Research On Thermal Protection Of Aero-engine Fuel Supply Line

For modern aero-engine, fuel is usually used for cooling other subsystem in the aircraft, which makes its temperature up to 100~140℃ when arriving at the nozzle. Besides, with the constantly development of aero-engine, the temperature of the diffuser outlet airflow is rising as a result more serious kerosene heating in the pipeline appears. It in turn makes fuel coke and even endangers the proper operations of the engine. Thus, it’s full of significance to conduct systematic studies on the thermal protection of engine fuel line. This paper, on the background of thermal protection of aero-engine fuel line, is mainly for numerical simulations and experimental researches on the simplified model of fuel pipeline with or without thermal protection. Two protection measures, wrapping insulation material around pipe and setting heat shield outside the tube, are used. Temperature variations in different conditions and their impacts on thermal protection as well as comparisons of different thermal protective means are analyzed. The study will provide technical supports for engine fuel line heat protection design.Firstly, the techniques of numerical simulation are presented in the paper. And the numerical simulations of the single fuel pipeline and the simplified fuel line without thermal protection are conducted. The results show that the fuel temperature increases with the rise of residence time and if there are no effective thermal protection measures, the pipe wall temperature will be higher than design value and coke will be found inside the pipeline.Then, numerical simulation studies on the thermal protective measures of wrapping insulation material around pipe and setting heat shield outside the tube are carried out. The influences of the parameters such as fuel velocityfv, fuel temperaturefT, hot air flow velocityav, hot air temperatureaT, kerosene tube diameterfD and insulating layer thickness h on the fuel pipe wall maximum temperaturewi. maxT, fule temperature rise DT, inner wall surface heat flux density q and heat flux Q are analyzed. It’s found that fuel velocity, fuel inlet temperature, hot air temperature and insulating layer thickness greatly affect the heat insulation effect, whereas kerosene tube diameter and hot air flow velocity have minor impact on that. Kerosene tube wall temperature and the temperature difference between inlet and outlet of the tube reduce with an increase in kerosene velocity and increase with increasing the hot air temperature. The increasing of fuel inlet temperature makes a small temperature difference between inlet and outlet of the fuel tube in case of low velocity of fuel, however the phenomenon is not so obvious in high fuel flow velocity. For a constant thickness of insulation layer, the heat insulation effect of air heat shield is better than that of thermal insulation material.Finally, experimental studies on thermal protective measures are conducted. The regularity of temperature rise in the fuel line under the experimental conditions is obtained. The characteristics of different thermal protection measures are analyzed. The studies show the numerical and experimental results show the same regular pattern under the experimental conditions. The thermal protection effect of insulation materials sorted from best to worst is that: aluminum silicate fiber fabrics, high silica glass fiber fabrics and basalt fiber fabrics. These three materials make wall temperature lower than the design value. For the heat shield, the heat insulation effect is inferior to that of thermal insulation material with the same layer thickness, when the air layer is thin, whereas heat insulation effect is greatly improved and better than that of fiber insulation layer with the same thickness when the air insulating layer thickness is up to 1.5mm.