AD-A261 009

The Burning Rate Behavior ofPure Nitrocellulose Propellant Samples

Frederick W. RobbinsTheresa Keys

ARL-TR-82 March 1993

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4.TITLE AND SUBTITLE S. FUNDING NUMBERS

MWe Burnig Rate Behavilor of Pure Nitrocellulose Propellant Samples ~1121A8

6. AUTHOR(S)

Freduic W. Robbins; and Theresa Keys

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) S. PERFORMING ORGANIZATIONREPORT NUMBER

9. SPONSORING/ MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/ MONITORINGAGENCY REPORT NUMBER

U.S. Army Research LaboratoryATITN: AMSRL-OP-CI-B (Tech Lib) ARL.-TR-82Aberdeen Ptoving Ground, MD 21005-506

11. SUPPLEMENTARY NOTES

I 2a. DISTRIBUTION/ AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

Approved for public release, distribution is unlimnited

13. ABSTRACT (Maximum 200 words)

Closed bomb firings have been conducted to detemine the burnig not behavio of pure nitrocellulose (NC) gunpropellants. Samples producd and tested included nitration levels of 12.02.12.65,13.11%, in both zero, and seven-perforated cylindrical geomnetries. A sample containing basic lead carbonate was als included. Burning rate derivedfrom the closed bomnb tests were compared to strandl burner data measured on samples extruded from the sane NCbalches. The burning rate plots for the pure NC samples show the characteritic slope changes of propellants withadditives.

14. SUBJECT TERMS 15. NUMBER OF PAGES32

intero ballistics; closed bomb tests. sgrand turne test&rssure 16. PRICE CODE

17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACTOF REPORT OF THIS PAGE OF ABSTRACT

UNCILA-SSUIFI UNCLASSIFED UNCLASSIFID ULNSN 7540-01-280-5500 Standard Form 29" (Rev. 2-69)

Prescribed by ASISI Sid W189I

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ACKNOWLEDGMENTS

The authors wish to thank T. C. Smith, S. E. Mitchell, and C. G. Irish for their helpful discussions

and suggestions. (Note: The U.S. Army Ballistic Research Laboratory was deactivated on 30 September

1992 and subsequently became part of the U.S. Army Research Laboratory (ARL) on 1 October 1992.)

Accesion For

NTIS CRA&MDTIC TABUnannounced 0Justification ... ...... ...............

By ................ .....Distribution!

Availability CodesAvail and I or

Dist Special

Ill..o

-4.- INTE~NTONALLY LE~r BLANK.

iv

TABLE OF CONTENTS

Page

ACKNOWLEDGMENTS .......................................... iii

LIST OF FIGURES .............................................. vii

LIST OF TABLES ............................................... vii

1. INTRODUCTION ............................................... 1

2. EXPERIMENTAL APPROACH ..................................... 1

3. RESULTS ..................................................... 4

3.1 Burning Rate as a Function of NC Nitrogen Content ..................... 93.2 Comparison of Zero- and Seven-Perforation Grain Burning Rates ............ 133.3 Strand Burner Data ............................................ 16

4. CONCLUSIONS AND RECOMMENDATIONS .......................... 18

5. REFERENCES .................................................. 21

DISTRIBUTION LIST ............................................ 23

V

INTUNTONALLY LEFr BLANK.

LIST OF FIGURES

Figure Page

1. Comparison of Burning Rates Determined by CIBOM and FRBOM (12.65%Nitrocellulose and 0.85% Basic Lead Carbonate; Seven-Perforation) ............ 4

2. Shot-to-Shot Variations in Burning Rate Curves (12.65% Nitrocellulose;Zero-Perforation) .............................................. 9

3. Bum Rate Curves for Zero- and Seven-Perforation Grains .................... 10

3a. Bum Rate Curves for Grains With Zero Perforations and Various NitrogenLevels ...................................................... 10

3b. Bum Rate Curves for Grains With Seven Perforations and Various NitrogenLevels ...................................................... I I

3c. Bum Rate Curves for Grains With Seven and Zero Perforations and12.02% Nitrogen ............................................... 11

