Experimental study on the effect of active engine thermal management on a bi-fuel engine performance, combustion and exhaust emissions

Abstract

Compressed natural gas (CNG) is a promising alternative fuel to environmental benefits, and the ignition temperature of CNG is higher than gasoline fuel. The cooling system at that point needs to be modified for the bi-fuel engine operation. On the other hand, the active engine thermal management (ETM) can give enhanced coolant temperature regulation during transient and steady-state operation. However, the aim of the present work was to experimentally investigate the spark ignition (SI) engine performance, combustion characteristics and exhaust gas emissions produced under a variety of operating conditions for gasoline and CNG. A comparative analysis of the brake-specific fuel consumption (BSFC), fuel conversion efficiency, cylinder pressure, heat release rate (HRR), exhaust emissions such as THC, CO, CO2 and NOx has been measured for gasoline and CNG, under the engine equipped by either conventional or active ETM coolant system. The effects of engine coolant temperature on performance, HRR and emissions are evaluated. The results indicate that active ETM improves the performance and HRR of a bi-fuel engine. It was found that active ETM generally had lower BSFC (3.53–5.82%) for both fuels and higher fuel conversion efficiency (5.7–7.8%) than those of conventional cooling system. Active ETM shows significantly lower emissions of THC, CO2 and CO; however, NOx emission shows irregular behavior for both fuels.