J85 Surge Transient Simulation

A one-dimensional model is presented for simulating surge disturbance propagations throughout an entire turbojet engine. The predicted results using this model are presented for the surge transient flow phenomena and the unsteady compressor operating-point excursion during surge in a J85 turbojet engine. The unknown stalled compressor stage characteristics are represented by parameters whose range was determined through a parametric study. The predicted stalled characteristics showed faster responses and larger pressure-ratio deterioration compared to low-speed compressors. Surge hammer overpressures were found to have a triangular shape in the time-space (engine axis) domain. The mass flow through the compressor was found to approach zero in 10-20 ms, thus affecting the peak hammer overpressures at the intake duct and the temperature rise in the compressor. Different stall methods were found to result in different compressor operating-point excursions.