Friday 16 October 2015

Properties of Fluids

Understanding the properties of fluids is essential to analyse their behavior in working conditions. In this post I have written the fluid properties namely mass density, specific weight, specific volume, specific gravity, viscosity, vapor pressure, compressibility and surface tension.

Mass Density
:
Mass Density (ρ ) is the property of a fluid is the mass per unit volume.
Specific Weight:
Specific Weight (w) of a fluid is the weight per unit volume.
Specific Volume:
Specific Volume (v) of a fluid is the volume of the fluid per unit mass.
Specific Gravity or Relative Density:
Specific Gravity (s) of a fluid is the ratio of the mass density of a fluid to the mass density of a standard fluid.
Viscosity:
Viscosity is property by virtue of which it offers resistance to the movement of one layer of fluid over the adjacent layer.
Vapor Pressure:
When a liquid is confined in a closed vessel, the ejected vapor molecules accumulated in the space between free liquid pressure and top of the vessel exert a partial pressure on the liquid surface. This pressure in liquid is known as vapor pressure.
Compressibility:
The normal compressive stress of any fluid element at rest is known as hydro static pressure which arises as a result of innumerable molecular collisions in the entire fluid. The degree of compressibility of a substance is characterized by bulk modulus of elasticity (K) .
Surface Tension:
Surface is a measure of fluid tendency to take a spherical shape, caused by mutual attraction of the liquid molecules.

Thursday 3 September 2015

DIFFERENCE BETWEEN AN ENGINEER AND ASCIENTIST FROM JAZIB SAEED KHAN'S BLOG

Engineer vs scientist - Difference between an engineer and a scientist - “I always wanted to be an engineer. And today as I see the magnificent artifacts that have been created by me I feel so lucky that I landed in a profession of my choice”. Well these are the words of a random person who happens to be an engineer by default. And believe  me if he were a scientist, he would have said the same thing. And so the hot point is: we really never know what makes an engineer different from a scientist.
Ironically people differentiate scientists from engineers by the level of personality they own. Engineers are often regarded as cool people with highly paid jobs who have nothing to do in the world but to make all the important decisions. Scientists on the other hand are regarded as the hapless
people who spend most of their lives with lab rats thinking over the issues that have nothing to do with a common man. This is the main reason most students want to take up engineering as the future
profession although they never realize that engineering is a multifaceted endeavor and they will have no exposure towards it until the end of the high school. And this happens to be the most important reason that most people never realize that a scientist and an engineer are indeed very different with different aims and indeed different priorities.
Differentiating engineering from science is a matter of how we look at the two professions in the real
world. An engineer’s priority should be to take up real world challenges and complete them in real time so that people may get the desired results and benefits. So in a way, we can regard that an engineer is closer to the common man than a scientist. It is just an opinion not a well established fact.
A scientist on the other hand should have the insight to perceive the upcoming future. And that is the fun part. A scientist mostly lives in a virtual world full of random and abstract thoughts that combine to form a solution. An engineer on the other hand lives in a real world that we all can see and feel. And that is the main reason that most of the work done by the scientist does not become inevitable at once.
Engineers often argue that their job is more innovative than the job of an average scientist who has to live with a bunch of lab rats all day long doing nothing. Well this perception is absolutely wrong. Inevitably engineering is a very versatile profession but innovation is just a part of it. A scientist on the other hand lives merely on innovation. Working in a virtual world is no easy task which requires loads of innovation in store.
Sometimes it is very difficult to draw a clear boundary between the two professions. Both have contributed immensely towards the development of this world. And it would be true to say that both are the wheels of the same car. Instead of discriminating them, we should try to bridge the two professions so that the world can really see what happens behind the scenes. I hope this article gives
you a good idea about difference between an engineer and a scientist.

Why engineers are not getting job offers?Ever thought why engineers are not getting joboffers?

There are so many reasons behind every rejection. It takes time to learn skills which are required for successful job interviews. Every day I get so many messages from confused fresh graduates and engineers from all over the world who ask me to help then in getting a job. From these messages, it is very clear that they are trying hard to reach out to fellow engineers and they are putting their best efforts in finding a job. But all these efforts are in WRONG direction. Here I would like to share some common reasons of interview rejection and why engineers are not getting job offers.

I have gone through all these phases of life. It hard to understand all these reasons at start of career but over time you start to realize your mistakes. Here i would share my personal experiences. Not preparing for interview I have seen many candidates who do not prepare for interviews. Interview is just like an exam, if you do not prepare, you will fail. Preparation for an interview includes looking for answers to common engineering interview questions, revising basic concepts of mechanical engineering courses, and dressing up properly for interview. General format of CV for all jobs I have seen many candidates who have a general format of CV to apply for all type of jobs. A good engineer will always make changes to his CV according to job description. Applying for too many posts in same organization/ company
Recently we are short listing engineering candidates for job interviews in my company. I have noticed so many candidates who applied for all positions with same CV. Is it logical applying for Manager Operations, Assistant manager operations, Assistant manager admin and Assistant operations at the same time? We rejected many candidates for this reason. Always be crystal clear about job position that you want to apply for.
Standing out too much Only add relevant information to your CVs and portfolio. Adding too much colors, extra information and irrelevant skills will not make any difference.
What is in it for me?
Always ask questions from your interviewer. Try to learn what is in this job for you? What opportunities of learning do you have? Is it suitable for you? This will help you decide whether the company is right for you.
Interview answers
Always prepare for potential common interview questions. Many engineers do not get job offers because they do not give satisfactory answers to some tricky questions. During all interviews, some
questions are of general nature while some questions are of technical nature.
Overconfidence
Overconfidence simply kills.
Lack of job information
Lack of job information and knowledge about possible job description gives a very bad impression about candidate. I once applied for a job position in a company dealing with water treatment plants. Reason for my rejection was that I could not explain how I would become a contributing member to this company because I was unaware of job description.
Non-confidence in employers’ recruitment procedure
Always show confidence in employers’ recruitment procedure. If they have called you for an interview, it means they are trying hard to do it on merit.
Always speak truth
Always speak truth. Those who are interviewing you, are experienced enough to catch false information through discussions.
Be yourself, be original
As simple as that: Be yourself, be original

Tuesday 1 September 2015

How to go for internship?

I do not want to spread any kind of negativity, but from my personal experience if your college is not a very reputed and recognized one then it can be almost impossible for you to get a decent paid internship. No matter what you are good in, no matter how hard you try its almost negligible chance for you to land at a nice internship. But still there are some ways which I will edit later OK lets start:

1.) If your college has a mechanism for internships then the companies will come for hiring interns as
they come for hiring employees, chose the company wisely according to you interest and learning opportunity not according to the stipend.
2.) If your college does not have a proper mechanism then you can ask your TPO to give you some contacts of local companies and a recommendation letter from your TPO and department professor would be helpful.
3.) If the above 2 are not applicable then its a long way to go...bear with me:
You need to actively look for internship opportunities on internet(almost 5-6 times in a day) and I would recommend you to start in the month of December.
Some of the websites which you can refer are:
a.) Internship | Summer Training | Paid Internships | Summer Internship 2014 subscribe on internshala and you will get the recent internship directly on your mail id.
b.) Internships and Internship Jobs in India
c.) Look for research internships on the websites of  IITs and IISC, some of the programs are:
SURGE : IIT Kanpur; IITJ-Indian Institute of Technology Jodhpur : UGRI,; IIT Jodhpur and almost every IIT has such program. Moreover if you are interested in research in a particular topic then you may contact the professors from elite institutions directly by going through their profile from the Institute website. But for this you need to make a strong case in front of him backing your interest and eligibility.
Likewise there are many more similar platforms on which you can search for internships.
4.) You may contact your college alumni to seek their help.
5.) Visit the career page of the websites of various companies, many companies directly call for applications or you may contact their HR
6.) Still if you can not land at an awesome internship then you can go for Industrial training but do not waste all of your vacation time unless you are preparing for some competitive exam. Now we come to the application, Cover letter and mail sending:
1.) Now that you have searched an internship and you are going to apply for it, keep these things in
mind:
a.) Your resume highlights the similar work done by you in college for which you are applying
b.) Make a standard resume, you can get help from many references on internet like Resume writing ppt presentation and similar. Also search for resume of IITB students online.
c.) Write a professional mail mentioning your interest and relevancy, avoid including jargon and irrelevant details
d.) Do not follow up too much
e.) It the cover letter is required then seek for help from your seniors on how to write it or look at the
internet
If you are entering your sophomore or pre-final year then it is highly recommended to develop some professional skills that may vary from branch to branch. It will not only help you in getting a decent internship but will help you in job interviews as well.
Stop wasting time and indulge in co-curricular, extra- curricular activities in college or outside the college. Be part of 1 or 2 clubs that interests you, it shows that you have organisational qualities and team spirit. Highlight your work on your resume.

