Showing papers on "Ullage published in 2005"

Oxygen sensor for aircraft fuel inerting systems

Abstract: An apparatus and method for monitoring oxygen concentrations in fuel tank ullage comprising providing a sensor head comprising an optical cavity, exposing the optical cavity to an ambient gaseous environment of a fuel tank or air separation module, via a laser light source emitting wavelength modulated light through the cavity, and receiving the wavelength modulated light with a detector.

Liquid measurement system having a plurality of differential pressure probes

Abstract: The weight of liquid in a tank subject to tilting is determined by measuring differences in air pressure in the ullage (the empty volume of the tank above the level of the liquid) and the air pressure produced by the weight of the liquid at the bottom of the tank. The pressures at the bottom of the tank are measured in a plurality of locations, and the differential pressures are combined to compensate for changes in the depth of the liquid when the tank is not level (e.g., when the tank is in an aircraft flying at an attitude other than straight and level). The electronics to measure the pressure and to process the pressure measurements are located remotely form the tanks, thus eliminating the possibility of ignition caused by the electronics when the liquid is fuel or other flammable liquid.

Modeling In-Flight Inert Gas Distribution in a 747 Center Wing Fuel Tank

Abstract: Extensive development and analysis has illustrated that fuel tank inerting, using air separation modules, is a reasonably cost-effective approach to preventing fuel tank explosions. To support the development of the Federal Aviation Administration inerting system, analytical and scale replica models of a Boeing 747 center wing fuel tank were developed and used to gage the ability of these relatively simple modeling methods to predict the ullage oxygen concentration of a specific fuel tank, given a flight cycle and inerting system performance. The analytical and scale models resulting average ullage oxygen concentration of the multiple bay fuel tank agreed well with measured flight test data, given the measured system performance and flight profile. Oxygen concentration distribution, in terms of the difference in oxygen concentration between the different bays of the test aircraft during the descent portion of the flight test, correlated well with the results obtained from both models, while model peak values deviated significantly from some of the measured flight test peak values. The resulting bay oxygen concentrations predicted by both models agreed with the flight test results within 1 percent oxygen on average, but the critical bay 1 (highest oxygen concentration bay) model values deviated by as much as 2 percent oxygen when compared with two separate tests. The computational model of a single flight test event illustrated fair agreement with the flight test data.

Multiphase Flow Separators in Reduced Gravity

Abstract: Gas phase and liquid phase separation is necessary for one of two reasons. First, system-critical components are designed to specifically operate in a single phase mode only. Pumps, especially centrifugal pumps, lose their prime when gas bubbles accumulate in the impellor housing. Turbines and compressors suffer from erosion problems when exposed to vapor laden with liquid droplets. The second reason is that system performance can be significantly enhanced by operating in a single phase mode. The condensation heat transfer coefficient can be enhanced when the liquid of an entering two-phase stream is stripped thus permitting initial direct contact of the vapor with the cold walls of the condenser. High efficiency and low mass Environmental Control and Life Support Systems invariably require multiphase processes. These systems consist of water filtration and purification via bioreactors that encounter two phase flow at the inlets from drainage streams associated with the humidity condensate, urine, food processing, and with ullage bubble effluent from storage tanks. Entrained gases in the liquid feed, could have deleterious effects on the performance of many of these systems by cavitating pumps and poisoning catalytic packed bed bioreactors. Phase separation is required in thermal management and power systems whereby it is necessary to have all vapor entering the turbine and all liquid exiting the condenser and entering the pump in order to obtain the highest reliability and performance of these systems. Power systems which utilize Proton Exchange Membrane Fuel Cells generate a humidified oxygen exit stream whereby the water vapor needs to be condensed and removed to insure reliable and efficient system operation. Gas-liquid separation can be achieved by a variety of means in low gravity. Several active and passive techniques are examined and evaluated. Ideally, a system that functions well in all gravity environments that the system experiences is a requirementCopyright © 2005 by ASME

Testing of a Spray-bar Thermodynamic Vent System in Liquid Nitrogen

Abstract: To support development of a microgravity pressure control capability for liquid oxygen, thermodynamic vent system (TVS) testing was conducted at Marshall Space Flight Center (MSFC) using liquid nitrogen (LN2) as a LOX simulant. The spray bar TVS hardware used was originally designed by the Boeing Company for testing in liquid hydrogen (LH2). With this concept, a small portion of the tank fluid is passed through a Joule-Thomson (J-T) device, and then through a longitudinal spray bar mixed-heat exchanger in order to cool the bulk fluid. To accommodate the larger mass flow rates associated with LN2, the TVS hardware was modified by replacing the recirculation pump with an LN2 compatible pump and replacing the J-T valve. The primary advantage of the spray-bar configuration is that tank pressure control can be achieved independent of liquid and vapor location, enhancing the applicability of ground test data to microgravity conditions. Performance testing revealed that the spray-bar TVS was effective in controlling tank pressure within a 6.89 kPa band for fill levels of 90%, 50%, and 25%. Tests were also conducted with gaseous helium (GHe) in the ullage. The TVS operated nominally with GHe in the ullage, with performance similar to the tests with gaseous nitrogen (GN2). Testing demonstrated that the spray-bar TVS design was flexible enough for use in two different propellants with minimal hardware modifications.

Experimental investigation into storage of confined cryogenic liquids without evaporation venting

Abstract: Publisher Summary This chapter presents a two-phase thermo-dynamical model to evaluate the heat transfer and pressurization of cryogenic liquids in a closed container, and programs were formulated to predict the effects of various factors on the cryogenic storage performance. Cryogenic liquids storage vessels are widely used in aerospace, transportation, and energy industries. Boil-off vapor is a great concern on cryogenic storage. It will concentrate in the vapor part of the inner tank, and will be eventually drained before causing tank overpressure. Substantial mass and cost savings could be achieved if evaporation venting can be avoided. Furthermore, inflammable, explosive or toxic liquids must be stored in a closed container without venting. The 2-phases thermodynamic model can be used to predict the storage duration of cryogenic liquids with a fair agreement. Test tank pressure and ullage is slight higher than predicted value. Confined liquid temperature is lower than its saturate temperature, and the liquid-vapor interface temperature is higher than that of other parts. Various factors affect the vent-less storage duration. The higher heating rate will cause shorter storage cycle. Vessel filled volume coefficient affects the storage duration of cryogenic tanks. For the experimental tank, its optimum Vessel filling volume coefficient is about 60%. Storage performance also varies with the properties of cryogenic liquids.

Liquid Nitrogen (Oxygen Simulant) Thermodynamic Vent System Test Data Analysis

Abstract: In designing systems for the long-term storage of cryogens in low-gravity (space) environments, one must consider the effects of thermal stratification on tank pressure that will occur due to environmental heat leaks. During low-gravity operations, a Thermodynamic Vent System (TVS) concept is expected to maintain tank pressure without propellant resettling. A series of TVS tests was conducted at NASA Marshall Space Flight Center (MSFC) using liquid nitrogen (LN2) as a liquid oxygen (LO2) simulant. The tests were performed at tank til1 levels of 90%, 50%, and 25%, and with a specified tank pressure control band. A transient one-dimensional TVS performance program is used to analyze and correlate the test data for all three fill levels. Predictions and comparisons of ullage pressure and temperature and bulk liquid saturation pressure and temperature with test data are presented.