Title: Effect of Compressed Natural Gas Mixing on the Engine Performance and Emissions
Abstract: Cleaner air quality is becoming a global concern, thus to improve the fuel and combustion process is vital.In this paper, computational fluid dynamics (CFD) analysis software CFD-ACE is used to investigate the flow behavior of methane and air in a compressed natural gas (CNG)-air mixer to be implemented in a CNG-diesel dual-fuel stationary engine.The effect of the number of mixer holes on the mixture quality was evaluated.The results of the 3D CFD simulation showed that the 8-hole Venturi mixer gave superior performance compared to the 4-hole mixer.Further analysis was carried out on the 8-hole Venturi mixer to investigate the effect of engine speed on the mass flow rate of CNG and the equivalence air to fuel ratio (1/).The second half of the paper presents comparative performance results between a single cylinder research compression ignition (CI) engine fueled with a CNG-diesel system and a conventional CI engine fueled by conventional diesel.The engine was equipped with the simulated 8hole Venturi mixer.The result showed a significant reduction in exhaust gas emission components (NO x , CO and CO 2 ) from the CNG-diesel engine compared to the conventional diesel engine, i.e. the reduction rates were on average of 54%, 59% and 31% respectively.The average power output developed by the dual-fuel engine was 10% higher than the diesel over the power curve.