3d. Bum Rate Curves for Grains With Seven and Zero Perforations and12.65% Nitrogen ..... ......................................... 12

3e. Bum Rate Curves for Grains With Seven and Zero Perforations and13.11% Nitrogen ............................................... 12

4. Bum Rate Coefficient vs. Flame Temperature (for a Burning Rate Exponentof 0.8) ...................................................... 15

5. Comparison of Bum Rates of Strands and Zero-Perforation Grains .............. 18

6. NOVA Code Simulations of 5-in. 54-Caliber Pressure-Time and PressureDifference Curves .............................................. 19

LIST OF TABLES

Table Page

I. Values for Experimental Propellant Samples ............................. 3

2. Firing Data .................................................... 5

3. Rationalized Burning Rate Coefficients ................................. 14

4. Strand Burning Test Data .......................................... 17

vii

IffNTUMONALLY LEFr BLANK.

viii

1. INTRODUCTION

In performing any gun interior ballistic calculations, the burning rate or the rate of regression of the

burning propellant is one of the most significant input parameters (Haukland and Burnett 1972). The

burning rate is used in interior ballistics computer codes with the propellant density and the geometry of

the propellant grains to compute the mass generation rate. The mass generation rate is integrated to

determine the instantaneous mass of propellant burned. Using an equation of state to calculate the average

pressure in the gun chamber and a pressure gradient equation, the projectile base pressure is calculated.

With the projectile base pressure known, the acceleration, velocity, and travel of the projectile can be

determined.

The closed bomb, which is most frequently used to generate experimental burning rate data for gun

propellants, is a closed vessel in which propellant is burned and the resulting pressure is monitored as a

function of time. Theoretically, the burning rate at all pressures, up to the maximum pressure attained in

the bomb, can be determined. Propellants have, in general, a monotomically increasing burning rate as

a function of pressure. When the logarithms of the burning rates are plotted vs. the logarithms of the

pressures, one obtains straight-line segments which frequently have distinctly different slopes. This

behavior is difficult to explain with either flamespread or variable thermodynamics.

The work described in this report was conducted to establish a database for propellant grains

containing only nitrocellulose (plus the residual solvents necessarily remaining from the processing). It

was also hoped to determine if the additives frequently used in gun propellants, such as basic lead

carbonate, diphenyl amine, or potassium sulfate, caused or affected the changes in the slopes of the

burning rate curves. The work was planned to include various nitrogen levels of nitrocellulose (NC)

without any additives and at least one sample with basic lead carbonate for comparison. Both closed

bomb and strand burning rate tests were included in the test program. Production, tests, and analysis were

performed at the Naval Ordnance Station, Indian Head, MD, between 1979 and 1981.

2. EXPERIMENTAL APPROACH

The three NC nitrogen levels selected for evaluation were those most frequently used in conventional

gun propellants, nominally, 12.0, 12.6, and 13.15%. The actual levels of the NC used for the propellant

samples were 12.02, 12.65, and 13.11%. Two grain configurations. zero- and seven-perforation right

circular cylinders, were selected for the closed bomb testing, and solid strands were used for the strand

burning rate tests. In addition to the "pure" NC samples, an additional 12.65% nitrogen sample was made

with 0.85% of basic lead carbonate, which was processed in the seven-perforation right circular cylinder

granulation.

The propellant samples were manufactured using the conventional processing techniques of mixing

with solvent in a horizontal, sigma-blade mixer, extrusion, and cutting to length. All samples for each

nitrogen level were processed using the same batch of NC and the same ratios and levels of solvents; the

solvent levels did vary from one nitrogen level to another. The grains and strands were dried very slowly

in order to minimize shrinkage, maximize straightness, and produce a relatively nonporous, smooth surface

texture.

The zero-perforation grains were extruded to a nominal 0.318 cm diameter and cut to a length of

0.64 cm; the seven-perforation grains had nominal dimensions of 0.64 cm in diameter and 1.3 cm in

length, and had perforations diametr. of 0.038 cm. The strands were nominally 0.64 cm in diameter.

