US20140190178A1

US20140190178A1 - Combustor

Info

Publication number: US20140190178A1
Application number: US14/238,067
Authority: US
Inventors: Michael J. O'Donnell
Original assignee: Beckett Gas Inc
Current assignee: Beckett Thermal Solutions
Priority date: 2011-08-11
Filing date: 2012-08-10
Publication date: 2014-07-10
Also published as: CA2844693A1; CN103998867A; EP2742292A4; WO2013023147A1; EP2742292A1

Abstract

A combustion method and combustor for use in a jet engine, the jet engine having a compressor portion and a turbine portion. The combustor includes an outer tube having a central axis that extends longitudinally intermediate the compressor portion and turbine portion and is positioned to receive air discharged by the compressor portion. An inner tube is positioned within the outer tube that includes an associated outer surface spaced from the inner surface of the outer tube thereby defining a combustion chamber. The outer tube and inner tube include fluid directing structure for communicating at least some of the air discharged by the compressor portion to the combustion chamber. The fluid directing structure directs air into the combustion chamber in a direction offset from the central axis, thereby causing rotation or swirling of the air about the central axis.

Description

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 61/522,412, filed Aug. 11, 2011, the entirety of which is incorporated herein by reference.

TECHNICAL FIELD

The invention relates to a fuel burner and, in particular, relates to a combustor for a gas turbine engine or heating appliance that imparts a centrifugal force upon combustion air or a combination of air and fuel.

BACKGROUND

Gas turbines, also referred to as jet engines, are rotary engines that extract energy from a flow of combustion gas. They have an upstream compressor coupled to a downstream turbine with a combustion chamber in between. There are many different variations of gas turbines, but they all use the same basic principal.
Jet aircraft are usually powered by turbojet or turbofan engines. A turbojet engine is a gas turbine engine that works by compressing air with an inlet and a compressor, mixing fuel with the compressed air, burning the mixture in the combustor, and then passing the hot, high pressure gas through a turbine and a nozzle. The compressor is powered by the turbine, which extracts energy from the expanding gas passing through it. The engine converts energy in the fuel to kinetic energy in the exhaust, producing thrust. All the air ingested by the inlet passes through the compressor, combustor, and turbine.
A turbofan engine is very similar to a turbojet except that it also contains a fan at the front of the compressor section. Like the compressor, the fan is also powered by the turbine section of the engine. Unlike the turbojet, some of the flow accelerated by the fan bypasses the combustor and is exhausted through a nozzle. The bypassed flow is at a lower velocity, but a higher mass, making thrust produced by the fan more efficient than thrust produced by the core. Turbofans are generally more efficient than turbojets at subsonic speeds, but they have a larger frontal area which generates more drag at higher speeds.
Turboprop engines are jet engine derivatives that extract work from the hot-exhaust jet to turn a rotating shaft, which is then used to spin a propeller to produce additional thrust. Turboprops generally have better performance than turbojets or additional thrust. Turboprops generally have better performance than turbojets or turbofans at low speeds where propeller efficiency is high, but become increasingly noisy and inefficient at high speeds.
Turboshaft engines are very similar to turboprops, differing in that nearly all of the energy in the exhaust is extracted to spin the rotating shaft. Turboshaft engines are used for stationary power generating plants as well as other applications.
One problem associated with gas turbine engines, especially in aircraft, is the possibility of flame-out, which occurs when the flame becomes extinguished within the combustion chamber. One of the causes of flame-out is instability of the flame front within the combustor. Since engine failure during flight is clearly problematic, it would be advantageous to construct a gas turbine engine such that the possibility of flame-out was reduced. For stationary power generating systems there is a need for reduced emissions, primarily NOx, in order to meet newer, more stringent clean air requirements.

