I am wondering if anyone could give me any advice on the combustion model I should use for a scramjet? I am currently using a laminar finite rate model, but will probably change to a finite rate/eddy dissipation model soon.

I am just using the default hydrogen model. Are there any values I need to change, due to the high mach numbers I will be using (Mach 10 freestream, Mach 7 in chamber)

Also if anyone has any other advice that would help, that would be appreciated.

Thank you

Andrew

I would recommend using the laminar finite-rate model with the coupled implicit solver. You might also want to try importing a detailed chemkin mechanism (File -> Import) such as this one...

!<><><><><><><><><><><><><><><><><><><><><><><><>< ><><><><><><><><><><><><><><><><><><><><> ! ! H2/O2 oxidation reaction mechanism -- ! (c) Li, Zhao, Kazakov, and Dryer, Princeton University, 2003. ! !!!!!!!!!!!!!!!! IMPORTANT !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!! ! ! HOW TO USE THIS MECHANISM: ! ! Due to ! (1) limitations of CHEMKIN-II format (specifically, an inability to implement ! temperature-dependent collision efficiencies in falloff reactions) ! and ! (2) lack of fundamental understanding of the mixing rules for the falloff ! reactions with the bath gases that have different broadening factors, ! ! the present implementation represents a compromise (approximate) formulation. ! ! As a consequence, PRIOR TO ITS USE IN THE CALCULATIONS, THIS FILE HAS TO BE ! MODIFIED. DEPENDING ON WHAT BATH GAS (DILUTANT) IS MOST ABUNDANT IN YOUR SYSTEM ! (THE PRESENT CHOICES ARE N2, AR, OR HE), YOU SHOULD UNCOMMENT THE CORRESPONDING ! BLOCK FOR THE REACTION H+O2(+M)=HO2(+M), AND COMMENT THE BLOCK FOR OTHER DILUTANT(S). ! AS GIVEN, THE MAIN DILUTANT IS SET TO BE N2. ! ! ! HOW TO REFERENCE THIS MECHANISM: ! ! Li, J., Zhao, Z., Kazakov, A., and Dryer, F.L. "An Updated Comprehensive Kinetic Model ! for H2 Combustion", Fall Technical Meeting of the Eastern States Section of the ! Combustion Institute, Penn State University, University Park, PA, October 26-29, 2003. ! ! ! HOW TO CONTACT THE AUTHORS: ! ! Prof. Frederick L. Dryer ! D-329-D Engineering Quadrangle ! Mechanical and Aerospace Engineering ! Princeton University ! Princeton, NJ 08544-5263 ! Phone: 609-258-5206 ! Lab: 609-258-0316 ! FAX: 609-258-1939 ! Email: fldryer@Princeton.EDU ! !************************************************* ********************************************* ! Development notes: ! !The following H2/O2 mechanism is based on Mueller et al's (Int.J.Chem.Kinet.1999,31:113) !Changes: ! !1.update the standard heat of formation of OH at 0K to 8.85kcal/mol (Ruscic et al, ! J. Phys. Chem. A, 2002, 106:2727) ! !2.update the rate constant of H+O2=O+OH as proposed by Hessler (J. Phys. Chem. A, 1998, ! 102:4517) ! !3.update the low-pressure-limit rate constant of H+O2(+M)=HO2(+M) with bath gases: H2, ! O2, N2, AR, HE, H2O as proposed by Michael et al (J. Phys. Chem. A, 2002,106:5297). ! The third-body efficiency of H2, O2, and H2O are taken as the average value over ! the temperature range of 300-3000K. ! The Fc in Troe's form with N2 and AR/HE as bath gas are different, so the fall-off ! kinetics is expressed in two sets, for N2 and AR/HE, respectively. ! !4.for all other recombination reactions, assume the third-body efficiency of HE is ! the same as AR. ! !5.modify the A factor of the rate constant of H+OH+M=H2O+M to 3.8E+22. ! !END OF NOTES !************************************************* ********************************************* ELEMENTS H O N END

SPECIES H2 O2 H2O H O OH HO2 H2O2 N2 END

REACTIONS

!H2-O2 Chain Reactions

! Hessler, J. Phys. Chem. A, 102:4517 (1998) H+O2=O+OH 3.547e+15 -0.406 1.6599E+4

