Introduction

For the purpose of thermodynamic analysis of the internal combustion engines, the following approximations are made:

1. The engine is assumed to operate on a closed cycle with a fixed mass of air which does not undergo any chemical change.
   
   
2. The combustion process is replaced by an equivalent energy addition process from an external source.
   
   
3. The exhaust process is replaced by an equivalent energy rejection process to external surroundings by means of which the working fluid is restored to the initial state.
   
   
4. The air is assumed to behave like an ideal gas with constant specific heat. These cycles are usually referred to as air standard cycle.