### Author Topic: How to reduce the heating values of gases in a combustion simulation?  (Read 4766 times)

#### pitney1

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##### How to reduce the heating values of gases in a combustion simulation?
« on: May 11, 2012, 10:50:17 PM »
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I would like to reduce the heating values of gases in a combustion simulation to represent a low combustion efficiency. How can I modify the NASA coefficients?

#### william

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##### Re: How to reduce the heating values of gases in a combustion simulation?
« Reply #1 on: May 11, 2012, 10:51:00 PM »
The ccl below uses the CEL expression CombEff to adjust the heating values:

LIBRARY:
MATERIAL: Methane Air WD1
Option = Variable Composition Mixture
Reactions List = Methane Air WD1
END # MATERIAL Methane Air WD1
MATERIAL : CH4 # Methane
Option = Pure Substance
PROPERTIES :
Option = Ideal Gas
Molar Mass = 16.04 [kg kmol^-1]
Dynamic Viscosity = 11.1E-06 [kg m^-1 s^-1]
Thermal Conductivity = 343E-04 [W m^-1 K^-1]
Thermal Expansivity = 3.35E-03 [K^-1]
Refractive Index = 1.
Reference Pressure = 1. [atm]
Reference Temperature = 25 [C]
Reference Specific Enthalpy = -74.87310 [kJ mol^-1] / 16.04 [kg kmol^-1]
Reference Specific Entropy = 186.2 [J mol^-1 K^-1] / 16.04 [kg kmol^-1]
SPECIFIC HEAT CAPACITY:
Option = NASA Format
Temperature Limit List = 300 [K], 5000 [K], 1000 [K]
NASA Coefficient List = \
NASACoeff21, NASACoeff22, NASACoeff23, \
NASACoeff24, NASACoeff25, NASACoeff26, \
NASACoeff27, \
NASACoeff11, NASACoeff12, NASACoeff13, \
NASACoeff14, NASACoeff15, NASACoeff16, \
NASACoeff17
END #SPECIFIC HEAT CAPACITY
#
# Boiling point (1 atm) = 111.66 [K]
# Critical Temperature = 190.58 [K]
# Critical Pressure = 4.604E+06 [Pa]
#
END #PROPERTIES
END #MATERIAL

CEL:
EXPRESSIONS:
#
# Combustion of methane: CH4 + 2O2 -> CO2 + 2H2O
#
Rgas = 8314.41 [J kmol^-1]
CombEff = 0.95
HoFCO2 = -393.5224 [kJ mol^-1]
HoFH2O = -241.8264 [kJ mol^-1]
HoFCH4 = -74.8731 [kJ mol^-1]
HeatofProducts = HoFCO2+2*HoFH2O
HeatofReaction = HeatofProducts-HoFCH4
#
# Modify heat of formation ofmethane to account for a
# combustion efficiency of less than 100% using Gordon
# & McBride (NASA) format for enthalpy polynomial
#
HoFCH4Mod = HeatofProducts-CombEff*HeatofReaction
#
NASACoeff11 = 0.07787415E+01
NASACoeff12 = 0.01747668E+00
NASACoeff13 = -0.02783409E-03
NASACoeff14 = 0.03049708E-06
NASACoeff15 = -0.01223931E-09
NASACoeff17 = 0.01372219E+03
Tref1 = 298.15
DHTref11 = NASACoeff11*Tref1 + NASACoeff12*Tref1^2/2 + \
NASACoeff13*Tref1^3/3 + NASACoeff14*Tref1^4/4 + \NASACoeff15*Tref1^5/5
Tref2 = 1000.0
DHTref12 = NASACoeff11*Tref2 + NASACoeff12*Tref2^2/2 + \
NASACoeff13*Tref2^3/3 + NASACoeff14*Tref2^4/4 + \
NASACoeff15*Tref2^5/5
NASACoeff16 = HoFCH4Mod/Rgas-DHTref11
# NASACoeff16 = -0.09825229E+05
#
# High temperature polynomial
#
NASACoeff21 = 0.01683479E+02
NASACoeff22 = 0.01023724E+00
NASACoeff23 = -0.03875129E-04
NASACoeff24 = 0.06785585E-08
NASACoeff25 = -0.04503423E-12
NASACoeff27 = 0.09623395E+02
DHTref22 = NASACoeff21*Tref2 + NASACoeff22*Tref2^2/2 + \
NASACoeff23*Tref2^3/3 + NASACoeff24*Tref2^4/4 + \
NASACoeff25*Tref2^5/5
# Ensure high T and low T polynomials match at Tref2
NASACoeff26 = DHTref12 + NASACoeff16 - DHTref22
# NASACoeff26 = -0.01008079E+06
#
END # EXPRESSIONS
END # CEL
END # LIBRARY

FLOW:

DOMAIN: Combustor
Location = Combustor
Coord Frame = Coord 0
Fluids List = Methane Air WD1
DOMAIN MODELS:
DOMAIN MOTION:
Option = Stationary
END # DOMAIN MOTION
BUOYANCY MODEL:
Option = Non Buoyant
END # BUOYANCY MODEL
REFERENCE PRESSURE:
Reference Pressure = 1.0133E5 [Pa]
END # REFERENCE PRESSURE
END # DOMAIN MODELS

FLUID MODELS:
TURBULENCE MODEL:
Option = k epsilon
END # TURBULENCE MODEL
TURBULENT WALL FUNCTIONS:
Option = Scalable
END # TURBULENT WALL FUNCTIONS
HEAT TRANSFER MODEL:
Option = Thermal Energy
END # HEAT TRANSFER MODEL
COMBUSTION MODEL:
Option = Eddy Dissipation
END # COMBUSTION MODEL
COMPONENT: CH4
Option = Transport Equation
END # COMPONENT CH4
COMPONENT: O2
Option = Transport EquationEND # COMPONENT O2
COMPONENT: CO2
Option = Transport Equation
END # COMPONENT CO2
COMPONENT: H2O
Option = Transport Equation
END # COMPONENT H2O
COMPONENT: N2
Option = Constraint
END # COMPONENT N2
THERMAL RADIATION MODEL:
Option = None
END # THERMAL RADIATION MODEL
END # FLUID MODELS

END # DOMAIN Combustor
END #FLOW