Conference paper ASME GT2014-26320, Düsseldorf, Germany
U. Siller, G. Kröger, T. Moser, S. Hediger
Year of publication: 2014
This paper describes the design and multi-disciplinary optimization of a two stage axial turbine of small scale turboshaft engine with a power output of 80kW. The two stage turbine concept includes a high pressure part to power the compressor and a low pressure part with constant rotational speed for shaft power. The paper builds up on the compressor design of the first part of the publication und focuses on a detailed presentation of the optimization setup and process.
For the automated geometry generation in the optimization process, the profile and meridional parametrization strategy is explained. Both, the high and low pressure stages are optimized in one combined setup to include stage interaction. The 3D blade generation process for the two stages requires an overall number of 150 free design parameters to be handled during the optimization. The numerical evaluation of members in the optimization uses a process considering aerodynamics as well as static and dynamic (Campbell diagram) machanics. For the CFD setup the inlet boundary conditons are calculated in a cycle estimation with the results of the compressor design from the first part of the publication. The outflow boundary condition however is set by an exit diffusor model which has been specifically implented in the flow solver.
Along with the optimization setup, managing the different optimization phases is illustrated. Finally, a detailed aerodynamic assessment of the chosen turbine geometry and a discussion on the performace maps are carried out. Overall the publication illustrates a highly complex optimization that is successful both in final results and with respect to industry competitive timeframe and given computing capacity. Well adapted design and analysis processes play a key role in this challanging task.
The prototype test of the small scale turboshaft engine is scheduled in 2014.