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mech3020-s11-hw02

# mech3020-s11-hw02 - MECH 3020 Thermodynamics II Homework...

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MECH 3020 Thermodynamics II: Homework set #2 1. (Due 1/21) A spark ignition engine has a dis- placement of V D = 2 L and a compression ratio of r = 9. The conditions of the air in the cylin- der at the bottom of the compression stroke are P 1 = 100 kPa and T 1 = 300 K. The heat added during the 2–3 heat addition process is q H = 1200 kJ/kg. Using the Otto cycle model and constant specific heat assumptions, (a) Calculate T 2 , T 3 , P 3 , and T 4 . (b) Calculate the thermal efficiency of the en- gine, (c) Calculate the engine RPM necessary to produce a power output of 40 kW. This is a 4–stroke engine; you will need to ac- count for this. The following problems are due on 1/24 2. The temperature and pressure in a high– performance spark ignition IC engine at the be- ginning of the intake stroke are 300 K and 1 atm. For reasons of emissions control and ma- terial limitations, the maximum temperature in the cycle must be limited to 2600 K. The spe- cific heats of the air can be assumed constant, with c v = 0 . 72 kJ/kg K.
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