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Method and Apparatus for the Thermal Stress of Complex Fluids: Application to Fuels Thomas J. Bruno* and Bret C. Windom Thermophysical Properties Division, National Institute of Standards and Technology, Boulder, Colorado, United States ABSTRACT: In this brief article we describe a simple apparatus that can produce sufficient quantities of thermally stressed complex fluids (such as fuels) to allow a full range of thermophysical property measurements to be performed on the resulting fluid. The apparatus operates in a continuous rather than batch mode, and consists of a high pressure pump, a reactor section, a quench, and a collection vessel. The apparatus is capable of operation to 55 MPa, 600 °C, with residence periods that are chosen on the basis of a wide range of fluid flow rates. Automation of the temperature and pressure control allows for safe, unattended operation. We have used this apparatus to generate thermally stressed rocket kerosene (RP-1 and RP-2) at 475 and 510 °C, and at a pressure of 17 MPa. We have verified that the thermally stressed fluid is comparable in composition to fluids that result from careful thermal decomposition kinetics measurements that are done in ampule reactors.
’ INTRODUCTION A large-scale research effort geared toward characterizing the thermophysical properties of kerosene-based fuels (for rocket and aircraft applications) is in progress at the National Institute of Standards and Technology (NIST) as well as other facilities.125 The goal of this work is to enhance design and operational specifications for these fluids, and to facilitate new applications in advanced engines. Another important aspect that is peripheral to the main effort is research and development on alternative (and renewable) substitutes and extenders for the more traditional petroleum based fuels, especially for aircraft. Regardless of the ultimate application, physicochemical characterization of the fuels is a critical component of the knowledge base that is required. The physicochemical aspects must address two distinct issues: the physico part and the chemical part. While the chemical aspect speaks to composition and variability of the chemical constituents of the fuel, the physico (or thermophysical) part, mentioned above, addresses properties that are required to develop reliable models for equilibrium, thermal, and transport properties. The properties that are required for model development include the fluid density, vapor pressure, volatility, heat capacity, viscosity, and thermal conductivity. Some of these property data for rocket fuels (RP-1 and RP-2) and turbine fuels (Jet-A, JP-8, and substitutes) have already been reported (see the references above). Moreover, in many cases the thermophysical property models have also been developed. These models are typically implemented in software packages that facilitate use by engine designers. The primary NIST model platform for this purpose is the REFPROP computer program.26 The logical paradigm when measuring such thermophysical properties for finished fuels (especially properties that are to be used for model development) is to maintain the fluids in as close to the as-received or pristine condition as possible. In other words, during the course of a measurement, care must be taken to avoid decomposing or changing the fluid sample in any way. Note that this also includes taking care to preserve the presence of the more volatile constituents which might be otherwise lost, This article not subject to U.S. Copyright. Published 2011 by the American Chemical Society
and therefore cause erroneous property measurements. Clearly, it is deleterious to make measurements on a fluid that is, or becomes poorly characterized by, for example, high temperature, high pressure, the catalytic effect of wetted surfaces, or evaporation. Of these factors, the effects of high temperatures can often be the most influential cause of thermophysical property changes. For this reason, it is typical to address the potential of thermal decomposition with kinetic studies before any property measurement is done.2732 On the other hand, there are important reasons for explicitly considering fuel that has decomposed to a greater or lesser extent under the influence of residence time at high temperature.9 This interest is related to the actual mode of use for many real fuels.3344 In rocket engines, for example, a portion of the fuel is used as a heat sink in the nozzle (to prevent excessive metal erosion and engine failure) before being burned with the oxidizer in the combustion chamber.45 In hypersonic aircraft, the fuel is used as a heat sink to cool leading edge surfaces and engine components before being burned in the combustors.46 Even in many subhypersonic (but supersonic) military aircraft, the fuel is used as a heat sink for many critical components. In some cases, the fuels may enter the supercritical fluid state and react to produce socalled endothermic fuels.36 For these reasons, there is a great deal of interest in the physicochemical character of fuels that have been partially decomposed or thermally stressed. Indeed, the study of thermally stressed rocket kerosene was an important issue that emerged as being a critical need during a workshop on the properties of RP-1 and RP-2, held at NIST in Boulder, Colorado in 2008.9 The temperature and pressure regimes in the heat sink cycles of rocket engines in particular are very severe, with temperatures near 1200 °C, and pressures of 17 MPa (2500 psig). Although the average residence time in the nozzle cooling channels at these Received: March 28, 2011 Revised: May 2, 2011 Published: May 02, 2011 2625
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Figure 1. Achematic diagram of the continuous flow thermal stress apparatus.
