Preliminary Surrogate Mixture Models for the Thermophysical Properties of Rocket Propellants RP-1 and RP-2 M. L. Huber, E. W. Lemmon, L. S. Ott, † and T. J. Bruno* Thermophysical Properties DiVision National Institute of Standards and Technology Boulder, Colorado 80305 ReceiVed March 11, 2009. ReVised Manuscript ReceiVed April 27, 2009 We have developed surrogate mixture models to represent the thermophysical properties of two kerosene rocket propellants, RP-1 and RP-2. The surrogates were developed with a procedure that incorporated experimental data for the density, sound speed, viscosity, thermal conductivity, and the advanced distillation curves for samples of the two fuels. The surrogate for RP-1 contains four components (R-methyldecalin, n-dodecane, 5-methylnonane, and heptylcyclohexane), and the surrogate for RP-2 contains five components (R-methyldecalin, n-dodecane, 5-methylnonane, 2,4-dimethylnonane, and heptylcyclohexane). Comparisons with experimental data demonstrate that the models are able to represent the density, sound speed, viscosity, and thermal conductivity of both fuels to within (at a 95% confidence level) 0.4, 2, 2, and 4%, respectively. The volatility behavior, as measured by the advanced distillation curves, is reproduced to within 0.5%. Introduction There has been a great deal of interest in recent years on the part of both NASA and the United States Air Force in developing new aerospace fuels, and in the reformulation of existing fuels. One such fuel is Rocket Propellant 1 (RP-1, MIL- P-25576C with amendment 2). 1 This fuel belongs to the general class of hydrocarbon fuels called “kerosenes,” and has been used with liquid oxygen as the oxidizer on vehicles such as the Saturn V launch vehicle (first-stage booster engine), 2 and more modern engines. Recent interest in developing the capability to reuse rocket motors multiple times (rather than a single time) has led to the reformulation of hydrocarbon fuels such as RP-1 to decrease the level of sulfur compounds, aromatics, and alkenes in the fuel. Three grades of RP-1 were specified with an eye toward decreasing the sulfur concentration specification: TS- 30 (total sulfur less than 30 ppm, mass/mass, which was similar to typical as-delivered RP-1), TS-5 (total sulfur less than 5 ppm, mass/mass) and UL RP-1 (ultralow sulfur, less than 100 ppb, mass/mass). Experience showed that ultralow sulfur RP-1 showed significant performance benefits over TS-5 with only marginally greater costs, so this fluid (ultralow) was selected to become ”RP-2” (and the RP-1 sulfur limit was lowered from 500 to 30 ppm, mass/mass). Thus, RP-1 and RP-2 3 have emerged as the primary kerosene rocket propellants for use in United States rocket motors. We note that the specification for RP-1 and RP-2 aromatic content are the same, however one commonly finds a lower aromatic content in RP-2. Other specifications, including those related to the distillation behavior, viscosity, density, freezing point, and net heat of combustion are identical for RP-1 and RP-2. 3 The focus of this work is the modeling of thermophysical properties of RP-1 and RP-2. These fuels are complex mixtures of hundreds of components, and modeling each individual constituent is not feasible. Instead, we use the concept of a surrogate mixture. The general principle is to use a mixture of a relatively small number of components (usually less than 20) to represent the behavior of the actual complex fuel. Edwards and Maurice 4 reviewed some of the surrogates available for aviation and rocket fuels and provided an overview of the general requirements and expectations of fuel surrogates. There currently are active working groups for developing experimental databases and surrogate models for the kinetics of jet, diesel, and gasoline fuels, 5-7 and various groups have proposed and studied surrogate fuel mixtures for gasoline, diesel fuel, and aviation turbine fuel. 8-18 Only two published surrogate mixtures * To whom correspondence should be addressed. E-mail: bruno@ boulder.nist.gov. † Present address: Chemistry and Biochemistry Department, California State University, Chico, CA. (1) Military Specification MIL-P-25576C; 1967. (2) Edwards, T. J. Propul. Power 2003, 19, 1089–1107. (3) Military Specification MIL-DTL-25576E; 2006. (4) Edwards, T.; Maurice, L. Q. J. Propul. Power 2001, 17, 461–466. (5) Colket, M.; Edwards, T.; Williams, S.; Cernansky, N. P.; Miller, D. L.; Egolfopoulos, F.; Lindstedt, P.; Seshadri, K.; Dryer, F. L.; Law, C. K.; Friend, D. G.; Lenhert, D. B.; Pitsch, H.; Sarofim, A.; Smooke, M.; Tsang, W., Development of an Experimental Database and Kinetic Models for Surrogate JetFuels. In AIAA Annual Conference [AIAA 2007-770], Reno, NV, 2007. (6) Farrell, J. T.; Cernansky, N. P.; Dryer, F. L.; Friend, D. G.; Hergart, C. A.; Law, C. K.; McDavid, R. M.; Mueller, C. J.; Patel, A. K.; Pitsch, H. In DeVelopment of an Experimental Database and Kinetic Models for Surrogate Diesel Fuels, [SAE-01-0201]; 2007. (7) Pitz, W. J.; Cernansky, N. P.; Dryer, F. L.; Egolfopoulos, F. N.; Farrell, J. T.; Friend, D. G.; Pitsch, H. In DeVelopment of an Experimental Database and Chemical Kinetic Models for Surrogate Gasoline Fuels, [SAE 2007-01-0175]; 2007. (8) Wood, C. P. The DeVelopment and Application of Surrogate Blends in Simulating the Combustion Performance of Distillate AViation Fuels; MS Thesis, University of California: Irvine, CA, 1989. (9) Wood, C. P.; McDonnell, V. G.; Smith, R. A.; Samuelsen, G. S. J. Propul. Power 1989, 5, 399–405. (10) Patterson, P. M.; Kyne, A. G.; Pourkashanian, M.; Williams, A. J. Propul. Power 2000, 16, 453–460. (11) Dagaut, P.; Reuillon, M.; Boettner, J.; Cathonnet, M. Proc. Combust. Inst. 1994, 25, 919–926. (12) Dean, A. J.; Penyazkov, O. G.; Sevruk, K. L.; Varatharajan, B. Proc. Combust. Inst. 2007, 31, 2481–2488. (13) Moss, J. B.; Aksit, I. M. Proc. Combust. Inst. 2007, 31, 3139– 3146. Energy & Fuels 2009, 23, 3083–3088 3083 10.1021/ef900216z This article not subject to U.S. Copyright. Published 2009 by the American Chemical Society Published on Web 05/19/2009 Downloaded by NOAA LIB BOULDER on July 8, 2009 Published on May 19, 2009 on http://pubs.acs.org | doi: 10.1021/ef900216z