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Energy & Fuels 2008, 22, 510–513
Bubble-Point Vapor Pressure Measurement for System JP-10 and Tributylamine by an Inclined Ebulliometer Yongsheng Guo,* Fengjun Yang, Yan Xing, Dan Li, Wenjun Fang, and Ruisen Lin Department of Chemistry, College of Science, Zhejiang UniVersity, Hangzhou 310027, People’s Republic of China ReceiVed July 10, 2007. ReVised Manuscript ReceiVed October 21, 2007
JP-10 has significant sensible heat sink capacities and may undergo endothermic chemical cracking for hypersonic aircraft applications without the problems associated with cryogenic fuels. Chemical initiators may accelerate the rate of cracking reactions and reduce the temperatures in a hypersonic aircraft heat exchanger/reactor. On the other hand, with the addition of an initiator some basic properties of JP-10 may change, such as volatility, which is directly related with ignition performance and combustion problems. Tributylamine (TBA) can be used as an effective initiator. Therefore, TBA and JP-10 blended fuel, as a potential fuel for hypersonic aircrafts, is worthwhile for further study. In the present work, the bubble-point vapor pressures and equilibrium temperatures for mixtures of JP-10 and TBA with different mass fractions were measured by comparative ebulliometry with inclined ebulliometers. Vapor pressures and equilibrium temperatures were correlated by Antoine’s equation with satisfactory precision. The bubble-point lines of pressure versus composition at different temperatures and temperature versus composition at different pressures were obtained. The mixtures exhibit positive deviations from Raoult’s law. It follows that the addition of TBA does not have a distinct effect on the vapor pressure and the phase equilibrium behavior of JP-10.
1. Introduction High heat sink fuel cooling technology can be applied to enhance engine performance over the entire spectrum of flight regimes. For hypersonic flight, it provides the only means for meeting the cooling requirements with storable fuels; for advanced fighter aircrafts, it provides an identifiable path to achieving IHPTET performance goals with current materials; and, for lower-speed military and commercial aircrafts, it can increase growth potential and play a key role in emission-reduction strategies. Although cryogenic fuels, such as liquid methane and liquid hydrogen, can provide sufficient cooling, they require large vehicles (because of low densities) and present cost, logistics, operational, and safety problems. The single-component hydrocarbon fuel known as JP-10 (chemical formula C10H16) is synthetically produced by the hydrogenation of dicyclopentadiene and is used in volume-limited combustion chambers. JP-10 has significant heat sink capacities for supersonic aircraft applications and may undergo endothermic chemical cracking for hypersonic missile applications without the problems associated with cryogenic fuels.1–3 At high Mach numbers, heat loads of aircraft exceed those available from sensible heating of the fuel. Therefore, endothermic reactions are needed to augment the cooling capacity of the fuel. Heterogeneous catalysis can increase the severity of cracking, but * To whom correspondence should be addressed. Telephone: +86-57187952371. Fax: +86-571-87951895. E-mail:
[email protected]. (1) Huang, H.; Sobel, D. R.; Spadaccini, L. J. Endothermic heat-sink of hydrocarbon fuels for scramjet cooling. 38th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, Indianapolis, IN, July 7–10, 2002. (2) Davidson, D. F.; Horning, D. C.; Oehlschlaeger, M. A.; Hanson, R. K. The decomposition products of JP-10. 37th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, Salt Lake City, UT, July 8–11, 2001. (3) Korabelnikov, A.; Kuranov, A. Thermal protection using endothermic fuel conversion. AIAA/CIRA 13th International Space Planes and Hypersonics Systems and Technologies Conference, Capua, Italy, May 16–20, 2005.
