Study on RP-3 Aviation Fuel Vapor Concentration

Abstract

Fuel vapor concentration is a key parameter for assessing the flammability of aircraft fuel tanks. However, the current research on RP-3 (Rocket Propellant-3) fuel vapor concentration is inadequate. This study categorizes fuel components by the number of carbon atoms and utilizes Raoult’s law to estimate the gas–liquid equilibrium relationship of each constituent element under equilibrium conditions. The equilibrium-state model is experimentally validated, and the differences in the constituents and fuel vapor concentrations of RP-3 and Jet-A (Jet Fuel-A) fuels are analyzed. In addition, an empirical correlation between the overall hydrocarbon concentration of RP-3 fuel vapor and the temperature and pressure in the equilibrium state is established, providing a theoretical basis for determining RP-3 fuel vapor concentration in related investigations. Furthermore, a transient prediction model of fuel vapor concentration is developed using the lumped parameter approach that considers the heat exchange among the fuel, gas, wall, and environment. The model’s accuracy is confirmed by comparing it to existing literature. Then, the temperature and fuel vapor concentration variation patterns in the fuel tank are calculated and evaluated under two typical flight scenarios. The results show a significant difference between the calculated fuel vapor concentration values obtained through equilibrium-state and transient models. Therefore, in the design of fuel vapor catalytic inerting systems, it is crucial to consider both the equilibrium and transient fuel vapor concentration values rather than relying solely on the former. Throughout the flight envelope, gas phase and fuel phase temperatures in RP-3, Jet-A, and C10H22 fuel tanks exhibit minimal differences. However, significant variations in fuel vapor concentration exist depending on the flight state and envelope. Hence, regarding RP-3 as equivalent to C10H22 is inappropriate. Additionally, fuel vapor concentration is a more suitable metric than fuel temperature for assessing fuel tank flammability.

Sustainable Aviation Fuels for Clean Skies: Exploring the Potential and Perspectives of Strained Hydrocarbons

“…The previous sections delved into the primary properties of aviation fuel, recognizing its complexity as a hydrocarbon blended with diverse characteristics. In addition to those discussed, other properties including vapor pressure, corrosiveness, water content, and surface tension play significant roles in aviation fuel quality control. , Vapor pressure gauges the fuel’s inclination to evaporate and form vapors at a specific temperature, mainly influenced by the presence of volatile compounds. , Maintaining the proper vapor pressure is essential to prevent vapor lock and ensure consistent fuel flow, especially during altitude changes and temperature variations. In aviation, the Reid vapor pressure (RVP) serves as a key indicator of the fuel’s volatility, measured through standardized methods.…”

“…37,39 Vapor pressure gauges the fuel's inclination to evaporate and form vapors at a specific temperature, mainly influenced by the presence of volatile compounds. 61,62 Maintaining the proper vapor pressure is essential to prevent vapor lock and ensure consistent fuel flow, especially during altitude changes and temperature variations. In aviation, the Reid vapor pressure (RVP) serves as a key indicator of the fuel's volatility, measured through standardized methods.…”