AD-A270 202(Distributed: August. 1993)

ANNUAL TECHNICAL REM". :,

to

US AIR FORCE OFFICE OF SCIENTIFIC RESEARCH

110 Duncan Avenue, Suite BI 15Boiling Air Force Base

Washington DC 20332-0001

AFOSR Grant No. 91-0170

TRANSPORT PHENOMENA AND INTERFACIAL KINETICSIN MULTIPHASE COMBUSTION SYSTEMS

Principal Investigator:Daniel

Period Covered: 15 February 1992 to 14 February 1993

Yale UniversityHigh Temperature Chemical Reaction Engineering Laboratory

Department of Chemical EngineeringPO Box 2159 YS, New Haven CT 06520 USA D T IC

APPROVED FOR PUBLIC RELEASE: DISTRIBUTION UNLIMITED

The views and conclusions contained in this document are those of the authors and his research colleagues and should not beinterpreted as necessarily the official policy or the endorsements, either expressed or implied, of the Air Force Office of

Scientific Research or the U.S. Government.

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TRANSPORT PHENOMENA AND INTERFACIAL KINETICS

IN MULTIPHASE COMBUSTION SYSTEMS

1. INTRODUCTION

The performance of ramjets burning slurry fuels (leading to condensed oxide aerosols andliquid film deposits), gas turbine engines in dusty atmospheres, or when using fuels from non-traditional sources, depends upon the formation and transport of small particles across non-isothermal combustion gas boundary layers (BLs). Even airbreathing engines burning "clean"hydrocarbon fuels can experience soot formation/deposition problems (e.g., combustor linerburnout, accelerated turbine blade erosion and "hot" corrosion). Moreover, particle formation andtransport are important in many chemical reactors used to synthesize or process aerospacematerials (turbine blade coatings, optical waveguides, ceramic precursor powders,...).Accordingly, our research is directed toward providing chemical propulsion systems engineersand materials-oriented engineers with new techniques and quantitative information on importantparticle- and vapor-mass transport mechanisms and rates.

The purpose of this report is to summarize our research methods and accomplishmentsunder AFOSR Grant 91-0170 (Technical Monitor: J.M.Tishkoff) during the 1-year period: 15February '92-14 February '93. Readers interested in greater detail than contained in Section 2 areadvised to consult the published papers explicitly cited in Sections 2 and 5. Copies of any of thesepublished papers (Section 5.2) or preprints (Section 5.3) can be obtained by writing to the PI:Prof. Daniel E. Rosner, at the Department of Chemical Engineering, Yale Up',versity, Box 2159Yale Station, New Haven CT 06520-2159 USA. Comments on, or examples of, the applicationsof our research (Section 3.4) will be especially welcome.

An interactive experimental/theoretical approach has been used to gain understanding ofperformance-limiting chemical-, and mass/energy transfer-phenomena at or near interfaces. Thisincluded the development and exploitation of seeded laboratory burners (Section 2.1), and newoptical diagnostic techniques (Section 2.2, Fig. 5). Resulting experimental rate data (Fig.8),together with the predictions of asymptotic theories (Section 2), were used as the basis forproposing and verifying simple viewpoints and effective engineering correlations for futuredesign/optimization studies.

2. RESEARCH ACCOMPLISHMENTS

Most of the results we have obtained under Grant AFOSR 91-0170 during 1992 can bedivided into the subsections below:2.1. TRANSPORT AND STABILITY OF AGGREGATED PARTICLES: THEORY

The ability to reliably predict the transport properties and stability of aggregated flame-generated particles (carbonaceous soot, A120 3, SiO 2,...) is important to many technologies,including chemical propulsion and refractory materials fabrication.

The Brownian diffusion-, inertial-, and optical-properties of aggregated particles, asformed in sooting diffusion flames, are quite sensitive to size (e.g. number N of "primary"particles; see Fig. 1) and morphology (geometrical arrangement of the primary particles). Neededare methods to anticipate coagulation and deposition rates of suspended populations of suchparticles, especially in combustion systems. Toward this end we have recently devloped improvedand efficient methods for predicting the Stokes drag of large 'fractal' aggregates via a spatiallyvariable porous sphere model (Figs. 1, 2). Using the Stokes-Einstein equation, the results of Fig.2 can now be used to predict the Brownian diffusivity of such aggregates in the high pressure(near continuum-) limit (proportional to the product of the reciprocal of the ordinate of Fig. 2 andN-l/DD. This approach is currently being extended to predict the thermophoretic diffiusivity ofsuch aggregates, an important quantity we have recently found to be much less sensitive to sizeand morphology than the translational Brownian diffusivity (Rosner et.al. 1992). Indeed, thisprovides the theoretical basis for the thermophoretic sampling technique being employed in ourcurrent experimental studies (Section 2.2,. These new methods/results, together with recent

results on the spread of aggregate sizes in coagulating populations, will be used to predict wailcapture rates by the mechanisms of convective-diffusion, turbulent eddy- impaction, andthermophoresis (Rosner, Tassopoulos and Tandon,1993). Also needed are methods to predictinteractions between aggregates and their surrounding vapor environment---interactions whichcan lead to primary particle growth, or bum-out. Toward this end we have also developed newand efficient methods to predict the "accessible surface area" of aggregates (expressed as afraction , il, of the true surface area in Fig. 3), including its dependence on size (N), structure(fractal dimension, Df), probing molecule reaction probability oa, and pressure level (via Knudsennumber based on primary particle diameter). Figure 4 shows the test of our "effective Damkohlernumber" correlation approach when compared with exact results of many numerical integrations(Rosner and Tandon,1993).

