Temperature Rise Study on Aircraft Engine Fluid Distribution Tubes Subjected to Oil Burner

Abstract

There are lots of tubes in aircraft engine nacelle to transfer different kinds of fluid to other parts of the aircraft. These tubes is required to be tested by standard oil burner, which provides an environment of temperature about 2000 °F and heat flux about 11.9 W/m. The purpose of this paper is to achieve a better understanding of the heat transfer process of tube fire test and make prediction on the temperature rise before samples were subjected to the test facility. The flow rate was studied by both theoretical and experimental method to determine its influence on temperature rise. Also, temperature rise of Jet A-1 fuel and lubricant RIPP 4050, which have different fluid characteristics, was used for comparison of the model. The result shows a good compliance between theoretical value and experimental measurements. Introduction Tubes are widely used in aircraft engine nacelles, distributing fuel, lubricant and hydraulic oil to other parts of the aircraft. As the space around engine is a most hazardous zone because of its high temperature and strong vibration, these hose assembly that carries flammable fluid is required to withstand the fire resistance test by airworthiness regulations. Tubes and connectors, no matter whether it’s made of metallic or non-metallic material, is required to be subjected to a standard kerosene flame by certain paragraphs of CCAR23.1183, CCAR 25.1183 and CCAR27.1183. As the type of carrying fluid differs, the flow rate in tubes varies greatly. Fuel distribution tube of some large transportation category aircraft may have a flow rate up to tens of thousands of liters per hour, while flow rate of hydraulic oil tube of some little aircraft may be 100 liters per hour or even lower. Because fluid acts as the temperature reducer for tubes, low flow rate is utilized in fire resistance test to represent the harshest condition for conservative considerations. Theoretical Analysis As the oil flows steadily and continuously within the tube by oil pump, the flow could be seen as a well-developed flow and the distribution of temperature field depends on whether the flow is turbulent or laminal. The Renault number, ReD, is determined by Eq. 1, ReD ≡ ρumD μ = 4?̇? πDρν = 4?̇? πDν , (1) Where ρ is the density of the fluid umis the average velocity of flow μ is the kinetic viscosity of fluid ν is the dynamic viscosity of fluid D is the inner diameter of the tube ?̇? is the mass flow rate The flow rates in this paper range from 50L/h to 200L/h, put the characteristics of fuel and hydraulic oil into calculation, the Renault numbers of both fluids are not greater than 2000, while the