Today’s UAV helicopter industry faces a lack of highly reliable, SFC optimized turboshaft engines in the 40kW to 100kW class, resulting in a significant drawback for the overall flight envelope and the system availability of these aircraft. This paper describes the design process for a turboshaft engine with a shaft power output of about 80kW. A thermodynamic cycle model is derived from the flight envelope of the Swiss UAV NEO S-350 helicopter drone. Different compressor configurations are analysed and discussed with regard to the power output and SFC of the engine as well as to manufactural constraints. Combining a high flow density with a high isentropic efficiency and pressure ratio, a three stage compressor configuration was selected. The design is based on two axial front stages with a total pressure ratio of 1.55 and 1.45, respectively, and a diagonal last stage with a total pressure ratio of 2.8. Finally, the aero-mechanical design and optimization process of the compressor is depicted and the manufactural process is described. The engine prototype is expected to be tested the first time in 2014.

Aero-mechanical design of the turbine section of a small scale turboshaft engine is presented in this paper. A single stage high-pressure turbine (HPT) and the power turbine stage (PT), have been designed by means of automated optimization. This study demonstrates how multi-disciplinary optimization can be used effectively in today’s industrial development cycles with respect to timeframe and computational resources. Both, the aerodynamic performance and the mechanical blade behavior were subject to the optimization in a very high dimensional design space expressed by well above 100 free design parameters for the annular duct and the bladings of two axial stages. In the first part, this paper describes the design task and constraints in order to meet the requested thermodynamic cycle performance and fabricational requirements. In the second part, the optimization strategy is explained with focus on geometry parameterization, simulation setups for flow and structural analysis and acceleration techniques for the optimization itself. Finally, a very promising resulting design is reviewed in terms of a detailed aerodynamic and mechanical assessment and regarding to the overall engine concept. This work contributes to the development of a highly efficient, light-weight propulsion system powering, beside a wide range of other possible applications, for example small aerial systems such as helicopter drones. The engine prototype is expected to be tested the first time in 2014.