10 Sites That Every Engineer Should Know About

Here's another post inspired by an office discussion. We were discussing our favourite engineering based websites and realised the results would make a great blog post. So after a rummage through our bookmarks and a little further debate we've come up with our top ten sites. We tried to keep the list balanced so you'll find a few resource sites, a little bit of fun and one or two sites that aren't purely engineering sites, but contain valuable knowledge for engineers. Do you have a favourite site that we haven't included? Why not add a comment below and give your favourites a plug.
1. Engineering.com
A wealth of engineering related news, videos, resources and jobs. Visit... Engineering.com
2. Engineering Formulas
A website packed full of formula for Fluid Mechanics, Failure Criteria, Finance and loads of things that don't begin with F too. A great site for lovers of Greek letters and other squiggles. Other parts of the site have information on materials, units, design and maths. Visit... eFunda: Engineering Formulas
3. The Engineering Toolbox
A great site, well structured into various engineering categories that lets you drill down to find the information you need. The flow of the site is a little spoiled by too many Google Ads links, but that is just a minor irritation.
Visit... The Engineering Toolbox
4. LinkedIn
Not strictly an engineering resource, but LinkedIn is a great place to network with fellow engineers (it's a bit like Facebook for grown-ups) and has some really useful special interest groups for sharing
knowledge, meeting like-minded professionals and exchanging job opportunities.
Visit... LinkedIn
5. GlobalSpec
Calling itself "The Engineering Search Engine", GlobalSpec is packed full of engineering products and suppliers. Has some great email newsletters and product alert emails. You can even find Prosig on GlobalSpec .
Visit... GlobalSpec
6. How Stuff Works
Whenever we need bit of extra background information for an office discussion this website is one of our first ports of call. Packed full of straightforward explanations
Visit... How Stuff Works
7. Eng-Tips Forums
A fine collection of discussion forums, blogs, whitepapers and more. Covers a wide range of engineering fields.
Visit... Eng-Tips Forum
8. Wikipedia
Again, not strictly an engineering site, but Wikipedia can't be ignored when seeking information. Much has been made of the possible innaccuracies of Wikipedia's articles, but genarally the scientific and engineering pages are well maintained.
Visit... Wikipedia
9. Discover Engineering
A fantastic site for students or anyone new to engineering. Or just about anyone who enjoys quirky science projects and engineering themed games and activities. We all need a little light relief, right?
Visit... Discover Engineering
10. Fun-Engineering
Another bit of fun to finish with. Fun-Engineering (maintained by Prof. Jim McGovern of the Department of Mechanical Engineering at the Dublin Institute of Technology) is a great little site, full of engineering gems. To my mind it is sites like this that make the WWW what it is.
Visit... Engineering-Fun

Saturday 29 August 2015

What should a Mechanical Engineer must know!

Well being a mechanical engineer student i personally think that basic concept is the most important thing every Mechanical Engineer should know and to remember those concept you must wrote them down on a paper and stick it on your wall so you can keep checking and remembering those basic concepts allow me to elaborate in case of thermodynamic ( you must know about zero,first,second law of thermodynamic and different formulas of enthalpy, understand of tables,of pressure ,temperature and curves etc) keep their short notes and use you gain knowledge on every holiday to solve real world problems must know ideal process cycles and its types and try to grap concepts of experiment and stick its notes close to your eyes
Fluid mechanics
For this you must know how to select a pump for certain requirement like you must know what is the head of pump pressure of pump and flow rate also you must know how to estimate pipe pressure and friction depending on is length ,diameter, and angle on which it is and most importantly pressure drop on different kinds of bends(must know about type of angle use in pipe and type of bends) how to find
center of (inertia,resultant force,resultant pressure) of shape on which fluid is carried this thing help in building (dams ,reservoirs for different fluids) and plus you should also know about CG (center of
gravitation) this help in building ships and floating stuff ,you must know about effect on pressure if you go down sea level inside fluid or go on high hills must know about how to use instrument and basic ideal gas laws and few application try to practice these concept every holiday
Mechanics of Material(MOM)
For MOM try to practice to remember bending moment, shear stress,torsional stresses, normal stresses,bending moment both (horizontally,vertically) moment of inertia of different shapes and objects must keep a chart on your wall to know difference of ductile and brittle cure mechanical properties (young modulus,yield strength of basic mostly use materials like aluminum,steel,brass,copper,iron etc) ,mohr circle etc and create a structure like cycle or other thing
using this concept or try to help those student who are making structure in there final year project
Design OF Machine Element(DOM)
keep remember basic things like different between rivet,screw,bolt,stud, and most most most important where to use them in come places you only use rivet you must know reason keep there  notes on your wall ,must type of keys and what material should we use same or different and flange design and other these thing try to solve there real problem by asking real engineer if you can or create your on and build product and test it or help final year student to build project
TOM (THEORY OF MACHINES)
Must know how to analysis mechanism, how to create mechanics mostly mechanism are made of 4 bar mechanism know ho to calculate velocity of component fore and all other stuff some mechanism are basic like train,umbrella,car roof mechanism and some are use in games like (wipe out try to look at these mechanism and think how it would have been made and create on paper find its velocity force ) and also you must keep notes of pulley and belts driver and follower,must know how to find best for your desired pulley ,types and uses and tables and about gears also type of gears uses how to
change direction method to find gear teeth

Heat and mass transfer (HMT)
Must know difference between conduction,convention,radiation and there formulas, and enthalpy,coefficient of convection,conduction etc which fluid ha what property and what is its use heat storage capacity and rate of heat transfer both in pip and solid wall must know how to design and
how to play with flow rate of pre -design pipe ,heat exchange and special cases of boiler,condenser effectiveness and efficiency trick to solve and other things like that keep remember must know which pump to use which design heat exchanger and effect of corrosion,environment speed etc keep their notes close to your eyes
IC Engine
Different types of engine parts of engine components which component has what effect what happen if leaking of on thing happen and real life cases of it how many parts to crankshaft mover what other components are connected with cam shaft and how camshaft control water pump,oil pump,radiator fan,vacuum section, carburetor parts, different condition of throttle and mixing ration change while,staring,cursing, cooing system different types and effect of environment case of different situations lubrication how and thrown which places oil move to lubricate and problem of flow of lubricate and its real life case try to communicate with your teacher math stuff must know all math formula and there use try to bring those formulas to real life pick one formula and work on it every holiday with real life situation

'A GOOD TEACHER IS A GIFT WHO CAN TELL YOU REAL LIFE PROBLEMS AND SITUATION'
Keep you interaction with your teacher who taught you and keep asking different question any doubt
and try to find those teachers who have experience in that field whose wisely because in your life only few courses you will be using it depend on you job type so focus on your dream work you want to do and for what you picked MECHANICAL ENGINEERING people die and new people come don't worry about job only do what you like its your life you life once.

Preparation for GATE 2016

Four things are vital for GATE preparation.
1. Theory
2. Problem practice
3.Revision
4. Test
Let me take each point one by one.
1. Theory:
First of all, go through the syllabus.
Page on iitk.ac.in
Either go through made easy notes which are easily available at any Xerox shop in Delhi,
OR
Make your own note from NPTEL.
NPTEL PHASE 2 - Courses
I will recommend you the second option (making notes from nptel) as it will build your concepts in
a much better way.
2. Problem Practice.
I will highly recommend you the following books.

GATE - Mechanical & PI Engineering 2016 : 28 Years
GATE Solved Papers with thorough Explanations (English) 1st Edition
GATE Practice Book 2016: Mechanical Engineering Book
IES 2015 Mechanical Engineering Topicwise Objective Solved Paper II
IES 2015 Mechanical Engg Topicwise Objective Solved Paper-I
Solving the first two is must. After solving these two if you still have enough time, go through the last two books also. Also, if possible, buy made easy notes and go through the problems in it. There are a few very good questions in it.
3. Revision.
This is one of the most important thing for GATE because irrespective of your preparation, if you don't have proper revision strategy, you are going to fail for sure. I have seen many students working really hard throughout the year and ending up with a very low rank because of lack of revision.
So, here is the key.
Make short notes. Go through the important formulas at least 10 times.
In short notes include all formulas and key points. This book is going to help you a lot in making short notes. A Handbook for Mechanical Engineering Book
4. Test.
Make your strategy in such a way that the last 45 days are dedicated only for giving tests. You can join any one or preferably both of these test series.
a) MADE EASY TEST SERIES
b) ACE ACADEMY TEST SERIES
Try to give each and every test of these two test series.
Giving test is very important because it is going to increase your problem solving speed and accuracy.
If you want to avoid making silly mistakes in the exam, give as many test as possible.
BEST OF LUCK FOR GATE'16

