1. At the beginning of the compression process of an air standard Otto cycle, p1= 1 bar, T1= 290 K, V1 = 400 cm3

. The maximum temperature in the cycle is 2200 K and the compression ratio is 8. Determine (a) the heat addition, in kJ. (b) the net work, in kJ. (c) the thermal efficiency. (d) the mean effective pressure, in bar.

2. Consider a modification of the air-standard Otto cycle in which the isentropic compression and expansion processes are each replaced with polytropic processes having n = 1.3. The compression ratio is 9 for the modified cycle. At the beginning of compression, p1 = 1 bar and T1

= 300 K. The maximum temperature during the cycle is 2000 K. Determine (a) the heat transfer and work per unit mass of air, in kJ/kg, for each process in the modified cycle. (b) the thermal efficiency.(c) the mean effective pressure, in bar.

3. A four-cylinder, four-stroke, 2.2-L gasoline engine operates on the Otto cycle with a

compression ratio of 10. The air is at 100 kPa and 60°C at the beginning of the compression process, and the maximum pressure in the cycle is 8 MPa. The compression and expansion processes may be modeled as polytropic with a polytropic constant of 1.3. Using constant specific heats at 850 K, determine (a) the temperature at the end of the expansion process, (b) the net work output and the thermal efficiency, (c) the mean effective pressure, (d) the engine speed for a net power output of 70 kW, and (e) the specific fuel consumption, in g/kWh, defined as the ratio of the mass of the fuel consumed to the net work produced. The air–fuel ratio, defined as the amount of air divided by the amount of fuel intake, is 16.

A 50-kg iron block and a 20-kg copper block, both initially at 80°C, are dropped into a large lake at 15°C. Thermal equilibrium is established after a while as a result of heat transfer between the blocks and the lake water. Determine the total entropy change for this process.