comet: colorado mini engine team preliminary design review

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

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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

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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

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Jet Cat P80-SE Engine[6]


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.


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CONOPS Diagram


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Functional Block Diagram


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Trade Options Considered


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Trade Study: Power Extraction Methods


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

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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)

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Hybrid Trade Study

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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


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[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


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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


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Feasibility analysis: Safety


• 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

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Feasibility analysis: Safety (cont.)


• 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

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[5]

Feasibility analysis: Safety (cont.)


• 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.

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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

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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


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Feasibility analysis: Testing (cont.)


Test Stand Customization

• Hardware

▫ Replace engine clamps

• Sensors/DAQ

▫ Mount new sensors or re-purpose existing sensors

▫ Integrate new sensors into existing DAQ

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Feasibility analysis: Alternate Engine

Starting Method – Starter Generator

•


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[2]

Feasibility analysis: Alternate Engine

Starting Method(cont.)

Voltage (Volts) Power Required (Watts)

0.1 0.000173

0.325 0.000564


• 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

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Feasibility: Generate 500W(cont.) • Determine available torque from engine using an

idealized model.


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[8]

Feasibility: Generate 500W (cont.)


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[8]

Feasibility: Generate 500W(cont.) • Idealized model results


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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


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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


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[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)


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[7]

Feasibility analysis: Modeling


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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


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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


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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


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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.


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Questions?


Back Up Slides


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.


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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.


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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

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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


Inlet Pressure (Static and Total)

Low Temp Pressure Sensors


Ambient Pressure Low Temp Pressure Sensors


Exhaust Pressure (Static and Total)

High Temp Pressure Sensors



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Engine Characterization Test (cont.)

Type of Measurement

Sensor Implementation/Integration

Exhaust Temperature K-Type Thermocouple


Compressor Temperature

K-Type Thermocouple


Ambient Temperature K-Type Thermocouple


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


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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

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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

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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


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Power Rectifier Equations •


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