Friday 28 August 2015

HR Round: tentative Questions:

1. Tell me something about yourself.
2. What do you know about Co?
3. Explain me any concept considering me as a layman.
4. Will you be able to work if posted in a place like Andaman?
5. What are your hobbies?
6. Tell me an interesting experience of your life.
7. Will you get married soon?
8. What will you do if you are told to work on something you don't know or like?
9. Tell something about yourself that is not in the resume.
10. What is your area of interest?
11. Why do you want to join this industry?
12. Would you work anywhere in the country?
13. What if we don’t select you today?
14. Tell me about your family, weakness and strength.
15. What is commitment? Do you have a girlfriend?
16. Do you consult your parents?
17. Will you stay away from your parents?
18. Will you do arranged or love marriage?
19. You are living in 21st century, you should take your own decisions. Then why consult parents?
20. Why should we hire you?
21. Tell me a few qualities that you have.
22. How much will you sell your project for?
23. What is your future plan?
24. How you being emotional help us?
25. Are you ready to relocate?
26. Will you be able to adjust yourself with people in Chennai?
27. Do you wish to go for higher studies?
28. Are you innovative enough?
29. What is your best achievement?
30. What has been your toughest decision till date?
31. Tell us about your journey.
32. Given a situation how would you resolve a conflict.
33. What would you do if your seniors are not noticing your work?
34. What has been your best experience till date?
35. Rate yourself on a scale of 1-5.
36. Are you aware about the Co eligibility, background check?
37. You have high percentage in SSC and HSC but low in engineering. Why?
38. What is your ambition in life?
39. What do you do in your free time?
40. Do you want to be in Co even after 3 years?
41. Why do you want to be in Co?
42. Why a job?
43. How happy are you with your parents decision?
44. What is the longest you have stayed away from your parents?
45. What are your expectations from TCS?
46. Where do you see yourself in the next 5 years?
47. Tell me about your teamwork.
48. What is your chance of getting selected?
49. Why should I select you compared to others?
50. Describe one instance when you have succeeded.
51. You are a project manager. How will you ensure that your project is completed on time?
52. What are the three keywords according to you for success?
53. Who is your role model?
54. In how many ways can you contribute to the society?
55. What is the meaning of your name? who do you have faith in?
56. Describe yourself in one line and in one word.
57. Do you think advantage of exemption from aptitude given to toppers is good or bad.
58. Which department would you like to go in?
59. If 20,000INR are given how will you manage it in a month? And how much will you save from that?
60. If not this Co where are you planning to go?
61. Tell me one instance when you worked as a team leader.
63. If you lead a project and the team members aren’t happy with you as the leader what will you
do?
64. How much time do you spend on the net? Tell me the most recent news that you have come
across.
65. What do you think of life?
66. Difference between creativity and innovation.
67. Difference between theorem and axiom.
68. Explain your interview experience in Marathi.
69. Where do you see yourself in the coming years?
70. What are your interests?
71. Tell me the story of any movie you saw recently.
72. Are you tired or nervous?
73. Are you sure you’ll take up the job and not go for further studies?
74. Why do you want to join an IT company? Since your percentage is so good? Will you work on
domains like database management, oracle, etc?
75. Difference between agile and waterfall.
76. How was your day?
77. How long did you wait? Was it worth the wait?
78. How do you manage to resolve conflicts within your siblings?
79. What books do you read?
80. How will you manage to live with females of other states?
81. If you are a team leader what 3 things do you think are most important ?
82. How do you make someone feel special?

Important Questions asked in Mechanical Engineering Interview!

I'm sharing this question list to fellow mechanical engineers that I made to prepare for an interview. It
contains two sections viz. technical questions followed by HR questions.
1. Technical questions:
Type of technical questions asked will be definition type and that too from basic. Your favorite subjects will be asked first and then they start questioning what they want you to answer. Some of the
questions are...

1. Why we do not use same technology to start both SI/CI engine?
2. Which one is more efficient? A four stroke engine or a two stroke and why?
3. 4 Stroke engine is more efficient primarily Because of the presence of valves which precisely control the flow of charge into the chamber and exit the exhaust gases with proper timing which is hard to achieve by ports in a 2 stroke engine.
4. Why there is no differential in a train. What happens when a train takes a turn?
5. A cantilever beam is loaded a point on its ends what will be the effect in shear force?
6. Why vehicle does not move when its gear is applied though parked in slope area?
7. What is shear force in fluid particle?
8. How gear ratio helps in power variation?
9. What is the angle of twist in drill?
10. What is the difference between impact force and sudden force?
11. How to calculate the turbine efficiency?
12. Why centrifugal pump casing is called involutes casing?
13. What will happen if reciprocating compressor run in exactly opposite direction?
14. What is the effect of clearance volume in performance of air- compressor?
15. What is the advantages and disadvantages of critical speed of turbine?
16. What will happen if oil is mixed with boiler feed water?
17. What is difference between fan and blowers?
18. What are the protections required to protect turbine?
19. what is critical temperature?
20. Air is a bad conductor of heat. Why it becomes hot in summer?
21. How many stages in compressor in there in gas turbine?
22. Which is more efficient? A rear engine Volvo Bus or a Front engine Volvo Bus? (Engine Capacity is same for both) why?
23. What is difference between stress and pressure?
24. What is Boiler HP?
25. What is Auto Dosing?
26. What happens when too much oil is injected in the working cylinder?
27. How many manholes should be there on boiler? Why?
28. What is used to check the amount & quality of fuel in two stroke IC engine?
29. Work done in throttling process is given by which formula?
30. Function of the strainer in IC engine?
31. What is the difference between the air pre-heater & air blower?
32. Why the compression ratio of the diesel engine should be high?
33. A vertical plate and a horizontal plate are suspended in an open room. Both are heated to the
same temperature. Which one will cool first? Why?
34. What is the color of flame if the boiler is running?
35. Which is the best lubricant-air, oil or water?
36. Tell the octane number in Indian petrol?
37. Difference between enthalpy & entropy?
38. What is the difference between safety valve and relief valve?
39. Explain cooling and its types?
40. What is the working principal of air compressor?
41. What is cryogenics and what are its fundamentals?
42. What is the difference between a shaper machine and a planner machine?
43. Why stress relieving of stainless steel is not roffered?
44. What are the advantages of PID controllers compared with those of a PLC?
45. Which two continents are mirror images of each other?
46. Where half nut is used?
47. What is the need for drafting?
48. Turbo charger driven by.............? and what its speed
49. Why...? Turbo charger used in DG....?
50. The stage below saturation is called?
51. Why is a condenser used in a Rankin cycle?
52. What is servo motor?
53. Can we use light duty vehicle axle into the heavy duty machinery axle? If no then why?
54. Stress strain diagram for fluid?
55. Where manning formula used?
56. What is level of documentations for a ISO 9001 certified company?
57. What is back plate in centrifugal pumps and its purpose?
58. Why tyres are manufactured in black colour?
59. Whether ductile material can fail in brittle manner? When?
60. On what property u can distinguish material as brittle or ductile?
61. Name fuels used in nuclear power plant?
62. On what thermodynamic cycle nuclear power plant works?
63. How can you increase the efficiency of power plant without changing in effort?
64. What is purpose of governor in Diesel engine?
65. Why petrol engines have more power than diesel engines of same capacity?
66. What is the difference between Torque and Power ( layman Idea)?
67. What will be the induced stress in the bar?
68. What is the Difference between Rated Speed and Economic Speed?
69. How to convert from HP to BHP or CC to Bhp please explain????????
70. How the material no. 2062 will mild steel of density 7.85? What are the other codes?
71. Why petrol engine gives more power than diesel engine even though diesel engine has high
compression ratio?
72. What is mean by Resistance welding?
73. Compare Brayton and Otto cycle.
74. Why we have to know the specific frequency of any equipment? does anybody know about specific frequency ?
75. What is pulverization?
76. What is the function of an isolator?
77. Why the back wheel of tractor is bigger than front wheel?
78. Flow will increase or decrease or remain same?
79. Why Mechanical seal used in Pumps?
80. The ratio of Emissive to absorption power of heat by a body is equal to heat emitted by a perfect
black body. Who said the statement
81. What is colour of flame if the of Halide Torch detects a refrigerant leakage?
82. How can we remove paint from (painted over) plastic or nylon objects with out damaging the
object?
83. How to calculate or arrive the capacity of a mechanical press?
84. The property of a metal that is determined by the indentation on a metal surface
85. The amount of thickness of the metal sheet that can be welded by ultrasonic welding is?
86. The amount of carbon present in Cast Iron?
87. Numeric control is used for?
88. The amount of moisture that is to be present in wood to be called dry wood is?
89. The pattern material used in Investment casting Process is?
90. What is the use of offset follower in cam? Why and where we have to use this type of follower?
91. What is the use of offset follower in cam? Why and where we have to use this type of follower?
92. State the difference between Forging & Fabrication?
93. What is flange rating?
94. What amount of heat energy loss in ESP?
95. What happen when diesel is injected in petrol engine?
96. What do you mean by property of system?
97. Why joule-Brayton cycle is not suitable for a reciprocating engine.
98. How does “turbulence” differ from swirl?
99. Is octane number beyond 100 is possible?
100. Explain the effect of fuel structure on knocking.
101. Discuss the advantages and disadvantages of LPG as a fuel in S.I. Engine?
102. What is the impact of using throttling device instead of expander in vapour compression cycle?
103. What is moisture choking? Which refrigerants are more prone to it?
104. What is Montreal protocol and why CFCs are being phased out?
105. Why reverse Joule Brayton is used in aircraft refrigeration system?
106. Explain how solar-energy can used in refrigeration system?
107. Is wet bulb temperature a thermodynamic property?
108. What is the utility of comfort chart?
109. How would you decide whether a reciprocating compressor or centrifugal compression is to be
used in a refrigerating system?
110. Why smoking is not allowed in air conditioned enclosure?
111. Why desert coolers become ineffective in raining season?
112. Why package units are being preferred over central air conditioning system?
113. What is MAPI.
114. What is capital budgetary?
115. What is group technology layout?
116. What is leveling & smoothing in production technology?
117. What is deference between method study & work measurement?
118. What you know about drilling?
119. How oil is produced? What is the size of well?
120. Pumps used in drilling procedure and why? Why not centrifugal pump? What if we want high
head and high discharge?
121. Difference between Pipeline and Piping ?
122. Use of CNG, LNG, LPG etc.
Additional questions subject wise:

