Fuel Flow Topology and Control for Extending Aircraft Thermal Endurance

Abstract

The effect of fuel flow topology and control on the thermal endurance of aircraft that use fuel as a heat sink was explored. Differential equations were derived that describe the behavior of recirculated fuel flows within a proposed dual-tank topology that features a designated recirculation tank. Equations for single-tank flow topology are also presented. It is shown that a simple switching controller acting on a dual-tank system results in aircraft thermal endurance that is greater than or equal to that of a single-tank configuration when the aircraft engine and fuel system are driven at a constant mass flow rate. More sophisticated examples are considered for a fighter aircraft mission where the endurance achieved by both open- and closed-loop single-tank systems are compared to the endurance of a dual-tank system operating under closed-loop control. Simulation results are used to quantify benefits that can be obtained by a judicious selection of closed-loop control strategy and fuel flow topology. The results show that a controlled dual-tank fuel topology can increase aircraft thermal endurance over that which can be attained by a single-tank fuel flow topology.