Air standard Cycle using python

INTRODUCTION:

Air standard cycles are quite important as they help us to understand the theoretical limits of a particular cycle ,which can be used to get an idea about the performance of IC engine.

An otto cycle consist of following processes:

1.Isentropic Compression process(1-2)

2.Constant Volume heat addition(2-3)

3.Isentropic Expansion process (3-4)

4.Constant Volume heat rejection(4-1)

In a otto cycle compression ratio is a crucial parameter.

Formulas used :

Swept Volume= pi/4*bore^2*stroke

Clearance volume= Swept volume/cr-1

Pressure*volume^gamma=constant

pressure*volume/temperature= constant

efficiency=(1-(1/cr)^(gamma-1))*10

program to solve an otto cycle and make plots for it.

# OTTO cycle simulator

import math
import matplotlib.pyplot as plot

def enginekine(bore,stroke,conrod,cr,start_crankangle,end_crankangle):
	#input engine parameters
	a=stroke/2
	R=conrod/a
	#defining angles
	sc=math.radians(start_crankangle)
	ec=math.radians(end_crankangle)
	numvalues=100
	dtheta=(ec-sc)/(numvalues-1)
	vs=(math.pi/4)*pow(bore,2)*stroke
	vc=vs/(cr-1)
	V=[]
#tracing the volume curve
	for i in range(0,numvalues):
		theta=sc+i*dtheta
		term1=0.5*(cr-1)
		term2= R+1-math.cos(theta)
		term3=pow(pow(R,2)-pow(math.sin(theta),2),0.5)
		V.append((1+term1*(term2-term3))*vc)
	return V
#point 1
p1=101325
t1=500
gamma=1.4
t3=2500

bore=0.1
stroke=0.1
conrod=0.15
cr=10
vs=(math.pi/4)*pow(bore,2)*stroke
vc=vs/(cr-1)
v1=vc+vs

#point 2
v2=vc
p2=p1*pow(v1/v2,gamma)
#p2v2/t2=p1v1/t1 rearranging
t2=p2*v2*t1/(p1*v1)
Vcompress=enginekine(bore,stroke,conrod,cr,180,0)
constant=p1*pow(v1,gamma)
pcomress=[]

#point 3
for v in Vcompress:
	pcomress.append(constant/pow(v,gamma))
v3=v2

#p3v3/t3=p2v2/t2 
p3=p2*v2*t3/(v3*t2)

Vexpand=enginekine(bore,stroke,conrod,cr,0,180)
constant=p3*pow(v3,gamma)
pexpand=[]


#point 4
for v in Vexpand:
	pexpand.append(constant/pow(v,gamma))
v4=v1
p4=p3*pow(v3/v4,gamma)
t4=p4*v4*t3/(p3*v3)
#plotting the pv diagram
plot.plot([v2,v3],[p2,p3])
plot.plot(Vcompress,pcomress)
plot.plot(Vexpand,pexpand)
plot.plot([v4,v1],[p4,p1])
plot.show()	


#Thermal efficiency
n = 1-(pow(cr,(1-gamma)))
print(n)

STEPWISE EXPLANATION OF CODE:

Step 1: importing libraries

Step 2:Defining thermodyanamic properties.

Step 3:Defining engine geometroc parameters.

Step 4:Pressure & Temperature at state 1.

Step 5:calculating swept volume and clearance volume.

Step 6:calculating themodynamic propert at state 1.

Step 7:Calling the function to determine various points between state1 & 2

Step 8:calculating properties at state 2.

Step 9: Properties at third state 3.

Step 10:Calling the function to determine various points between state3 & 4.

Step 11:Properties at state 4.

Step 12:Plotting the points and lines.

Step 13:calculating thermal efficiency.

then writing a fuction as shown below fuction and then using it in main program and calcute and plot the pv diagram.

RESULT:

Hence efficiency of otto cycle is 60.18%