The actual grain dimensions and residual solvent levels are given in Table 1. It should be noted that the

12.02% nitrogen level samples were not as smooth as the samples of the two other nitrogen levels and

had some uncolloided NC dispersed throughout the grains. It is felt that the surface area definition for

solvent-processed extruded grains, because of shrinkage and rough surfaces, is not as correct as for

solventless extruded propellant grains, but burning rate trends can probably be captured.

The thermodynamic properties of the propellants used ir the data reduction for the closed bomb tests

were calculated with the Blake code (Freedman 1974) (Table 1). Values for the 0.25 g/cm 3 loading

density were chosen. No variable thermodynamic properties were used in the calculations.

The igniter system for the closed bomb tests consisted of an MlOO match boosted with 1.1 g of

Dupont 700x. A series of five shots was conducted for each grain type in the 182.4-cm 3 closed bomb at

ambient temperature. The first two firings were at reduced charge weights to determine a charge weight

which will give a nominal peak pressure of 310 MPa. The pressure data were digitized at 25-ps intervals

and stored on magnetic tape. Burning rates were then computed from the pressure history with two

different programs. The first, CIBOM (Wynne 1976), is a program which computes the time rate of

change of mass burned (dm/dt) from the time rate of change of pressure (dP/dt). Using least squares,

dP/dt is obtained by fitting the pressure data to a cubic polynomial and evaluating the differentiated

2

ac , V%

L U N M. @I..soo

5 r- r- s 4

-fzi%n %. %DID

polynomial. The second, FRBOM (Robbins and Horst 1976), computes dn/dt by calculating the mass

at a pressure and the mass at some higher pressure and equating dm/dt to the change in the calculated

mass burned in an integral number of sample time intervals (•xnAt). Both programs fit, by a least squares

analysis, the bum rate-pressure data to a power law in specified pressure ranges.

The strand burner tests were conducted at ten pressures, ranging from 3.5 to 55.2 MPa. Testing was

limited by the capability of the existing strand burner facility to a maximum pressure of 55.2 MPa. An

average of three or four shots at each pressure was used to determine the burning rate.

3. RESULTS

The burning rate descriptions, coefficient and exponent, for straight-line segments are given in Table 2.

Burning rates calculated with CIBOM and FRBOM differ by approximately 0.5%. The plots cannot be

distinguished from each other when overlaid, except that one is smoother because of smoothing techniques

intrinsic to the separate programs (Figure 1). The difference in tail-off is caused by different slivering

routines of the programs.

200-CIBOM

FRBOM

100-

50-E

S40-

S30-

m 20-

10-

55 10 20 30 40 50 100 200 300 400

Pressure (MPa)

Note: (12.65% Nit'ocellulose and 0.85% Basic Lead Carbonate; Seven-Perforation)

Figure 1. Comparison of Burning Rates Determined by CIBOM and FRBOM.

4

0l C4__ n_ m_ %0_____v

0,'0

u to W 0 m N t IToc'r- w %

0 00 0 '~ e C4-nencc 0% % o a n Q M

0 *

-ne - en0

.Iz U

-- 9 f -- cRT Sr-

C-4 r- N r- 0grýC0ý t- '0fi -N. %n " l"%n"% 4 nN

-u e'a cc C1 1 %

C1 4 C14 C1 - r

in n % %nv5

0 m__ _ _ _%0_ _en__ _ _ _C

U,~c v~-O cy, in I0OOV

a) tn 0 % 4O 00 0 k -0cc-e

0

Ix _ _ _ _

c) e en"

a 0 In CO > cc Mcce"M2jCIn

qn a)Mr ýr %r-M - r cr, - r

ra -l C4 w% C4 IT C~4 INI

a) - i-orE wl.t5~

wl i % n n k

_ý wl 00 0 l m'i e l 0 l ' l 0in~ in kn 9 n0n i

en WE0 co% % DCt 0 4C MC4

cl rý -) %Rt% nr-v%

0I

%a %n 00 V A 40'O.0

o 00000 OC4 ( 0.% ~ ~ o -rO-o tnU~o e-%o An ~C 5 u

%n cc %n- P , A8r00o0

14ý Mr- 00 o00r% 0 00 CC-!

in r- oo oc40

tto

kn~ in %M 4n % n n %

I-w l wl % n %n % n %

tu

00 V) C T00t0w M 0

~00OO%~~O00~ %0 O 0

0n M_%_%0_§G _M_

6 ~00

ba

en e t-e

I":

6en

The variation from shot to shot (Figure 2) was determined to be approximately 1% at the higher

pressure range (207 MPa) and 2% at the lower pressure range (28 MPa) as calculated from values of the

coefficient (a) and exponent (n) in Table 2.

