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COMET:
Colorado Mini Engine Team
Preliminary Design Review
October 14, 2013
Team members: Julia Contreras-Garcia Emily Ehrle Eric James Jonathan Lumpkin Matthew McClain Megan O’Sullivan Benjamin Woeste Kevin Wong
Customer: Lt. Joseph Ausserer, USAF University of Colorado
Outline • Project description
• Evidence of baseline feasibility
▫ Safety
▫ Testing
▫ Alternate Start Method
▫ Ability to Generate 500 W
▫ Modeling
• Status summary
• Strategy for conducting remaining studies
Future Studies Status Baseline Feasibility Project Description
2
Project Description
Future Studies
• Design and build a Power Extraction Unit (PEU) for a JetCat P-80 SE mini-turbojet engine that will generate 500 Watts of electrical power at 24VDC.
• Sponsored by Air Force Research Laboratory’s Aerospace Propulsion Outreach Program (APOP)
Status Baseline Feasibility Project Description
3
Jet Cat P80-SE Engine Specs6
Thrust 22 LB @ 125,000 RPM
Weight 2.9 LB, incl. starter
Diameter 4.4 inches
RPM Range 35,000 - 125,000
Exhaust gas temp. 580°C -690°C
Fuel consumption 9 oz per/min at full power
Fuel Jet A1, 1-K kerosene
4
Jet Cat P80-SE Engine[6]
Future Studies Status Baseline Feasibility Project Description
Objectives
Future Studies
• Level one ▫ PEU must generate 500 Watts of power at 24 Volts ▫ PEU must produce this power after the engine has been running
no longer than 1 min 20 s, twice the average start up time ▫ Engine and PEU must be compatible with the WPAFB test stand
• Level two ▫ Reducing thrust by no more than 25% ▫ Increasing specific fuel consumption by no more than 50% ▫ Producing 500 W throughout the engine’s operating range
• Level three ▫ Add no more than the weight than an equivalent battery pack
with 30 minutes of power (8 lbs) • Level four
▫ PEU to be entirely external to the JetCat engine, making the most modular solution.
Status Baseline Feasibility Project Description
5
CONOPS Diagram
Future Studies Status Baseline Feasibility Project Description
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Functional Block Diagram
Future Studies Status Baseline Feasibility Project Description
7
Trade Options Considered
Future Studies Status Baseline Feasibility Project Description
8
Trade Study: Power Extraction Methods
Future Studies Status Baseline Feasibility Project Description
Topic Weight Tapping Shaft Piezo Magnet Thermal Blow by Exhaust
Safety 16 3 4 3 4 3 3
Weight 5 4 5 5 5 3 3
Cost 8 4 2 5 2 4 1
Reliability 11 3 4 3 4 3 4
Testability 14 5 2 4 5 5 4
Feasibility 27 5 0 3 1 5 5
Impact 19 3 5 1 5 2 2
Total 100 3.95 2.72 3.02 3.41 3.71 3.44
9
Comparison of top two methods
Compressor Blow by Tapping the Shaft
Pros Cons
Power generation is independent of speed and temperature of engine
Higher decrease in performance
All components are well understood
Risk of stalling the engine
Risk of overheating engine
Pros Cons
Weighs less than compressor option
Removes stock starter
Easier to implement
Potential shaft imbalance
Less stages in power generation process (fewer losses)
10
Future Studies Status Baseline Feasibility Project Description
Hybrid Trade Study
11
Future Studies Status Baseline Feasibility Project Description
Topic Weight Tapping Shaft Tapping Shaft
w/TEG
Safety 10 3 2
Cost 15 4 3
Weight 15 4 2
Testability 10 5 5
Complexity 20 3 1
Impact 30 3 4
Total 100 3.2 2.85
Baseline Design: Tapping the Shaft
Future Studies
• Remove starter engine with alternator to utilize rotational energy of drive shaft
▫ Placement reduces negative effects on thrust
▫ Necessary to have a different system to start engine
• Alternator placed on rod extending from shaft
▫ Extension from original drive shaft
▫ Rod extends from inlet of engine
Status Baseline Feasibility Project Description
12
[1]
Critical Project Elements • Safety
▫ Foreign object debris entering engine ▫ Temperatures in excess of material capabilities ▫ Starting the engine without stock starter motor
