A comparison of the numerical predictions of the supersonic combustion of Hydrogen using the S-A and SST k – ω models
11 Aug 2009-Progress in Computational Fluid Dynamics (Inderscience Publishers)-Vol. 9, Iss: 8, pp 475-489
TL;DR: In this article, the influence of the turbulence model on the numerical predictions of supersonic combustion of hydrogen in a model combustor is investigated, showing that the mixing and hence the heat release is over predicted by the SA model.
Abstract: In the present work, the influence of the turbulence model on the numerical predictions of supersonic combustion of hydrogen in a model combustor is investigated. Three dimensional, compressible, turbulent, reacting flow calculations using the Shear Stress Transport (SST) k – ω model have been carried out. The results are compared with earlier results obtained using the Spalart-Allmaras model. The effect of detailed chemistry on the predictions of heat release and combustion efficiency is also investigated for one injection scheme. The calculations show that the mixing and hence the heat release is over predicted by the SA model. Whereas, the peak values for pressure and temperature are predicted better by the SST k – ω model. This investigation demonstrates the importance of the use of a two equation turbulence model over a one equation model for studying such complex flow phenomena.
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TL;DR: In this article, the effect of turbulent dispersion on the mixing efficiency is studied using a stochastic model in conjunction with the two-equation shear stress transport k-ω turbulence model.
Abstract: In this numerical study, supersonic combustion of kerosene in three model combustor configurations is investigated. To this end, 3-D, compressible, turbulent, nonreacting, and reacting flow calculations with a single step chemistry model have been carried out. For the nonreacting flow calculations, the droplet diameter distribution at different axial locations, variation of the Sauter mean diameter, and the mixing efficiency for three injection pressures are presented and discussed. In addition, the effect of turbulent dispersion on the mixing efficiency is studied using a stochastic model in conjunction with the two-equation shear stress transport k-ω turbulence model. For the reacting flow calculations, contours of heat release and axial velocity at several axial locations are used to identify regions of heat release inside the combustor. Combustion efficiency predicted by the present results is compared with earlier predictions for all the combustor models. Furthermore, the predicted variation of static pressure along the combustor top wall is compared with experimental data reported in the literature. Calculations show that the penetration and spreading of the fuel increases with an increase in the injection pressure. Predicted values of the combustion efficiency are more realistic when the spray model is used for modelling the injection of the fuel. The importance of the mixing process, especially for a liquid fuel such as kerosene, on the prediction of heat release is discussed in detail.
62 citations
TL;DR: In this article, the effect of variation in the inlet Mach number and stagnation temperature on the mixing of fuel with the oxidizer and the subsequent stabilization of a flame in a combustor at supersonic conditions was numerically investigated.
33 citations
TL;DR: In this paper, the three-dimensional coupled implicit Reynolds average Navier-Stokes (RANS) equations, SST k - ω turbulent model and Eddy-Dissipation Concept (EDC) reaction model are employed to investigate the flow fields with different mixer configurations, namely the lobe, rectangle, triangle, and pentagon.
24 citations
TL;DR: In this article, a new asymmetric strut-based fuel injection is proposed and investigated for enhanced fuel-air mixing and combustion in supersonic combustors, where the strut configuration is re-designed and the fuel injector is tested.
Abstract: In this paper, a new asymmetric strut-based fuel injection is proposed and investigated for enhanced fuel-air mixing and combustion in supersonic combustors. The strut configuration is re-designed ...
4 citations
Cites background or methods from "A comparison of the numerical predi..."
...In most of the studies, the single step reaction model is efficient to present the dominant features of the scramjet combustor (Desikan and Kurian 2006; Kumaran and Babu 2009a; Manna et al. 2013)....
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...…injection systems incorporated in the supersonic combustor are wall injection (Northam and Anderson 1986), strut injection (Desikan and Kurian 2006; Kumaran and Babu 2009a; Manna et al. 2013; Qiu et al. 2020), cavity injection (Kim, Baek, Han 2004; Li et al. 2020a; Peng et al. 2020; Roos et al.…...