Also recently initiated are studies of the restructuring kinetics of aggregates - ie. thosefactors which determine the observed size of the apparent "primary particles" comprising sootparticles, and the "collapse" of surface area observed in some high temperature systems (Cohenand Rosner, 1993).

2.2. FORMATION, TRANSPORT AND STABILITY OF COMBUSTION-GENERA TED PARTICLES:lAMINAR COUNTERFLOW DIFFUSION FLAME EXPERIMENTSA manuscript descrbhing our measurements of :he thcnop ,,u ýt'c diffrsivity of flame-

generated submicron "soot" particles using a (TiCl4(g)-)seeded low strain-rate counterflowlaminar diffusion flame (CDF-) technique has just appeared (Gomez and Rosner, 1993). Aknowledge of the relative positions of the gas and particle stagnation planes and the associatedchemical environments, can be used to control the composition and morphology of flame-synthesized particles. These factors should also influence particle production and radiation fromturbulent non-premixed "sooting" flames, as discussed further in Gomez and Rosner, 1993.

To extend this work to obtain fundamental information on nucleation, growth andaggregate restructuring, during this past year we have developed an improved "slot-type" burner(Fig. 5) and introduced instruments to carry out in situ measurements of particle Brownian motion("dynamic light scattering"). We have also developed a thermophoretic sampler (Fig. 6) to extractaggregates from various positions in the seeded-CDF for morphological analysis using electronmicroscope images. Aggregate data obtained from CH4 flames seeded with titanium tetra-isopropoxide (TTIP-) vapor are now being obtained and will be analyzed using the theoreticalmethods briefly outlined in Sections 2.1, 2.3.

2.3. MULTIPHASE BOUNDARY LAYER THEORY: NUCLEATION, GROWTH. THERMOPHORESIS ANDINERTIAOur IJHMT J paper giving comprehensive results of Seeded micro-combustor

experiments, and ancillary theoretical calculations on the interesting competition between particleinertia and particle thermophoresis for the case of laminar gaseous boundary layers on surfaceswith streamwise curvature (e.g., turbine blades), should appear this Fall (Konstandopoulos andRosner, 1993).

We are now carrying out theoretical studies on the structure of thin reaction-nucleation-coagulation 'sublayers' within laminar boundary layers, including stagnation flows similar tothose achieved in our counterflow burner (Fig. 5) and CVD-impingement reactor (see Fig. 7below).

An account of our recent studies of the unusual population dynamics of coagulatingabsorbing-emitting particles in strong radiation fields is about to appear in Aerosol Sci. Tech.(Mackowski et.al., 1993). For a useful overview of our recent work on these and other effects ofenergy transfer on suspended particle dynamics, see Rosner, et. al., 1992, which was included asan Appendix to our last OSR Annual Report.

2.4. KINETICS AND MORPHOLOGY OF CVD-MATERIALS IN MULTI-PHASE ENVIRONMENTSA small impinging jet (stagnation flow) reactor (Fig. 7) is being used to study the chemical

vapor deposition (CVD-)-rates of refractory layers on inductively (over-)heated substrates(Collins, Rosner and Castillo,1992,1993). These measurements, initiated with the co-sponsorship of NASA-Lewis Labs, are being used to understand deposition rates and associated

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polydispersed populations of aggregated particles incombustion gases.

3

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sponsorship of NASA-Lewis Labs, are being used to understand deposition rates and associateddeposit microstructures observed in highly non-isothermal, often particle-containing local CVDenvironments. Figure 8 shows (logarithmic ordinate) our apparent first order deposition rateconstants vs. reciprocal surface temperature for TiO2(s) obtained from TTIP(g). The dark pointsshow our predicted surface temperatures for the onset of vapor phase reactions ("vapor phaseignition"(VPI)) within the boundary layer and the onset of vapor phase diffusion control of theheterogeneous reaction(Castillo and Rosner, 1993).

In our OSR-sponsored Yale HTCRE Lab research during the past year, briefly reviewedhere, we have shown that new methods for rapidly measuring particle transport rates, combinedwith recent advances in boundary layer theory, provide useful means to identify and incorporateimportant, but previously neglected, mass transport phenomena in many propulsion engineeringand ma- :-ials engineering design/optimization calculations.

