Study On Road Rest Of Diesel/Methanol Compoud Combustion And Its Combustion Characteristics

With the reduction of petroleum resources and the increasingly stringent emission regulation, high efficient alternative fuels have become an important research direction of internal combustion engine. Methanol presents a promising prospect as an alternative fuel. This thesis encircle realization of applying the DMCC mode into vehicle, and further study on combustion character of diesel/methanol dual fuel is conducted according to the road test results.The mechanical part and circuit system were refitted for the vehicle working at the DMCC mode. After the test calibration of each road conditions, on the thruway condition, substitute percentage is 28.3%, substitute ratio is 1.36, and the fuel thermal efficiency increases by 10.26%; on the common road condition, substitute percentage is 24.2%, substitute ratio is 1.57, and the fuel thermal efficiency increases by 6.32%.According to the problems found in the road test, an intensive research was conducted concering on the combustion character of diesel/methanol dual fuel. The experimental results show that: the compound combustion of diesel/methanol dual fuel has the following characteristics, 1) Compared with the baseline engine, the form of heat release rate is changed significantly by the injected methanol, simultaneously the ignition point is delayed a lot. 2) The heat release rate is significantly accelerated, the maximum heat release rate increases and the original heat release rate rises sharply. Besides, the proportion of premixed combustion increased, the proportion of diffusion combustion decreases.In order to further understand the comprehensive properties of diesel/methanol dual fuel combustion, the power performance, emission performance and fuel economy were investigated on a 6-cylinder electronic unit pump engine. The experiments show that: 1) The power performance of the DMCC mode is better than baseline engine. 2) The combustion of diesel/methanol dual fuel had a high efficient fuel thermal efficiency zone. 3) The emission performance is imprved.In order to further understand the basis combustion character of diesel/methanol dual fuel, a study was carried out from the basic combustion and atomization characteristics respectively using a constant volume bomb and a visual methanol spray device. The basis combustion experiments show that, methanol atmosphere had a strong hysteresis to the ignition of diesel compared with pure air atmosphere, and the ignition time is delayed. Besides, the ignition time of diesel is delayed more with the increasing of the methanol content.The above study shows that, the diesel/methanol compound combustion mode has been successfully applied to vehicle, which can meet the needs of normal operation and obtain excellent fuel economy. The reasons of why DMCC mode can greatly improve the fuel combustion efficiency are that, under the compound combustion of diesel/methanol dual fuel, the form of heat release rate is significantly changed, simultaneously the ignition point is delayed and the trend of homogeneous charge compression ignition is enhanced. Besides the proportion of premixed combustion increases, while the proportion of diffusion combustion decreases, so the fuel combustion efficiency of engine is greatly improved.