Fluid Mechanics and Fluid Machinery
What is the difference between impulse & reaction turbine.
Explain unit speed, unit discharge unit power & specific speed.
Explain NPSH, in which parameter it depends on.
What is jet ratio?
What is Deriaz turbine?
Which turbine is good for tidal power plant?
What is Navier-stroke equation.
What are the significance of
Mach number
Weber number
Material Science
What is quazi-crystal?
What do you understand by a free cutting steel?
What elements are usually added to make a steel free cutting, & how they make the steel free cutting?
Explain various method of hardening of steel?
What do you understand by the term “Arrest point” in connecting with heat treatment of plain carbon steel?
What influence does grain size have on the mechanical properties of metals.
Describe the difference between brittle and ductile fracture.
What is the difference between natural & artificial aging?
Thermodynamics
What is availability function for a closed system?
If it is possible that entropy of a system can decrease during a given process?
What is dead state in thermodynamics?
What is exergy?
What happens to triple point line when projected to P-T plane?
What is compressibility factor and what is its value for Vander walls gases.
What are initial conditions for formation of shock waves?
What do you understand by choking in nozzle flows?
Is it possible that pressure and velocity decreases simultaneously/
Distinguish between “Available energy” & Availability?
What is pure substances.
What is critical point? What is the value of critical temperature, pressure & volume of water?
What is sublimation curve, fusion curve & vaporization curve?
What is Rayleigh Line & Fanno Line?
What is normal shocks & when its occurs?
What is High Grade Energy & Low Grade Energy?
Heat & Mass Transfer
What is Newton’s Law of cooling.
What is Recuperator & Regenerators?
Whether fin can actually reduce heat transfer? is it possible? When?
What is difference between Biot no. & Nusselt no?
Which one is greater, thermal boundary layer or hydrodynamic boundary layer?
What is film temperature in forced convection flow?
What is fully developed region and where it is applicable?
What is the critical radius of insulation, explain clearly in terms of thermal resistance and heat
transfer rate?
At what case do you recommend Fin?
What is the difference between free convection & forced convection in what parameter forced &
free convection depend.
Internal Combustion Engine What is the use of Carburetor in SI Engine, There is trend towards increases of injection system in
Automobiles, Explain.
Why Supercharging is not popular with SI Engines?
What is performance number.
Explain Knocking in SI Engine & Mention, the factor that tend to reduce Knocking?
Explain the difference between Knocking in SI Engine & CI Engine?
How does “Turbulence” differ from “Swirl”?
Name some Antiknock additive and explain the Mechanism by which they reduce the knock?
Power Plant engineering
What is slip ratio in thermal power plant?
In Pendant super heater whether parallel flow or counter flow heat exchange between steam and flue gases.
What happens to mass flow in case of supersaturated flow?
Why clearance are provided in reciprocating compressor?
Explain turbojet & Rocket Engine.
What’s the advantage of compounding of steam turbine?
What’s are boiler mounting & accessory.
Draw the sketch of pulse jet engine. What are its main advantage & disadvantage?
Explain working principal of scram jet engine,
what is advantage over the ramjet?
What are the advantage of nuclear power plants over thermal power plants.
What is fast breeder reactor?
What is circulation ratio and what is its range in power plant?
One 2-row Curtis turbine is equivalent to how many reaction turbines for same value of blade velocity and angle of nozzle?
What are thermal neutrons?
What is breeding ratio?
What is the application of jet and rocket technology? Which is used in missiles?
Strength of Materials
What do you mean by equal strength in a beam?
What is difference between pure shear and simple (normal) shear?
Is it possible that decrease in area gives a decrease in stress?
Whether shear stresses are always parallel to shear forces?
By which experiment, you find it toughness of material.
Distinguish between direct stress & bending stress.
What do you mean by Torsional rigidity & lateral rigidity?
Define “slenderness ratio”. How it is used in long and short column?
Machine Design
What are rolling contact bearing?
What are the anti friction bearings?
What is stress concentration factor?
What is the bolt of uniform strength?
What is the difference Static Load carrying
capacity & Dynamic Load carrying capacity?
Why we are not using the unit joule for torque instead of N-m.
What is Low cycle fatigue failure and High cycle fatigue failure? What are considerations of these while designing a machine?
What is mechanical advantage?
How trains take turns though there is no differential gear?
Do you know epicyclical gear box? What is the practical application of epicyclical gear box?
What is tooth profile? Which one is better?
Theory of Machines
What is Keneddy theorem?
Do we need a screw with efficiency less than 50%?
What is backlash?
What is damping ratio?
Define Resonance.
Define critical speed or whirling speed or
whipping speed.
What is machine? Giving example, Differentiate
between a machine & structure.
What is Mechanical advantage.

Refrigeration and Air-conditioning
What is utility of comfort chart?
hat is wet compression?
To maximize COP what should be the condition of vapour at suction to compression?
What is the range of NBP (normal boiling point) in case of most refrigerants?
Why COP of CO2 gas is less and still why it is used in transport refrigeration?
What are the most crucial parts in reciprocating compressors?
How compressors are selected based on type of refrigerant?
What is correlation between wet bulb
temperatures an adiabatic saturation temperature?
Why isothermal compressor is Desirable?
What is desirable property of ideal refrigerant?
Define effective temperature & what is the optimum design condition for comfort for summer A/C?
Production Engineering
Why arc is slowly extinguished in case of arc welding?
Which inert gas is commonly used for thin work piece and which inert gas for thick work piece?
What is friction welding?
What is difference between brazing & braze welding?
Why hole basis system is adopted in manufacturing?
What is 3- 2-1 principle?
Where diamond pin locator is used?
How presses are rated?
What is spring back?
What is difference between fillet and corner radius?
What are overhead costs?
Why depreciation is to be taken into account in industrial management?
Why breakeven point is important in any industry?
What is sine bar?
What is marginal cost and marginal revenue?
What is shear and where it is provided in case of punching and blanking?
What is angle of bite?
What is extrusion ratio?
What is gutter and where it is used?
Which process is used for making nuclear reactor fuel rods?
What is difference between Amorphous and crystalline solids?
What are the various method of inspection of
casting for internal & external defects?
Why are allowances provided for in the
production of patterns? What do they depend on?
What is the deference between soldering & brazing?
What is meant by solid-state welding explain.
What is cold welding?
Describe the principal behind resistance welding processes.
What function should a lubricant perform in manufacturing process?
Explain the difference between punching & blanking.
Explain the difference between discontinuous chips and segment chips.
Explain the different type of tool wear.
What is difference between oblique & orthogonal cutting.
What are the main difference between jig and fixture?
What is AOQ
What is LTPD
What is Producer risk
What is Consumer’s risk
What is JIT approaches?
What is group technology? What are its main advantages?
Define the term “production & productivity.
What is the significance of ISO 9000 series & 1400 series.
What is artificial intelligence?
Which welding process does not required any filler material?
What is tack weld?
Which process used for cutting thicker plates?
Where drooping characteristics of power source is required in arc welding?
2. HR questions:
1. Tell me about yourself?
2. What is your hometown famous for?
3. Tell about your achievements in life.
4. Your strengths and weakness
5. Are you a team player?
6. Tell me about your ability to work under pressure.
7. How would you know you will be successful on this job?
8. Describe your management style.
9. Global warming
10. Chief justice of India
11. Vice President of India
12. CEO of Apple, when did he die?
13. Gas scenario
14. RBI policy
15. Corporate Governance
16. Corporate Laws
17. Cast system is boon or bane ?
18. What’s the difference in the modus operandi of Amir Khan’s “Satyameva jayate” and Anna Hazares movement?
19. What will u do on your part to remove corruption? If you travel in a train without confirmed ticket will u bribe the TT for a seat?
20. What do u mean by optimistic. Is it always good to be optimistic or it helps sometimes to be pessimist?
21. What is difference between confidence and over confidence?
22. What is the difference between hard work and smart work?
23. What are your goals?
24. What motivates you to do a good job?
25. What makes you angry?
26. Give an example of your creativity
27. Describe ideal company, job, and location?
28. What are your hobbies?
29. Inspiration in your life and why?
30. What was the toughest decision you ever had to make?
31. Define success? and how do you measure up to your definition
32. About present job (if employed)
33. Why did you resign from your previous job?
34. Why have you been unemployed so long?
35. What was the toughest challenge you have ever faced?
36. What would you say to your boss if he is crazy about an idea, but you think it stinks?
37. Why should I hire you?
38. Explain how you would be an asset to this organisation.
39. If we give you a job will you leave IIT B or your organisation?
40. What changes would you make if you came on board?

