Method and apparatus for isolating inactive fuel passages

RELATED APPLICATIONS

0001The present application claims the benefit of U.S. Provisional Patent Application No. 60/854,517 filed Oct. 26, 2006 which is incorporated herein by reference.

TECHNICAL FIELD

0002The technical field generally relates to fuel injection, and more particularly relates to fuel injection where some fuel passages are inactive in some modes of operation. While the present application was developed for gas turbine engines, it is also applicable to other areas of technology including, but not limited to furnaces and rockets.

BACKGROUND

0003Inactive fuel passage(s) may be found in equipment for many reasons including, but not limited to: a pilot injector which is utilized for low power operation and may be turned off as required at higher power; staged fuel injector(s) which may be turned on and off based upon desired operating parameters; and/or fuel injectors utilized for operation on different types of fuel at different times. During times that a fuel passage is inoperative, hot combustion products and/or fuel can enter the passages. Also, an inoperative fuel passage for liquid fuel may have stagnant residual fuel that may be altered from exposure to temperature and/or contaminants. Altered stagnant fuel may solidify or otherwise affect the performance of the fuel passage and fuel injector. There is a continued need for a system that minimizes or prevents the introduction of hot combustion products and/or fuel and air into the inactive fuel passage(s) and includes a technique for flushing residual liquid fuel from the inactive fuel passage(s) as disclosed herein.

SUMMARY

0004One embodiment relates to an apparatus having a combustion chamber and a duct in fluid flow communication with the combustion chamber. The apparatus includes at least one opening adapted for delivering a liquid fuel into the duct. The apparatus further includes at least one passage adapted for delivery of a gas upstream of the at least one opening for minimizing the entrance of a fluid other than the gas into the fuel delivery opening. Further embodiments, forms, objects, features, advantages, aspects, and benefits shall become apparent from the following descriptions, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

0005<figref idref="DRAWINGS">FIG. 1</figref> is a schematic diagram of one embodiment of an apparatus for isolating inactive fuel passages.

0006<figref idref="DRAWINGS">FIG. 2</figref> is a schematic diagram of one embodiment of a duct in fluid communication with a combustion chamber.

0007<figref idref="DRAWINGS">FIG. 3</figref> is a schematic diagram of one embodiment of at least one passage adapted for delivery of a gas upstream of an opening adapted for delivery of a liquid fuel into a duct.

0008<figref idref="DRAWINGS">FIG. 4</figref> is a schematic diagram of one embodiment of a plurality of passages arranged concentrically around the at least one opening adapted for delivery of a liquid fuel into a duct.

0009<figref idref="DRAWINGS">FIG. 5</figref> is a timeline schematically illustrating isolating inactive fuel passages.

DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

0010For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated embodiments, and that such further applications of the principles of the invention as illustrated therein as would normally occur to one skilled in the art to which the invention relates are contemplated and protected.

0011With reference to <figref idref="DRAWINGS">FIG. 1</figref>, there is illustrated a schematic diagram of one embodiment of an apparatus <b>100</b> for isolating inactive fuel passages. The reader should understand that the present application is not limited to the following embodiment unless specifically provided to the contrary.

0012The apparatus <b>100</b> includes a fuel manifolding system with a gas manifold <b>102</b> and a liquid fuel manifold <b>104</b>. The gas manifold <b>102</b> is fed by a gas supply <b>106</b>, and may be fed gaseous fuel, air, purge air, and/or other gaseous streams at various operating conditions of the system <b>100</b> as understood by one of skill in the art. During some operating conditions, the gas manifold <b>102</b> may be shut off or flowing a nominal amount of gas. In one embodiment, the gas supply <b>106</b> provides gaseous fuel and the gas manifold <b>102</b> feeds a plurality of gas injectors <b>108</b> for the operation of a turbine engine. The gas injectors <b>108</b> may feed into a combustion chamber <b>109</b>.

0013The liquid fuel manifold <b>104</b> is fed by a liquid fuel supply <b>110</b> and a water flush supply <b>112</b>. The liquid fuel manifold <b>104</b> may be fed water or liquid fuel at various operating conditions of the apparatus <b>100</b>. In some embodiments, the liquid fuel manifold <b>104</b> may be fed air, purge air, other streams, and/or may be shut off during some operating conditions. In one embodiment, the liquid fuel supply <b>110</b> provides diesel fuel, kerosene, liquid natural gas, or similar fuels to liquid injectors <b>113</b> that feed an internal combustion engine such as a turbine engine. The liquid injectors <b>113</b> may feed into a combustion chamber <b>109</b>. The liquid fuel manifold <b>104</b> may be fed by lines including one-way valves <b>114</b> or similar protections to prevent flowback of fluids to the liquid supplies <b>110</b>, <b>112</b>.

