1
32kviews
An engine working on the Otto cycle is supplied with air at 0.1 MPa and 35oC the Compression ratio is 8. Heat supplied is 2100KJ/Kg. Calculate the maximum pressure and temperature of the cycle,

the cycle efficiency and mean effective pressure.

3 Answers
4
4.4kviews

p1=0.1MPa,T1=35+273=308K,r=v1v2=8:1,heat supplied=2100KJ/Kg

Adiabatic compression process 1-2:

T2T1=v1v2(γ1)=r(γ1)=8(1.41)

T2=2.297×308=707.476K

p1vγ1=p2vγ2

p2p1=v1v2γ=81.4=18.379

p2=18.379×1=18.379 bar

Constant volume process 2-3:

Heat added during the process,

cv(T3T2)=2100

0.72(T3707.476)=2100

T3=3624.143K

Also,

p2T2=p3T3

p3=p2T3T2

=18.379×3624.143707.476

p3=94.14 bar

Thermal efficiency,

ηth=11r(γ1)

=118(1.41)

ηth=.5674=56.74%

∴pressure ratio,rp=p3p2 =94.1418.379=5.122

The mean effective pressure is given by,

pm=p1r[(r(γ1)1)(rp1)](γ1)(r1)

=(1×8[8(1.41)15.1221](1.41)(81)

pm=15.28bar

1
880views

1.243457723×10^-3 this is my answer

0
933views

= (1×88(1.4−1)−1(5.122−1(8−1)/(1.4-1)(8-1)

Please log in to add an answer.