Ultraviolet Emission Spectroscopy Ultraviolet Emission Spectroscopy of the Hydroxyl Radical in of the Hydroxyl Radical in

Miniscale PMMA Hybrid Rocket Miniscale PMMA Hybrid Rocket Motor Exhaust PlumesMotor Exhaust Plumes

Kellen HarknessKellen Harkness

Department of ChemistryDepartment of Chemistry

Harding UniversityHarding UniversityASGC Conference – 20 April 2007ASGC Conference – 20 April 2007

BackgroundBackground

Hybrid rocket motorsHybrid rocket motors Stable, cheap fuelStable, cheap fuel Need constant oxidizer Need constant oxidizer

flow for useflow for use SpaceShipOneSpaceShipOne

Harding’s involvementHarding’s involvement Development of Development of

spectroscopic methodspectroscopic method MiniscaleMiniscale SafeSafe InexpensiveInexpensive FastFast

SubjectSubject MatterMatter

Fuel:Fuel: Polymethylmethacrylate Polymethylmethacrylate (PMMA), or Plexiglas(PMMA), or Plexiglas TransparentTransparent Chemically simple, clean burningChemically simple, clean burning Easy to obtainEasy to obtain Easy to machineEasy to machine

Oxidizer: Oxidizer: Gaseous oxygenGaseous oxygen Chemically simpleChemically simple On handOn hand

(C(C55OO22HH88))nn + 6+ 6nn O O22 → 5 → 5nn CO CO22 + 4 + 4nn H H22OO

UV Emission SpectroscopyUV Emission Spectroscopy What is it?What is it?

Measurement of electronic Measurement of electronic transitionstransitions

The hydroxyl radicalThe hydroxyl radical Formed by several reactionsFormed by several reactions Common, high energy Common, high energy

intermediate for combustion intermediate for combustion processesprocesses

AA22ΣΣ X X22ΠΠ

Common problemsCommon problems ““Gaussianization”Gaussianization” Self-absorptionSelf-absorption

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

290 300 310 320 330

Wavelength (nm)

Irra

dia

nce

(W

/m2 )

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

290 300 310 320 330

Wavelength (nm)

Irra

dia

nce

(W

/m2 )

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

306 308 310 312 314 316

Wavelength (nm)

Irra

dia

nce

(W

/m2 )

Experiments PerformedExperiments Performed

Irradiance vs. Oxidizer flow rateIrradiance vs. Oxidizer flow rate Irradiance vs. TimeIrradiance vs. TimeMapping the plume for Mapping the plume for ··OH concentrationOH concentration

Instrumentation & SetupInstrumentation & Setup

Rocket motors PMMA

100 mm length 6.35 mm bore

Rocket stand Adjustable in two

directions

Spectrometers StellarNet EPP2000 UV-Vis StellarNet EPP2000 UV5-HR Viewing area: 8 mm2

Data Collection SoftwareData Collection Software

SpectraWizSpectraWiz Collect data from spectrometersCollect data from spectrometers Exports to fileExports to file

MatlabMatlab Integrate spectral dataIntegrate spectral data All spectra integrated from 306.24 nm to 324.57 nmAll spectra integrated from 306.24 nm to 324.57 nm Used the trapezoidal rule for integrationUsed the trapezoidal rule for integration

ExcelExcel CorrelationCorrelation IllustrationIllustration

ResultsResults

Effect of oxidizer flow rate on irradianceEffect of oxidizer flow rate on irradiance

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

0 0.005 0.01 0.015 0.02 0.025 0.03

Oxidizer flow rate (mol O2/s)

Irra

dia

nce

(W

/m2 )

Results

• Mapping the plume for ·OH radical– Measured in a 2D planar grid

• 6.35 mm spacing radially, 12.7 mm spacing axially

ResultsResults

Effect of burn time on Effect of burn time on irradianceirradiance Linear relationshipLinear relationship

ConclusionsConclusions

Effect of oxidizer flow rate Effect of oxidizer flow rate Irradiance is highest at around 0.017 mol/s OIrradiance is highest at around 0.017 mol/s O22

Mapping the hydroxyl radicalMapping the hydroxyl radical The hydroxyl radical can be found in a smaller The hydroxyl radical can be found in a smaller

envelope than the visible area of the plumeenvelope than the visible area of the plume Irradiance peaks close to 25 mm axial distance, 0 mm Irradiance peaks close to 25 mm axial distance, 0 mm

radial distanceradial distance

Effect of timeEffect of time Irradiance generally increases linearly with timeIrradiance generally increases linearly with time

Future Studies and IdeasFuture Studies and Ideas

Thrust measurementsThrust measurements Farbar, E.; Louwers, J.; Kaya, T.; “Investigation of Metallized Farbar, E.; Louwers, J.; Kaya, T.; “Investigation of Metallized

and Nonmetallized Hydroxyl Terminated and Nonmetallized Hydroxyl Terminated Polybutadiene/Hydrogen Peroxide Hybrid Rockets”, Journal of Polybutadiene/Hydrogen Peroxide Hybrid Rockets”, Journal of Propulsion and Power, Vol. 23, No. 2Propulsion and Power, Vol. 23, No. 2

Temperature measurementsTemperature measurementsSpectroscopy of other gases/materialsSpectroscopy of other gases/materials

ReferencesReferences Wilson, Edmond W., Jr.; Mackey, James E.; Keller, Brett Wilson, Edmond W., Jr.; Mackey, James E.; Keller, Brett

D.; Goertzen, Elaine J.; Clements, Sheryl A.; Rivenbark, D.; Goertzen, Elaine J.; Clements, Sheryl A.; Rivenbark, Charles F., II; Cox, Calvin; “OH Emission Spectra of Charles F., II; Cox, Calvin; “OH Emission Spectra of Hybrid Rocket Motors using PMMA and HTPB,” 41Hybrid Rocket Motors using PMMA and HTPB,” 41stst AIAA/ASME/ASEE Join Propulsion Conference, Tucson, AIAA/ASME/ASEE Join Propulsion Conference, Tucson, AZ, 10-13 July 2005AZ, 10-13 July 2005

Dieke, G.H.; Crosswhite, H.M.; 1961 Dieke, G.H.; Crosswhite, H.M.; 1961 J. Quant. J. Quant. Spectroscp. Radiat. TransferSpectroscp. Radiat. Transfer 22 97 97

de Izarra, Charles; “UV OH spectrum used as a de Izarra, Charles; “UV OH spectrum used as a molecular pyrometer”; J. Phys. D: Appl. Phys. molecular pyrometer”; J. Phys. D: Appl. Phys. 3333 (2000) (2000)

Pellerin, S.; Cormier, J.M.; Richard, F.; Musiol, K.; Pellerin, S.; Cormier, J.M.; Richard, F.; Musiol, K.; Chapelle, J.; “A spectroscopic diagnostic method using Chapelle, J.; “A spectroscopic diagnostic method using UV OH band spectrum”, J. Phys. D: Appl. Phys. UV OH band spectrum”, J. Phys. D: Appl. Phys. 2929 (1996)(1996)

AcknowledgementAcknowledgement

Arkansas Space Grant ConsortiumArkansas Space Grant ConsortiumNASA/EPSCoRNASA/EPSCoRHarding UniversityHarding UniversityDr. WilsonDr. Wilson