甲醇喷射时刻对甲醇/柴油双直喷发动机性能的影响

The operating range and performance of a methanol/diesel dual direct injection engine were experimentally studied using a dual direct injection engine test platform. The results demonstrate that when methanol is injected during the intake stroke, the operating range of the methanol/diesel dual direct injection engine is restricted by rough combustion with the maximum pressure rise rate exceeding 0.8 MPa· (°) ⁻¹ and unstable combustion with the coefficient of variation of indicated mean effective pressure exceeding 5.0%. When methanol is injected in the late stage of the compression stroke, the engine’s operating range is only limited by rough combustion. Under this condition, the maximum methanol substitution rate can reach 62.7%, and the indicated thermal efficiency can be as high as 43.4%. The timing of methanol injection exerts a profound influence on the combustion and emission characteristics of a methanol/diesel dual direct injection engine. When the methanol injection timing is − 60°, both the peak pressure and the maximum pressure rise rate in the cylinder reach their highest values, the ignition delay period is the shortest, the combustion duration is maximized, and the NO_x emissions are at their peak. However, the CO, HC and soot emissions are minimized, amounting to only 8.5, 1.3 and 0.06 g·(kW·h)⁻¹ respectively.