Chapter 5 (below). The agreement will not be exact, but it should be close. Hill included some inefficiencies in his engine components but we do not. Specific trut 004 1700 Specific fuel 1500 4000 Compressor pressure FIGURE 5.20 Turbojet cruise thrust and fuel consumption (M-0.85) Assume: constant heat capacity, gamma = 1.4, perfectly expanded pe = pa Computed Quantities No. Ta (K) Pa (atm) pa (kPa) ratio Pos/Poz Case Flight Ambient Ambient Ambient Compressor Maximum Fuel Mach temp. pressure pressure pressure temperature Heating T4 = T04 Value QR Flight Poz Speed kPa kPa P2 T₂ To2 P3 P4 T3 K K kPa K Uoo CPR (K) kJ/kg m/s 123456 0.85 2 1500 45,000 0.85 10 1500 45,000 0.85 20 1500 45,000 0.85 40 1500 45,000 0.85 60 1500 45,000 0.85 100 1500 45,000 LK T4 T5 Τε nozzle exit Specific combustor SFC K K velocity u₂ m/s thrust I ma fuel-air ratio kN/(kg/s) (f) Thermal Desired Air specific fuel efficiency Thrust mass flow consumption 7th KN (kg/s)/kN Fuel flow ma rate kg/s m, kg/s 300 300 300 300 300 300
Chapter 5 (below). The agreement will not be exact, but it should be close. Hill included some inefficiencies in his engine components but we do not. Specific trut 004 1700 Specific fuel 1500 4000 Compressor pressure FIGURE 5.20 Turbojet cruise thrust and fuel consumption (M-0.85) Assume: constant heat capacity, gamma = 1.4, perfectly expanded pe = pa Computed Quantities No. Ta (K) Pa (atm) pa (kPa) ratio Pos/Poz Case Flight Ambient Ambient Ambient Compressor Maximum Fuel Mach temp. pressure pressure pressure temperature Heating T4 = T04 Value QR Flight Poz Speed kPa kPa P2 T₂ To2 P3 P4 T3 K K kPa K Uoo CPR (K) kJ/kg m/s 123456 0.85 2 1500 45,000 0.85 10 1500 45,000 0.85 20 1500 45,000 0.85 40 1500 45,000 0.85 60 1500 45,000 0.85 100 1500 45,000 LK T4 T5 Τε nozzle exit Specific combustor SFC K K velocity u₂ m/s thrust I ma fuel-air ratio kN/(kg/s) (f) Thermal Desired Air specific fuel efficiency Thrust mass flow consumption 7th KN (kg/s)/kN Fuel flow ma rate kg/s m, kg/s 300 300 300 300 300 300
Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
Problem 1.1MA
Related questions
Question
1. Ideal turbojet problem: An ideal turbojet engine operates at an altitude of 15 km.
Look up values for Ta and p a in a standard atmosphere table on the web.
Flight Mach number is 0.85. The compressor pressure ratio CPR is 40, the maximum
gas temperature (T04 ) is 1500 K. The Jet-A fuel has a heating value of Q R = 45,000
kJ/kg. The nozzle perfectly expands the gas so that exit static pressure p e equals p a .
Use the same equations as we did in our lecture problem for an ideal turbojet.
Ideal means that the inlet, compressor, turbine and exhaust are isentropic.
As we discussed, the Mach number of the air is small at stations 2-5 so static and
stagnation conditions are the same.
Look up values for Ta and p a in a standard atmosphere table on the web.
Flight Mach number is 0.85. The compressor pressure ratio CPR is 40, the maximum
gas temperature (T04 ) is 1500 K. The Jet-A fuel has a heating value of Q R = 45,000
kJ/kg. The nozzle perfectly expands the gas so that exit static pressure p e equals p a .
Use the same equations as we did in our lecture problem for an ideal turbojet.
Ideal means that the inlet, compressor, turbine and exhaust are isentropic.
