AIR STANDARD CYCLE

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 AIR STANDARD CYCLE:

 

OTTO CYCLE:

  • Nicholus august otto is invented a working four stroke diesel engine,that’s why the four stroke cycle is also known as otto cycle.later this formula is widely used in petrol engine too.
  • Otto cycle is an idealized thermodynamic cycle that explain about the function of typical spark ignition piston engine.it widely used in automobile engine.
  • In this system describe what happens to mass of air? And how it changes due to pressure,volume,temperature,addition of heat,removal of heat.



PROCESSES:

  1. Process 0-1 = intake stroke,mass of air is drawn into cylinder at constant pressure.
  2. Process 1-2 = isentropic compression stroke,to compress the air/fuel ratio the piston moves BDC(bootom dead center) to TDC(top dead center).
  3. Process 2-3 = constant volume heat addition,due to the compression,the air fuel mixture burns rapidly and it will produce massive heat while the piston stay at TDC.
  4. Process 3-4 = isentropic expansion,the power, the piston is driven outward by the expansion of gases.
  5. Process 4-1 = constant volume heat rejection,the heat is rejected while the piston at BDC.
  6. Process 1-0 = exaust stroke,the mass of air is relised to atmosphere at constant pressure.

AIR STANDARD CYCLE USING MATLAB:

clear all
close all
clc

%air standard cycle
%input
gamma=1.4;
t3=2000;

%state variable
p1=101325;
t1=500;

%engine geometric parameter
bore=0.1;
stroke=0.1;
con_rod=0.15;
cr=12;
%calculate swept and clearance volume
vs=(pi/4)*bore^2*stroke;
vc=vs/(cr-1);
v1=vs+vc;
v2=vc;

%state variable at point2
p2=p1*(cr)^gamma;
t2=(p2*v2*t1)/(p1*v1);
%calling a function for compression
constant_c=p1*v1^gamma;
v_comp=engine(bore,stroke,con_rod,cr,180,0);
p_comp=constant_c./(v_comp.^gamma);
%state variable at point3
v3=v2;
p3=(p2*t3)/t2;
%callind a function for expansion
constant_c=p3*v3^gamma;
v_exp=engine(bore,stroke,con_rod,cr,0,180);
p_exp=constant_c./(v_exp.^gamma);
%state variable at point 4
v4=v1;
p4=p3*(v3/v4)^gamma;
%to find a thermal efficiency
Thermal_efficiency=1-(1/(cr^(1.4-1)))
%plotting
figure(1)
hold on
xlabel('velocity')
ylabel('pressure')
plot(v1,p1)
plot(v2,p2)
plot([v2 v3],[p2 p3])
plot([v4 v1],[p4 p1])
plot(v_comp,p_comp)
plot(v_exp,p_exp)
plot(v3,p3)
plot(v4,p4)

In this program we wants to create pv diagram related to this we wrote some kind of formulla through otto cycle,and we wants to find out the thermal efficiency.so,we implemented thermal fprmulla.we can also write a function program here itself.but it much more ugly.so we write a program and call via function.before we calling a function we save a program in a one folder.otherwise,it won't call that function...

function program

function [v]= engine(bore,stroke,con_rod,cr,start_crank,end_crank)

a=stroke/2;
R=con_rod/a;
%calculate swept and clearance volume
vs=(pi/4)*bore^2*stroke;
vc=vs/(cr-1);

theta =linspace(start_crank,end_crank,100);

term1 = 0.5*(cr-1);
term2 = R+1-cosd(theta);
term3 = ((R^2-sind(theta).^2).^0.5);
v=(1+(term1*(term2-term3)))*vc;

end

for curve purpose we use mathematicall formulla and seperated as term1,2,3....otherwise it appear as a straight line...

output:

THERMAL EFFICIENCY=0.6299

figure 1

ERROR OCCURS WHILE RUN THE PROGRAM

 

*I JUST MADE A MISTAKES FORMULLA.WHEN I CORRECT IT.THE PV DIAGRAM AND THERMAL EFFICIENCY AUMATICALLY GOT IT....

if any doubts feel free to ask me instagram@ame_ir43


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