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  • AD-754 852

    RAMJET ENGINE FUEL INJECTION STUDIES

    John T. Hojnacki

    Air Force Aero Propulsion LaboratoryWright-Patterson Air Force Base, Ohio

    November 1972

    II

    DISTRIBUTED BY:

    National Technical Information ServiceU. S. DEPARTMENT OF COMMERCE5285 Port Royal Road, Springfield Va. 22151

  • AFAPL-TR-72-76

    RAMJET ENGINE FUEL INJECTION STUDIES

    JOHN T. HOJNACKI

    TECHNICAL REPORT AFAPL-TR-72-76

    D D C,

    NOVEMBER 1972 FEB 8 1973

    B

    Approved for public release; distribution unlimited.

    Reproduced by

    NATIONAL TECHNICALINFORMATION SERVICE

    U S Deportmenl of CommerceSprgflield VA 22151

    AIR FORCE AERO PROPULSION LABORATORYAIR FORCE SYSTEMS COMMAND

    WRIOHT-PATrERSON AIR FORCE BASE, OHIO 45433

  • NOTICE

    When Government drawings, specifications, or other data are used for any purpose

    other than In connection ,ith a definitely related Government procurement operation,

    the United States Government thereby incurs no responsibility nor any obligation

    whatsoever; and the fact that t government may have formulated, furnished, or in

    any way supplied the said drawings, specifications, or other data, is not to be regarded

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    or corporation, or conveying any rights or permission to mangfacture, use, or sell any

    patented invention that may in any way be related thereto.

    CV I2, ... ' I ,'AY A ILA 'I 1I' C O9E S

    MIE

    p.-C

    Copies of this report should not be returned unless return is required by security

    considerations, contractual obligations, or notice on a specific document.AIR FORCE/56780,18 January 1973 - 100

  • UNCLASSIFIEDSecunty Classification

    DOCUMENT CONTROL UATA . R & D(secutity classfjcation of title, body of abstract and indexnri annotation mu,%t he entered when the overall report Is clossilied)

    I ORIGINA TING ACTtVI ry (Corporate author) 20. REPORT SECURITY CLASSIFICATION

    Air Force Aero Propulsion Laboratory UNCLASSIFIEDWright-Patterson Air Force Base, Ohio 45433 2b GROUP

    3 REPORT TITLE

    RAMJET ENGINE FUEL INJECTION STUDIES

    4 OESCRIPTIVE NO :ES (Type of report and inclusive date&)

    S AU THOR(S (First name, middle initial. last name)

    John T. Hojnacki

    6 REPORT OATE 7a. TOTAL NO. OF PAGEJ 7b NO OF REFS

    November 1972 43 4Ia CONTRACT OR GRANT NO 9a. ORIGINATOR'S REPORT NUMBERISI

    b. PROJECT NO 3012 AFAPL-TR-72-76

    c. Task 301212 9b. OTHER REPORT NO(S) (Any other numbers that may he assignedthis report)

    d.

    0 CISTRIOUTION STATEMENT

    Approved for public release; distribution unlimited.

    It SUPPLEMENTARY NOTES 12 SPONSORING MILITARY ACTIVITY

    Air Force Aero Propulsion LaboratoryI Wright-Patterson AFB, Ohio 45433I3 ABSTRACT

    The purpose of this investigation was to develop empirical methods for designing a fuelinjection system applicable to sudden expansion burners using a coaxial inlet. An integralrocket/ramjet missile may utilize this type of fuel system.

    The primary objectiv, of a liquid fuel injection system is to provide the combustion cham-ber with the proper amount of fuel in a pattern that will result in efficient combustion over theflight path of the missile. The relative amounts of fuel and air at the flameholding region areimportant in determining the efficiency of combustion. This local fuel/air ratio can be esti-mated once the penetration and spreading characteristics of the fuel spray are known. Thenthe proper distance of the fuel injector from this flameholding region can be selected to obtainstoichiometric conditions there.

    From the local fuel/air ratio relationship, a family of curves was plotted, which arefunctions of downstream distance and overall fuel/air ratio. With these' curves, the injectorwas placed at the appropriate distance from the flameholding region to obtain stoichiometricconditions at that region. Subsequent tests using the AFAPL Ramjet Burner Thrust StandFacility verified that efficient combustion was achieved.

    DD 'ov 61473 UNCLASSIFIEDSecuritv Clasnification

  • UNOLASSIFIEDSecurity Classification

    4 LINK A LINK B I LINK CKEYOL ROOLE WT - - ~ ~

    ROLE WT ROLE WT iRLE AT

    Ramjets

    Fuel Injection

    Ramjet Combustor Performance

    U S uover ,ent Printing Office 1q72 - 759 489/297 UNCLASSIFIEDSecurity Classification

  • AFAPL-TR-7276

    RAMJET ENGINE FUEL INJECTION STUDIES

    JOHN T. HOJNACKI

    Approved for public release; distribution unlimited.

