柴油机可变涡流进气流动的数值模拟研究

Numerical Simulation Study on Variable Swirl Intake Flow of Diesel Engine

为1台2.0L的4气门柴油机设计了可变涡流进气系统,利用三维CFD软件AVL-Fire分别对柴油机的3种气道型式的气体流动进行了数值模拟计算,得出了不同型式进气道的流通特性和涡流特性。提出了两种涡流控制阀方案,在切向和螺旋进气道分别设置旋转阀片进行调节,可以改变涡流比,并经比较研究选出了较优方案。研究结果表明,螺旋进气道在大气门升程下的流通能力优于切向进气道,但小气门升程下切向进气道流通能力较好,且产生涡流能力较强;双进气道由于气流的干涉会导致进气能量的损失,但涡流扭矩有所增加;涡流控制阀能在一定范围内改变进气涡流比,且设置在螺旋气道侧的方案具有更好的变涡流效果,能够保证较好的流通性和较大的涡流比变化范围,满足发动机不同工况对流通性和涡流强度的要求。

A variable swirl intake system was designed on a 2.0 L 4-valve diesel engine. The intake flows of three intake ports for diesel engine were simulated with the 3D AVL Fire software and their flow and swirl characteristics were acquired. Two schemes of swirl control valve were proposed, which set the rotary valve plate in tangential and spiral intake port respectively. Then the swirl ratio could be changed and a better scheme was selected after the comparison. The result shows that the flow characteristic of spiral intake port is better than that of tangential intake port for a lager valve lift. However, the opposite is true for a small valve lift and the stronger swirl produces. The double intake ports will lead to the loss of intake energy due to airflow interference, but the swirl torque increases. The swirl control valve can change the intake swirl ratio within a certain range and has the better effect of changing swirl when it is mounted on the side of spiral port, which ensures better flow charac- teristic and larger swirl ratio range that meet the engine flow and swirl requirements under different conditions.