Experimental, numerical and exergy analyses of a dual fuel combustion engine fuelled with syngas and biodiesel/diesel blends

This work investigates the effects of addition of syngas and biodiesel on a reactivity controlled compression ignition (RCCI) engine fuelled with diesel. Scanning electron microscopy (SEM) of exhaust particulate matter has been done to obtain particulate matter (PM) morphology. Energy and exergy analyses have been performed to observe energy and availability shares, and to provide directions for the energy recovery systems. Closed cycle combustion simulations have been performed to complement the experimental results and for an improved understanding of in-cylinder dynamics. Chemical and physical properties of three biodiesel samples have been analysed using elemental analysis, Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry. Based on the initial study, used cooking oil based biodiesel blend (B20, 20% biodiesel) has been chosen in experiments. The optimal operating conditions for syngas/diesel and syngas/B20 in RCCI mode for different operating parameters have been investigated. Injection pressure, injection timing and pre-injection mass ratio have been modified to get improved combustion efficiency at mid-load. Syngas/diesel mode with an injection timing of 19 degrees before top dead centre (bTDC) shows slightly higher brake thermal efficiency (BTE) with 22% and 77% lower oxides of nitrogen (NOx) and PM respectively as compared to conventional diesel combustion. In syngas/B20 mode, a maximum BTE of 24% has been observed for the case with a pre-injection at 50 degrees bTDC with 30% mass fraction and 18 degrees bTDC main injection timing. Syngas/diesel shows a reduction in primary soot particle count by about 67% and contains larger aggregates as compared to neat diesel.