In this paper, experiments are performed to measure and demonstrate the whole throttling process from the steady operating state to stall inception with water ingestion in a low speed axial compressor. A transparent casing is used to visualize the water distribution on the casing. Two types of nozzles are used, giving the average droplets diameters of 35 μm and 90 μm, respectively. Six different water mass flow rates are tested, ranging from 0.064% to 2.05% compared to the reference airflow rate. The compressor performance curves change significantly as the ingested water flow rate. Small water flow rates even improve the performance while the middle water flow rates decrease it. For large water flow rates, the pressure rise coefficient drops rapidly and becomes “flat” at low airflow rate but the stall margin is extended much further into the low airflow rate region. To visualize the whole stall evolution process, photos and digital videos are both taken through transparent casing and record the patterns of the water distribution on the casing. Dynamic casing static pressure is also measured at the same time. Due to the centrifugal force acting on the water droplets, the water film on the casing along the tangential direction is observed in photos and videos. The edges of water film can be identified, and the back edge is believed to separate the incoming flow and the tip leakage flow. As the compressor is throttled to smaller flow rates yet still away from the stall limit, this interface moves forwards and becomes fluctuating which can be visualized with bare eyes. The fluctuation becomes more and more violent until the water film suddenly spills out of the leading edge, and thus the stall happens. As the water ingestion rate increases, the film gets wider and thicker, and even exceeds the leading edge before stall inception. Unsteady casing static pressure is also measured. The increased power spectrum density of pressure signals in frequency domain is found and believed to might be related with the water film fluctuation observed on the compressor casing. The phenomena observed in photos and videos provide interesting information of the flow in the compressor and deserve further research.
Measurements and Visualization of Process From Steady State to Stall in an Axial Compressor With Water Ingestion
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Liu, L, Zhang, H, Li, J, Yu, C, Lin, F, & Nie, C. "Measurements and Visualization of Process From Steady State to Stall in an Axial Compressor With Water Ingestion." Proceedings of the ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. Volume 6C: Turbomachinery. San Antonio, Texas, USA. June 3–7, 2013. V06CT42A032. ASME. https://doi.org/10.1115/GT2013-95352
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