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Unformatted text preview: Problem 1 116 points}: A spark—ignition automobile engine can be modeled as an Otto cycle with compression ratio 1“,, = 9 and displacement volume Vd = 0.002 m3. For operation at full throttle the following conditions are
found: T1=330K, T2=795K, T3=2400K. Assume that the airstandard model is valid and that the constant speciﬁc heats of air are taken at 300 K. The
heating value of the fuel is FHV = 43,000 kJ/kgfuel. Determine the minimum volume of the cycle, me, the
maximum volume of the cycle, Vmax, and the airtofuel ratio AF. v
(v: )7: *3; MJo’a
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\/’= ’03,,” = 0.00225 M3
V, 000995
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Mug—33 VF’v/m‘ Mom M3
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QH : W116 FHV \‘NMWW: WSW Wm P/boess.’ AF  W FHV  ”39‘”
"79 0 Cv (T3 ~12) h (ommwoo "795)
A? = 37.3; Vmin = 0000.15 m3 Vmax : 0,009.25 m3 Problem 2 118 points}: A fossilfueled steam power plant operates on the ideal Rankine cycle shown in the
schematic. The following operating conditions are known. P1= 10 kPa,v1 = 0.001010 m3/kg, P2 = 15000 kPa, 123 = 3310 kJ/kg, Determine the exhaust pressure, P4, the exhaust quality, x4,
and the entropy at the exit of the turbine, s4. 034W ﬂuke out/ms a (‘mdP/IW‘
P. : F4 : to kPA Side 3?
P3: Pg: 19,000 W01 1,33; 3310 W713 a 93: SB}! q: (peep/MP1? +ur9N) s5: 3:! = 0.3% 553;
P4: (0 k?“
X4: 05—75%?
a 163‘
S4: G. 590 ’3‘ K Problem 3 116 points): A refrigerator operating on a vaporcompression cycle is shown in the diagram below.
The working ﬂuid is R134a and the following conditions are known: P1: 60 kPa, P2 = 1600 kPa, x1=1,x3 = O, QH = 95 kW,
Assuming the compressor operates isentropically, determine: (A) The temperature exiting the compressor, T 2,
(B) The mass ﬂow rate of R—134a through the system, m, Ass {sz com:w: ’ ; 90 W ? O —> 93,: Ho “(I/13¢ Y, 1 l 819: S1 : 7:1: 73“1 0C,
a —._————_——_——————_ Pl: [560 W0. h; 1 4458 VJ/rj X3 ' 0
9/\ 1M {or Maser
52H : w ( K2443)
M: ﬁ— $36.; : 0.58%qc Vii/s
T2: 73.14 0C 3%.QOIK Problem 4 116 points}: Consider the steadystate Brayton cycle shown in the schematic below. The airstandard model holds and the following operating conditions are known: Assuming the constant speciﬁc heats of air are evaluated at a mean effective
temperature of 600 K, calculate the exhaust temperature, T4, and the exhaust’s P3=900 kPa, T3=850 K, P4: 150 kPa, 77C=80%, m~=85% isentropic temperature, T43. [)4 600k: 3(7 1370
[$145,991 +Urblhe‘. b.
P3 : <73 >‘C‘l
Pkf 17.45
Mal thm‘
pit " T3 TV a
B~T~(s
T, 570 3 K
T4, 9020,01 K :4
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v ~. 851) i (o.gs)(a’sb $220.9) 74: 570,30 k Problem 5 116 points): The real (nonideal) turboj et engine shown in the diagram below contains a diffuser
section at the inlet to slow the ambient air before entering the compressor. Assume the airstandard model holds, that cold properties are used for the constant specific heats of air (300 K), and that the following
conditions are known: m =1kg/s, T1= 250 K, T2 = 450 K, T3 = 1200 K, T4 = 765 K, P3/P4 = 6 =1500 k Calculate the rate of entropy generation in the turbine, 39,7134, and the rate of entropy generation in the combustion chamber, Sgen,2_3, if the equivalent heat of combustion comes from a reservoir at
TH = 1500 K. PWOM'PS of Ar a} 300 k Cp; Loos “3/ng
CV: 0/7’2 W/ks,“
k1 L000
Sean} Low , ”"NW’LQI
O = M53 ‘VJ'Sq + 5904,34
‘ ~ ~ 774 El
53,,“ : Mar—say = M cm ,3 ~ M F3)
, , 7(08 1
— Q )(0005 > m ~(0,337) L (a )>
' . KW
was/J [044/ W W: 5.9/5), 'co/hJSJMW (/LW
r 0 ~
0 : W] S}; ‘W’lss + T:L 4. 336%,2'3 OffH : WO’B‘ba)
 ' F l W) (T ~Ta)
53%,95 3 W(S>'Sg) ‘ if], C10 3
’H = UHLWSXth/oovysv)
(Imyﬂl‘ ”‘30 _0>~E£
 (H (V ) [500 : 753375— kw
kw
SI‘gen 34:.ﬂLL Mhmr WW
' M55 {neer » . W
8%,, = Aussies 5‘2— E Problem 6 118 points): A compressionignition, internal combustion engine operating on the ideal Diesel cycle
operates with a compression ratio of rv = 16 and a cutoff ratio of rC = 3. Assume the airstandard model holds with a mean effective constant speciﬁc heat ratio of k = 9/7. The following operating conditions are known: P, = 150 kPa, T, = 350 K, V, = 0.0015 m3 ® @ (9 Determine the speciﬁc heat at constant pressure, cp, the thermal efﬁciency of the Diesel cycle, 11,;,, and the mass of air used in the system during each cycle. I r k _ l
____ c
@ a: 2: ® ”2W0: I~ viii“Wm ]
k" ‘ 3‘17 
. (‘7/7)(0 187) _ ) ‘ F) q/7(3’))]
Q/7 1
C10 ‘ 1.951’5 %K [bmmr O #59059 k
cp lMR kw 77th = (DJ[530
ma= 0.0094“! ’53 q I ll ...
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 Spring '08
 Chung

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