The role of the baroclinic term in supersonic fuel/air mixing enhancement

Romagnosi, Luigi; Ingenito, Antonella; Cecere, D.; Giacomazzi, E.; Bruno, Claudio

doi:10.2514/6.2011-401

Cited by 11 publications

(6 citation statements)

References 7 publications

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“…inlet/isolator, supersonic combustor and expander/nozzle, while modeling of the integrated flow path in a full-scale combustion is generally scarce. From the literature, the most preferred modeling cases are the HyperShot I&II [3][4][5][6][7][8][9][10] and SCHOLAR [11][12][13][14][15][16], due a large degree to their relative complete data on experimental setup and measurements 2 American Institute of Aeronautics and Astronautics for model validation. Simulations based on the experimental cases tested on some other scramjet combustor facilities, such as the DLR scramjet combustor [17,18], the University of Virginia's Supersonic Combustion Facility (SCF) [18][19][20][21] and the CUBRC Combustion Duct [22], are also growing vigorously.…”

Section: Introductionmentioning

confidence: 99%

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Full-scale Detached Eddy Simulation of kerosene fueled scramjet combustor based on skeletal mechanism

Yao¹,

Wang²,

Lu³

et al. 2015

20th AIAA International Space Planes and Hypersonic Systems and Technologies Conference

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Large Eddy Simulation (LES) of kerosene fueled scramjet combustor is generally scare in the literature, due mainly to the formidable computational cost arisen by complex kerosene mechanism. In this study, the skeletal reduction of a detailed reaction mechanism (2185 species/8217 steps) of aviation kerosene is conducted using directed relation graph with error propagation and sensitivity analysis (DRGEPSA) method, resulting a skeletal mechanism consisting of 39 species/153 elemental reactions for China Daqing RP-3 aviation kerosene. The comparisons of adiabatic flame temperature, total heat release, ignition delay and laminar flame speed predicted by the skeletal mechanism show an overall good accordance with the original detailed reaction mechanism. Then a three-dimensional Detached Eddy Simulation (DES) modeling based on the skeletal kerosene mechanism is employed for the numerical analysis of a full-scale scramjet combustor, which has been experimentally tested in a long-time direct connect supersonic combustion test platform (abbreviated as DTZ) assembled in Chinese Academy of Sciences (CAS). Pressure and heat flux measurement systems are attached to the combustor assembly to monitor the real-time combustion performance and provide validation data for the numerical modeling. Three cases with fuel equivalence ratios from 0.8, 1.0 to 1.2 and the same crossflow conditions at Mach 2.0 are modeled. The time-averaged static pressure and heat flux are in generally good agreement with the experiment with the peak heat flux slightly underpredicted. The instantaneous and/or time-averaged pressure, momentum, temperature and turbulence fields, which are difficult to be measured, are analyzed to reveal the main flow and combustion physics, especially those related to the flame distribution and holding. The combustion is identified as in ramjet mode for the investigated cases. With the increasing of fuel equivalence ratio, the shock train propagates upstream in the isolator and the interaction between the upstream and downstream combustion assumes different patterns.

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Section: Introductionmentioning

confidence: 99%

“…those based on HyperShot I&II [3][4][5][6][7][8][9][10] or SCHOLAR cases [11][12][13][14][15][16], with a few based on pure hydrocarbons (e.g. ethylene [42,72], methane [73,74] and acetone [75]), however few are based kerosene [76][77][78][79].…”

Section: Introductionmentioning

confidence: 99%

Full-scale Detached Eddy Simulation of kerosene fueled scramjet combustor based on skeletal mechanism

Yao¹,

Wang²,

Lu³

et al. 2015

20th AIAA International Space Planes and Hypersonic Systems and Technologies Conference

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“…Recent LES studies [26] have shown that baroclinic effects can play a major role in turbulent flows where density and pressure gradients are misaligned and adding such a correction to the k-ε model to increase turbulence production provides substantive improvements to data comparisons for applications such as angled/transverse jet interactions in a high-speed environment. Following the formulation for buoyant jets provided by Nicolette, et al [27], an extension to the turbulence kinetic energy production is incorporated to account for the baroclinic production, G b ,…”

Section: Turbulence Model Equations 21 K-ε Turbulence Modelmentioning

confidence: 99%

“…Our approach has been to employ extensions that do not detract from the reliable performance of the basic model for simpler flows. One such extension, based on LES calculations of angled jet mixing problems [26], is the inclusion of a baroclinic torque correction term [27] which serves to increase the initial mixing of angled jets. For high-speed flows, using a well calibrated compressibility-correction that works for parallel mixing problems, angled mixing is typically under-predicted.…”

