Some notes on fuel boiling losses and fuel-tank pressurisation in a long-range supersonic aircraft

Abstract

A method of calculating the fuel boiling losses, due to aerodynamic heating, from a supersonic aircraft with integral wing fuel tanks is devised and is applied to the Concord, assuming flight conditions of Mach 2.2 at 64000 ft altitude using low boiling point kerosene fuel. It is shown that if the specified tank pump performance is achieved the quantity of fuel evaporated is no more than 150 lb if the tanks are unpressurised, and is negligible in the present design case where the tanks are pressurised. to 2.2 psia. The calculations are based on certain assumptions defined in the text concerning fuel distillation characteristics, heat transfer data and boiling fuel distribution in the tankage. Because much of the evaporated fuel may condense in the vent system and be recovered it is likely that the fuel loss through boiling in unpressurised tanks will be less than the weight of additional equipment required to pressurise the tanks. Since the fuel transfer pump duty is very arduous, the feasibility of operating without tank pressurisation depends on the actual pump performance achieved. Suggestions are made for reducing the severity of the conditions affecting fuel thermal stability by modified fuel handling procedures in the aircraft. Note (added April 1968) The Concord performance specifications and fuel system design have been changed since this Report was issued originally and the numerical values quoted for fuel losses, based as they are on the data available in 1967, are no longer applicable to the actual aircraft.