Showing papers on "Ullage published in 2010"

System and method for scavenging ullage from center wing tanks in an airplane

Abstract: A system for reducing reactive components in ullage of a fuel tank, typically the fuel tank of an airplane. The system includes an air driven unit for creating a fluidic motive force to remove ullage from the fuel tank, and a main catalytic unit for receiving the ullage and reducing the reactive components to yield processed ullage for return to the fuel tank.

CFD Fuel Slosh Modeling of Fluid-Structure Interaction in Spacecraft Propellant Tanks with Diaphragms

Abstract: Liquid sloshing within spacecraft propellant tanks causes rapid energy dissipation at resonant modes, which can result in attitude destabilization of the vehicle. Identifying resonant slosh modes currently requires experimental testing and mechanical pendulum analogs to characterize the slosh dynamics. Computational Fluid Dynamics (CFD) techniques have recently been validated as an effective tool for simulating fuel slosh within free-surface propellant tanks. Propellant tanks often incorporate an internal flexible diaphragm to separate ullage and propellant which increases modeling complexity. A coupled fluid-structure CFD model is required to capture the damping effects of a flexible diaphragm on the propellant. ANSYS multidisciplinary engineering software employs a coupled solver for analyzing two-way Fluid Structure Interaction (FSI) cases such as the diaphragm propellant tank system. Slosh models generated by ANSYS software are validated by experimental lateral slosh test results. Accurate data correlation would produce an innovative technique for modeling fuel slosh within diaphragm tanks and provide an accurate and efficient tool for identifying resonant modes and the slosh dynamic response.

Drop Tower Experiments on Non-isothermal Reorientation of Cryogenic Liquids

Abstract: Capillary driven surface oscillations of liquid argon (Tsat = 87.3 K at 1,013 hPa) have been investigated in a partly filled right circular cylinder under non-isothermal boundary conditions. The oscillations take place during the reorientation from the normal gravity surface position towards a new position upon step reduction of gravity. The situation is similar to the end of thrust in a rocket tank when the cold propellant moves along the warmer tank wall driven by capillary forces. The aim was to investigate the influence of the temperature difference between the slightly subcooled cryogenic liquid and the superheated cylinder wall on the oscillations and their characteristics in a single-component, two-phase system. Axial wall temperature gradients of averaged 0.15 K/mm − 1.93 K/mm above the normal gravity surface position were implemented. A general dependence of the reorientation behavior on the gradient value was observed, concerning the apparent contact line behavior, the frequency and damping of the oscillations of the free surface center point, and the apparent contact angle. The behavior of the ullage pressure was found to follow the behavior of the contact line.

Progress in Modeling Pressurization in Propellant Tanks

Abstract: Summary The pressure of propellant and oxidizer tanks has to be maintained within a narrow margin and is critical to the proper functioning of the liquid propulsion system. Several control mechanisms such as venting and spray bars are specifically deployed in the tankage to ensure that the pressure in the tank is restricted to the design margins. In this paper a suite of predictive tools have been developed that can aid in the design and management of propellant tanks. The analysis tools comprise of a multi-node lumped parameter code, a multi-phase CFD code, and a hybrid procedure that utilizes CFD in conjunction with a lumped parameter based internal boundary between the ullage and the liquid. Each tool is specifically tailored towards a certain class of tank pressurization problems: for example the multi-node lumped parameter approach is particularly suited for long duration space tank applications, while the CFD approach is applicable to short duration injection based pressurization problems where mixing is the dominant physical mechanism. In long duration cases, where injection or venting based control systems can significantly alter the flow in the tank the hybrid approach is more appealing. A series of test cases from different regimes of tank pressurization were considered in this paper with the three approaches. The first simulation was based on the Saturn AS-203 self-pressurization fuel tank experiment in a low gravity environment. The complete duration of the test was analyzed with the multi-node lumped parameter code with average heat loads through the tank walls and the

A History of Collapse Factor Modeling and Empirical Data for Cryogenic Propellant Tanks

Abstract: One of the major technical problems associated with cryogenic liquid propellant systems used to supply rocket engines and their subassemblies and components is the phenomenon of propellant tank pressurant and ullage gas collapse. This collapse is mainly caused by heat transfer from ullage gas to tank walls and interfacing propellant, which are both at temperatures well below those of this gas. Mass transfer between ullage gas and cryogenic propellant can also occur and have minor to significant secondary effects that can increase or decrease ullage gas collapse. Pressurant gas is supplied into cryogenic propellant tanks in order to initially pressurize these tanks and then maintain required pressures as propellant is expelled from these tanks. The net effect of pressurant and ullage gas collapse is increased total mass and mass flow rate requirements of pressurant gases. For flight vehicles this leads to significant and undesirable weight penalties. For rocket engine component and subassembly ground test facilities this results in significantly increased facility hardware, construction, and operational costs. "Collapse Factor" is a parameter used to quantify the pressurant and ullage gas collapse. Accurate prediction of collapse factors, through analytical methods and modeling tools, and collection and evaluation of collapse factor data has evolved over the years since the start of space exploration programs in the 1950 s. Through the years, numerous documents have been published to preserve results of studies associated with the collapse factor phenomenon. This paper presents a summary and selected details of prior literature that document the aforementioned studies. Additionally other literature that present studies and results of heat and mass transfer processes, related to or providing important insights or analytical methods for the studies of collapse factor, are presented.