Section: Introduction and Historical Perspectivementioning

confidence: 99%

Turbulence Modeling Advances and Validation for High Speed Aeropropulsive Flows

Dash

Brinckman

Ott

2012

International Journal of Aeroacoustics

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Advances made in extending a unified k-ε based RANS turbulence model to "more reliably" analyze high-speed aero-propulsive flows are discussed. The unified model solves additional scalar fluctuation model (SFM) equations to predict variations in turbulent Prandtl and Schmidt numbers, which can be quite substantial for these types of flows. The discussion includes a historical perspective of the developmental work performed as well as an overview of the current modeling status. RANS modeling still plays a dominant role in the "practical" analysis of aeropropulsive flows. It is used for preliminary design and design-optimization studies, where a large matrix of calculations must be performed, and, in the application of hybrid RANS/LES methodology, where the use of LES is often restricted to massively separated or jet/free shear regions of the flow. In extending the model, we have adhered to a "building-block" philosophy using data sets of increasing complexity and emphasizing high-speed applications where compressibility effects can play a dominant role. Fundamental laboratory data sets as well as benchmark LES/DNS solutions have been used for model calibration and validation, with several key comparisons presented in this article. Recent extensions described in this article include: low Re extensions to the SFM model improving near wall predictions; a compressibility/density gradient correction to the species fluctuation equation improving mixing predictions; and, a baroclinic torque correction to the kinetic energy equation improving predictions for angled jets. This article shows how these extensions serve to improve comparisons with data for a number of basic aeropropulsive flows, and it also discusses utilization of the unified RANS model in a hybrid RAN/LES DES modeling framework. NOMENCLATURE CC Compressibility correction nomenclature CVS Compressible vortex stretching nomenclature DES Detached Eddy Simulation DNS Direct Numerical Simulation EASM Explicit Algebraic Stress Model F d Density correction term in k f equation F m , f 1 , f 2 Near wall damping terms in SSGZ model G b Baroclinic torque correction term in k equation k Turbulent kinetic energy (TKE) k e Internal energy (or temperature) variance k f Species variance L et Turbulent Lewis number LES Large Eddy Simulation M Mach number M c Convective Mach number M t Turbulent Mach number PDE Partial differential equation P k Turbulent production term Pr t Turbulent Prandtl Number RANS Reynolds averaged Navier-Stokes SSGZ So, Sarkar, Gerodimos, and Zhang Sc t Turbulent Schmidt Number SFM Scalar fluctuation model SS ε Round jet vortex stretching correction SS k Compressibility correction term SWBLI Shock wave boundary layer interaction ε Dissipation rate of turbulent kinetic energy ε e Dissipation rate of internal energy fluctuations ε f Dissipation rate of scalar fluctuations λ b Near wall coefficient blending function ξ εT Near wall damping term in SFM model µ t Turbulent viscosity 814 Turbulence modeling advances and validation for high speed aeropropul...

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“…Typically, the detailed mechanisms for small-molecule fuels (C 1 -and C 2 -based) consist of less than one hundred species, while largemolecule Jet fuels (C >10 -based) consist of hundreds of or even thousands of species. For this reason, current supersonic combustion modelings are mostly based on hydrogen fuel [24, [37][38][39][40][41][42][43][44][45][46][47][48] and only a small portion of them are based on small-molecule hydrocarbon fuels (.g. ethylene [49,50], methane [51,52] and acetone [53]).…”

Section: B Kerosene Mechanism Reduction and Turbulent Combustion Modmentioning

confidence: 99%

A comparative study of elliptical and round scramjet combustors by Improved Delayed Detached Eddy Simulation

Yao

Yuan

et al. 2017

21st AIAA International Space Planes and Hypersonics Technologies Conference

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To explore the combustion performance of non-rectangular type supersonic combustors, the flow and combustion characteristics in round and round-to-elliptic shape-transition (RdEST) supersonic combustors under the same configurations of flight Mach number and fuel equivalence ratio were compared based on modeling results. The fuel equivalence ratio is maintained the same as 0.8, while two inlet Mach numbers of 2.5 and 3.0 both corresponding to a real flight Mach number of 6.5 are tested. To alleviate the strict requirements on wall-normal and -parallel grid spacing, Improved Delayed Detached Eddy Simulation (IDDES) is employed in this study to enable an automatic choice of RANS or LES mode depending on the local boundary layer thickness and turbulent viscosity. To reduce the computational cost of stiff kerosene oxidation chemistry, a total of four versions of skeletal mechanisms (respectively 48s/197r, 39s/153r, 28s/92r and current 19s/54r) have been developed based on the detailed 2815s/8217r Dagaut mechanism by using a highly efficient and reliable directed relation graph with error propagation and sensitivity analysis (DRGEPSA) method together with manual path analysis. Although the mechanism size has been significantly reduced, key kinetic properties such as adiabatic flame temperature, heat release rate, ignition delay and laminar flame speed all agree well with the original detailed mechanism. The static pressure along streamwise direction is compared with the measurement to validate the modeling results. Two key aspects are well predicted, i.e. the pressure ratio and the initial pressure rise location, indicating that the flame anchoring location and the distribution of wave structures inside the combustor are close to the actual situation. Then the aerodynamic fields are analyzed for the round and elliptic combustors to compare their flow, mixing and combustion related flow structures. The three-dimensional wave structures inside the elliptic combustor are firstly shown to reveal the influence of nonaxisymmetric cross-section on the shock train and Mach field. Especially the time evolution of the flame region is analyzed, and dominant flame modes are extracted by the aid of proper orthogonal decomposition (POD) method.

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The role of the baroclinic term in supersonic fuel/air mixing enhancement

Cited by 11 publications

References 7 publications

Full-scale Detached Eddy Simulation of kerosene fueled scramjet combustor based on skeletal mechanism

Full-scale Detached Eddy Simulation of kerosene fueled scramjet combustor based on skeletal mechanism

Turbulence Modeling Advances and Validation for High Speed Aeropropulsive Flows

A comparative study of elliptical and round scramjet combustors by Improved Delayed Detached Eddy Simulation

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