Interview Q & A (part-3)

1. WHAT IS 2-STROKE IC ENGINE?

1.AN 2-STROKE engine is designed by DUGLAD CLERK in 1880, the suction,compression,expansion and exhaust takes place during 2-stroke of piston.Their is 1 stroke after every revolution of the crank shift.

2. WHAT IS 4-STROKE ENGINE?

2.A 4-stroke engine is an internal combustion engine in which the piston completes four separate strokes— intake, compression, power, and exhaust— during two separate revolutions of the engine’s crankshaft, and one single thermodynamic cycle.It uses natural gas,manufactured gas.

3.WHAT IS THE DIFFERENCE BETWEEN 2-STROKE AND 4-STROKE IC ENGINE?

3.

2-stroke engine fires 1 time in each revolution whereas a 4-stroke fires 1 time in 2 revolutions.

  2-stroke is simpler and lighter, but less versatile.

 In place of valves in 4-stroke engines ,ports are present in 2-stroke engines,stroke has no valve, the piston act like a valve to control the flow of fuel..

light duty engines are 2 stroke used commonly, for heavy duty 4 stroke are used.

4.NAME THE MAIN STEPS INVOLVE IN 4-STROKE IC ENGINE?

4.Following are the steps involved in this are:

The steps involved here are:
Intake stroke: Air and vaporized fuel are drawn in.
Compression stroke: Fuel vapor and air are compressed and ignited.
Combustion stroke: Fuel combusts and piston is pushed downwards.
Exhaust stroke: Exhaust is driven out. During the 1st, 2nd, and 4th stroke the piston is relying on power and the momentum generated by the other pistons.

Four-stroke cycle (or Otto cycle)
1. Intake
2. Compression
3. Power
4. Exhaust

5.WHAT ARE THE ADVANTAGES OF LUBRICATION IN IC ENGINE?

5.It reduces the wear and tear of the moving parts.
   It damps down the vibration of the engine.
   It cleans the moving parts.
   It makes the piston gas tight.

6.NAME THE FUEL USED BY IC ENGINES?

6.Following are the types of fuels used for IC engines:

Petroleum: Petroleum spirit ,Petroleum diesel,liquified petroleum gas,Compressed natural gas,Jet fuel ,Residual fuel.

Coal: methanol ,Gasoline ,Diesel fuel.

Biofuels and vegoils: Peanut oil and other vegoils , Biobutano, biodiesel ,Dimethyl Ether, biogas,hydrogen

7. When a real gas behaves like ideal gas?

7.A real gas behaves like an ideal gas in low pressure and high temperature conditions.

8. What is the significance of entropy?

8.As per the second law of thermodynamics, any heat input to the system (Heat engine) cannot be converted completely into useful work. Some energy is lost and that is called 'unavailable work'. The amount of unavailable work increases as the entropy increases.

9.What is the difference between heat transfer and thermodynamics?

9.Heat transfer deals with the energy analysis which in transition and and depends on the modes of heat transfer like conduction, convection and radiation or combination of any modes. Heat transfer deals in non equilibrium domain and conditions while thermodynamics deals with study of system at equilibrium and does not depend on how heat transfer is calculated.

10. At which temperature thermal radiation can become zero? 

10.Not possible. Because thermal radiation becomes only zero at absolute zero temperature which can never be attained by the third law of thermodynamics.

11.What is Nominal size?

11.The Nominal size of a dimension is the size by which it is referred to as a matter of convenience.

12.Define Actual size?

12.The Actual size of a dimension is its actual measured size.

13.What do you meant by Basic size?

13.The Basic size of a dimension is the size in relation to which all limits of variation are made.

14.Define Fits?

14.The relation between two mating parts with reference to ease the assembly is called Fit.

15.Find out the least count of a vernier caliper when its main scale graduation is 49 mm and the vernier scale is divided in to 50 equal parts?

15.

Value of 1 main scale division = 1 mm
Value of 50 vernier scale divisions = 49 mm
Value of 1 vernier scale division = 49 x 50 mm or 0.98 mm
Least count = 1 M.S.D – 1 V.S.D = 1 – 0.98 = 0.02 mm

16. Name the various parts of a vernier caliper?

16.Main scale or beam

     Fixed jaw
     Movable jaw
     Vernier scale
     Fine adjusting unit
     Locking screws
     Fine adjusting screw
     Inner measuring nibs
     Depth gauge.

17.What are the purposes of Vernier Height Gauge?

17.
For making parallel lines on the work piece to the accuracy of 0.02 mm in metric system and 0.001” in inch system.

For comparing heights of finished work piece.

18.What is the use of of vernier Bevel Protractor?

18.Vernier Bevel Protractor is used to measure and check the angles of a job to the accuracy of 5’ (5 minutes).

19. Specify the term Backlash of a micrometer?

19.Backlash is the lack of motion or lost motion of the spindle when the rotation of the thimble is changed the direction.

20.What are the main merits of a vernier caliper over a micrometer?

20.

Vernier caliper is a multi purpose instrument, can be used to measure inside, outside, and depth as well, where a micrometer is not considered as multipurpose.

The different size of a job can be measured with a single vernier caliper but numbers of micrometers are needed for different sizes of job.

Vernier caliper is easy for taking measurements and simple working, where as a micrometer works with a principle of nut and bolt and quiet sensitive.

The measurements can be taken easily by a vernier caliper than by a micrometer.