• Testing ▫ Engine Characterization Test ▫ Measurements Necessary ▫ Test stand customization/ compatibility
• Alternate Engine Starting Method ▫ Combination starter/generator
• Ability to generate 500 W ▫ Performance of engine with power extraction system ▫ Generator system ▫ Power rectification
• Modeling ▫ Predicting engine characteristics and performance
Future Studies Status Baseline Feasibility Project Description
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Critical Project Elements Not Presented
• Obtaining engine
▫ ITAR export control regulations
▫ Air Force contract is delayed because of government shut down
▫ No feasibility analysis: engine is not ITAR controlled because under thrust threshold
• Thermal analysis
▫ No feasibility analysis because difficult without having engine and level of detail is out of scope at this point in the project
Future Studies Status Baseline Feasibility Project Description
14
Feasibility analysis: Safety
Future Studies Status Baseline Feasibility Project Description
• Safety Concerns
▫ Debris from PEU mounted at inlet of engine entering engine and causing damage
▫ Reduction in spin speed due to additional demand on drive shaft could increase turbine temperatures past tolerance
▫ Starting the turbine/compression rotation with compressed air (off ramp), may violate recommended safe distance for operating the engine
15
Feasibility analysis: Safety (cont.)
Future Studies Status Baseline Feasibility Project Description
• Concern Mitigation
▫ Install a FOD screen on Engine
JetCat FOD Screen for 4.37’’ diameter engines:~44$
▫ PEU Vibration Analysis
Analysis of vibrational modes of PEU and shaft
16
[5]
Feasibility analysis: Safety (cont.)
Future Studies Status Baseline Feasibility Project Description
• Concern Mitigation (cont.)
▫ Engine Auto Shutdown
Engine will automatically shutdown if temperature exceeds programmed limit during operation
Develop a thermal model of the engine to determine if temperatures will exceed operational limits
▫ Reinforce and Position Blast Shield (As Off Ramp)
Reinforce the blast shield and position it so we can stand close enough to the engine safely and manually start with compressed air.
17
Feasibility analysis: Engine
Characterization Test Purpose
• Need to characterize engine parameters (compressor pressure, nozzle temperature, etc.) in order to accurately model engine performance
• Validate engine model outputs to real engine data
• Need concrete engine parameters for more accurate power extraction calculations
18
Future Studies Status Baseline Feasibility Project Description
Feasibility analysis: Necessary
Measurements Type of Measurement Sensor Implementation/Integration
Thrust Load cell Already on Test Stand
Compressor Pressure (static and total)
Low Temperature Pressure Transducer
Already on Test Stand
Exhaust Temperature Thermocouple Already on Test Stand
Rate of Fuel Consumption
Liquid Flow Meter
Insert meter on incoming fuel line
Voltage and Current Multimeter On electrical power output
Future Studies Status Baseline Feasibility Project Description
19
Feasibility analysis: Testing (cont.)
Future Studies Status Baseline Feasibility Project Description
Test Stand Customization
• Hardware
▫ Replace engine clamps
• Sensors/DAQ
▫ Mount new sensors or re-purpose existing sensors
▫ Integrate new sensors into existing DAQ
20
Feasibility analysis: Alternate Engine
Starting Method – Starter Generator
•
Future Studies Status Baseline Feasibility Project Description
21
[2]
Feasibility analysis: Alternate Engine
Starting Method(cont.)
Voltage (Volts) Power Required (Watts)
0.1 0.000173
0.325 0.000564
Future Studies Status Baseline Feasibility Project Description
• Assuming a start up time of 5 seconds and normal voltage values for pump start @ 5000 rpm
RPM Torque Required to
yield 500 W
35,000 0.136 Nm
125,000 0.038 Nm
22
Feasibility: Generate 500W(cont.) • Determine available torque from engine using an
idealized model.
Future Studies Status Baseline Feasibility Project Description
23
[8]
Feasibility: Generate 500W (cont.)