conditions is short (seconds or less), the exposure is sufficient to significantly change the fluid chemistry. Furthermore, for fuel film-cooled engines, a fuel barrier exists in close proximity to high-temperature gaseous combustion products. Structural limitations of materials used in rocket thrust chambers limit continuous high-temperature operation under extreme stress. However, in other advanced propulsion applications such as actively cooled hypersonic vehicles, the use of high-temperature alloys and longer average residence time can result in even greater fuel bulk temperatures. Rocket kerosenes that consist of mainly isoparaffins in the as-delivered fluid show breakdown into polynuclear aromatic hydrocarbons, some light gases (hydrogen, methane, ethane, and lower olefins), and coke particles that consist of carbonaceous structures.41,4762 Currently, test rigs are available to thermally stress fuels in the very high temperature and low residence time regimes.33,35,38 The primary interest in the application of these facilities is to study the coke formation and deposition on wetted surfaces.41,47,53,55,63 This has also been done to assess substrate surface fouling, since in an operating engine, fouling of the cooling channels can be a cause of catastrophic failure. It has become clear, however, that greater attention must be paid to the fluid itself, and while the high temperature regime is important, we must systematically begin consideration with the lower temperature region up to approximately 500 °C, and pressures of 17 MPa. In particular, it is now recognized that we must measure and model the thermophysical properties of fuel that has been stressed under these controlled conditions.9 In prior work, we have developed several apparatus and methods to screen fuels for decomposition and to measure the thermal decomposition reaction rate constants for fuels and fuel components.64,65 We have applied these techniques to RP-1, RP-2 (and also these two fluids with stabilizing additives),27,29,31,32,66,67 Jet-A,28 JP-10,4 and several pure fluid components of fuel and working fluids.30,6872 Both the screening and kinetics measurement apparatus utilize batch ampule reactors and off-line analysis as a function of exposure time. These approaches and apparatus provide a well controlled and well characterized reaction pathway, capable of generating thermal decomposition kinetic data, including the evaluation of corrosivity of the product suite.7375 While it is possible, in principle, to generate thermally stressed fuel with an adaptation of such a batch apparatus, the throughput would be very low. A more suitable and practical approach
would be one that employs a continuous or dynamic method. Even with such a dynamic approach, careful control of temperature, pressure, and residence time is needed to assign at least an approximate pedigree to any resulting sample of thermally stressed fuel.
’ EXPERIMENTAL SECTION The apparatus that has been designed and constructed for the thermal stress of fuels by use of a dynamic approach is shown schematically in Figure 1. The apparatus consists of a high pressure syringe pump capable of generating 55 MPa (8000 psig), at constant flow rates that may be specified on the controller. Fluid thus pressurized is delivered into a high temperature reactor consisting of a 25 cm length of 316 L stainless steel capillary tubing having a nominal outside diameter of 1.6 mm (1/16 in.), and an inside diameter of 0.05 mm (0.020 in.). The length of tubing that serves as the reactor is tightly coiled around a mandrel that accommodates a 250 W cartridge heater. The tubing thus coiled is in contact with the mandrel, and is coated with a high thermal conductivity potting compound (that was developed at NIST) made from moldable ceramic and aluminum powder.76 The reactor tubing and potting compound is covered by a 400 series stainless steel heat shield surrounding the reactor tubing. A platinum resistance temperature sensor (for both measurement and control) is potted with the reactor capillary coil, in contact with the reactor tubing. The cartridge heater is set into the mandrel with titanium nitride to provide efficient heat transfer and to prolong the heater life. The reactor is capable of generating a controlled temperature of 600 °C. The repeatability of the temperature is 1 °C at temperatures to 475 °C, and 5 °C at temperatures between 500 and 600 °C. The space surrounding the reactor is filled with Pyrex wool insulation, and the entire reactor assembly is contained in a sealed stainless steel chassis box. The insulation is sufficiently effective so that even with the reactor operating at 600 °C, the exterior of the cabinet is merely warm to the touch. While the reactor we have used here is a typical stainless steel used in laboratory apparatus, we recognize that other materials may be desirable for the wetted surface. It is a simple matter to make reactor sections, complete with heater and temperature sensor, of many materials such as copper, Silcosteel, Inconel, or Hastalloy.73 The fact that we have used a stainless steel reactor in this present apparatus must be considered as an additional variable in 2626
