A~D-R147 874 A SHOCK TUBE POWDER DISPERSAL UNIT(U) ARMY BALLISTIC i/iRESEARCH LAB ABERDEEN PROVING GROUND MDL J DECKER ET AL. OCT 84 BRL-MIR-3393 BBI-AD-F388 585

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' BR MEMORANDUM REPORT BRL-MR-3393

L4.

A SHOCK TUBE POWDER DISPERSAL UNIT

Leon J. DeckerArthur Cohen

Emmett Donnelly

October 1984

KO.-TE3J 1A;84

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*US ARMY BALLISTIC RESEARCH LABORATORY!i ,ABERDEEN PROVING GROUND, MARYLAND

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1. REPORT NUMBER 2. GOVT ACCESSION NO. RECIPIENT'S CATALOG NUMBER

MEMORANDUM REPORT BRL-MR-3393 - 6J-' ? _:_ __,_|

4. TITL (wid Sbtitln FYlF REPORT & PERIOD COVERED

A Shock Tube Powder Dispersal Unit

6. PERFORMING ORG. REPORT N.MBER

7. AUTHOR" S. CONTRACT OR GRANT NUMBEr(.s* Leon J. Dcker

Arthur Cohen• "Emmett Donnelly

9. PERFORMIN GRGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT. PROJECT, TASK* US Army Ballistic Research Laboratory AREA b WORK UNIT NUMBEPS

ATTN: AMXBR-IBD IL161102AH43. Aberdeen Proving Ground, MD 21005-5066

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€" IS. SUPPLEMENTARY NOTES

12. OKY OS (Continue on revere* side If neceeary and identify by block number)

,. Dusty Gas

*20. Aftrf ACr rcoatene rev.erse old# It neey mod Identify' by block number) tltA simple device for producing a dusty gas at the end wall of a shock tube

*prior to the arrival of the test shock wave has been produced and tested.It is readily adapted to existing equipment with minimal modifications.

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TABLE OF CONTENTS

Page

I* INTRODUCTION. . .. .. .. .. .. . ... . .. ..... **...**.*...****... *****.5

I. EXPERII4ENTAWuRESULTS .......................... ...

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Accc>~iri o r

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I. INTRODUCTION

It is advantageous to use reflected shock waves to study the chemicalreactions of powdered materials at high temperatures and pressures in shocktubes. Difficulties in interpretation of experimental results areconsiderably reduced when the powders are uniformly distributed as a dusty gas

* adjacent to the end wall of the tube. This unit provides a means of formingsuch a gas at time which can be varied prior to arrival of the shock wave.Dusty gases have been produced in shock tubes by using the incident shock flowto disperse powders from aerodynamic foils (knife-edge, contoured disk, etc.)or thin films. These techniques are capable of generating a dusty gas in thetest section of the tube, but the powder cannot be uniformly distributed near

* the end wall, and the formation times are controlled solely by the arrival ofthe incident shock wave. Tests thus made can only approximate desiredconditions.

Woodburn, Everson, and Kirk' used a vertical shock tube with a blower andsolenoid valve assembly at the end wall to produce a dusty gas in situ priorto shock initiation. The solenoid valves were located in the end and sidewalls respectively and were closed imediately before shock initiation.

The powder dispersal unit described herein generates a gaseous suspensionof solid particles in the volume adjacent to the end wall of the shock tube,creating the desired dusty gas experimental condition prior to the arrival ofthe test shock wave. This device provides the test conditions that thevarious shelf/knife edge/diaphragm techniques only approximate. It can bereadily incorporated into existing shock tubes through a simple end-platemodification. Modifying a shock tube by placing it in a vertical plane andadding solenoid valves requiring end-plate and side wall modifications isconsiderably more costly and, in our facility, physically impossible.

II. EXPERIMENTAL/RESULTS

A schematic of the dispersal unit is shown in Figure 1. Photographs ofthe unit are shown in Figures 2, 3 and 4. The initial shock wave is used togenerate a time-delayed gated pulse which is conducted through a brass contact(7) into an electrical primer (6) detonating the primer 1 to 5 ms prior to thearrival of the incident shock wave at the end wall of the shock tube. Thistiming ensures that the dust will be thoroughly and uniformly dispersed intothe test gas at the time of shock reflection. The detonation of primer (6)drives lexan piston (5) down the smooth bored cylinder (17) contained vithinthe main body (14) of the device. As the leading edge of piston (5) -passesvent port (12), the gases in cylinder (17) between diaphragm (1) and piston(5) are trapped and compressed. The compressed gas ruptures the first

* diaphragm (1), blows through the sample chamber (3), and then ruptures the* second diaphragm (2). The powdered sample stored in chamber (3) is carried by

the compressed gas into the shock tube where it is turbulently mixed into thetest gas. Photographs obtained using a high speed framing camera showed that

1E.T7. Woodbur"n, R.C. Everson and A.R.M. Kir'k, "T2hermal Decompoition andHydrogenation of Coal Duet in a Shock &lbe," Fu.el, Vol. 5, p. 38, 1974.

5

the powder (<37 u n) was dispersed and uniformly distributed in less than two-thirds ms after initiation of firing pulse. The distribution remained fairlyuniform for approximately seven ins. Diaphragms (1) and (2) are selected frommaterials appropriate for the pressures involved, i.e., aluminum foil, mylarsheet, etc. The diaphragms may be held in place by adhesives at low shocktube pressures, or by "0" rings at higher pressures.

P -"

III. CONCLUSION

This device was used to examine dusty gases composed of stoichiometricH /0 mixtures containing K2 S04 and 4O 3 respectively. The information thuso"tained has been reported elsewhere. This invention provided a reliable,

* ->- operationally simple means of producing dusty gases at the end wall of a shock* - tube prior to arrival of the incident shock wave.

Details of Sketch:

(1) First diaphragm

(2) Second diaphragm (flush with end wall)

(3) Sample chamber

(4) First edge of sample chamber

(5) Lexan piston deformable, 0.3775 inches OD in our application

(6) Electric primer M52A3B1

(7) Brass contact to conduct firing pulse into primer

, (8) Brass plate machined to receive primer and to complete circuit for thefiring pulse

(9a,9b) Phenolic backing plates to support and insulate brass contact (7)

(10) Steel supporting plate

(11) Steel assembly screws

(12) Vent port (6 mm diameter)

(13) Threaded plug containing sample chamber (3) with flat surfaces for-" supporting diaphragms (1,2)

(14) Main body of mechanism machined from iron or brass stock

2 A. Cohen ad L. Decker, "Chemical Mchanism fo' Secondary nahSUppreseion," Eighteenth Sjmpoeiv (International) on Combustion, p. 225,1981.

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(15) Portion of main body (14) threaded to mate with plug (13)

(16) Portion of main body ( 14) threaded to mate with end wall of shocktube (not shown)

(17) Smooth bored cylinder 0.3780 inches ID in main body (14) through

which piston (5) is driven

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