Memo
To:
Dan Pope, Ph.D
From:
Tim Elsner, Jesse Niemand, Scott Rasmussen, Dave Schindler
Date:
4/13/2020
Subject:
Jet Engine Lab
OBJECTIVE
The objective of the Jet Engine lab is to analyze the performance of an actual jet engine based on measurements taken in lab.
EQUIPMENT

Turbine Technologies, Ltd. Model LX4000 Gas Turbine Laboratory apparatus

Control Company Model No. 14-648-51 Aneroid Barometer

Airflow Type SJ/24 Manometer, 0 to 6 kPa
RESULTS
The jet engine was set up in the lab with a pre-configured digital data acquisition system that measures the fuel flow rate ( V
 fuel
), the thrust force ( F ), the engine RPM’s along with temperature thrust and pressure for the positions in Table 1.
Table 1: Data Acquisition Positions
Point Location
Area for
Flow
(m 2 )
1
2
3
Compressor Inlet
Compressor Exit
Turbine Inlet
0.00252
0.002622
0.00299
4
5
Turbine Exit
Thrust Nozzle
Exit
0.00299
0.00229
While the engine was running, there were measurements for temperature at the Thrust Nozzle
Exit and pressure taken for the manometer at four different RPM’s. Table 2 shows the data collected.
1

Table 2: Lab Data
Atmospheric
Pressure 100.4 kPa
RPM
44719
50050
65000
Temperature at Thrust
Nozzle Exit (deg C)
451
437
432
80200 482
The manufacturer’s specifications were also given and are shown in Table 3.
Table 3: Manufacturer's Specifications
Design Maximum Thrust
Max Exhaust Gas
Temperature
Mass Flow (air)
40 lbf
(178N)
1328°F
(720°C)
1.1 lbm/s
(0.5 kg/s)
1.33
Design Maximum RPM 87000
Engine Pressure Ratio
Specific Fuel Consumption
(s.f.c)
3.4
1.18 lbm/(lbf*hr)
6.8 inches
(17cm) Engine Diameter
Engine Length
10.8 inches
(27cm)
From the data collected in the lab along with the manufacturer’s specifications, the calculated results for the jet engine are shown in Table 4.
Table 4: Calculated Results
RPM
Pressure at Manometer
(kPa)
0.33
0.43
0.79
44719 50050 65000 80200
0.099
0.00129
76.432
0.112
0.00160
70.167
0.155
0.00252
61.574
0.206
0.00396
51.967 m`air (kg/s) m`fuel (kg/s)
A/F ratio
Compressor
Power (kW)
Compressor Eff.
(%)
Combustor Eff.
(%)
Turbine Power
(kW)
Turbine Eff. (%)
Nozzle Eff. (%)
Measured Thrust
(lbf)
Predicted Thrust
(lbf)
Predicted S.F.C.
(lbm/lbf*hr)
6.147
48.15
108.02
30.089
403.16
-2497
115.31
1.585
6.459
7.722
55.406
98.968
31.987
300.17
-1546
116.68
1.99
6.382
17.321
58.894
77.625
37.142
160.03
-723.03
117.54
3.701
5.408
31.789
65.102
74.042
57.002
120.13
-350.51
118.87
7.13
4.406
Mach Number 0.179 0.201 0.276 0.379
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The calculated values were obtained by assuming:

The nozzle exhausts to atmospheric pressure

In the compressor where the temperatures are low o c p
= 1.005 kJ/kg*K o k = 1.4

In the turbine and nozzle where the temperatures are higher o c p
= 1.148 kJ/kg*K o k = 1.333
Note: The measured thrust is not correct because the equipment was not in proper working order when the measurements were taken.
The efficiencies for the nozzle, compressor, combustor and turbine of the jet engine are represented in
Figures 1 and 2.
Nozzle Efficiency
0
40 45 50 55 60 65 70 75 80
Thousands
-350.509
-500
-723.03
-1000
-1500
-2000
-1546
-2500
-2497
-3000
RPM
Figure 1: Nozzle Efficiency
Compressor vs. Combustor vs. Turbine Efficiencies
450
400
350
300
250
200
150
100
50
0
40
403.159
300.17
160.033
108.021
98.968
55.406
77.625
58.894
120.125
74.042
65.102
48.15
45 50 55 60 65 70 75
RPM
Compressor Eff.
Combustor Eff.
Turbine Eff.
Figure 2: Compressor vs. Combustor vs. Turbine Efficiencies
80
Thousands
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The efficiencies for the jet engine are not very realistic at the lower RPM’s and the only ones that get close to realistic values are the compressor and combustor efficiencies as the RPM’s get closer to full throttle.
The nozzle efficiency is the most unrealistic because the temperature measured at the nozzle was higher than that of the turbine exit. The efficiency is negative because the entropy and temperature increases at the end of the cycle. This trend is better shown in the T-s diagram created in
Fig. 3. The reason for the bad data may be a result of a faulty or non-calibrated sensor in the system.
717.454
800
600
T.plot /