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Energy & Fuels the interpretation of the results. To the extent that the wetted surface may play a role in the reaction mechanism at a given temperature and pressure, one must realize that this can change with other wetter surface materials. One can determine, at least in an approximate way, whether the mechanism is primarily thermal or primarily catalytic by an examination of the vapor products that are present.77 Following the reactor, the fluid is directed via stainless steel capillary tube into a chilled water bath heat exchanger that is maintained at between 5 and 10 °C. This serves to quench the reaction and cool the thermally stressed fluid prior to entering the pressure control. The length of tubing following the reactor, leading to the water bath, is minimized in order to minimize the exit end effect (that is, the transition from the reactor to the quench). Subsequent to the heat exchanger, the fluid is directed into a back pressure regulator (made from polyether ether ketone, PEEK). The back pressure is variable and can be set to achieve a range of desired back pressures. The combination of syringe pump control and back pressure regulator can provide a controlled, constant flow rate at any desired nominal pressure. In this way, the residence period can also be controlled. Moreover, the temperature and pressure controllers are capable of continuous automated operation. A fitting on the back pressure regulator leads directly into a collection vessel. At this point in the process, as mentioned above, the fluid is chilled to below room temperature. The vessel (actually a polyethylene bottle) is maintained at atmospheric pressure. Although no provision is made to exclude air or to condition the thermally stressed sample that is collected, most air inside this vessel is displaced by the vapor fraction that emerges with the thermally stressed liquid. Although no temperature control is currently applied to the collection bottle, it is a simple matter to add this feature when desired. Downstream from the collection vessel is an activated charcoal trap, the purpose of which is to absorb vapors and to prevent back diffusion of air into the vessel. While the pressure rating of the coiled tube reactor is approximately 88 MPa (12 800 psi) at 100 °C, it must be derated to 55 MPa (8000 psi) at 500 °C. As a precaution, the upper pressure (or alarm condition) limit of the syringe pump is typically set well below this pressure, at 20 MPa (3000 psi), for all practical thermal stress cycles. Moreover, while it is possible, in principle, to control and maintain a temperature in excess of 600 °C, the upper temperature (or alarm condition) temperature was set at 550 °C for all thermal stress cycles performed thus far with the apparatus. The syringe pump can be operated to deliver a constant pressure (repeatable to 7 kPa, 1 psig) or constant flow rate (repeatable to 0.005 mL/min). To obtain a constant and controlled residence period, one simply sets the flow rate and then uses the back pressure regulator to obtain the desired pressure. With this mode of operation, the flow rate is very precise, but the pressure obtained in the reactor can vary by approximately 0.3 MPa, 50 psig). This is not problematic because pressure is a relatively weak variable in the characterization of thermal stress of fuels. Moreover, the pressure control and repeatability in an operating rocket engine is far more uncertain and variable than the 0.3 MPa of this apparatus. Indeed, pressure repeatability is not an issue in a rocket engine; we raise the issue here only because it is an issue in production of research samples upon which modeling work is to be performed. The most useful feature of the apparatus is the ability to generate an appreciable quantity of well characterized (in terms
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of temperature, pressure, and residence period) thermally stressed fuel in a safe manner without significant operator attention. One can produce between 0.5 and 1 L of fluid per week. This quantity is suitable for a complete measurement suite of volatility, density, speed of sound, viscosity, and thermal conductivity. The automated features allow us to operate the apparatus in 12-h shifts; the main limitation being the capacity of the syringe pump. We must shut down the reactor for a few minutes after 12 h of operation to fill the fluid reservoir. This only requires 30 min, after which the apparatus can operate unattended for another 12 h period.
