Microcombustion: Catalyzed Partial Oxidation of Ethanol in a Heated Nickel Microtube

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Microcombustion Catalyzed Partial Oxidation of
Ethanol in a Heated Nickel Microtube

• Final Presentation
• Peter Galie
• Princeton University
• Principal Investigator Dr. Steven J. Schneider
• Glenn Research Center
• Cleveland, Ohio

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Introduction

• The Necessity for Micro-scale Combustors
• i. MEMS/ Micro-Spacecraft (20-100 kg)
• ii. Nano-Spacecraft (10-20 kg)
• iii. Ignition for large-scale rockets

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Benefits of Micro-scale

• Size, Weight
• Currently costs 10,000/kg to put an object
  into Lower Earth Orbit.
• Versatility
• Small spacecraft can perform a variety of
  different missions, from global
• surveying to disaster
• monitoring of other
• spacecraft.

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Limitations of Micro-Combustion

• As the size of combustion chamber decreases, the
  surface area to volume ratio increases. Heat
  release rate scales with volume, while heat loss
  rate scales with surface areas. Thus, at high
  surface area to volume ratios, heat loss
  dominates.
• The quenching diameter, the critical distance
  below which a flame cannot propagate and
  combustion is impossible.

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Catalyzed Micro-Combustion

• Surface Catalysis
• The use of a heated catalyst such as platinum
  or palladium can aid in the chemical combustion
  of hydrogen and oxygen as presented in studies by
  Dr. Schneider of NASA and Professor Sung of Case
  Western.

(C. Sung)
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Why Ethanol?

• Steam Reforming of 100 Proof Ethanol
• C2H5OH H2O ? 2CO 4H2
• Nickel serves as a good surface catalyst for this
  reaction. Performs like platinum or palladium,
  but MUCH cheaper.
• Ethanol contains more energy per unit mass than
  most other alternative fuels. It is derived
  through biological processes, NOT using fossil
  fuels.
• Non-toxic

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Non-Toxic is a RELATIVE term
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The Initial Experimental Apparatus

(Schneider)
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Components of the Apparatus
Inlet Thermocouple
Ethanol Inlet
Inlet Pressure Transducer
Inside-Boiler Thermocouple
Boiler Thermocouple
Tube Thermocouple Connections
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Components of the Apparatus
Digital Controller Input
Bleed Valve
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Components of the Apparatus
to the Analyzer
Exhaust Pressure Transducer
Electrical Heating Tab
750 sccm N2 Purge (Large flow rate needed for
successful Gas Analyzer Operation)
Voltage across tube
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Experimental Results

• Variables
• Flow Rate, Temperature
• Measurements
• Temperature Heater, Inside, Outside
  Hotplate, Inlet to tube, Microtube 1,2, and
  3.
• Pressure Inlet pressure, Outlet pressure
• Gas composition HCs, CO, CO2, H2
• Voltage Power Source, Across tube
• Flow Rate Nitrogen Purge, Ethanol Flow

LabView
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Flow Analysis

• Possibility of Flow Choking, Details of Chemical
  Kinetics calculated by PLUG Component of ChemKin
• Rayleigh Flow Heat Flux
• Fanno Flow Friction
• Hugonoit Flow Pressure Density

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ChemKin Modeling

• Ethanol steam reforming chemical kinetics has NOT
  been well studied. Solution? - Model methane on
  nickel as an approximation.

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Initial Experiment (6/22) Results

• Chemical Reaction C2H5OH H2O ? 2CO 4H2
• So we expect the rate of hydrogen production to
  be twice that of carbon monoxide.
• Moreover, we should see a steep decrease in the
  amount of ethanol analyzed.

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Initial Experiment (6/22) Results
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Catalyst Activation Temperature

• Nickel must reach a certain temperature before it
  can be activated to catalyze the ethanol
  reformation.
• Looking at the previous graph, one can see that
  the activation temperature is approximately 800
  oF

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Anomalous Result

• There was a significant unexpected result.

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Possible Causes of Anomaly

• Condensation of Vaporized 100 proof Ethanol

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Possible Causes of Anomaly

• Heat Transfer The heat dissipates very quickly
  due to the small diameter of the highly
  conductive copper tubing. Simplified Equations

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Possible Causes of Anomaly

• Heat Transfer Analysis Assuming 50 degree
  Fahrenheit difference between vapor and tube
  wall.

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Midterm Status

• The ethanol reforming process is an endothermic
  reaction. It cannot sustain itself without
  constant addition of power.
• Through the addition of gaseous oxygen (GOX), the
  hydrogen from the ethanol could react with the
  oxygen to produce a highly exothermic reaction.
• This could lead to sustainability, or the heat
  could be used to expand the products through a
  small nozzle, creating a mini-thruster.

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Changes Made to Apparatus
Heater Tape
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Changes Made to Apparatus
Oxygen to plenum, then to microtube
Oxygen from Flow Controller
Oxygen to Atmosphere

• Three-Way Bypass Valve

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GOX Addition Failure (7/20)

• Ethanol Flow controller became very instable at
  onset of the test. A large flow passed through
  the tube before resistive heating. This
  saturated the flow analyzer with hydrocarbons.
  Eventually, the tube broke due to the thermal
  stress, before oxygen could be added.
• In other words this was a BAD day

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Initial GOX Addition (7/22)

• First Oxygen Addition
• Large Temperature Decrease. Catalyst Activation.
  Rapid Deactivation

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Initial GOX Addition (7/22)

• Second Oxygen Addition
• -gt Insignificant Change in Molar Ratios

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Initial GOX Addition (7/22)

• Increased Flow Rates
• -gt Mixing Ratios were increased from 0 to 0.4
• -gt Brief Periods of Surface Catalysis

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Initial GOX Addition (7/22)

• Unexpected Pressure Rise (..again)

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Initial GOX Addition (7/22)

• Vacuum Conditions
• -gt Indicated a large hole inside the microtube.
  Suspicions were confirmed.

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Initial GOX Addition (7/22)

• Chemkin Predicted the following..

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Secondary GOX Addition (7/27)

• Ethanol Instability
• -gt Interesting results after the experiment

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Secondary GOX Addition (7/27)

• Carbon Soot Formation

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Support of our Conclusion

• Reduce Temperature, Reduce Proof
• Steam Reforming of 75 Proof Ethanol

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Support of Sooting Theory

• ChemKin Results

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Can we solve the Sooting problem?

• 75 Proof, Low Temperatures
• What does ChemKin think?

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Micro-catalyzed EthanolSteam Reforming (7/28)

• Results

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Micro-catalyzed EthanolSteam Reforming and
Combustion (7/28)

• Results

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Self-Sustainability Attempt (8/9/05)
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Conclusions

• Ethanol can in fact be made a dirty fuel.

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Conclusions

• The design of the combustor must be changed.
• The microtube was used for computational
  simplicity. Perhaps a more robust design could
  promote full sustainability.

Swiss Roll?
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Conclusions

• BUT!
• .. under the right conditions, a robust steam
  reformer and combustor can be constructed using
  nickel-catalyzed ethanol as a fuel source.

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Acknowledgements

• The New Jersey Space Grant
• The NASA Academy
• My Principal Investigator
• Dr. Steve Schneider
• Branch Chief
• Dr. Rich Blech
• Laboratory Colleague
• Mr. Roger Scheman
• Propulsion Engineers
• Mr. Eric Pencil
• Mr. Brian Reed
• Dr. James Gilland
• Office Colleagues
• Mr. H.T. Huynh