Effects of Low Reynolds Number on Loss Characteristics in Transonic Axial Compressor

Abstract

A three-dimensional computation was conducted to understand effects of low Reynolds numbers on loss characteristics in a transonic axial compressor, Rotor 67. As a gas turbine becomes smaller and it operates at high altitude, the engine frequently operates under low Reynolds number conditions. This study found that large viscosity significantly affects the location and intensity of the passage shock, which moves toward the leading edge and has decreased intensity at low Reynolds number. This change greatly affects performance as well as internal flows, such as pressure distribution on the blade surface, tip leakage flow and separation. The total pressure ratio and adiabatic efficiency both decreased by about 3% with decreasing Reynolds number. At detailed analysis, the total pressure loss was subdivided into four loss categories such as profile loss, tip leakage loss, endwall loss and shock loss.

Effects of Low Reynolds Numbers on Performance of a One-Stage Axial Compressor

“…13) In this study, total pressure loss of the one-stage transonic compressor varies according to the ¹0.22 power of the Reynolds number. These results are in a good agreement with the results reported by Matsunuma,6) Choi et al 9) and Fielding. 13) In their results, total pressure loss in an axial turbomachinery is proportional to a power of Reynolds number between ¹0.35 and ¹0.20.…”

“…The flow separation and thick boundary layer on blade surfaces at a low Reynolds number caused a large loss in the wake, thereby making the overall loss increase. A more detailed description of the relation between total pressure loss and Reynolds number can be found in Choi et al 8,9) The difference in total pressure between Low Re and Ref.…”

“…Total pressure loss remains nearly constant when the Reynolds number is greater than the critical value and the loss increases rapidly below the critical value. Referring to Choi et al, 9) a transonic rotor also has a critical value of Reynolds number around 250,000. These two results imply that an axial compressor has a critical Reynolds number between 200,000 and 300,000, below which total pressure loss rises quickly.…”

“…In previous studies, Choi et al 8,9) analyzed the variation of each loss category depending on the Reynolds number in an axial compressor. Table 3 summarizes their results for total pressure loss variation in relation to the Reynolds number.…”

“…Recently, Choi et al 8,9) found, based on their numerical simulations, that an axial compressor might have a Reynolds number threshold between 200,000 and 300,000, below which the total pressure loss increases quickly. In these studies, the axial compressor consisted of a single rotor without a stator.…”