’ RESULTS AND DISCUSSION The initial application of the thermal stress apparatus was done with two rocket kerosenes: RP-1 and RP-2. The RP-1 was obtained from the Air Force Research Laboratory, Propulsion Directorate at Wright Patterson Air Force Base. The RP-2 was obtained from the Air Force Research Laboratory, Propulsion Directorate at Edwards Air Force Base. Each of the samples was used without treatment or purification. Care was taken to minimize exposure to the atmosphere (to minimize oxidation), evaporation of the more volatile components, and uptake of moisture. The sample of RP-1 is from a batch that has previously been used for extensive property measurement and modeling. The sample has, in the course of that work, been considered representative of rocket kerosenes, although significant variability among batches and preparation recipes has recently become better appreciated.1 As with RP-1, the sample of RP-2 was also from a batch used previously for extensive property measurement and modeling. Unlike RP-1, however, there have only been two batches of RP-2 produced to date. Thus, the compositional and property variability is less well characterized. The sample of RP-1 was pink because of the presence of athe dye azobenzene-4-azo-2-naphthol. This sample has been subjected to an extensive chemical analysis in the previous work mentioned in the above paragraph. This analysis was done with a gas chromatographymass spectrometryinfrared spectrophotometry method (30 m capillary column of 5% phenyl dimethyl polysiloxane, having a thickness of 1 μm, temperature program from 90 to 250 °C, 10 °C/min). Mass spectra were collected for each peak from 15 to 550 RMM (relative molecular mass) units, and infrared spectra were collected between 4000 and 600 cm1.78 The assignment of the peaks of the major components (having an area percent in excess of 1%) was presented earlier.3,21 This fluid is primarily composed of linear and branched paraffins, cycloparaffins, alkenes, and some aromatics. The sample of RP-2 was clear and colorless (no dye is added to this fuel). The RP-2 was also analyzed by gas chromatography mass spectrometryinfrared spectrophotometry (30 m capillary column of 5% phenyl dimethyl polysiloxane, having a thickness of 1 μm, temperature program from 70 to 260 °C, 7 °C/min, and a ballistic heating step to 300 °C). The peaks having an area percentage in excess of 1% were assigned. RP-2, like RP-1, is composed primarily of linear and branched paraffins with some aromatics. The apparatus of Figure 1 was used to thermally stress RP-1 and RP-2 at temperatures of 475 and 510 °C. For each temperature, the reactor was maintained at a pressure of 17 MPa (2500 psi). The uncertainty in temperature and pressure were discussed above. For each temperature, the flow rate was maintained at 0.100 mL/min to provide a residence period of approximately 2627
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Figure 2. Total ion chromatograms showing the progression of thermal stress from the as-received RP-1, to stress at 475 and 510 C (at 17 MPa, residence time 0.51 min). The emergent suite of decomposition products at the beginning of the chromatograms of the thermally stressed samples mirrors that observed in our earlier kinetics measurements.
0.51 min. Under these thermal stress conditions, a significant vapor phase develops in both fuels. At 475 °C, the vapor phase constituted approximately 30% (mass/mass) of the products, while at 510 °C it constituted 50% (mass/mass). The vapor products consisted mainly of hydrogen, methane, and some lower (C2C3) hydrocarbons. Although it is possible to capture the vapor for separate testing (indeed, the apparatus is easily modified to capture both phases simultaneously), our primary interest here was the generation and subsequent measurement of the recovered liquid. The liquid recovered after thermal stress at 475 °C had a deep yellow or amber cast. The liquid after thermal stress at 510 °C had a deep amber or light brown cast. Some comment is warranted regarding the philosophy by which we separate the gas and liquid streams for separate measurement, since in an operating rocket engine, it is the composite stream (both the generated gaseous phase and the thermally stressed liquid phase) that is burned. Therefore, it might be argued that the separation is superfluous, if not deceptive, in that it results in an unrealistic fluid. From our point of view, however,
in the measurement and modeling of complex fluid thermophysical properties, the treatment of these two streams is very different. Indeed, one would apply completely different instruments to the measurement of the gaseous and liquid viscosities and densities, for example. The presence of appreciable hydrogen in the gaseous products makes a significant difference in the kind of apparatus that can be used. Thus, for the purpose of development of thermophysical property measurements (and many other types of measurements as well), separate consideration of the two phases is critical. In terms of the subsequent modeling, separate consideration of the two streams is sometimes useful, but not critical. Modern thermodynamic models can handle a variety of properties, over a wide range of conditions, almost seamlessly. Indeed, difficulties are typically only encountered when components that differ greatly in chemical properties (polarity, polarizability, etc.) are studied. Thus, one might separately model the two streams if, for example, there was a desire to implement surrogate mixture models with fewer rather than more constituents, to minimize computation time. 2628
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Figure 3. Histogram showing the results of the moiety family analysis based on ASTM D-2789. The ordinate is in units of volume fraction.