0014The apparatus <b>100</b> further includes a drain <b>116</b> fluidly connected to the gas manifold <b>102</b> and the liquid fuel manifold <b>104</b>. The drain <b>116</b> may comprise multiple drains <b>116</b> that may be separate from each other. The drain <b>116</b> may be separated from the manifolds <b>102</b>, <b>104</b> by one or more valves <b>118</b>. The valves <b>118</b> may comprise one-way valves, and may be controllable by an electronic controller (not shown) or the like.

0015In one embodiment, when fuel is not flowing to the gas manifold <b>102</b> or the liquid fuel manifold <b>104</b>, a valve <b>118</b> fluidly connected to the dormant manifold <b>102</b>, <b>104</b> is momentarily opened. The dormant manifold <b>102</b>, <b>104</b> may be pressurized by a purge fluid, causing the dormant manifold <b>102</b>, <b>104</b> to back-flush into the drain <b>116</b>. The purge fluid may be compressor air or any other generally inert fluid.

0016Referring to <figref idref="DRAWINGS">FIGS. 2 and 3</figref>, there is illustrated a schematic diagram of one embodiment of a duct <b>202</b> in fluid communication with a combustion chamber <b>109</b>. In one aspect, the combustion chamber <b>109</b> forms a portion of a gas turbine engine. However, the present application is not limited to gas turbine engines. In one embodiment, the duct <b>202</b> is a radial and/or annular duct <b>202</b> adapted to deliver a fuel and air mixture to the combustion chamber <b>109</b>. A gaseous fuel delivery device <b>204</b> discharges gaseous fuel into the duct <b>202</b>. In one aspect of the present application, the gaseous fuel delivery device <b>204</b> may be a fuel injector <b>108</b> such as one depicted in <figref idref="DRAWINGS">FIG. 1</figref>.

0017A liquid fuel passage <b>206</b> is adapted for passage of liquid fuel and/or a purging agent through at least one opening <b>208</b> formed in the duct wall <b>210</b> for the discharge of liquid fuel and/or a purging agent into the duct <b>202</b>. The opening <b>208</b> may be a discrete hole or a continuous opening. In another form the at least one opening <b>208</b> is defined by a plurality of spaced openings (not shown). The at least one opening <b>208</b> is located downstream of the area of gas fuel injection <b>212</b> associated with the gaseous fuel delivery device <b>204</b>.

0018Another fluid flow passage <b>214</b> adapted for passage of a gas through at least one opening <b>216</b> that may be upstream of the liquid fuel opening <b>208</b>. The opening <b>216</b> may be a discrete hole or a continuous opening. The gas opening <b>216</b> may be a plurality of openings that correspond to the liquid fuel openings <b>208</b>. For example, there may be one gas opening <b>216</b> upstream of each liquid fuel opening <b>208</b>. In an alternate embodiment, there may be a plurality of gas openings <b>216</b> for each liquid fuel opening <b>208</b>, wherein at least one of the plurality of gas openings <b>216</b> is directly upstream of the liquid fuel opening <b>208</b>. As used herein, directly upstream indicates a geometric positioning (i.e. a position such that gas flowing from the gas opening <b>216</b> flows across the liquid fuel opening <b>208</b>) and a distance positioning. The distance that comprises directly upstream depends upon the flow rates in the duct <b>202</b> and the flow rate of gas coming out of the gas opening <b>216</b>. A substantial amount of the gas from the opening <b>216</b> should flow across the liquid fuel opening <b>208</b> before separation from the duct wall <b>210</b> and diffusion into the main duct <b>202</b> stream. The determinations for such an arrangement are mechanical steps for one of skill in the art based upon the disclosures herein.

0019In one form the fluid flow passage <b>214</b> is relatively small in comparison to the duct <b>202</b> and can deliver a flow of gas immediately upstream of the liquid fuel opening <b>208</b>. In one form of the present application the flow of gas forms a shielding film directed in substantially the same direction as the bulk fluid flow in the duct <b>202</b>. The gas may be air that is extracted from a compressor associated with a turbine engine, however the present application is not limited to air from the compressor and the gas may be from other sources. For clarification, the fluid flowable through the passage <b>214</b> is a gas and may or may not be air. In one form of the present application the fluid flow passage <b>214</b> is concentric with the duct <b>202</b>.

