Combustion of the biomethane in an IC engine with over-expanded cycle

Abstract

The paper presents results of the experimental investigation on an internal combustion (IC) over-expanded engine fueled with biomethane. During this research the pressure trace of the combustion was collected and on that basis the analysis of the combustion process has been made. The measurements were done for two engine configurations with the classic Otto cycle and the over-expanded cycle. Over-expanded cycle was achieved by changing the intake cam profile and provide earlier intake valve closure before BDC. To recompense the lost in the engine power a supercharging was used. Additionally, during the measurements the parameters as TDC position, crankshaft position, temperature of both the intake air, the engine coolant and fuel were collected. On the basis of those measurements the characteristics of the pressure as functions of crank angle and mass fraction burned (x b ) were performed to show possibilities for different engine configurations. As a result of this research, it can be concluded that the over-expanded cycle in the IC engine leads to increase in thermal efficiency and the supercharging is a proper measure to compensate losses in engine power caused by use the over-expanded cycle.