Trying to graph two differential equations on same plot

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Rodrigo Blas
Rodrigo Blas 2020-3-19
评论： Rodrigo Blas 2020-3-22
T1=50+273.15; %%k
T2=127+273.15; %%k
Fao=2.5; %%mol/min
P=10; %%atm
k1=10^-4; %%min^-1
R=8.314; %j/k*mol
R1=8.206*10^-5*1000; %%atm*dm^3/K*mol
E=85*1000; %%j/mol
k2=k1*exp(E/R*(1/T1-1/T2)); %%min^-1
cao=P/(T2*R1); %%mol/dm^3
ep=2+1-1;
xf=.90;
alpha=.001; %%dm^3
volcstr=(Fao*xf)*(1+ep*xf)/(k2*cao*(1-xf)); %%dm^3
fun=@(x) Fao/(cao*k2)*(1+ep*x)./(1-x);
volpfr=integral(fun,0,xf); %%dm^3
[x,y]=ode45(@(x,y) jallohwfun7(alpha,ep,xf,y,cao,k2,Fao),[0 500],[0 1]);
plot(x,y(:,1),'r','LineWidth',1);
hold on;
plot(x,y(:,2),'k','LineWidth',1);
legend('Pressure', 'Conversion');
xlabel('Volume [dm^3]');
ylabel('Pressure [atm] & Conversion');
title('Pressure and Conversion vs Volume ');
function dydt=jallohwfun7(alpha,ep,xf,y,cao,k2,Fao)
dydt=zeros(2,1);
dydt(1)=-alpha*(1+ep*xf)/2*y(1);
dydt(2)=k2*cao/Fao*(1-y(2))/(1+ep*y(2));
end
I want to graph two differential equations on same graph however i keep getting a straight line for both equations, which is incorrect.

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采纳的回答

David Goodmanson
David Goodmanson 2020-3-19
Hi Rodrigo,
you have the following:
function dydt=jallohwfun7(alpha,ep,xf,y,cao,k2,Fao)
dydt=zeros(2,1);
dydt(1)=-alpha*(1+ep*xf)/2*y(1);
dydt(2)=k2*cao/Fao*(1-y(2))/(1+ep*y(2));
end
with initial conditions y(1) = 0, y(2) = 1. Plugging those in gives dy/dt(1) = 0, dy/dt(2) = 0 so the system never gets off the schneid. It just stays in the initial state.

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