Question

The conditions at the beginning of compression in an Otto engine operating on hot-air standard with k=1.35 and 101.325 kPa, 0.05m3 and 32C. The clearance is 8% and 15kJ are added per cycle. Determine the mean effective pressure.

Answer 1

`P_m=181.42 KPa`

Step-by-step explanation:

`P_1=101.325 KPa,V_1=0.05m^3,T_1=32C`,K=1.35

Clearance is 8%.

Heat added=15 KJ

We know that compression ratio
`r=1+(1)/(C)`

`r=1+(1)/(0.08)`

r=13.5

`r=(V_1)/(V_2)`

`13.5=(0.05)/(V_2)`

`V_2=3.7* 10^(-3)`

We know that efficiency of otto cycle

`\eta =1-(1)/(r^(k-1))`

`\eta =1-(1)/(13.5^(1.35-1))`

`\eta =0.56`

`\eta =(W)/(Q)`

W is the work out put and Q is the heat addition.

`0.56 =(W)/(15)`

W=8.4 KJ

We know that Work =Mean effective pressure x swept volume.

Here swept volume
`V_s=V_1-V_2`

`V_s=0.05-3.7* 10^(-3)`

`V_s=0.0463 m^3`

Noe by putting the values

Work =Mean effective pressure x swept volume.

`8.4=P_m* 0.0463`

`P_m=181.42 KPa`