An Experimental Comparison of Enriched Biogas and CNG on Dual Fuel Operation of a Diesel Engine

Abstract

In the present work CNG and enriched biogas (93% CH4 by vol.) have been experimentally compared for performance and emission characteristics in a dual fuel diesel engine. The diesel is used as the pilot fuel, which is directly injected into the engine cylinder. The CNG and biogas are used as the main fuels, which are inducted with the intake air in the intake manifold. The experimental observations are taken for steady state conditions at varying engine loads for maximum pilot fuel substitution conditions. The performance of the engine is evaluated based on energy and exergy analyses. The emission characteristics are shown for oxides of nitrogen (NOx), hydrocarbon (HC), carbon monoxide (CO) and smoke emissions. It was found that enriched biogas showed the performance similar to that with CNG, whereas slight variations in the emissions were observed. The exergy efficiencies of 27.8% and 26.9% were calculated for CNG and biogas dual fuel operations respectively at the full load. Similarly, maximum pilot fuel substitutions were found 73.4% and 71.4% for the above conditions respectively.