Modelling, simulation, and optimization of a hot pressurization system for a liquid propellant space engine and comparison with experimental results

Abstract: The main objective of this paper is to optimize the performance of a gas generator (GGO) in order to reduce propellant consumption, flyweight, and contamination. Hence, the periodic operation of a GGO is offered. For this purpose, a non-linear modelling and dynamic simulation of a hot pressurization system is developed in order to predict the history of pressure, temperature, and mass flowrate of pressurant and propellant during the expulsion of the propellant from a tank. This model calculates the change in ullage volume owing to expulsion of the propellant. It also considers the net heat transfer in the ullage space. The new approach is validatedusing experimental results. It is noticeable that despite othermodelling approaches, the present pressurization systemmodelling is not decoupled from the turbopump system. It means that the interaction is observed between these two systems. Finally, the periodic operation of a GGO is compared with its normal performance, and acceptable results are obtained.

Aircraft fuel tank system

Abstract: An aircraft fuel tank system is disclosed in which a vent tank is provided with an additional ullage vent for use, in combination with an eternal flame barrier means, when refuelling.

A Study of Fluid Interface Configurations in Exploration Vehicle Propellant Tanks

Abstract: The equilibrium shape and location of fluid interfaces in spacecraft propellant tanks while in low-gravity is of interest to system designers, but can be challenging to predict. The propellant position can affect many aspects of the spacecraft such as the spacecraft center of mass, response to thruster firing due to sloshing, liquid acquisition, propellant mass gauging, and thermal control systems. We use Surface Evolver, a fluid interface energy minimizing algorithm, to investigate theoretical equilibrium liquid-vapor interfaces for spacecraft propellant tanks similar to those that have been considered for NASA's new class of Exploration vehicles. The choice of tank design parameters we consider are derived from the NASA Exploration Systems Architecture Study report. The local acceleration vector employed in the computations is determined by estimating low-Earth orbit (LEO) atmospheric drag effects and centrifugal forces due to a fixed spacecraft orientation with respect to the Earth or Moon, and rotisserie-type spacecraft rotation. Propellant/vapor interface positions are computed for the Earth Departure Stage and Altair lunar lander descent and ascent stage tanks for propellant loads applicable to LEO and low-lunar orbit. In some of the cases investigated the vapor ullage bubble is located at the drain end of the tank, where propellant management device hardware is often located.

Marine fuel tank ullage system

Abstract: A ullage system for a marine fuel tank that maintains an exact ullage space in all marine refueling situations including refueling in moving or pitching and rolling situations. The invention includes two ball valve assemblies that are inserted into a fuel tank at approximately the same level. The two assemblies typically are at opposite ends of the tank. One of the ball valves is smaller than the other in diameter. The smaller valve is coupled to an air vent; the larger valve is coupled to the filler tube. An important feature of the present invention is that it can typically be made to fit any marine fuel tank simply by changing the length of a vent tube to reach the correct ullage level for the tank at hand. The components of the present invention can be made from standard fuel valve materials.

Evaluation of Triethylene Glycol Monomethyl Ether (TRIEGME) as an Alternative Fuel System Icing Inhibitor for JP-8 Fuel

Abstract: : In recent years there has been an increasing incidence of reports of the peeling of topcoat material in the ullage space of integral wing tanks in B-52 aircraft. Recent work indicates that with the JP-8/DiEGME combination, the icing inhibitor additive can concentrate in the tank ullage and condense at high concentrations on the upper tank walls. High concentrations of DiEGME cause swelling and subsequent peeling of the epoxy-based topcoat. In this work, we report on the identification and evaluation of alternative icing inhibitor additives that do not cause topcoat delamination in fuel tank upper surfaces. The selection process identified triethylene glycol monomethyl ether (TriEGME) as the most promising candidate for replacement of DiEGME. TriEGME was shown to exhibit equivalent icing inhibition performance to DiEGME, but also exhibits a much lower tendency to negatively impact BMS 10-39 topcoat on aircraft fuel tank ullage surfaces. Subsequent testing was performed to determine the impact of TriEGME on compatibility with other fuel system materials and its effect on fuel properties.

