Effects of Reynolds Number and Surface Roughness Magnitude and Location on Compressor Cascade Performance

Abstract

An experimental investigation has been conducted to characterize the influence of Reynolds number and surface roughness magnitude and location on compressor cascade performance. Flow field surveys have been conducted in a low-speed, linear compressor cascade. Pressure, velocity, and loss have been measured via a five-hole probe, pitot probe, and pressure taps on the blades. Four different roughness magnitudes, Ra values of 0.38 μm (polished), 1.70 μm (baseline), 2.03 μm (rough 1), and 2.89 μm (rough 2), have been tested. Furthermore, various roughness locations have been examined. In addition to the as manufactured (baseline) and entirely rough blade cases, blades with roughness covering the leading edge, pressure side, and 5%, 20%, 35%, 50%, and 100% of suction side from the leading edge have been studied. All of the tests have been carried out for Reynolds numbers ranging from 300,000 to 640,000. For Reynolds numbers under 500,000, the tested roughnesses do not significantly degrade compressor blade loading or loss. However, loss and blade loading become sensitive to roughness at Reynolds numbers above 550,000. Cascade performance is more sensitive to roughness on the suction side than pressure side. Furthermore, roughness on the aft 2/3 of suction side surface has a greater influence on loss. For a given roughness location, there exists a Reynolds number at which loss begins to significantly increase. Finally, increasing the roughness area on the suction surface from the leading edge reduces the Reynolds number at which the loss begins to increase.

Large-eddy simulation of 3-D corner separation in a linear compressor cascade

“…The main mechanisms of corner separations are: 11 (i) strong adverse pressure gradients, (ii) secondary flows within the passage, (iii) the mixing of the boundary layers on both the end-wall and the blade suction surface, and (iv) a possible horseshoe vortex (when the a) feng.gao@buaa.edu.cn b) jerome.boudet@ec-lyon.fr blade leading edge is thick). 12 Corner separations are also influenced by many parameters, such as compressor loading, 7 inflow boundary layers, 13 free-stream turbulence intensities, 14 clearance flows, 15 Reynolds number, 16 Mach number, 17 surface roughness, 16 and real blade geometries. 18 As corner separations can reduce the compressor efficiency and can lead to negative consequences, it is requested to control or reduce corner separations.…”

Prediction of the unsteady turbulent flow in an axial compressor stage. Part 2: Analysis of unsteady RANS and LES data

“…Previous works also reports that transition [4] as well as the level of losses [4,1] is sensitive to surface roughness. However, since the Reynolds number related to the test case considered in this paper is quite high (Re = 7 × 10 5 ), a low level of roughness (< 11µm) 1 should not influence the near wall flow. Indeed, transition in the present compressor should be controlled mainly by the free-stream turbulence, pressure gradient and periodic incoming wakes.…”

“…There are some indications in the literature that the effects of surface curvature, divergence / convergence effects, compressibility, and heat transfer in gas turbines are less significant on transition as compared to free-stream turbulence effects [12]. Previous works also reports that transition [4] as well as the level of losses [4,1] is sensitive to surface roughness. However, since the Reynolds number related to the test case considered in this paper is quite high (Re = 7 × 10 5 ), a low level of roughness (< 11µm) 1 should not influence the near wall flow.…”

Performance Metrics and Experimental Testing of Erosion-Resistant Compressor Blade Coatings

“…[11]. Initial average surface rough ness (Ravg) values for the bare, TiN-coated and CrAlTiN-coated upstream blades were: 1.17 pm, 1.34 pm, and 1.64 pm, respec tively.…”