Axial turbines for aircraft engines and power plants have reached a very high level of development. Further improvements, in particular in terms of higher efficiency and reduced number of blades and stages, resulting in higher loads, are possible, but can only be achieved through a better understanding of the flow parameters and a closer connection between experiment and numerical design and simulation. An analysis of future demands from the industry and existing turbine research rigs shows that there appears a need for a powerful turbine test rig for aerodynamic experiments.
This paper deals with the development and built up of a new so called Next Generation Turbine Test Facility (NG-Turb) at the German Aerospace Center (DLR) in Göttingen. The NG-Turb is a closed-circuit, continuously running facility for aerodynamic turbine investigations, allowing independent variation of engine relevant Mach and Reynolds numbers. The flow medium (dry air) is driven by a 4-stage radial gear compressor with a high pressure ratio and a wide inlet volume flow range. In a first stage the NG-Turb test section will allow investigations on single shaft turbines up to 2½ stages. In a further expansion stage the NG-Turb will be equipped with a second independent shaft system, then enabling experiments with configurations of high and low (or intermediate) pressure turbines and in particular offering the possibility for investigations at counter rotating turbines. Secondary air for cooling investigations can be provided by auxiliary screw compressors. Mass flow through the Turbine is determined redundantly with an uncertainty of about ±0.3%, using well calibrated Venturi nozzles upstream and downstream of the test section.
The operation concept and main design features of the NG-Turb will be described and an overview of the applied standard measurement and data acquisition technics capturing efficiency, traverse data etc. will be given. Thermodynamic cycle calculations have been performed in order to simulate the flow circuit of the NG-Turb and to access whether turbine operating points can be driven within the performance map of the compressor system. Finally the calibration procedure for the Venturi nozzles, which has been conducted during the commissioning phase of the NG-Turb by applying a special calibration test section, is explained and some results will be shown.