# Ansys CFX problem: unexpected very high temperatures in premix laminar combustion

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Faizan
Join Date: Feb 2016
Posts: 4
Rep Power: 8 Hello everybody,

I am new to the field of combustion CFD. I have used Ansys CFX before but only for non-reacting flows. I am trying to simulate a premix laminar combustion model using Ansys CFX. The model is a simple tube, which I am analyzing as a 2D symmetric part. Inlet velocity is 1 m/s. Inlet Temperature is 298 K. Outlet condition is 1 atm. Mass fractions for methane and oxygen at the inlet are 0.2 and 0.8 respectively. I am using a temperature condition at the walls such that for first few iterations a 2200 K temperature is applied there and then it is switched to 298 K. Also I am using no turbulence model (Laminar) and thermal energy model. For chemistry, I am using Finite rate chemistry (one step).

The problem I am having is that after the solution converges, temperatures in the domain are very unexpectedly high. Maximum temperature is 6138 K. This is wrong as Adiabatic flame temperature for methane combustion is around 2200 K. Can you please help me in this matter? I have attached the image of high temperature contour. and below is the ccl file :
Attached Images high temp.jpg (84.5 KB, 38 views)   February 1, 2016, 07:46 .CCL file part 1 #2 New Member   Faizan Join Date: Feb 2016 Posts: 4 Rep Power: 8 # State file created: 2016/02/01 13:40:57 # Build 16.2 2015.06.30-00.06-134402 LIBRARY: CEL: EXPRESSIONS: temp cond = if(aitern<50,2200[K],298[K]) END END MATERIAL GROUP: Air Data Group Description = Ideal gas and constant property air. Constant \ properties are for dry air at STP (0 C, 1 atm) and 25 C, 1 atm. END MATERIAL GROUP: CHT Solids Group Description = Pure solid substances that can be used for conjugate \ heat transfer. END MATERIAL GROUP: Calorically Perfect Ideal Gases Group Description = Ideal gases with constant specific heat capacity. \ Specific heat is evaluated at STP. END MATERIAL GROUP: Constant Property Gases Group Description = Gaseous substances with constant properties. \ Properties are calculated at STP (0C and 1 atm). Can be combined with \ NASA SP-273 materials for combustion modelling. END MATERIAL GROUP: Constant Property Liquids Group Description = Liquid substances with constant properties. END MATERIAL GROUP: Dry Peng Robinson Group Description = Materials with properties specified using the built \ in Peng Robinson equation of state. Suitable for dry real gas modelling. END MATERIAL GROUP: Dry Redlich Kwong Group Description = Materials with properties specified using the built \ in Redlich Kwong equation of state. Suitable for dry real gas modelling. END MATERIAL GROUP: Dry Soave Redlich Kwong Group Description = Materials with properties specified using the built \ in Soave Redlich Kwong equation of state. Suitable for dry real gas \ modelling. END MATERIAL GROUP: Dry Steam Group Description = Materials with properties specified using the IAPWS \ equation of state. Suitable for dry steam modelling. END MATERIAL GROUP: Gas Phase Combustion Group Description = Ideal gas materials which can be use for gas phase \ combustion. Ideal gas specific heat coefficients are specified using \ the NASA SP-273 format. END MATERIAL GROUP: IAPWS IF97 Group Description = Liquid, vapour and binary mixture materials which use \ the IAPWS IF-97 equation of state. Materials are suitable for \ compressible liquids, phase change calculations and dry steam flows. END MATERIAL GROUP: Interphase Mass Transfer Group Description = Materials with reference properties suitable for \ performing either Eulerian or Lagrangian multiphase mass transfer \ problems. Examples include cavitation, evaporation or condensation. END MATERIAL GROUP: Liquid Phase Combustion Group Description = Liquid and homogenous