! Sutherland et al., 21st Symposium, p. 929 (1986) O+H2=H+OH 0.508E+05 2.67 0.629E+04

! Michael and Sutherland, J. Phys. Chem. 92:3853 (1988) H2+OH=H2O+H 0.216E+09 1.51 0.343E+04

! Sutherland et al., 23rd Symposium, p. 51 (1990) O+H2O=OH+OH 2.97e+06 2.02 1.34e+4

!H2-O2 Dissociation Reactions

! Tsang and Hampson, J. Phys. Chem. Ref. Data, 15:1087 (1986) H2+M=H+H+M 4.577E+19 -1.40 1.0438E+05

H2/2.5/ H2O/12/

! Tsang and Hampson, J. Phys. Chem. Ref. Data, 15:1087 (1986) O+O+M=O2+M 6.165E+15 -0.50 0.000E+00

H2/2.5/ H2O/12/

! Tsang and Hampson, J. Phys. Chem. Ref. Data, 15:1087 (1986) O+H+M=OH+M 4.714E+18 -1.00 0.000E+00

H2/2.5/ H2O/12/

! Tsang and Hampson, J. Phys. Chem. Ref. Data, 15:1087 (1986) !H+OH+M=H2O+M 2.212E+22 -2.00 0.000E+00 H+OH+M=H2O+M 3.800E+22 -2.00 0.000E+00

H2/2.5/ H2O/12/

!Formation and Consumption of HO2

! Cobos et al., J. Phys. Chem. 89:342 (1985) for kinf ! Michael, et al., J. Phys. Chem. A, 106:5297 (2002) for k0

!************************************************* ***************************** ! MAIN BATH GAS IS N2 (comment this reaction otherwise) ! H+O2(+M)=HO2(+M) 1.475E+12 0.60 0.00E+00

LOW/6.366E+20 -1.72 5.248E+02/

TROE/0.8 1E-30 1E+30/

H2/2.0/ H2O/11./ O2/0.78/

! Tsang and Hampson, J. Phys. Chem. Ref. Data, 15:1087 (1986) [modified] HO2+H=H2+O2 1.66E+13 0.00 0.823E+03

! Tsang and Hampson, J. Phys. Chem. Ref. Data, 15:1087 (1986) [modified] HO2+H=OH+OH 7.079E+13 0.00 2.95E+02

! Baulch et al., J. Phys. Chem. Ref Data, 21:411 (1992) HO2+O=O2+OH 0.325E+14 0.00 0.00E+00

! Keyser, J. Phys. Chem. 92:1193 (1988) HO2+OH=H2O+O2 2.890E+13 0.00 -4.970E+02

!Formation and Consumption of H2O2

! Hippler et al., J. Chem. Phys. 93:1755 (1990) HO2+HO2=H2O2+O2 4.200e+14 0.00 1.1982e+04 DUPLICATE HO2+HO2=H2O2+O2 1.300e+11 0.00 -1.6293e+3 DUPLICATE

! Brouwer et al., J. Chem. Phys. 86:6171 (1987) for kinf ! Warnatz, J. in Combustion chemistry (1984) for k0 H2O2(+M)=OH+OH(+M) 2.951e+14 0.00 4.843E+04 LOW/1.202E+17 0.00 4.55E+04/ TROE/0.5 1E-30 1E+30/ H2/2.5/ H2O/12/

! Tsang and Hampson, J. Phys. Chem. Ref. Data, 15:1087 (1986) H2O2+H=H2O+OH 0.241E+14 0.00 0.397E+04

! Tsang and Hampson, J. Phys. Chem. Ref. Data, 15:1087 (1986) H2O2+H=HO2+H2 0.482E+14 0.00 0.795E+04

! Tsang and Hampson, J. Phys. Chem. Ref. Data, 15:1087 (1986) H2O2+O=OH+HO2 9.550E+06 2.00 3.970E+03

! Hippler and Troe, J. Chem. Phys. Lett. 192:333 (1992) H2O2+OH=HO2+H2O 1.000E+12 0.00 0.000

DUPLICATE H2O2+OH=HO2+H2O 5.800E+14 0.00 9.557E+03

DUPLICATE

END

Thank you for your advice...

Andrew