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...EDM is incorporated for single step (Kumaran and Babu 2009a; Manna et al. 2013; Xianyu et al. 2007) chemically reaction mechanism in the turbulent flow....
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...The efficiency of the combustion is calculated based on mass fraction of water vapor as proposed in (Kumaran and Babu 2009b). ηcombustion ¼ 1 9 αH2OρudA � �x inlet _Mfuelinlet where the αH2O is the mass fraction of water vapor....
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Dissertation•
01 Jan 2015
TL;DR: In this paper, the effect of different droplet sizes on a gas flow around a compressor blade in a wet gas compressor is investigated, and the results show that a thin film will cover the blade which has an effect on the particle tracks.
Abstract: Subsea is a term that refers to drilling and processing of gas and oil in underwater
locations. One example of a subsea technology is a wet gas compressor which is
used to compress fluids that consists of multiple phases. By compressing the wet
gas the recovery of unprocessed streams can be increased and the investment cost
reduced. The Norwegian company OneSubsea has designed and manufactured a
wet gas compressor, first of its kind, and is developing the next generation of the
compressor with assistance from the technical consultancy company AF. At AF’s
department for technical analysis in Gothenburg simulations of the compressor with
pure gas flow are performed. To compliment these simulations a separate project is
performed to evaluate the effects of a flow that is multiphase. Therefore the aim of
this project is to study the effect of different droplet sizes on a gas flow around a
compressor blade in a wet gas compressor.
Multiphase flow, consisting of natural gas and oil droplets, around one blade in the
first step of the wet gas compressor is considered. Computational fluid dynamic
simulations of one way coupled multiphase flow are solved using the conservation
equations of mass and momentum, Lagrangian particle tracking and the k −! SST
turbulence model. The range of the droplet size and volume fraction evaluated are
1-200 μm and 1-2%, respectively.
Several different studies were performed. The results are characterised by flow properties
outputted just after the blade, at the start of the next blade row, and with
visualisations of the particle tracks around the blade. The main study, the Base
case, consisted of 22 different case studies where the droplet size was held constant
for each case, but varied within the size range between the cases. A coefficient of
restitution (COR) was used to model the droplet wall interaction and the results
showed that the droplets have an effect on the outflow from the first compressor
step. The droplets decrease the average velocity angle at the axial clearance for all
droplet sizes. The decrease is low, at a relatively constant value, for droplet sizes
up to around 80 μm. For droplets larger than 80 μm, velocity angle decreases with
increasing droplet size. By studying the particle tracks around the blade the droplet
flow could be divided into three characteristic regions, according to the importance
of wall interaction and effect of gas flow on the droplet.
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After analysing the results from the Base case the importance of wall interaction
was studied further. Simulations showed that the majority of the droplets are colliding
with the wall. A sensitivity study for the COR was performed which showed
that the droplet flow is independent of COR for droplet sizes up to 50 μm, almost
independent up to 100 μm, and strongly dependent for the rest of the size range.
A case study where the droplets were trapped at the wall was performed, but the
reliability of these results are questionable since the data is based on a small fraction
of droplets that pass the blade. For the final wall interaction study a liquid wall film
at the blade was modelled. According to the theory this should be the most realistic
way to model a droplet wall interaction. Due to lack of time this case study could
not be fully completed and only an idea of the result is presented. The result shows
that a thin film will cover the blade which has an effect on the particle tracks.
The conclusion from this project is that the droplets will effect the flow around
the blade by decreasing the average velocity angle for the flow entering the next
blade row; the magnitude of the effect is increasing with increased droplet size. The
droplet wall interaction is important for the particle tracks, thus it is recommended
to further evaluate this aspect.
2 citations
Cites background from "A comparison of the numerical predi..."
...The disadvantage of this model is that it over-predicts turbulence in regions where large normal strain can be found, for example in stagnation regions [1, 10]....
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