Overview

The sole purpose of combustion in a reciprocating piston engine is to shift the expansion process away from the compression process in order to generate a working cycle. The only reason for the use of fuel is to generate pressure in order to accomplish this task. This is accomplished by an exothermic (one associated with acquisition of internal energy) chemical reaction, as a consequence of which a transformation (metamorphosis) takes place in engine cylinder between the reactants at initial state, i, attained at the end of the process of compression, and the products at final state, f, established at the start of the process of expansion, as depicted on the pressure-volume (indicator) diagram in Fig. 1.1.