Revisica
Sign in
ENGR5003 / Week 4
Old spec L18 Question 2TutorialOld spec ENGR2172:212 min

ENGR217 (old spec) Thermo L18 tutorial, Question 2 official answers

In an ideal Otto cycle, the pressure and temperature of the air at the start of compression are 1 bar and 330 K. The compression ratio is 8 and 1250 kJ/kg of heat is added at constant volume. Determine the maximum pressure and temperature of the cycle, the thermal efficiency and the mean effective pressure. Take γ=1.4\gamma = 1.4, cv=0.7175c_v = 0.7175 kJ/(kg K), Rg=0.287R_g = 0.287 kJ/(kg K).

Formulas you may need
  • Adiabatic process: pVγ=constpV^\gamma = \text{const}, TVγ−1=constTV^{\gamma-1} = \text{const} (on the formula sheet)
  • Constant-volume heat addition qin=cv(T3−T2)q_{in} = c_v(T_3 - T_2); ideal gas p/Tp/T const at constant VV (on the formula sheet)
  • Otto efficiency η=1−rv1−γ\eta = 1 - r_v^{1-\gamma} (on the formula sheet)
  • Mean effective pressure MEP=wnetv1−v2\mathrm{MEP} = \dfrac{w_{net}}{v_1 - v_2} (on the formula sheet)