Wednesday 19 August 2015

GATE 2016 Mechanical Engineering Syllabus

Section 1: Engineering Mathematics
Linear Algebra: Matrix algebra, systems of linear equations, eigenvalues and eigenvectors.
Calculus: Functions of single variable, limit, continuity and differentiability, mean value theorems, indeterminate forms; evaluation of definite and improper integrals; double and triple integrals; partial derivatives, total derivative, Taylor series (in one and two variables), maxima and minima, Fourier series; gradient, divergence and curl, vector identities, directional derivatives, line, surface and volume integrals, applications of Gauss, Stokes and Green’s theorems.
Differential equations: First order equations (linear and nonlinear); higher order linear differential equations with constant coefficients; Euler-Cauchy equation; initial and boundary value problems; Laplace transforms; solutions of heat, wave and Laplace's equations.
Complex variables: Analytic functions; Cauchy-Riemann equations; Cauchy’s integral theorem and integral formula; Taylor and Laurent series.
Probability and Statistics: Definitions of probability, sampling theorems, conditional probability; mean, median, mode and standard deviation; random variables, binomial, Poisson and normal distributions.
Numerical Methods: Numerical solutions of linear and non-linear algebraic equations; integration by trapezoidal and Simpson’s rules; single and multi-step methods for differential equations.
Section 2: Applied Mechanics and Design
Engineering Mechanics: Free-body diagrams and equilibrium; trusses and frames; virtual work; kinematics and dynamics of particles and of rigid bodies in plane motion; impulse and momentum (linear and angular) and energy formulations, collisions.
Mechanics of Materials: Stress and strain, elastic constants, Poisson's ratio; Mohr’s circle for plane stress and plane strain; thin cylinders; shear force and bending moment diagrams; bending and shear stresses; deflection of beams; torsion of circular shafts; Euler’s theory of columns; energy methods; thermal stresses; strain gauges and rosettes; testing of materials with universal testing machine; testing of hardness and impact strength.
Theory of Machines: Displacement, velocity and acceleration analysis of plane mechanisms; dynamic analysis of linkages; cams; gears and gear trains; flywheels and governors; balancing of reciprocating and rotating masses; gyroscope.
Vibrations: Free and forced vibration of single degree of freedom systems, effect of damping; vibration isolation; resonance; critical speeds of shafts.
Machine Design: Design for static and dynamic loading; failure theories; fatigue strength and the S-N diagram; principles of the design of machine elements such as bolted, riveted and welded joints; shafts, gears, rolling and sliding contact bearings, brakes and clutches, springs.
Section 3: Fluid Mechanics and Thermal Sciences
Fluid Mechanics: Fluid properties; fluid statics, manometry, buoyancy, forces on submerged bodies, stability of floating bodies; control-volume analysis of mass, momentum and energy; fluid acceleration; differential equations of continuity and momentum; Bernoulli’s equation; dimensional analysis; viscous flow of incompressible fluids, boundary layer, elementary turbulent flow, flow through pipes, head losses in pipes, bends and fittings.
Heat-Transfer: Modes of heat transfer; one dimensional heat conduction, resistance concept and electrical analogy, heat transfer through fins; unsteady heat conduction, lumped parameter system, Heisler's charts; thermal boundary layer, dimensionless parameters in free and forced convective heat transfer, heat transfer correlations for flow over flat plates and through pipes, effect of turbulence; heat exchanger performance, LMTD and NTU methods; radiative heat transfer, Stefan-Boltzmann law, Wien's displacement law, black and grey surfaces, view factors, radiation network analysis.
Thermodynamics: Thermodynamic systems and processes; properties of pure substances, behaviour of ideal and real gases; zeroth and first laws of thermodynamics, calculation of work and heat in various processes; second law of thermodynamics; thermodynamic property charts and tables, availability and irreversibility; thermodynamic relations.
Applications: Power Engineering: Air and gas compressors; vapour and gas power cycles, concepts of regeneration and reheat. I.C. Engines: Air-standard Otto, Diesel and dual cycles. Refrigeration and air-conditioning: Vapour and gas refrigeration and heat pump cycles; properties of moist air, psychrometric chart, basic psychrometric processes. Turbomachinery: Impulse and reaction principles, velocity diagrams, Pelton-wheel, Francis and Kaplan turbines.
Section 4: Materials, Manufacturing and Industrial Engineering
Engineering Materials: Structure and properties of engineering materials, phase diagrams, heat treatment, stress-strain diagrams for engineering materials.
Casting, Forming and Joining Processes: Different types of castings, design of patterns, moulds and cores; solidification and cooling; riser and gating design. Plastic deformation and yield criteria; fundamentals of hot and cold working processes; load estimation for bulk (forging, rolling, extrusion, drawing) and sheet (shearing, deep drawing, bending) metal forming processes; principles of powder metallurgy. Principles of welding, brazing, soldering and adhesive bonding.
Machining and Machine Tool Operations: Mechanics of machining; basic machine tools; single and multi-point cutting tools, tool geometry and materials, tool life and wear; economics of machining; principles of non-traditional machining processes; principles of work holding, design of jigs and fixtures.
Metrology and Inspection: Limits, fits and tolerances; linear and angular measurements; comparators; gauge design; interferometry; form and finish measurement; alignment and testing methods; tolerance analysis in manufacturing and assembly.
Computer Integrated Manufacturing: Basic concepts of CAD/CAM and their integration tools.
Production Planning and Control: Forecasting models, aggregate production planning, scheduling, materials requirement planning.
Inventory Control: Deterministic models; safety stock inventory control systems.
Operations Research: Linear programming, simplex method, transportation, assignment, network flow models, simple queuing models, PERT and CPM.

What do Mechanical Engineers do?

Scientists dream about doing great things. Engineers do them.”

-James A. Michener
Engineers solve complex problems for society. Mechanical engineers create and build mechanical devices. They apply the fundamentals of science and math to create practical, useful solutions that the rest of us can use.
The diverse mechanical engineering field can be divided in a variety of ways in terms of job functions. Some of the most common functions relate to these areas of technology, but not all do. Among these fields are:
  • Product Design -- developing products ranging from biomedical devices to gasoline-powered engines. A mechanical engineer designs anything that uses mechanical motion.
  • Research and Development -- discovering new solutions to human needs or improving older methods.
  • Manufacturing -- developing the machines that process materials into products. Designing and building machines and systems of machines that improve operating efficiency is of prime importance.
  • Systems management -- overseeing operations of a large system, such as a power plant, as well as supervising the people who work there.
  • Energy -- planning how energy is generated, stored, and moved. Industries that produce and deliver electrical power, such as natural gas, oil and alternative energy, employ mechanical engineers to develop more fuel-efficient cars, motors, and appliances.
In most of these fields, the mechanical engineer is concerned with heat utilization or machine design--in other words, harnessing or creating energy. Heat utilization techniques are applied in boilers, air conditioners, and refrigeration units. Machine design is more focused on hardware, including automobile engines, computers, and washing machines.

