Otto-cycle engine kinematics

I have compiled otto-cycle engine kinematics program. The effficiency of the engine depends on the critical ratio(cr). Otto-cycle consists of two isentropic processes and are known as compression process and expansion process, and two constant volume process. During this isentropic process the temperature remains constant and pressure value changes in accordance with volume of the cylinder. By Here in the results volume v1 is the sum of swept volume and the clearance volume.

The coordinates are (v1,p1,); (v2,p2); (v3,p3); (v4,p4).

There are mainly four process.

1. Adiabatic compression of air (gamma=1.4) from (v1,p1) to (v2,p2).

2. Heat addition at constant volume from (v2,p2) to (v3,p3).

3. Adiabatic expansion of air from (v3,p3); to (v4,p4).

4. Heat rejection at constant volume from (v4,p4) to (v1,p1)

In the results graph the cycle starts from extreme lower point and follows the cycle in counter clock wise direction.

The efficiency of the cycle is defined as the ratio of net workdone to net heat added.

Total net work done can be explained as the difference between heat added and heat rejected which is also called as output. Net heat added is known as input. The value for the efficienct is given in the screenshot.

clear all
close all
clc

% Inputs
gamma = 1.4;
t3 = 2500;
% for isentropic process px(vx^gamma) = py(vy^gamma) 
% for ideal process (px*vx)/tx = (py*vy)/ty 
% cr = v1/v2

% state variables at point 1
p1 = 101325;
t1 = 600;

% Engine parameters
bore = 0.1;
stroke = 0.1;
connectingrod = 0.15;
cr = 13.5;

% calculations
vs = (pi/4)*bore*bore*stroke;
vc = vs/(cr - 1);
v1 = vs + vc;
v2 = vc;
v3 = v2;
v4 = v1;

%state variable at point 1
p1;
v1;
t1;

% state variables at point 2
p2 = p1*(cr^gamma);
t2 = (p2*v2*t1)/(p1*v1);
constant = p1*v1^gamma;
vcompression = volume(bore,stroke,connectingrod,cr,180,0);
pcompression = constant./vcompression.^gamma;

%state variables at point 3
p3 = (p2*v2*t3)/(v3*t2);

% state variables at point 4
v4;
p4 = p3*((1/cr)^gamma);
constant = p3*(v3^gamma);
vexpansion = volume(bore,stroke,connectingrod,cr,0,180);
pexpansion = constant./vexpansion.^gamma;

% efficiency of otto cycle
efficiency = 1 - ((1/cr)^(gamma-1));


figure(1)
hold on
grid on
plot(v1,p1,\'*\',\'color\',\'r\')
plot(vcompression,pcompression,\'color\',\'k\')
plot(v2,p2,\'*\',\'color\',\'r\')
plot(v3,p3,\'*\',\'color\',\'r\')
plot(vexpansion,pexpansion,\'color\',\'k\')
plot(v4,p4,\'*\',\'color\',\'r\')
xlabel(\'volome\',\'color\',\'b\')
ylabel(\'pressure\',\'color\',\'b\')