ENGINEERING AND CFD

Hydrogen-enriched fuels can reduce the CO2 emissions of gas turbines. However, the presence of hydrogen in fuel mixtures can also lead to undesirable phenomena like flashback. Swirling combustors can take advantage of an axial air injection to increase their resistance against flashback. Such an example is the swirl-stabilized presented in experiments at the TU Berlin. The axial momentum ratio between the fuel jets and the air was found to control flashback resistance. This experimental hypothesis motivates the present study where large-eddy simulations of the combustion system are carried out to study the physics behind flashback phenomena in hydrogen gas turbine combustors.

An effective cooling of the gas turbine components subject to high thermal stresses is vital for the success of new engine and combustion concepts aiming at achieving further improvements in the energy conversion efficiency of the overall machine. The use of pulsating impinging jets - which enlarge vortex structures naturally occurring in the impinging jet flow when no pulsation is enforced - is a promising approach to develop a substantially more performant cooling system. To gain a deeper understanding of how the vortex system behaves under realistic conditions, researchers performed a DNS of a non-pulsating impinging jet flow with fully turbulent inflow conditions and compared its results with a reference case with a laminar inflow.

A cavity in a turbulent gas flow often leads to an interaction of vortex structures and acoustics. By exploiting this interaction, in some applications sound can be suppressed: silencers for jet engines or exhausts. In other cases, sound can be equally produced: squealing of open wheel-bays, sunroof and window buffeting, noise of pipeline intersection and tones of wind instruments. Typically, in expansive experimental runs, various configurations are tested in order to fulfill the design objectives of the respective application. Based on a 'Direct Numerical Simulation', the aim is to improve the understanding of the interactions between turbulence and acoustics of cavity resonators and to develop standalone sound prediction models, which…

Supersonic impinging jets can be found in different technical applications of aerospace engineering. Depending on the flow conditions, loud tonal noise can be emitted. The so-called impinging tone is investigated by researchers of the chair of computational fluid dynamics at the Technical University of Berlin. Using direct numerical simulations (DNS) carried out on the Cray HPC systems Hermit, Hornet and Hazel Hen of the HLRS, the underlying sound source mechanisms could be identified for a typical configuration.

As part of the collaborative research centre CRC 1029, impingement cooling is studied at the chair of computational fluid dynamics at the Technical University of Berlin. The project aims at a more efficient cooling of turbine blades. This is necessary since future combustion concepts within gas turbines bring much higher thermal loads. Large scale direct numerical simulations (DNS) are carried out using the Cray supercomputers Hermit, Hornet and Hazel Hen of the HLRS.

Shock-wave/boundary-layer interactions (SBLIs) play an important part in many engineering applications. They are common in internal and external aerodynamic flows. However, numerical treatment of such SBLIs is difficult as the important flow features place competing demands on the applied numerical algorithms. Using the HPC infrastructure provided by the HLRS, scientists of the Technische Universität Berlin performed a detailed direct numerical simulation of a transonic SBLI creating a detailed numerical database this way which is now available for further detailed studies.

Noise prediction is one of the most discussed topics for Computational Fluid Dynamics today due to the fact that noise optimization, energy saving and pollutant emission minimization complement each other. In a GCS Large Scale project headed by Professor Jörn Sesterhenn of the Technische Universität Berlin, numerical simulations of a supersonic jet were performed on HPC system SuperMUC of LRZ, focusing on the research of the acoustic field.