SUMMARY OF THE INVENTION

The present invention provides a new and improved method of combustion and a combustor or burner that can be used in a jet engine, as well as other heating/burner applications. In the illustrated embodiment, the combustor is shown as it would be used with a jet engine of the type that includes a compressor portion and a turbine portion.
According to one of the preferred and illustrated embodiments, the jet engine includes a compressor portion and turbine portion. In this one preferred and illustrated embodiment, the combustor includes a longitudinally extending tube having a central axis, which is positioned to receive air that is charged by the compressor portion. The outer tube has an outer surface and an inner surface. An inner tube is positioned within the outer tube and includes an associated outer surface that is spaced from the inner surface of the outer tube, thereby defining a passage that may be a combustion chamber where a fuel mixture can be at least partially combusted.
In the illustrated embodiment, the outer tube includes fluid directing structure for communicating at least some of the air discharged by the compressor portion to a combustion chamber passage that is defined between the inner surface of the outer tube and the outer surface of the inner tube. The fluid directing structure directs air in a direction offset from the central axis of the outer tube, thereby causing rotation of the air about the central axis. At least one fuel supply member directly or indirectly supplies fuel to the combustion chamber passage in order to form a rotating or swirling fuel air mixture in the combustion chamber passage.
According to the invention, the rotating fuel mixture in the combustion chamber passage may be completely or partially burned in the combustion chamber passage.
In a preferred and illustrated embodiment, the inner tube also includes associated fluid directing structure for communicating air it receives from the compressor portion to the combustion chamber passage. The associated fluid directing structure directs the air in a direction that is also offset from the central axis.
In one embodiment, the fuel member communicates directly with the combustion chamber passage and directly supplies fuel to the chamber passage where it is mixed with the compressor air to form a rotating/swirling combustible fuel/air mixture. In an alternate embodiment, the fuel member premixes the fuel with some compressor air and then supplies the premixed fuel and air to the combustion chamber passage where it is mixed with the rotating compressor air (or fuel/air mixture) already delivered to the combustion chamber passage. In another alternative embodiment, the fuel member discharges fuel into a stream of air discharged by the compressor portion as it flows towards the combustor. In this alternate embodiment, both fuel and compressor air flow through the fluid directing structure of the outer and/or inner tubes into the combustion chamber passage.
According to one illustrated embodiment, the outer and inner tubes are arranged such that their respective axes are coincident. According to an alternate construction of this embodiment, the axes of the inner and outer tubes are coincident with a rotation axis defined by the compressor portion.
According to a preferred embodiment, the fluid directing structure includes a plurality of openings and a guide associated with each opening, the guides being angled relative to a tube surface for imparting a radial rotation to the air about the central axis. In the illustrated embodiment, the guides are arranged in a series of rows that extend around the periphery of the outer tube. In the preferred embodiment, the inner tube has a similar fluid directing structure.
In a more preferred embodiment, the fluid directing structure includes a series of steps formed in the outer tube, the steps including openings for directing the air into the combustion chamber passage in a direction that causes rotation or swirling of the mixture radially about the central axis. According to a feature of this more preferred embodiment, each step has an L-shape including a first member and a second member including the openings for directing the air, such that the openings of one step direct the air across the adjoining step to impart rotation to the mixture.
According to an exemplary embodiment, the fluid directing structure includes a plurality of openings that each extend from the outer surface of the outer tube to the inner surface, each opening extending through the outer tube at a relative angle to an axis extending normal to the outer surface of the inner tube and through the central axis. According to a feature of this embodiment, the outer tube includes a plurality of second openings that each extend from the outer surface of the outer tube to the inner surface in a direction extending to the central axis. In a more preferred embodiment, the inner tube includes similar fluid directing structure.
In a preferred and illustrated embodiment, the outer tube is formed as a series of overlapping arcuate plates that define the fluid directing structure, each plate having a corrugated profile and having a series of passages through which the air is directed into the combustion chamber passage. In this embodiment, the corrugated profile includes a plurality of alternating peaks and valleys and, preferably, the overlapping plates are longitudinally and radially offset from one another, such that the peaks of one plate are positioned between the peaks of adjacent plates. In addition, in this embodiment, each plate directs the air in a direction that extends substantially parallel to the adjoining plate to impart rotation to the mixture.
In the preferred construction of this embodiment, the inner tube of the combustor includes a first end that communicates with air discharged by the compressor portion and a second end having an end wall for closing the second end of the inner tube in a gas tight manner. With this construction, the fluid directing structure associated with the inner and outer tubes provides the only fluid path to the combustion chamber passage.
In a combustor constructed in accordance with one or more of the disclosed embodiments, the rotating mixture is radially layered within the combustion chamber passage.
According to still another embodiment of the invention, the combustor includes a tube having a central axis that is located intermediate the compressor portion and the turbine portion and has an outer and inner surface. Fluid directing structure is formed on the tube, including passages extending from the outer surface to the inner surface. The inner surface of the tube defines a combustion chamber. A passage communicates air discharged by the compressor portion with the outer surface of the tube. The fluid directing structure directs the compressor air at an angle offset from the central axis of the tube, thereby causing rotation of compressor air in the combustion chamber. A fuel member supplies fuel or a mixture of fuel and air, directly or indirectly, to the combustion chamber.
In the illustrated combustion of this alternate embodiment, a spaced apart continuous wall surrounds the tube, thereby defining at least a portion of the passage for communicating air to the outer surface of the tube. In a more preferred construction of this embodiment, the jet engine includes a plurality of these alternate combustors that are spatially arranged around an axis of rotation defined by the compressor portion.
An object of the present invention is to provide a jet engine combustor in which air or fuel and air are forced through fluid directing structures to cause swirling and/or rotation of the air/fuel mixture about the axis of the combustor.
Other objects and advantages and a fuller understanding of the invention will be had from the following detailed description of the preferred embodiments and the accompanying drawings.
Additional features and a further understanding of the invention will become apparent by reading the following detailed description made in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a combustor for use in a jet engine in accordance with an aspect of the present invention;

FIG. 2A is a section view taken along line 2A-2A of FIG. 1;

FIG. 2B is a section view taken along line 2B-2B of FIG. 1;

FIG. 3A is an enlarged view of a portion of a fluid directing structure constructed in accordance with a preferred embodiment of the invention;

FIG. 3B is a section view of FIG. 3A taken along line 3B-3B;

FIGS. 4A-4D are enlarged views of portions of alternative fluid directing structure in accordance with the present invention;

FIG. 5 is a schematic illustration of an alternative combustor for use in a jet engine in accordance with another aspect of the present invention;

FIG. 6A is a section view taken along line 6A-6A of FIG. 5;

FIG. 7 is a schematic illustration of an alternative combustor for use in a jet engine in accordance with another aspect of the present invention;

FIG. 8A is a section view taken along line 8A-8A of FIG. 7;

FIG. 8B is a section view taken along line 8B-8B of FIG. 7;

FIG. 9 is a schematic illustration of an alternative combustor for use in a jet engine in accordance with another aspect of the present invention;

FIG. 10 is a section view taken along line 10-10 of FIG. 9, and;

FIG. 11 is a section view taken along line 11-11 of FIG. 10.

