Question Set 28 – Mechanical Engineering

# Question Set 28

Question No. 1

How the analyses and calorific values of fuels can be reported?

It may be reported as:

(A) As received or fired (wet) basis

(B) Dry or moisture free basis

(C) Combustible or ash and moisture free basis

Question No. 2

We have read that when the piston goes up and down then the engine works i.e. the suction, compression etc. then what happens in the case of big vehicles, which start at stable condition, i.e. how does their piston moves when they are at rest. How suction, compression etc?

Smaller vehicles like bikes, cars are started with the help of motors. Initially, motors turn the crank shaft till sufficient suction pressure is reached. When sufficient suction pressure is reached, the engine starts to suck the fuel in and then the cycle begins when the fuel is taken in and ignited. Similarly, for huge engines, instead of motors, we use starting air. air at a pressure of 10-30 bar is fed to the engine which is at rest. This air rotates the engine till it attains sufficient suction pressure. Once the pressure is reached, the cycle starts and it starts firing.

Question No. 3

The Compression ratio of Petrol engine is always less than Compression Ratio of Diesel engine why?

Petrol is not self igniting; it needs spark to flame up in chamber. Whereas diesel is self igniting in diesel engine, to attain that state it requires high temp &pressure. This temperature & pressure is more than what’s required in Petrol Engines by property of that fluid.

Question No. 4

What are the important operational performance parameters in design of fuel firing equipment?

Fuel flexibility, electrical load following capability, reliability, availability, and maintenance ease.

Question No. 5

What is the difference between total moisture and inherent moisture in coal?

The moisture content of the bulk as sampled is referred to as total moisture, and that of the air dried sample is called inherent moisture.

Question No. 6

What is the temperature of space?

The short answer is that the temperature in space is approximately 2.725 Kelvin. That means the universe is generally just shy of three degrees above absolute zero, the temperature at which molecules themselves stop moving. That’s almost -270 degrees Celsius, or -455 Fahrenheit.

Question No. 7

Proximity analysis of coal provides data for a first, general assessment of a coal’s quality and type. What elements it reports?

Moisture, volatile matter, ash and fixed carbon.

Question No. 8

Ultimate analysis of coal is elementary analysis. What it is concerned with?

Carbon, hydrogen, nitrogen, and sulfur in coal on a weight percentage basis.

Question No. 9

What are the causes of main engine black smoke?

There is many cause of black smoke.

(A) Is improper mixture of fuel supply by carburettor like very rich mixture so the fuel improper burn.

(B)  It is when piston or piston ring is fail so back side cooling oil release in combustion chamber it cause black smoke.

(C) Improper ignition system like not sufficient time of pressure rise delay period.

Question No. 10

What is the significance of torque (in Nm) given in the engine specification?