The operating conditions discussed above were chosen as the basis for initial study of thermally stressed rocket kerosene. We are by no means restricted to these conditions, however. It is likely that in the future, follow-on work will be done at different temperatures, pressures, and residence times. The apparatus is sufficiently flexible to allow a wide range of operating conditions to be simulated. It is critical that we ensure that the fluid produced by the thermal stress apparatus is in fact consistent with expectations that are based upon prior experience. We appreciate that the large potential variability in the chemical composition of rocket kerosene can affect the thermal stressed fluid that is obtained. For the batches of RP-1 and RP-2 that were used here, we had previously characterized in detail the global thermal decomposition kinetics with an ampule reactor method. For RP-1, the rate constant measurements extended to 500 °C, while for RP-2, the measurements extended up to 450 °C. In those measurements, discussed earlier, the residence periods ranged from 10 to 600 min, primarily to obtain valid rate constants over a range of reaction periods. Thus, we recognize that in the present work, with residence periods controlled to 0.51 min, the kinetic studies are not exactly analogous. We can, however, use the earlier work to assess the reaction products in an approximate way. For both RP-1 and RP-2, the major compositional change noted in the kinetics measurements was an emergent suite of light to moderate relative molecular mass products. These products, identified and measured with gas chromatography, appeared in a retention period range that contained few if any components of the starting fluid, thus making the emergent suite ideal for a kinetic measurement. In fFigure 2, we present total ion chromatograms (30 m capillary column of 5% phenyl dimethyl polysiloxane, having a thickness of 1 μm, temperature program from 90 to 250 °C, 10 °C/min, mass selective detection from 15 to 550 relative molecular mass units) of RP-1, and the thermally stressed fluid from 475 and 510 °C, respectively. We note that at 475 °C, we observe the emergent suite that has developed even after a residence period of 0.51 min. This cluster is essentially the
same as that obtained in the earlier kinetics measurements.27,29,31,32,67 We note a significant change in the reaction chemistry at 510 °C. Here, the emergent suite is much larger, and in fact includes larger (higher relative molecular mass) cracking products. We also note (from a detailed peak by peak analysis) the emergence of more aromatic and naphthalenic compounds, and a decrease of linear and branched aliphatic compounds, at the higher temperature. This mirrors the compositional trends that were observed during the kinetics measurements. Moreover, similar compositional trends have also been observed by other workers with different approaches.4851,57,5962,79 An alternative means of tracking the change shown in Figure 2 is to characterize the chemical family moieties. We have done this with an adaptation of ASTM method D-2789. In this method, GCMS is used to characterize hydrocarbon samples into six types. The six types or families include the following: paraffins, monocycloparaffins, dicycloparaffins, alkylbenzenes (arenes or aromatics), indanes and tetralins (grouped as one classification), and naphthalenes. Although the method is specified only for application to low olefinic gasoline, and has significant limitations, it is of practical relevance to many complex fluid analyses, and is often applied to gas turbine fuels, rocket propellants, and missile fuels. In Figure 3, we present the results of this analysis for the thermally stressed RP1. Here, the effects of thermal stress are seen to be incremental at 475 °C, but quite dramatic at 510 °C. At 510 °C, one observes a sharp decrease in paraffins, a sharp increase in aromatics, and smaller increases in indanes, tetralins, and