binary mixture materials which \ can be included with Gas Phase Combustion materials if combustion \ modelling also requires phase change (eg: evaporation) for certain \ components. END MATERIAL GROUP: Particle Solids Group Description = Pure solid substances that can be used for particle \ tracking END MATERIAL GROUP: Peng Robinson Dry Hydrocarbons Group Description = Common hydrocarbons which use the Peng Robinson \ equation of state. Suitable for dry real gas models. END MATERIAL GROUP: Peng Robinson Dry Refrigerants Group Description = Common refrigerants which use the Peng Robinson \ equation of state. Suitable for dry real gas models. END MATERIAL GROUP: Peng Robinson Dry Steam Group Description = Water materials which use the Peng Robinson equation \ of state. Suitable for dry steam modelling. END MATERIAL GROUP: Peng Robinson Wet Hydrocarbons Group Description = Common hydrocarbons which use the Peng Robinson \ equation of state. Suitable for condensing real gas models. END MATERIAL GROUP: Peng Robinson Wet Refrigerants Group Description = Common refrigerants which use the Peng Robinson \ equation of state. Suitable for condensing real gas models. END MATERIAL GROUP: Peng Robinson Wet Steam Group Description = Water materials which use the Peng Robinson equation \ of state. Suitable for condensing steam modelling. END MATERIAL GROUP: Real Gas Combustion Group Description = Real gas materials which can be use for gas phase \ combustion. Ideal gas specific heat coefficients are specified using \ the NASA SP-273 format. END MATERIAL GROUP: Redlich Kwong Dry Hydrocarbons Group Description = Common hydrocarbons which use the Redlich Kwong \ equation of state. Suitable for dry real gas models. END MATERIAL GROUP: Redlich Kwong Dry Refrigerants Group Description = Common refrigerants which use the Redlich Kwong \ equation of state. Suitable for dry real gas models. END MATERIAL GROUP: Redlich Kwong Dry Steam Group Description = Water materials which use the Redlich Kwong equation \ of state. Suitable for dry steam modelling. END MATERIAL GROUP: Redlich Kwong Wet Hydrocarbons Group Description = Common hydrocarbons which use the Redlich Kwong \ equation of state. Suitable for condensing real gas models. END MATERIAL GROUP: Redlich Kwong Wet Refrigerants Group Description = Common refrigerants which use the Redlich Kwong \ equation of state. Suitable for condensing real gas models. END MATERIAL GROUP: Redlich Kwong Wet Steam Group Description = Water materials which use the Redlich Kwong equation \ of state. Suitable for condensing steam modelling. END MATERIAL GROUP: Soave Redlich Kwong Dry Hydrocarbons Group Description = Common hydrocarbons which use the Soave Redlich Kwong \ equation of state. Suitable for dry real gas models. END MATERIAL GROUP: Soave Redlich Kwong Dry Refrigerants Group Description = Common refrigerants which use the Soave Redlich Kwong \ equation of state. Suitable for dry real gas models. END MATERIAL GROUP: Soave Redlich Kwong Dry Steam Group Description = Water materials which use the Soave Redlich Kwong \ equation of state. Suitable for dry steam modelling. END MATERIAL GROUP: Soave Redlich Kwong Wet Hydrocarbons Group Description = Common hydrocarbons which use the Soave Redlich Kwong \ equation of state. Suitable for condensing real gas models. END MATERIAL GROUP: Soave Redlich Kwong Wet Refrigerants Group Description = Common refrigerants which use the Soave Redlich Kwong \ equation of state. Suitable for condensing real gas models. END MATERIAL GROUP: Soave Redlich Kwong Wet Steam Group Description = Water materials which use the Soave Redlich Kwong \ equation of state. Suitable for condensing steam modelling. END MATERIAL GROUP: Soot Group Description = Solid substances that can be used when performing \ soot modelling END MATERIAL GROUP: User Group Description = Materials that are defined by the user END MATERIAL GROUP: Water Data Group Description = Liquid and vapour water materials with constant \ properties. Can be combined with NASA SP-273 materials for combustion \ modelling. END MATERIAL GROUP: Wet Peng Robinson Group Description = Materials with properties specified using the built \ in Peng Robinson equation of state. Suitable for wet real gas modelling. END MATERIAL GROUP: Wet Redlich Kwong Group Description = Materials with properties specified using the built \ in Redlich Kwong equation of state. Suitable for wet real gas modelling. END MATERIAL GROUP: Wet Soave Redlich Kwong Group Description = Materials with properties specified using the built \ in Soave Redlich Kwong equation of state. Suitable for wet real gas \ modelling. END MATERIAL GROUP: Wet Steam Group Description = Materials with properties specified using the IAPWS \ equation of state. Suitable for wet steam modelling. END MATERIAL: Air Ideal Gas Material Description = Air Ideal Gas (constant Cp) Material Group = Air Data, Calorically Perfect Ideal Gases Option = Pure Substance Thermodynamic State = Gas PROPERTIES: Option = General Material EQUATION OF STATE: Molar Mass = 28.96 [kg kmol^-1] Option = Ideal Gas END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = 1.0044E+03 [J kg^-1 K^-1] Specific Heat Type = Constant Pressure END REFERENCE STATE: Option = Specified Point Reference Pressure = 1 [atm] Reference Specific Enthalpy = 0. [J/kg] Reference Specific Entropy = 0. [J/kg/K] Reference Temperature = 25 [C] END DYNAMIC VISCOSITY: Dynamic Viscosity = 1.831E-05 [kg m^-1 s^-1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 2.61E-2 [W m^-1 K^-1] END ABSORPTION COEFFICIENT: Absorption Coefficient = 0.01 [m^-1] Option = Value END SCATTERING COEFFICIENT: Option = Value Scattering Coefficient = 0.0 [m^-1] END REFRACTIVE INDEX: Option = Value Refractive Index = 1.0 [m m^-1] END END END MATERIAL: Air at 25 C Material Description = Air at 25 C and 1 atm (dry) Material Group = Air Data, Constant Property Gases Option = Pure Substance Thermodynamic State = Gas PROPERTIES: Option = General Material EQUATION OF STATE: Density = 1.185 [kg m^-3] Molar Mass = 28.96 [kg kmol^-1] Option = Value END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = 1.0044E+03 [J kg^-1 K^-1] Specific Heat Type = Constant Pressure END REFERENCE STATE: Option = Specified Point Reference Pressure = 1 [atm] Reference Specific Enthalpy = 0. [J/kg] Reference Specific Entropy = 0. [J/kg/K] Reference Temperature = 25 [C] END DYNAMIC VISCOSITY: Dynamic Viscosity = 1.831E-05 [kg m^-1 s^-1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 2.61E-02 [W m^-1 K^-1] END ABSORPTION COEFFICIENT: Absorption Coefficient = 0.01 [m^-1] Option = Value END SCATTERING COEFFICIENT: Option = Value Scattering Coefficient = 0.0 [m^-1] END REFRACTIVE INDEX: Option = Value Refractive Index = 1.0 [m m^-1] END THERMAL EXPANSIVITY: Option = Value Thermal Expansivity = 0.003356 [K^-1] END END END MATERIAL: Aluminium Material Group = CHT Solids, Particle Solids Option = Pure Substance Thermodynamic State = Solid PROPERTIES: Option = General Material EQUATION OF STATE: Density = 2702 [kg m^-3] Molar Mass = 26.98 [kg kmol^-1] Option = Value END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = 9.03E+02 [J kg^-1 K^-1] END REFERENCE STATE: Option = Specified Point Reference Specific Enthalpy = 0 [J/kg] Reference Specific Entropy = 0 [J/kg/K] Reference Temperature = 25 [C] END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 237 [W m^-1 K^-1] END END END MATERIAL: CH4 Material Description = Methane CH4 Material Group = Gas Phase Combustion Option = Pure Substance Thermodynamic State = Gas PROPERTIES: Option = General Material EQUATION OF STATE: Molar Mass = 16.04 [kg kmol^-1] Option = Ideal Gas END SPECIFIC HEAT CAPACITY: Option = NASA