Numerical studies on interactions between a centrifugal compressor and the back-propagated pressure waves originated from a pulse detonation combustor

Abstract

In order to investigate the influence of the back-propagated pressure waves originated from a pulse detonation combustor on the operating characteristics of the compressor in the pulse detonation turbine engine, a model consist of a centrifugal compressor and an isolation section which was usually utilized to decrease the peak value of the back-propagated pressure waves was set up. Numerical simulations were carried out to study the interactions between the centrifugal compressor and the back-propagated pressure waves under different operating conditions. The matching characteristics of the compressor under the influence of the back-propagated pressure waves were analyzed in a detonation cycle. The results showed that the back-propagated pressure waves would push the shock wave in the isolator towards the throat position, but the shock wave did not pass through the throat for the compressor corrected speed of n = 100% and n = 105%. For these two cases, the back-propagated pressure waves were completely isolated and the operating characteristics of the compressor were the same as those under the steady outlet conditions. For the corrected speed of n = 50% and n = 90%, the shock wave in the isolator section was pushed out of the throat and the supersonic flow in the isolator section was destroyed under the influence of the back-propagated pressure waves. The back-propagated pressure waves would propagate upstream into the compressor. Consequently, the instantaneous mass flow rate and the torque acting on the centrifugal impeller was decreased. The work required by the compressor was also reduced. The equivalent isentropic efficiency of the compressor was decreased. The separation or backflow in the compressor caused by the back-propagated pressure waves would results in an equivalent isentropic efficiency loss of 3.2% points for the case of n = 90% and 15.6% points for the case of n = 50%.

Spatial-Temporal evolution characteristics of pre-Stage-stall in a centrifugal compressor with a vaneless diffuser and a volute

“…The compressors are required to simultaneously meet the requirement of high efficiency, high-pressure ratio, and broad operating range. [1][2][3] The stable operating range of centrifugal compressors is confined by the unstable flow phenomenon of rotating stall 4 and surge, 5 which also deteriorates the efficiency and induces severe vibrations. 6 The surge, which should be practically avoided, is usually triggered by the stage stall.…”