Numerical and Experimental Studies of Reynolds Number and Rotor-Stator Clocking Effect on Performance of a Highly-loaded Two-stage Compressor with 3.7 Total Pressure Ratio

摘要

The work presents the results of experimental and numerical investigations of Re number effect on gas-dynamic characteristics of a highly loaded two-stage compressor HPC-2, simulating the first two stages of the HPC for an advanced engine. The compressor has the following parameters [1-4]: Gcor=31.8 kg/s; π~*=3.7; H_T=0.421 The experimental study of HPC-2 is carried out at the CIAM's C-3 test facility when changing the Reynolds number by decreasing pressure at the inlet from 1 bar to 0.2 bar and changing the clocking position of stator rows at optimal points of performances at two rotational speeds (0.7 and 0.88). Tests of HPC-2 compressor show that a stepwise decrease of the inlet pressure from 1.0 to 0.7, 0.4, 0.2 bar (a decrease in Re number from 1785000 to 294000) leads to a smooth decrease in maximum compressor efficiency by 1% and a shift of compressor characteristics towards lower air flow rates (by 2%). The calculated values of Re effect on the compressor characteristics for the 3D flow model without reference to the laminar-turbulent boundary layer conversion point are much higher than the experimental values for efficiency and flow, and are 4% for max. efficiency, and 3% for air flow. Including γ - Reθ transition model into the computation shows lower negative effect of Re number on calculated parameters: 1.3% for max. efficiency and 0.65% for mass flow. The experimental studies of compressors for present-day engines show that unsteady processes play a key role in compressor efficiency and stability. One way to control unsteady flow in compressors is clocking effect [1-6]. Recently clocking effect of stators and rotors has been investigated in details using the HPC-2 two-stage compressor in H = 0; M = 0 conditions [6, 7]. The effect of Reynolds number on compressor characteristics is studied in this work for the HPC-2 compressor with account of the rotor and stator clocking effect. Tests of HPC-2 compressor show that a decrease in the inlet pressure and changes in Re number result in a more severe total clocking effect and is 0.5% in terms of efficiency under atmospheric conditions at the inlet and 1% with a decrease in the inlet pressure from atmospheric pressure down to 0.2 bar. Reynolds number influence on rotor clocking was studied numerically in this work.