Problems faced in your final year project and ways to avoid them

Your academic project would be a demanding, but an exciting learning experience. However, it is not without problems which, if not identified and addressed, could seriously effect the final result and ultimately reduce your marks. Here we mentioned some of these problems and how to avoid them
The “Overachiever” Problem:
A common problem is selecting a topic that is far too ambitious for the allotted time.   Remember that you have only a few weeks to finish the design, development and testing of your project. Be careful not to select a topic that is unrealistically large.  This can lead to frustration as well as errors caused by “cutting corners” and hurrying through the implementation.  Discuss with your supervisor the scale of what you are planning.  If he or she thinks it may be too large, consider implementing the project in stages, each complete in itself.  When stage I is working move on to stage II.  If you do not finish stage II, however, you still have a functioning system.
The “Do It Tomorrow” Problem:
The project weeks alloted for completion sounds like a long time, but it goes by quickly.  You need an implementation schedule that allocates reasonable amounts of work throughout the entire semester. Then you must stick to that schedule.  Don’t be tempted to postpone work on the project because your due date seems so far off.  All that happens is that during the final few weeks you rush madly to get something working, and project implemented in a rush rarely works correctly!
The “Sleeping Member” Problem:
In the ideal world, all team members have equal ability, equal interest in the problem, and work equally hard.  In the real world that may not happen.  You may have one (or more) team members who do not carry their share of the workload, not because of a lack of ability, but rather lack of interest or motivation.  This is a serious problem because, although part of your marks is based on each individual’s effort, another part is based on successfully finishing the project.  A non-contributing team member can slow down or prevent completion of the work.  If you have a teammate who is not doing his or her share of the work, talk to them and stress the importance of everyone doing their job.  If this does not solve the problem then talk to your supervisor.  Don’t let the failure of others prevent you from completing the work and receiving good marks.
The “Poop Out At The End” Problem:
You have worked hard for many weeks to complete the project. You have spent many late nights and chased down hundreds of bugs, but it is now working, so are you done?  Absolutely not!  The project evaluation is not based only on the programs you develop but also on your written reports and oral presentations.  Even though you may be “burned out” from implementation, remember there is still work to do. Don’t produce a poorly witten paper or give a poorly organized presentation.  That will negate much of your good work. Put in the time needed to prepare both a well written, high-quality final report and a well organized, polished presentation. A good job on these last steps will insure that you receive the marks that fairly represents the work you have done.


Tips for Perfect Final Year Project

For an effective project, it is advisable to carry out the following activities
  • Defining the objectives of the project.
  •  Acquiring background information about the problem and its possible solutions.
  • Establishing the criteria by which your solution(s) to the problem will be judged.
  • Determining by what process the work will be carried out.
  • Planning the detailed phases of the project.
  • Adopting one or more design methodologies.Analysing requirements.
  • Using (or constructing) tools.
  • Construction of one or more artefacts (hardware, software, document).
  • Evaluating your solution to the problem.Reporting on your work.


    Whatever the nature of the problem you set out to solve, the conclusion of your project should be whether you solved it successfully or not.

Quotes

The monogram of our national initials, which is the symbol for our monetary unit, the dollar, is almost as frequently conjoined to the figures of an engineer's calculations as are the symbols indicating feet, minutes, pounds, or gallons. … This statement, while true in regard to the work of all engineers, applies particularly to that of the mechanical engineer..
— Henry R(obinson) Towne
"We don't see the things the way they are, We see things the Way We are"- Talmund

"Opportunity is missed by most people because it is dressed in overall and looks like work"
- Thomas A Edison


GATE Books for Mechanical Engineering

GATE Books for Mechanical Engineering
S.NO.       SUBJECT                                                                         AUTHOR
1               ENGINEERING Thermodynamics                      P.K. Nag; Cen gel and Boles
2.              I.C. Engine                                                           R.P. Sharma M. L. Mathur, R. P. Sharma
3.             Gas Turbine and Propulsive Systems                    PR Khajuria & SP Dubey; V ganesan
4.             Fluid Mechanics                                                    D.S. Kumar; k.l.kumar; Cengel                                                                                                 & Cimbala, Frank m. white
5.             Compressible Flow                                                S.M. Yahya; John D. Anderson
6.             Heat and Mass Transfer                                         P. K Nag; JP Hollman; D.S. Kumar;                                                                                                          R.C. Sachdeva
7.             Refrigeration and Air Conditioning                       P. K Nag; CP Arora; Domkundwar
8.             Fluid Machinery                                                     D. S. Kumar; Jagdish Lal; RK Bansal
9.            Theory of Machines                                                S S Rattan , Thomas Bevan
10.          Mechanical Vibration                                              V.P Singh; G.K. Grover
11.          Machine Design                                                      Shigley , VB Bhandari
12.          Material Science                                                     WD Callister IP Singh
13.          Production Engg.                                                    P. N. Rao ( Vol I & II) ,Kalpkjian Schmid                                                                                                Amitabh Ghosh & AK Malik
14.         Industrial Engg.                                                       O. P. Khanna Buffa & Sarin
15.         Operations Research                                               A.M. Natarajan, P.Balasubramani
16.         Strength of Materials                                              Timoshenko gere, RAMAMRUTHAM,
                                                                                              B.C. Punamia

Bench Vice Assembly

Bench vise - a holding device attached to a workbench; has two jaws to hold workpiece firmly in place. vise. holding device - a device for holding something. jaw - holding device consisting of one or both of the opposing parts of a tool that close to hold an object.




Plumber Block Assembly

A pillow block, also known as a plummer block or bearing housing, is a pedestal used to provide support for a rotating shaft with the help of compatible bearings & various accessories. Housing material for a pillow block is typically made of cast iron or cast steel.

Selection

Pillow blocks are usually referred to the housings which have a bearing fitted into them and thus the user need not purchase the bearings separately. Pillow blocks are usually mounted in cleaner environments and generally are meant for lesser loads of general industry. These differ from "plummer blocks" which are bearing housings supplied without any bearings and are usually meant for higher load ratings and corrosive industrial environments. However the terms pillow block and plummer block are used interchangeably in certain parts of the world.
The fundamental application of both types is the same which is to mount bearings safely enabling their outer ring to be stationary while allowing rotation of the inner ring. The housing is bolted to a foundation through the holes in the base. Bearing housings are either split type or unsplit type. Split type housings are usually two piece housings where the cap and base can be detached, while certain series are one single piece housings. Various seals are provided to prevent dust and other contaminants from entering the housing. Thus the housing provides a clean environment for the expensive bearings to freely rotate, hence increasing their performance and duty cycle.
Bearing housings are usually made of grey cast iron. However various grades of metals can be used to manufacture the same.
ISO 113 specifies internationally accepted dimensions for plummer blocks.