Despite the formidable complexities to be overcome in the design and operation of air-breathing propulsion power plants utilizing a broad spectrum energetic fuels these particulartechniques and results are indicative of the potentially useful simplifications and generalizationswhich have emerged from our present fundamental AFOSR-funded research studies ofcombustion-generated particle transport mechanisms. It is hoped that this Annual Report and itssupporting (cited) papers will facilitate the refinement and/or incorporation of some of the presentideas into engineering design procedures of much greater generality and reliability. This work hasalready helped identify new directions where research results would have a significant impact onengineering pi ctice in both the defense and civilian sectors of the US economy (Section 3.4).

3. ADMINISTRATIVE INFORMATION:PERSONNEL, PRESENTATIONS, APPLICATIONS,

"COUPLING' ACTIVITIESThe following sections summarize some pertinent 'non-technical' facets of the

abovementioned Yale HTCRE Lab/AFOSR research program:3.1 Personnel

The present results (Sections 2 and 5) are due to the contributions of the individuals listedin Table 3.1-1, which also indicates the role of each researcher and the relevant time interval ofthe activity. It will be noted that, in addition to the results themselves, this program hassimultaneously contributed to the research training of a number of students and recent PhDs, whowill now be in an exceilent position to make future contributions to technologies oriented towardair-breathing chemical propulsion, and high-tech materials processing.

Table 3.1-1 Summary of Research Participantsa on AFOSR Grant:TRANSPORT PHENOMENA AND INTERFACIAL KINETICS

IN MULTIPHASE COMBUSTION SYSTEMS

Name Statusa Date(s) Principal Research ActivitybAlbagli, D. PDRA 4/92- particle production in CDFsCohen, R. D. '1S 1,2/93 aggregate restructuring theoryCollins, J. GRA '92,'93 CVD of ceramic coatingsGomez, A. Asst.Prof. '92 Ms. on particle transp. props.(CDFs)Kho,T. GRA '92,'93 chemical vapor infiltration (coatings)Papadopoulos, D GRA '92 transport phenomena in CVD reactorsRosner, D.E. PI '92-'93 program direction-dep. theory/expSilverman, I. PDRA '92-'93 spray evap/comb, at high pressuresTandon, P. GRA '92-'93 transport phenomena in BLs and CDFs

a PDRA=Post-doctoral Research Asst GRA= Graduate Research AssistantPI = Principal Investigator VS = Visiling Scholar

b See Section 5 for specific references cited in text (Section 2)

5"

3.2 Cooperation with US IndustryThe research summarized here was supported by AFOSR under Grant 91-0170 (2/15/92-

2/14/93). The Yale HTCRE Laboratory has also been the beneficiary of continuing smaller grantsfrom U.S. industrial corporations, including GE-Schenectady, DuPont, and Shell as well as thefeedback and advice of principal scientists/engineers from each of these corporations andCombustion Engineering-ABB and Textron. We appreciate this level of collaboration, and expectthat it will accelerate inevitable applications of our results in areas relevant to their technologicalobjectives (see, also, Section 3.4, below).

3.3 Presentations and Research TrainingApart from the publications itemized in Section 5 and our verbal presentation (of progress)

at the regular AFOSR Contractors Meeting (6/18/92, La Jolla), our results have also beenpresented at annual or topical conferences of the following professional organizations:

Int. Fine Particle Res. Inst. (6/2/92; Harrogate England))AIChE (1 1/3192; Miami FL)

In addition, during the period: 2/15/92 -2/14/93, the PI presented seminars at thefollowing Universities:

U Manchester Inst.Sci.Tech. 5/28/92 Leeds 5/29/92 Penn State (7/28/92)

Brown (9/22/92) Notre Dame (10/27/92)

In all, a total of 8 external talks were given based in part on the results of this AFOSR researchprogram.

This program involved the PhD dissertation research of two Yale graduate students (J.Collins and P. Tandon; cf.Table 3.1-1). Indeed, J. Collins is expected to complete his PhDdegree requirements in Fall '93.

3.4 Some Known Applications of Yale-HTCRE Lab Research ResultsIt has been particularly gratifying to see direct applications of some of this generic

AFOSR-supported particle and vapor mass transfer research in more applications-orientedinvestigations reported in recent years. Indeed, the writer would appreciate it if further examplesknown to the reader can be brought to his attention.

In the area of multicomponent vapor deposition in combustion systems additionalapplications of our predictive methods (for "chemically frozen" (Rosner et.al., 1979) and LTCEmulticomponent laminar boundary layers) continue to be made by British Coal Corporation-Power Generation Branch (I. Fantom, contact) in connection with their topping cycles which rungas turbines on the products of fluidized bed coal combustors/gasifiers. The writer has alsoproposed applications of our computational methods to Aerojet Propulsion Div. ( D.M.Jassowski ) in connection with predicting the chemical stability of iridium rocket nozzle coatings.Our Poster in the 1988 Combustion Symposium (Seattle) appears to have motivated Prof. Takeno(Nagoya) to initiate experiments using a laminar counterflow diffusion flame to estimate thethermophoretic diffusivity of LDV seed particles. Our paper on the experimental determination ofsmaller aggregated particle thermophoretic diffusivities using laminar CDF/LDV/Laser LightScattering techniques is nearing completion, and will be submitted to Combustion Science andTechnology early in our next year's program. Also, in combustion research many groups (eg.Dobbins et.al. (Brown U.), Faeth et.al. (U. Mich.), Katz et al. (J.Hopkins U.)) are now utilizing"thermophoretic sampling" techniques to exploit the size- and morphology-insensitive captureefficiency characteristics that we have proven in our AFOSR research (Section 2.1).

