A Methodology for Assessing Axial Compressor Stability with Inlet Temperature Ramp Distortion

Based on a small perturbation stability model for periodic flow, the effects of inlet total temperature ramp distortion on the axial compressor are investigated and the compressor stability is quantitatively evaluated. In the beginning, a small perturbation stability model for the periodic flow in compressors is proposed, referring to the governing equations of the Harmonic Balance Method. This stability model is validated on a single-stage low-speed compressor TA36 with uniform inlet flow. Then, the unsteady flow of TA36 with different inlet total temperature ramps and constant back pressure is simulated based on the Harmonic Balance Method. Based on these simulations, the compressor stability is analyzed using the proposed small perturbation model. Further, the Dynamic Mode Decomposition method is employed to accurately extract pressure oscillations. The two parameters of the temperature ramp, ramp rate and Strouhal number, are discussed in this paper. The results indicate the occurrence and extension of hysteresis loops in the rows, and a decrease in compressor stability with increasing ramp rate. Compressor performance is divided into two phases, stable and limit, based on the ramp rate. Furthermore, the model predictions suggest that a decrease in period length and an increase in Strouhal number lead to improved compressor stability. The DMD results imply that for compressors with inlet temperature ramp distortion, the increase of high-order modes and oscillations at the rotor tip is always the signal of decreasing stability.