Abstract:

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.

Key words: alcohol, diffusion, fuel, pollution, operating range, combustion, emissions

摘要：

利用双直喷发动机试验平台开展了甲醇/柴油双直喷发动机运行范围及性能的试验研究。结果表明，甲醇在进气行程中喷射时，甲醇/柴油双直喷发动机的运行范围受两种情况限制：最大压升率超过0.8 MPa·（°）^-1时的粗暴燃烧、指示平均有效压力的循环变动超过5.0%时的不稳定燃烧。当甲醇在压缩行程后期喷射时，发动机运行范围仅受限于粗暴燃烧，最高甲醇替代率可达62.7%，指示热效率高达43.4%。甲醇喷射时刻对甲醇/柴油双直喷发动机燃烧和排放特性均有显著影响。当甲醇喷射时刻为-60°时，爆发压力和最大压升率均达到最高，着火延迟期最短，燃烧持续期最长，同时NO _x 排放最大，但CO、HC和soot排放最低，分别仅为8.5、1.3和0.06 g·（kW·h）^-1。

关键词: 醇, 扩散, 燃料, 污染, 运行范围, 燃烧, 排放