Explicit examples are provided in ongoing work at MIT (Walsh et.al. 1992), and SandiaCRF, both groups having incorporated our rational correlation of inertial particle impaction (e.g. acylinder in cross-flow) in terms of an effective Stokes number. This PI was also pleased toconfirm recent applications of our AFOSR and DOE-supported research (on the correlation ofinertial impaction by cylinders in crossflow) by the National Engineering Laboratory (NEL) ofGlasgow Scotland (Contact: Dr. Andrew Jenkins). NEL is apparently collaborating with

6

Marchwood Labs-CEGB on developing mass-transfer prediction methods applicable to waste-heat recovery systems in incinerators, as well as pulverized coal-fired boilers. These applicationsare somewhat similar to those reported by the Combustion Lab R&D group at MIT and PennState U.

As mentioned last year, explicit use of our studies of self-regulated "capture" of incidentimpacting particles (Rosner and Nagaragan, 1987) is being made in current work on impactseparators and ceramic heat exchangers for coal-fired turbine systems in high performancestationary power plants. Other potential applications arise in connection with "candle filters" usedto remove fines (sorbent particles,...) upstream of the turbines. A useful summary of work inthese interrelated areas (Solar Turbines, Textron Defense Systems, Hague International_...) waspresented at the Engineering Foundation Conference Inorganic Transformations and AshDeposition During Combustion. , the proceedings of which appeared during this past year.

Clearly, fruitful opportunities for the application of our recent "non-Brownian" convectivemass transfer research now exist in many of the programs currently supported by the US AirForce, as well as civilian sector R&D.

4. CONCLUSIONS

In the OSR-sponsored Yale HTCRE Lab research during the period: 2/15/92-2/14/93,briefly described above, we have shown that new methods for rapidly measuring particle-masstransfer rates , combined with our recent advances in mass transport theory, provide useful meansto identify and incorporate important, but previously neglected, mass transport phenomena inmany propulsion engineering and materials engineering design/optimization calculations. Oneimportant class of examples involve our treatment of aggregated particle transport phenomt 'ia(Section 2.1)

Despite formidable complexities to be overcome in the design and operation of mobile andstationary power plants utilizing a broad spectrum of energetic fuels the abovementionedtechniques and results (Section 2) are indicative of the potentially useful simplifications andgeneralizations emerging from our present fundamental AFOSR-funded research studies ofcombustion-generated particle transport mechanisms and interfacial reactions relevant to thesynthesis of refractory materials. It is hoped that this Annual Report and its supporting papers(Section 5) will facilitate the incorporation of many of the present ideas into design and testprocedures of greater generality and reliability. This work has also helped identify new directionswhere it is anticipated that research results will have a significant impact on future DOD andcivilian sector engineering practice.

5. REFERENCES

5.1 CITED BACKGROUND PUBLICATIONS (Predecessor OSR, DOE- Grants)

Castillo, J.L., Garcia-Ybarra, P., and Rosner, D.E.,"Morphological Instability of aTher'-rophoretically Growing Deposit", J. Crystal Growth 116, 105-126, (1992)

Eisner, A.D. and Rosner, D.E., Experimental Studies of Soot Particle Thermophoresis in NonIsothermal Combustion Gases Using Thermocouple Response Techniques", Combustion andFlame 61, 153-166(1985); see, also: J PhysicoChemical Hydrodynamics (Pergamon) 7,91-100 (1986)

Rosner, D.E. and Kim,S.S., "Optical Experiments on Thermophoretically AugmentedSubmicron Particle Deposition From 'Dusty' High Temperature Gas Flows", The ChemicalEngrg. J.(Elsevier) 29,[3], 147-157 (1984)

Rosner, D.E. and Nagarajan. R.,"Toward a Mechanistic Theory of Net Deposit Growth fromAsh-Laden Flowing Combustion Gases: Self-Regulated Sticking of Impacting Particles andDeposit Erosion in the Presence of Vapor 'Glue"', Proc. 24th National Heat Transfer Conf.,AIChE Symposium Series, Vol. 83 [257], pp. 289-296, (1987)

7.

Rosner, D.E., Mackowski, D.W,. Tassopoulos,M., Castillo,JL., and Garcia-Ybarra, P.,"Effects of Heat Transfer on the Dynamics and Transport of Small Particles in Gases", I/EC -Research (ACS) 31,760-769 (1992)

Rosner, D. E. , Chen B.K., Fryburg G.C. and Kohl F.J., Chemically Frozen MulticomponentBoundary Layer Theory of Salt and/or Ash Deposition Rates from Combustion Gases",Combustion Science and Technology 20, 87-106 (1979)

Rosner, D.E., Transport Processes in Chemically Reacting Flow Systems,Butterworth-Heinemann, Stoneham MA, 1986; 3d Printing 1990.