200-

100-

S50 -E140-

30 -C

m20

10-

5 10 20 30 40 50 100 200 300 400

Pressure IMPa)

Note: (12.65% Nitrogen; Zero-Perforaion)

Figure 2. Shot-to-Shot Variations in Burning Rate Curves.

3.1 Burning Rate as a Function of NC Nitrogen Content. A composite of representative burning rate

curves for the zero- and seven-perforation grains for the three nitrogen levels are given in Figure 3. Select

comparisons are given in Figures 3a-e. As would be expected, for both grain geometries, the burning

rates are higher for the higher nitrogen level grains. The curves on each figure appear parallel, though

the high-pressure portions of the 12.02% NC curves have a slightly larger burning rate exponent than the

higher nitrogen NC curves (0.89-0.83 for the zero-perforation and 0.84-0.64 for the seven-perforation

grains).

It is evident that the curves of all three nitrogen levels have slope breaks (Figures 3a and 3b) and at

least three separate sections. Further, for each grain geometry the slope breaks occur in nearly the same

9

Zero-perforation Seven-perforation

S...... 12.02% Nitration -- - -... 12.02% Nitration

12.65% Nitration ....- 12.65% Nitration

13.11% Nitration 13.11% Nitration

200-

100-

50-E

30-

S20 0

10- 1,7 E.--"

5 ..j " I I I ! III I

5 10 20 30 40 50 100 200 300 400

Pressure (MPa)

Figure 3. Bum Rate Curves for Zero- and Seven-Perforation Grains With Different NitrogenLevels.

200-

2 13.116% Nitrogen

100- 12.65% Nitrogen . "

. 12.02% NitrogenE

E

Sp

co.o

10- .

5-5 10 100 400

Pressure (MPa)

Figure 3a. Bum Rate Curves for Grains With Zero Perforations and Various Nitrogen Levels.

10

200

13.11% Nitrogen100-

1-0-i12.65% Nitrogen

E 12.02% Nitrogen

CDv 0 , ........

° ..

10-

5-5 10 100 400

Pressure (MPa)

Figure 3b. Burn Rate Curves for Grains With Seven Perforations and Various Nitromen Levels.

200-

- - 7 Perf100-

- 0 PernEE

C

10•

5I5 10 100 400

Pressure (MPa)

Figure 3c. Bum Rate Curves for Grains With Seven and Zero Perforations and 12.02% Nitrogen.

11

200S- -7 Per/ f'

100

E

107

5

5-' I '.' ", . I

5 10 100 400Pressure (MPa)

Figure 3d. Bum Rate Curves for Grains With Seven and Zero Perforations and 12.65% Nitrogen.

200

100- - 7 Per/

100

5 10 100 400

Pressure (MPa)

Figure 3e. Bum Rate Curves for Grains With Seven and Zero Perforations and !13.1!1!% Nitrogen.

12

pressure range for all nitrogen levels. For the zero-perforation grains, the first major break occurs around

20 MPa and the second major break occurs at 35 to 50 MPa with some suggestion that the second one

occurs at the lower end of the range for the higher nitrogen levels. For the seven-perforation grains, the

breaks are at 21 to 28 MPa and at 34 to 70 MPa. However, the break in the 12.02% nitrogen level tends

to be much higher for the seven-perforation grains (up to 90 MPa) than for the zero-perforation grains (up

to 48 MPa).

The humps at high pressure for the seven-perforation grains are caused by smoothing through the

pressure-time curve at slivering with a cubic polynomial. Even though the program (FRBOM) has an

exact solution for the surface function routine, the cubic equation cannot adjust itself well enough to

compensate for the discontinuous dp/dt at that point.

