Performance Assessment of a Recuperated Turboshaft Engine: A Multifuel Case

Abstract

The low cycle efficiency of simple cycle micro gas turbines is typically raised by the use of recuperators. The recuperated cycle allows for improved efficiency at low power-to-weight ratio, mainly due to the weight of the added heat exchanger. As weight is considered to be a key parameter for aeroengines, an analysis that addresses benefits and drawbacks of a more efficient, but heavier propulsion system design is required to be carried out. This paper assesses propulsion systems based on simple and recuperated cycle small gas turbine configurations, unusual in aviation, running with conventional jet fuel or hydrogen. An analytical model capable of modelling a turboshaft engine steady state design and off-design operation is developed. The specific fuel consumption of different engine arrangements is therefore calculated to evaluate the performance trade-off between the improved power plant fuel economy and its larger weight under a generic reference mission for a light helicopter. To enable a consistent mission analysis study of the hydrogen fueled rotorcraft, the weight of the tanks for liquid hydrogen storage is estimated according to a preliminary design model. The results obtained suggest that a hydrogen-fueled recuperated powerplant can shorten the flight time to reach the breakeven point, compared to a recuperated jet fuel powerplant of the same power rating.