Development of a modified diesel engine cycle

Abstract

This paper presents an investigation of a novel type of diesel engine cycle, an approximate constant pressure cycle. The prototype engine is called the diesel engine with oil cushioned piston (DEOCP). In contrast to conventional engines, the DEOCP has a variable cylinder volume which is controlled automatically by the engine's cylinder pressure. The variable cylinder pressure is achieved by inserting a hydraulic cylinder into the engine's piston rod. The engine cylinder pressure is thus self-controlled and an ideal constant pressure cycle can theoretically be achieved. Computer simulations and engine tests have shown that the DEOCP distinguishes itself with high cycle efficiency, improved low-load performance and good starting ability. A detailed theoretical analysis and test results are presented in the paper, as well as a discussion of existing problems and possible further developments. Development of the diesel engine with oil cushioned piston could break the limit of cycle efficiency of conventional engines, hence opening a new avenue for diesel engine development.