掺烧比对P50/甲醇双燃料发动机燃烧与排放的影响

燃料富氧重整和双燃料燃烧模式是改善燃烧过程和降低颗粒物排放的重要方法。在一台四缸增压中冷的高压共轨柴油机上，采用进气道喷射甲醇、缸内喷射P50（50%体积比例柴油与50%体积比例PODE）的双燃料模式，研究掺混比对P50/甲醇双燃料发动机燃烧与排放特性的影响。研究结果表明：相比于纯柴油模式，P50及P50/甲醇双燃料燃烧模式均可同时降低NO_x与PM排放；与P50相比，在P50/甲醇双燃料模式下，随着甲醇掺烧比的增大，滞燃期延长、燃烧持续期缩短、峰值放热率增大；小负荷时，峰值缸内压力、峰值压力升高率和峰值燃烧温度降低；在中高负荷，峰值缸内压力、峰值压力升高率和峰值燃烧温度升高；NO_x排放逐渐降低；中等负荷下，颗粒物数浓度和体积浓度降低；大负荷下，颗粒物数浓度和体积浓度增加，但是远低于柴油；P50/甲醇双燃料发动机具有良好的减排效果。

Effect of Methanol Ratio on Combustion and Emissions of Dual-fuel P50/methanol Engine

Fuel reforming using intramolecular oxygen and dual-fuel combustion modes is an important method for improving combustion and reducing particulate emissions. In this study, the influence of the substitution ratio on the combustion and emission characteristics of a dual-fuel engine was studied on a four-cylinder supercharged and intercooled high-pressure common rail diesel engine with methanol injection in the inlet and P50 (50% volume ratio diesel and 50% volume ratio PODE) injection in the cylinder. The research results show that, compared with diesel, both P50 and P50/methanol dual-fuel engines can decrease NO_x and PM emissions simultaneously. Compared with P50, with an increase in the methanol blending ratio, the P50/methanol dual-fuel prolongs the ignition delay, shortens the combustion duration, and increases the peak heat release rate; at low loads, the peak in-cylinder pressure, peak pressure increase rate, and peak combustion temperature decrease. At medium and high loads, the peak in-cylinder pressure, peak pressure increase rate, and peak combustion temperature increase; moreover, the NO_x emissions decrease. At medium loads, the number and volume concentrations of PM decrease, and, at high loads, those of PM increase but are far lower than those of diesel. The results prove that the P50/methanol dual-fuel engine has a good emission reduction effect.