Revised model coefficients for vibrational relaxation in a nitrogen–oxygen gas mixture

Gehre, Rolf; Wheatley, Vincent; Boyce, Russell

doi:10.1007/s00193-012-0401-z

Cited by 8 publications

(9 citation statements)

References 14 publications

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“…Thermal non-equilibrium effects are modeled with the Laudau-Teller-model 34 and the relaxation rates are specified in Gehre et al 35 For vibrational relaxation, only vibration-translation (V-T) coupling is being modeled, vibration-vibration (V-V) coupling is neglected and an average vibrational temperature T v , which represents the total vibrational energy, is used.…”

Section: Numerical Setupmentioning

confidence: 99%

Combustion Regimes in Inlet-fulled, Low Compression Scramjets

Gehre¹,

Wheatley²,

Boyce³

2015

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

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This paper investigates the combustion regimes that are present in inlet-fueled, low compression scramjets. Injection of fuel in the inlet allows mixing to take place prior to ignition, and permits the fuel plumes to interact with strong shocks and rarefactions at the combustor entrance, which accelerates the mixing process. Consequently, the combustion is partially premixed. Wall-modeled large-eddy simulations (WMLES) are used to accurately resolve or model the turbulent flow structures occurring during the supersonic combustion process. Based on the WMLES data, spatial distributions of turbulent and chemical time scales can be extracted and used to determine the representative turbulent Damköhler and Reynolds numbers. The collective WMLES data is visualized using the Williams diagram, which shows that a wide range of combustion regimes are present throughout the supersonic combustion process. NomenclatureDa t Turbulent Damköhler number H Altitude, m J Momentum flux ratio Ka Karlovitz number k Turbulence kinetic energy, J/kg l 0 Integral length scale, m l c Chemical length scale, m l δ Reaction zone length scale, m M Mach numbeṙ m Mass flow rate, kg/s p Pressure, Pa q Dynamic pressure, Pa R N Leading edge radius, m Re t Turbulent Reynolds number Re u Unit Reynolds number s L Flame speed, m/s T Temperature, K u Velocity, m/s Turbulent dissipation, J/(kg s) η Kolmogorov length scale, m ν Laminar kinematic viscosity, m 2 /s τ c Chemical time scale, s τ δ Reaction zone time scale, s * PhD Student, School of Mechanical and Mining Enginieering, University of Queensland, Student Member AIAA.

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Section: Numerical Setupmentioning

confidence: 99%

Combustion Regimes in Inlet-fulled, Low Compression Scramjets

Gehre¹,

Wheatley²,

Boyce³

2015

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

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“…The relaxation process between the translational and vibrational modes takes much longer, which results in regions of thermal non-equilibrium (T = T v ). The speed of the relaxation process can be calculated using the Landau-Teller relaxation model [124] coupled with a semi-empirical formulation for the relaxation time, which is mainly based on the one given by Millikan and White [144], but modified to better match experiments according to Gehre et al [65]. Nevertheless, the relaxation time τ is still formulated as…”

Section: Thermal Non-equilibriummentioning

confidence: 99%

“…with p being the gas mixture pressure expressed in atmospheres. It should be noted that for a 5-species air mixture several coefficients A sr and B sr are replaced with experimental data as analyzed and validated by Gehre et al [65]. For hydrogen combustion schemes, experimental data regarding the relaxation mechanism for several collision combinations is provided by [137].…”

Section: Vibrational Source Termmentioning

confidence: 99%

“…These data sets are, however, not complete and furthermore not validated against relevant flow problems. As shown by Gehre et al [65] using unvalidated data sets can lead to significant modeling errors, which is why experimental data for hydrogen/air relaxation is omitted from this analysis. It is, however, strongly recommended to validate these data sets to improve the modeling of the thermal relaxation processes.…”

Section: Vibrational Source Termmentioning

confidence: 99%

“…Each simulation uses a five species gas model consisting of N 2 , O 2 , NO, O and N, which includes chemical non-equilibrium effects, where Park's curve fits from 1990 [163] model the chemical equilibrium constants. Thermal non-equilibrium effects are modeled with the Laudau-Teller-model [124], with the relaxation rates being specified in [65]. For vibrational relaxation, only vibration-translation (V-T) coupling is being modeled, vibration-vibration (V-V) coupling is neglected and an average vibrational temperature T v , which represents the total vibrational energy, is used.…”

Section: Nozzle Simulationmentioning

confidence: 99%

See 2 more Smart Citations

The flow physics of inlet-fueled, low-compression scramjets

Gehre¹

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Calculation of Vibrational Relaxation Times Using a Kinetic Theory Approach

Oblapenko

2018

J. Phys. Chem. A

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In the present work, a method for computation of vibrational relaxation times based on a kinetic theory definition is utilized to calculate vibrational relaxation times of molecules present in air (N 2 , O 2 , and NO) in collisions with air species particles. An overview of available experiment VT relaxation time measurements, as well as quasi-classical trajectory (QCT) calculation results, and various empirical models, is given. Different inelastic cross-section models are used for the computation of the relaxation times, and their parameters are adjusted to fit the available experimental data and QCT results. It is shown that the proposed method of calculation can give a quantitative and qualitative agreement with the available data in a wide range of temperatures; the obtained interaction parameters may be used not only for vibrational relaxation time calculation within a multitemperature framework but also for development of statespecific models for use in CFD and DSMC codes.

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Revised model coefficients for vibrational relaxation in a nitrogen–oxygen gas mixture

Cited by 8 publications

References 14 publications

Combustion Regimes in Inlet-fulled, Low Compression Scramjets

Combustion Regimes in Inlet-fulled, Low Compression Scramjets

The flow physics of inlet-fueled, low-compression scramjets

Calculation of Vibrational Relaxation Times Using a Kinetic Theory Approach

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