DETAILED DESCRIPTION

The invention relates to a fuel burner and, in particular, relates to a combustor for a gas turbine engine that imparts a centrifugal force upon combustion air or a combination of air and fuel. Although the drawings generally depict a turbojet type engine and the specification describes the present invention in use in a jet engine, those having ordinary skill will appreciate that the combustor of the present invention described herein is suitable for use in any of the engine variants described above.
FIGS. 1-2B illustrate a combustor 240 for use in a jet engine 200 in accordance with an embodiment of the present invention. As shown in FIG. 1, the jet engine 200 extends along an axis 202 and includes a housing 210 that extends along the axis from a first end 212 to a second end 214. A wall 216 of the housing 210 defines an interior passage 218 that extends the length of the housing. A turbine 220, a compressor 230, and at least one combustor 240 are positioned within the passage 218 of the housing 210 and along the axis 202. The compressor 230 includes a shaft or connecting member 232 that connects the compressor to the turbine 220 such that the connecting member and turbine rotate together. The combustor 240 is positioned axially between the turbine 220 and the compressor 230.
As shown in FIGS. 2A-2B, the combustor 240 includes outer and inner tubes 242, 244 that are concentric to one another about a central axis 241 and secured to one another and the housing 210. The central axis 241 of the combustor 240 may be coaxial with the axis 202 of the engine 202 or may be spaced from the axis of the engine (not shown). The connecting member 232 extends through the inner tube 244 and a shaft seal 233 is provided between the connecting member and the inner tube to prevent fluid from passing between the connecting member and the inner tube directly into the turbine 220.
The space between the outer and inner tubes 242, 244 defines a fluid passage 274 for receiving fuel and air. The periphery of the outer tube 242 includes fluid directing structure 248 for directing fluid radially inward to the fluid passage 274. More specifically, the fluid directing structure 248 is configured to direct fluid to the fluid passage 274 in a direction that is offset from the central axis 241 of the combustor 240 and along a path that is angled relative to the normal of the inner surface (not shown) of the outer tube 242.
The periphery of the inner tube 244 includes fluid directing structure 252 for directing fluid from the interior 250 of the inner tube radially outward into the fluid passage 274. More specifically, the fluid directing structure 252 is configured to direct fluid into the fluid passage 274 in a direction that is offset from the central axis 241 of the combustor 240 and along a path that is angled relative to the normal of the outer surface (not shown) of the inner tube 244. The fluid directing structures 248, 252 may direct their respective fluid in the same general direction. The fluid directing structure 248, 252 may include a series of openings with associated fins or guides for directing the fluid in the desired manner (FIGS. 3A-4D).
The jet engine 200 further includes one or more tubular fuel supply members 254 that extend into or are otherwise in direct fluid communication with the fluid passage 274 of the combustor 240 and extend radially outward from the passage, through the wall 216 of the housing 210, and to a fuel source (not shown) outside of the housing. The fuel supply members 254 thereby deliver fuel directly to the fluid passage 274, as indicated generally by arrows F1. Although six fuel supply members 254 spaced radially equidistant from one another are illustrated in FIGS. 1-2B, it will be appreciated that any number of fuel supply members exhibiting any spacing configuration may be provided in accordance with the present invention.
A ring-shaped wall 251 (see FIG. 2B) is secured to the end of the outer and inner tubes 242, 244 closer to the compressor 230 in order to seal one end of the fluid passage 274 in a fluid-tight manner. The wall 251 is provided with openings 253 that receive ends of the fuel supply members 254 to establish the direct fluid path between the fuel supply members and the fluid passage 274.
In operation, air enters the compressor 230 at the first end 212 of the housing 210 in the direction indicated generally by the arrows D2 (FIG. 2A) and exits the compressor as compressed air. Some of the compressed air exiting the compressor 230 flows directly into the interior 250 of the inner tube 244 as indicated generally by the arrows D3 and through the fluid directing structure 252 in the inner tube 244 into the fluid passage 274. Some of the compressed air also flows to the peripheral annular space 277 between the outer tube 242 and the wall 216 of the housing 212, where it flows through the fluid directing structure 248 in the outer tube and into the fluid passage 274 as indicated generally by arrows D4. A wall 255 secured to the end of the outer and inner tubes 242, 244 closer to the turbine 220 and between the outer tube and the wall 216 of the housing 210 prevents the compressed air D4 from passing into the turbine without first passing through the combustor 240.
The compressed air D3, D4 is mixed with fuel F1 that is injected into the combustor 240 via the fuel supply members 254. Since the ring-shaped wall 251 blocks the end of the fluid passage 274 adjacent to the compressor 230, the fuel F1 is directed by the fuel supply members 254 directly into the fluid passage 274. Accordingly, the fluid directing structures 248, 252 of the combustor 240 only control the flow of compressed air D4, D3 into the fluid passage 274 such that the compressed air mixes with the fuel F1 from the fuel supply members 254 within the fluid passage 274 in a desired manner. More specifically, as the peripheral air D4 passes through the fluid directing structure 248 in the outer tube 242 and into the fluid passage 274, the air mixes with the fuel F1 exiting the fuel supply members 254. Due to the configuration of the fluid directing structure 248, the compressed air D4 is imparted with a centrifugal force about the central axis 241 of the combustor 240 as it enters the fluid passage 274. The swirling air D4 mixes with the fuel F1 to create a swirling air/fuel mixture within the fluid passage 274 and about the central axis 241 of the combustor 240.
Likewise, the compressed air D3 enters the interior 250 of the inner tube 244 and passes through the fuel directing structure 252 of the inner tube 244 and into the fluid passage 274, thereby imparting a centrifugal force upon the compressed air D3 about the central axis 241 of the combustor 240. The swirling air D3 mixes with the fuel F1 to create an additional swirling air/fuel mixture within the fluid passage 274 and about the central axis 241 of the combustor 240. The mixture formed from the fuel F1 and the compressed air D3 mixes with and becomes indistinguishable from the mixture formed from the fuel F1 and the compressed air D4 within the fluid passage 274.
