Co, hc and nox emissions characteristics of a retrofitted bi-fuel natural gas engine

Abstract

This paper presents the experimental results carried out to evaluate CO, HC and NOx exhaust emissions and performance characteristics of a computer integrated bi-fuel spark ignition engine that has been retrofitted for two fuels namely, gasoline and compressed natural gas (CNG). The ignition point was optimised for CNG through the external device so that the maximum cylinder pressure occurred at similar as gasoline fuel such as between 10 to 10.50 deg crank angles after top dead centre (TDC). The used engine is a 4-cylinder spark ignition engine that has been operated with steady state condition using engine operating software and data acquisition system called CADET6. An eddy current dynamometer was used to measure engine performance characteristics such as engine brake power and fuel consumption and to give load on engine during measuring emission characteristics. Bosch and Bacharach exhaust gas analysers were used to measure emissions gases such as CO, HC and NOx. The performance test was done with full throttle condition and corresponding air-fuel (AFR) was evaluated. The emissions test was done with fixed load condition for both the fuels. The results show that CNG reduces 15% brake power with 15% to 18% reduction in specific fuel consumption (SFC) as compared to gasoline fuel. This is mainly due to the gases nature of CNG fuel. The emissions results show that CNG reduces CO and HC emissions but increases NOx emissions. The details about the emissions and performance results with three way catalytic (TWC) converter have been presented and discussed. The results of this experiment will be used to develop of new dedicated natural gas engines. © 2005 Taylor & Francis Group, LLC.