Format LOWER INTERVAL COEFFICIENTS: NASA a1 = 0.07787415E+01 [] NASA a2 = 0.01747668E+00 [K^-1] NASA a3 = -0.02783409E-03 [K^-2] NASA a4 = 0.03049708E-06 [K^-3] NASA a5 = -0.01223931E-09 [K^-4] NASA a6 = -0.09825229E+05 [K] NASA a7 = 0.01372219E+03 [] END TEMPERATURE LIMITS: Lower Temperature = 300 [K] Midpoint Temperature = 1000 [K] Upper Temperature = 5000 [K] END UPPER INTERVAL COEFFICIENTS: NASA a1 = 0.01683479E+02 [] NASA a2 = 0.01023724E+00 [K^-1] NASA a3 = -0.03875129E-04 [K^-2] NASA a4 = 0.06785585E-08 [K^-3] NASA a5 = -0.04503423E-12 [K^-4] NASA a6 = -0.01008079E+06 [K] NASA a7 = 0.09623395E+02 [] END END REFERENCE STATE: Option = NASA Format Reference Pressure = 1 [atm] Reference Temperature = 25 [C] END DYNAMIC VISCOSITY: Dynamic Viscosity = 11.1E-06 [kg m^-1 s^-1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 343E-04 [W m^-1 K^-1] END ABSORPTION COEFFICIENT: Absorption Coefficient = 1.0 [m^-1] Option = Value END SCATTERING COEFFICIENT: Option = Value Scattering Coefficient = 0.0 [m^-1] END REFRACTIVE INDEX: Option = Value Refractive Index = 1.0 [m m^-1] END END END MATERIAL: CO Material Description = Carbon Monoxide CO Material Group = Gas Phase Combustion Option = Pure Substance Thermodynamic State = Gas PROPERTIES: Option = General Material EQUATION OF STATE: Molar Mass = 28.01 [kg kmol^-1] Option = Ideal Gas END SPECIFIC HEAT CAPACITY: Option = NASA Format LOWER INTERVAL COEFFICIENTS: NASA a1 = 0.03262452E+02 [] NASA a2 = 0.01511941E-01 [K^-1] NASA a3 = -0.03881755E-04 [K^-2] NASA a4 = 0.05581944E-07 [K^-3] NASA a5 = -0.02474951E-10 [K^-4] NASA a6 = -0.01431054E+06 [K] NASA a7 = 0.04848897E+02 [] END TEMPERATURE LIMITS: Lower Temperature = 300 [K] Midpoint Temperature = 1000 [K] Upper Temperature = 5000 [K] END UPPER INTERVAL COEFFICIENTS: NASA a1 = 0.03025078E+02 [] NASA a2 = 0.01442689E-01 [K^-1] NASA a3 = -0.05630828E-05 [K^-2] NASA a4 = 0.01018581E-08 [K^-3] NASA a5 = -0.06910952E-13 [K^-4] NASA a6 = -0.01426835E+06 [K] NASA a7 = 0.06108218E+02 [] END END REFERENCE STATE: Option = NASA Format Reference Pressure = 1 [atm] Reference Temperature = 25 [C] END DYNAMIC VISCOSITY: Dynamic Viscosity = 16.6E-06 [kg m^-1 s^-1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 251E-04 [W m^-1 K^-1] END ABSORPTION COEFFICIENT: Absorption Coefficient = 1.0 [m^-1] Option = Value END SCATTERING COEFFICIENT: Option = Value Scattering Coefficient = 0.0 [m^-1] END REFRACTIVE INDEX: Option = Value Refractive Index = 1.0 [m m^-1] END END END MATERIAL: CO2 Material Description = Carbon Dioxide CO2 Material Group = Gas Phase Combustion Option = Pure Substance Thermodynamic State = Gas PROPERTIES: Option = General Material EQUATION OF STATE: Molar Mass = 44.01 [kg kmol^-1] Option = Ideal Gas END SPECIFIC HEAT CAPACITY: Option = NASA Format LOWER INTERVAL COEFFICIENTS: NASA a1 = 0.02275725E+02 [] NASA a2 = 0.09922072E-01 [K^-1] NASA a3 = -0.01040911E-03 [K^-2] NASA a4 = 0.06866687E-07 [K^-3] NASA a5 = -0.02117280E-10 [K^-4] NASA a6 = -0.04837314E+06 [K] NASA a7 = 0.01018849E+03 [] END TEMPERATURE LIMITS: Lower Temperature = 300 [K] Midpoint Temperature = 1000 [K] Upper Temperature = 5000 [K] END UPPER INTERVAL COEFFICIENTS: NASA a1 = 0.04453623E+02 [] NASA a2 = 0.03140169E-01 [K^-1] NASA a3 = -0.01278411E-04 [K^-2] NASA a4 = 0.02393997E-08 [K^-3] NASA a5 = -0.01669033E-12 [K^-4] NASA a6 = -0.04896696E+06 [K] NASA a7 = -0.09553959E+01 [] END END REFERENCE STATE: Option = NASA Format Reference Pressure = 1 [atm] Reference Temperature = 25 [C] END DYNAMIC VISCOSITY: Dynamic Viscosity = 14.9E-06 [kg m^-1 s^-1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 145E-04 [W m^-1 K^-1] END ABSORPTION COEFFICIENT: Absorption Coefficient = 1.0 [m^-1] Option = Value END SCATTERING COEFFICIENT: Option = Value Scattering Coefficient = 0.0 [m^-1] END REFRACTIVE INDEX: Option = Value Refractive Index = 1.0 [m m^-1] END END END   February 1, 2016, 07:47 .ccl part 2 #3 New Member   Faizan Join Date: Feb 2016 Posts: 4 Rep Power: 8 MATERIAL: Copper Material Group = CHT Solids, Particle Solids Option = Pure Substance Thermodynamic State = Solid PROPERTIES: Option = General Material EQUATION OF STATE: Density = 8933 [kg m^-3] Molar Mass = 63.55 [kg kmol^-1] Option = Value END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = 3.85E+02 [J kg^-1 K^-1] END REFERENCE STATE: Option = Specified Point Reference Specific Enthalpy = 0 [J/kg] Reference Specific Entropy = 0 [J/kg/K] Reference Temperature = 25 [C] END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 401.0 [W m^-1 K^-1] END END END MATERIAL: H2 Material Description = Hydrogen H2 Material Group = Gas Phase Combustion Option = Pure Substance Thermodynamic State = Gas PROPERTIES: Option = General Material EQUATION OF STATE: Molar Mass = 2.016 [kg kmol^-1] Option = Ideal Gas END SPECIFIC HEAT CAPACITY: Option = NASA Format LOWER INTERVAL COEFFICIENTS: NASA a1 = 0.03298124E+02 [] NASA a2 = 0.08249442E-02 [K^-1] NASA a3 = -0.08143015E-05 [K^-2] NASA a4 = -0.09475434E-09 [K^-3] NASA a5 = 0.04134872E-11 [K^-4] NASA a6 = -0.01012521E+05 [K] NASA a7 = -0.03294094E+02 [] END TEMPERATURE LIMITS: Lower Temperature = 300 [K] Midpoint Temperature = 1000 [K] Upper Temperature = 5000 [K] END UPPER INTERVAL COEFFICIENTS: NASA a1 = 0.02991423E+02 [] NASA a2 = 0.07000644E-02 [K^-1] NASA a3 = -0.05633829E-06 [K^-2] NASA a4 = -0.09231578E-10 [K^-3] NASA a5 = 0.01582752E-13 [K^-4] NASA a6 = -0.08350340E+04 [K] NASA a7 = -0.01355110E+02 [] END END REFERENCE STATE: Option = NASA Format Reference Pressure = 1 [atm] Reference Temperature = 25 [C] END DYNAMIC VISCOSITY: Dynamic Viscosity = 8.8E-06 [kg m^-1 s^-1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 1.809E-01 [W m^-1 K^-1] END ABSORPTION COEFFICIENT: Absorption Coefficient = 1.0 [m^-1] Option = Value END SCATTERING COEFFICIENT: Option = Value Scattering Coefficient = 0.0 [m^-1] END REFRACTIVE INDEX: Option = Value Refractive Index = 1.0 [m m^-1] END END END MATERIAL: H2O Material Description = Water Vapour Material Group = Gas Phase Combustion, Interphase Mass Transfer, Water Data Option = Pure Substance Thermodynamic State = Gas PROPERTIES: Option = General Material EQUATION OF STATE: Molar Mass = 18.02 [kg kmol^-1] Option = Ideal Gas END SPECIFIC HEAT CAPACITY: Option = NASA Format LOWER INTERVAL COEFFICIENTS: NASA a1 = 0.03386842E+02 [] NASA a2 = 0.03474982E-01 [K^-1] NASA a3 = -0.06354696E-04 [K^-2] NASA a4 = 0.06968581E-07 [K^-3] NASA a5 = -0.02506588E-10 [K^-4] NASA a6 = -0.03020811E+06 [K] NASA a7 = 0.02590233E+02 [] END TEMPERATURE LIMITS: Lower Temperature = 300 [K] Midpoint Temperature = 1000 [K] Upper Temperature = 5000 [K] END UPPER INTERVAL COEFFICIENTS: NASA a1 = 0.02672146E+02 [] NASA a2 = 0.03056293E-01 [K^-1] NASA a3 = -0.08730260E-05 [K^-2] NASA a4 = 0.01200996E-08 [K^-3] NASA a5 = -0.06391618E-13 [K^-4] NASA a6 = -0.02989921E+06 [K] NASA a7 = 0.06862817E+02 [] END END REFERENCE STATE: Option = NASA Format Reference Pressure = 1 [atm] Reference Temperature = 25 [C] END DYNAMIC VISCOSITY: Dynamic Viscosity = 9.4E-06 [kg m^-1 s^-1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 193E-04 [W m^-1 K^-1] END ABSORPTION COEFFICIENT: Absorption Coefficient = 1.0 [m^-1] Option = Value END SCATTERING COEFFICIENT: Option = Value Scattering Coefficient = 0.0 [m^-1] END REFRACTIVE INDEX: Option = Value Refractive Index = 1.0 [m m^-1] END END END MATERIAL: N2 Material Description = Nitrogen N2 Material Group = Gas Phase Combustion Option = Pure Substance Thermodynamic State = Gas PROPERTIES: Option = General Material EQUATION OF STATE: Molar Mass = 28.01 [kg kmol^-1] Option = Ideal Gas END SPECIFIC HEAT CAPACITY: Option = NASA Format LOWER INTERVAL COEFFICIENTS: NASA a1 = 0.03298677E+02 [] NASA a2 = 0.01408240E-01 [K^-1] NASA a3 = -0.03963222E-04 [K^-2] NASA a4 = 0.05641515E-07 [K^-3] NASA a5 = -0.02444855E-10 [K^-4] NASA a6 = -0.01020900E+05 [K] NASA a7 = 0.03950372E+02 [] END TEMPERATURE LIMITS: Lower Temperature = 300 [K] Midpoint Temperature = 1000 [K] Upper Temperature = 5000 [K] END UPPER INTERVAL COEFFICIENTS: NASA a1 = 0.02926640E+02 [] NASA a2 = 0.01487977E-01 [K^-1] NASA a3 = -0.05684761E-05 [K^-2] NASA a4 = 0.01009704E-08 [K^-3] NASA a5 = -0.06753351E-13 [K^-4] NASA a6 = -0.09227977E+04 [K] NASA a7 = 0.05980528E+02 [] END END REFERENCE STATE: Option = NASA Format Reference Pressure = 1 [atm] Reference Temperature = 25 [C] END DYNAMIC VISCOSITY: Dynamic Viscosity = 17.7E-06 [kg m^-1 s^-1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 259E-04 [W m^-1 K^-1] END ABSORPTION COEFFICIENT: Absorption Coefficient = 1.0 [m^-1] Option = Value END SCATTERING COEFFICIENT: Option = Value Scattering Coefficient = 0.0 [m^-1] END REFRACTIVE INDEX: Option = Value Refractive Index = 1.0 [m m^-1] END END END MATERIAL: O2 Material Description = Oxygen O2 Material Group = Gas Phase Combustion Option = Pure Substance Thermodynamic State = Gas PROPERTIES: Option = General Material EQUATION OF STATE: Molar Mass = 31.99 [kg kmol^-1] Option = Ideal Gas END SPECIFIC HEAT CAPACITY: Option = NASA Format LOWER INTERVAL COEFFICIENTS: NASA a1 = 0.03212936E+02 [] NASA a2 = 0.01127486E-01 [K^-1] NASA a3 = -0.05756150E-05 [K^-2] NASA a4 = 0.01313877E-07 [K^-3] NASA a5 = -0.08768554E-11 [K^-4] NASA a6 = -0.01005249E+05 [K] NASA a7 = 0.06034738E+02 [] END TEMPERATURE LIMITS: Lower Temperature = 300 [K] Midpoint Temperature = 1000 [K] Upper Temperature = 5000 [K] END UPPER INTERVAL COEFFICIENTS: NASA a1 = 0.03697578E+02 [] NASA a2 = 0.06135197E-02 [K^-1] NASA a3 = -0.01258842E-05 [K^-2] NASA a4 = 0.01775281E-09 [K^-3] NASA a5 = -0.01136435E-13 [K^-4] NASA a6 = -0.01233930E+05 [K] NASA a7 = 0.03189166E+02 [] END END REFERENCE STATE: Option = NASA Format Reference Pressure = 1 [atm] Reference Temperature = 25 [C] END DYNAMIC VISCOSITY: Dynamic Viscosity = 19.2E-06 [kg m^-1 s^-1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 266E-04 [W m^-1 K^-1] END ABSORPTION COEFFICIENT: Absorption Coefficient = 1.0 [m^-1] Option = Value END SCATTERING COEFFICIENT: Option = Value Scattering Coefficient = 0.0 [m^-1] END REFRACTIVE INDEX: Option = Value Refractive Index = 1.0 [m m^-1] END END END MATERIAL: Soot Material Group = Soot Option = Pure Substance Thermodynamic State = Solid PROPERTIES: Option = General Material EQUATION OF STATE: Density = 2000 [kg m^-3] Molar Mass = 12 [kg kmol^-1] Option = Value END REFERENCE STATE: Option = Automatic END ABSORPTION COEFFICIENT: Absorption Coefficient = 0 [m^-1] Option = Value END END END MATERIAL: Steel Material Group = CHT Solids, Particle Solids Option = Pure Substance Thermodynamic State = Solid PROPERTIES: Option = General Material EQUATION OF STATE: Density = 7854 [kg m^-3] Molar Mass = 55.85 [kg kmol^-1] Option = Value END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = 4.34E+02 [J kg^-1 K^-1] END REFERENCE STATE: Option = Specified Point Reference Specific Enthalpy = 0 [J/kg] Reference Specific Entropy = 0 [J/kg/K] Reference Temperature = 25 [C] END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 60.5 [W m^-1 K^-1] END END END MATERIAL: Water Material Description = Water (liquid) Material Group = Water Data, Constant Property Liquids Option = Pure Substance Thermodynamic State = Liquid PROPERTIES: Option = General Material EQUATION OF STATE: Density = 997.0 [kg m^-3] Molar Mass = 18.02 [kg kmol^-1] Option = Value END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = 4181.7 [J kg^-1 K^-1] Specific Heat Type = Constant Pressure END REFERENCE STATE: Option = Specified Point Reference Pressure = 1 [atm] Reference Specific Enthalpy = 0.0 [J/kg] Reference Specific