Effects of leading edge profiles on flow behavior and performance of supercritical CO2 centrifugal compressor

Abstract

The supercritical carbon dioxide (sCO2) Brayton cycle is considered one of the promising power cycles. Centrifugal compressors are the core equipment of sCO2 systems. The inlet condition of compressors is near the critical point of CO2, which makes the flow in compressors become more complex and has the risk of condensation. To improve the flow behavior at the leading edge (LE) of the blade, a method of correcting the LE profiles (long-short axis ratio) of the blade was proposed. The cause of condensation at the LE of the blade is analyzed by numerical simulation and the effects of the LE profiles on the flow behavior in the impeller passage and the performance of the compressor. The results show that the suction peak on the LE suction side is changed under different working conditions. With the increase of the long-short axis ratio of the LE of blades, the suction peak at the LE is weakened. Under the design condition, the volume of the two-phase flow in the impeller passage with elliptical LE is 20% lower than that with arc LE. When the long-short axis ratio of the LE is 3∼6, the volume of the low-dryness flow decreases with the increase of the long-short axis ratio under the condition of the small flow rate. Under the design condition, the isentropic efficiency of the compressor with the largest long-short axis ratio of the LE increases by 1.411%, and the pressure ratio increases by 0.0353.