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Accelerated hypergolic ignition with lowering of temperature
372
COMBUSTION AND FLAME
97:372-374 (1994)
Accelerated Hypergolic Ignition with Lowering of Temperature S. P. PANDA, S. G. KULKARNI, and C. PRABHAKARAN Faculty of Explosives and Applied Chemistry, Institute of Arrnament Technology, Girinagar, Pune 411025, India
Hypergolic liquid fuels known to undergo cationic polymerizationat the preignition stage with red fuming nitric acid (RFNA) as oxidizerhave been found to exhibit synergistichypergolicignitionat zero and subzero temperatures. This accelerated ignitionwith loweringof temperature has been ascribed to negativeactivation energy usually associated with most cationic polymerizationsystems. The best ignition was obtained with blends of fuels consisting of norbornadiene and furfuryl alcohol which underwent strong cationic polymerizationwith protonic acids and possiblyDiels-Alderaddition to each other.
INTRODUCTION Using R F N A as oxidizer, Panda et al. [1-6] have reported hypergolic ignition of furfurylidene ketones, azomethines, azines, hydrazones, 3-carene, norbornadiene, and blends of norbornadiene with carene, furfuryl alcohol, and furfurylidene-acetones. In these systems cationic polymerization has been stated as one of the predominant pre-ignition reactions. Equal blends of norbornadiene and furfuryl alcohol or furfurylidene acetone showed synergistic ignition with RFNA. This was explained in terms of D i e l s - A l d e r reaction of dienes and dienophiles in addition to cationic polymerization before ignition [6]. It became of interest to measure the ignition delay of individual fuels and their equal blends with lowering of the initial temperature of the propellants using R F N A as oxidizer. Our experiments showed apparently unusual results in terms of accelerated ignition with progressive cooling.
METHODS AND MATERIALS Norbornadiene (Fluka AG, I), furfuryl alcohol (BDH, II), and 3-carene (Camphor & Allied Products, India, IV) were obtained from trade sources and were distilled before use. Furfurylideneacetone (III) was synthesized following Vogel [7]. R F N A used in the experiments was obtained from High Explosives Factory, 0010-2180/94/$7.00
Khadki, India, and contained HNO3, 75.5%; N204, 21%; H 2 0 , 2%; H3PO 4. 1% and HF, 0.5%. Ignition delay measurements (ID) were carried out using a modified Pino's ignition delay apparatus as reported by Kulkarni and Panda [8]. The fuel and oxidizer were cooled below 0°C in a refrigerator and were brought up to 0°C by keeping at room temperature before ID measurements. For similar measurements, they were cooled in a Dewar flask using liquid nitrogen up to - 15°C and brought up to -10°C in a refrigerator.
RESULTS AND DISCUSSIONS Table 1 gives the ID values in milliseconds for different neat fuels and their blends at 26°C (room temperature), 0°C, and - 1 0 ° C with R F N A as oxidizer. For fuels like norbornadiene (I) and furfuryl alcohol (II), where cationic polymerization is very strong in the presence of protonic acids [9, 10], the decrease in ID with varying temperature was significant. This was still more pronounced when the fuel molecules were blended in equal amounts. The synergy in ignition with lowering of temperature in the case of the 1:1 blend of furfuryl alcohol and norbornadiene may be due to the predominently negative overall activation energy (generally in the range of - 4 0 to + 60 k J / m o l ) for cationic polymerization [11, 12, p. 79], which may remain valid for cationic copolymerization Copyright© 1994by The CombustionInstitute Published by Elsevier Science Inc.
ACCELERATED HYPERGOLIC IGNITION
CH 2OH II
l
[~
CH=CHC -OC -H?3
III
IV
Fig. 1. Structures of fuel molecules. I: Norbornadiene. II: Furfuryl alcohol. III: Furfurylideneacetone. IV: Carene.
[12, p. 290], and additional Diels-Alder reaction between the molecules which is associated with a low positive activation energy [13, 14]. It may be highlighted that for many cationic polymerization systems a negative energy of activation for the overall rate is known to create the unusual phenomenon of increase in the rate of reaction with decrease in temperature [12, p. 80].