Sung, C.J., Law, C.K., and Axelbaum, R.L., "Thermophoretic Effects on Seeding Particles inLDV Measurements of Flames", Combustion Science and Technology (submitted, 1993)

Walsh, P.M., Sarofim, A. F., and Beer, J.M., "Fouling of Convection Heat Exchangers byLignitic Coal Ash", Energy and Fuels (ACS) 6 (6) 709-715 (1992)

5.2 PUBLICATIONS WHICH APPEARED* BASED IN PART ONAFOSR 91-0170

Collins, J., Rosner, D. E. and Castillo, J.L., "Onset Conditions for Gas Phase Reaction andNucleation in the CVD of Transition Metal Oxides", Materials Research Soc. SymposiumProceedings Vol. 250, MRS (Pittsburgh PA) (1992), pp. 53-58

Gomez, A., and Rosner, D.E.*, "Thermophoretic Effects on Particles in Counterflow LaminarDiffusion Flames " Combustion Science and Technology 89, 335-362 (1993)

Gomez, A., Rosner, D.E. and Zvuloni, R., "Recent Studies of the Kinetics of Solid BoronGasification by B203(g) and Their Chemical Propulsion Implications", Proc. 2d Int. Sympos.on Special Topics in Chemical Propulsion: Combustion of Boron-Based SolidPropellants and Solid Fuels, (1993), pp 113-132.

Rosner, D.E., Konstandopoulos, A.G., Tassopoulos, M., and Mackowski, D.W, "DepositionDynamics of Combustion-Generated Particles: Summary of Recent Studies of ParticleTransport Mechanisms, Capture Rates, and Resulting Deposit Microstructure/Propertie s",Proc. Engineering Foundation Conference: Inorganic Transformations and AshDeposition During Combustion, Engineering Foundation/ASME, New York (1992); pp.585-606

5.3 PAPERS IN PREPARATION OR SUBMITTED FOR PUBLICATION

Albagli, D., and Rosner, D.E., "Factors Governing the Accessible Surface Area of Combustion-Generated Ultrafine Particles" (in preparation, 1993)

Cohen, R. D., and Rosner, D. E. , "Kinetics of Restructuring of Large Multiparticle Aggregates"(in preparation 1993)

Castillo, J. L. and Rosner, D.E., Role of High Activation Energy Homogeneous ChemicalReactions in Affecting CVD-Rates and Deposit Quality for Heated Surfaces", in preparation,

1093)Konstandopoulos, A.G. and Rosner, D.E.,"Inertial Effects on Thermophoretic Transport of

Small Particles to Walls With Streamwise Curvature---I. Experiment, IH. Theory", Accepted1993 Int. J. Heat Mass Transfer (Pergamon)

Konstandopoulos, A.G., Labowsky, M J., and Rosner, D.E., "Inertial Deposition of PirticlesFrom Potential Flows Past Cylinder Arrays", J. Aerosol Sci (Pergamon Press) 24 (4) 471-483 (1993)

Mackowski, D.W., Tassopoulos, M. and Rosner, D.E.,"Effect of Radiative Heat Transfer on theCoagulation Dynamics of Combustion-Generated Particles", (Accepted 1992; Revisionsubmitted to Aerosol Sci. Technol.(AAAR) (1993))

*During this reporting period; Full papers are reproduced in Section 6 (with Forms 298)

• m Ii II II

Park, H.M., and Rosner, D.E., "Thermophoretically Induced Phase Separation in Highly-Loaded 'Dusty' Gas Mixtures"(Revised version of HTCRE #162, in preparation 1993)

Rosner, D. E., Collins, J. and Castiilo, J.L., "Onset Conditions for Gas Phase Reactions andParticle Nucleation/Growth in CVD Boundary Layers", submitted for Int. Conf. on CVD(XII), 1993.

Rosner, D.E. and Tandon, P., "Diffusion and Heterogeneous Reaction in Large Multi-partiucleAggregates; Calculation and Correlatior, " 'Accessible' Surface Area", (accepted; to appearAIChE J. Winter '93-'94)

Rosner, D.E., Tassopoulos M., and ";, --don, P. , "Sensitivity of Total Mass Deposition Rate andResulting Deposit Microstructure to Morphology of Coagulation-Aged Aerosol Populations ofAggregated Primary Particles", in preparation, 1993)

Zuloni, R., Rosner, D.E., and Gomez, A., "High Temperature Kinetics of Solid BoronGasification By its N-ligher Oxide B203(g): Flow Reactor Techniques, Rate Measurements andTheir Chemica' "mplications", J. Phys. Chem. (to be submitted, 1993)

LIST OF ABBREVIATIONS

BL Boundary layer CDF Counterflow diffusion flameCVD Chemical vapor deposition CRF Combustion Research FacilityLDV Laser Doppler Velocimetry LTCE local thermochemical equilibriumMRS Materials Research Society TTIP Titanium tetra-isopropoxide

6. APPENDICES (Complete Papers Published During 2/15/92-2/14/93Period; including Form 298 for each)

HIGH TEMPERATURE CHEMICAL REACTIONENGINEERING LABORATORY

YALE UNIVERSITYBOX 2159, YALE STATION

NEW HAVEN, CONNECTICUT 06520 U.S.A.

