叶片掠对跨声转子进口流动的影响

选择NASA Rotor 37跨声转子作为原型叶片,在叶片90%展高以上通过移动叶型基元的弦向位置构造叶尖掠特征,共有包括原型转子、2个前掠转子和2个后掠转子等5种不同叶型几何的算例.利用数值模拟软件计算得到5种转子的总体特性并获得三维流场.结果表明:叶尖前掠减小了叶片尖部进口的平均攻角,而后掠则使攻角增大.引入周向平均无黏动量方程,计算出由周向平均所产生的周向不均匀源项及径向平衡方程的各项数值,并对比其在5个转子进口的分布规律及其与攻角变化之间的关联.通过改变进口的流动平衡,叶尖前掠使轴向速度增大、周向速度减小,进而使得攻角减小;后掠则在叶尖起到了相反的效应.采用这种准三维方法研究了叶片掠对叶片进口流场的影响. 

Effect of blade sweep on inlet flow in transonic compressor rotors

NASA Rotor 37 was selected as a baseline blade. Sweep features at tip regions were formed by moving the airfoil sections above the 90% span along the chordwise direction. There were five cases including the baseline rotor, two forward rotor and backward sweep rotors in total. A numerical simulation softwave was used to simulate the five rotors and obtain the overall characteristics and three-dimensional (3-D) flow fields. The results indicated that the tip forward sweep resulted in a decrease of inlet averaged incidence, while the backward sweep caused the reverse consequence. A circumferentially averaged method was introduced to provide the circumferential fluctuation terms as well as values in the inviscid momentum equation. The distributions of the circumferential fluctuation terms in the radial inviscid momentum equation at the blade inlet were calculated for comparison between the five cases, and were analysed for incidence variation. Forward sweep at tip regions resulted in the increase of axial velocity and reduction of circumferential velocity, further reducing the incidence due to the change of flow equilibrium at blade inlet, while backward sweep caused an inverse effect in the same region. The effect of blade sweep on flow fields at blade inlet was studied from the quasi-3-D perspective.