otto cycle solver

clear all
close all
clc
%inputs
gamma =1.4;
t3 = 2300;
%state variabes
p1 = 101325;
t1 = 500;
%engine geometric internship
bore = 0.1;
stroke = 0.1;
cond_rod = 0.15;
cr =12;
% calculating the swept volume and the clearance volume
v_swept = pi/4*bore^2*stroke;
v_clearance = v_swept/(cr-1);
v1 = v_clearance + v_swept
v2 = v_clearance
%state variable at state 2
%p2V2^gamma = p1V1^gamma 
p2 = p1*cr^gamma;
t2 = (p2*v2*t1)/(p1*v1);
v_compression = engine_parameters(bore,stroke,cond_rod,cr,180,0)
constant_c = p1*v1^gamma
p_compression =constant_c./v_compression.^gamma;

%state variable 3


v3 = v2;
p3 = p2*t3/(t2);
v_expansion = engine_parameters(bore,stroke,cond_rod,cr,0,180)
constant_c = p3*v3^gamma
p_expansion =constant_c./v_expansion.^gamma


%state variable at state 4`
v4 = v1;
p4 = p3*(v3/v4)^gamma;
t4 = t1*p4/(p1);

figure(1)
hold on
plot(v1 , p1 ,\'*\',\'color\' ,\'r\')
plot(v_compression, p_compression)
plot(v_expansion,p_expansion)
plot([v2 v3],[p2 p3])
plot([v4 v1],[p4 p1])
plot(v2 , p2 ,\'*\',\'color\',\'r\')
plot(v3 , p3 ,\'*\',\'color\',\'r\')
plot(v4 , p4 ,\'*\',\'color\',\'r\')
%thermal efficiency
 
etta = 1-1/(cr)^(gamma -1);
fprintf(\'Thermal Efficiency = %1.3f\\n\', etta);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

function [v]= engine_parameters(bore,stroke,cond_rod,cr,start_crank,end_crank)

a= stroke/2;
R= cond_rod/a;
v_s = pi/4*bore^2*stroke;
v_c = v_s/(cr-1);
theta =linspace(start_crank,end_crank,4);
term1= 0.5*(cr-1);
term2 = R + 1-cosd(theta);
term3 = (R^2 -sind(theta).^2).^0.5 ;
v = ( 1+term1*(term2-term3)).*v_c;

end

Where is function file?