0020In a liquid fuel operating mode, liquid fuel passes through the liquid fuel passage <b>206</b> and is supplied through the liquid fuel opening <b>208</b> into the duct <b>202</b>. The discharge of liquid fuel through the opening <b>208</b> may form a series of jets that discharge into the duct <b>202</b>. In one form the fuel jets discharge at a high angle of attack into the flow of air or gaseous fuel and air mixture and are atomized by the shearing action of that flow of fluid in the duct <b>202</b>. For example, the angle may be perpendicular as shown in <figref idref="DRAWINGS">FIG. 2</figref>, although other angles are possible and it is a mechanical step for one of skill in the art to determine an angle sufficient for fuel atomization in a particular embodiment. The present application contemplates other directions of discharge in addition to perpendicular.

0021In one form of the present application, the flow of gas through the fluid flow passage <b>214</b> has relatively little momentum in comparison to the liquid fuel jets through the liquid fuel opening <b>208</b> and does not influence the atomization of the liquid fuel jets. For the purposes of the present application, relatively little momentum indicates that if gas flow through the fluid flow passage <b>214</b> continues uninterrupted, the gas flow from the gas opening <b>216</b> does not significantly disturb the liquid fuel delivery through the liquid fuel opening <b>208</b>.

0022For purposes of illustration, <figref idref="DRAWINGS">FIG. 2</figref> generally depicts a gaseous flow passage <b>214</b> upstream of a liquid fuel flow passage <b>206</b>, thereby creating a gas injector blocking and/or shielding an inactive liquid flow passage <b>206</b>. However, the upstream flow passage <b>214</b> may be a gas or liquid injection passage, and the downstream flow passage <b>206</b> may be a gas or liquid injection passage. Therefore, embodiments including an upstream injector shielding a downstream injector are contemplated within the scope of the present application.

0023Referring to <figref idref="DRAWINGS">FIG. 3</figref>, in one preferred form of the present application a wall portion <b>210</b> of the duct <b>202</b> between the gas opening <b>216</b> and the liquid fuel opening <b>208</b> is smooth and free of transitions that might cause the gas film to separate before reaching the liquid opening <b>208</b>. The gas delivered from the gas flow passage <b>214</b> may be delivered at a flow rate such that the gas remains in laminar flow across the liquid fuel opening <b>208</b>. Other wall configurations for the wall portion <b>210</b> are contemplated herein.

0024Referring back to <figref idref="DRAWINGS">FIG. 2</figref>, upon termination of liquid fuel flow, which may be just a temporary interruption of the liquid fuel flow, a valve acts to admit fluid to the liquid fuel passage <b>206</b>, flushing the passage <b>206</b> of liquid fuel. The fluid admitted to flush the liquid fuel passage <b>206</b> may be referred to herein as a purge fluid. The purge fluid may be water from an engine compressor wash water supply, nitrogen from air bottles, air, or other fluids believed to be known to one skilled in the art. In one embodiment, the purge fluid comprises water from the water flush supply <b>112</b>.

0025After a predetermined period of time, the flow of purge fluid is interrupted. It should be understood that in one embodiment there are periods of time when neither liquid fuel or purge fluid are passed through the liquid fuel passage <b>206</b>. The purge fluid flow may be controlled through valves and/or other flow control devices. The purge fluid flow may occur for a predetermined time calculated according to engine operating conditions during or preceding the purge, including but not limited to operating temperatures, properties of the fuel and/or purge fluid to be utilized, and other parameters known in the art that may affect the time and/or fluid volume required for an effective purge of the liquid fuel passage <b>206</b> and/or associated manifolds <b>102</b>, <b>104</b>, fuel supply lines, and the like.

