# Presentation: 285247

## 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

## 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

## 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.

## 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.

## 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)

## 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

## Non-Toxic is a RELATIVE term

## The Initial Experimental Apparatus

- (Schneider)

## Components of the Apparatus

- Inlet Pressure Transducer

- Inside-Boiler Thermocouple

- Boiler Thermocouple

- Ethanol Inlet

- Inlet Thermocouple

- Tube Thermocouple Connections

## Components of the Apparatus

- Digital Controller Input

- Bleed Valve

## Components of the Apparatus

- Electrical Heating Tab

- 750 sccm N2 Purge  (Large flow rate needed for successful Gas Analyzer Operation)

- Voltage across tube

- Exhaust Pressure Transducer

- ...to the Analyzer

## 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

## 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

## ChemKin Modeling

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

## 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.

## Initial Experiment (6/22) Results

## 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

## Anomalous Result

- 		There was a significant unexpected result.

## Possible Causes of Anomaly

- 	Condensation of Vaporized 100 proof Ethanol

## Possible Causes of Anomaly

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

## Possible Causes of Anomaly	

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

## 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.

## Changes Made to Apparatus

- Heater Tape

## Changes Made to Apparatus

- 			       Three-Way Bypass Valve

- Oxygen from Flow Controller

- Oxygen to plenum, then to microtube

- Oxygen to Atmosphere

## 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

## Initial GOX Addition (7/22)

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

## Initial GOX Addition (7/22)

- Second Oxygen Addition
- -> Insignificant Change in Molar Ratios

## Initial GOX Addition (7/22)

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

## Initial GOX Addition (7/22)

- Unexpected Pressure Rise  (.....again)

## Initial GOX Addition (7/22)

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

## Initial GOX Addition (7/22)

- Chemkin Predicted the following.....

## Secondary GOX Addition (7/27)

- Ethanol Instability
- -> Interesting results after the experiment......

## Secondary GOX Addition (7/27)

- Carbon Soot Formation

## Support of our Conclusion

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

## Support of Sooting Theory

- ChemKin Results

## Can we solve the Sooting problem?

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

## Micro-catalyzed EthanolSteam Reforming  (7/28)

- Results:

## Micro-catalyzed EthanolSteam Reforming and Combustion  (7/28)

- Results:

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

## Conclusions

- Ethanol can in fact be made a dirty fuel.

## 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?

## Conclusions

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

## 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
- Mr. Ed Braunscheidal