A low pressure turbine guide vane of an aircraft engine is structurally redesigned for additive manufacturing (AM). AM is known to provide more design freedom than conventional manufacturing methods, which encourages the implementation of numerical optimization methods in the design process in order to reduce weight by eliminating unneeded material. One such method is called topology optimization (TO), which finds the optimal material distribution inside a fixed design space. Using commercial software, TO is conducted to find the optimal geometry. The guide vane is subject to gas loads. During optimization, constraints for bending deformation and Eigen frequencies are applied. The design space consists of the airfoil interior and the shrouds, leaving aerodynamic surfaces untouched. Several TO approaches are examined and the result is preliminarily evaluated in a stationary coupled temperature-displacement FEA with take-off loading conditions. The results indicate a potential weight reduction of 19% but with a rise in temperature gradients. An enlarged shroud geometry would enable even greater weight reduction.

The examination of small turbojet engines for unmanned aviation systems is a main research activity at the Institute of Aeronautical Engineering at the Universität der Bundeswehr München. The special requirements for the design of these propulsion systems include compact installation size, high reliability and low acquisition costs. But the low overall efficiency, the high exhaust gas temperature and excessive noise emission limit the options for integration and mission profiles. The concept of the ejector nozzles offers a solution for further improving the propulsion system following the requirements. The secondary mass flow delivered from the ejector nozzle can not only reduce the exhaust gas temperature but also enhance the thrust. Ejector nozzles have been developed in combination with special mixer nozzles with the design goal of increasing the pumping performance and thrust augmentation. Both numerical and experimental investigations are conducted to study the mixing ability of the primary nozzle, the key to optimising the ejector performance.

Tip blowing and axial slot casing treatments have shown their ability to enhance the stability of a transonic axial compressor with different effects on efficiency. For an effective application of these casing treatments, a good knowledge of the influence of the casing treatment on the rotor flow field is important. There is still a need for more detailed investigations, in order to understand the interaction between the treatment and the near casing 3D flow field. For transonic compressor rotors this interaction is more complex, as super- and subsonic flow regions alternate while interacting with the casing treatment. In the present study, an axial slot and a tip blowing casing treatment, which have been developed and optimized for the same tip critical transonic axial compressor rotor (reference rotor) by Streit et al. [1] and Guinet et al. [2], are subject of the investigation. Both casing treatment types showed their capabilities to enhance the compressor stability without losing by means of CFD simulations. Since the higher compressor stability allows a higher blade loading, Streit et al. reduced the blade number of the rotor. Thus, the efficiency was increased due to the reduction of friction losses. However, applying the tip blowing casing treatment to the reduced rotor shows a negative effect on the efficiency. Both casing treatment types recirculate flow from a downstream to an upstream location of the rotor and reinject it to enhance the near casing flow field. Although the working principle of the two casing treatment types are similar, the transfer of the casing treatments from the reference to the reduced rotor show different trends in efficiency. Therefore, the effect of recirculation cannot explain the difference in efficiency. Hence, applying axial slots must include additional flow features, compared to recirculation channels. Compensating effects as in circumferential groove casing treatments and other flow interactions between the near casing flow field and the slot flow are considered. These additional mechanisms of the axial slot casing treatment will be identified and isolated by comparing the two different casing treatment types. The numerical simulations are carried out on a 1.5 stage transonic axial compressor using URANS simulations.

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