生物柴油发动机进气道模拟与优化

针对DK4柴油机改为燃用生物柴油后出现混合气均匀度较差等问题，本文通过稳流试验和数值模拟的方式，结合均匀试验设计法，在稳态工况下，在进气道前端加装不同结构参数的导流叶片，研究了其对发动机流量系数和涡流比的影响，选择了最佳模型，并对比了瞬态工况下原进气道与优化后的进气道涡流比、累计进气质量和排放特性。结果表明:稳态工况下，优化后的进气道较原进气道平均涡流比增加了24.79%，缸内流量系数提升了1.17%；瞬态工况下，优化后的进气道涡流比整体提高9.46%，累计进气质量增加了7.02%；缸内温度和压力均提高，NOx排放平均升高4.4%，soot排放降低9.9%。可见优化后的进气道有效改善混合气形成，降低生物柴油发动机颗粒排放。

Simulation and Optimization of Intake Port of Biodiesel Engine

In order to solve the problems such as poor mixture uniformity after DK4 diesel engine was changed to use biodiesel, In this paper, Through steady flow test and numerical simulation, combined with uniform experimental design method, under the steady-state working conditions, guide vanes with different structural parameters were installed at the front of the intake port, and their effects on the engine flow coefficient and swirl ratio were studied, and the best model was selected, and the swirl ratio, cumulative intake quality and emission characteristics of the original intake port and the optimized intake port under transient working conditions were compared. The results reveal that under the steady-state working conditions, the average swirl ratio of the optimized intake port was increased by 24.7% compared with the original intake port, and the flow coefficient in the cylinder was increased by 1.17%. Under the transient conditions, the vortex ratio of the optimized intake port was increased by 9.46% and the cumulative intake quality was increased by 7.02%. Cylinder temperature and pressure were increased, with NOx emissions was increased by an average of 4.4% and soot emissions was reduced by 9.9%. It can be seen that the optimized intake tract effectively improves the formation of mixture and reduces the soot emission of biodiesel engines.