Future Studies Status Baseline Feasibility Project Description
24
[8]
Feasibility: Generate 500W(cont.) • Idealized model results
Future Studies Status Baseline Feasibility Project Description
25
Feasibility: Generate 500W (cont.) • High speed alternator3
▫ 500 to 1000 W at 50,000 to 150,000 RPMs
83% of engine’s operational range
Torques range from 0.955 to 0.0637 Nm
▫ Direct drive combined heat and power unit
▫ Maximum weight of 2.1 pounds
Future Studies Status Baseline Feasibility Project Description
26
Feasibility: Generate 500W (cont.) • Three Phase Power Rectifier concerns
▫ Large Variation frequency (580 – 2080 Hz)
▫ High Currents (20 amps) required
▫ Output Voltage ripple requires smoothing
Future Studies Status Baseline Feasibility Project Description
27
[7]
Feasibility: Generate 500W (cont.) • Three phase power
▫ High current and voltage components are available
▫ Ripple can be attenuated with π filter or voltage
regulator (currently seeking clarification from
customer about what ripple is considered
acceptable)
Future Studies Status Baseline Feasibility Project Description
28
[7]
Feasibility analysis: Modeling
Future Studies Status Baseline Feasibility Project Description
29
Status Summary • Generate 500 W
▫ Engine outputs sufficient torque ▫ Power rectifier can handle expected loads ▫ Need further analysis of power rectification frequency
response • Reduce thrust by no more than 25% and increase thrust
specific fuel consumption by no more than 50% ▫ Simulink model requires further refinement
• PEU produces 500 W in less than 1 min 20 s after engine starts running ▫ Characteristic of generator engine relationship ▫ Power generated based on RPM, engine characterization
test needed to gain further information on engine start up cycle
Future Studies Status Baseline Feasibility Project Description
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Status Summary (cont.) • Weight of power extraction system
▫ High speed alternator for Combined Heat Power unit weighs maximum of ~2.1 lbs
▫ Within 8 lbs limit on system
• Test stand compatibility ▫ Generator will be mounted to front of engine on shaft,
no size limits in this direction ▫ Other engine dimensions are standard to JetCat P80-
SE, what test stand at WPAFB is designed for
• Generate 500 W over operating range ▫ Alternators are capable of generating 500 W over top
83% of range
Future Studies Status Baseline Feasibility Project Description
31
Strategy for Remaining Studies • Generator research and trade studies
▫ Single phase versus three phase
▫ Buy versus make
▫ RPM versus wattage
• Engine characterization test
▫ Must wait until engine is acquired
• Power rectification research
▫ Voltage regulator versus π filter
Future Studies Status Baseline Feasibility Project Description
32
References 1. Antônio Rosa do Nascimento, Marco, Rodrigues, Lucilene de Oliveira, Cruz dos Santos,
Eraldo, Eber Batista Gomes, Eli, Luis Goulart Dias, Fagner, Iván Gutiérrez Velásques, Elkin and Alexis Miranda Carrillo, Rubén, “Micro Gas Turbine Engine: A Review,” Progress in Gas Turbine Performance, InTech, Rijeka, 2013.
2. Engineering Toolbox, “Angular Motion – Power and Torque.” www.engineeringtoolbox.com. Engineering Toolbox. Web. 11 Oct 2013. http://www.engineeringtoolbox.com/angular-velocity-acceleration-power-torque- d_1397.html.
3. James, B.P, and Al Zahawi, B.A.T., “A High Speed Alternator for a Small Scale Gas Turbine CHP Unit,” Seventh International Conference on Electrical Machines and Drives, Manchester University, UK, 1995, pp. 281-285
4. “JetCat Lieferprogramm 2013-1,” JetCat, Wettelbrunnerstr, Germany, 2013. 5. Jet Cat USA. "Jet-Net FOD Screen (4.37" Diameter Engines).”
www.sitewavesstores5.com. JetCatUSA, n.d. Web. 11 Oct. 2013. <http:// www.sitewavesstores5.com/mm5/merchant.mvc?Screen=PROD>.
6. Jet Cat USA. “Instruction Manual V6.0 ECU”. Print. JetCatUSA, n.d. 11 Oct. 2013 7. Pejovic, P. “Three-Phase Diode Rectifiers with Low Harmonics,” New York, Springer
Science+Buisness Media, 2007, Print 8. Rahman, N. U. and Whidborne, J. F., “A Numerical Investigation into the effect of
engine bleed on performance of a single spool turbojet engine,” Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering Vol. 222, Number 7, pp. 939-949, 2008.
