王达，晁岳栋，邓俊，杨陈，沈源，李理光.高压缩比活塞顶形状对湍流动能和缸内气流的影响[J].内燃机工程,2019,40(3):56-64.
高压缩比活塞顶形状对湍流动能和缸内气流的影响
Effects of High Compression Raito Piston Geometry on Turbulence Kinetic Energy and Air Flow in Cylinder
DOI：10.13949/j.cnki.nrjgc.2019.03.008
关键词:高压缩比  湍流动能  气流  活塞形状  滚流
Key Words:high compression ratio  turbulence kinetic energy  air flow  piston crown geometry  tumble
基金项目:
作者单位
王达，晁岳栋，邓俊，杨陈，沈源，李理光 1.同济大学 汽车学院，上海 200092； 2.吉利动力总成研究院,宁波 315336； 3.同济大学 中德学院，上海 200092 
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摘要:基于一台排量1.0 L的小型涡轮增压直喷汽油机，研究了压缩比、活塞形状和结构尺寸对缸内气流和湍流动能的影响。结果显示，随着压缩比的提高，缸内滚流在压缩过程中减弱，压缩末期的湍流动能减小，压缩比16.0的活塞在压缩末期的湍流动能大约为压缩比9.6活塞的27%。而对于活塞形状来说，较大尺寸的球面凹坑形状有利于压缩末期湍流动能的保持，而不规则的活塞会使得压缩末期的湍流动能下降41%。凹坑的尺寸存在一个最佳值，凹坑深度过浅或过深都会降低缸内湍流动能。选择压缩比为12.0且湍流动能最高的活塞加工并试验，基于4种不同形状的活塞和最佳油耗的工况分析燃烧特性，结果显示随着工况的改变，缸内湍流动能的峰值和相位会改变，但结构对湍流动能影响的优劣基本不变。火焰扩散方向为缸内湍流动能较大的位置，缸内平均湍流动能越大，火焰传播越快，燃烧特性越好。
Abstract:Based on a 1.0 L turbocharged gasoline direct injection(GDI) engine, an engine model for 3D numerical simulation was set up and verified by the tested pressures in cylinder. The effects of different compression ratios(CR), different geometries and different structure sizes of piston on air flow in cylinder and turbulence kinetic energy(TKE) were simulated with the model at full throttle characteristics condition. The result shows that with the increase of CR, tumble becomes weak in compression process and TKE is reduced at the end of compression. TKE of CR 16.0 is 27% of that of CR 9.6. A relative larger bowl shape benefits the maintaining of higher TKE at the end of compression, and irregular shapes will reduce TKE by 41%. There exists the best structure size of the bowl, and too deep and too shallow pit will reduce TKE. In order to test the effect of the design of high compression ratio, the piston of CR 12.0 with the highest TKE was manufactured and tested at the lowest fuel consumption condition. Meanwhile, the simulation model was further verified. The effect of the piston on air flow in cylinder and TKE at different conditions was simulated, and the combustion characteristics of four CR 12.0 pistons with different bowl shapes were studied with the model at the lowest fuel consumption condition. The results show that the peak and phase of TKE change with the condition, but the effect of the piston top geometry on TKE has not changed, whether it is good or bad. Flame spreads in the direction of high TKE. The higher the TKE, the higher the flame spreading velocity and the better the combustion.
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