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  • 0NWC TP 6278

    Combustion Processes inSolid Propellant Cracks

    "byK. K. KuoM. Kumar

    S. M. KovacicJ. E. Wills

    T T. Y. Chang

    Pennsylvania State Universityfor the

    Rosearch wepartment

    JUNE 1981

    NAVAL WEAPONS CENTERCHINA LAKE, CALIFORNIA 93555

    1w wc.

    Approved or public release; distrib,tion unlimited.

    DTICELECTE,SJUL 12 i9M

    S8 2 0 7 1 2 0 ' .

    , . n .... . . .... A

  • J I

    Naval Weapons CaterAN ACT vrrY OF Th-E NAJAL MATE5IA COMMANAJ*D

    FOREWORD

    This is the final report for a research program conducted byPennsylvania State University in support of the Aerothermochemistry

    SDivision's studies of combustion processes in solid propellant cracks.Continuing support from Naval Weapons Center covered a period from1 February 1978 to 31 January 1980.

    This report was reviewed for technical accuracy by Channoa F.Price of the Aerothe,-mochemistry Division. Work was supported by NavalWeapons Center under Contract N60530-78-C0069. This report is a continu-ation of the research program on "Transient Combustion Processes inSolid Propellant Cracks," carried out in the Mechanical EngineeringDepartment of the Pennsylvania State University.

    This report is released at the working level. Because of thecontinuing nature of this research, changes may be made in the future.

    Apprcved by Under authority ofE. L. ROYCE, Head W. B. HAFFResearch Department CAPT, U.S. Navy11 June 1981 Commander

    Released for publication byR. M. HILLYER.7e:hniccl Director

    NWC Technical Publication 6278

    Published by ....... ................... ... Research DepartmentCollation ................ .................... ... Cover, 50 leavesFirst printing ............. ............. 185 unnumbered copiep

    1

  • UNCLASSIFIEDSECURITY CLASSIFICATION OF THIS PAGE (W"On Data Entered)

    REPORT DOCUMENTATION PAGE READ INSTRUCTIONSBEFORE COMPLETING FORM

    I REPORT NUM9ER 2.. GOVT ACCESSION NO. 3. RECIPIENT'S CATALOG NUMBER

    NWC TP 6278 wb~-Af I1 __ __ __--__4. TITLE 'and Subtitle) S. TYPFSAORT A PERID COVERED

    COMBUSTION PROCESSES IN SOLID PROPELLANT P

    CRACKS 1 Feb 197C - 31 Jan 1980

    6. PERAWI lO$001EP0RT NUMBER

    7. AUTHOR(4) a. CONTRACT OR GRANT NUMBER(O

    K. K. KUO, M. KUMAR, S. M. KOVACIC, J. E. WILLS,

    T. Y. CHANG N60530-7P-C-0069

    9. PERFORMING ORGANIZATION NAME AND ADDRESS 11. PROGRAM ELEMENT, PROJECT, TASK

    PENNSYLVANIA STATE UNIVERSITY AREA & WORK UNIT NUMBERS

    UNIVERSITY PARK, PENNSYLVANIA 16802 B0003-SB

    11. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE

    NAVAL WEAPONS CENTER JUNE 1981

    CHINA LAKE, CALIFORNIA 93555 i1. NUMBER OF PAGES98

    14. MONITORING AGENCY NAME & AODRESS(It different tram Controlling Office) IS. SECURITY CLASS. (of thin teport)

    UNCLASSIFIED

    ISa. O'ECLASSIFICATION 'DOWNGRADINGSCHEDULE

    16. DISTRIBUTION STATEMENT (of this Report)

    APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED

    17. DISTRIBUTION STATEMENT (of the abstract entered in Block 20, it different Ifom Report)

    Id. SUPPLEMENTARY vOTES

    19. KEY WORDS (Continue on .evorao aide it neceeaary aid Identify by block number)

    SOLID PROPELLANT -DEF LAG RATION-TO-D ETONATION TRANSITIONCONVECTIVE BURNING

    20. ABSTRACT (Continue oan revete olde If necesay and Identify by block number)

    (SEE BACK OF FORM)

    DD 1473 EDITION OF I NOV69 $I OBSOLETI UNCLASSIFIEDS/N 0102-014- 6601

    89CURITY CLASSIFICATION OF T141S PACC (Wlhen Dae iftewed)

  • UNCLASSIFIEDtLt.U$I|TY CLASSIPICATION OF THIS PAGE(Wheu Datea Enteeft)

    (U) Combustion Processes in Solid Propellant Cracks, by. K. Kuo, M. Kumar, S. M. Kovacic, J. E. Wills, and. Y. Chang, Pennsylvania State University, University Park,ennsylvania. China Lake, California, Naval Weapons Center,

    June 1981, 98 pp. (NWC TP 6278, Publication UNCLASSIFIED.)_.-(M)his report presents results of a study of combustion o

    -rocesses in solid propellant cracks. As might eej pseted,inder moderate chamber pressurization rates (