Table 1. JP-10 Fuel Properties specific gravity at 20 °C (g cm-3) viscosity at 40 °C (mm2 s-1) boiling temperature (°C) relative molecular mass
0.926 2.297 184.6 135.9
the use of a solid catalyst complicates the design and construction of the heat exchanger/reactor. Another problem with solid catalysts is a limited lifetime. Catalysts can fail by either deactivation or disbanding from the metal surface. If a catalyst is used, periodic regeneration of the catalyst is likely to be required. The use of an initiator for cracking has been suggested.4,5 An initiator can improve the cooling capacity of the hydrocarbon fuel, such as JP-10. On the other hand, with the addition of an initiator, some basic properties of JP-10 may change, such as volatility, which is directly related with ignition delay and combustion problems. Tributylamine (TBA) can be used as an effective initiator. Therefore, TBA and JP-10, as a potential blended fuel for hypersonic aircrafts, is worthwhile for further study. In the present work, the equilibrium vapor pressure of mixtures of TBA and JP-10 are investigated. The bubble-point pressures of mixtures as a function of temperature were measured by comparative ebulliometry using inclined ebulliometers.6–10 The bubble-point lines of pressure versus composition at different temperatures and temperature versus composition at different pressures were obtained. The results may provide important information on the essential thermodynamic property of volatility (4) Wickham, D. T.; Engel, J. R.; Hitch, B. D.; Karpuk, M. E. Initiators for endothermic fuels. J. Propul. Power 2001, 17, 1253–1258. (5) Wickham, D. T.; Engel, J.; Roonery, S.; Hitch, B. D. Additives to increase fuel heat sink capacity in a fuel/air heat exchanger. 41st AIAA/ ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, Tucson, AZ, July 7–10, 2005.
10.1021/ef700396k CCC: $40.75 2008 American Chemical Society Published on Web 11/27/2007
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Table 2. Bubble-Point Vapor Pressure Data for JP-10 Plus TBA Systems T (K)
P (kPa)
T (K)
P (kPa)
T (K)
P (kPa)
T (K)
P (kPa)
T (K)
P (kPa)
WTBA % ) 1.0000 432.30 22.24 439.52 27.57 443.55 31.19 446.52 34.11 448.52 36.21 451.71 39.78 455.17 43.98 459.60 49.91 462.83 54.64 465.72 59.20 468.54 63.94 473.29 72.67 478.09 82.46 481.39 89.82 487.04 102.29
WTBA % ) 0.7946 400.06 16.37 404.89 19.34 410.78 23.64 417.00 28.61 422.26 33.62 427.86 39.06 432.63 44.12 435.60 49.12 440.19 55.04 443.23 60.03 449.49 70.34 452.26 75.14 455.28 80.86 459.50 90.76 461.82 95.45 464.77 101.50
WTBA % ) 0.5950 404.89 19.34 407.40 21.08 413.69 25.81 422.76 33.95 426.34 38.36 430.88 43.25 434.58 48.23 437.70 53.09 440.71 57.95 443.61 63.10 446.32 67.95 449.21 73.45 451.77 78.06 455.44 85.86 459.84 95.30 462.81 102.06
WTBA % ) 0.4037 400.97 17.83 407.13 21.53 415.56 28.73 420.55 33.69 425.18 38.36 429.58 43.34 432.88 48.03 435.54 52.18 438.54 55.87 442.84 62.57 444.76 66.27 446.63 70.30 454.72 87.14 457.23 92.46 461.58 101.59
WTBA % ) 0.1987 404.15 20.22 412.14 26.17 418.67 32.02 423.23 36.76 428.50 42.90 432.59 48.20 435.96 52.99 439.43 58.28 442.80 63.82 445.71 69.01 448.32 73.89 450.97 79.18 453.46 84.31 455.99 89.96 458.51 95.71 460.76 101.22
WTBA % ) 0.1006 404.89 21.85 410.82 26.38 416.53 31.57 422.35 37.62 427.25 43.45 431.09 48.50 435.91 55.55 439.28 60.91 442.52 66.51 445.73 72.39 448.20 77.26 450.54 82.04 453.00 87.41 455.35 92.74 457.65 98.19 459.06 101.31
WTBA % ) 0.0799 403.22 20.85 409.69 25.70 415.65 31.02 421.23 36.68 425.56 41.65 429.62 46.86 433.21 51.85 436.66 57.08 440.61 63.55 443.58 68.83 446.10 73.50 448.89 79.03 451.63 84.82 453.88 89.81 456.17 95.08 458.56 101.13