naphthalenics. This is completely consistent with our earlier observations. We would be remiss if we failed to address at least in an approximate way the repeatability of the thermally stressed fluid that we could produce with the apparatus described here. In a typical 12-h work shift, we are able to process approximately 72 mL of starting fluid, assuming a residence period of 0.51 min. Accounting for the gas fraction of the thermal stress product, we can typically recover between 30 and 50 mL of thermally stressed liquid per work shift. Performing the chromatographic analyses described earlier on each of the 12-h aliquots of fluid allows us to 2629
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Energy & Fuels track the repeatability of the thermally stressed fluid that we are producing. We have found that the chromatographic profiles of 12-h aliquots are remarkably similar to one another. The peaks obtained do not vary, and their areas (corresponding to the concentration) vary only by few percent. As a result of the repeatability that we are routinely able to achieve, we are confident enough to place each 12-h aliquot of the thermal stress product in a commingled, refrigerated (7 °C) stock liquid container, so that the fluid used for the ultimate property measurement is uniform. This serves also to minimize the potential of spillage of large volumes of thermally stressed fluid when removing an aliquot from the apparatus. Always of concern when operating an apparatus such as this is the potential of coking, especially in the reactor section but also as a potential foulant in the back pressure regulator valve. During operation, this would be manifest in an increasing pressure, while the pump maintains the desired flow rate and residence time. Our experience with the apparatus shows that fouling does indeed occur in the back pressure regulator when the apparatus is operated at 510 °C, but not at 475 °C. The fouling was easily eliminated by flushing the valve with unreacted rocket propellant to clear the accumulated particulates. We never experienced fouling in the reactor section, even after operation at 510 °C.
’ CONCLUSIONS In this brief paper, we present a simple yet flexible apparatus that provides appreciable quantities of thermally stressed complex fluids such as fuels. It is important to be able to produce such samples, since thermal stress of fuels will occur in engines and machinery, and it is often critical to measure and model the properties of such fluids. The apparatus allows simultaneous control of reaction temperature, pressure, and residence period. The apparatus can run unattended in a safe manner. In this work we focused on producing thermally stressed liquid, although simple modifications can allow for the separate collection of the liquid and gaseous phases of the decomposition products, or even a two-phase collection. We demonstrated the compositional consistency of the thermally stressed fluid from this apparatus with carefully controlled kinetics measurements. We conclude that the apparatus presented provides a valuable framework to study in any depth desired the effect of thermal stress on complex fluids such as fuels. ’ AUTHOR INFORMATION Corresponding Author
*E-mail:
[email protected].
’ ACKNOWLEDGMENT The financial support of the Air Force Research Laboratory (MIPR-F1SBAA0138G001) is gratefully acknowledged. B.C.W. gratefully acknowledges a National Academy of Sciences/National Research Council Postdoctoral Associateship. ’ REFERENCES (1) Lovestead, T. M.; Windom, B. C.; Riggs, J. R.; Nickell, C; Bruno, T. J. Assessment of the compositional variability of RP-1 and RP-2 with the advanced distillation curve approach. Energy Fuels 2010, 24, 5611–5623. (2) Billingsley, M.; Edwards, J. T.; Shafer, L. M.; Bruno, T. J. Extent and impacts of hydrocarbon fuel compositional variability for aerospace propulsion systems. 46th AIAA/ASME/SAE/ASEE Joint Propulsion