Future Studies Status Baseline Feasibility Project Description
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Questions?
Future Studies Status Baseline Feasibility Project Description
Back Up Slides
Future Studies Status Baseline Feasibility Project Description
Compressor Bleed Air
Pros Cons
Power Generation is independent of engine speed and temperature.
Air pulled from engine will degrade performance.
Components of design are well understood
Generator will be heavy compared to engine.
Components of design are available “Off the Shelf”
Risk of Stalling Engine
Manufacture requires physically altering engine.
Future Studies Status Baseline Feasibility Project Description
36
Thermal Electric Generators Pros Cons
Does not disrupt air flow and thus doesn’t affect thrust and can possibly increase fuel efficiency
Would require nearly 500 TEGs surrounding the nozzle to achieve 500 Watts of power
Novel idea. Has never been used on jet engine before
Procurement of materials is difficult
Many different versions are available for purchase online
Ones available for purchase online have max temperatures at around 300°C. Thus the necessity to manufacture our own
Requires no actual manufacturing or much modification of the engine itself
Mass adds up as many are necessary in order to produce the amount of power required
Can be tested without the engine itself The higher the temperature gradient the more power that is produced may lead to necessity of cooling system for one side.
Future Studies Status Baseline Feasibility Project Description
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Engine Characterization Visual
Combustor
Combustor
Co
mp
ress
or T
urb
ine
P
P
P
T
T T
Test Stand
Thrust Inlet
Load
RPM
P T Ambient:
Fuel Tank
M P = Pressure Sensor T = Temp Sensor Load = Load Cell RPM = RPM Sensor = Flow Meter
Load
T
RPM
P
M
38
Engine Characterization Test
Type of Measurement
Sensor Implementation/Integration
Thrust Axial Load Cell Already on Test Stand
Compressor Pressure (Static and Total)
Low Temp Pressure Sensors
Already on Test Stand
Inlet Pressure (Static and Total)
Low Temp Pressure Sensors
Already on Test Stand
Ambient Pressure Low Temp Pressure Sensors
Already on Test Stand
Exhaust Pressure (Static and Total)
High Temp Pressure Sensors
Already on Test Stand
Future Studies Status Baseline Feasibility Project Description
39
Engine Characterization Test (cont.)
Type of Measurement
Sensor Implementation/Integration
Exhaust Temperature K-Type Thermocouple
Already on Test Stand
Compressor Temperature
K-Type Thermocouple
Already on Test Stand
Ambient Temperature K-Type Thermocouple
Already on Test Stand
Mass Flow of Fuel Liquid Flow Meter
Already on Fuel Pump
Engine RPM RPM Sensor 2 Methods: 1) Internal Engine RPM Sensor 2) RPM Sensor on Test Stand
Future Studies Status Baseline Feasibility Project Description
40
Secondary Engine Characterization
Test: Drive Shaft Torque
• First Test: Find Moment of Inertia of Drive Shaft Assembly
▫ Use handheld torque meter to measure torque of an electric motor spinning at a certain RPM
▫ Spin drive shaft with electric motor at known torque at known RPM, calculate MOI
• During Engine Characterization
▫ Accelerate engine linearly, measure RPM
▫ Calculate Torque as a function of RPM
41
Future Studies Status Baseline Feasibility Project Description
Testing Sensor Costs
• Currently:
▫ No Sensor Purchase Required, everything needed is available
• Potentially:
▫ Flow Meter:
Unit: Equiflow Flow Sensor
Unit Cost: $171.00
Replaceable Insert Cost: $65.00
42
Future Studies Status Baseline Feasibility Project Description
Compressed Air Start • Industry standard
▫ Primary method used prior to five years ago
▫ Now use electric starters
• Need to spin turbine up to correct speed
▫ 5,000 RPM for ignition
▫ ~35,000 RPM for engine to take over process
• Only need compressed air
▫ Air tanks
▫ Gas compressors
Future Studies Status Baseline Feasibility Project Description
43
Power Rectifier Equations •
Future Studies Status Baseline Feasibility Project Description
44