轴向间距对矿用旋风机旋转失速性能的影响

Effect of axial spacing on rotating stall performance of FBCDZ-10-No20 contra-rotating fan

矿用对旋风机在小流量工况运行时极易出现旋转失速现象,严重影响其运行稳定性。采用SST k-ω湍流模型,对FBCDZ-10-No20型对旋风机在5种轴向间距下全流道内的非定常流动进行数值模拟,研究了轴向间距对矿用对旋风机失速过程的影响,揭示了不同轴向间距时的失速起始与发展机理。结果表明:轴向间距对失速起始扰动的首发位置、表现形式和发展过程都具有显著影响。对于70、100 mm两种轴向间距,失速起始扰动均首发于前级叶顶,随后在两级叶轮之间的动−动干涉作用下,后级叶顶也出现失速起始扰动,但与70 mm的轴向间距相比,当轴向间距为100 mm时,动−动干涉效应相对较弱,使得后级出现失速起始扰动需要更长的时间。对于140、170、225 mm三种轴向间距,失速起始扰动均是首先发生在后级叶根区域,不同的是140 mm间距时,前级叶顶泄漏流不能完全随主流流出通道,而是形成了局部叶顶堵塞区;而对于170、225 mm两种间距,前级叶顶则几乎没有堵塞区,最终仅在后级形成了成熟的失速涡团。随着轴向间距的增大,由前级叶顶泄漏流发生前缘溢流及尾缘反流形成的堵塞区逐渐缩小,而由后级叶根吸力面径向涡流形成的堵塞区则逐渐增大,当前级叶顶泄漏流无法形成堵塞区时,失速类型就由前级叶顶泄漏流诱发的“突尖型”转变为由后级叶根径向涡流诱发的“局部喘振型”。

Mining contra-rotating fan are prone to rotational stall when it operates at low flow rates,which seriously affects the operational stability.The unsteady flow in the full flow passage of a FBCDZ-10-No20 contra-rotating fan at five axial spacings was numerically simulated by using the SST k-ωturbulence model.The effect of axial spacing on the stall process of contra-rotating fan was studied,and the mechanism of stall inception and development at different axial spacings was revealed.The results shown that the axial spacing had a significant influence on the initial position,type and development of stall inception.For the axial spacings of 70 mm and 100 mm,the stall inception first occurred at the tip of the front stage,and subsequently appeared at the tip of the rear stage due to the rotor-rotor interaction between the two stages.However,compared with the axial spacing of 70 mm,the rotor-rotor interaction at the axial spacing of 100 mm was relatively weak,making it take longer for a stall inception to occur in the rear stage.For all three axial spacings of 140 mm,170 mm and 225 mm,the stall inception occurred first in the root of rear stage.The difference was that for the axial spacing of 140 mm,the leakage flow at the tip of the front stage cannot completely flow out of the channel with the main flow,and a localized tip blockage area was formed.However,for both spacings of 170 mm and 225 mm,there was almost no blockage area at the tip of the front stage,and eventually only mature stall vortices formed in the rear stage.With the increase of the axial spacing,the blockage area formed by both the leading edge overflow and the trailing edge reverse flow those originated from the leakage flow at the tip of the front stage gradually reduced.In contrast,the blockage area formed by the radial vortex on the suction surface near the root of the rear stage gradually increased.When the leakage flow at the tip of the front stage failed to form blockage area,the stall type changed from the“spike type”induced by the tip leakage flow at the front stage to the“localized surge type”induced by the radial vortex flow at the root of the rear stage.