plotting values that comes from a if else loop

I'm having issues with plotting in my if else statements, the PRF it's supposed to cycles through numbers and in the end plot B vs Prf. why is it not plotting Prf ?

clc
clear all
close all



R=287;
Qr=43400000;   %heat reaction value
Pa=187500;     % atmospher
Ta=216.7;    % outside temprature
M=.73;         % mach number
gd=1.4;         %gama

% variables 
%B=5;           %bypass ratio
BArray = 5:1:10; %bypass ratio
for idx = 1:numel(BArray) 
    B = BArray(idx);


To4=1875;      %turbine inlet temperature

%Prf= not given;    %Fan pressure ratio

%Efficiencies and gamma for specific heat
d=.97;            gamad=1.4;            %diffuser
c=.85;            gamac=1.37;           %compressor
b=1;              gamab=1.35;           %burner
t=.9;             gamat=1.33;           %turben 
nz=.98;           gamanz=1.36;          %nozzle
fan=.85;          fangamenz=1.4;        %fan
fan_nozzle=.97;                         %fan nozzle




%flight velocity equation
U=M*sqrt(gd*R*Ta);
%compressor inlet temperature calculation
T0a=Ta*(1+(gamad-1)/2*M^2);
T02=T0a;
%compressor inlet pressure calculation
P02=Pa*(1+d*(T02/Ta-1))^(gd/(gd-1));

%compressor outlet pressure calculation
 

% PrcArray = 7:1:27;% compressor ratio
% for idx = 1:numel(PrcArray) 
    Prc = 24;
        
    
    P03=P02*Prc;
        P04=P03;
        %compressor outlet temperature calculation
        T03=T02*(1+1/c*(Prc^((gamac-1)/gamac)-1));

        %Cp calculations
        Cpb=(gamab/(gamab-1))*R;
        Cpc=(gamac/(gamac-1))*R;
        Cpt=(gamat/(gamat-1))*R;
        %fuel to air flow rate ratio
        f=(To4-T03)/(Qr/Cpb-To4);
        
        %fan pressure ratio
  Prf=1;  % i start with one so i can put in a loop after
        
  
        %fan pressure and temperature calculation
        P08=P02*Prf;
        T08=T02*(1+1/fan*(Prf^((fangamenz-1)/fangamenz)-1));
        %turbine outlet condition calculations
        T05=To4-(T03-T02)-B*(T08-T0a);
        P05=P04*(1-1/t*(1-T05/To4))^(gamat/(gamat-1));
        %nozzle inlet conditions
        P06=P05;
        T06=T05;
        P05==P08;
        

        if P05==P08;
            continue 
        else 
            PrfArray = 1:00001:2; %prf % what i'm trying to plot
        for a = 1:numel(PrfArray) 
    %Prf= PrfArray(a);
            
            
            %for Prf=1:00001:2;
              
              P08=P02*Prf;
        T08=T02*(1+1/fan*(Prf^((fangamenz-1)/fangamenz)-1));
        %turbine outlet condition calculations
        T05=To4-(T03-T02)-B*(T08-T0a);
        P05=P04*(1-1/t*(1-T05/To4))^(gamat/(gamat-1));
        %nozzle inlet conditions
        P06=P05;
        T06=T05;
        Prf= PrfArray(a);
            
            end
        
            
        %exit flight velocities calculations
        Ue=sqrt(2*nz*gamanz/(gamanz-1)*R*T06*(1-(Pa/P06)^((gamanz-1)/gamanz)));
        Uef=sqrt(2*fan_nozzle*fangamenz/(fangamenz-1)*R*T08*(1-(Pa/P08)^((fangamenz-1)/fangamenz)));
        %specific thrust and TSFC calculations
       specthrust(idx) = (1+f)*Ue+B*Uef-(1+B)*U;
       specific_Thrust=max(specthrust);
        %fprintf('your specific thrust is %f', specthrust)
       %format bank
        %disp(num2str(specthrust,'%.0f'))
        TSFC=f./specthrust;
        
        %disp(num2str(TSFC,'%.0f'));
        %overall efficiency calculations
        A=((1+f)*Ue^2/2+B*Uef^2/2-(1+B)*U^2/2);
        ep=specthrust*U/A;
        eth=A/(Qr*f);
        eoa=ep*eth;
        
        end

end
%figure
hold on
u=5:1:10; %bypass

scatter(u,specthrust, 'd','r','filled')
ylabel('Specific Thrsut (kN*s/kg)')
xlabel('ByPass ratio')
%axis([4 12 1400 1800])
grid on
title('ByPass ratio vs Specific Thrust')

figure(2)
scatter(u,TSFC,'d','filled')
ylabel('TSFC')
xlabel('ByPass ratio')
%axis([5 30 200000 230000])
grid on
title('ByPass ratio vs TSFC')

figure(3)
scatter(u,eoa, 'd','g','filled')
ylabel('overall efficiency of the engine')
xlabel('ByPass ratio')
axis([4 12 .21 .26])
grid on
title('ByPass ratio vs overall efficiency of the engine')



figure(4)
scatter(u,Prf, 'd','g','filled')
ylabel('Fan Pressure Ratio')
xlabel('ByPass ratio')
%axis([4 12 .21 .26])
grid on
title('ByPass ratio vs Fan Pressure Ratio')

Answer 1

[Star Strider]

I am not certain what you are doing, so I cannot suggest specific changes.

The ‘Prf’ value plots, however it is a scalar so the result is a horizontal line of green diamonds at 2. (The ‘PrfArray’ vector contains only 2 values anyway.)

The ‘eoa’ plot is blank, however that is because of the axis call. That neds to be changed or removed.

Consider vectorising the code to make it more efficient and easier to read and troubleshoot. See the documentation section on Vectorization for more information.

.

[Jerin Thomas]

apologies for the confusion, correct me if i am wrong here. I thought PrfArray was storing values from each of the itaration to make P05==P08?

the code is supposed to run between 1:.00001:2, so the value of prf can be 1 or 1.2 or 1.2234. Then store these values in ‘PrfArray’

[Star Strider]

No worries!

Unless the code changed from previously (before it was closed), those variables as are I described them.

The for loop only executes when P05 ~= P08 although I did not look closely at all the results, only the variables mentioned in the question.

It always helps to see what the variables are before plotting them (I did just that when I ran the code earlier.)

See the Debugging and Analysis documentation section for help in understanding what the code is actually doing.

I strongly recommend vectorising the code, since that will significantly reduce its complexity and make it easier to read and troubleshoot.

.