C
400
200
17.455
0
1.6
1.685
1.8
2 2.2
s.plot
kJ
2.4
2.6
2.8
2.896
Entropy
Figure 3: T-s Diagram at Full Throttle
The turbine efficiency is the second most unrealistic because it starts at 400% and ends at
120%. The high efficiency is due to the drastic change in temperature from the turbine inlet to the turbine exit. The efficiency is dependant on the difference of the two temperatures and the greater the difference, the higher the overall efficiency. The reason for the bad data may be a result of a faulty or non-calibrated sensor in the system.
The compressor efficiency starts out unrealistic at 108% when idling, but gets to a more realistic
74% as the engine hits full throttle. This is expected because the calculated stagnation temperature is
120°C and the actual temperature is 175°C. The 55°C difference is the largest at full throttle while idle has a difference of 32°C. The large range of temperatures that were acquired effect the efficiency directly when calculating.
The combustor efficiency is the only one that seems to be realistic with a starting efficiency of
48% at idle and an ending efficiency of 65% when at full throttle. This is due to the greater amount of air that is forced through the engine. As more air passes through the engine, the rate of heat transfer increases and directly effects the overall calculated efficiency.
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60
Looking at the compressor power versus the turbine power, Fig. 4 was created:
Compressor vs. Turbine Power
57.002
50
40
31.987
37.142
31.789
30.089
30
20
17.321
10
7.722
6.147
0
40 45 50 55 60 65 70 75 80
Thousands
RPM
Compressor Power Turbine Power
Figure 4: Compressor vs. Turbine Power
From Fig. 4, the turbine power is much greater than the compressor power. This is the case because the turbine and compressor are on the same shaft and both get power from the combustion of the fuel.
The reason for the difference is mainly due to the fact that the turbine is directly after the combustor along with losses in the bearings as the power is transferred to the compressor.
CONCLUSIONS AND RECOMMENDATIONS
Due to the skewed results of the lab, there were obviously sources of error in probably more than one instance throughout the lab. These error sources could have been introduced in many places throughout the lab including data collection, human error while reading instruments, and also instrumentation.
For the jet engine lab, speed (in RPMs), temperature at the nozzle exit, and monometer pressure difference were recorded at multiple speeds. The RPM reading was most likely very accurate since it is usually a .
At the specific thermocouple location at the thrust nozzle exit (T 05), the temperature data could be off. The reason this particular temperature could be skewed is because if there is too much fuel being consumed and not being combusted inside the engine, it could make its way out of the system and combust externally. When this happens, the temperature at T 05 is incorrect since, if the flame burns near, but externally, the temperature would read too high. In this case, the temperature would be hotter due to the flame when the combustion did not actually contribute power to the engine because of external combustion. If the flame combusted far enough away from the throttle nozzle exit, the temperature would be low.
The situation just explained would cause a big variation in the analyzation of the engine. If the temperature were high when the extra fuel combusted near the throttle nozzle exit, the data would predict that more fuel is being burned internally since that would create a hotter exit temperature. This would not be the case, the fuel that made the temperature rise would have actually not contributed to the performance of the motor, it combust externally and would be wasted. The other case where the
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fuel would burn away from the throttle nozzle exit would bring T 05 down. This condition would indicate that not enough fuel is being consumed, when in fact too much is being consumed. In both cases, the temperature would not be correct since the motor would not be operating correctly.
Figure 5: External flame combustion http://wings.avkids.com/Book/Propulsion/Images/components_01.jpg
It should be noted that when the jet engine was operating at full throttle, the release of extra fuel was actually occurring and combusting outside combustion chamber which would raise the specific fuel consumption data as it would be consuming more fuel than converting to kinetic energy.
The pressure difference recorded by the monometer would not have been off unless a person would be just barely blocking the atmospheric pressure side of it, but that is unlikely. It is, however possible that the reader of the monometer could have read the pressure difference incorrectly since the reading was from top to bottom instead of the conventional bottom to top scale.
The lab overall was very good, it gave the students a chance to see in person an actual jet engine operate and were able to discuss with other classmates the theory and what was actually happening. Unless students work for a company that makes jet engines, they will most likely not get the chance to come this close to one again. The fact that the students got to operate the engine was also beneficial and appreciated. Nothing needs to be changed on the way that that the lab is conducted.
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BIBLIOGRAPHY
[1] Boles, Michael A., Yunus, Cengel A., Thermodynamics an Engineering Approach, 5 th Edition,
McGraw-Hill Companies, Inc. (2006). http://wings.avkids.com/Book/Propulsion/Images/components_01.jpg
ATTATCHMENTS
See following attachments:
I. Calculations
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