Entropy = 0.0 [J/kg/K] Reference Temperature = 25 [C] END DYNAMIC VISCOSITY: Dynamic Viscosity = 8.899E-4 [kg m^-1 s^-1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 0.6069 [W m^-1 K^-1] END ABSORPTION COEFFICIENT: Absorption Coefficient = 1.0 [m^-1] Option = Value END SCATTERING COEFFICIENT: Option = Value Scattering Coefficient = 0.0 [m^-1] END REFRACTIVE INDEX: Option = Value Refractive Index = 1.0 [m m^-1] END THERMAL EXPANSIVITY: Option = Value Thermal Expansivity = 2.57E-04 [K^-1] END END END MATERIAL: Water Ideal Gas Material Description = Water Vapour Ideal Gas (100 C and 1 atm) Material Group = Calorically Perfect Ideal Gases, Water Data Option = Pure Substance Thermodynamic State = Gas PROPERTIES: Option = General Material EQUATION OF STATE: Molar Mass = 18.02 [kg kmol^-1] Option = Ideal Gas END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = 2080.1 [J kg^-1 K^-1] Specific Heat Type = Constant Pressure END REFERENCE STATE: Option = Specified Point Reference Pressure = 1.014 [bar] Reference Specific Enthalpy = 0. [J/kg] Reference Specific Entropy = 0. [J/kg/K] Reference Temperature = 100 [C] END DYNAMIC VISCOSITY: Dynamic Viscosity = 9.4E-06 [kg m^-1 s^-1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 193E-04 [W m^-1 K^-1] END ABSORPTION COEFFICIENT: Absorption Coefficient = 1.0 [m^-1] Option = Value END SCATTERING COEFFICIENT: Option = Value Scattering Coefficient = 0.0 [m^-1] END REFRACTIVE INDEX: Option = Value Refractive Index = 1.0 [m m^-1] END END END REACTION: Methane Air WD1 Additional Materials List = CH4,O2,CO2,H2O Option = Multi Step Reaction Description = Methane Air Single Step Reactions List = Methane Oxygen WD1 END REACTION: Methane Oxygen WD1 Option = Single Step FORWARD REACTION RATE: Option = Arrhenius Pre Exponential Factor = 8.3E6 [s^-1] Temperature Exponent = 0. REACTION ACTIVATION: Activation Energy = 30. [kcal mol^-1] Option = Activation Energy END END PRODUCTS: Materials List = CO2,H2O Option = Child Materials CHILD MATERIAL: CO2 Option = Stoichiometric Stoichiometric Coefficient = 1.0 END CHILD MATERIAL: H2O Option = Stoichiometric Stoichiometric Coefficient = 2.0 END END REACTANTS: Materials List = CH4,O2 Option = Child Materials CHILD MATERIAL: CH4 Option = Stoichiometric Reaction Order = -0.3 Stoichiometric Coefficient = 1.0 END CHILD MATERIAL: O2 Option = Stoichiometric Reaction Order = 1.3 Stoichiometric Coefficient = 2.0 END END END END FLOW: Flow Analysis 1 SOLUTION UNITS: Angle Units = [rad] Length Units = [m] Mass Units = [kg] Solid Angle Units = [sr] Temperature Units = [K] Time Units = [s] END ANALYSIS TYPE: Option = Steady State EXTERNAL SOLVER COUPLING: Option = None END END DOMAIN: Default Domain Coord Frame = Coord 0 Domain Type = Fluid Location = B16 BOUNDARY: Boundary 1 Boundary Type = SYMMETRY Location = F17.16,F18.16 END BOUNDARY: inlet Boundary Type = INLET Location = F22.16 BOUNDARY CONDITIONS: COMPONENT: CH4 Mass Fraction = 0.2 Option = Mass Fraction END COMPONENT: CO2 Mass Fraction = 0.0 Option = Mass Fraction END COMPONENT: O2 Mass Fraction = 0.8 Option = Mass Fraction END FLOW REGIME: Option = Subsonic END HEAT TRANSFER: Option = Static Temperature Static Temperature = 298 [K] END MASS AND MOMENTUM: Normal Speed = 1 [m s^-1] Option = Normal Speed END END END BOUNDARY: outlet Boundary Type = OUTLET Location = F20.16 BOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END MASS AND MOMENTUM: Option = Static Pressure Relative Pressure = 1 [atm] END END END BOUNDARY: top wall Boundary Type = WALL Location = F19.16,F21.16 BOUNDARY CONDITIONS: HEAT TRANSFER: Fixed Temperature = temp cond Option = Fixed Temperature END MASS AND MOMENTUM: Option = No Slip Wall END END END DOMAIN MODELS: BUOYANCY MODEL: Option = Non Buoyant END DOMAIN MOTION: Option = Stationary END MESH DEFORMATION: Option = None END REFERENCE PRESSURE: