Combustion and performance of heavy-duty diesel engines fuelled with dimethyl ether

Abstract

This experimental study was conducted with a heavy-duty diesel engine fuelled with dimethyl ether (DME). The combustion and emission characteristics of DME engine were investigated. The results show that the peaks of in-cylinder pressure, heat release rate (HRR), pressure rise rate (PRR), and mean gas temperature of the DME engine are lower than those of diesel engines. For DME engines, with increase in the engine load, the diagram of HRR varies from two peaks to a single peak. With increasing engine speed under the same mean effective pressure, the ignition timing is delayed, and the heat release centroid gradually moves away from the top death centre (TDC). The DME engine with an injector of six holes and a plunger of larger diameter exhibits a good performance owing to a faster diffusion combustion. With increase in fuel delivery advance angle at rated power, the ignition timing advances, and the centroid of the HRR is near the TDC. However, the peak of the HRR is at the same level. The results also show that higher torque and power can be achieved with DME than with diesel fuel operation at full load. At full load, the fuel consumption at low engine speeds with DME is lower than with diesel fuel, and nitrogen oxide emissions of the DME engine decrease markedly. Hydrocarbon emissions reduce while carbon monoxide emission slightly increases. The combustion of the DME engine is free of smoke throughout all the operating points. As DME is an oxygenated fuel, its combustion produces less carbon dioxide than that from diesel combustion. European stationary cycle emission test results show that the emissions from the DME engine are below the limits of the Euro 3 regulations.