0026In a pre-mix gas fuel mode, gaseous fuel is supplied to the gaseous fuel delivery device <b>204</b> with air in the duct <b>202</b> before discharging into the combustion chamber <b>109</b>. The film or curtain of air provided by the fluid flow passage <b>214</b> flows across the liquid fuel opening <b>208</b> and reduces or prevents the gas/air mixture in the duct <b>202</b> from entering the liquid fuel passage <b>206</b>. In one form the gas film flowing over the opening(s) <b>208</b> function to aerodynamically isolate the inactive liquid fuel passage <b>206</b> from other fluid flow within the duct <b>202</b>. In one embodiment, the gas provided by the fluid flow passage <b>214</b> partially or completely blocks the ingress of the gaseous fuel and air mixture flowing in the duct <b>202</b> into the entrance of the inactive liquid fuel passage <b>206</b>. In an embodiment where the ingress of the mixture is partially blocked, the fluid flow passage <b>214</b> provides sufficient gas to ensure an air/fuel ratio within the inactive liquid fuel passage <b>206</b> less than that required to support combustion. The amount of gas that must be provided through the fluid flow passage <b>214</b> to achieve sufficient blockage depends upon the flow rates, fluid densities, and passage <b>206</b>, <b>214</b> and duct <b>202</b> sizes. The gas film is preferably formed of a quantity of clean air, however other gases and quality of air are contemplated herein.

0027Referring to <figref idref="DRAWINGS">FIG. 4</figref>, in one embodiment the fluid flow within the duct <b>202</b> proximate to the liquid fuel opening <b>208</b> is in a first direction, and the liquid fuel delivered through the opening <b>208</b> flows in a second direction substantially perpendicular to the first direction. However, other flow directions are contemplated herein. The gaseous fluid passage <b>214</b> comprises a plurality of passages <b>214</b> fluidly connected to a plurality of gas flow openings <b>216</b> arranged concentrically around the liquid fuel opening <b>208</b>, and the gas delivered from the passages <b>214</b> flows substantially in the second direction (i.e. the direction of flow through the liquid fuel opening <b>208</b>). At least one of the gas flow openings <b>216</b> arranged concentrically around the liquid fuel opening <b>208</b> is upstream of the liquid fuel opening <b>208</b>. The arrangement illustrated in the embodiment of <figref idref="DRAWINGS">FIG. 4</figref> is similar to an air spoke atomizer, but the air flow in the gaseous fluid passages <b>214</b> is substantially lower than in a typical air spoke atomizer. Specifically, the gas flow through the passages <b>214</b> can continue during delivery of fuel through the liquid fuel opening <b>208</b> without disturbing the atomization and delivery of liquid fuel to the stream flowing in the duct <b>202</b>.

0028Referring to <figref idref="DRAWINGS">FIG. 5</figref>, a timeline <b>500</b> schematically illustrating isolating inactive fuel passages is depicted. The timeline indicates a flow value of purge air fluid <b>502</b>, a flow value of gaseous fuel <b>504</b>, a flow value of liquid fuel <b>506</b>, and a flow value of a liquid purge fluid <b>508</b>. The flows indicated in the timeline <b>500</b> are schematic only, and do not indicate relative flow rates or other features of the flows.

0029For purposes of illustration, the timeline <b>500</b> begins with an engine startup at time A and an engine shutdown at time G, but the operations of isolating inactive fuel passages may proceed on a continuing basis. The order of steps described herein is not intended to be limiting, and the steps may be performed in a different order, with delays, and the like unless explicitly stated otherwise.

0030The timeline <b>500</b> begins with starting an engine and beginning a flow of purge air through the gaseous flow passage <b>214</b> at time A. The ramp-up time to achieve full gaseous flow is schematic only, and the actual time to full gaseous flow is dependent upon various parameters for a particular system. Other ramp-up and ramp-down times shown in the timeline <b>500</b> are similarly schematic in nature. The timeline <b>500</b> continues with beginning a gaseous fuel flow at time B. While the engine is fueled by gaseous fuel, the purge air flows and isolates the inactive liquid fuel passage <b>206</b>. An engine with dual-fuel capability begins a switch to liquid fuel at time C, which may include beginning with a water flush. After a prescribed time, occurring in the example at time D, the liquid fueling begins and the gaseous fueling is shut down.

0031At a later time E, the engine begins to switch from liquid fueling to gaseous fueling. In one embodiment, a water flush is performed for a period after the engine begins gaseous fueling. Again during gaseous fueling the purge air flows and isolates the inactive liquid fuel passage <b>206</b>. At a time G, the gaseous fueling is shut off, the engine is shut down, and the purge air is shut down. In one embodiment, the purge air flows throughout the engine operation from time A to time G, during times of liquid fueling and during times with no liquid fueling. The illustrated embodiment allows the use of a completely passive purging system to isolate inactive fuel passages <b>206</b>, allowing the purging system to operate without valves and controls.

