超高压喷射条件下非常态燃油的缸内燃烧排放特性研究

摘要

In order to improve the combustion and emission performance of high power diesel engine, the super-high fuel injection pressure more than 180MPa was proposed. The three-dimensional geometric model including combustion chamber and intake duct was established. The dynamic grid division of the simulation model was completed on the FIRE software. The calculation results of the internal flow field of the nozzle were used as the boundary to simulate the combus-tion process. The effects of the physical parameters of fuel and nozzle parameters on the combustion and emission character-istics of diesel engine were analyzed. The results show that when the physical parameters change, the cavitation effect of nozzle is enhanced, which is helpful to the oil beam to obtain good initial broken state. The atomization effect is improved, and the combustion process in the cylinder become more fully; When the nozzle diameter increases, the initial turbulent kin-etic energy increases, the range of fuel becomes larger. The fuel injection duration is shorter, and the later emission concen-tration is small; With the fuel injection angle increases, the fuel and air mixture in the cylinder becomes more uniform, and the combustion performance is further enhanced.%以改善大功率柴油机的燃烧与排放性能为目标，创新性地提出180 MPa 以上的超高燃油喷射压力。建立包括进气道和燃烧室在内的三维几何模型，利用 AVL FIRE 软件对仿真模型进行动网格划分，将燃油喷射系统的喷嘴内流场计算结果作为边界条件对燃烧过程进行仿真计算，分析燃油物性参数的变化以及喷嘴参数对柴油机燃烧排放性能的影响。结果表明：当燃油的物性参数发生变化之后，喷孔内部空化效应的增强有助于油束获得良好的初始破碎状态，雾化效果好，缸内燃烧过程进行得更加充分；当喷孔直径增大时，油滴初始湍动能增强，运动发展范围较大，喷油持续期短，后期排放物浓度小；随着喷射夹角增大，缸内燃油与空气混合得更加均匀，燃烧性能进一步提高。