可变气门升程对涡轮增压缸内直喷汽油机缸内流动特性的影响

采用数值模拟方法对不同最大进气门升程（MVL）下涡轮增压缸内直喷汽油机缸内气体的流动特性进行分析，以掌握变气门升程对缸内流动的影响规律．结果表明，MVL的减小使过进气门中心线的纵截面内的顺时针滚流增强。在120℃A时刻，MVL为7．7mm时截面内气体流动以逆时针滚流为主，而MVL为1．0mm时截面内气体流动以顺时针滚流为主；低MVL有利于进气初期缸内滚流比的提高，而在进气后期及压缩过程中，MVL为1．0mm时缸内滚流比明显低于MVL为7．7mm和4．0mm时的缸内滚流比；随着进气门升程的减小，湍流强度第一个峰值明显升高（MVL为7．7mm时峰值为0．54，而MVL为1．0mm时峰值达1．03），但小MVL条件下湍流强度衰减较快，在压缩末期3种MVL下的湍流强度差别较小．

Effects of Variable Valve Lift on Flow Characteristics of Turbocharged Gasoline Direct Injection Engine

In order to understand the effect of variable valve lift on in-cylinder flow, numerical simulation method was used to analyze the flow characteristics of in-cylinder air under different max valve lift （MVL） in a turbocharged gasoline direct injection （GDI）engine. The results show that, with the valve lift decreasing, the clockwise tumble on the cross-section through the axis of intake valve increased, and at 120° CA, the air flow is counter-clockwise large- scale tumble when MVL is 7.7 mm, while it is clockwise large-scale tumble when MVL is 1.0 mm; it can improve the tumble ratio at the beginning of intake process under low MVL condition, but at the end of intake process and compression process, the tumble ratio when MVL is 1.0 mm is significantly lower than that when MVL is 7.7 mm and 4.0 mm; with the MVL decreasing, the first peak of turbulence intensity significantly increased, with the peak value being 0.54 and 1.03 when MVL is 7.7 mm and 1.0 mm, respectively, while the decay rate is fast under low MVL condition, and at the end of compression the turbulence intensity is similar for three MVLs values.