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Showing papers on "Ullage published in 2018"


Patent
15 Aug 2018
TL;DR: In this paper, a fuel tank inerting system for aircraft is described, which consists of a catalytic reactor, a heat exchanger, and a controller configured to perform a light-off operation of the catalytic Reactor by controlling at least one lightoff parameter.
Abstract: Fuel tank inerting systems for aircraft are provided. The systems include a fuel tank, a catalytic reactor arranged to receive a first reactant from a first reactant source and a second reactant from a second reactant source to generate an inert gas that is supplied to the fuel tank to fill an ullage space of the fuel tank, a heat exchanger arranged between the catalytic reactor and the fuel tank and configured to at least one of cool and condense an output from the catalytic reactor to separate out the inert gas, and a controller configured to perform a light-off operation of the catalytic reactor by controlling at least one light-off parameter and, after light-off occurs, adjusting the at least one light-off parameter to an operating level, wherein the at least one light-off parameter comprises a space velocity through the catalytic reactor.

17 citations


Journal ArticleDOI
TL;DR: In this article, an inerting test bench was constructed to compare the inerting capabilities between NEA and mixed inert gas (MIG), and the results revealed that the variations of oxygen concentrations on the ullage and in the fuel are nearly identical no matter the inert gas is NEA or MIG.

15 citations


Journal ArticleDOI
TL;DR: In this paper, a test bench is constructed, and the variation of oxygen concentration on ullage or in the fuel is measured under various flow rates, fuel loads and initial oxygen concentrations on Ullage.
Abstract: Fuel scrubbing technology could be used for fuel tank inerting and fuel deoxygenation. Both N2 and CO2 are perfect inert gases, but the solubility of CO2 is nearly 20 times higher than that of N2 in jet fuels, so the scrubbing inerting process varies with the selection of N2 or CO2. A scrubbing test bench is constructed, and the variation of oxygen concentration on ullage or in the fuel is measured under various flow rates, fuel loads and initial oxygen concentrations on ullage. Experimental results reveal that the ullage and dissolved oxygen concentrations of CO2 scrubbing are always higher than that of N2 scrubbing. The inerting time of CO2 scrubbing of a 30%, 50% and 70% fuel load is approximately 1.42, 1.7 and 2.75 times that of N2 scrubbing, respectively. The scrubbing test under 5%, 9% and 14% initial ullage oxygen concentration revels a peak in ullage oxygen concentration of 7.23% and 9.97% for N2 scrubbing and that of 12.63%, 13.4% and 15.4% for CO2 scrubbing, respectively.

10 citations


Journal ArticleDOI
12 Apr 2018-Energies
TL;DR: In this article, a computational study of the process of removing water from an aircraft's fuel tank by pumping nitrogen enriched air (NEA) from the bottom of the tank was performed.
Abstract: This paper concerns a computational study of the process of removing water from an aircraft’s fuel tank by pumping nitrogen enriched air (NEA) from the bottom of the tank. This is an important procedure for the smooth, efficient, and safe operation of the aircraft’s engine. Due to the low partial pressure of water in the pumped NEA, it absorbs water from the fuel. The water-laden bubbles enter the ullage, the empty space above the fuel, and escape into the environment. The effects of the number of NEA inlets and the NEA mass flow rate on the timescale of the NEA pumping were investigated using Computational Fluid Dynamics. The results reveal that the absorption of water by the NEA bubbles is low and is not affected by the number of the inlets used. Yet, the water content in the fuel decreases fast during the procedure, which is the desired outcome. We show that this is due to the relatively dry NEA entering the ullage and displacing the moist air, thus reducing the partial pressure of water at the fuel/ullage interface. This shift from equilibrium conditions forces water to evaporate from the fuel’s entire surface. Furthermore, the amount of water migrating from the fuel directly into the ullage is significantly greater than that absorbed by the rising bubbles. In turn, the rate of decrease of the water content in the ullage is determined by the total NEA mass flow rate and this is the dominant contributor to the draining time, with the number of NEA nozzles playing a minor role. We confirmed this by pumping NEA directly into the ullage, where we observe a significant decrease of water even when the NEA is not pumped through the fuel. We also show that doubling the mass flow rate halves the draining time. When considering the capability of most modern aircraft to pump NEA through the fuel as part of their inerting system, the proposed method for removing water is particularly attractive, requiring very little (if at all) design modification.