  • NWC TP 6278

    CONTENTS

    Introduction . . . 3

    Background . . . . . . &. . . . . . . . . . . . . . . . . . . . . . 4

    Theoretical Work ..................................... 5Modeling of the Crack Tip Ignition Phenomena ...... ......... 5Linkage of Crack Combustion Code and Nonlinear

    Finite Element Analysis Program ............. 20Determination of Complete Set of Dimensionless

    Paramel'ers ......... ....... ........................ ... 35

    Experimental Work ................................. 37Crack Tip Ignition Study ........ ... ................... ... 37Investigation of the One-Dimensionality of

    the Flame Front ....................... 49Effect of Propellant Crack Geometry ....... .............. ... 51

    Summary of Progress and Conclusions .......... ................ .. 54

    Bibliography ........................ ........................... 57

    Appendixes:A. Basic Definitions and Operation Rule for Favre

    Averaging .... ................... ........................ 59B. Difficulties Encountered in Obtaining Analytical

    Solutions .................................. 61C. NFAP/CCC Program Input ................... 65D. Sample Data for NFAP/CCC Combined Program .... ......... 85

    Nomenclature..... ......................... ............ 95

    Figures:1. Schematic Diagram of the Physical Model for the

    Tip Ignition Study ..... ... ... .................... ii.2. Comparison of Predicted and Measured Ignition Delays . . . 183. Calculated Heat Flux and Propellant Surface Temperature

    Vs. Time ........ 194. Calculated Temperature Distribution at Various Times . 215. Schematic Diagram of CCC and NFAP Linkage ... ....... ... 276. General Layout of the CCC and LFAP Linkage . ....... 297. Finite Element Grid ........ ... ................... ... 318. 3oundary Condition for a Test Specimen ............ 329. Calculated Pressure Distributions for Various Times

    From the Crack Combustion Code ............. 3310. Calculated Pressure Distributions for Various Times

    rom the Combined Crack Combustion and Nonlinear Finite-Element Analysis Program ..... ......... ................ 34

  • NWC TP 6278

    Figures (Contd):11. Schematic Diagram of the Test Rig for the Study of

    Propellant Ignition at the Closed End of an InertCtack . . ......................... 38

    12. Block Diagram of Remotely-Controlled Ignition andPhotography System ........... ................... ... 41

    13. Block Diagram of Data Acquisition System ... ........ .. 4214. Measured Pressure-Time Traces for Crack Tip Ignition

    Experiment (DNC Test No. 30) ......................... 4415. Measured Pressure-Time Traces for Crack Tip Ignition

    Experiment (DNC Test No. 31) ...... ............... ... 4516. Measured Pressure-Time Traces for Crack Tip Ignition

    Experiment (DNC Test No. 33) ...... ............... ... 4617. Measured Pressure-Time Traces for Crack Tip Ignition

    Experiment (DNC Test No. 41) ...... ............... ... 4718. Measured Pressure-Time Traces for Crack Tip Ignition

    Experiment (DNC Test No. 42) ...... ............... ... 4819. Geometric Configuration of the Propellant Sample Used

    in DNC Test No. 24 (All Dimensions are in mm) ......... 5020. Expanded Short-Time Pressure Traces of DNC Test

    No. 24 ................. ....................... .... 5121. Motion Pictures of the Flame Spreading Phenomenon

    for DNC Test No. 24 .......... ................... ... 52

    Tables:1. Input Variables for the Tip Ignition Computer Program . 172. Interpretation of the Motion Pictures ir Figure 213

    (DNC Test No. 24 ............. ................... ... 54 2

    0cOasrion fl For

    By_

    _Distribution/

    _.Availabillity Codes

    * 2

  • NWC TP 6278

    INTRODUCT ION

    A very important characteristic of a gas permeable solid propellantis that it undergoes the transition from normal burning to detonationunder certain operating conditions. A transition from deflagration-to-detonation (DDT) may not only cause malfunction or failure of a solidpropellant motor, but it is also a potential source of hazard. DDTusually involves very high flame propagation rates, high pressures, andlarge burning surface areas. DDT is therefore more likely to occur ingas permeable propellants, such as granular propellant beds or propel-lant grains with flaws or cracks which have large burning surface areas.

    Cracks inside solid propellant grains, which are likely to beencountered in high-energy propellants with high-solids loading, canallow hot, high pressure gases to penetrate the cavity. The combustionprocesses inside the crack can produce much higher pressure than thedesigned maximum operating pressure. If the local pressure rise due tothe gasification is sufficiently rapid, it may produce strong compres-sion waves, or even shock waves which can initiate detonation. Further-more, for DDT in damaged propellant grains with cracks, crack branching/propagation must take place to provide the additional surface area.Some experimental and theoretical studies, based purely on solid mech-anics considerations, have been conducted to predict crack propagationin solid propellant grains. However, realistic predictions of acceler-ative convective burning and crack propagation cannot be made unless acombustion program incorporating a structural analysis program is used.

    Convective burning, however, is not the only mechanism responsible

    for producing the steep pressure gradients that lead to the transitionto detonation. There are other mechanisms which may also be important Iin DDT processes. The presence of numerous ignited spots and ablating

    surfaces at some distance from the combustion zo