1. Consider a supercharged, ideal engine operating under an Otto cycle. The key characteristics of the...

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1. Consider a supercharged, ideal engine operating under an Otto cycle. The key characteristics of the engine are similar to those for the ideal engine example problem worked in class: a compression ratio of 10, exhaust pressure 100 kPa, heat release 2512 kJ/kg of fresh mixture, specific heat ratio = 1.25. However, the intake pressure due to supercharging is 125 kPa and the intake temperature is 320 K. Determine: (For your initial guess assume that the residual mass fraction is 0.025 and that the exhaust temperature at the exhaust valve closing is 1090 K. These "guesses" should be good enough so that you only have to go through the iteration cycle once.) (a) The work output per kg of mixture and the net imep for the cycle. (b) The ratio of the total (not specific) work to the total work for a simple Otto cycle operating with the same compression ratio and residual mass fraction (and an intake temperature 320 K and an intake pressure of 100 kPa), and compare the thermal efficiencies of the supercharged cycle and the simple Otto cycle. (Note that the mass in the supercharged cycle is different from that in the simple cycle due to the differences in T1 and P.) (c) The results from parts a and b don't include the work done to supercharge the intake. Estimate the work required for the supercharging and then re-compute efficiency for the supercharged cycle and compare it to the simple Otto cycle efficiency calculated in part b. - = 1. Consider a supercharged, ideal engine operating under an Otto cycle. The key characteristics of the engine are similar to those for the ideal engine example problem worked in class: a compression ratio of 10, exhaust pressure 100 kPa, heat release 2512 kJ/kg of fresh mixture, specific heat ratio = 1.25. However, the intake pressure due to supercharging is 125 kPa and the intake temperature is 320 K. Determine: (For your initial guess assume that the residual mass fraction is 0.025 and that the exhaust temperature at the exhaust valve closing is 1090 K. These "guesses" should be good enough so that you only have to go through the iteration cycle once.) (a) The work output per kg of mixture and the net imep for the cycle. (b) The ratio of the total (not specific) work to the total work for a simple Otto cycle operating with the same compression ratio and residual mass fraction (and an intake temperature 320 K and an intake pressure of 100 kPa), and compare the thermal efficiencies of the supercharged cycle and the simple Otto cycle. (Note that the mass in the supercharged cycle is different from that in the simple cycle due to the differences in T1 and P.) (c) The results from parts a and b don't include the work done to supercharge the intake. Estimate the work required for the supercharging and then re-compute efficiency for the supercharged cycle and compare it to the simple Otto cycle efficiency calculated in part b. - =