How to solve for three answers from 3 equations using fsolve

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Jcy Juice
Jcy Juice 2022-5-13
评论： Torsten 2022-5-15
I have three equations:
I've attempted to solve them but i am unsure where i am going wromg
%function file
function n = moles(guess)
global NC NH NO NCH4 NCO NCO2 NH2 NH2O
mol1 = guess(1); mol2 = guess(2); mol3 = guess(3);
%equations
n(1) = NCH4 + NCO + NCO2 - NC;
n(2) = NCH4 + NH2 + NH2O - NH;
n(3) = NCO + 2*NCO2 + NH2;
end
%mainfile
%inputs
NC = 10;
NH = 50;
NO = 5
sol = fsolve('assignment1',guess);

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采纳的回答

Davide Masiello
Davide Masiello 2022-5-13
Ran in:
Below, see an example of how to solve the system.
I had to make up the values of the constants since you have not specified them in your question.
clear,clc
% Constants (I made up the values)
molC = 1;
molH = 1;
molO = 1;
T = 600;
molCH4 = 1;
molCO = 1;
molCO2 = 1;
molH2 = 1;
molH2O = 1;
k1 = 1;
k2 = 1;
P = 1;
Po = 1;
% Initial guess
nguess = [2 1 1 3 2];
% Solver
sln = fsolve(@(x)moles(x,molC,molH,molO,T,k1,k2,molCH4,molCO,molCO2,molH2,molH2O,P,Po),nguess)
Equation solved. fsolve completed because the vector of function values is near zero as measured by the value of the function tolerance, and the problem appears regular as measured by the gradient.
sln = 1×5
1.0e-15 * 0.0555 0.0278 0.0278 0.1110 0.0555
% Function
function n = moles(n,molC,molH,molO,T,k1,k2,molCH4,molCO,molCO2,molH2,molH2O,P,Po)
f = [ -n(1) + molCH4 + molCO + molCO2 - molC;...
-n(2) + 4*molCH4 + 2*molH2 + 2*molH2O - molH;...
-n(3) + molCO + 2*molCO2 + molH2;...
-n(4) + 3*log(molH2) + log(molCO) - log(molH2O) - log(molCH4) - log(k1);...
-n(5) + log(molH2) + log(molCO2) - log(molH2O) - log(molCO) - log(k2)
];
end

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