Patent Application
20050137441
This invention generally relates to a fuel delivery system for an energy conversion device, and specifically to a fuel delivery system including a fuel deoxygenator and an oxygen scavenger module for removing dissolved oxygen to increase the usable cooling capability of a fuel.
A gas turbine engine is an energy conversion device typically used in aircraft and in power generation applications. A gas turbine engine typically includes a compressor, a combustor and a turbine. Air entering the compressor is compressed and directed toward a combustor. Fuel is combined with the high-pressure air and ignited. Combustion gases produced in the combustor drive the turbine.
It is common practice to use fuel as a cooling medium for various systems onboard an aircraft. The usable cooling capacity of a particular fuel is limited by the formation of insoluble products referred to as “coke”. The formation of coke deposits is dependent on the amount of dissolved oxygen present within the fuel due to prior exposure to air. Reducing the amount of oxygen dissolved within the fuel decreases the rate of coke deposition and increases the maximum allowable temperature.
U.S. Pat. Nos. 6,315,815, and ______ assigned to Applicant, disclose devices for removing dissolved oxygen using a gas-permeable membrane disposed within the fuel system. As fuel passes along the permeable membrane, oxygen molecules in the fuel diffuse out of the fuel across the gas-permeable membrane. An oxygen partial pressure differential across the permeable membrane drives oxygen from the fuel, which is unaffected and passes over the membrane.
Another fuel deoxygenating device utilizes a catalytic material exposed to fuel flow. The catalytic material initiates reactions with components of the fuel to prevent dissolved oxygen from combining with other elements within the fuel and form coke-producing products. The catalytic material causes formation of components less likely to form coke-precursors within the fuel delivery system.
It is also known to remove dissolved oxygen from fuels with the use of oxygen scavengers. Oxygen scavengers are inorganic materials for removing dissolved oxygen. Oxygen scavengers are mostly inert materials that are non-toxic, non-flammable and easily regenerated. However, the quantity of oxygen scavenging material required for fuel de-oxygenation aboard an aircraft is impractical.
The more dissolved air that can be removed from the fuel the greater the fuel temperature before coke deposits form, and the greater usable cooling capacity available. Disadvantageously, the size of a fuel deoxygenator increases disproportionably with the requirements for removing oxygen. An increase in oxygen removal from 90% to 99% requires nearly a doubling of deoxygenator size. As appreciated, space aboard an aircraft is limited and any increase in device size affects overall configuration and operation.
Accordingly, it is desirable to develop a fuel delivery system for a gas turbine engine that removes dissolved oxygen for increasing the usable cooling capability of a fuel without requiring substantial amounts of additional space.
This invention is a fuel delivery system for an energy conversion device including a fuel deoxygenator and an oxygen scavenger module for removing dissolved oxygen and increasing the usable cooling capability of a fuel.
The fuel delivery system of this invention includes a fuel deoxygenator and an oxygen scavenger module. Fuel flowing though the fuel delivery system flows through the fuel-deoxygenating device. The fuel-deoxygenating device removes a first portion of oxygen from the fuel. Fuel emerging from the fuel-deoxygenating device flows into the oxygen-scavenging module where a second portion, smaller than the first portion of oxygen is removed from the fuel.
Fuel emerging from the oxygen scavenger is substantially free of any dissolved oxygen. The substantially oxygen free fuel is flowed through a heat exchanger for absorbing heat from another system. The removal of dissolved oxygen increases the exploitable cooling capacity of the fuel. This provides for increased engine temperature that in turn increases overall engine efficiency.
The combination of the oxygen scavenger and the fuel deoxygenator provides for an increase in removal of dissolved oxygen relative to the use of either device alone. The size of a fuel deoxygenator or oxygen scavenger module capable of removing the proportion of dissolved air removed by the combination is not optimal. The combination provides the desired increase in deoxygenation of fuel without the corresponding increase in device size.
Accordingly, the fuel delivery system of this invention provides for the removal of increased amounts of dissolved oxygen, resulting in increased usable cooling capability of fuel without requiring substantial amounts of additional space.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:
Referring to
The fuel system 20 also includes a heat exchanger 26 for rejecting heat from other systems, schematically shown at 32 to fuel 28. The other system can include cooling of cooling air or other fluids circulated through the engine 10. The specific cooling requirement dictates the configuration of the heat exchanger 26. A worker skilled in the art with the benefit of this disclosure would understand how to configure the heat exchanger 26 and fuel system 20 to utilize the increased cooling capacity of fuel provided by this invention.
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In operation a partial pressure differential is created by the vacuum source 82 between a non-fuel side 75 of the permeable membrane 73 and a fuel side 77. Oxygen indicated at arrows 80 diffuses from fuel 28 across the composite permeable membrane 73 and into the porous substrate 76. From the porous substrate 76 the oxygen 80 is pulled and vented out of the fuel system.
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Preferably, the catalytic material 84 is supported on a honeycomb structure 86 disposed within the fuel deoxygenator 22′″. However, the catalytic material may be supported on granules, extrudates, monoliths, or other known catalyst support structures.
Although embodiments of fuel deoxygenators 22 are shown and described, a worker skilled in the art with the benefit of this application would understand that other configurations of fuel deoxygenators are within the contemplation of this invention.
The size of the fuel-deoxygenating device 22 is dependent on the amount of oxygen removal required. The size of the fuel-deoxygenating device 22 increases disproportionately with increases in oxygen removal demands. For example, increasing the percent removal of oxygen from 90% to 99% would require substantially a doubling in size of the fuel-deoxygenating device 22. This is so because as oxygen is removed from the fuel, the oxygen pressure differential decreases exponentially. This decrease in available oxygen pressure differential reduces the amount of oxygen that can be removed with the fuel deoxygenator 22.
The fuel delivery system of this invention combines the fuel deoxygenator 22 with the oxygen scavenger module 24. The oxygen scavenger module 24 is disposed within the fuel flow 28 after the fuel deoxygenator 22 to remove remaining oxygen within the fuel.
Referring to
Oxygen absorbent materials are typically inert, non-toxic, non-flammable and regenerable. The disadvantage being that large quantities are required for the removing oxygen in sufficient quantities from fuel to prevent undesirable coking. The oxygen-scavenging module 24 is therefore placed after the fuel-deoxygenating device 22 to remove only a portion of oxygen from the fuel.
Preferably, the oxygen-scavenging module 24 includes a sufficient amount of oxygen absorbent material to remove approximately 10% of oxygen contained with fuel. The fuel-deoxygenating device 22 is configured to remove approximately 90% of the dissolved oxygen. Accordingly, the amount of oxygen absorbent material 25 required is small enough to be practically installed within the module 27 that can be replaced after a desired duration of operation. For example, removing 10% of the dissolved oxygen from a fuel system flowing 1000 gallons/hour must absorb approximately 425 grams of oxygen every 20 hours. 10 kilograms of oxygen absorbent material would be required to remove the desired amount of oxygen. As appreciated, this is an example and a worker with the benefit of this disclosure would understand how to determine the amount of sorbent material required for a specific application.
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The foregoing description is exemplary and not just a material specification. The invention has been described in an illustrative manner, and should be understood that the terminology used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications are within the scope of this invention. It is understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.
