Investigation of cyclic variations in air-fuel ratio, cylinder wall temperature, and residual gas fraction of a dual fuel compression ignition engine

Abstract

Dual fuel operation in compression ignition engines is an effective way to reduce the NOx emission. Within the certain range of fuel premixing ratio (PR), the dual fuel operation in CI-engines results in improved thermal efficiency. The dual fuel CI-engine has relatively higher cyclic variations in comparison to conventional CI-engine which limits the range of fuel premixing in dual fuel CI-engine. The cyclic variations in air-fuel ratio, cylinder wall temperature, and residual gas fraction are the major factors, which governs the variations in combustion parameters. The cyclic variations in combustion need to control for stable engine operation. The present study estimates the cyclic air-fuel ratio, cylinder wall temperature, and residual gas fraction from the measured in-cylinder pressure data of dual-fuel CI-engine. The experiments are performed on a modified single cylinder CI-engine equipped with a separate port fuel injector and its controller to operate an engine in dual fuel mode. In this study, 1500 consecutive engine cycles are recorded, and air-fuel ratio, cylinder wall temperature, and the residual gas fraction is estimated for each cycle. Pressure moment method is used to estimate the cyclic air-fuel ratio. The cyclic cylinder wall temperature is calculated by determining the inversion angle. The cyclic variations are analyzed using statistical methods.