A numerical study on the unsteady effect of axial spacing on the performance in a contra-rotating axial compressor

Abstract

Unsteady numerical simulations are conducted to investigate the unsteady effects of axial spacing on the performance of a contra-rotating axial compressor. The results show that the stage efficiency is dominant by unsteady effects between two rotors at lower axial gap ranges. As the axial spacing is increased, the variation of aerodynamic force is different for the two rotors. As a whole, the oscillation on the pressure surface is much stronger than that on the suction side in rotor1. For rotor2, however, the local maximum amplitude is just located at the blade leading edge, especially near the tip region. Additionally, the maximum amplitude of the pressure fluctuations generally decreases with an increase of axial spacing. The dominating frequency is different for monitors located at different positions and varies with the increasing of axial gaps. As the axial gap is increased, the potential effects decay in the process of propagating. Meanwhile, the incoming wakes are mixed out more sufficiently which would reduce the fluctuations at leading edge of rotor2. Therefore, a proper axial spacing should be chosen in the design process of a contra-rotating axial compressor considering both the performance and structure.

Flow behavior in a contra-rotating transonic axial compressor

“…Their findings indicated that by decreasing the axial spacing between the blade rows, an increase in efficiency and static pressure coefficient was achieved. Liu et al [7] results consistent with those of Smith [5] and Zak [6], investigated the effect of the axial spacing of the blade rows on the contra-rotating compressor.…”

Experimental study of the parameter effects on the flow and noise characteristics for a contra-rotating axial fan

“…Nouri et al [12] conducted an experimental investigation on the inverse design method of contra-rotating axial fans and the effects of varying the axial distance and rotational speed ratios on the overall performance were analyzed. Mao et al [13] investigated the effects of axial distance on the performance of a contra-rotating axial fan by unsteady numerical simulation. The results suggested that the unsteady effects dominated the flow behavior at smaller axial spacing ranges, while the variation of aerodynamic force for two rotors was different as the axial spacing increased.…”

A theory for rotating stall in contra-rotating fans

“…It was further shown that at design speed the axial spacing did not significantly affect the stage performance, but at offdesign speeds an optimum axial distance could be determined. A numerical study of unsteady effects of axial spacing in a contra-rotating compressor was conducted by Mao and Liu, 7 which emphasized the importance of a proper choice of the design axial distance between the two rotors. A transonic two-stage contra-rotating compressor was designed, built and tested by Wilcox and Wright 8 and Wilcox and Stevans.…”