IC Engine Simulation, Help with Loops

Goal of the code is to create a simulation to gain a PV diagram of an internal combustion engine. I have code to generate a PV diagram using only air, piston location and engine parameters, (bore, connecting rod length, etc.).

Next step is to add valves.

Assuming: Piston starts at bottom dead center, THETA = 0 Pa = 101 (atmospheric pressure) 4 stroke engine, I tried using this loop:

P = Pa.*Vbdc./Vd;
Pa = 101

    for i=length(THETA)
        if(0 < THETA(i) && THETA(i) <2*pi)
            Pcyl = P;
        elseif(2*pi < THETA(i) && THETA(i) < 4*pi)
            Pcyl = Pa;
        end
    end

plot(THETA,Pcyl)

Am I on the right track of thinking? This does not give a plot, but I'm not sure how else to go about it.

Thank you for your help, MW

[kjetil87]

i didnt check other parts of your code. But the loop will never run more then one time, regardless of what length(THETA) is. Should be for i=1:length(THETA). Also if u want Pcyl to keep one value for each loop counter u need to index it. Pcyl(i)=something. ( if length(THETA) is a big number you should initiate the vector Pcyl before running the loop: Pcyl=zeros(length(THETA),1); <-- this is not a must, but will speed up your loop significantly )

Test this to see what happens to the loop index.

test_vector=[1,2,3,4,5];

for i=length(test_vector) disp(i); end

for i=1:length(test_vector) disp(i) Pcyl(i)=i; end

[kjetil87]

should offcourse be ..disp(i);Pcyl(i)=i;end

(missing semicolon)

Answer 1

[Steve Miller]

Take a look at the documentation for this Simscape Driveline block, Generic Engine.

https://www.mathworks.com/help/sdl/ref/genericengine.html

This block will produce a plot similar to what you are looking for.

--Steve