The parallelism of the different segments of the burning rate vs. pressure curve would suggest that

rationalization of the burning rates, as proposed by Irish (1979) and supported by data of Riefler (Riefler

and Lowery 1974) and Grollman (Grollman and Nelson 1977) is a viable technique which should allow

easy ranking of propellants with respect to their burning rates. In Table 3, three exponents have been

chosen and the corresponding coefficients have been calculated for the seven-perforation propellant. The

ranking according to nitrogen level is evident with a higher coefficient for higher nitrogen levels. In

Figure 4, the coefficients for the three nitrogen levels and the two grain geometries, assuming a burning

rate exponent of 0.8, are plotted vs. adiabatic flame temperature (which is proportional to nitrogen level

with minor perturbations due to volatile levels). This figure shows the usefulness of having one number

to characterize a whole section of a burning rate curve.

3.2 Comparison of Zero- and Seven-Perforation Grain Burning Rates. The burning rate data for zero-

and seven-perforation grains are compared for the three nitrogen levels in Figures 3c-e. All seven-

perforation burning rates above 21 MPa are higher than those of the corresponding zero-perforation grains

of the same nitrogen level, but the rates merge at about 210 MPa just before slivering occurs. This would

suggest that, since the volatile levels did not vary greatly for each nitrogen level and there was no pattern

of difference in volatile levels in the two grain geometries, the elevation of the burning rate for the

seven-perforation grains is a function of the perforations.

If the apparent burning rate augmentation is a function of the perforations, a higher mass generation

rate inside the perforations is suggested as the cause. This, in turn, suggests a higher pressure inside the

13

II=

C - -m r- N ;C7

C. en 0

cc t- -- r-q~ ena c n(

sq q IQ

I 00

14

( Zero-perforation cylinder (% nitration)

E) Seven-perforation cylinder (% nitrtion)

A Average of zero- and seven-ietforation1

40 Seven-perforation cylinder with 0.85% lead carbonate (% nitration).---. a "2.25 X 10-4 (Tf - 1800) n-g4A mm/(s - Mpan)]2

2.6-

2.4 .13.11Seven-perf oration

Co.o 2.2-

S-P 13.11E 2.0-

Cq

1.8- 12.65

Zero.perforation

S1.6--0

a * Q12.65

C5

CoS1.

12.02

1.2 L20

1.0 I I ! I I2400 2500 2600 2700 2800 2900 3000 3100

Flame temperature (K)

1 Burning averaged using NN * N2

From Grollmen and Nelson.

Note: For a Burning Raze Exponent of 0.8.

Figure 4. Buminn Rate Coefficient vs. Flame Temperature.

15

perforations or an increase in the surface area by expansion or splitting. (There is evidence, however, that

grains do not split [Naval Ordnance Station 1979a, 1979b; Robbins and Bingham 1981 ].) This hypothesis

should be studied with a computer model to determine what pressure differential must be maintained in

that pressure regime to cause the apparent enhancement in burning rate.

This geometry effect was not noted in a similar study with NOSOL, an easily ignited double-base

propellant (Mitchell and Horst 1976). The data reduction technique and closed bomb collection procedure

for the NOSOL and pure NC samples were the same, but the NOSOL perforations were two to three times

larger than those of the pure NC samples.

3.3 Strand Burner Data. The strand burning data are given in Table 4 and plotted in Figure 5. The

corresponding zero-perforation grain closed bomb burning rates are provided in Figure 5. The strand data

have not been corrected for their total volatile content. Corrected data would be slightly higher on the

graphs since all solvent levels are higher for the strands than for the grains. Notwithstanding uncorrected

strand data, it is considered noteworthy that the strand data exhibit the same trends with respect to nitrogen

content (including characteristic slope breaks) as the closed bomb data.