WTBA % ) 0.0627 403.31 21.04 410.14 26.27 415.71 31.10 422.85 38.81 428.02 45.14 432.09 50.71 435.36 55.56 438.78 61.02 441.77 66.19 445.03 72.16 447.74 77.46 450.27 82.72 452.84 88.08 455.24 93.65 457.31 98.64 458.62 101.92
WTBA % ) 0.0407 400.37 19.33 406.23 23.39 414.21 30.15 419.48 35.42 424.34 40.99 430.15 48.44 433.85 53.76 436.96 58.57 440.44 64.53 443.13 69.47 446.00 75.03 448.98 80.62 451.30 85.59 453.98 91.52 455.68 96.35 457.91 101.92
WTBA % ) 0.0215 400.81 19.77 406.76 24.04 413.41 29.70 418.79 35.01 423.72 40.55 427.76 45.86 431.74 51.11 435.12 56.18 438.49 61.57 441.31 66.50 444.24 71.85 447.04 77.32 449.61 82.63 452.00 87.81 454.24 92.97 456.39 98.36 457.94 101.99
WTBA % ) 0.0000 405.26 23.12 411.85 28.53 417.94 34.44 422.67 34.44 427.40 39.70 431.07 45.53 434.72 50.60 437.56 56.57 444.18 61.61 446.78 72.25 449.29 77.35 451.95 82.50 454.05 88.27 456.12 98.03 457.78 102.02
Table 3. Correlation Results of Vapor Pressure by Antoine’s Equation for JP-10 Plus TBA Systems WTBA (%) 100.00 79.46 59.50 40.37 19.87 10.06 7.99 6.27 4.07 2.15 0.00
data points 15 16 16 15 16 16 16 16 16 17 15
temperature range (K) 432–488 400–465 404–463 400–462 404–461 404–460 403–459 403–459 400–458 400–458 405–458
Antoine’s equation coefficients A B × 10-3 C 14.006 3.637 99.184 12.906 2.971 106.135 13.592 3.294 95.192 13.449 3.223 96.219 14.663 4.115 51.085 14.562 4.019 54.747 14.750 4.166 47.534 14.325 3.833 63.521 15.037 4.362 39.198 14.478 3.945 57.603 12.792 2.783 117.037
that relates to ignition performance, operability of storage, and the stability and security properties of the fuel. 2. Experimental Section 2.1. Materials and Characterization. TBA with a purity of over 99.0% as claimed by the supplier, Sinopharm Chemical
AAD (kPa) 0.236 0.285 0.312 0.383 0.019 0.047 0.035 0.047 0.148 0.056 0.206
ARD (%) 0.503 0.541 0.576 0.709 0.030 0.069 0.053 0.091 0.190 0.088 0.361
Reagent Company, was used without further purification. The hydrocarbon fuel JP-10 is provided by the Liming Research Institute of Chemical Industry. The physical parameters are listed in Table 1. 2.2. Vapor Pressure Measurements. An inclined ebulliometer with a pump-like stirrer and the comparative ebulliometry were used. The structure and operation of the apparatus has been
512 Energy & Fuels, Vol. 22, No. 1, 2008
Guo et al. measured over the equilibrium pressure range from about 16.0 to 101.3 kPa.
3. Results and Discussion
Figure 1. Comparison of the vapor pressure data of ethanol.
Bubble-point vapor pressures at various temperatures for 11 systems with different compositions of TBA and JP-10 were measured. The experimental data are listed in Table 2, where W is the mass fraction and T is the bubble-point temperature. The vapor pressure data for ethanol are compared to the literature data11 in Figure 1; they are in reasonable agreement. The deviation of the vapor pressure for ethanol from the literature data is 0.46% at 320 K, and the maximum deviation is around 1.57% at 350 K. Figure 2 gives the change of vapor pressures for several mixtures with different compositions of JP-10 and TBA against the temperature. Pure TBA has a lower vapor pressure, which is not in favor of ignition performance, but the mixtures even with a high composition of TBA have similar values to JP-10. Therefore, the addition of TBA almost does not have distinct effects on the vapor pressures and the phase equilibrium behavior of JP-10. A nonlinear regression method was used to fit the vapor pressure data to Antoine’s equation ln p ) A -
B T - C
(1)
where p is the vapor pressure in Pa, T is the equilibrium temperature in K, and A, B, and C are constants. Table 3 gives the Antoine constants, together with the errors given by the average absolute deviation (AAD) and average relative deviation (ARD)12
∑| n
AAD ) Figure 2. Vapor pressure at different TBA mass fractions (WTBA).
