The process of wet compression in an axial compressor is an intricate two-phase flow involving not only heat and mass transfer processes but also droplet breakup and even formation of discontinuous water film on the blade surface and then breaking into droplets. The implementation of practical boundary conditions for water droplets on the blade surface is the key to the proper numerical simulation of the wet compression process. In this paper, the droplets-wall interactions are analyzed using the theory of spray wall impingement through two computational models for an isolated transonic compressor rotor (NASA rotor 37). The Model #1, representing spread phenomenon, assumes that all droplets impacting on the blade are trapped in the water film and subsequently released from its trailing edge and enter the wake region with an equivalent mass flow but bigger in diameter and smaller in number. Whereas, the Model #2, representing splashing phenomenon, assumes that upon impacting on the blade, the droplets will breakup into many smaller ones. The three-dimensional flow simulation results of these two models are analyzed and compared in this paper. The trajectory of droplets for the spread phenomenon clearly showed formation of larger size droplets on the rotor blade’s suction surface near its trailing edge which broke-up into larger number of smaller size droplets. Whereas, in the case of splashing, droplets breakup into many smaller size droplets upon impacting on the blades. The three-dimensional flow field, examined through Mach number and temperature contours, showed that the evaporation was much larger around the blade’s tip region indicated by a larger temperature reduction. The examination of limiting streamlines clearly showed that the wet compression moved shockwave towards blade’s tip region and separation region and vortex region became weaker for a given amount of water injection and for both droplets-wall interaction models. For a given amount of injection flow and downstream of the separation line, the extent of flow reversal region in the spanwise direction and near the blade’s trailing edge are influenced by the type of droplet-wall interaction. Also, the extent of flow reversal region in the spanwise direction reduces with the decrease in the injected droplets size.
- International Gas Turbine Institute
Understanding Behavior of Water Droplets in a Transonic Compressor Rotor With Wet Compression
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Sun, L, Zheng, Q, Luo, M, Li, Y, & Bhargava, R. "Understanding Behavior of Water Droplets in a Transonic Compressor Rotor With Wet Compression." Proceedings of the ASME Turbo Expo 2010: Power for Land, Sea, and Air. Volume 5: Industrial and Cogeneration; Microturbines and Small Turbomachinery; Oil and Gas Applications; Wind Turbine Technology. Glasgow, UK. June 14–18, 2010. pp. 135-156. ASME. https://doi.org/10.1115/GT2010-23141
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