Improved Stall Recovery in “Electrified” Gas Turbine Engines

This study investigates the potential for stall control and recovery of “electrified” gas turbine engines that incorporate advanced electric generator/motor system capable of adding or reducing torque from the engine shaft. In parallel to the conventional stall recovery action, such as reducing fuel flow, electric motors are utilized to drive the engine shaft to accelerate, thus enhancing the stall recovery process. This idea is assessed using simulations of compressor flow during engine transients using a recently developed model capable of capturing the propagation of compression and expansion waves as well as shock waves in the compressor. A lumped-parameter combustor-turbine model is coupled with the aforementioned compressor flow model to simulate flow transients. This study considers a single-shaft gas turbine engine equipped with an electric motor that encounters stall at 75% speed during a cold acceleration. It is found that, compared to the traditional engine that plunges to surge, the “electrified” engine recovers from stall and accomplish the engine acceleration after receiving assistance from an electric motor providing mechanical power equivalent to 3% of the maximum dry thrust fuel combustion power. Such an electric power corresponds to the power required to drive the engine shaft to continue accelerating while the control logic reduces the TIT to recover stall.