ARD ) described in detail previously.6 The bubble-point temperatures of a sample and a reference material of ethanol in two separate ebulliometers were measured under the same pressure, which avoided the necessity of measuring the equilibrium pressure directly with a mercury manometer; the pressure could be calculated from the boiling temperature of ethanol and its wellknown pressure-temperature behavior. The temperatures inside the two ebulliometers were measured with two standard platinum resistance thermometers connected to Keithley 195A digital multimeters. Vapor pressures at various temperatures were (6) Sun, H.; Fang, W.; Guo, Y.; Lin, R. Investigation of bubble-point vapor pressures for mixtures of an endothermic hydrocarbon fuel with ethanol. Fuel 2005, 84, 825–831. (7) Schwarz, B. J.; Wilhelm, J. A.; Prausnitz, J. M. Vapor pressures and saturated-liquid densities of heavy fossil-fuel fraction. Ind. Eng. Chem. Res. 1987, 26, 2353–2360. (8) Li, H.; Han, S.; Teng, Y. Bubble points measurement for system chloroform-ethanol-benzene by inclined ebulliometer. Fluid Phase Equilib. 1995, 113, 119–127. (9) Ambrose, D.; Ewing, M. B.; Ghiassee, N. B.; Sanchez Ochoa, J. C. The ebulliometric method of vapor-pressure measurement: Vapor pressure of benzene, hexafluorobenzene, and naphthalene. J. Chem. Thermodyn. 1990, 22, 589–605.
|
1 p - pexp n i ) 1 cal i
∑|
(2)
|
n pcal - pexp 1 × 100% ni ) 1 pexp i
(3)
where n is the number of the experimental data points. From the correlation results, the lines of p-WTBA at several temperatures and T-WTBA at several pressures are shown in Figures 3 and 4, along with the departures of the equilibrium temperature and pressures from the linear addition values. Clearly, the mixtures of JP-10 and TBA have a positive deviation on the values of pressures from Raoult’s law and a negative deviation on the values of temperatures. The pressure departure increases with temperature, and the maximum pressure departure ∆p among the six temperatures is about 23.7 kPa at 450 K. Temperature departures affected by pressure are minor (10) Guo, Y.; Zhong, J.; Xing, Y.; Li, D.; Lin, R. Volatility of blended fuel of biodiesel and ethanol. Energy Fuel 2007, 21, 1188–1192. (11) Diogo, H. P.; Santos, R.; Nunes, P. M.; Minas da Piedade, M. E. Ebulliometric apparatus for the measurement of enthalpies of vaporization. Thermochim. Acta 1995, 249, 113–120. (12) Wang, Z.; Fang, W.; Lin, R.; Guo, Y.; Zhou, X. Volatility of blended fuel of endothermic hydrocarbon fuel and triethylamine. Fuel 2006, 85, 1794–1797.
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Figure 3. Bubble-point vapor pressure against composition at several temperatures (left) and departures of the equilibrium pressure from the linear addition values (right).
Figure 4. Bubble-point temperature against composition at several pressures (left) and departures of the equilibrium temperature from the linear addition values (right).
in the range of 50–100 kPa. The maximum temperature departure, ∆T, is around –17 K. 4. Conclusion Bubble-point vapor pressures for the systems of JP-10 with TBA were measured satisfactorily by comparative ebulliometry with inclined ebulliometers. The bubble lines of equilibrium pressure or temperature versus composition can be obtained from the correlation on the experimental results. The binary system of JP-10 plus TBA appears with positive deviations from Raoult’s law.
Acknowledgment. The authors are grateful to the National Natural Science Foundation of China (20703036).
Nomenclature AAD ) average absolute deviation A, B, and C ) Antoine constants ARD ) average relative deviation exp ) experimental value p ) vapor pressure, kPa T ) equilibrium temperature, K ref ) reference value W ) mass fraction EF700396K
