Week 2 Air standard Cycle

"""
Otto_cycle
"""
import math
import matplotlib.pyplot as plt

def engine_kinematics(bore, stroke,con_rod, cr, start_crank, end_crank):

#geometric parameters

a = stroke/2
R = con_rod/a

#volume parameters
V_s = math.pi*(1/4)*pow(bore,2)*stroke
V_c = V_s/(cr-1)

sc= math.radians(start_crank)
ec= math.radians(end_crank)

num_values = 50

dtheta = ec-sc/(num_values-1)
V =[]

for i in range(0,num_values):
theta = sc + i*dtheta
term1 = 0.5*(cr-1)
term2 = R+1-math.cos(theta)
term3 = pow(R,2)-pow(math.sin(theta),2)
term3= pow(term3, 0.5)

V.append((1+term1*(term2-term3))*V_c)

return V

#inputs
p1 = 101325
t1 = 500
gamma = 1.4
t3 = 2300
con_rod =0.15
cr =12
bore =0.1
stroke =0.1

#volume computation
v_s = math.pi*(1/4)*pow(bore,2)*stroke
v_c = v_s/(cr-1)
v1 =v_c +v_s

#state2 point 2
v2 = v_c

#p2v2^gamma = p1v1^gamma
p2 =p1*pow(v1,gamma)/pow(v2,gamma)

#p2v2/t2 = p1v1/t1 | rhs = p1v1/t1 |p2v2 =rhs |t2 = p2v2/rhs
rhs =p1*v1/t1
t2 = p2*v2/rhs
V_compression = engine_kinematics(bore, stroke,con_rod,cr,180,0)

constant = p1*pow(v1,gamma)

P_compression =[]

for v in V_compression:
P_compression.append(constant/pow(v, gamma))

#state point 3
v3 = v2
#p3v3/t3 =p2v2/t2 |rhs = p2v2/t2 |p3 = rhs*t3/v3

rhs= p2*v2/t2
p3=rhs*t3/v3
V_expansion= engine_kinematics(bore, stroke,con_rod,cr,0,180)

constant = p3*pow(v3,gamma)

P_expansion =[]

for v in V_expansion:
P_expansion.append(constant/pow(v, gamma))

#state point 4
v4 = v1

#p4v4^gamma =p3v3^gamma

p4 = p3*pow(v3,gamma)/pow(v4,gamma)

#p4v4/t4 =rhs
t4= p4*v4/rhs

#thermal efficiency-otto cycle engine
k=1.4 #ambient air.
n_eff=1-(1/pow((cr),k-1)) #from source data formula for n_eff (thermal efficiency)

print(n_eff)

plt.plot([v2,v3],[p2,p3])
plt.plot(V_compression,P_compression)
plt.plot(V_expansion, P_expansion)
plt.plot([v4,v1],[p4,p1])
plt.show()