Correct Answer - Option 2 : Both Statement (I) and Statement (II) are individually true but Statement (II) is NOT the correct explanation of Statement (I)
Concept:
In internal combustion engines, the products of combustion are expelled to its surroundings and this makes these engines operate on open cycles.
For each cycle, fresh charge (a mixture of air and fuel) is introduced. To study the operations and performances of these engines, they are represented with theoretical engines operating on thermodynamic cycles and these theoretical engines are referred to as air standard engines.
They are called air standard engines because their working fluid is taken to be majorly air.
In these engines, heat is added from an external source as opposed to burning fuel and a heat sink is provided as opposed to exhaust, thus returning the air back to its original state.
The following assumptions are made for the air standard cycle:
- The working fluid (air) has a constant mass throughout the entire air cycle and air is taken to be ideal.
- The air maintains a constant specific heat capacity throughout the cycle.
- The combustion process is replaced by a heat transfer process from an external heat source.
- The cycle is completed by the heat transfer to the surrounding in contrast to the exhaust and the intake processes of an actual engine.
- All the processes are internally reversible.
The composition of nitrogen in air and fuel mixture is high that is 79% by mass or 77 % by volume.
According to air standard cycle, nitrogen does not undergo any changes or any chemical reaction in the combustion chamber.
Both the statements are individually true and statement 2 is not the correct explanation of statement 1.
