Effect of CNG Heating Value Variations on Emissions Characteristics in a Diesel-CNG Dual-Fuel Engine

Abstract

-In this paper, purpose of study is emissions characteristics according to effects of heating value variations of CNG fuel in a dual-fuel engine fueled by diesel and natural gas. For heating value variation of CNG fuel, nitrogen gas was mixed with pure CNG fuel. So the higher heating value was changed from 10,400 kcal/N㎥ to 9,400 kcal/N㎥. Under one condition of CNG substitution rate was fixed at 80%, diesel fuel was injected at a fixed injection timing of 16 CAD BTDC and fuel pressure was also fixed at 110 MPa. The condition of tested engine was 1800 rpm and 500Nm. Emissions were sampled in exhaust pipe was located at downstream turbocharger. As a result, emissions characteristics were checked in heating value variations of CNG fuel with mixed nitrogen gas THC, CH4 and CO emissions decreased and NOx and CO2 increased.