Aerodynamic analysis of a highly loaded compressor in semi-closed cycles using a throughflow method

This paper outlines the aerodynamic performance of a highly loaded 5-stage compressor in a conceptual semi-closed cycle. An in-house throughflow computation procedure that has been proven to be a powerful tool in aerodynamic analysis for modern compressors is applied to simulate the compressor. The influences of changes in physical properties of the working medium with varying ratios of exhaust CO2 recirculation are considered in the computation. A series of numerical simulations is conducted with two settings depending on whether the rotational speed is set to obey the criterion of similarity. For the identical non-dimensional speed parameter, the compressor can operate stably with pure CO2 as the working fluid. The distributions of aerodynamic parameters undergo no big differences under various CO2 contents; however, a somewhat little higher loss is observed for the 5th stage. When the absolute rotational speed is set according to the originally designed value, the compressor can bear a 25% CO2 content at the cost of a substantially narrowed working range, and a recirculation ratio of approximately 10% is a safe threshold value. The aerodynamic configuration also undergoes a notable redistribution given these circumstances; the load of the front stages is reduced, but the rear stages become the risk factors at near stall condition. This research reveals that from the compressor design point of view, a semi-closed cycle is feasible using existing technology and that compressor modifications are needed according to situational requirements. (c) 2015 Society of Chemical Industry and John Wiley & Sons, Ltd