Tuesday 18 August 2015

Carburetor

A carburetor (American and Canadian spelling), carburator , carburettor, or carburetter ( Commonwealth spelling ) is a device that blends air and fuel for an internal combustion engine. It is sometimes colloquially shortened to carb in North America or carby in Australia. [citation needed]
Etymology
The word carburetor comes from the French carbure meaning " carbide". [1] Carburer means to combine with carbon. In fuel chemistry, the term has the more specific meaning of increasing the carbon (and therefore energy) content of a fluid by mixing it with a volatile hydrocarbon.
History and development
The carburetor was invented by an Italian, Luigi De  Cristoforis, in 1876. [citation needed] A carburetor was developed by Enrico Bernardi at the University of Padua in 1882, for his "Motrice Pia", the first petrol combustion engine (one cylinder, 121.6 cc) prototyped on 5 August 1882.[ citation needed ]
A carburetor was among the early [when? ] patents by Karl Benz as he developed internal combustion engines and their components. [2]
Early carburetors were the surface carburetor type, in which air is charged with fuel by being passed over the surface of gasoline. [3]
The world's first carburetor for the stationary engine was invented by the Hungarian engineers János Csonka and Donát Bánki in 1893.[4][5] Parallel to this, the Austrian automobile pioneer Siegfried Marcus invented the rotating brush carburetor .[citation needed]
Frederick William Lanchester of Birmingham, England, experimented with the wick carburetor in cars. In 1896, Frederick and his brother built the first gasoline-driven car in England: a single cylinder 5 hp (3.7 kW) internal combustion engine with chain drive. Unhappy with the performance and power, they re-built the engine the next year into a two-cylinder horizontally opposed version using his new wick carburetor design.
In 1885, Wilhelm Maybach and Gottlieb Daimler developed a float carburetor for their engine based on the atomizer nozzle.[6]
Carburetors were the usual method of fuel delivery for most US-made gasoline -fueled engines up until the late 1980s, when fuel injection became the preferred method. [7] (This change was dictated more by the requirements of catalytic converters than by any inherent inefficiency of carburation; a catalytic converter requires much more precise control over the fuel / air mixture, to closely control the amount of oxygen in the exhaust gases.) In the U.S. market, the last carbureted cars were:
1990 (General public) : Oldsmobile Custom Cruiser, Buick Estate Wagon, Cadillac Brougham, Honda Prelude (Base Model), Subaru Justy
1991 (Police) : Ford Crown Victoria Police Interceptor with the 5.8 L (351 cu in) engine.
1991 (SUV) : Jeep Grand Wagoneer with the AMC 360 engine.
1993 Mazda B2200 (Light Truck)
1994 (Light truck) : Isuzu[8]
In Australia, some cars continued to use carburetors well into the 1990s; these included the Honda Civic (1993), the Ford Laser (1994), the Mazda 323 and Mitsubishi Magna sedans (1996), the Daihatsu Charade (1997), and the Suzuki Swift (1999). Low-cost commercial vans and 4WDs in Australia continued with carburetors even into the 2000s, the last being the Mitsubishi Express van in 2003. Elsewhere, certain Lada cars used carburetors until 2006.
Many motorcycles still use carburetors for simplicity's sake, since a carburetor does not require an electrical system to function. Carburetors are also still found in small engines and in older or specialized automobiles , such as those designed for stock car racing , though NASCAR 's 2011 Sprint Cup season was the last one with carbureted engines; electronic fuel injection was used beginning with the 2012 race season in Cup. [9]
Principles
The carburetor works on Bernoulli's principle : the faster air moves, the lower its static pressure, and the higher its dynamic pressure. The throttle (accelerator) linkage does not directly control the flow of liquid fuel. Instead, it actuates carburetor mechanisms which meter the flow of air being pulled into the engine. The speed of this flow, and therefore its pressure, determines the amount of fuel drawn into the airstream.
When carburetors are used in aircraft with piston engines, special designs and features are needed to prevent fuel starvation during inverted flight. Later engines used an early form of fuel injection known as a pressure carburetor . Most production carbureted (as opposed to fuel-injected ) engines have a single carburetor and a matching intake manifold that divides and transports the air fuel mixture to the intake valves, though some engines (like motorcycle engines) use multiple carburetors on split heads. Multiple carburetor engines were also common enhancements for modifying engines in the USA from the 1950s to mid-1960s, as well as during the following decade of high- performance muscle cars fueling different chambers of the engine's intake manifold .
Older engines used updraft carburetors, where the air enters from below the carburetor and exits through the top. This had the advantage of never "flooding" the engine, as any liquid fuel droplets would fall out of the carburetor instead of into the intake manifold ; it also lent itself to use of an oil bath air cleaner, where a pool of oil below a mesh element below the carburetor is sucked up into the mesh and the air is drawn through the oil-covered mesh; this was an effective system in a time when paper air filters did not exist.
Beginning in the late 1930s, downdraft carburetors were the most popular type for automotive use in the United States. In Europe, the sidedraft carburetors replaced downdraft as free space in the engine bay decreased and the use of the SU-type carburetor (and similar units from other manufacturers) increased. Some small propeller-driven aircraft engines still use the updraft carburetor design. The main disadvantage of basing a carburetor's operation on Bernoulli's principle is that, being a fluid dynamic device, the pressure reduction in a venturi tends to be proportional to the square of the intake air speed. The fuel jets are much smaller and limited mainly by viscosity, so that the fuel flow tends to be proportional to the pressure difference. So jets sized for full power tend to starve the engine at lower speed and part throttle. Most commonly   this has been corrected by using multiple jets. In SU and other movable jet carburetors, it was corrected by varying the jet size. For cold starting, a different principle was used in multi-jet carburetors. A flow resisting valve called a choke, similar to the throttle valve, was placed upstream of the main jet to reduce the intake pressure and suck additional fuel out of the jets.
Operation
Fixed- venturi, in which the varying air velocity in the venturi alters the fuel flow; this architecture is employed in most carburetors found on cars.
Variable-venturi , in which the fuel jet opening is varied by the slide (which simultaneously alters air flow). In "constant depression" carburetors, this is done by a vacuum operated piston connected to a tapered needle which slides inside the fuel jet. A simpler version exists, most commonly found on small motorcycles and dirt bikes, where the slide and needle is directly controlled by the throttle position. The most common variable venturi (constant depression) type carburetor is the sidedraft SU carburetor and similar models from Hitachi, Zenith-Stromberg and other makers. The UK location of
the SU and Zenith -Stromberg companies helped these  arburetors rise to a position of domination in the UK car market, though such carburetors were also very widely used on Volvos and other non-UK makes.
Other similar designs have been used on some European and a few Japanese automobiles. These carburetors are also referred to as "constant velocity" or "constant vacuum" carburetors. An interesting variation was Ford's VV (Variable Venturi) carburetor, which was essentially a fixed venturi carburetor with one side of the venturi hinged and movable to give a narrow throat at low rpm
and a wider throat at high rpm. This was designed to provide good mixing and airflow over a range of engine speeds, though the VV carburetor proved problematic in service.
A high performance 4-barrel carburetor. Under all engine operating conditions, the carburetor must: Measure the airflow of the engine Deliver the correct amount of fuel to keep the fuel/air mixture in the proper range (adjusting for factors such as temperature)
Mix the two finely and evenly
This job would be simple if air and gasoline (petrol) were ideal fluids; in practice, however, their deviations from ideal behavior due to viscosity, fluid drag, inertia, etc. require a great deal of complexity to compensate for exceptionally high or low engine speeds. A carburetor must provide the proper fuel/air mixture across a wide range of ambient temperatures, atmospheric pressures, engine speeds and loads, and centrifugal forces :
Cold start
Hot start
Idling or slow-running
Acceleration
High speed / high power at full throttle
Cruising at part throttle (light load)
In addition, modern carburetors are required to do this while maintaining low rates of exhaust emissions . To function correctly under all these conditions, most carburetors contain a complex set of mechanisms to support several different operating modes, called circuits.
Basics Cross-sectional schematic of a downdraft carburetor
A carburetor basically consists of an open pipe through which the air passes into the inlet manifold of the engine. The pipe is in the form of a venturi: it narrows in section and then widens again, causing the airflow to increase in speed in the narrowest part. Below the venturi is a butterfly valve called the throttle valve — a rotating disc that can be turned end-on to the airflow, so as to hardly restrict the flow at all, or can be rotated so that it (almost) completely blocks the flow of air. This valve controls the flow of air through the carburetor throat and thus the quantity of air/fuel mixture the system will deliver, thereby regulating engine power and speed. The throttle is connected, usually through a cable or a mechanical linkage of rods and joints or rarely by pneumatic link , to the accelerator pedal on a car or the equivalent control on other vehicles or equipment.
Fuel is introduced into the air stream through small holes at the narrowest part of the venturi and at other places where pressure will be lowered when not running on full throttle. Fuel flow is adjusted by means of precisely calibrated orifices, referred to as jets , in the fuel path.
Off-idle circuit
As the throttle is opened up slightly from the fully closed position, the throttle plate uncovers additional fuel delivery holes behind the throttle plate where there is a low pressure area created by the throttle plate blocking air flow; these allow more fuel to flow as well as compensating for the reduced vacuum that occurs when the throttle is opened, thus smoothing the transition to metering fuel flow through the regular open throttle circuit.
Main open-throttle circuit
As the throttle is progressively opened, the manifold vacuum is lessened since there is less restriction on the airflow, reducing the flow through the idle and off-idle circuits. This is where the venturi shape of the carburetor throat comes into play, due to Bernoulli's principle (i.e., as the velocity increases, pressure falls). The venturi raises the air velocity, and this high speed and thus low pressure sucks fuel into the airstream through a nozzle or nozzles located in the center of the venturi. Sometimes one or more additional booster venturis are placed coaxially within the primary venturi to increase the effect.
As the throttle is closed, the airflow through the venturi drops until the lowered pressure is insufficient to maintain this fuel flow, and the idle circuit takes over again, as described above.
Bernoulli's principle, which is a function of the velocity of the fluid, is a dominant effect for large openings and large flow rates, but since fluid flow at small scales and low speeds (low Reynolds number ) is dominated by viscosity, Bernoulli's principle is ineffective at idle or slow running and in the very small carburetors of the smallest model engines. Small model engines have flow restrictions ahead of the jets to reduce the pressure enough to suck the fuel into the air flow. Similarly the idle and slow running jets of large carburetors are placed after the throttle valve where the pressure is reduced partly by viscous drag, rather than by Bernoulli's principle. The most common rich mixture
device for starting cold engines was the choke, which works on the same principle.
Power valve
For open throttle operation a richer mixture will produce more power, prevent pre-ignition detonation , and keep the engine cooler. This is usually addressed with a spring- loaded "power valve", which is held shut by engine vacuum. As the throttle opens up, the vacuum decreases and the spring opens the valve to let more fuel into the main circuit. On two-stroke engines , the operation of the power valve is the reverse of normal — it is normally "on" and at a set rpm it is turned "off". It is activated at high rpm to extend the engine's rev range, capitalizing on a two-stroke's tendency to rev higher momentarily when the mixture is lean.