Reference Pressure = 0 [atm] END END FLUID DEFINITION: mix Option = Material Definition MATERIAL DEFINITION: Option = Reacting Mixture END MORPHOLOGY: Option = Continuous Fluid END END FLUID MODELS: COMBUSTION MODEL: Option = Finite Rate Chemistry Reactions List = Methane Air WD1 END COMPONENT: CH4 Option = Transport Equation END COMPONENT: CO2 Option = Transport Equation END COMPONENT: H2O Option = Constraint END COMPONENT: O2 Option = Transport Equation END HEAT TRANSFER MODEL: Include Viscous Dissipation Term = Off Option = Thermal Energy END THERMAL RADIATION MODEL: Option = None END TURBULENCE MODEL: Option = Laminar END END END INITIALISATION: Option = Automatic INITIAL CONDITIONS: Velocity Type = Cartesian CARTESIAN VELOCITY COMPONENTS: Option = Automatic END COMPONENT: CH4 Option = Automatic END COMPONENT: CO2 Option = Automatic END COMPONENT: O2 Option = Automatic END STATIC PRESSURE: Option = Automatic END TEMPERATURE: Option = Automatic with Value Temperature = 1500 [K] END END END OUTPUT CONTROL: MONITOR OBJECTS: MONITOR BALANCES: Option = Full END MONITOR FORCES: Option = Full END MONITOR PARTICLES: Option = Full END MONITOR POINT: recirculation zone temp Cartesian Coordinates = 0.005 [m], 0.0005 [m], 0 [m] Coord Frame = Coord 0 Option = Cartesian Coordinates Output Variables List = Temperature MONITOR LOCATION CONTROL: Interpolation Type = Nearest Vertex END POSITION UPDATE FREQUENCY: Option = Initial Mesh Only END END MONITOR RESIDUALS: Option = Full END MONITOR TOTALS: Option = Full END END RESULTS: File Compression Level = Default Option = Standard END END SOLVER CONTROL: ADVECTION SCHEME: Option = High Resolution END CONVERGENCE CONTROL: Length Scale Option = Conservative Maximum Number of Iterations = 100 Minimum Number of Iterations = 1 Timescale Control = Auto Timescale Timescale Factor = 1.0 END CONVERGENCE CRITERIA: Conservation Target = 0.001 Residual Target = 1e-06 Residual Type = RMS END DYNAMIC MODEL CONTROL: Global Dynamic Model Control = Yes END MCF ENERGY DIFFUSION: Option = Unity Lewis Number END END END COMMAND FILE: Version = 16.2 END   February 1, 2016, 16:02 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,170 Rep Power: 134    Have you seen this FAQ? http://www.cfd-online.com/Wiki/Ansys...hemistry_model Also: You do not appear to have a radiation model. Isn't this important at these temperatures?   February 1, 2016, 17:00 #5 Senior Member   Join Date: Jun 2009 Posts: 1,575 Rep Power: 28 May I ask how you computed the adiabatic flame temperature for the specific case you are solving ? The adiabatic flame temperature is not a universal value though many engineers take it as such because it refers to a standard condition in their minds. If by any chance you are referring to results computed by some chemical equilibrium codes, there is the first problem. Those codes usually refer to air-methane (while you are doing oxygen-methane only); therefore, the presence of N2 drops the adiabatic temperature considerably. I think 6000+ [K] is still high, but if the solution converged, the adiabatic flame temperature is determined by pure thermodynamics, i.e. enthalpy balances and not CFD. What are the conditions for the adiabatic flame temperature value you are reporting ? Are there other species for such conditions ? Hope the above helps,  Tags cfs, high temperature problem, laminar, premix Thread Tools Search this Thread Show Printable Version Email this Page Search this Thread: Advanced Search Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are On Refbacks are On Forum Rules Similar Threads Thread Thread Starter Forum Replies Last Post loth ANSYS 3 December 24, 2015 05:31 Stephen Lau CFX 1 April 18, 2007 03:02 zyf CFX 3 October 7, 2006 03:08 Bi Chang CFX 2 May 10, 2005 04:47 Andrea CFX 2 October 11, 2004 05:12

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