Question

An ideal Otto cycle has a compression ratio of 7. At the beginning of the compression process, P1 = 90 kPa, T1 = 27°C, and V1 = 0.004 m3. The maximum cycle temperature is 1147°C. For each repetition of the cycle, calculate the heat rejection and the net work production. Also, calculate the thermal efficiency and mean effective pressure for this cycle. Use constant specific heats at room temperature. The properties of air at room temperature are cp = 1.005 kJ/kg·K, cv = 0.718 kJ/kg·K, R = 0.287 kJ/kg·K, and k = 1.4.

The heat rejection is kJ____.

The net work production is kJ____.

The thermal efficiency is ____.

The mean effective pressure kPa____.

Answer 1

TO SOLVE QUESTION FIRST WE MUST KNOW ALL PROCESSES OCCURING IN OTTO CYCLE

THEN AS WE KNOW

HEAT IS REJECTED AT CONSTANT VOLUME (4 - 1) = m*C_v*(T₄ - T₁)

NET WORK PRODUCED = HEAT ADDED(2 - 3) - HEAT REJECTED(4 - 1) = Q_a - Q_r

THERMAL EFFICIENCY = WORK DONE / HEAT ADDED = W_net / Q_a

MEAN EFFECTIVE PRESSURE = WORK DONE / SWEPT VOLUME = W_net / V₁ - V₂

values of temperature and volume can be found out by various relations for each processes as calculated below