Alternative to employing a power valve, the carburetor may utilize a metering rod or step-up rod system to enrich the fuel mixture under high-demand conditions. Such systems were originated by Carter Carburetor [citation needed] in the 1950s for the primary two venturis of their four barrel carburetors, and step-up rods were widely used on most 1-, 2-, and 4-barrel Carter carburetors through the end of production in the 1980s. The step-up rods are tapered at the bottom end, which extends into the main metering jets. The tops of the rods are connected to a vacuum piston and/or a mechanical linkage which lifts the rods out of the main jets when the throttle is opened (mechanical linkage) and/or when manifold vacuum drops (vacuum piston). When the step-up rod is lowered into the main jet, it restricts the fuel flow. When the step-up rod is raised out of the jet, more fuel can flow through it. In this manner, the amount of fuel delivered is tailored to the transient demands of the engine. Some 4-barrel carburetors use metering rods only on the primary two venturis, but some use them on both primary and secondary circuits, as in the Rochester Quadrajet.
Accelerator pump
Liquid gasoline, being denser than air, is slower than air to react to a force applied to it. When the throttle is rapidly opened, airflow through the carburetor increases immediately, faster than the fuel flow rate can increase. This transient oversupply of air causes a lean mixture, which makes the engine misfire (or "stumble")—an effect opposite what was demanded by opening the throttle. This is remedied by the use of a small piston or diaphragm pump which, when actuated by the throttle linkage, forces a small amount of gasoline through a jet into the carburetor throat. [10] This extra shot of fuel counteracts the transient lean condition on throttle tip-in.
Most accelerator pumps are adjustable for volume and/or duration by some means. Eventually the seals around the moving parts of the pump wear such that pump output is reduced; this reduction of the accelerator pump shot causes stumbling under acceleration until the seals on the pump are renewed. The accelerator pump is also used to prime the engine with fuel prior to a cold start. Excessive priming, like an improperly adjusted choke, can cause flooding . This is when too much fuel and not enough air are present to support combustion. For this reason, most carburetors are equipped with an unloader mechanism: The accelerator is held at wide open throttle while the engine is cranked, the unloader holds the choke open and admits extra air, and eventually the excess fuel is cleared out and the engine starts.
Choke
When the engine is cold, fuel vaporizes less readily and tends to condense on the walls of the intake manifold, starving the cylinders of fuel and making the engine difficult to start; thus, a richer mixture (more fuel to air) is required to start and run the engine until it warms up. A richer mixture is also easier to ignite.
To provide the extra fuel, a choke is typically used; this is a device that restricts the flow of air at the entrance to the carburetor, before the venturi. With this restriction in place, extra vacuum is developed in the carburetor barrel, which pulls extra fuel through the main metering system to supplement the fuel being pulled from the idle and off-idle circuits. This provides the rich mixture required to sustain operation at low engine temperatures.
In addition, the choke can be connected to a cam (the fast idle cam) or other such device which prevents the throttle plate from closing fully while the choke is in operation. This causes the engine to idle at a higher speed. Fast idle serves as a way to help the engine warm up quickly, and give a more stable idle while cold by increasing airflow throughout the intake system which helps to better atomize the cold fuel.
In many carbureted cars, the choke is controlled by a cable connected to a pull-knob on the dashboard operated by the driver. In some carbureted cars it is automatically controlled by a thermostat employing a bimetallic spring , which is exposed to engine heat, or to an electric heating element. This heat may be transferred to the choke thermostat via simple convection, via engine coolant, or via
air heated by the exhaust. More recent designs use the engine heat only indirectly: A sensor detects engine heat and varies electrical current to a small heating element, which acts upon the bimetallic spring to control its tension, thereby controlling the choke. A choke unloader is a linkage arrangement that forces the choke open against its spring when the vehicle's accelerator is moved to the end of its travel. This provision allows a "flooded" engine to be cleared out so that it will start.
Some carburetors do not have a choke but instead use a mixture enrichment circuit, or enrichment. Typically used on small engines, notably motorcycles, enrichments work by opening a secondary fuel circuit below the throttle valves. This circuit works exactly like the idle circuit, and when engaged it simply supplies extra fuel when the throttle is closed.
Classic British motorcycles, with side-draft slide throttle carburetors, used another type of "cold start device", called a "tickler". This is simply a spring-loaded rod that, when depressed, manually pushes the float down and allows excess fuel to fill the float bowl and flood the intake tract. If the "tickler" is held down too long it also floods the outside of the carburetor and the crankcase below, and is therefore a fire hazard.
Other elements The interactions between each circuit may also be affected by various mechanical or air pressure connections and also by temperature sensitive and electrical components. These are introduced for reasons such as response, fuel efficiency or automobile emissions control . Various air
bleeds (often chosen from a precisely calibrated range, similarly to the jets) allow air into various portions of the fuel passages to enhance fuel delivery and vaporization. Extra refinements may be included in the carburetor/ manifold combination, such as some form of heating to aid fuel vaporization such as an early fuel evaporator .
Fuel supply
Float chamber
Holley "Visi-Flo" model #1904 carburetors from the 1950s, factory equipped with transparent glass bowls. To ensure a ready mixture, the carburetor has a "float chamber" (or "bowl") that contains a quantity of fuel at near-atmospheric pressure, ready for use. This reservoir is constantly replenished with fuel supplied by a fuel pump . The correct fuel level in the bowl is maintained by means of a float controlling an inlet valve , in a manner very similar to that employed in a cistern (e.g. a toilet tank).
As fuel is used up, the float drops, opening the inlet valve and admitting fuel. As the fuel level rises, the float rises and closes the inlet valve. The level of fuel maintained in the float bowl can usually be adjusted, whether by a setscrew or by something crude such as bending the arm to which the float is connected. This is usually a critical adjustment, and the proper adjustment is indicated by lines inscribed into a window on the float bowl, or a measurement of how far the float hangs below the top of the carburetor when disassembled, or similar.
Floats can be made of different materials, such as sheet brass soldered into a hollow shape, or of plastic; hollow floats can spring small leaks and plastic floats can eventually become porous and lose their flotation; in either case the float will fail to float, fuel level will be too high, and the engine will not run unless the float is replaced. The valve itself becomes worn on its sides by its motion in its "seat" and will eventually try to close at an angle, and thus fails to shut off the fuel completely; again, this will cause excessive fuel flow and poor engine operation.
Conversely, as the fuel evaporates from the float bowl, it leaves  sediment, residue, and varnishes behind, which clog the passages and can interfere with the float operation. This is particularly a problem in automobiles operated for only part of the year and left to stand with full float chambers for months at a time; commercial fuel stabilizer additives are available that reduce this problem.
The fuel stored in the chamber (bowl) can be a problem in hot climates. If the engine is shut off while hot, the temperature of the fuel will increase, sometimes boiling ("percolation"). This can result in flooding and difficult or impossible restarts while the engine is still warm, a phenomenon known as "heat soak". Heat deflectors and insulating gaskets attempt to minimize this effect. The Carter Thermo-Quad carburetor has float chambers manufactured of insulating plastic (phenolic), said to keep the fuel twenty degrees (F.) cooler.
Usually, special vent tubes allow atmospheric pressure to be maintained in the float chamber as the fuel level changes; these tubes usually extend into the carburetor  throat. Placement of these vent tubes is critical to prevent fuel from sloshing out of them into the carburetor, and sometimes they are modified with longer tubing. Note that this leaves the fuel at atmospheric pressure, and therefore it cannot travel into a throat which has been pressurized by a supercharger mounted upstream; in such cases, the  entire carburetor must be contained in an airtight pressurized box to operate. This is not necessary in  installations where the carburetor is mounted upstream of the supercharger, which is for this reason the more frequent system. However, this results in the supercharger being filled with compressed fuel/air mixture, with a strong tendency to explode should the engine backfire ; this type of explosion is frequently seen in drag races, which for safety reasons now incorporate pressure releasing blow-off plates on the intake manifold, breakaway bolts holding the supercharger to the manifold, and shrapnel-catching ballistic nylon blankets surrounding the superchargers.
Diaphragm chamber
If the engine must be operated in any orientation (for example a chain saw ), a float chamber is not suitable. Instead, a diaphragm chamber is used. A flexible diaphragm forms one side of the fuel chamber and is arranged so that as fuel is drawn out into the engine, the diaphragm is forced inward by ambient air pressure. The diaphragm is connected to the needle valve and as it moves inward it opens the needle valve to admit more fuel, thus replenishing the fuel as it is consumed. As fuel is
replenished the diaphragm moves out due to fuel pressure and a small spring, closing the needle valve. A balanced state is reached which creates a steady fuel reservoir level, which remains constant in any orientation.