Determine the combustion efficiency behaviour when a heat recuperator device is involved

Question1

Effect of preheating temperature on adaibatic flame temperature

The below written is the python code to know how adiabatic flame temperature behaviour change with respect to preheating temperature. Here i considered methane as the fuel and calculates AFT at varying preheating temperatures.

1. import cantera and matplot to find attributed and create plots
2. create gas as a variable to store the species data and assagn value to LHV
3. B variable is taken as fuel and quantity class is assaigned to it to find mass and enthalpy at a given temperature,pressure and mass fractions
4. A variable is taken for air and quantity class is assaigned to it to find mass and enthalpy at a given temperature,pressure and mass fractions
5. X are empty arrays where values of Adiabatic Flame temperature at varying preheating temperatures values are stored
6. For loop is created to find AFT at varying pre heating temperature
7. And the heat out and efficiencies are calculated and stored by using append command
8. Plotting of efficiency vs preheating temperature is done

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creating mixtures
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#import cantera as ct becuse we are calculating AFT by using cantera
import cantera as ct
import matplotlib.pyplot as plt # Usedd to create plots

gas=ct.Solution(\"gri30.cti\") # Taking gas properties


B=ct.Quantity(gas)
B.TPX=298.15,ct.one_atm,\'CH4:1546\'
B.moles=1 #assigning moles
X=[] #Creating n array to store AFT
T=[] #creating to store preheating temperature
for  t in range(298,600): #for loop to know AFT at different Preeating temperatures
	A=ct.Quantity(gas)
	A.TPX=t,ct.one_atm,{\'O2\':0.21,\'N2\':0.79}
	A.moles=9.523809524
	M=A+B
	M.equilibrate(\'HP\',\'auto\')
	X.append(M.T)
	T.append(t)
plt.plot(T,X,color=\'red\') #plotting preheating temperature vs Adiabativ=c flame temperature
plt.xlabel(\'Preheating Temperature\')
plt.ylabel(\'Adiabatic Flame Temperature\')
plt.title(\'Effect of preheating temperture on AFT\')
plt.show()

We can observe as the preheating temperature rises simultaneously Adiabatic flame temperature is also rising that is because during combustion time temperature and turbulance plays an major role. Preheated air coming from recuperator already as higher temperature than the staturated temperature do it requires less fuel,less time and complete combustion(More enthalpy) can be acheived. Because of that as preheating temperature rises AFT as rising

Question2

Combustion efficiency

The aim in this problem is to find the behaviour of efficiency with varying preheating temperatures so the above wrtten is the formulae to calculaate the efficiency where Q is the Heat out or simple we can say output and M_fuel is mass of the fuel and LHV is lower heating value which is alredy defined in the problem

To calculate efficiency first step is find out mass and enthalpys of fuel,air and products by calculating mass fractions and then by using cantera find masses and enthalpy

Mass fraction calculation

1. import cantera and matplot to find attributed and create plots
2. create gas as a variable to store the species data and assagn value to LHV
3. B variable is taken as fuel and quantity class is assaigned to it to find mass and enthalpy at a given temperature,pressure and mass fractions
4. C variable is taken as for products and quantity class is assaigned to it to find mass and enthalpy at a given temperature,pressure and mass fractions, unlike reactant product are assagned with exit temperature of 1700K
5. A variable is taken for air and quantity class is assaigned to it to find mass and enthalpy at a given temperature,pressure and mass fractions
6. Q,N are empty arrays where values of heat ,efficiency at varying preheating temperatures values are stored
7. For loop is created to find efficiency at varying pre heating temperature
8. And the heat out and efficiencies are calculated and stored by using append command
9. Plotting of efficiency vs preheating temperature is done

\"\"\"
creating mixtures
\"\"\"
import cantera as ct
import matplotlib.pyplot as plt

gas=ct.Solution(\"gri30.cti\")
LHV=50e6


B=ct.Quantity(gas)
B.TPX=298.15,ct.one_atm,\'CH4:1546\'
B.moles=1
Fuel_mass=B.mass
Fuel_enthalpy=B.enthalpy_mass
print(Fuel_enthalpy)

C=ct.Quantity(gas)
C.TPX=1700,ct.one_atm,{\'CO2\':0.095,\'H2O\':0.190,\'N2\':0.715}

C.moles=10.52
Product_mass=C.mass
Product_enthalpy=C.enthalpy_mass
Q=[]
N=[]
T=[]
for  t in range(298,600):
	A=ct.Quantity(gas)
	A.TPX=t,ct.one_atm,{\'O2\':0.21,\'N2\':0.79}

	A.moles=9.523809524
	Air_mass=A.mass
	Air_enthalpy=A.enthalpy_mass
	q_loss=Air_mass*Air_enthalpy+Fuel_mass*Fuel_enthalpy-Product_mass*Product_enthalpy
	Q.append(q_loss)
	efficiency=(q_loss/(Fuel_mass*LHV))*100
	N.append(efficiency)
	T.append(t)
print(Q)
print(N)

plt.plot(T,N,color=\'red\')
plt.xlabel(\'Preheating Temperature\')
plt.ylabel(\'Efficiency\')
plt.title(\'Effect of preheating temperture on efficiency\')
plt.show()

As we can see rising of preheating temperature leads to rise in efficiency so it is better to use preheated air so that we are using the heat that is lost to improve our efficiency. So greater the preaheating temperature higher woould be the efficiency. Because of that time temperature and turbulance charecteristics are improved by rising passing preheated air inside the furnance

It is better to assume fixed exit furnace temperature ,because even exit temperature effects the efficiency.But as per challege our aim is to find behaviour of efficiency with varying preheater temperature so if we take exit temperature as contant we can find the behaviour of efficiency. But in reality exit furnance temperature vary time to time because of serveral depending factors so if we want results more accuratly it is better to use