This disclosure relates to the field of heat exchangers. More particularly, this disclosure relates to systems which incorporate a combustion chamber and a heat exchanger.
It is known to provide systems, such as heat engines (e.g. gas turbines), which include a combustion chamber in which fuel is burnt to generate hot gas and a heat exchanger, such as a recuperator used to recover energy from exhaust gas and thereby increase the efficiency of the heat engine. Measures which can increase the efficiency of a heat engine and/or reduce the size and/or weight of a heat engine are advantageous.
At least some embodiments of the present disclosure provide apparatus comprising:
a combustion chamber wall enclosing a combustion chamber; and
a heat exchanger integral with at least a portion of said combustion chamber wall;
wherein the heat exchanger and the combustion chamber wall are formed together as one entity from a single body of material; and
wherein said heat exchanger transfers heat from a hot gas to a cold gas and comprises a plurality of hot gas conduits to direct hot gas along respective hot gas paths, and a plurality of cold gas conduits to direct cold gas along respective cold gas paths;
wherein one or more of:
(i) at least some of said cold gas conduits directly connect to respective inlet openings in said combustion chamber wall;
(ii) at least some of said cold gas conduits directly connect to one or more cold gas plenums abutting said combustion chamber wall and plenum-inlet openings provide flow paths for said cold gas between respective ones of said one or more cold gas plenums and said combustion chamber; and
(iii) said combustion chamber wall is porous and said cold gas passes from at least some of said cold gas conduits into said combustion chamber through porous openings in said combustion chamber wall.
The present disclosure recognizes that increases in thermal efficiency and reductions in the size and mass of a system may be achieved, at least in some embodiments, when a heat exchanger is integrally formed with at least a portion of a combustion chamber wall. The heat exchanger and the combustion chamber wall are formed together as one entity, such as being formed together with the same material in an additive manufacturing process whereby the combustion chamber wall and the heat exchanger comprise a single body of material. Such an arrangement permits a more compact design and allows better heat transfer between the heat exchanger and the combustion chamber, as may be desired.
Whilst the combustion chamber can have a wide variety of different forms, in at least some embodiments of the disclosure the combustion chamber has a primary combustion chamber inlet and an combustion chamber outlet with a primary fluid flow path extending between the primary combustion chamber inlet and the combustion chamber outlet. A fuel and air mixture to be combusted may flow along this primary fluid flow path.
The heat transfer between the heat exchanger and the combustion chamber may be improved, and the combined apparatus made more compact, when the heat exchanger at least partially surrounds the combustion chamber in planes normal to at least a portion of the primary fluid flow path. Thus, the heat exchanger will at least partially wrap around the combustion chamber.
In some embodiments of the disclosure, the heat exchanger may fully surround the combustion chamber in planes normal to at least a portion of the primary fluid flow path. For example, if the combustion chamber has the form of an approximate cylinder with the fluid flow path extending along the axis of the cylinder, then the heat exchanger may have an annular cross section surrounding the combustion chamber. The portion of the primary fluid flow path for which the heat exchanger partially or fully surrounds the combustion chamber may in some embodiments extend along the entirety of the primary fluid flow path thereby increasing the amount of heat transfer possible between the heat exchanger and the combustion chamber wall, and accordingly the combustion gases within the combustion chamber.
The heat exchanger may serve to transfer heat from a hot gas to a cold gas and accordingly include a plurality of hot gas conduits to direct hot gas along respective hot gas paths and a plurality of cold gas conduits to direct cold gas along respective cold gas paths. Heat exchange between a hot gas and a cold gas flowing along respective conduits can provide efficient heat transfer.
In some embodiments the hot gas paths may flow away from the combustion chamber and the cold gas paths flow toward the combustion chamber and substantially parallel with the hot gas paths. Such an arrangement tends to locate the hottest of the hot gas close to the combustion chamber and the hottest of the cold gas closest to the combustion chamber in a manner which increases the efficiency with which heat may be transferred. Such an arrangement provides counterflow heat exchange between the hot gas and the cold gas.
In other possible example embodiments, the hot gas paths may cross to the cold gas paths as they pass through the heat exchanger in a way which provides a cross-flow type of heat exchanger. Such an arrangement may be preferred in embodiments in which simplicity of manifolding to route the hot gas and the cold gas are priorities.
Heat transfer between the hot gas and the cold gas may be improved in efficiency and the material requirements of the heat exchanger reduced when the hot gas conduits and the cold gas conduits share at least some conduit boundary walls.
