Improving Hybrid Electric Propulsion Efficiency

Electrically driven turbine engine compressor and propulsion fans require a large stability margin against stall conditions to avoid unwanted performance issues while undergoing transients in operating conditions. This stability margin, while it maintains safe operation, also necessarily reduces the engine performance. Despite extensive research efforts, no viable alternative methods for reducing the operable stability margin and improving engine performance exist. This current innovation, originally conceived for stall prevention, offers a solution by utilizing a supercapacitor in line with an electric motor and motor controller to rapidly change a compressor or propulsor fan speed. The use of the supercapacitor enables rapid extraction, or addition of power, to prevent the fan from stalling. Additionally, this novel drive motor may be used for sensing stall event precursor signals by using the motor controller to detect variations in torque on the shaft caused by variance in loading on the blade system. The improved stall avoidance capabilities allow an engine fan to operate more efficiently, providing more thrust for a given frontal area, increasing operational range, reduced weight, and improved operational safety. The related patent is now available to license. Please note that NASA does not manufacture products itself for commercial sale. Propulsion system engineers at NASA’s Glenn Research Center have developed a novel method for increasing the efficiency of electrically driven propulsors by improving the range of operability against stall. Stall affects both compressor and propulsion fans and can be induced from a variety of operational conditions, often transient in nature. The incidence of stall conditions requires an operating margin between the stall point and the point of optimum operating efficiency, and typically, the compressor/propulsor fan operates at a lower efficiency point to increase the stall margin. Stall must be avoided to maintain thrust and in some cases to avoid catastrophic failure. While many researchers have explored stall control in the past, it remains a prevailing issue. This innovation integrates supercapacitors in the electric drive such that the drive can quickly modulate power to avoid stall. The electric motor system can also enable improved stall detection.