TT,.L strand burning rate data at low pressures are lower than that extrapolated from closed bomb data

using mid-pressure ranges. The technique of extrapolation closed bomb data from mid-pressure range to

low pressures is often the procedure used in determining the burning rate input for two-phase flow interior

ballistics codes such as NOVA (Gough 1977) where flamespread is modeled. It has been assumed that

the first high slope section between 5 and 20 MPa is a combination of flamespread and the intrinsic

burning rate of the propellant and, therefore, should not be used in a flamespread model. The low

pressure burning rate data obtained from the strand burner tests suggest that extrapolation of closed bomb

data to low pressures may, however, involve incorrect assumptions about the influence of flamespread.

Simulations of the 5-inch, 54-caliber gun system were made with the NOVA code to illustrate the effect

of the low-pressure burning rate data. Two computations were made with only one difference: one

extrapolated the closed bomb mid-pressure burning rate data to low pressures (as has been done

traditionally) and the other used the low-pressure burning rate data from the closed bomb. The resulting

pressure-time curves for two gauge locations (case base and case mouth) and the associated pressure

difference (AP) curve are compared in Figure 6. The use of the actual low pressure data has the effect

of reducing the magnitude of the calculated pressure difference and causing a longer ignition delay.

16

Table 4. Strand Burning Test Data

Pressure Burning rates at 250 C Average burning rates(MPa) (crn/s) (cm/s)

Mix 619; 12.02% Nitrogen NC

3.45 0.292, 0.358, 0.300 0.3186.89 0.569, 0.569, 0.589 0.577

10.34 , 0.759, a 0.826 0.79213.79 0.925, 0.927, 1.036, 1.156 1.01120.68 1.400, a, 1.435, 1.278 1.37227.58 1.748, 1.524, 1.692, 1.699 1.66634.47 2.670, 2.261, 2A79, 2.583 2.49941.37 2.101, 2.182, 1.986, 2.139 2.10348.26 2.642, 2.250, 2.291, 2.162 2.33755.16 2.344, 3.078, 3.124, 2.731 2.819

Mix 618; 12.65% Nitrogen Nr

3.45 0.310, 0.315, 0.315 0.3126.89 0.640, 0.612, 0.617 0.622

10.34 0.866, 0.848, 0.907 0.87213.79 1.100, 1.107, 1.107 1.10520.68 1.565, 1.600, 1.575 1.58027.58 1.872, 1.887, 1.902 1.88734.47 2.146, 2.159, 2.106 2.13641.37 2.377, 2.334, 2.375 2.36248.26 2.670, 2.647, 2.662 2.65955.16 3.005, 3.028, 3.094 3.043

Mix 599; 13.11% Nitrogen NC

3.45 0.427, 0.439, 0.409, 0.417 0.4246.89 0.813, 0.836, 0.846 0.831

10.34 1.128, 1.135, 1.133 1.13313.79 1.461, 1.461, 1.473 1.46620.68 1.925, 2.007, 1.979 1.97127.58 2.405, 2.492, 2.423 2.44134.47 2.835, 3.272, 2.880 2.99541.37 3.213, 3.368, 3.203 3.26148.26 4.115, 4.158, 4.069 4.11555.16 4.234, 4.216, 4.257 4.237

a Test strand flashed.

17

IHTR 698

Zero-perforation grains Strands-* ... ,12.02% Nitration 0 12.02% Nitration

12.65% Nitration O 12.85% Nitration

13.11% Nitration A 13.11% Nitration

200

100 . .10,

40 A040 ..O

0-

aA

"- 30,...

,o_

10-

A

5 I I I I I I5 10 20 30 40 50 100 200 300 400

Prmure (MPa)

Figure 5. Comparison of Burning Rates of Strands and Zero-Perforation Grains.

4. CONCLUSIONS AND RECOMMENDATIONS

The following conclusions resulted from the study:

(1) A database of bum rate equations has been presented for pure NC grains for three nitration levels

and for NC with a basic lead carbonate additive for a 12.65% nitrogen level.

(2) The burning rate plots for pure NC show the characteristic slope changes of propellants with

additives.

(3) The data suggest an enhanced burning rate associated with the presence of perforations in the

grain.

18

Pressure-Time for Two Points

400.