= = = i i i i i i i i9

1.AGNC RUEPO RTY DOCUMb~n) ENOTDATEIO. PA EPOTTP N AE OE

f l p erhCAt'Sympos. Proc.-MRSMUITL AND S#JW1IU IS. PUMO~G NU641BRS

ONSET CONDITIONS FOR GAS PHASE REACTION AND NUCLEATION PE - 61102FIN THlE CVD OF TRANSITION METAL OXIDES PR - 2308

L AWTOACS)SA -BSS. G -AF0SF,. 9)-01-70

J. Collins .D.E. Rosner and 3. Casliflo

7. PUAIOMG ORGANIZATION NAME(S) AND ADONESW4S) IL PERFORMING ORGANIZAT'1ON

HIGH TEMPERATURE CHEMICAL REACTION REMIRT MIJSMSR

ENGINEERING LABORATORYYALE UNIVERSITY

BOX 2159, YALE STATIONNEW HAVEN, CONNECTICUT 06520 U.S.A. __________

S. SPONiSOMGfMONrYORAING AGENCY NAME(S) AND ADDAISESIS) Is. SPONSORING /moNftTORINGAGENCY REPORT NUMIER

AFOSR/NA110 Duncan Avenue, Suite L115Bolling AFB DC 20332-0001

i1. S4JPftLWNTARy NOTES

USa. DESTRU4ITONAVAILASIUT STATEMENT 121L OISTRISUT)ON CoDE

Approved for public release; distribution isunlimited1

13. ABSTRACT (MAmjumw 200 woirs

A combined experimental/theoretical study is presented of the onset conditions for gasphase reaction and particle nucleation in hot substrate/cold gas CVD of transition metal oxides.Homogeneous reaction onset conditions are predicted using a simple high activation energyreacting gas film theory. Experimental tests of the basic theory are underway using anaxisymmetric impinging jet CVD reactor. No "vapor phase ignition" has yet been observed in theTiCL1JO2 system under accessible operating conditions (below substrate temperature T.= 1700) K)and funher experiments are planned using more reactive feed materials. The goal of this researchis to provide CYD reactor design and operation guidelines for achieving acceptable depositmicrostructures at the maximum deposition rate while simultaneously avoiding homogeneousreactiorn/ucleation and diffusional limitations.

i4. SURJECT Tim"S IL. NUMUS Of PAGES

chemical vapor deposition, vapor phase ignition, metal oxide films 4chemical reaction engineering , convecti ve-d iffus ion, Soret mass transport % MK c0ot

17' SECURJY CLSIFICATION IL SECQJRI¶ CLASS FCTIM III. SEldorTY CASSROCAI*N 30. UWTATION OF ABSTRACTOF RIPORT OF THIS PAGE OF AASTIIACTUnclassified Unclassified Unclassified UL

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1.ANNY s NY LalsREPORT DA&3 1POUIT TV P1 AND DATES COV9111111993Il~f~ij;ý-CombSciTcch.89 335-362

C. TFlL! AND SUSIBITT L. PUNOGQ NMIWESM

Thermcophoretic Effects on Particles in Counterfiow PE - 61102FLaminar Diffusion Flames PR- 2308

IS. AUTHOR(SI SA- ESG -APOS5? 91-0u70

ALESSANDRO GOMEZ and DANIEL E ROSNER

7. P5.BFOOA G ORGANIZATION NAME(S) AND ADORE11SMES) A. PERFORMIING ORGANIZA71ION1

HIGH TEMPERATURE CHEMICAL REACTION Al" NUMIER

ENGINEERING LABORATORYYALE UNIVERSITY

BOX 216~9, YALE STATIONNEW HAVEN, CONNECTICUT 06520 U.S.A.

