Jens Ortmanns

An Experimental Investigation of a Tandem Stator Flow Characteristic in a Low Speed Axial Research Compressor

A major goal in axial compressor development is to increase the efficiency and to reduce the weight of the module. In order to do so the power density has to be increased by raising the work per stage. Higher capability to do work can be achieved by increasing the circumferential velocity component of the fluid. Tandem stators might offer the ability to turn high swirling flow with lower losses compared to a single blade stator. In terms of higher aerodynamic loading the use of tandem vanes can be a key feature to allow the design of highly efficient and compact compressor modules.This paper presents the design and experimental validation of a single stage low speed axial compressor with a tandem outlet guide vane, representative for a modern jet engine high pressure compressor. Additionally to the overall compressor performance the 3D flow field of the tandem stator has been measured with a five hole probe at different operating points. The results will be discussed in comparison with numerical results. Furthermore, oil flow pictures are used to get a deeper insight into flow conditions inside the vane passage and to validate the numerically predicted secondary flow structures.Copyright

Numerical Investigation of Axial Compressor Stages With Differing Degrees of Reaction

In order to increase the efficiency of a compressor module, several loss sources such as aerofoil profile loss, secondary loss and clearance flow phenomena must be taken into account and balanced in the most efficient way. This current document presents the results of a numerical investigation based on a conventionally loaded high pressure compressor stage with different inlet and exit swirls. The effects of changing the degree of reaction on the compressor stage flow pattern is analysed in detail. In general, the correlation between the overall stage efficiency at constant pressure ratio and the degree of stage reaction is low. Nevertheless, the results show a direct impact on the rotor tip leakage flow and the secondary flow phenomena in the stator end-wall region when the degree of reaction is modified which is driven by the change in static pressure rise between the rotor and the stator passages. The balance of these two loss sources might have an impact on the efficiency and the stall behaviour of a multi-stage compressor.Copyright