In some example embodiments the cold gas from the cold gas conduits may be introduced into the combustion chamber through the combustion chamber wall. For example, the cold gas may be air which is pre-heated within the heat exchanger before it is introduced and forms part of the combustion process taking place within the combustion chamber. In this context, the cold gas conduits may connect/communicate with the combustion chamber in a variety of different ways. These different ways of connecting the cold gas conduits to the combustion chamber may be used separately or in combination with a given embodiment.
Some of the cold gas conduits may directly connect to respective inlet openings within the combustion chamber wall. Other of the cold gas conduits may directly connect to one or more cold gas plenums which adjoin the combustion chamber wall and themselves have plenum-inlet openings which provide flow paths for the cold gas between the cold gas plenums and the combustion chamber.
It is also possible that the combustion chamber wall may be formed so as to be porous rather than having particular and specific openings therein such that cold gas from the cold gas conduits may pass into the combustion chamber through porous openings in the combustion chamber wall. Such a porous combustion chamber wall may form one wall of, for example, a plenum holding cold gas and connected to one or more cold gas conduits within the heat exchanger.
In addition to providing cold gas through the combustion chamber wall, at least some of the cold gas conduits may serve to provide a portion of the cold gas to the primary combustion chamber inlet. By directing different portions of the cold gas through respective cold gas conduits a predictable and accurate division of the flow of cold gas may be achieved with a particular desired proportion of that cold gas being fed in by the primary combustion chamber inlet and another specific portion or portions being fed into the combustion chamber through the combustion chamber wall in a controlled manner through other of the cold gas conduits.
The ability to evenly direct the hot gas through the hot gas conduits may be improved by the use of one or more inner hot gas plenums proximal to the combustion chamber to supply hot gas to the hot gas conduits and one or more outer hot gas plenums distal from the combustion chamber for collecting the hot gas from the hot gas conduits. Such an arrangement enhances the evenness with which the hot gas is flowed through the hot gas conduits and ensures that the hottest of the hot gas is close to the combustion chamber wall in a manner which increases heat transfer.
The combustion chamber may also be supplied with fuel through one or more fuel conduits. The fuel within the fuel conduits may be pre-heated using the heat exchanger integrally formed with the combustion chamber wall such as by one or more of: using hot gas conduits proximal to the fluid conduits; using cold gas conduits (still containing gas which will typically be hotter than the fuel) close to the fuel conduits; and by directly absorbing heat from the body of the heat exchanger itself. The fuel conduits may supply fuel directly to the primary combustion chamber inlet.
The shapes of the paths followed by the hot gas conduits and the cold gas conduits can vary. In some embodiments, respective ones of the hot gas conduits and the cold gas conduits follow involute paths that are an involute of an outer cross sectional boundary of the combustion chamber wall in a cross sectional plane containing the corresponding involute path. Such an arrangement allows the hot gas conduits and the cold gas conduits to be packed closely together and to have a constant, or substantially constant, cross sectional area along their length in a manner suited to efficient operation.
While the cross sectional boundary from which the involute paths are drawn, and in which plane they lie could take a variety of different forms. This outer cross sectional boundary may conveniently be circular and perpendicular to the primary flow path in the case of a combustion chamber in the form of a cylinder.
Whilst a wide variety of different relationships are possible in the disposition of the hot gas conduits and the cold gas conduits, in at least some embodiments efficient heat transfer may be promoted when these are interleaved around the combustion chamber.
In some embodiments, the hot gas conduits have cross sectional areas normal to the hot gas paths that are greater than the cross sectional areas of the cold gas conduits normal to the cold gas paths. Providing larger cross sectional areas for the hot gas paths relative to the cold gas paths increases the efficiency with which the heat transfer may be achieved as the hot gas is typically less dense than the cold gas and accordingly requires larger conduits for the same mass flow.