373 Furfurylideneacetone (III), which turns very viscous at 0°C, showed an increase in ID with RFNA at 0°C. This may be due to bad mixing of oxidizer and fuel preventing an intimate reaction. However, blended with norbornadiene, it showed a synergistic decrease in ID at 0°C, which is expected, due to faster cationic polymerization and a relatively slower but additional Diels-Alder reaction at the preignition stage. 3-Carene (IV) undergoes cationic polymerization with protonic acids (15). However, with decrease of temperature, the ID of carene with RFNA showed an increase and it turned nonhypergolic at 0°C (Table 1). This may be due to a possible positive activation energy for carene polymerization system. Blended with norbornadiene in equal amounts, carene failed to show any decrease in ID with RFNA when the initial temperature of the propellant was lowered. This may be explained in terms of the low activation energy ( - 2 0 to + 41 KJ/mol) generally associated with most carbonium ion polymerization where the polymerization rates do not increase rapidly with lowering of temperature [16].
TABLE 1 Ignition Delay of Norbornadiene and Its Equal Blends with Furfuryl Alcohol, Furfurylideneacetone and Carenc at Different T e m p e r a t u r e s with R F N A as Oxidizer. O = oxidizer; F = fuel Srl No.
F u e l / F u e l blend
1.
Norbornadiene(I)
2.
Furfuryl alcohol(II)
3.
Norbornadiene, I - furfuryl alcohol(II)
4.
Furfurylideneacetone(IIl)
5.
Norbornadiene(I)-Furfurylideneacetone(llI) Carene(IV)
Temperature °C
-
-
-
6. 7.
Norbornadiene(I)-Carene(IV) -
26 0 10 26 0 10 26 0 10 26 0 26 0 26 0 26 0 10
O / F by Volume (optimum)
Average ignition delay, ms
Standard deviation ms
2.0 2.0 2.0 2.0 2.0 2.0 2.4 2.4 2.4 2.0 2.0 2.4 2.4 3.5 -2.4 2.4 2.4
44 37.6 28.2 109.0 98.0 86.2 16.6 15.2 13.5 23.0 34.5 22.2 19.4 377.0 Non-hypergolic 55.0 59.3 61.0
0.57 0.5 0.5 4.1 4.0 4.0 0.5 0.6 0.6 0.5 0.8 0.4 0.5 8.3 -0.8 0.9 1.2
374
The authors thank Rear Admiral Ajay Sharma, A VSM, Director and Dean, IA T for permitting the publication of the paper. REFERENCES 1. Panda, S. P., and Kulkarni, S. G., Combu~t. Flame 28:25-31 (1977). 2. Panda, S. P., and Kulkarni, S. G., Def. Sci. J 27(2):77-80 (1977). 3. Panda, S. P., and Kulkarni, S. G., Combust. Flame 53:93-98 (1978). 4. Panda, S. P., and Kuikarni, S. G., J. Armt. Studies 11(2):138-139 (1976). 5. Kulkarni, S. G., and Panda, S. P., Combust. Flame 56:241-244 (1984). 6. Panda, S. P., Kulkarni, S. G., and Prabhakaran, C., Combust. Flame 76:107-110 (1989). 7. Furniss, B. S., Hannaford, A. J., Rogers, V., Smith, P. W. C. and Tatchell, A. R., Vogels Textbook of Practical Organic Chemistry, ELBS, Longman Group, London, 1978, p. 795. 8. Kulkarni, S. G., and Panda, S. P., Combust. Flame 40:29-36 (1981).
S . P . PANDA ET AL. 9. Kennedy, J. P., Cationic Polymerization of Olefins--A Critical Inventory, Wiley Interscience, New York, 1975, p. 223. 10. Siegfried, K. J., Furan Polymer, Cited in Encyclopedia of Polymer Science and Technology, (H. Mark and N. G. Gaylord, Eds., Wiley, New York, 1967, Vol. 7, pp. 435-437. 11. J. M. G. Cowie, Polymers: Chemistry and Physics of Modem Material, International Textbook Company, Aylesbury, 1973, p. 77. 12. Sawada, H., Thermodynamics of Polymerization, Marcel Dekker, New York, 1976. 13. Norman, R. O. C., Principles of Organic Synthesis, 2nd ed., Chapman & Hall, London, 1981, p. 291. 14. Fleming, I., Frontier Orbitals and Organic Chemical Reactions, Wiley, London, 1982, p. 22. 15. Panda, S. P., and Kulkarni, S. G., J. Polym. Sci. (Polymer Letters Edition) 21:649-656 (1983). 16. Eastham, A. M., Cationic Polymerization, cited in Encyclopedia of Polymer Science and Technology (H. Mark and N. G. Gaylord, Eds.), Wiley, New York, 1965, Voi. 3, p. 53.
