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Stuttgart Mühlhausen, Germany

Chatakonda O.,University of New South Wales | Knudsen E.,Stanford University | Hawkes E.R.,University of New South Wales | Talei M.,University of New South Wales | Pitsch H.,Institute of Combustion Technology
Proceedings of the 18th Australasian Fluid Mechanics Conference, AFMC 2012 | Year: 2012

Large-eddy simulations (LES) have been successfully applied to premixed turbulent flames in the flamelet regime. However, in the context of LES, comparatively little effort has focused on modelling of premixed flames in regimes of combustion in which the small scale eddies can penetrate the flame, the most important of which is the so-called thin-reaction zones (TRZ) regime. In this work, a posteriori LES of a turbulent premixed, methaneair slot-jet are performed using strained and unstrained premixed flamelet solutions. The turbulent flame speed is calculated using the Hawkes model [13] in both static and dynamic coefficients versions. The LES results are compared with direct numerical simulation (DNS) data, demonstrating that the strained flamelet solution with the Hawkes model performs well in simulating turbulence perturbations of sub-grid premixed flame structures in the TRZ regime.


Schiller G.,German Aerospace Center | Schiller G.,Institute of Technical Thermodynamics | Auer C.,German Aerospace Center | Auer C.,Institute of Technical Thermodynamics | And 15 more authors.
Applied Physics B: Lasers and Optics | Year: 2013

A planar solid oxide fuel cell (SOFC) operated with hydrogen at T = 1,123 K was equipped with an optically transparent anode flow field to apply species concentration measurements by 1D laser Raman scattering. The flow channels had a cross section of 3 mm × 4 mm and a length of 40 mm. The beam from a pulsed high-power frequency-doubled Nd:YAG laser (λ = 532 nm) was directed through one channel and the Raman-scattered light from different molecular species was imaged onto an intensified CCD camera. The main goal of the study was an assessment of the potential of this experimental configuration for a quantitative determination of local gas concentrations. The paper describes the configuration of the optically accessible SOFC, the laser system and optical setup for 1D Raman spectroscopy as well as the challenges associated with the measurements. Important aspects like laser pulse shaping, signal background and signal quality are addressed. Examples of measured species concentration profiles are presented. © 2012 Springer-Verlag Berlin Heidelberg.


Messerle V.E.,Al-Farabi Kazakh National University | Ustimenko A.B.,Al-Farabi Kazakh National University | Slavinskaya N.A.,Institute of Combustion Technology | Riedel U.,Institute of Combustion Technology
Proceedings of the ASME Turbo Expo | Year: 2012

This paper describes numerical and experimental investigations of coal gasification in a combined arc-plasma entrained flow gasifier. The experimental installation is intended to operate in the electric power range of 30-100 kW, mass averaged temperature 1800-4000 K, coal dust consumption 3-10 kg·h-1 and gas-oxidant flow 0.5-15 kg·h-1. The numerical experiments were conducted using the PLASMA-COAL computer code. It was designed for computation of the processes in plasma gasifiers. This code is based on a one-dimensional model, which describes the twophase chemically reacting flow with an internal plasma source. The thermo-chemical conversion of the oxidizer-coal mixture is described through formation of primary volatile products, their conversion in the gas phase and the coke residue gasification reactions. Kazakhstan Ekibastuz bituminous coal of 40% ash content, Germany Saarland bituminous coal of 10.5% ash content and 14% ash content bituminous coal from the Middleburg opencast mines, South Africa, were used for the investigation. Performed investigations demonstrate that regardless of the coal quality the plasma assisted coal gasification allows obtaining a pure synthesis gas at a ratio of H2:CO≥1. Copyright © 2012 by ASME.


Muhlbauer B.,German Aerospace Center | Muhlbauer B.,Institute of Combustion Technology | Ewert R.,German Aerospace Center | Ewert R.,German Institute of Aerodynamics and Flow Technology | And 4 more authors.
AIAA Journal | Year: 2010

The derivation and validation of a broadband combustion noise model is presented. The random particle-mesh approach for combustion noise is a hybrid computational fluid dynamics/computational aeroacoustics method and relies on the stochastic reconstruction of combustion noise sources in the time domain. The stochastic reconstruction of unsteady sound sources based on statistical turbulence quantities from a reacting Reynolds-averaged Navier-Stokes simulation is realized with the random particle-mesh method. In the present paper, the modeled combustion noise sources are derived for the use in conjunction with the linearized Euler equations for the computation of the acoustic propagation. Two open, nonpremixed, turbulent jet flames (DLR-A and DLR-B), which differ in their fuel outlet velocity and their respective Reynolds number, are used for the validation of the particle-mesh for combustion noise approach. Results of the reacting flow computations and the subsequent acoustic simulations are compared with measurements. Excellent agreement is found between the computed narrow band sound spectra and the experimental data. Copyright © 2010.


Sadanandan R.,German Aerospace Center | Sadanandan R.,Institute of Combustion Technology | Luckerath R.,German Aerospace Center | Luckerath R.,Institute of Combustion Technology | And 4 more authors.
Journal of Propulsion and Power | Year: 2011

The combustion behavior of natural gas flames with H 2 as an admixture is investigated in an optically accessible combustor operating under gas turbine relevant conditions. OH * chemiluminescence imaging and planar laserinduced fluorescence measurements of OH were performed along with exhaust gas analysis to investigate the influence of various parameters like mixture composition, degree of premixing, and velocities on the pollutant emissions. The results show that the degree of premixing along with the recirculation rate of the burned gases plays an important role in NO x and CO emissions. Compared with pure natural gas fired flames, the ones with H 2 admixture burned closer to the burner due to an increased reactivity. Under such conditions, a low emissions operating range can be achieved either by increasing the jet velocities or by reducing the degree of premixing. Both methods favor NO x reduction due to the suppression of local peak flame temperatures. The optimum combination of degree of premixing and jet velocity should lead to a recirculation and mixing rate such that the resulting ignition delay is long enough to promote mixing of the fresh fuel/air with the burned gases before the flame reactions but short enough to ensure a stable operation of the burner. At the same time, combustor residence times should be short in order to reduce the thermal-NO formation but long enough to enable complete combustion. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc.

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