  • AFAPL-TR-72-76

    FOREWORD

    The work reported in this document was conducted during the period

    5 October 1970 to 15 September 1971 under Project 3012, Task 301212,

    by the Experimental Group of the Ramjet Technology Branch, Ramjet Engine

    Di-ision, Air Force Aero Propulsion Laboratory. The project engineer is

    John T. Hojnacki.

    ThiF, report was submitted by the author 1 May 1972.

    This report has been reviewed and is approved.

    EDWARD T. CURRA N, ChiefRamjet Technology BranchRamjet Engine Division

    ii

  • AFAPL-TR-7 2-76

    ABSTRACT

    The purpose of this investigation was to develop empirical methods for

    designing a fuel injection system applicable to sudden expansion burners using

    a coaxial inlet. An integral rocket/ramjet missile may utilize this type of

    fuel system.

    The primary objective of a liquid fuel injection system is to provide the

    combustion chamber with the proper amount of fuel in a pattern that will result

    in efficient combustion over the flight path of the missile. The relative amounts

    of fuel and air at the flameholding region are important in determining the

    efficiency of combustion. This local fuel/air ratio can be estimated once the

    penetration and spreading characteristics of the fuel spray are known. Then

    the proper distance of the fuel injector from this flameholding region can be

    selected to obtain stoichiometric conditions there.

    From the local fuel/air ratio relationship, a family of curves was plotted,

    which are functions of downstream distance and overall fuel/air ratio. With

    these curves, the injector was placed at the appropriate distance from the

    flameholding region to obtain stoichiometric conditions at that region. Subse-

    quent tests using the AFAPL Ramjet Burner Thrust Stand Facility verified that

    efficient combustion was achieved.

    iii

  • AFAPL-TR-72-76

    TABLE OF CONTENTS

    SECTION PAGE

    I INTRODUCTION 1

    1I TEST HARDWARE 3

    III TEST PROCEDURE 7

    IV ANALYSIS I0

    V COMBUSTOR PERFORMANCE 25

    VI CONCLUSIONS 28

    REFERENCES 29

    APPENDIX DERIVATION OF LOCAL FUEL/AIRRATIO CURVES 31

    Preceding page blank

  • A FAPL-TR-72-76

    LIST OF FIGURES

    FIGURE PAGE

    1. Schematic of Test Installation 4

    2. Sketch of Injector 5

    3. Single Pass "Z" Schlieren System 6

    4. Penetration Experiment 8

    5. Changes in Penetration with Velocity Ratio 11

    6. Mass Flow Calibration of Injector Fuel, JP-4 12

    7. Mass Flow Calibration of Injector Fuel, JP-4 13

    8. Mass Flow Calibration of Injector Fuel,Shelldyne RJ-5 14

    9. Changes in Penetration with Downstream Distance is10. Changes in Penetration with Density Ratio 17

    11. Changes in Penetration with Viscosity Ritio 18

    12. Penetration Correlation with Test Conditions 19

    13. Calculated Penetration vs. Measured PenetrationUsing Previous Investigators' Equations 21

    14. Spreading of Liquid Fuel Sprays in SubsonicAir Streams

    22

    15. Variation of Local Fuel/Air Ratio for theEngine Design of Figure 1 23

    16. Bascline Engine 24

    17. JP-4 Combustor Performance, 38, Nozzle,A /A3

    26

    18. RJ-5 Combustor Performance, 38% Nozzle 27

    vi

  • AFAPL-TR-72-76

    SYMBOLS

    a,b, c, d exponents

    X penetration distance, distance cross-stream parallelto injector axis (inch)

    Y spreading distance, width of fuel spray (inch)

    Z downstream distance parallel to air stream axis (inch)

    Pj density of liquid (lb/ft3 )

    Pa density of air stream (lb/ft3)

    V. liquid velocity (ft/sec)3

    Va air stream velocity (ft/sec)

    do orifice diameter (inch)

    a. liquid surface tension (dyne/cm)

    /1 j viscosity of liquid (lb /ft-sec)

    (f/a)1 local fuel/air ratio

    (f/a) overall fuel/air ratio

    Aa area of inlet (in2

    Af area of fuel (in )

    mf mass flow fuel (lbmI/sCC)

    Inma mass flow air (lbm/eec)

    vii

  • - - _1 - - - -------- -v--* - - ~ - -

    AFAPL-TR-72-76

    SECTION I

    INTRODUCTION

    The first part of this investigation was conducted to determine the pene-

    tration and spreading correlation which would predict most accurately the pene-

    tration and spreading that occurs in the coaxial inlet of a sudden expan3ion

    ramjet engine combustor using a single plain-stem cross-stream injector.

    Then, from the proper correlation, we drew empirical design curves which

    would position the injectors at a distance from the flameholding region for

    maximum combustion efficiency.

    Chelko (Reference 1) used a dimensional analysis involving all the variables

    that were expected to affect the penetration distance for cross-stream injectors.

    He used a single liquid (water) and a constant air stream velocity. His variables

    were orifice diameter and air stream density, He assumed that the discharge

    coefficient was equal to 1.00, which may not have been valid. He made no

    attempt to measure the spreading of the water spray. H