2 citations


Patent
05 Apr 2018
TL;DR: In this article, the mixing flow path and the operating flow path are arranged in a co-flowing configuration such that ambient air communicated by the operating flows and inert flows communicated by mixing flows are directed into the tank.
Abstract: An inerting and venting system for an aircraft. The inerting and venting system includes a tank containing fluid to be inerted, a mixer including an operating flow path and a mixing flow path, a vent line fluidly connecting ambient atmosphere to the operating flow path of the mixer, and an inert gas line fluidly connecting an inert gas source to the mixing flow path of the mixer. The mixing flow path and the operating flow path are arranged in a coflowing configuration such that ambient air communicated by the operating flow path mixes in a coflowing manner with inert gas communicated by the mixing flow path and the coflowed mixture is directed into the tank. The inerting and venting system may include a first valve for controlling flow of vent air from ambient atmosphere to the tank, and a second valve for controlling flow of inert gas from an inert gas source to the tank. A valve adjuster is configured to passively adjust the first and second valves in response to a pressure differential between the ambient atmosphere and the tank, and to control ratio of flow in response to oxygen concentration in the inert gas or the tank ullage gas.

2 citations


01 Jan 2018
TL;DR: In this paper, the authors analyzed the fluid motion and the pressure fluctuations in the cryogenic propulsion upper stage Liquid Hydrogen (LH 2 ) and Liquid Oxygen (LO x ) tanks during the ascent phase.
Abstract: The graduation project was conducted at the upper stage liquid propulsion department of ArianeGroup at the facilities of Airbus DS, Bremen. Based on a series of past flights of Ariane 5 launcher, the aim is to analyze the fluid motion and the pressure fluctuations in the cryogenic propulsion upper stage Liquid Hydrogen (LH 2 ) and Liquid Oxygen (LO x ) tanks during the ascent phase. Pressure fluctuations (drops or rises) during the ascent phase are undesirable due to the need for relief or re-pressurization of the fuel tanks. Tank relief is obtained through relief valves, while re-pressurization is done using on-board gaseous Helium; both cases increase the failure probability of the system and/or the total weight of the launcher.The objective of the project is to find out why these pressure fluctuations occur, what are the parameters that affect the pressure evolution and at what extend the liquid fuel motion (sloshing) is responsible for this behavior.According to the literature several parameters affect the pressure evolution during sloshing. These parameters are further investigated through flight data analysis. The approach also involves CFD simulations of the kinematic behavior of the liquid fuel focusing on the sloshing angle. Finally, a statistical model is built attempting to predict the pressure change inside the tanks. Higher sloshing angles match with higher pressure rise inside the LO x tank. The magnitude of the pressure rise appears to be directly connected to the kinematic profile of the launcher as well as to the ullage volume of the tank. The maximum predicted ullage pressure is below the tank's sizing pressure limit. Regarding the LH 2 tank, no strong correlation of flight parameters to the pressure change is identified; no sufficient statistical model is built. The CFD simulation shows that relatively higher sloshing angle magnitude and duration exists near the pressure drop periods and that strong breaking waves are likely to be formed in the case of a sudden pressure drop behavior. The LH 2 tank is more prone to the formation of breaking/splashing waves. The effect of vibrations, which is not included in the CFD study, is also important for the explanation of the pressure drop magnitude.

1 citations


Patent
26 Apr 2018
TL;DR: A purge system includes an airflow source to provide an airflow, and a fuel tank, including: a tank volume including a tank ullage, at least one inlet, wherein the at least 1 inlet is in fluid communication with the tank Ullage and the airflow source, and at least 2 outlets, where one outlet can direct the inbound airflow as an outbound airflow from the tankUllage to the overboard location outside the aircraft as discussed by the authors.
Abstract: A purge system includes an airflow source to provide an airflow, and a fuel tank, including: a tank volume including a tank ullage, at least one inlet, wherein the at least one inlet is in fluid communication with the tank ullage and the airflow source to provide the airflow as an inbound airflow to the tank ullage, and at least one outlet, wherein the at least one outlet is in fluid communication with the tank ullage and an overboard location outside the aircraft to direct the inbound airflow as an outbound airflow from the tank ullage to the overboard location.

