增压直喷汽油机扫气抑制爆震试验研究及模拟解析

Experiment Study and Numerical Analysis of Suppressing Knock with Scavenging for Turbocharged GDI Engine

针对增压缸内直喷汽油机(GDI)高负荷爆震问题进行研究,利用可变气门正时控制发动机扫气过程,在稀燃条件下分别对不同节气门开度和负荷的情况进行了不同VVT角度的试验。试验结果表明:扫气可抑制爆震并能提高发动机的低速扭矩;同时,基于一维热力循环模型的模拟解析发现,扫气主要通过降低缸内残余废气系数和降低进气门关闭时缸内气体温度实现抑制爆震;通过提高发动机的进气充量和抑制爆震后增大点火提前角来提高发动机的低速扭矩。

To research suppressing engine knock in high load with scavenging for turbocharged GDI engine, experiments were conducted under the conditions of lean mixture combustion and different throttle openings. The scavenging process was controlled using VVT technology. Experimental results indicate that scavenging can suppress the knock occurring and increase engine torque at low speed as well. Meanwhile, simulation analysis based on one-dimensional thermodynamic cycle model reveals that scavenging process decreases in-cylinder residual gas content and charge temperature at start of compression stroke, so engine knock is suppressed. By scavenging the volumatic efficiency increases and ignition timing can be advanced while the knock is suppressed, thus being beneficial to rising engine low speed torque.