Numerical study of a two-stage transonic fan dynamic characteristics in transient processes

Abstract The transient performance of aero-engine during acceleration and deceleration processes has a significant effect on the maneuverability of the aircraft. The dynamic characteristics of the fan/compressor component during rapid changes in engine speed, inlet flow distortion, and back pressure fluctuation can significantly affect the stability and efficiency of the engine. The dynamic characteristics of a two-stage transonic fan during acceleration-deceleration processes combined with variable back pressure are investigated based on three-dimensional unsteady simulations of a single passage model. The numerical results show that the dynamic operating point does not move along the constant corrected speed line when the outlet is specified as a variable back pressure at the designed rotation speed, and the mass flow rate at the inlet presents a hysteresis induced by the separation flow that periodically appears in the second rotor passage. In the acceleration-deceleration processes between 95% to 100% rotation speed, the transient operating points also show a remarkable hysteresis from the constant corrected speed line. And hysteresis is exacerbated by increasing the rate of acceleration-deceleration processes or coupling with variable back pressure.