中文摘要：

在一台4气门可视化光学发动机上，研究了可变气门升程下缸内气体流动特性。研究结果表明：发动机采用不同气门升程，在不同转速下，数值模拟的缸内流场分布与采用激光粒子图像技术测试而获得气流速度场结果吻合良好。发动机在采用最大气门升程为1．7mm的低气门升程型线下可以产生较强的湍流，尤其在进气行程，其湍流强度是发动机采用最大气门升程为6.8mm大气门升程曲线时的两倍。进气初期气门阀座处气流速度最高，且随气门升程的降低和转速的提高，气门阀座处气流的速度都有大幅上升；最大气门升程为1．7mm，发动机转速为960r／min时，气门阀座处最大速度达到了140m／s。在低气门升程下，压缩终了的湍动能最大值较高，且湍动能分布更加均匀。

英文摘要：

The in-cylinder flow characteristics under variable valve lift （VVL） were studied in a singlecylinder four-valve optical SI engine. The results show that, the in-cylinder flow fields by numerical simulation are in good agreement with the measurement from the particle image veloeimetry （PIV）. Using the low valve lift curve with maximum valve lift of 1.7 mm, strong turbulence can be generated, especially in the induction stroke. Turbulence intensity is doubled compared with that using the high valve lift curve with maximum valve lift of 6.8 mm. In the early induction stroke, the maximum flow velocity appears at the intake valve seats, and it increases substantially as valve lift is decreased and engine speed is increased. In the case of maximum valve lift of 1.7 mm and engine speed of 960 r/min, the maximum flow velocity at the intake valve seats reaches 140 m/s. At the end of the compression stroke, the low valve lift can generate higher in-cylinder maximum turbulent kinetic energy and more uniformed turbulent kinetic energy distribution.