Since the fluid directing structures 248, 252 extend around the entire periphery of the outer tube 242 and the inner tube 244, respectively, the collective air/fuel mixture within the fluid passage 274 is forced generally in a single direction, indicated by arrow R (FIG. 2B), that is transverse to the central axis 241 of the combustor 240. It will be appreciated that the fluid directing structures 248, 252 may direct the respective air/fuel mixtures in the same direction, e.g., clockwise relative to the central axis 241, within the fluid passage 274. Consequently, the air/fuel mixture within the fluid passage 274 undergoes a rotational, spiraling effect relative to the central axis 241 of the combustor 240 and within the fluid passage 274. The rotating, spiraling air/fuel mixture is ignited by an ignition device (not shown) of any number of types well known in the art and positioned in any number of suitable locations to light the combustor 240. For example, the wall 251 may be provided with an opening (not shown) through which an igniter extends. Flame proving means (not shown) may be positioned in any number of suitable locations to detect the presence of flame.
Due to the continued supply of air and fuel to the combustor 240 from the compressor 230 and the fuel supply members 254, subsequent spiraling air/fuel mixtures are created within the fluid passage 274 prior to complete combustion of prior air/fuel mixtures within the passage such that the spiraling air/fuel mixtures become radially layered within the fluid passage. The swirling or rotation of the air fuel mixture in the passage 274 provides thorough mixing of the fuel and air, thereby improving combustion. The swirling pattern imparted to the fuel air mixture contributes to combustion stability and, therefore, reduces the chances of flame out.
As shown in FIGS. 2A-2B, the combustion products from the ignited air/fuel mixture exit the combustor 240 rotating about the central axis 241 of the combustor 240 and the axis 202 of the jet engine 200 as indicated generally by arrows R2. The combustion products of the air/fuel mixture exit the combustor 240 at elevated pressure and velocity and pass through the turbine 220, thereby imparting rotation upon the turbine as indicated generally by arrow R3. The turbine 220, in turn, directs the combustion products out of the jet engine 200 in the direction indicated generally by arrows T to provide thrust to the aircraft. Since the connecting member 232 rotatably connects the turbine 220 to the compressor 230, the rotating turbine drives the compressor.
Each of the fluid directing structures 248, 252 may have any configuration suitable for imparting rotation to the compressed air D4, D3, respectively, to form an air/fuel mixture with the fuel F1 and within the fluid passage 274 that swirls about the central axis 241 of the combustor 240 in accordance with the present invention. FIGS. 3A-3B illustrate one configuration of the fluid directing structure 252 of the inner tube 244 and those having ordinary skill will appreciate that the fluid directing structure 248 of the outer tube 242 may have a similar construction to the fluid directing structure 252. Alternatively, the fluid directing structures 248 and 252 may be dissimilar (not shown). In any case, the fluid directing structure 248 is configured to direct fluid radially inward while the fluid directing structure 252 is configured to direct fluid radially outward.
As shown in FIGS. 3A-B, the fluid directing structure 252 includes a plurality of openings 284 in the inner tube 244 for allowing the compressed air D3 to pass radially outward from the central passage 250 of the inner tube to the fluid passage 274. Each of the openings 284 extends entirely through the inner tube 244 from an inner surface 282 to an outer surface 280. Each opening 284 may have any shape, such as rectangular, square, circular, triangular, etc. The openings 284 may all have the same shape or different shapes. The openings 284 are aligned with one another along the periphery, i.e., around the circumference, of the inner tube 244 to form an endless loop. One or more endless loops of openings 284 may be positioned adjacent to one another or spaced from one another along the length of the inner tube 244. Each loop may have any number of openings 284. The openings 284 in adjacent loops may be aligned with one another or may be offset from one another. The size, shape, configuration, and alignment of the openings 284 in the inner tube 244 is dictated by desired flow and performance characteristics of the compressed air D3 flowing through the openings. Although the openings 284 are illustrated as being arranged in a predetermined pattern along the inner tube 244, it will be appreciated that the openings may be randomly positioned along the inner tube (not shown).
Each opening 284 includes a corresponding fluid directing projection or guide 286 for directing the compressed air D3 passing through the associated opening radially outward into the fluid passage 274 and in a direction that is offset from the central axis 241 of the combustor 240, i.e., a direction that will not intersect the central axis. The guides 286 are formed on or integrally attached to the inner surface 282 and/or the outer surface 280 (not shown) of the inner tube 244. Each guide 286 extends at an angle (shown in FIG. 3 b) relative to the outer surface 280 of the inner tube 244. The guides 286 may extend at the same angle or at different angles relative to the outer surface 280 of the inner tube 244. Each guide 286 extends at an angle, indicated at α2, relative to an axis 287 extending normal to the outer surface 280 of the inner tube 244.
Since the fluid directing structure 248 on the outer tube 242 may be formed similar to the fluid directing structure 252 on the inner tube 244, those having ordinary skill in the art will appreciate that guides and openings associated with the fluid directing structure 248 (not shown) direct the compressed air D4 passing through the outer tube radially inward toward the central passage 274 and in a direction that is offset from the central axis 241 of the combustor 240. Similar to the fluid directing structure 252 on the inner tube 244, the guides of the fluid directing structure 248 on the outer tube 242 may be formed in or integrally attached to the inner surface and/or the outer surface of the outer tube (not shown). In the illustrated embodiment, the fluid directing structures 248, 252 direct the associated incoming compressed air D4, D3 in the same general direction such that the combined air/fuel mixture swirls within the fluid passage 274 around the central axis 241 of the combustor 240 in the same general direction.
FIGS. 4A-D illustrate alternative configurations of the fluid directing structure 252 in the inner tube 244 in accordance with the present invention. The fluid directing structure 252 a-d directs the incoming compressed air D3 radially outward into the fluid passage 274 and in a direction that is 1) offset from the central axis 241 and 2) angled relative to the normal of the outer surface 280 of the inner tube 244 such that compressed air mixes with the fuel F1 to form an air/fuel mixture within the central passage 274 that exhibits a swirling, rotational path around the central axis while becoming radially layered relative to the central axis. The openings in the fluid directing structure may be randomly positioned along the inner tube 244 or may be arranged in any predetermined pattern dictated by desired flow and performance criterion.
