基于爆震的甲醇-柴油双燃料发动机掺烧比边界研究

Co-combustion ratio boundary of methanol-diesel dual-fuel engines based on knock

【目的】以一台电控共轨六缸柴油机改造的发动机为试验对象,以发生爆震为限制条件,研究甲醇-柴油双燃料燃烧下的掺烧比边界.【方法】通过对滞燃期变化的分析,发现甲醇-空气预混气发生均质压燃是甲醇-柴油双燃料燃烧爆震的重要诱因;利用回归分析,发现进气压力、排气温度及甲醇-空气预混气浓度对掺烧比边界有显著性影响.【结果】以边界掺烧比为因变量,得到排气温度及甲醇-空气预混气过量空气系数为自变量的线性模型,边界掺烧比=-0.1×排气温度-4.48×空气与甲醇预混气过量空气系数+101.897.【结论】甲醇-柴油双燃料发动机可利用排气温度、空气与甲醇预混气过量空气系数两个参数预测最大掺烧比,以实现掺烧比随工况的实时调整.

【Objective】With the confined condition,knock,the co-combustion ratio boundary of methanol-diesel dual-fuel combustion was studied based on a modified electronically controlled common rail 6-cylinder engine.【Method】By analyzing the ignition delay period,the conclusion could be arrived that the homogenous charge compression ignition of methanol-air mixture was a significant contributor to the knock of methanol-diesel dual-fuel combustion.By regression analysis,it could be reached that intake pressure,exhaust temperature and the concentration of methanol-air mixture had a significant influence on the boundary co-combustion ratio.【Result】A linear model was set up,which included the dependent variable of boundary co-combustion ratio and the independent variables of exhaust temperature and the excess air coefficient of methanol-air mixture：the maximum co-combustion ratio=-0.1×exhaust temperature-4.48×the excess air coefficient of methanol-air mixture ＋101.897.【Conclusion】The maximum co-combustion ratio could be predicted by exhaust temperature and the excess air coefficient of methanol-air mixture in the methanol-diesel dual fuel engines to realize the real-time modulation of the co-combustion ratios with the operation conditions.