A Study of the Emissions of a Dual Fuel Engine Operating with Alternative Gaseous Fuels

Research on the combustion and performance of dual fuel stationary engines using natural gas and methane is found to be adequate in published literature. The emissions aspects, however, are less well investigated. Inadequacy is also noted in the case of published research works on biogas in dual fuel engines in respect of regulated emissions. One important pollutant which has not received much attention among researchers is the particulate matter (PM) for such applications. Though it is often claimed that PM emissions from gas-diesel dual fuel engines are much reduced, few works have been published to support this claim. The present study is intended to help fill the gap and all the regulated emissions (CO, CO₂, NO_x, UHC) including PM are measured for a Lister Petter direct injection stationary diesel engine modified for dual fuel applications. Two alternative gaseous fuels used in this study are natural gas and biogas. PM is measured by the conventional gravimetric method and PM physical structures are observed visually and are analyzed by scanning electron microscopy. Results are compared between the diesel and dual fuel operations and also between natural gas and biogas fueling for a particular engine operating condition. PM emission for dual fueling is found to be reduced by about 70% (on a mass basis) compared to diesel fueling at the same operating conditions. Also smaller and rounder particulate agglomerates are observed and measured for dual fueling as compared to diesel fueling.