Week 4 - Combustion Efficiency Calculation after Preheating

The effect of preheating air on AFT of ch4 was calculated.cantera method is used to create the mixture of air and fuel

we used the temparatures Tmin = 289k and Tmax = 600k

from the graph we conclude that Aft increases with increasing air temparature ,so large amount of useful heat energy is available for given fuel.so amount of fuel requried is less hence preheating air helps for fuel saving 

And i uploaded graph as Zip file

code:-

# simple code to vary the temparature of air and oxidiser individually

# i assumed that A = FUEL and B = AIR

import cantera as ct
import matplotlib.pyplot as plt

gas = ct.Solution('gri30.cti')

#CH4+2(o2+3.76N2)=CO2+2H2O+7.52n2

#A = FUEL

A = ct.Quantity(gas)
A.TPX = 298.15,ct.one_atm,'CH4:1'

#B = AIR

B = ct.Quantity(gas)
Tmin = 298 #k
Tmax = 600 #k

plot_interval = 50

for i in range (Tmin,Tmax): #preheating
B.TPX=i,ct.one_atm,{'O2':0.21,'N2':0.79}
B.moles = 9.52

M = A+B
M.equilibrate('HP',"gibbs")
print(M.T)

if i%plot_interval is 0:
plt.plot(i,M.T,'.',color = 'red')

plt.title("effect of preheating on ch4")
plt.xlabel('preheating temparature(air)')
plt.ylabel('AFT')
plt.show()

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# simple code to vary the temparature of air and oxidiser individually

import cantera as ct
import matplotlib.pyplot as plt

gas = ct.Solution('gri30.cti')

#CH4+2(o2+3.76N2)=CO2+2H2O+7.52n2

#FUEL

A = ct.Quantity(gas)
A.TPX = 298.15,ct.one_atm,'CH4:1'
A.moles = 1
mass_A = A.mass

#products
products = ct.Quantity(gas)
products.TPX = 1700,ct.one_atm,{'CO2':0.095,'H2O':0.190,'N2':0.714}
products.moles = 10.52
mass_products = products.mass

#B = AIR

B = ct.Quantity(gas)
Tmin = 298 #k
Tmax = 600 #k
LHV = 50000
plot_interval = 50

for i in range (Tmin,Tmax): #preheating
B.TPX=i,ct.one_atm,{'O2':0.21,'N2':0.79}
B.moles = 9.52
mass_B = B.mass

h_B = B.enthalpy_mass
h_A = A.enthalpy_mass
h_products = products.enthalpy_mass

B_A = mass_B/mass_A

# total heat transfer(Q)
Q =( B_A*h_B) + (h_A) -(B_A+1)*h_products

#EFFICIENCY
efficiency = (Q/LHV)*100

if i%plot_interval is 0:
plt.plot(i,efficiency,'.',color = 'red')

plt.title("effect of preheating on efficiency (ch4)")
plt.xlabel('preheating temparature(air)')
plt.ylabel('efficiency')
plt.grid()
plt.show()

combustion efficiency = efficiency = (Q/LHV)*100

result:

combustion increases with preheated air .if the output T continously increased recuperator may get damage as preheating T depends on T of products .

YeS it is right to fix a furnace exit temparature.