FIGS. 4A-D illustrate alternative configurations of the fluid directing structure 252, 248 that may be formed on or integrally attached to the inner and/or outer surface of the respective tube 244, 242 in accordance with the present invention. More specifically, either of the fluid directing structures 248, 252 may exhibit any of the configurations shown in FIGS. 4A-D. In the preferred embodiment, the fluid directing structure 248 directs the incoming compressed air D4 radially inward into the fluid passage 274 and in a direction that is 1) offset from the central axis 241 and 2) angled relative to the normal of the inner surface of the outer tube 242 (not shown) such that the compressed air mixes with the fuel F1 to form an air/fuel mixture that exhibits a swirling, rotational path within the central passage 274 and around the central axis. Likewise, the fluid directing structure 252 directs the incoming compressed air D3 radially outward into the fluid passage 274 and in a direction that is 1) offset from the central axis 241 and 2) angled relative to the normal of the outer surface 280 of the inner tube 244 (not shown) such that compressed air mixes with the fuel F1 to form an air/fuel mixture that exhibits a swirling, rotational path within the central passage 274 and around the central axis. In each case, the openings in the fluid directing structure 248, 252 may be randomly positioned along the respective tube 242, 244 or may be arranged in any predetermined pattern dictated by desired flow and performance criterion.
In FIG. 4A, the fluid directing structure 252 a includes a plurality of guides 286 a that define openings 284 a in the inner tube 244 a. The guides 286 a are arranged in a series of rows that extend around the periphery of the inner tube 244 a. The annular rows are positioned next to one another along the length of the inner tube 244 a. The guides 286 a of adjacent rows may be radially offset from one another or may be radially aligned with one another (not shown). The guides 286 a in each row may be similar or dissimilar to one another. The guides 286 a direct the compressed air D3 passing through the openings 284 a in a radially inward direction that is offset from the central axis 241 and at an angle α2 relative to the axis 287 a extending normal to the outer surface 280 a of the inner tube 244 a. If the guides 286 a within a row are fully or partially aligned with one another around the periphery of the inner tube 244 a, the compressed air D3 exiting each guide in that row is further guided in a direction offset from the central axis 241 by the adjacent guide(s) in the same row.
In FIG. 4B, the inner tube 244 b is formed as a series of steps that each includes a first member 283 and a second member 285 that extends substantially perpendicular to the first member to form an L-shaped step. The second member 285 of each step includes a plurality of openings 284 b for directing the compressed air D3 in a direction that is offset from the central axis 241 and angled relative to the axis (not shown) extending normal to the outer surface 280 b of the inner tube 244 b. In particular, the openings 284 b in each second member 285 direct the compressed air D3 across the first member 283 of the adjoining step to impart rotation to the compressed air and, thus, to the air/fuel mixture within the fluid passage 274 about the central axis 241.
In FIG. 4C, the fluid directing structure 252 c includes a plurality of openings 284 c that extend from the inner surface 282 c of the inner tube 244 c to the outer surface 280 c. The openings 284 c extend through the inner tube 244 c at an angle relative to the axis 287 c extending normal to the outer surface 280 c of the inner tube 244 c and through the central axis 241 of the combustor 240. The openings 284 c in the inner tube 244 c direct the compressed air D3 and, thus, the air/fuel mixture within the fluid passage 274 in a direction that is offset from the central axis 241 and at an angle relative to the axis 287 c in order to impart rotation to the air/fuel mixture within the fluid passage about the central axis.
In FIG. 4D, the fluid directing structure 252 d is formed by a series of arcuate, overlapping plates 330 that cooperate to form the inner tube 244 d. Each plate 330 has a corrugated profile that includes peaks 332 and valleys 334. The plates 330 are longitudinally and radially offset from one another such that that peaks 332 of one plate 330 are spaced between the peaks of adjacent plates. In this configuration, the peaks 332 and valleys 334 of the plates create passages 336 through which the compressed air D3 is directed. Each plate 330 directs the compressed air D3 in a direction that extends substantially parallel to the adjoining arcuate plate to impart rotation to the compressed air and, thus, to the air/fuel mixture within the fluid passage 274 about the central axis 241. The air/fuel mixture within the fluid passage 274 is thereby directed in a direction that is offset from the central axis 241 of the combustor 240 and angled relative to the axis (not shown) extending normal to the plates 330.
FIGS. 5-6A illustrate a jet engine 200 a in accordance with another embodiment of the present invention. Features in FIGS. 5-6A that are identical to features in FIGS. 1-2B have the same reference number as FIGS. 1-2B, whereas features in FIGS. 5-6A that are not similar to features in FIGS. 1-2B are given the suffix “a”. FIGS. 5-6A illustrate a jet engine 200 a similar to the jet engine 200 of FIGS. 1-2B. In the jet engine 200 a of FIGS. 5-6A, the fuel being delivered via the fuel pipe 254 a is partially mixed with air prior to being injected into the region 274. The partially pre-mixed fuel is indicated by the reference character F3 and, as seen best in FIG. 6A, the fuel pipe 254 a passes through a pre-mix chamber 254′. As seen best in FIG. 6A, the pre-mix chamber 254′ receives compressor air indicated by the reference character D5 through a port (not specifically shown) formed in the pre-mix chamber 254′. Fuel passing through the chamber mixes with the incoming air stream (D5) and is injected to the region 274 where it is mixed with additional air D4, D3 delivered through ports 252, 248 formed in the members 244, 242, respectively (see also FIG. 2B).
The jet engine burner shown in FIG. 6A operates essentially similar to the burner shown in FIG. 2A, except that the fuel is pre-mixed with some air prior to being injected into the region 274. The fuel and air movement patterns shown in FIG. 2B are equally applicable to the burner shown in FIG. 6A. In the jet engine 200 a of FIGS. 5-6A, however, the fuel delivered by the fuel supply members 254 a is partially pre-mixed with the incoming compressed air D5 before being discharged into the chamber 274. This partial fuel mixture is further mixed with compressed air D3 and D4 which is injected through the respective fluid directing structure 252 and 248 and into the fluid passage/combustion chamber 274′ where the fully mixed fuel charge is ignited and burned.