9. SPOMSOiNG/MONITORaNG AGENCY NAME(S) AND6 ADORESS4ES) to. iPowsoRING/motoITOmRJNAGENCY REPORT NUMBER

AFOSR/NA110 Duncan Avenue, Suite L115Boiling AFB DC 20332-0001

11. SWPP15.MLNTAR'V NOTES

112s. OGSTRUUTONI'AVAILAIIllT STATEMENT 121. OISTRABUT1ON Cool

Approved for public release; distribution isunlimited

13. ABSTRACT (Meiaarmfifi 200words)

Abstract-lTrerrrtphoresis. meanin~g particle drift dowri a local eas temperature gradmitn. is no- knwnto be important to manyv combustion-relaid technologies Until no*. howeser. n., dirctciteperimcniatdeterminations of primary 3nd aggregated particle therniophoretic dliftnuivtties. 1,irDl,.. in high iemperaturccombustion environment, have heen reported To pertorm such measurenments. we selected a seeded larmnarcounierfiow diffusion name tCDF1 operated at low sirain-rate as a well-defined combustion svstem. offerinitat the same time a low vetocirs and high wemnperature gradient environmeni. Vie enralilished a CH, 0, Inertopposed jet diffusion flame in* which the gaseous tueloesngen ratio. and the diluenst flow rate% were adjustedto obtain a flat, stable flame. approximately coincident with the gas stagnationi plane IGSPI Particles fedto Or formed on either or both sides of the GSP move toward this plane until the local aual selccits isexacit v counterbalanced by the thermophoretic velocity As a result of this dynamic "equilibrium" condition, apatrick stagnation plane IPSPI is established on one "r both sides of the GSP. resultinig in the formation sif areadtiy othscrsabfe "dust-free" zone Dramatic confirmation of this phenomenon is orfered by using tlaer-sheetvisualization Of the region. which reveals a thick dark zone, the dust-tree volume, thaticontrasts wit thebright parti'cle-laden regions. This -phase separation- phenomenon allowed u" to determine TvO' particletheernophoreli difftasvtrrrs by: it measuring the temperature field using tntlemcpis jeasuringthe thickness of the dark zone it e. FSP-posilionsl using laser light scatterine, and iti) measuring. computingthe asial gaseous convective velociry at ihe particle stagnation planelsl. Experimnents and calciulatrirns indicatequantittv agreement berween these measurements and kinetic theory pred-ctions for isolated spheres at

Kn.~Iin the case of CH,10O4N, diffusion names Replacement of N, with He as diluent resulted in amuhthicker and more readily meaisurable particle-free laver, but yielded Zinly qualitative agreement with the

theory, because of uncertainties in the gas composition in the flamne, As well at posssible cointrihutioni% tromsimsultaneous diflusiophonrtic mechanisms. In somne 'hootking diffusion flames, and in lyiviheists flames in whichpairticlets are the desired products, both laminar and turbulent, it is Shown that thermophoresis can influence

article residence times in the decisive region where nucleation, growth. coagulation, sintering and oxidationoccur. as well as particle temperatures, which influence panicle morpholoic and radiative heat tiaids Vikebnefly discuss the non-premised comtbustion conditions under which thes theirtnophoretically-induced effectsare litkely to be appreciable.

14. SulJC EM IS. NUMBER OF PAGES

Keny Words Aerosols, Soot. Aggregated Particles. Gasous Ditfusiuri Flames, Throhrss r-.in¶.PWECDDiffusion. Flame Synthesis of Fine Particles. Aerosol Reaction Engineering _Trohri.Bona 6 R 1C0

SI? SCURITY CLASSIFICATIION I AL O SECRdTY CLASSIFICATION1 9. SICU111Y7 CIASIWIATIQNif 20. LMIATION Of ABSTRACTOf RIPOIRT I of THIS PAGE OF ABSTRACT .Unclassified Unclassified Unclassified UL

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REPORT DOCUMENTATION PAGE OUS No 7408

1treffet F, ~ to ".pw .i¶Isw~of 0"nqwof 4W WON ot 1 0"j~

1. AGENCY VII ONLY (Leave blank) 3. REPORT OATS 3. REPORT TYPE AND DATM COVERED1"3 T Book chapter ()Zep,. 4t)

A. TITL AND 54J5TITU L PUNDOG NUhARSRECENT STUDIES OFTilE KINETICS OF SOU D IIBORlONGASIFICATION By 11203(g) AND THEIR CHIEMICAL. PE - 61102F

P1ROPULSION IMPLICATIONS PR- 2308L LTHW SA- BS

G - AFOSR 91-0170ALESSANDRO GO0NIIZ , DANIEL. E. ROSNERt AND) lONI ZVUt.ONI

7. PEA*50UG ORANIMZATION NAME(S) AND ADDRISS4ES) L. PERFORMING ORGANIZA~iONHIGH TEMPERATURE CHEMICAL REACTION IPOOT NUMBER

ENGINEERING LABORATORYYALE UNIVERSITY

BOX 2159, YALE STATIONNEW HAVEN, CONNECTICUT 06520 U.S.A. __________

9. SPONSOICIGINIONITOUlNG AGENCY NAMI(S) AND ADORESS4ES) S0. SPONSORiNG I MOWlOPINGAGENJCY REP'ONT NUMEIA

AF'OSR/NA110 Duncan Avenue, Suite E.115_Boiling AFB DC 20332-0001

Ii. SUPPLEMENTAXY N YTESin Proc. 2d Int. Sympos. on Special Topics in Chemical Propulsion: (K.K.Kuo, R.Pein, eds)Combustion of Boron-Based Solid Propellants and Solid Fuels, pp 113-132.CRC Press (Boca Raton)__ __________

