Dual Fuel Methanol and Diesel Direct Injection HD Single Cylinder Engine Tests
Journal article, 2018
Laws concerning emissions from heavy duty (HD) internal combustion engines are becoming increasingly stringent. New engine technologies are needed to satisfy these new requirements and to reduce fossil fuel dependency. One way to achieve both objectives can be to partially replace fossil fuels with alternatives that are sustainable with respect to emissions of greenhouse gases, particulates and nitrogen oxides (NOx). A suitable candidate is methanol. The aim of the study presented here was to investigate the possible advantages of combusting methanol in a heavy duty Diesel engine. Those are, among others, lower particulate emissions and thereby bypassing the NOx-soot trade-off. Because of methanol's poor auto-ignition properties, Diesel was used as an igniting sources and both fuels were separately direct injected. Therefore, two separate standard common rail Diesel injection systems were used together with a newly designed cylinder head and adapted injection nozzles. This study serves as a proof-of-concept, demonstrating that methanol can successfully be used in a high pressure Diesel injection system. Additionally, the combustion properties of the dual fuel system were compared to those of pure Diesel with the same dual injection strategy. Methanol offered comparable combustion efficiencies to conventional Diesel with lower NOx and significantly lower soot emissions. A design of experiments study was performed to characterize the methanol-diesel system's behavior in detail at a single speed-load point. A sweet spot analysis showed potential for optimizing the given setup towards even higher indicated gross efficiency with very low soot and low NOx.