Proceedings ArticleDOI
14 May 2018
TL;DR: In this paper, the authors present an international guidance that is contained in CENELEC CLC/TR 50427: Assessment of Inadvertent Ignition of Flammable Atmospheres by Radio-Frequency Radiation.
Abstract: High Intensity Radiated Field (HIRF) testing of, in, and around, aircraft, and aircraft subsystems, that contain fuel (or other potentially explosive atmosphere creating substances) pose particular hazards for Radio Frequency (RF) Induced ignition — Hazards of Electromagnetic Radiation to Fuel (HERF). The primary threat is considered to be from ignition by RF induced sparking/arcing, as this requires far less energy than direct heating effects. Accepted international guidance that is used is contained in “CENELEC CLC/TR 50427: Assessment of Inadvertent Ignition of Flammable Atmospheres by Radio-Frequency Radiation” to identify risks posed by the testing. Where hazardous levels of RF energy are identified as being used within a HIRF test, various mitigations can be used to reduce the overall risk, such as: Air frame/fuel-system review and/or inspection to reduce the probability of any dormant or undetected make/break arcing mechanisms within the flammable atmosphere/ullage; read-across of Electrostatic Discharge (ESD)/Lightning Strike design protection measures that would make the risk non-credible; specifying a minimum fuel load so arcing mechanisms are not in ullage space; use of alternate fuels to change the fuel/air mixture in the ullage to being too rich or too lean; injection of inert atmospheres into the ullage to prevent ignition; identification of alternate assessment strategies and/or potential restriction on HIRF test levels, to identify safe and cost effective assessment solutions for aircraft HIRF clearance activities.

Patent
08 Nov 2018
TL;DR: In this article, a liquid fuel pump (20) was configured to raise the pressure of liquefied gas to a predetermined first pressure and a gas evaporator (24) was used to evaporate the liquid into gaseous form at the first pressure.
Abstract: Invention relates to a liquefied gas fuel feeding system (10) for an internal combustion piston engine (12) comprising: a tank (14) configured to store fuel in cryogenic conditions, which when in use comprises a liquid gas space (14.1) having a surface (14.2) and an ullage space (14.3) above the surface (14.2); a fuel supply line (16) arranged to extend from the tank (14) to the internal combustion piston engine (12), the fuel supply line (16) comprising successively a first line section (16.1) and a second line section 16.2), wherein the first line section (16.1) is configured to receive liquefied gas from the tank (14), and comprising a liquid fuel pump (20) configured to raise the pressure of liquefied gas to a predetermined first pressure and a gas evaporator (24) configured to evaporate the liquefied gas into gaseous form at the first pressure, and wherein the second line section (16.2) is configured to receive gaseous gas from the gas evaporator (24), the second line section (16.2) comprising a gas valve unit (25) configured to open or close the flow connection between the gas evaporator (24) and the internal combustion piston engine (12), and the liquefied gas fuel feeding system (10) is provided with a return line (26) extending from the second line section (16.2) to the tank (14), the return line (26) opening into the ullage space (14.3) of the tank (14), and wherein the return line (26) is provided with a first pressure relief valve (28).

Patent
12 Apr 2018
TL;DR: In this article, the use of a small diameter metal tube and sealing of the metal tube against the inner surface of the pipette tip near a distal opening of the tip allows for a minimal ullage volume.
Abstract: A sub-1 μL pipette having a small diameter metal tube that is concentrically located within the tip mounting shaft/portion of the pipette and extends from the distal end thereof by some predetermined distance so as to seal against the interior of a pipette tip that is installed to the tip mounting portion. The use of a small diameter metal tube and sealing of the metal tube against the inner surface of the pipette tip near a distal opening of the pipette tip allows for a minimal ullage volume.