柴油机瞬态工况下燃烧和排放特性的研究

Based on eddy currency dynamometer a set of control and measurement system for diesel engines under transient operating conditions was developed. Repeatable transient operating modes had been realized，real-time parameters had been measured and recorded by this system. The emission characteristic and the combustion process of diesel engine under transient operating conditions were researched. In this project some potential technologies for improving the diesel's performance under transient conditions were studied. Some key conclusions showed by test results can be pointed out respectively in emission, combustion process and performance improvement. .Emission test results show some conclusions as follow. The response delay of even combustion temperature and air intake, the over-fuelling of fuel supply under transient operating conditions are important factors for PM emission and smoke opacity increasing. Gaseous pollutant is insensitive to the operating transient rate, but the trade-off between NOx and PM emission still exists. The formation of polycyclic aromatic hydrocarbons (PAHs) is directly correlated with the lack-oxygen combustion..Combustion process analysis presents some significant characteristics. With the transient rate increasing combustion duration prolongs, combustion start point delays, diffusion combustion fraction increases, maximal even combustion temperature become higher and the corresponding crank angle delays, which make the combustion process deteriorated. The prolonged combustion duration and increased diffusion combustion fraction are important factors for PM emission and smoke opacity increasing under higher transient rate operating conditions..Some opinions have been pointed out in transient performance improving study. Full load air-fuel ratio is the most important factor for transient performance. In order to gain better performance the calibration of full load air-fuel ratio should make allowance for the deterioration of transient conditions. The well matched VNT system can increase the power out-put, improve the emission behavior and economical efficiency. Supplying some highly-compressed air into exhaust manifold can change one less air intake quasi-balance state of the turbo charge system into another balance state with more air intake, which makes the smoke opacity of full load conditions under low speed decrease by 50%. Thus, the emission behavior under transient operating conditions can be greatly improved by this technology..

利用瞬态测功机等测试手段对柴油机瞬态工况下的燃烧和排放特性进行实验研究。找出柴油机瞬态工况直的燃烧和排放特性相对于稳态工况下的燃烧与排放特性的变化关系，分析造成这种变化的原因及主要影响因素，探讨校正的方法，为实现柴油机瞬态工况下高效低污染燃烧提供理论依据。