Question

In an Otto cycle air is compressed from an initial pressure 120 kPa and temperature 370 T (K). The cycle has compression ratio of 10. In the constant volume heat addition process 1000 kJ/kg heat is added into the air. Considering variation on the specific heat of air with temperature, determine,

(a) the pressure and temperature at the end of heat addition process (show the points on P-v diagram)

(b) the network output

(c) the thermal efficiency

(d) the mean effective pressure for the cycle.

The gas constant of air is R = 0.287 kJ/kg.K

(Describe the necessary assumptions you have considered in your solutions.)

Answer 1

Asnwers:-

CASE-1 For Temprerature (T = 300°K)

Cp= 1.005 KJ/Kg K , Cv = 0.718 KJ/Kg K, Gamma= 1.4

(1) T3 = 2322.16 °K, P3 = 7531.47 Kpa

(2) Wnet = 601.89 KJ/Kg

(3) Thermal Efficiency = 60.19%

(4) mep = 755.75 Kpa

CASE -2 For Temperature (T= 400°K)

(1) T3 = 2296.17 °K, P3 = 7447.18 Kpa

(2) Wnet = 597.33 KJ/Kg

(3) Thermal Efficiency = 59.73 %

(4) mep = 750.03 Kpa