Extent and Impacts of Hydrocarbon Fuel Compositional Variability for Aerospace Propulsion Systems

The thermal decomposition kinetics of JP-7, JP-TS and JP-900 were studied, motivated by the need of the hypersonic vehicle community for a fuel that has a high degree of thermal stability. Decomposition reactions were performed at 375, 400, 425 and 450 °C in stainless-steel ampule reactors. In all cases, the pressure before decomposition was 34.5 MPa (5000 psi). Decomposition as a function of time at each temperature was quantified by analyzing the thermally stressed liquid phase using gas chromatography. These results were used to determine global first-order rate constants that approximate the overall decomposition rate of of each fuel. For JP-7, these first-order rate constants ranged from 1.79 × 10 −5 s −1 at 375 °C to 3.02 × 10 −4 s −1 at 450 °C. For JP-TS, the rate constants had values between 1.74 × 10 −5 s −1 at 375 °C to 2.70 × 10 −4 s −1 at 450 °C. For JP-900, the rate constants ranged from 1.03 × 10 −5 s −1 at 375 °C to 3.60 × 10 −4 s −1 at 450 °C. At all temperatures studied, these three fuels have similar rate constants for thermal decomposition; with only one exception, the values of k′ are identical within the combined uncertainty. The rate constants for the decomposition of RP-2, a fuel being considered as a replacement fuel for hypersonic vehicles, are similar in the temperature range studied. Considering the time needed for 1% of the sample to decompose (t 0.01 ), we find that required instrument residence times range from 16 min at 375 °C to 30 s at 450 °C. The rate constants measured here, as well as the Arrhenius parameters that we calculate, can be used to design and plan physical property measurements at additional temperatures.

Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermal Decomposition Kinetics of the Thermally Stable Jet Fuels JP-7, JP-TS and JP-900

Gough¹,

Widegren²,

Bruno³

2014

“…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. − 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.…”

Section: Introductionmentioning

confidence: 99%

Assessment of the Composition and Distillation Properties of Thermally Stressed RP-1 and RP-2: Application to Fuel Regenerative Cooling

Windom

Bruno

2011

In this work, we measured the volatility of thermally stressed samples of RP-1 and RP-2 rocket propellant kerosenes by use of the advanced distillation curve method. This work is part of a large program at NIST and other laboratories geared toward improving the operability of the hydrocarbon component of liquid fuel packages. Measuring the properties of thermally stressed rocket propellant kerosene is a necessary component of this overall effort. This is motivated by the use of the kerosene as a coolant before combustion in the engine. Samples of RP-1 and RP-2 were stressed at 475 and 510 °C, at a pressure of 17 kPa (2500 psi), for residence times of 0.5 min. Volatility measurements revealed significant changes early in the distillation curves, becoming very pronounced at the higher temperature. The volatility measurements were supplemented with chemical analyses and a calculation of the enthalpy of combustion as a function of distillate volume fraction. We note that the increase in volatility is explained by the significant increase of very light (lower molecular mass) components produced during the thermal stress. We also note that the enthalpy of combustion follows the same pattern as the volatility, as we have noted in previous studies.

“…Another avenue that may yield additional improvement in the thermal stability of RP-2 is to change the overall chemical composition of the fuel. This is possible because RP-2 is blended from various refinery streams or feedstocks to meet specification requirements. − Therefore, in principle, it is possible to change the relative concentrations of various classes of hydrocarbons in the fuel. For example, it should be possible to increase (or decrease) the concentrations of linear alkanes, branched alkanes, or cyclic alkanes.…”

Section: Introductionmentioning

confidence: 99%

Thermal Stability of RP-2 as a Function of Composition: The Effect of Linear, Branched, and Cyclic Alkanes

Widegren

Bruno

2013

The objective of this work was to identify compositional changes that could improve the thermal stability of the kerosene rocket propellant known as RP-2. For this study, we probed the effect of different types of alkanes on the thermal stability of RP-2. The proportion of linear, branched, or cyclic alkanes was increased by mixing RP-2 with one of the following alkanes (25% by mass): n-dodecane, n-tetradecane, 4-methyldodecane, 2,6,10-trimethyldodecane, or 1,3,5-triisopropylcyclohexane. These mixtures were thermally stressed in stainless steel ampule reactors at 673 K (400 °C, 752 °F) for up to 4 h. After each reaction, the stressed fuel was analyzed by gas chromatography with flame ionization detection. The decomposition kinetics of each added alkane was determined from the decrease in its chromatographic peak. The overall decomposition kinetics of each fuel mixture was determined from the increase in a suite of chromatographic peaks that correspond to light decomposition products. These data are compared to similar data for neat RP-2.