Ullage

About: Ullage is a research topic. Over the lifetime, 501 publications have been published within this topic receiving 4704 citations. The topic is also known as: headspace.

Review of technologies for active suppression for fuel tank explosions

Abstract: Historically, fuel fire and explosion is a major cause of aircraft losses in combat. Data from Southeast Asia showed that over half of the aircraft combat losses involved fuel fire and explosions. To increase survivability, various techniques have been implemented to reduce the vulnerability of the aircraft’s fuel system. Ullage (the vapor space above the fuel level in a fuel tank) in aircraft fuel tanks can have a potentially explosive fuel-air mixture. Fuel tank explosions are a result of ullage deflagrations where the combustion overpressure generated exceeds the structural strength of the tank. Initially, large-scale use of passive protection systems was first developed based on reticulated foams. These systems imposed penalties on the fuel systems, since they displaced and retained fuel and sometimes had a finite limit on installed service life. To eliminate such penalties, the use of active systems was pursued, notably Halon 1301 inerting of the F-16 fuel tanks and nitrogen inerting in the C-5. However, these systems also had their own set of penalties. As a result, reactive systems were investigated.

Analytic Solution for the Phase Change in a Suddenly Pressurized Liquid-Vapor System

Abstract: To prevent boil-off of a cryogenic liquid in a nonperfectly insulated container, it is necessary to pressurize the ullage region. This is most conveniently accomplished by introducing a small quantity of gas at an elevated temperature. The amount of pressurizing gas required is inversely proportional to the temperature at which it enters the tank, since the pressurization requirement manifests itself as an energy requirement. The introduction of pressurant has two effects on the liquid-vapor system: it raises the interface temperature to the saturation temperature corresponding to the elevated ullage pressure, and it increases the vapor temperature. The liquid-vapor system, if isolated, will adjust to this nonequilibrium condition by transferring thermal energy from the vapor to the liquid. However, unlike two solids at different temperatures in thermal contact, the controlling temperature difference is not governed by the initial liquid and vapor temperatures alone. It is the interface temperature that controls the net heat flow into the liquid or vapor. Any imbalance of heat flow across the liquid-vapor interface is accounted for by a phase change, i.e., by energy being released at the interface by condensation or absorbed by evaporation.

System and methods for ullage space fuel level estimation

Abstract: A method for a vehicle, comprising: indicating a true fill level of a fuel tank based on a fuel vapor canister temperature profile during a refueling event. In this way, a quantity fuel dispensed over the maximum fill level of the fuel tank may be accounted for, regardless of the fuel level sensor reading.