Parallel Hybrid Propulsion & Secondary Power System Architecture Exploration and Evaluation

The parallel hybrid turbofan propulsion (PHTF) system, with a high and low spool connected motor/generator, applied to a single aisle aircraft, has been study extensively and been shown to provide both gas turbine level and aircraft level benefits. With significant electrification of the propulsion system, the degree of subsystem electrification should also be considered. Thus this current study focuses on the PHTF, considering not only the PHTF operating modes but also the secondary power subsystems (electric, hydraulic, and pneumatic) which interface with the propulsion system. Secondary power subsystem options range from hydraulic or electric for actuation to pneumatic or electric for the environmental control system. Each combination has been explored and evaluated within the UTRC aircraft systems integrated model (ASIM) - architecture exploration and evaluation (AEE) framework to identify the aircraft subsystem architecture that best complements the preferred hybrid propulsion system, where the hybrid propulsion system encompasses low and high spool machine size, usage scenario, and boost power source. Energy cost reduction and technology risk are evaluated for each design space architecture. The results show that a mild PHTF, using a low level of stored electric energy is preferred with a combination of electric and hydraulic actuation, electric wing anti-ice, and electric engine accessories. A bleed and electric based pneumatic system, each pared with an ECS optimized for the type of pneumatic system show similar energy cost performance.