1. What is the difference between scavenging and supercharging ?
Ans: Scavenging is process of flushing out burnt gases from engine cylinder by introducing fresh air in the cylinder before exhaust stroke ends. Supercharging is the process of supplying higher mass of air by compressing the atmospheric air.
2. What are the names given to constant temperature, constant pressure, constant volume, constant internal energy, constant enthalpy, and constant entropy processes.
Ans: Isothermal, isochroic, isobaric, free expression, throttling and adiabatic processes respectively.
3. In a Rankine cycle if maximum steam pressure is increased keeping steam temperature and condenser pressure same, what will happen to dryness fraction of steam after expansion ?
Ans: It will decrease.
4. Why entropy change for a reversible adiabatic process is zero ?
Ans: Because there is no heat transfer in this process.
5. What are two essential conditions of perfect gas ?
Ans: It satisfies equation of state and its specific heats are constant.
6. Enthalpy and entropy are functions of one single parameter. Which is that ?
Ans: Temperature.
7. Why rate of condensation is higher on a polished surface compared to rusty surface ?
Ans: Polished surface promotes drop wise condensation and does not wet the surface.
8. Why Entropy decreases with increase in temperature?
Ans. ds=dQ/T Entropy is inversely proportional to the temperature so, as temp. Increases, entropy decreases.
9. Why different types of sound are produced in different bikes, though they run on SI Engines?
Ans. Engine specifications are different in different manufactures like as Bore Diameter (CC), Ignition timing. Also the exhaust passage takes more responsible for sound.
10. How much Watt means 1Hp?
Ans. 746.2 Watt
11. Explain Bicycle Rear Wheel Sprocket working?
Ans. Rear wheel sprocket works under the principle of ratchet and pawl.
12. Definition of Octane Number and Cetane Number?
Ans. Octane No.- Octane number is defined as the percentage, by volume, of iso octane in the mixture of iso octane and h-heptane. It is the measure of rating of SI engine.
Cetane No.- Cetane number is defined as the percentage, by volume, of n-cetane in the mixture of n-cetane and alpha methyl naphthalene. It is the measure of rating of CI engine.
13. Which Mechanism is used in Automobile gearing System?
Ans. Differential mechanism
14. When Crude Oil is Heated, Which Hydro Carbon comes first?
Ans. Natural gas (Gasoline)… at 20 Celsius
15. How to calculate Bearing number ti Diameter of the inner and outer?
Ans. Divide the shaft diameter size by 5, it will give last two digit of the bearing no. and according to type of load we have to choose the type of bearing and that will give prior number of the bearing.
16. The Fatigue life of a part can be improved by?
Ans. Improving the surface finish by Polishing & providing residual stress by Shot peening.
17. What happens if gasoline is used in a Diesel Engine, Siesel Engine will work?
Ans. No, It will not work, as the Compression ratio of Petrol engine is 6 to 10 & that of Diesel engine is 15 to 22. Thus on such high compression, gasoline gets highly compressed & it may blast
11. Poissons Ratio is Higher in, Rubber/Steel/Wood?
Ans. When a material is compressed in one direction, it usuallytends to expand in the other two directions perpendicular tothe direction of compression. This phenomenon is called thePoisson effect. Poisson’s ratio is a measure of the Poisson effect.
For rubber = 0.5
For steel = 0.288
For wood < 0.2
12. What is the difference between Fan and Blower?
Ans. Fan is an air pushing device. Either Axial or Centrifugal type systems are used to move the air in low pressure. It is rotated by a motor separately.
When the fan is a housing of blades and motor, then it called as Blower. It directs the air in a single path with high pressure.
13. What is Heat Rate of Power Plant?
Ans. Heat rate is a measure of the turbine efficiency. It is determined from the total energy input supplied to the Turbine divided by the electrical energy output
14. What is Hydrodynamic Cavitation?
Ans. Hydrodynamic cavitation describes the process of vaporization in a constrained channel at a specific velocity.
Bubble generation and Bubble implosion which occurs in a flowing liquid as a result of a decrease and subsequent increase in pressure.
15. What is Difference between Hardness and Toughness?
Ans. Toughness is the ability of a material to absorb energy.
Hardness is the ability of a material to withstand wear.
16. What is the hottest part of Refrigerant in Refrigeration?
Ans. Compressor
17. What does F.O.F Stand for Piping Design?
Ans. Face of Flange, The F.O.F (Raised face and Flat face) is used to know the accurate dimension of the flange in order to avoid the minute errors in measurement in case of vertical or horizontal pipe lines.
18. Where Multi stage Pump is Used?
Ans. Pressure washing of Aircraft, Trains, Boats and Road vehicles as well as Spray washing of industrial parts and Electronic components.
19. What does pump develop:- (a) Flow (b) Pressure
Ans. A pump does not create pressure, it only creates flow. Pressure is a measurement of the resistance to flow.
20. How to measure temperature of Bearing?
Ans. Normally the temperature range from 80 degree to 110 degree Celsius. So the following temperature measurement devices are used.
· Dial Type Bearing Temperature Detector
· Stator Winding Temperature Detector
· Resistance Bearing Temperature Detector (Bearing RTD)
· Specialized in Pin type RTD
21. Difference between Performance and Efficiency?
Ans. The accomplishment of a given task measured against preset known standards of accuracy, completeness, cost, and speed is called as Performance.
Efficiency is defined as the input given and the work obtained from that input like money, time, labour etc. It’s the main factor of productivity.
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