- Extrapolated value below 27.6 MPaExtrapolated value below 27.6 MPActual value below 27.6 MPa

300 - Actual value below 27.5 MPS

* 1!

200

- I-CI.

0L L

0 4 8 12 16 20Time (ms)

Pressure Difference100

SExtrapolated values below 27.6 MPa

75r Actual values below 27.6 MPS

254/ I It. i I• I.,"

S25 ,"* I ,;' i iA*. , I ,I t,

-25- a

-so

-75.

0 4 8 12 16 20Time (ms)

Figure 6. Nova Code Simulations of 5-inch, 54-Caliber Pressure-Time and Pressure Difference

Curves.

19

(4) Two data reduction computer programs were run on the same data with no significant difference

noted in calculated bum rates between the programs.

(5) The low-pressure strand burning rate data agree with the low-pressure closed bomb burning rate

data and suggest that the low-pressure section of the closed bomb burning rate curve is significant.

(6) The maximum difference in calculated burning rates from one closed bomb firing to another of

the same propellant at the same loading density was in the order of 2%.

The following recommendations are offered:

(1) In a continuation of the study, high-pressure strand burning data should be obtained and the

effects of solvent level should be studied.

(2) The use of measured low pressure bum rate data is recommended to provide improved simulation

of the flamespread event with two phase flow interior ballistic codes.

20

5. REFERENCES

Freedman, E. "A Brief Users Guide for the BLAKE Program." BRL-IMR-249, U.S. Army BallisticResearch Laboratory, Aberdeen Proving Ground, MD, July 1974.

Gough, P. S. "Numerical Analysis of a Two-Phase Flow With Explicit Internal Boundaries." IHCR 77-5,Paul Gough Associates, Inc., Portsmouth, NH, I April 1977.

Grollman, B. B., and C. W. Nelson. "Burning Rates of Standard Army Propellants in Strand Burner andClosed Chamber Tests." BRL-MR-2775, U.S. Army Ballistic Research Laboratory, Aberdeen ProvingGround, MD, August 1977.

Haukland, A. C., and W. M. Burnett. "Sensitivity of Interior Ballistic Performance to PropellantThermochemical Parameters." Proceedings of the Tri-Service Gun Propellant Symposium, vol. 1,par. 7.3-1, Picatinny Arsenal, Dover, NJ, 11-13 October 1972.

Irish, C. G., Jr. "An Attempt to Rationalize NACO Propellant Burning Rate Descriptions." Proceedingsof the 16th JANNAF Combustion Meeting, Monterey, CA, CPIA Publication 308, vol. 1,pp. 399-415, December 1979.

Mitchell, S. E., and A. W. Horst. "Comparative Burning Rate Study." Proceedings of the 13th JANNAFCombustion Meeting, Monterey, CA, CPIA Publication 308, vol. 1, pp. 383-404, September 1976.

Naval Ordnance Station. Technology Ouarterly, Gun Ammunition Propulsion, July-September 1979,Indian Head, MD, pp. 29-30, 28 February 1979a.

Naval Ordnance Station. Technology Ouarterly. Gun Ammunition Propulsion. July-September 1979,Indian Head, MD, pp. 3-4, 31 August 1979b.

Riefler, D. W., and D. S. Lowery. "Linear Bum Rates of Ball Propellants Based on Closed BombFirings." BRL Contract Report No. 172, U.S. Army Ballistic Research Laboratory, Aberdeen ProvingGround, MD, August 1974.

Robbins, F. W., and R. P. Bingham. "A Study of the Burning Characteristics of Multiperforated GunPropellant Grains." IHTR 697, U.S. Army Ballistic Research Laboratory, Aberdeen Proving Ground,MD, 10 March 1981.

Robbins, F. W., and A. W. Horst. "Numerical Simulation of Closed Bomb Performance Based on BLAKECode Thermodynamic Data." IHMR 76-295, U.S. Army Ballistic Research Laboratory, AberdeenProving Ground, MD, 29 November 1976.

Wynne, G. J. "Y Bomb--A Computer Program for the Collection, Storage, and Processing of Pressure-Time Data From Propellant Burned in a Closed Bomb." IHTR, April 1976.

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