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Conference and Exhibit, Paper AIAA 2010-6824, Nashville, TN, 2010; American Institute of Aeronautics and Astronautics: Nashville, TN, 2010; pp 115. (3) Bruno, T. J.; Smith, B. L. Improvements in the measurement of distillation curves - part 2: application to aerospace/aviation fuels RP-1 and S-8. Ind. Eng. Chem. Res. 2006, 45, 4381–4388. (4) Bruno, T. J., Huber, M. L., Laesecke, A, Lemmon, E. W., Perkins, R. A. Thermochemical and Thermophysical Properties of JP-10; NIST-IR 6640; National Institute of Standards and Technology: Boulder, CO, 2006. (5) Bruno, T. J. Thermodynamic, transport and chemical properties of “reference” JP-8. In Book of Abstracts, Army Research Office and Air Force Office of Scientific Research, 2006 Contractor’s meeting on Chemical Propulsion, 2006; pp 1518. (6) Bruno, T. J. The properties of S-8. In Final Report for MIPR F4FBEY6237G001; Air Force Research Laboratory, 2006. (7) Bruno, T. J., Laesecke, A., Outcalt, S. L., Seelig, H-D, Smith, B. L. Properties of a 50/50 Mixture of Jet-A þ S-8; NIST-IR-6647; National Institute of Standards and Technology: Boulder, CO, 2007. (8) Bruno, T. J. Thermodynamic, transport and chemical properties of “reference” JP-8. In Book of Abstracts, Army Research Office and Air Force Office of Scientific Research, 2007 Contractor’s meeting on Chemical Propulsion, 2007. (9) Bruno, T. J., Billingsley, M, Bates, R. D. Findings and Recommendations from the Joint NIST/AFRL Workshop on Rocket Propellants and Hypersonic Vehicle Fuels; National Institute of Standards and Technology: Boulder, CO, September 2008. (10) Bruno, T. J., Huber, M. L., Laesecke, A., Lemmon, E. W., McLinden, M. O., Outcalt, S. L., Perkins, R., Smith, B. L., Widegren, J. A. Thermodynamic, Transport, and Chemical Properties of “Reference” JP-8; NISTIR 6659; National Institute of Standards and Technology: Gaithersburg, MD, 2010. (11) Bruno, T. J.; Smith, B. L. Evaluation of the physicochemical authenticity of aviation kerosene surrogate mixtures. Part I: Analysis of volatility with the advanced distillation curve. Energy Fuels 2010, 24, 4266–4276. (12) Bruno, T. J.; Huber, M. L. Evaluation of the physicochemical authenticity of aviation kerosene surrogate mixtures. Part II: Analysis and prediction of thermophysical properties. Energy Fuels 2010, 24, 4277–4284. (13) Bruno, T. J.; Baibourine, E.; Lovestead, T. M. Comparison of synthetic isoparaffinic kerosene turbine fuels with the composition explicit distillation curve method. Energy Fuels 2010, 24, 3049–3059. (14) Huber, M. L.; Laesecke, A.; Perkins, R. A. Transport properties of dodecane. Energy Fuels 2004, 18, 968–975. (15) Huber, M. L.; Smith, B. L.; Ott, L. S.; Bruno, T. J. Surrogate Mixture Model for the Thermophysical Properties of Synthetic Aviation Fuel S-8: Explicit Application of the Advanced Distillation Curve. Energy Fuels 2008, 22, 1104–1114. (16) Huber, M. L.; Lemmon, E. W.; Diky, V.; Smith, B. L.; Bruno, T. J. Chemically authentic surrogate mixture model for the thermophysical properties of a coal-derived-liquid fuel. Energy Fuels 2008, 22, 3249–3257. (17) Huber, M. L.; Lemmon, E.; Bruno, T. J. Effect of RP-1 compositional variability on thermophysical properties. Energy Fuels 2009, 23, 5550–5555. (18) Huber, M. L.; Lemmon, E. W.; Bruno, T. J. Surrogate mixture models for the thermophysical properties of aviation fuel Jet-A. Energy Fuels 2010, 24, 3565–3571. (19) Lemmon, E. W.; Huber, M. L. Thermodynamic properties of n-dodecane. Energy Fuels 2004, 18, 960–967. (20) Lovestead, T. M.; Bruno, T. J. Comparison of the hypersonic vehicle fuel JP-7 to the rocket propellants RP-1 and RP-2 with the advanced distillation curve method. Energy Fuels 2009, 23 (7), 3637–3644. (21) Ott, L. S.; Hadler, A.; Bruno, T. J. Variability of the rocket propellants RP-1, RP-2, and TS-5: Application of a composition- and enthalpy-explicit distillation curve method. Ind. Eng. Chem. Res. 2008, 47 (23), 9225–9233. 2630
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