The fluid directing structure 252 allows the air D3 within the passage 250 to be directed radially outward into the fluid passage 274, and the fluid directing structure 248 allows the air D4 in the region 277 outside of the outer tube 242 to be directed radially inward into the fluid passage 274. Either or both of the fluid directing structures 248, 252 may have any of the configurations illustrated in FIGS. 3A-4D.
The compressed air D3, D4 mixes with the partial fuel mixture F3 from the fuel supply members 254 a to form an air/fuel mixture within the fluid passage 274 that swirls around the axis 241 of the combustor 240 a. Due to the configuration of the fluid directing structure 248, the compressed air D4 is imparted with a centrifugal force about the axis 241 of the combustor 240 a as it passes into the fluid passage 274. Likewise, the compressed air D3 enters the interior 250 of the inner tube 244 and then through the directing structure 252 of the inner tube 244 and into the fluid passage 274, thereby imparting a centrifugal force upon the air/fuel mixture about the axis 241 of the combustor 240 a.
Those having ordinary skill in the art will appreciate that a mixture of air and fuel is formed in the fluid passage and imparted with a centrifugal force that causes the air/fuel mixture within the fluid passage 274 to rotate or spiral around the central axis of the combustor, thus improving and stabilizing combustion.
FIGS. 7-8 illustrate a jet engine 200 b in accordance with another embodiment of the present invention. Features in FIGS. 7-8 that are identical to features in FIGS. 1-2B or FIGS. 5-6A have the same reference number as FIGS. 1-2B or FIGS. 5-6A, whereas features in FIGS. 7-8 that are not similar to features in FIGS. 1-2B are given the suffix “b”. Similar to the jet engine 200 of FIGS. 1-2B, a wall 251 b is secured to the end of the combustor 240 b closer to the compressor 230 and a wall 255 b is secured to the end of the combustor closer to the turbine 220. In the jet engine 200 b of FIGS. 7-8, however, the fuel F4 is injected upstream from the combustor and is completely mixed with compressed air D4′ before entering the combustor 240 b.
The jet engine 200 b of FIGS. 7-8 includes a fluid mixing element 290 secured to the housing 210 for pre-mixing the compressed air D4′ and fuel F4 exiting the fuel supply members 254 b such that the air and fuel is completely mixed prior to entering the combustor 240 b. The fluid mixing element 290 is positioned along the axis 202 of the jet engine 200 b between the fuel supply members 254 b and the combustor 240 b and includes an outer element 292 and an inner element 294 positioned concentric to one another and the connecting member 232. The outer element 292 is ring-shaped and has a generally frustoconical configuration that tapers radially inward in a direction extending towards the combustor 240 b, i.e., leftward as viewed in FIG. 8. The inner element 294 is positioned in the interior of the outer element 292 and is secured to or integrally formed with the outer element. The compressor/turbine connecting member 232 extends through an opening indicated generally by the reference character 294 a in the inner element 294.
An annular gap 296 extends between the inner element 294 and the outer element 292 and tapers inwardly in a direction extending towards the combustor 240 b, i.e., the cross-sectional area of the gap along the axis 202 decreases in the direction towards the combustor. The fluid mixing element 290 is configured such that the compressed air D4′ from the compressor and the fuel F4 exiting the fuel supply members 254 b must pass through the gap 296 in the mixing element in order to reach the combustor 240 b. Since the cross-sectional area of the gap 296 decreases along the length of the fluid mixing element 290, the compressed air D4′ and fuel F4 become mixed together as the air and fuel travel through the fluid mixing element. The air D4′ and fuel F4 exit the fluid mixing element 290 as a fully pre-mixed mixture, indicated generally as M in FIG. 8. Although the fluid mixing element 290 is illustrated as having a particular construction, those having ordinary skill will appreciate that any structure or structures may be used that are configured to mix the compressed air D4′ and fuel F4 to form a fully pre-mixed mixture M that enters the combustor 240 b to be ignited.
The mixture M enters the combustor 240 b along two different pathways. Some of the mixture M flows to the region 277, i.e., the exterior of the combustor 240 b between the wall 216 of the housing 210 and the outer tube 242, where it is directed radially inward by the fluid directing structure 248 of the outer tube 242 into the fluid passage 274. The remainder of the mixture M flows into the interior 250 of the inner tube 244 where it is directed radially outward by the fluid directing structure 252 of the inner tube into the fluid passage 274. The fluid directing structures 248, 252 cause the collective mixture M to swirl within the fluid passage 274 around the axis 241 of the combustor 240 b in a manner similar to that illustrated in FIG. 2B. The mixture M is then ignited within the fluid passage 274 by an ignition source (not shown) and the combustion products of the ignited mixture are expelled from the combustor 240 b towards the turbine 220 in the manner indicated generally by arrows R2 in order to drive the turbine in the manner described.
FIGS. 9-11 illustrate a jet engine 200 c in accordance with another aspect of the present invention. In the jet engine 200 c of FIGS. 9-11, a plurality of combustors 240 c is arranged about the central axis 202 of the jet engine. Each of the combustors 240 c may constitute the non-pre-mixed combustor 240 of FIGS. 1-2B, the partially pre-mixed combustor 240 a of FIGS. 5-6B or the fully pre-mixed combustor 240 b of FIGS. 7-8 or modifications thereof. Features in FIGS. 9-11 that are identical to features in FIGS. 1-8 have the same reference number as FIGS. 1-8, whereas features in FIGS. 9-11 that are similar to features in FIGS. 1-8 are given the suffix “c”.
As shown in FIG. 9, the compressor 230 and the turbine 220 are positioned within the housing 210 on opposing sides of the combustors 240 c. The combustors 240 e are preferably axially aligned with one another and are radially spaced about the axis 202 of the jet engine 200 c (FIG. 9). Although five combustors 240 c are illustrated in FIGS. 9-11, it will be appreciated that more or fewer combustors may be provided in accordance with the present invention. Furthermore, the combustors 240 c may be symmetrically or asymmetrically spaced about the central axis 202. The combustors 240 c may extend substantially parallel to one another and the axis 202 or may extend at an angle relative to one another and/or the axis. A wall 270 is provided between the wall 212 of the housing 210 and the combustors 240 c and between the combustors to ensure that fluid only flows into the combustors, i.e., not around or between the combustors and the wall of the housing. Another wall 272 is also preferably provided to prevent air or fuel/air from bypassing the combustors. The walls 270, 272 may also serve as mounting plates or supports for the combustors 240 c.
