Werner Krebs | SIEMENS - Academia.edu (original) (raw)

Papers by Werner Krebs

Volume 2: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, 2001

Since the flame of high intense low NOx gas turbine combustion systems is stabilized by swirl, th... more Since the flame of high intense low NOx gas turbine combustion systems is stabilized by swirl, the analysis of the swirl flow is very crucial to the design and optimization of such combustion systems. Although a huge amount of publications have been provided on this field just a few have used Large Eddy Simulation due to limits in computer resources. Using Large Eddy Simulation the large vortical structure of the flow is resolved leading to a much better insight of the flow features. Hence, in this paper the Large Eddy Simulation has been applied to investigate the non reacting confined swirling flow downstream of a gas turbine burner. A high accuracy of the prediction of the full three dimensional simulation could be pointed out by comparison of the computational results to measurements. Further the large vortical structure and the dynamic behavior of the flow has been analyzed. The formation of a precessing vortex core is visualized. Due to the precessing motion of the central rec...

Fluid Mechanics and Its Applications, 2002

Die Erfindung betrifft einen Dusentrager (1) fur einen Strahlbrenner, mit einem Dusentragerkorper... more Die Erfindung betrifft einen Dusentrager (1) fur einen Strahlbrenner, mit einem Dusentragerkorper (2) umfassend eine im Betrieb einer Brennkammer zugewandte Heisseite (3) und eine von der Brennkammer abgewandte Kaltseite (4), zwischen denen sich ein umlaufender Rand (5) erstreckt, wobei sich Durchlasse (6) im Dusentragerkorper (2) von der Kaltseite (4) bis zur Heisseite (3) erstrecken und Vormischzonen ausbilden, wobei der Dusentragerkorper (2) aus Metallschaum (7) gefertigt ist und Innenwande (8) der Durchlasse (6) fur Vormischzonen gasdicht ausgefuhrt sind.

Proceedings of the First International Symposium on Radiation Transfer, 1995

Volume 2: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, 1999

A detailed thermal analysis involving both measurements and calculations has been carried out in ... more A detailed thermal analysis involving both measurements and calculations has been carried out in order to determine the wall heal load and to optimize the amount of cooling air for an annular combustor. In calculations, the convective wall heat flux has been detemined by application of a 3D Navier-Stokes Code. Furthermore, the radiation exchange between the hot combustion gases and the liner has been calculated using a multidimensional spectral approach. Although a quite high thermal power density is found within the combustion chamber the wall heat load is at a low level. Values are well below 80 kW/m2, due to the application of ceramic tiles which have a low thermal conductivity. The wall heat load is dominated by radiation emitted in the lower gas radiation bands (λ < 2.9 μm). The convective wall heat flux is nearly balanced out by the sealing air which is discharged through gaps between the ceramic tiles. The cooling effect of the sealing air, however, is strongly influenced ...

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, 1998

Environmental compatibility requires low emission burners for gas turbine power plants as well as... more Environmental compatibility requires low emission burners for gas turbine power plants as well as for jet engines. In the past significant progress has been made developing low NO x and CO burners by introducing lean premixed techniques. Unfortunately these burners often have a more pronounced tendency than conventional burner designs to produce combustion driven oscillations. The oscillations may be excited to such an extent that strong pulsation may possibly occur; this is associated with a risk of engine failure and higher NO x emissions.

Journal of Turbulence, 2004

... The first configuration consists of 10 opposed in-line jets in cross-flow (JICF) issuing in a... more ... The first configuration consists of 10 opposed in-line jets in cross-flow (JICF) issuing in a rectangular duct. ... Journal of Turbulence 5 (2004) 005 (http://jot.iop.org/) 8 ... of the jet injection hole shape and size [49, 50], the jet inlet velocity profile [51], the initial jet penetration angle [52 ...

Proceedings of the Combustion Institute

In recent years, the NOx emissions of heavy duty gas turbines have been significantly reduced by ... more In recent years, the NOx emissions of heavy duty gas turbines have been significantly reduced by introducing lean premixed combustion. However, these flames are known to be prone to combustion instabilities, which became the key issue of modern gas turbine combustion research. In this paper, investigations of a single model gas turbine burner are presented with special focus on thermo-acoustic eigenmodes of the combustor and the resulting interaction between periodic flow field oscillations and flame front fluctuations. A numerical analysis of the eigenmodes of the combustor rig was preformed and compared to pressure probe measurements. By the numerical analysis Helmholtz mode pressure oscillations were predicted to be present in the air plenum upstream the burner as well as in the combustion chamber. These oscillation modes could well be confirmed by the analysis of the pressure signals taken at different position within the combustor rig. By these pressure oscillations thermo-acoustic flame instabilities are triggered. Due to a phase lag between the pressure oscillations in the air plenum and those in the combustion chamber, fluctuations of air flow through the burner are induced, which in turn cause fluctuations of the equivalence ratio at the burner exit plane. As result, fluctuations of the heat release rate within the flame are established, which interfere with the acoustics of the rig and, thus, unstable combustion is maintained. The dynamics of the flow field and of the flame was studied experimentally by phase-locked LDA and OH-LIF diagnostics. The experimental results give an excellent insight into the chain of processes that are responsible for the thermo-acoustic instabilities. Interestingly, two different oscillation modes could be identified depending on the amplitude of the oscillations. At low oscillation levels only weak and locally confined velocity fluctuations in the main reaction zone were observed which do not have any significant impact on the flame. By increasing the equivalence ratio, the transition from low to high oscillation levels can be triggered. Under high oscillation levels, a pumping motion of the flow field in axial direction could be identified which causes strong periodic disturbances of the flame.

Progress in Computational Fluid Dynamics an International Journal, Mar 20, 2015

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