Question

An air standard limited pressure cycle has a compression ratio of 15 and compression begins at 0.1 MPa, 40°C. The maximum pressure is limited to 6 MPa and the heat added is 1.675 MJ/kg. Compute (a) the heat supplied at constant volume per kg of air, (b) the heat supplied at constant pressure per kg of air, (c) the work done per kg of air, (d) the cycle efficiency, (e) the temperature at the end of the constant volume heating process, (f) the cut-off ratio, and (g) the m.e.p. of the cycle.

Answer 1

p₃ = p₄ = 6000 kPa 

Q_2–4 = 1675 kJ/kg

(a) Heat supplied at constant volume = C_v (T₃ – T₂) = 235 kJ/kg

(b) Heat supplied at constant Pressure = (1675 – 235) = 1440 kJ/kg

(c) Work done = Q₁ – Q₂ = 1675 – C_v (T₅ – T₁) = 1014.44 kJ/kg

(d) Efficiency η = \(\frac{Q_1 - Q_2}{Q_1} = \frac{1014.44}{1675}\) × 100% = 60. 56%

(e) Temperature at the end of the heating (T₃) = 1252 K

(f) Cut-off ratio