The combustors 240 c are different from the combustors 240, 240 a, 240 b in that no inner tube is used. The outer tube 242′ of the combustor has fluid directing structure 248 such that the mixture of air and fuel is directed from a fluid passage 277′ radially inward through the fluid directing structure into the interior 274′. In this configuration, each combustor 240 c includes a solid outer wall 297 that has a continuous surface such that no fluid passes radially through it. A cap 251 c is provided on each combustor 240 c to fluidly seal the upstream end of the tube 242 closer to the turbine 200 such that air and/or the fuel/air mixture cannot axially enter the passage 274′ of the combustor 240 c, i.e., the air and/or fuel mixture must pass radially inward through the fluid directing structure 248′ and into the interior passage 274′. The downstream end of the annular passage 277′ is sealed by a cap 257 a which ensures that all the air (or fuel-air mixture) travels into the combustion passage 274′.
Air exiting the compressor 230 is distributed amongst the combustors 240 c. The air is mixed with fuel delivered by the fuel pipe 254 c and is ultimately swirled and burned in the inner combustion chamber 274′. Several methods and apparatus for injecting fuel into the burner 240 c are illustrated in FIG. 10. A fuel pipe 254 c is shown in solid and, in the solid configuration, fuel is injected upstream of the combustor 240 c where it is fully mixed with air delivered by the compressor 230 as described in connection with FIGS. 7, 8A and 8B. This fully mixed fuel/air charge then enters the region 277′ and travels into the combustion passage 274′ via ports 248 formed in the tubular member 242′. As explained earlier, the ports are arranged to cause rotation of the fuel/air mixture in the combustion passage 274′.
In an alternate embodiment, each combustor 240 c utilizes the fuel/air delivery system described in connection with FIGS. 5 and 6A. A fuel pipe 254 c′ includes a pre-mix chamber 254″. In this configuration, the fuel being delivered by the fuel pipe 254 c′ is partially mixed with air received by the pre-mix chamber 254″ from the compressor 230. This partial fuel mixture is injected into the chamber 274′ through the cap 251 c where it fully mixed with compressor air D6 that enters the chamber 274′ via the passage 277′ and then the ports 248 formed in the tubular member 242′.
In still another embodiment, the combustors 240 c utilize the fuel/air delivery system described in connection with FIGS. 1 and 2A. In this configuration, the fuel is injected directly into the combustion passage 274′ via the fuel pipe 254 c, the downstream end of which extends thought the cap 251 c. The injected fuel is mixed with the swirling air delivered through the tubular member 242′.
In all of these embodiments, an igniter (not shown) within the interior 274′ of the tube member 242′ of each combustor 240 c ignites the swirling air/fuel mixtures. The swirling combustion products collectively exit the combustors 240 c and pass through the turbine 220, causing rotation of the turbine and expulsion of the combustion products from the jet engine 200 c.
The combustor of the present invention for use in a jet engine is advantageous over conventional combustors or burners for several reasons. Unlike conventional combustors in which the flame is propagated primarily by molecular conduction of heat and molecular diffusion of radicals from the flame into the approaching stream of reactants, i.e., the air/fuel mixture, the combustor of the present invention forces, additional heat transfer by convection and radiation from the high velocity flame envelope overlaying and intermixing with the incoming air/fuel mixture. The incoming air/fuel mixture is pre-heated while the flame zone is being cooled, which advantageously helps to reduce NO_x. Radicals are also forced into the incoming reactant stream by the overlaying and intermixing flame envelope. The presence of radicals in a mixture of reactants lowers the ignition temperature and allows the fuel to burn at lower than normal temperature. It also helps to significantly increase flame speed, which shortens the reaction time, thereby additionally reducing NO_xformation while significantly improving flame stability/flame retention. The improved stability and flame retention reduces the chances of flame out.
Due to the exceptional flame retention/stability of the combustor of the present invention, it is capable of running at very high combustion loadings. High loadings allow the burner to run in a stable “lifted flame” mode i.e., the flame is spaced from the combustor surfaces. Lifting of the flame in this manner is desirable in that the combustor surfaces are not directly heated, thereby maintaining the surfaces at a lower temperature and lengthening the usable life of the combustor. A high combustion loading also allows the use of a smaller, space saving, and less costly combustor for a given application. Furthermore, the combustor of the present invention, due to the exceptional flame retention as discussed above, is also capable of operating cleanly (low CO) at very high levels of excess air, which produces NOx levels well below those achievable with conventional combustors.
The preferred embodiments of the invention have been illustrated and described in detail. However, the present invention is not to be considered limited to the precise construction disclosed. For example, it will be understood that any of the combustors described above may incorporate a “variable volume” combustion chamber, e.g., fluid passage, by configuring the wall 251 c (shown in FIG. 9) secured to the inner and outer tubes to be movable along the axis of the jet engine. Such a construction would allow for optimized combustion performance by matching the combustion chamber volume to the power output required.
The invention has been described in detail in connection with a jet engine application. Those skilled in the art will recognize that the principles of this invention may be applied to burners used in heating appliances such as hot water tanks, furnaces and boilers. Those skilled in the art will recognize that the disclosed burner configurations can be adapted for use in the identified heating applications. For some applications, the burner would be configured as a power burner in which a blower or the suitable device would force air into the burner where it would be mixed with the suitable liquid fuel such as fuel oil or a gaseous fuel such as natural gas or propane.
Various adaptations, modifications and uses of the invention may occur to those skilled in the art to which the invention relates and the intention is to cover hereby all such adaptations, modifications, and uses which fall within the spirit or scope of the appended claims.

