AME 436
Assigned: 3/10/08
Problem Set #4
Due: 3/24/08 at 12:00 noon in OHE 430 for oncampus
students (scan and email to Dan Hong or fax to me at 213
7408071 if you’re off campus); DEN students submit
homework through DEN
For all problems, if useful, you can use the AirCycles.xls spreadsheet to guide your answers but you need to explain your
results.
Note:
laptops or Pocket PCs running Excel spreadsheets will NOT be permitted on the exams.
Problem #1
For an Otto cycle with constantvolume combustion and the following parameters:
r = 9,
γ
= 1.3, M =
0.029 kg/mole, f = 0.062, Q
R
= 4.3 x 10
7
J/kg, T
2
= 300K, P
2
= 0.5 atm, P
exh
= 1 atm, h = 0,
η
comp
=
η
exp
=
0.9 (in other words, ideal
except for the compression and expansion efficiency, and the throttling
),
determine the following:
a)
Temperature (T
3
) and pressure (P
3
) after compression, and the compression work per kg of mixture
b)
Temperature (T
4
) and pressure (P
4
) after combustion
c)
Temperature (T
5
) and pressure (P
5
) after expansion, and the expansion work per kg of mixture
d)
Net work per kg of mixture (don’t forget about the throttling loss!)
e)
Thermal efficiency
f)
IMEP
Note in this case that we cannot simply use P
2
r
γ
and T
3
= T
2
r
γ
1
; instead we have to use the definitions of
compression and expansion efficiency given in lecture 6 to get the pressures and temperatures.
Problem #2
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 Spring '08
 Ronney
 Thermodynamics, Internal combustion engine, Diesel engine, Heat engine, compression ratio, fuel mass fraction

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