Showing papers on "Ullage published in 2000"

Vapor recovery system for fuel storage tank

Abstract: A vapor recovery system for a fuel storage tank. The system includes a pair of VOC adsorbent canisters that alternately recover VOC vapors from the fuel tank ullage or are regenerated. Regeneration of the VOC adsorbent canisters is provided by exhausting the VOC vapors from the VOC canisters using a vacuum pump and back into the fuel tank ullage. When the operating pressure of the fuel tank ullage is elevated, an auxiliary VOC adsorbent canister is operated in parallel with the pair of canisters in order to recover the increased amount of VOC vapors in the tank ullage.

Method and system for controlling the supply of nitrogen to electrical power handling equipment

Abstract: A system that controls nitrogen pressure in the ullage of a power transformer that has its windings submerged in oil. The pressure is controlled in a narrow range of approximately 0.5 psi to approximately 2.0 psi. A nitrogen generator supplies the nitrogen to a reservoir from which it is distributed to the ullage as well as to accessories such as a load tap changer or a control box. A temperature regulator is provided for substation installations that are located in climates with wide ambient temperature variations to control the pressure of the generated nitrogen in an acceptable range.

Pressur1zation analysis of cryogenic propulsion systems

Abstract: The pressurization behavior of a cryogenic hydrogen tank was analyzed using computational fluid dynamics (CFD). The analysis examined the gas-phase thermodynamics of the propellant tank during the prepressurization phase using noncondensable helium, and autogenous pressurization using hydrogen gas during engine operation. The primary purpose of the analysis was to predict the ullage pressure behavior and the amount of pressurization gas necessary to maintain the ullage pressure within the specified band. Results from the analysis were compared to test data obtained at the NASA Lewis Plum Brook Propulsion Research Facility in 1998 for a Boeing Delta III hydrogen-oxygen upper stage vehicle designated as the X-Stage. The model predictions were shown to be in good agreement with the available test data.

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.

The Cost of Implementing Ground- Based Fuel Tank Inerting in the Commercial Fleet

Abstract: : This report documents a cost analysis of ground-based fuel tank inerting for the commercial fleet performed by a group of industry experts lead by an Federal Aviation Administration (FAA) representative. Ground-based inerting (GBI) consists of displacing most of the oxygen dissolved in the fuel with nitrogen by a process called fuel scrubbing, and displacing the air in the empty space (ullage) of the fuel tank, with nitrogen-enriched air (NEA) in a process called ullage washing. The cost analysis considers the cost of implementing and performing GBI for all US departures carrying more than 19 passengers. The cost of GBI for only departures of airplanes with heated center wing tanks (HCWTs) was also determined. Airplanes that have the air conditioning equipment, or packs, located below the center wing fuel tanks are considered to have heated center wing tanks. This analysis considered all nonrecurring and recurring costs of GBI at all major U.S. airports over 10 years, with a 3-year start-up period. The cost of modifying the aircraft to allow for GBI was not considered in this analysis.

Cryogenic Fuel Tank Draining Analysis Model

Abstract: One of the technological challenges in designing advanced hypersonic aircraft and the next generation of spacecraft is developing reusable flight-weight cryogenic fuel tanks. As an aid in the design and analysis of these cryogenic tanks, a computational fluid dynamics (CFD) model has been developed specifically for the analysis of flow in a cryogenic fuel tank. This model employs the full set of Navier-Stokes equations, except that viscous dissipation is neglected in the energy equation. An explicit finite difference technique in two-dimensional generalized coordinates, approximated to second-order accuracy in both space and time is used. The stiffness resulting from the low Mach number is resolved by using artificial compressibility. The model simulates the transient, two-dimensional draining of a fuel tank cross section. To calculate the slosh wave dynamics the interface between the ullage gas and liquid fuel is modeled as a free surface. Then, experimental data for free convection inside a horizontal cylinder are compared with model results. Finally, cryogenic tank draining calculations are performed with three different wall heat fluxes to demonstrate the effect of wall heat flux on the internal tank flow field.

Hybrid thermal control testing of a cryogenic propellant tank

Abstract: This report presents the experimental results of a hybrid thermal control system, one that integrates a passive system (multi-layer insulation) with an active system (a mechanical cyrocooler) applied to cryogenic propellant storage. These experiments were performed on a 1.39 m diameter spherical propellant tank filled with LH2 while installed in an evacuated chamber. The tank heat transfer to the cryocooler was accomplished with a condenser installed in the ullage of the tank and mated to the second stage of the cooler, and by conduction, through copper leaves mated to the first stage of the cooler. The first hybrid system test was performed with both the condenser and the leaves, a configuration that had excess capacity to remove the heat entering the tank; the second test was performed with only the condenser, with a capacity closely matched to the tank heating rate. In both of these tests, the goal of zero boil-off was achieved.

Transient Analysis of Pressurization and Pneumatic Subsystems of the X-34 Main Propulsion System

Abstract: Transient models for the pressurization, vent/relief, and pneumatic subsystems of the X-34 Main Propulsion System are presented and simulation of their operation within prescribed requirements are provided. First, using ROCket Engine Transient Simulation (ROCETS) program, pressurization subsystem operation was simulated and helium requirements and the ullage thermodynamic condition within each propellant tank were calculated. Then, Overpressurization scenarios of propellant tanks and the response of vent/relief valves were evaluated using ROCETS simulation of simultaneous operation of the pressurization and vent/relief subsystems by incorporating the valves data into the model. Finally, the ROCETS simulation of in-flight operation of pneumatic subsystem predicted the overall helium consumption, Inter-Propellant Seal (IPS) purge flowrate and thermodynamic conditions, and Spin Start power.

Air separation module using high speed starting valve for high-speed warming up penetrating membrane air separation module

Abstract: PROBLEM TO BE SOLVED: To heighten the efficiency of a high-speed warming up system of an inert gas generating system in an aircraft. SOLUTION: This system is equipped with an air separation module including a separation mode having an inlet, an outlet, an exist port, and an entry port, the inlet being connected to a hot air source and formed by hollow fibers for supplying inert gas to a fuel tank, a valve connected to the above entry port and connected to at least one of the exit port and the hot air source, and a monitor for checking an operating parameter of the module to be reported to a computer. A method for high speed warming up the system comprises a first introduction of letting hot air flow into the module to separate nitrogen gas, and feeding some of the separated nitrogen gas into an ullage space of a fuel tank, and a second introduction of returning some of separated nitrogen gas into the module. COPYRIGHT: (C)2001,JPO