Speed Programming in Matlab/Octave for non computer science engineers

Title :-

staichiometric combustion calculation for alkane,alkene and alkyne fuels using following equation.

Objective :-

Here

n = Number of moles of C

ar = Stoichiometric co-efficient

a = Number of moles of Carbon-di-oxide

b = Number of moles of water

c = Number of moles of nitrogen

Introduction :-

Stoichiometric or Theoretical Combustion is the ideal combustion process where fuel is burned completely.

A complete combustion is a process burning all the carbon (C) to (CO₂), all the hydrogen (H) to (H₂O) and all the sulphur (S) to (SO₂).

With unburned components in the exhaust gas such as C, H₂, CO, the combustion process is uncompleted and not stoichiometric .

The combustion process can be expressed:

[C + H (fuel)] + [O₂ + N₂ (Air)] -> (Combustion Process) -> [CO₂ + H₂O + N₂ (Heat)]

where

C = Carbon

H = Hydrogen

O = Oxygen

N = Nitrogen

To determine the excess air or excess fuel for a combustion system we starts with the stoichiometric air-fuel ratio. The stoichiometric ratio is the perfect ideal fuel ratio where the chemical mixing proportion is correct. When burned all fuel and air is consumed without any excess left over.

Process heating equipment are rarely run that way. "On-ratio" combustion used in boilers and high temperature process furnaces usually incorporates a modest amount of excess air - about 10 to 20% more than what is needed to burn the fuel completely.

If an insufficient amount of air is supplied to the burner, unburned fuel, soot, smoke, and carbon monoxide exhausts from the boiler - resulting in heat transfer surface fouling, pollution, lower combustion efficiency, flame instability and a potential for explosion.

To avoid inefficient and unsafe conditions boilers normally operate at an excess air level. This excess air level also provides protection from insufficient oxygen conditions caused by variations in fuel composition and "operating slops" in the fuel-air control system. Typical values of excess air are indicated for various fuels in the table below.

• if air content is higher than the stoichiometric ratio - the mixture is said to be fuel-lean
• if air content is less than the stoichiometric ratio - the mixture is fuel-rich

Process :-

from the above equation , it eed to be balance the carbon moles and oxygen moles then we can get the relation between stoichiometric coefficient-ar and number of carbon moles in the euation for different types of fuels are Alkane , Alkene and Alkyne.

Alkane fuels :-

Alkene fuel :-

Alkyne fuels :-

By using this formula we can calculate number of carbon moles and ratio to stoichiometric co-efficient Ar

Programe :-

% staichiometric combustion calculation for alkane,alkene and alkyne fuels
close all
clear all
clc

% relation between carbon moles and ar for alkane,alkene,alkyne
x = linspace(1,10,20);
carbon_moles = x ;

% for alkanes
alkane_ar = zeros(1,length(x));
for i = 1:length(x)
    x = i;
    b = ((2*x)+2)/2;
    ar= ((2*x)+b)/2;
    alkane_ar(i) = ar;
end

x = linspace(1,10,20);
carbon_moles = x ;

% for alkenes
alkene_ar = zeros(1,length(x));
for i = 1:length(x)
    x = i;
    b = (2*x)/2;
    ar=((2*x)+b)/2;
    alkene_ar(i) = ar;
end

x = linspace(1,10,20);
carbon_moles = x ;

% for alkynes 
alkynes_ar = zeros(1,length(x));
for i = 1:length(x)
    x = i;
    b = ((2*x)-2)/2;
    ar= ((2*x)+b)/2;
    alkyne_ar(i) = ar;
end 
    
% plotting
figure (1)
plot(carbon_moles,alkane_ar,'color','red');
hold on
plot(carbon_moles,alkene_ar,'color','blue');
hold on
plot(carbon_moles,alkyne_ar,'color','green');
hold off

xlabel('no of carbon_moles');
ylabel('stochiometric co-efficient ar')
legend('alkane','alkene','alkyne')
title('stochiometric combustion result for alkane,alkene,& alkyne fuels')

Output :-