ABSTRACT
Internal combustion engines may be divided into two types depending on whether they deliver their energy via a reciprocating piston or a rotating turbine. The majority of piston engines operate either on the Otto cycle, in which the combustion is spark-initiated, or on the diesel cycle, in which autoignition occurs in the hot, compressed charge. The principles of operation of internal combustion engines are addressed as required in order to appreciate the principles of the combustion processes involved and the attainment of optimum performance, including the environmental impact. Multivalve and variable valve-timing systems are used in current engines to optimise the gas motion for the most efficient combustion under given operating conditions. Improved control over fluid motion within the combustion chamber itself has enabled a revision of combustion chamber designs in later development of engines. Both premixed vapour phase combustion and the diffusion controlled burning of fuel droplets occur in a diesel engine.
