DETERMINATION OF PV DIAGRAM AND ITS THERMAL EFFICIENCY OF ENGINE USING MATLAB

AIM:

To determine the pv diagram and thermal efficiency of engine using MATLAB

INTRODUCTION:

The Otto cycle is a set of processes used by spark ignition internal combustion engines.The different process such as isentropic compression,constant volume heat addition,isentropic expansion,cpnstant volume heat rejection.

The efficiency of otto cyle is ,

THEORY:

The diagramatic representation ofPiston and valves in a four-stroke internal combustion engine.

The process of converting gasoline into motion is called "internal combustion." Internal combustion engines use small, controlled explosions to generate the power needed to move your car all the places it needs to go.

An internal combustion engine (ICE) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit.

OTTO CYCLE:

The Otto Cycle, describes how heat engines turn gasoline into motion. This cycle turns chemical energy into thermal energy and then into motion. The Otto cycle describes how internal combustion engines (that use gasoline) work, like automobiles and lawn mowers.

The compression ratio, CR, is defined as the ratio of the volume at bottom dead center and the volume at top dead center.

FORMULA USED:

swept volume=Πbore² x stroke

clearance volume=swept volume/(cr-1)

cr-compression ratio=(v1/v2)

Ideal gas=pv/T

THERMAL EFFICIENCY :


Efficiency increases with increase in compression ratio and specific heat ratio (γ) and is independent of load,amount of heat added and initial conditions.

In general the thermal efficiency, of any heat engine is defined as the ratio of the work it does, W, to the heat input at the high temperature

PROGRAM:

clear all
close all
clc

%inputs
gamma=1.4
%state variables
p1=101325
t1=500
 
%engine geometry parameters
bore=0.1;
stroke=0.1;
con_rod=0.15;
cr=12;
t3=1500;

%calculating the swept volume and the clearance volume
v_swept=(pi/4)*bore^2*stroke;
v_clearance=v_swept/(cr-1);
 v1=v_swept+v_clearance
 v2=v_clearance
 
 
 %state variables at state point 2
 %p2v2^gamma=p1v1^gamma
 %p2=p1*(v1/v2)^gamma=p1*cr^gamma
 p2=p1*cr^gamma;
 
%p1v1/t1=p2v2/t2 | t2=p2*v2*t1/(p1*v1)
t2=p2*v2*t1/(p1*v1);
constant_c=p1*v1^gamma;
v_compression=engine_kinematic(bore,stroke,con_rod,cr,0,180);

p_compression =constant_c./v_compression.^gamma;

%state variables at state point 3 
v3=v2
%p3v3/t3=p2v2/t2 | p3=p2*t3/t2
p3=p2*t3/t2
constant_c=p3*v3^gamma;
v_expansion=engine_kinematic(bore,stroke,con_rod,cr,180,0);

p_expansion =constant_c./v_expansion.^gamma;

%state variable at state point 4
v4=v1

%p3v3^gamma=p4v4^gamma | p4=p3(v3/v4)^gamma
p4=p3*(v3/v4)^gamma


%thermal efficiency
thermal_efficiency=1-(1/(cr^(gamma-1)))
figure(1)
hold on
plot(v1,p1,'*','color','r')
plot(v_compression,p_compression)
plot(v2,p2,'*','color','r')
plot([v2 v3],[p2 p3])
plot(v3,p3,'*','color','r')
plot(v_expansion,p_expansion)
plot(v4,p4,'*','color','r')
plot([v4 v1],[p4 p1])

figure(2)
plot([v1 v2 v3 v4],[p1 p2 p3 p4],'color','b')

OUTPUT:

The above diagram represents the output result with thermal efficiency of otto cycle

Thermal efficiency=0.6299

CONCLUSION:

In this project,MATLAB is used to perform the code and thermal efficiency and we can plot graph between pressure and volume.during the code,various errors has been arised and rectified to execute.

RESULT:

Thus the pv diagram and thermal efficiency of engine is determined using MATLAB.