Effects of Postinjection on Combustion and Soot Emission of Methanol and Diesel Dual-Fuel Based on an Optical Engine Investigation

The effects of postinjection on the performance of a diesel/methanol dual-fuel engine were achieved based on an optical engine. Methanol was injected into the intake duct, while diesel underwent a dual injection into the cylinder, comprising both the main injection and the postinjection. In this paper, two tests were conducted to investigate the impacts of the injection mass and timing of the postinjected diesel on the in-cylinder combustion process. First, an investigation was conducted into the effects of diesel postinjection mass on the combustion process. Second, the effects of the diesel postinjection timing on the combustion process were investigated. In both tests, the heat release from the injected fuel and the timing of the main injection stayed constant. The results indicated that as the mass of diesel postinjection increases, the cylinder pressure decreases and the combustion duration extends. When the timing of diesel postinjection is delayed, the two-stage heat release within the cylinder becomes more pronounced, significantly inhibiting soot formation in-cylinder. By employing suitable diesel postinjection mass and timing strategies, soot formation can be minimized while maintaining the engine’s thermal efficiency.