Received 25 May 1993; revised 8 November 1993
COMBUSTION AND FLAME
97:372-374 (1994)
Accelerated Hypergolic Ignition with Lowering of Temperature S. P. PANDA, S. G. KULKARNI, and C. PRABHAKARAN Faculty of Explosives and Applied Chemistry, Institute of Arrnament Technology, Girinagar, Pune 411025, India
Hypergolic liquid fuels known to undergo cationic polymerizationat the preignition stage with red fuming nitric acid (RFNA) as oxidizerhave been found to exhibit synergistichypergolicignitionat zero and subzero temperatures. This accelerated ignitionwith loweringof temperature has been ascribed to negativeactivation energy usually associated with most cationic polymerizationsystems. The best ignition was obtained with blends of fuels consisting of norbornadiene and furfuryl alcohol which underwent strong cationic polymerizationwith protonic acids and possiblyDiels-Alderaddition to each other.
INTRODUCTION Using R F N A as oxidizer, Panda et al. [1-6] have reported hypergolic ignition of furfurylidene ketones, azomethines, azines, hydrazones, 3-carene, norbornadiene, and blends of norbornadiene with carene, furfuryl alcohol, and furfurylidene-acetones. In these systems cationic polymerization has been stated as one of the predominant pre-ignition reactions. Equal blends of norbornadiene and furfuryl alcohol or furfurylidene acetone showed synergistic ignition with RFNA. This was explained in terms of D i e l s - A l d e r reaction of dienes and dienophiles in addition to cationic polymerization before ignition [6]. It became of interest to measure the ignition delay of individual fuels and their equal blends with lowering of the initial temperature of the propellants using R F N A as oxidizer. Our experiments showed apparently unusual results in terms of accelerated ignition with progressive cooling.
METHODS AND MATERIALS Norbornadiene (Fluka AG, I), furfuryl alcohol (BDH, II), and 3-carene (Camphor & Allied Products, India, IV) were obtained from trade sources and were distilled before use. Furfurylideneacetone (III) was synthesized following Vogel [7]. R F N A used in the experiments was obtained from High Explosives Factory, 0010-2180/94/$7.00
Khadki, India, and contained HNO3, 75.5%; N204, 21%; H 2 0 , 2%; H3PO 4. 1% and HF, 0.5%. Ignition delay measurements (ID) were carried out using a modified Pino's ignition delay apparatus as reported by Kulkarni and Panda [8]. The fuel and oxidizer were cooled below 0°C in a refrigerator and were brought up to 0°C by keeping at room temperature before ID measurements. For similar measurements, they were cooled in a Dewar flask using liquid nitrogen up to - 15°C and brought up to -10°C in a refrigerator.
RESULTS AND DISCUSSIONS Table 1 gives the ID values in milliseconds for different neat fuels and their blends at 26°C (room temperature), 0°C, and - 1 0 ° C with R F N A as oxidizer. For fuels like norbornadiene (I) and furfuryl alcohol (II), where cationic polymerization is very strong in the presence of protonic acids [9, 10], the decrease in ID with varying temperature was significant. This was still more pronounced when the fuel molecules were blended in equal amounts. The synergy in ignition with lowering of temperature in the case of the 1:1 blend of furfuryl alcohol and norbornadiene may be due to the predominently negative overall activation energy (generally in the range of - 4 0 to + 60 k J / m o l ) for cationic polymerization [11, 12, p. 79], which may remain valid for cationic copolymerization Copyright© 1994by The CombustionInstitute Published by Elsevier Science Inc.
ACCELERATED HYPERGOLIC IGNITION
CH 2OH II
l
[~
CH=CHC -OC -H?3
III
IV
Fig. 1. Structures of fuel molecules. I: Norbornadiene. II: Furfuryl alcohol. III: Furfurylideneacetone. IV: Carene.
[12, p. 290], and additional Diels-Alder reaction between the molecules which is associated with a low positive activation energy [13, 14]. It may be highlighted that for many cationic polymerization systems a negative energy of activation for the overall rate is known to create the unusual phenomenon of increase in the rate of reaction with decrease in temperature [12, p. 80].