0032As is evident from the figures and text presented above, a variety of embodiments according to the present invention are contemplated. In one form of the present application there is provided a system for minimizing or preventing the introduction of hot combustion products and/or fuel and air into the inactive fuel passage(s). In another form of the present application the fuel injector is utilized to deliver liquid fuel at times and includes a technique for flushing residual liquid fuel from the inactive fuel passage(s). The present application further contemplates a system that minimizes or prevents the introduction of hot combustion products and/or fuel and air into the inactive fuel passage(s) and includes a technique for flushing residual liquid fuel from the inactive fuel passage(s).

0033Certain exemplary embodiments include an apparatus comprising a combustion chamber and a duct in fluid flow communication with the combustion chamber. The duct may be an annular duct. In further exemplary embodiments at least one opening is adapted for delivering liquid fuel into the duct and at least one passage adapted for delivery (i.e. delivery passage) of a gas upstream of the at least one opening for minimizing the entrance of a fluid other than the gas into the fuel delivery opening. In further exemplary embodiments, the fluid flow in the duct comprises a gaseous fuel and air mixture. In some embodiments, the fluid flow within the duct proximate to the at least one opening is in a first direction, and the gas delivered from the at least one passage flows substantially in the first direction.

0034Certain embodiments include a gas deliverer adapted to deliver a gaseous fuel into the duct upstream of the at least one opening. In some embodiments, the at least one opening defines a plurality of spaced openings in the duct. In certain exemplary embodiments, the at least one delivery passage is just prior to the at least one opening, and a wall portion of the duct between the at least one passage and the at least one opening is smooth. The gas delivered from the at least one passage may be delivered at a flow rate such that the gas remains in laminar flow across the at least one opening.

0035In further exemplary embodiments, a third fluid is in flow communication with the at least one opening adapted for delivering liquid fuel into the duct, the third fluid being selectively dispensed through the at least one opening. The third fluid may be a purge fluid.

0036Certain exemplary embodiments include an apparatus comprising a combustion chamber and a duct in fluid flow communication with the combustion chamber. Further embodiments include a first passage adapted for delivering at least one of a liquid fuel and a purging fluid into the duct through at least one opening, and a gaseous fuel dispenser located upstream of the at least one opening; operable to dispense a gaseous fuel into the duct to form a gaseous fuel and air mixture. Further exemplary embodiments include a second passage adapted for delivering a gas through at least one hole located upstream of the at least one opening for shielding the at least one opening from the introduction of the gaseous fuel and air mixture from the duct. Further embodiments include the second passage comprising a plurality of holes arranged concentrically around the first passage. In a further embodiment, the fluid flow within the duct may be in a first direction, where the first passage delivers the liquid fuel and/or purging fluid into the duct in a second direction. In an exemplary embodiment, the second passage delivers the gas in substantially the second direction, and the second direction is substantially perpendicular to the first direction.

0037Certain exemplary embodiments include a method comprising flowing a gaseous fuel and air mixture through a duct, and shielding an entrance to a liquid fuel delivery opening with a secondary gas to block the passage of the gaseous fuel and air mixture into the entrance.

0038Certain exemplary embodiments include a method comprising discharging a gaseous fuel into a duct to form a fuel and air mixture, the duct being disposed in fluid flow communication with a combustion chamber. In further embodiments, the method includes delivering a liquid fuel through a passage and out of at least one opening into the duct. The method further includes interrupting the delivering and flowing a second gas over the at least one opening to block the flow of the fuel and air mixture into the opening. In certain embodiments, the method further includes flowing the second gas in laminar flow over the at least one opening. The method may further include purging the passage of liquid fuel after interrupting the delivering, wherein purging the passage may comprise receiving purge air from a purge air supply, and flowing the purge air into a liquid fuel manifold in fluid communication with the passage.

0039Certain exemplary embodiments include an apparatus comprising a combustion chamber and a duct in fluid flow communication with the combustion chamber. The apparatus further includes at least one liquid fuel delivery opening adapted for delivering a liquid fuel into the duct, and a means for aerodynamically isolating the at least one liquid fuel delivery opening from the duct. In certain embodiments, the method further includes a means for purging the liquid fuel from the at least one liquid fuel delivery opening.

0040While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the inventions are desired to be protected. It should be understood that while the use of words such as preferable, preferably, preferred, more preferred or exemplary utilized in the description above indicate that the feature so described may be more desirable or characteristic, nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the invention, the scope being defined by the claims that follow. In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary. A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever.