Stall Inception in a Boundary Layer Ingesting Fan
Stall Inception in a Boundary Layer Ingesting Fan
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DOI：
10.1115/gt2015-43025
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发表时间：
2015-06
期刊：
影响因子：
--
通讯作者：
D. Perović;C. Hall;E. Gunn
中科院分区：
文献类型：
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作者：
D. Perović;C. Hall;E. Gunn
与吊舱式涡扇发动机相比，采用边界层进气（BLI）的喷气发动机可以显著降低飞机燃油消耗。然而，发动机风扇必须在严重的进气道扭曲下连续运行，这将降低稳定性。本文对一种低速钻机风机进行了实验研究，该风机的进气存在bl型畸变。在失速期间，在多个位置进行了非定常套管静压测量。在接近失速的工作点，在转子入口和出口也进行了稳态、全环空区域穿越。发现BLI引起的稳定性降低很小。研究发现，在无刷工况下，尽管存在转子工作点超出净流稳定边界的局部区域，风机仍能稳定运行。由于上游速度和旋流不均匀，在施加b.i型畸变时，所测转子入射角在环空周围发生变化。失速前的非定常机匣压力波动幅值与转子攻角的周向变化相关，表明转子攻角是影响流动扰动产生和发展的关键变量。在高发生率的区域，类似于局部流动分离的扰动被启动。然而，在低发生率或负发生率的区域，任何扰动都会迅速衰减。当高发生率区域足够广泛，足以承受可以在整个环空传播的干扰时，发生BLI的完全旋转失速。
Jet engines with boundary layer ingestion (BLI) could offer significant reductions in aircraft fuel burn compared with podded turbofans. However, the engine fans must run continuously with severe inlet distortion, which is known to reduce stability. In this paper, an experimental study has been completed on a low-speed rig fan operating with a BLI-type inlet distortion. Unsteady casing static pressure measurements have been made at multiple locations during stall events. Steady-state, full-annulus area traverses have also been performed at rotor inlet and exit at a near-stall operating point. The reduction in stability caused by BLI is found to be small. It is found that with BLI the fan can operate stably despite the presence of localized regions where the rotor operating point lies beyond the stability boundary measured in clean flow. With the BLI-type distortion applied, the measured rotor incidence varies around the annulus due to nonuniform upstream velocity and swirl. The measured amplitude of unsteady casing pressure fluctuations just prior to stall is found to correlate with the circumferential variation of rotor incidence, suggesting that rotor incidence is a key variable affecting the creation and growth of flow disturbances. In regions of high incidence, disturbances resembling local flow separations are initiated. However, in regions of low or negative incidence, any disturbances decay rapidly. Full rotating stall with BLI occurs when high incidence regions are widespread enough to sustain disturbances which can propagate around the entire annulus.