Claims

Having described the invention, the following is claimed:

1. A jet engine comprising:

a housing having a first end and a second end and an interior passage that extends from the first end to the second end;

a compressor positioned within the first end of the interior passage;

a turbine positioned within the second end of the interior passage; and

a combustor positioned within the interior passage between the compressor and the turbine, the combustor extending along a central axis and comprising:

an outer tube having an outer surface and an inner surface defining a passage;

an inner tube positioned within the passage of the outer tube and having an outer surface and an inner surface defining an interior, wherein a fluid passage is defined between the outer surface of the inner tube and the inner surface of the outer tube, the fluid passage being supplied with a mixture of air and combustible fuel, the inner tube and the outer tube having fluid directing structure for causing the mixture of air and combustible fuel within the fluid passage to rotate radially about the central axis.

2. A combustor for a jet engine, said jet engine having a compressor portion and a turbine portion, the combustor comprising:

a) an outer tube having a central axis, said outer tube extending longitudinally and positioned to receive air discharged by said compressor portion and said outer tube having an outer surface and an inner surface;

b) an inner tube positioned within said outer tube, said inner tube having an outer surface spaced from said inner surface of said outer tube, thereby defining a combustion chamber passage therebetween;

c) said outer tube including fluid directing structure for communicating at least some of the air discharged by said compressor portion into said combustion chamber passage, said air being directed in a direction offset from said central axis, thereby causing rotation of said air about said central axis;

d) at least one fuel supply member for supplying a fuel to said combustion chamber passage in order to form a rotating fuel air mixture in said combustion chamber passage.

3. The combustor of claim 2 wherein said inner tube includes associated fluid directing structure for communicating air discharged by said compressor portion to said combustion chamber passage, said associated fluid directing structure directing said air in a direction that is offset from said central axis.

4. The combustor of claim 1 wherein said fuel member communicates with said combustion chamber passage and directly supplies fuel to said combustion chamber passage where it is mixed with said compressor air to form a rotating combustible fuel/air mixture.

5. The combustor of claim 2 wherein said fuel member premixes said fuel with some compressor air and then supplies said premixed fuel and air to said combustion chamber passage where it is mixed with the rotating compressor air in said combustion chamber passage.

6. The apparatus of claim 2 wherein said fuel member discharges fuel into a stream of air discharged by said compressor and flowing towards said outer tube, said fluid directing structure of said outer tube communicating both fuel and compressor air to said combustion chamber passage.

7. The apparatus of claim 1 wherein an axis of said inner tube and said central axis of said outer tube are coincident.

8. The apparatus of claim 7 wherein said axes of said inner and outer tubes are also coincident with a rotational axis of said compressor portion.

9. A combustor for a jet engine, said jet engine having a compressor portion and a turbine portion, the combustor comprising:

a) a tube having a central axis, the tube being located intermediate said compressor portion and said turbine portion, said tube having an outer surface and an inner surface;

b) fluid directing structure formed on said tube including passages extending from said outer surface to said inner surface;

c) said inner surface of said tube defining a combustion chamber;

d) a passage communicating air discharged by said compressor portion with said outer surface of said tube for delivering compressor air to said combustion chamber through said fluid directing structure, said fluid directing structure directing said compressor air at an angle offset from said central axis, thereby causing rotation of said compressor air in said combustion chamber;

e) a fuel member for supplying fuel to said combustion chamber.

10. The apparatus of claim 9 wherein a spaced apart continuous wall surrounds said tube, thereby defining at least a portion of said passage for communicating air to said outer surface of said tube.

11. The apparatus of claim 10 wherein said jet engine includes a plurality of said combustors spatially arranged around an axis of rotation defined by said compressor portion.

12. The apparatus of claim 2 wherein said rotating fuel air mixture is substantially completely combusted in said combustion chamber passage.

13. The combustor of claim 2, wherein the fluid directing structure includes a plurality of openings and a guide associated with each opening, the guides being angled relative to the tube surface for radially rotating the mixture about the central axis.

14. The fuel burner of claim 13, wherein the guides are arranged in a series of rows that extends around the periphery of the outer tube.

15. The combustor of claim 2, wherein the fluid directing structure includes a series of steps formed into the outer tube, the steps including openings for directing the air into the combustion chamber passage to rotate the mixture radially about the central axis.

16. The combustor of claim 15, wherein each step has an L-shape including a first member and a second member including the openings for directing the air such that the openings of one step direct the air across the adjoining step to impart rotation to the mixture.

17. The combustor of claim 2, wherein the fluid directing structure includes a plurality of openings that each extend from the outer surface of the outer tube to the inner surface; each opening extending through the outer tube at an angle relative to an axis extending normal to the outer surface of the inner tube and through the central axis.

18. The combustor of claim 17, wherein the outer tube includes a plurality of second openings that each extend from the outer surface of the outer tube to the inner surface in a direction extending to the central axis.

19. The combustor of claim 2, wherein the outer tube is formed as a series of overlapping arcuate plates that define the fluid directing structure, each plate having a corrugated profile having a series of passages through which the air is directed into the combustion chamber passage.

20. The combustor of claim 19, wherein the corrugated profile includes a plurality of alternating peaks and valleys.

21. The combustor of claim 20, wherein the overlapping plates are longitudinally and radially offset from one another such that the peaks of one plate are positioned between the peaks of adjacent plates.

22. The combustor of claim 19, wherein each plate directs the air in a direction that extends substantially parallel to the adjoining plate to impart rotation to the mixture.

23. The combustor of claim 3, wherein the inner tube includes a first that communicates with air discharged by said compressor portion and a second end having an end wall for closing the second end of the inner tube in a gas-tight manner, such that said associated fluid directing structure provides the only fluid path to said combustion chamber passage for said air received by said inner tube from said compressor portion.

24. The combustor of claim 2, wherein the rotating mixture is radially layered within the combustion chamber passage.

25. A method for combusting fuel in a jet engine having compressor and turbine portions, comprising the steps of:

a) providing a tube having an outer surface communicating with air discharged by said compressor portion and an inner surface at least partially defining a combustion chamber;

b) providing fluid directing structure between said inner and outer surfaces for communicating said compressor air from said outer surface to said combustion chamber, at an angle offset with respect to a central axis of said tube, such that said air is caused to rotate within said combustion chamber;

c) supplying fuel to said combustion chamber to thereby provide a swirling fuel/air mixture;

d) at least partially combusting said fuel air mixture in said combustion chamber;

e) supplying said combusted fuel/air mixture to said turbine portion.

26. The method of claim 25 further comprising the step of providing an inner tube within said outer tube such that said combustion chamber is defined between an outer surface of said inner tube and an inner surface of said outer tube.

27. The method of claim 26 further comprising the step of directing compressor air from an inner surface of said inner tube to an outer surface of said inner tube through associated fluid directing structure that imparts rotation to said compressor air as it travels into said combustion chamber.