As we discussed, the Mach number of the air is small at stations 2-5 so static and
stagnation conditions are the same.
a) Find these values for an idea on how to do part b
i) what is the exit velocity of air in the exhaust ?
ii) what is the specific thrust, in kN thrust / (kg/s of air) ?
iii) what is the specific fuel consumption = kg/s of fuel / kN thrust ?
iv) what is the fuel-air ratio f ?
b) Repeat part a, but now use the Excel spreadsheet that is with posted with
your CANVAS homework assignment. All conditions are identical to the first
problem except that now you will vary the compressor pressure ratio p 3 /p 2 .
The spreadsheet is called the AE335 Turbojet Design Code. (I gave it to you
i) For case 4, notice that compressor pressure ratio CPR (p 3 /p 2 ) is 40, which is the same
as the first problem. For this case 4, type in the same equations as you used in the first
problem above, and verify that you get the same numbers for parts 1a to 1d.
ii) Use the Fill Down and Fill Up icons in Excel to fill in all the spreadsheet values for
cases (1-3 and 5 and 6).
iii) Now use Excel to make a plot of SPF (specific thrust) on the vertical axis versus CPR
on the horizontal axis. Plot a set of lines that connect your computed values.
i) what is the exit velocity of air in the exhaust ?
ii) what is the specific thrust, in kN thrust / (kg/s of air) ?
iii) what is the specific fuel consumption = kg/s of fuel / kN thrust ?
iv) what is the fuel-air ratio f ?
b) Repeat part a, but now use the Excel spreadsheet that is with posted with
your CANVAS homework assignment. All conditions are identical to the first
problem except that now you will vary the compressor pressure ratio p 3 /p 2 .
The spreadsheet is called the AE335 Turbojet Design Code. (I gave it to you
i) For case 4, notice that compressor pressure ratio CPR (p 3 /p 2 ) is 40, which is the same
as the first problem. For this case 4, type in the same equations as you used in the first
problem above, and verify that you get the same numbers for parts 1a to 1d.
ii) Use the Fill Down and Fill Up icons in Excel to fill in all the spreadsheet values for
cases (1-3 and 5 and 6).
iii) Now use Excel to make a plot of SPF (specific thrust) on the vertical axis versus CPR
on the horizontal axis. Plot a set of lines that connect your computed values.
iv) Now plot another curve, but plot SFC (specific fuel consumption) on the vertical
axis and CPR on the horizontal axis. Notice that this curve is similar to one in Fig.
5.20 above, but it will not be exactly equal
axis and CPR on the horizontal axis. Notice that this curve is similar to one in Fig.
5.20 above, but it will not be exactly equal
Try to get back to me with this in about 2-2 and a half hours, I need to know this stuff as I am severly struggling with it. Hopefully I will be fine, and use everything I learned in class but I need a hand with this.
Transcribed Image Text:Chapter 5 (below). The agreement will not be exact, but it should be close. Hill
included some inefficiencies in his engine components but we do not.
Specific trut
004
1700
Specific fuel
1500
4000
Compressor pressure
FIGURE 5.20 Turbojet cruise thrust and fuel consumption (M-0.85)
Transcribed Image Text:Assume: constant heat capacity, gamma = 1.4, perfectly expanded pe = pa
Computed Quantities
No.
Ta (K) Pa (atm) pa (kPa) ratio Pos/Poz
Case Flight Ambient Ambient Ambient Compressor Maximum Fuel
Mach temp. pressure pressure pressure temperature Heating
T4 = T04 Value QR
Flight
Poz
Speed kPa kPa
P2
T₂ To2 P3 P4 T3
K K kPa
K
Uoo
CPR
(K)
kJ/kg
m/s
123456
0.85
2
1500
45,000
0.85
10
1500
45,000
0.85
20
1500
45,000
0.85
40
1500
45,000
0.85
60
1500
45,000
0.85
100
1500
45,000
LK
T4 T5 Τε nozzle exit Specific combustor
SFC
K
K
velocity
u₂ m/s
thrust
I ma
fuel-air
ratio
kN/(kg/s)
(f)
Thermal Desired Air
specific fuel efficiency Thrust mass flow
consumption 7th
KN
(kg/s)/kN
Fuel
flow
ma
rate
kg/s
m, kg/s
300
300
300
300
300
300
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