Method and device for generating ullage in fuel tank

Abstract: PROBLEM TO BE SOLVED: To properly maintain an oxygen concentration of an ullage in fuel tanks 40, 45, so as to prevent fire. SOLUTION: A pair of wing tank 40 and central tank 45 are provided within a fuel tank section 60 of an aircraft, to be communicated each other. The wing tank 40 is opened to outside air via a surge tank 35. NEA (Nitrogen Enriched Air) containing a large amount of nitrogen as an inert gas is introduced from an NEA supply source 15 via valves 25, 30. The NEA is guided to a mixing chamber 55 via the valve 30, during going-down of the aircraft of increasing outside air pressure, followed to be mixed with the outside air and to be guided further to the wing tank 40 and the central tank 45. The NEA is guided to the central tank 45 via the valve 25, during going-up or cruise of decreasing relatively the outside air pressure, and flows further to the wing tank 40. The oxygen concentration gets proper thereby over the whole of the fuel tanks 40, 45. COPYRIGHT: (C)2011,JPO&INPIT

Theoretical Study of Washing Inerting Process in Aircraft Fuel Tank

Abstract: Considering or not the evolution of the dissolved oxygen from fuel oil,two different washing inerting mathematical models of ullage for the fuel tank are established with differential method,and the models are verified by experimental dataOn the basis of the model without oxygen evolution,three parameters of inerting ratio,volumetric tank exchange of ullage,and total volumetric tank exchange are defined to simplify the description of the inerting process and the calculation of the nitrogen-enriched air flow rateThe results show that the volumetric tank exchange of ullage and the final oxygen concentration of the inerted ullage are independent of the fuel load,but the total volumetric tank exchange decreases when the fuel load increases in the model without oxygen evolutionIn the oxygen evolution model,because some oxygen is released from the fuel,the volumetric tank exchange increases dramatically when the fuel load increases,but the total volumetric tank exchange is still inversely related to the fuel loadUnder the same fuel load,both volumetric tank exchange of ullage and total volumetric tank exchange in the oxygen evolution model are higher than those in the model without oxygen evolutionIn the washing inerting design,aproper flow rate of nitrogen-enriched air can be estimated and determined according to the calculating results via the two models

Leak prevention in aircraft fuel tanks

Abstract: A method and apparatus for stopping a leak of fuel from an aircraft auxiliary fuel tank 2 in the event that the tank is ruptured or perforated by a projectile such as a bullet B. The tank may be installed in the aircraft hold and may comprise inner and outer skins 44, 43 creating a space between 45 which is occupied by supporting webs. The apparatus consists of a vacuum pump 37 which is connected in a vent line 30 of the aircraft auxiliary fuel tank 2. The vacuum pump 37 evacuates the tank ullage U to reduce the pressure of fuel in the tank 2 to a value below ambient atmospheric pressure in the aircraft hold so that in the event of perforation ambient air A is sucked into the tank. The rate at which air is sucked into the tank is sufficient to stop fuel leaking from the tank.

Flow Visualization and Calculation at the Outlet of Propellant Tank Pressurizing Gas Injector

Abstract: Propellant tank pressurizing gas injector is used in the pressurization system of liquid propellant rocket to reduce incoming gas velocity and distribute the gas in the tank. Temperature distribution in the propellant tank ullage is varied according to the gas injector shape, and it has influence on the required pressurant gas and thermal phenomena in the tank. In this paper, diffuser type gas injector was studied to make the ullage have stratified temperature distribution. Injected gas flow at the outlet of prototype diffuser was visulized using particle image velocimetry method and it was compared with the results of calculation. Calculation was well agreed with measurement and was used as an inlet condition of propellant tank ullage calculation.

Required Pressurant Mass for Cryogenic Propellant Tank with Pressurant Temperature Variation

Abstract: The prediction of the required pressurant mass for maintaining the pressure of propellant tanks during propellant feeding is an important issue in designing pressurization system. The temperature of pressurant fed into propellant tank is the critical factor in the required pressurant mass and is one of the most crucial design parameters in the development of pressurization system including designing the weight of pressurant tanks and the size of heat exchanger. Hence a series of propellant drainage tests by pressurizing propellant stored in a cryogenic propellant tank have been performed with measuring the temperature distribution inside ullage and the required pressurant mass according to the temperature condition of pressurant. Results shows that the required pressurant mass decreases as the temperature of pressurant increases. However, the rate of the actual pressurant mass to the ideal required pressurant mass increases.

Optical Mass Gauging System for Measuring Liquid Levels in a Reduced Gravity Environment

Abstract: A compact and rugged fiber-coupled liquid volume sensor designed for flight on a sounding rocket platform is presented. The sensor consists of a Mach-Zehnder interferometer capable of measuring the amount of liquid contained in a tank under any gravitational conditions, including a microgravity environment, by detecting small changes in the index of refraction of the gas contained within a sensing region. By monitoring changes in the interference fringe pattern as the system undergoes a small compression provided by a piston, the ullage volume of a tank can be directly measured allowing for a determination of the liquid volume. To demonstrate the technique, data are acquired using two tanks containing different volumes of liquid, which are representative of the levels of liquid in a tank at different time periods during a mission. The two tanks are independently exposed to the measurement apparatus, allowing for a determination of the liquid level in each. In a controlled, laboratory test of the unit, the system demonstrated a capability of measuring a liquid level in an individual tank of 10.53 mL with a 2% error. The overall random uncertainty for the flight system is higher than that one test, at +/- 1.5 mL.