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

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Answer: Given: Oto Cycle Ti = 370 k EP - 120 kPa To compression Ratio - 10 Q = heat addition at constant = 1000 ko voheme kg Teacher's Signature.

P4 3 Tig: p-v diagram of otto cycle 2 1 y h =1.4 (for air) т. (10joy Te = 929.39K 370 Livi= const P2 es const a - Constant R B Р. [V V2 Pa = 120 x 10 1 P2 = 3014.26 kPa .. da = la dT TR Ś Cicle 10 KS kg 20

a in terms By putting the function of of tempt and integrating the equation o can find the numerical value of tempt h = Temp. of point Process (23) is constant voheme D P2 V₂ = P B Rh RB - 3014.26 P3 929.39 T3 1 P= 3.24 3 kPa P3- Presstake at end of heat addition process - 3.24 h kPa Ang T3 tempt at end of heat addition process (b) = thermal efficrency thermal [6Oy (103004 thernee 50-6018 Teachers Signature

Mothermal output work Head added o output woek Loox 0.6018 atput work = 601-8913 Kg (c) Thermal efficiency an thermal thermal = 0.6018 Ag Prenn: Meen effectice Pressure Pinean = n x [P3-b. thermal MICHU 0-60 18x (3.247-3014.26) Po-1 (1-4-1) Pomou 0.167 (3:24 3 - 80 1426) kPa Ang