Balanced use of recuperator in an MGT-powered eVTOL for extending cruise-stage flight time

Although recuperators are not widely used in micro gas turbines for aircraft due to the concern of added weight, modern design and manufacturing technologies are able to make recuperators both compact and efficient, which makes the situation worth another assessment. The presented research systematically investigates the pros and cons of adopting a recuperative micro gas turbine for eVTOL applications. The research takes a 30 kW micro gas turbine power chain as an example and develops a system model consisting of the gas turbine, a recuperator, the weight and loading of the eVTOL, propellers and motors. A Pareto-based optimisation strategy is developed to identify the flight-time-optimal balance between the mass of the recuperator and the mass of the fuel under different cruise-speed and payload conditions. Under the long-duration forward-flight conditions considered, compared with the simple-cycle configuration in which the recuperator mass is replaced by an equal mass of fuel, the optimised recuperated configuration increases the calculated flight time by approximately 10–15 % over a broad low-payload range, with a maximum absolute gain of about 1.3 h. These findings demonstrate that recuperated micro gas turbines have clear advantages over simple-cycle micro gas turbines for some eVTOL applications. A well-balanced recuperator can therefore extend the flight time while reducing fuel consumption and direct CO 2 emissions under favourable operating conditions.