373 Furfurylideneacetone (III), which turns very viscous at 0°C, showed an increase in ID with RFNA at 0°C. This may be due to bad mixing of oxidizer and fuel preventing an intimate reaction. However, blended with norbornadiene, it showed a synergistic decrease in ID at 0°C, which is expected, due to faster cationic polymerization and a relatively slower but additional Diels-Alder reaction at the preignition stage. 3-Carene (IV) undergoes cationic polymerization with protonic acids (15). However, with decrease of temperature, the ID of carene with RFNA showed an increase and it turned nonhypergolic at 0°C (Table 1). This may be due to a possible positive activation energy for carene polymerization system. Blended with norbornadiene in equal amounts, carene failed to show any decrease in ID with RFNA when the initial temperature of the propellant was lowered. This may be explained in terms of the low activation energy ( - 2 0 to + 41 KJ/mol) generally associated with most carbonium ion polymerization where the polymerization rates do not increase rapidly with lowering of temperature [16].
TABLE 1 Ignition Delay of Norbornadiene and Its Equal Blends with Furfuryl Alcohol, Furfurylideneacetone and Carenc at Different T e m p e r a t u r e s with R F N A as Oxidizer. O = oxidizer; F = fuel Srl No.
F u e l / F u e l blend
1.
Norbornadiene(I)
2.
Furfuryl alcohol(II)
3.
Norbornadiene, I - furfuryl alcohol(II)
4.
Furfurylideneacetone(IIl)
5.
Norbornadiene(I)-Furfurylideneacetone(llI) Carene(IV)
Temperature °C
-
-
-
6. 7.
Norbornadiene(I)-Carene(IV) -
26 0 10 26 0 10 26 0 10 26 0 26 0 26 0 26 0 10
O / F by Volume (optimum)
Average ignition delay, ms
Standard deviation ms
2.0 2.0 2.0 2.0 2.0 2.0 2.4 2.4 2.4 2.0 2.0 2.4 2.4 3.5 -2.4 2.4 2.4
44 37.6 28.2 109.0 98.0 86.2 16.6 15.2 13.5 23.0 34.5 22.2 19.4 377.0 Non-hypergolic 55.0 59.3 61.0
0.57 0.5 0.5 4.1 4.0 4.0 0.5 0.6 0.6 0.5 0.8 0.4 0.5 8.3 -0.8 0.9 1.2
374
The authors thank Rear Admiral Ajay Sharma, A VSM, Director and Dean, IA T for permitting the publication of the paper. REFERENCES 1. Panda, S. P., and Kulkarni, S. G., Combu~t. Flame 28:25-31 (1977). 2. Panda, S. P., and Kulkarni, S. G., Def. Sci. J 27(2):77-80 (1977). 3. Panda, S. P., and Kulkarni, S. G., Combust. Flame 53:93-98 (1978). 4. Panda, S. P., and Kuikarni, S. G., J. Armt. Studies 11(2):138-139 (1976). 5. Kulkarni, S. G., and Panda, S. P., Combust. Flame 56:241-244 (1984). 6. Panda, S. P., Kulkarni, S. G., and Prabhakaran, C., Combust. Flame 76:107-110 (1989). 7. Furniss, B. S., Hannaford, A. J., Rogers, V., Smith, P. W. C. and Tatchell, A. R., Vogels Textbook of Practical Organic Chemistry, ELBS, Longman Group, London, 1978, p. 795. 8. Kulkarni, S. G., and Panda, S. P., Combust. Flame 40:29-36 (1981).
S . P . PANDA ET AL. 9. Kennedy, J. P., Cationic Polymerization of Olefins--A Critical Inventory, Wiley Interscience, New York, 1975, p. 223. 10. Siegfried, K. J., Furan Polymer, Cited in Encyclopedia of Polymer Science and Technology, (H. Mark and N. G. Gaylord, Eds., Wiley, New York, 1967, Vol. 7, pp. 435-437. 11. J. M. G. Cowie, Polymers: Chemistry and Physics of Modem Material, International Textbook Company, Aylesbury, 1973, p. 77. 12. Sawada, H., Thermodynamics of Polymerization, Marcel Dekker, New York, 1976. 13. Norman, R. O. C., Principles of Organic Synthesis, 2nd ed., Chapman & Hall, London, 1981, p. 291. 14. Fleming, I., Frontier Orbitals and Organic Chemical Reactions, Wiley, London, 1982, p. 22. 15. Panda, S. P., and Kulkarni, S. G., J. Polym. Sci. (Polymer Letters Edition) 21:649-656 (1983). 16. Eastham, A. M., Cationic Polymerization, cited in Encyclopedia of Polymer Science and Technology (H. Mark and N. G. Gaylord, Eds.), Wiley, New York, 1965, Voi. 3, p. 53.
Received 25 May 1993; revised 8 November 1993