Ill. INSTRNUTIONIAVACLAIRUT STATEMENT Ilab. DSTROUTION CODE

Approved for public release; distribution isIunlimitedI

I I. AASTRACT (Maximum 20Q wov*j

Interfacial kinetics arc likely to play a ratc-limiting role in (hc combustion ofsmall boron particles and yet little is known about boron gasification byB203(g), which may bý important because of its formation from 02 in theboundary layer near 'he gasifying surface. For these reasons, intrinsickinetics of the high temperature B20 3(g)1J3(s) reaction were investigatedutilizing newly designcd flow reactor techniques, together with a 'real-time'(boron) clement detection technique based on microwave-induced plasmaemission spectroscopy. Known amounts of tile gaseous reactant 13203 weregenerated using a resistively heated Knudsen effusion source operating in ahigh velocity argon gas background. Reaction rate measurements on a joule-healed boron filament covered the surface temperature interval 1330-2050 Kat B3203 partial pressures between 6.10-3 and 6.10-2 Pa.

Thiese kinetic data are used to discuss the expected sequence of rate-controllingProcesses for the combustion of an individiuaJ B(s) particle in air under typicalramjet conditions

I Sultc? ERMSIS. NVUMIE* Of PAGES

Iboron combustion, boron particle ignition, extinction; flow reactor, .

gasification kinetics, boric oxide vapor, plasma emission spectroscopy . "CCO

1?7 SICURMT CLASIIPICATO*"N I I SECURfTY CLASSWIICATION Is. SECLWMT O.ASSJPCATbOU0 30. LOMTATION OF AISTRACTOF RIPMh OF TinS PAGE Of "$TRACT

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REPORT DOCUMENTATION PAGEPA Mwin eI aIt"I" of U~ W#W %weew 10 imp te~ 'Vw ow'waw OWN Nem' .w -.111M

= 00. 0111 - _- eg -iW q tmao~ ofl WHOM'I " S swafwaeft mImsOi go O.W. tilt= 9 tii m 0tN00 W!f 14= Oma of~t am'0 'wg~ ~

1.AEMIUECLTLc.bg~ .REOTDT EOT P1AD01 OEE Book chapter

& TIT AMD SUITITL L FulNaonG NU tagDEPOSITION DYNAMICS OF COMBUSTION-GENERATED PARTICLES.

SUMMARY OF RECENT STUDIES OF PARTICLE TRANSPORT MECHANISMS, PE - 61102FCAPTURE RATES AND RESULTING DEPOSIT MICROSTRUCTURE/PROPERTIES PR - 2308

L AUTHOWSA-EBSG -AFOSR 91-0170

D. E. Rosner, A. G. Iconstandopoulos, M. Tassopoulos.

and D. W. Mackowski

7. PLO*MANGORGAXIZATION NAME(S) AND ADORESS4ES) L nVROWM6 osGANUAT1ONHIGH TEMPERATURE CHEMICAL REACTION USP@* Wuua&

ENGINEERING LABORATORYYALE UNIVERSITY

BOX 2`159, YALE STATIONNEW HAVEN, CONNECTICUT 06520 U.S.A. __________

*. SPONSO61111GIM NIORING AGENCY NAME(S) AND *00*555415) 16. SPONSORUSGMOWTIG

AF10SR/NA tI RPWWW1

110 Duncan Avenue, Suite E115Bolling AFB DC 20332-0001

111. S4IPFEMNAMRV NOTESin Proc. Engineering Foundation Conference: Inorganic Transf'ormations and Ash

Deposition During Combustion, Engineering Foundation/ASME, New York (1992); pp.585-606 ____________

124. OESTRIPUTONIAVALAUR.IMY STATEMENT -~b 1 S1 6RolPJI COM

Approved for public release; distribution isunlimited

I13. AASTRACT (Mewmnum 200 waro

We review here some of the principal results of our recent research directed towardsunderstanding and predicting the depo riuon dy'ap*5c of com~bujyion-generated particles in fossi-fuelpower production technologies. In view of our previous review papers (Engineering FoundationSymposia. ASME-HTD and J. PCH, loc.cit.). which explicitly dealt with dense spherical particles,isolated targets and vapor-particle interaction% prior to deposition, the specific topics emphasized inthis overview arr.

Brownian diffusion-. therophotetic. and inenial-properties of aggregated particles

Effects of pariicle sine Mtectrrm and Awrphviagy on total deposition rates

Combined effects of Menta van Ahennephrensi for surfaces with streamwise curvature

Prediction and crea. of oinertial particle captunt by fliwd-dynasnscallyinteracting cylinders in ctosa-flow

Micni-methanieal Aspects of anivingpoancls capaeur and associated depow Sr'owth

computer simulation of panicle deposition nVechardrnlde pozsi Inicrstrucowe1p'opeaijv inerreladons

i.SUNICT TEPRMS IS. NUMBER Of PAGES

Key Words. Aerosols, Soot, Aggregated Particles, Gaseous Diffusion f'lames, Thermophoresis. Brownian I ZDiffusion. Flame Synthesis (it Fine Particles, Aero-ol Reaction Engineering 1 M C004

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