Abstract

Gravity feed is one fuel supply way for aeroplane and the simulation of it is very important. The traditional method to calculate the gravity feed is to assume that only one tank in fuel system supplies the needed fuel to the engine, and then calculated for the single branch. Actually, all fuel tanks compete for supplying fuel and the key problem for gravity feed calculation is to simulate the multiple-branch and transient process. The present paper gives the mathematical model for fuel flow pipe, pump, check valve and the simulation model for fuel tank at first, and then presented a new calculation model for gravity feed fuel of aeroplane fuel system based on the flow network theory and time difference method. The model takes into consideration all fuel tanks and can solve the multiple-branch and transient process of gravity feed. Finally, the thesis gives a numerical example for a certain type of aircraft, achieved the variations of fuel level and flow mass per second of each fuel tanks, the variations of the fuel pressure at the engine inlet, and predicted the maximum time that the aeroplane could fly safely under gravity feed. The numerical example indicts that the method proposed here is intrinsically superior to the traditional methods and is closer to understanding the real seriousness of the fuel supply situation.

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