The inlets through which the cold gas may be supplied into the combustion chamber may be formed so as to direct the cold gas to flow with a mean direction that is non-normal to the combustion chamber wall in a manner which tailors the introduction of the cold gas into the combustion chamber at specific points to the requirements of those specific points. For example, the combustion chamber inlet openings proximal to the primary combustion chamber may direct the cold gas to enter the combustion chamber with a mean flow direction rotating around the primary flow path in a manner which supports and enhances the generation of a stable vortex airflow within the combustion gas helping to provide consistent and thorough combustion. Other combustion chamber inlet openings proximal to the combustion chamber outlet may serve to direct the cold gas to enter the combustion chamber with a mean flow direction having a component parallel with and in the same direction as the primary flow path which may assist in helping to provide a layer of relatively cool gas close to the combustion chamber wall thereby separating the combustion chamber wall from the hottest of the combustion gasses in a manner which reduces the erosion of the combustion chamber wall. Other of the combustion chamber inlets at an intermediate position along the primary flow path direct the cold gas to enter the combustion chamber with a mean flow direction having a component parallel with and opposite from the primary flow path in a manner which enhances the mixing of such cold gas with the combustion gasses from the primary inlet.
Whilst the combustion chamber wall and the heat exchanger may be formed in a variety of different ways, such as casting, in at least some embodiments the apparatus is formed of consolidated powder material, such as may be used in additive manufacturing processes, e.g. energy beam melted metal powder consolidated to form the combined combustion chamber wall and heat exchanger.
While the heat exchanger may serve a variety of different thermodynamic roles within the system, in at least some embodiments the heat exchanger may be a recuperator serving to transfer heat from waste exhaust gases into cold gas which is to be combusted within the system.
Such a recuperator may be advantageously used within the context of a turbine driven by the combustion gas from the combustion chamber to produce exhaust gas which is the hot gas of a recuperator serving to receive cold gas from a compressor driven by the turbine and to transfer heat from the hot gas in to the cold gas which is to be supplied to the combustion chamber.
The apparatus can be formed by additive manufacture. In additive manufacture, an article may be manufactured by successively building up layer after layer of material in order to produce an entire article. For example the additive manufacture could be by selective laser melting, selective laser centring, electron beam melting, etc. The material used for the heat exchanger and combustion chamber wall can vary, but in some examples may be a metal, for example aluminium, titanium or steel or could be an alloy. The additive manufacture process may be controlled by supplying an electronic design file which represents characteristics of the design to be manufactured, and inputting the design file to a computer which translates the design file into instructions supplied to the manufacturing device. For example, the computer may slice a three-dimensional design into successive two-dimensional layers, and instructions representing each layer may be supplied to the additive manufacture machine, e.g. to control scanning of a laser across a powder bed to form the corresponding layer. Hence, in some embodiments rather than providing a physical apparatus, the technique could also be implemented in a computer-readable data structure (e.g. a computer automated design (CAD) file) which represents the design of an apparatus as discussed above. Thus, rather than selling the apparatus in its physical form, it may also be sold in the form of data controlling an additive manufacturing machine to form such an apparatus. A storage medium may be provided storing the data structure. The storage medium may be a non-transitory storage medium.
Example embodiments will now be described, by way of example only, with reference to the accompanying drawings in which:
Fuel is passed through a fuel conduit 10 to the primary combustion chamber inlet 6. The fuel is expelled through a nozzle 12 into the combustion chamber where it is mixed with cold gas (air) which has passed through the recuperator and been heated by hot gas, which is also passed through the recuperator. Some of the cold gas is introduced through a cold gas conduit 14 directly into the primary combustion chamber inlet 6. This cold gas may pass through vanes which impart a rotating motion about the primary flow path. The fuel from the nozzle 12 mixed with this cold gas and burned (combusted). The combustion gas follows a vortex (swirling) path within a central portion of the combustion chamber toward to the combustion chamber outlet 8.
Further cold gas conduits 16 within the recuperator pass cold gas directly into the combustion chamber through inlets 18 within the combustion chamber wall 4. These inlets may be directed such that they impart a mean flow direction to the cold gas entering the combustion chamber with a component of motion which rotates around the primary flow path. This rotational motion of the cold gas introduced through the conduits 18 is used to support the swirling motion imparted to the cold gas introduced through the primary combustion chamber inlet 6 and help to maintain a stable vortex within which the fuel is combusted.
There are further cold gas conduits 20 within the recuperator which pass cold gas into cold gas plenums 22 which border (adjoin/abut) the combustion chamber wall 4. Openings within the combustion chamber wall 4 which connect to the cold gas plenums allow cold gas to enter the combustion chamber via the cold gas plenums 22. These outlets within the combustion chamber wall 4 which connect to the cold gas plenums 22 can have shapes which serve to direct the cold gas passing therethrough to have a mean flow direction in a particular direction. More particularly, the openings in the wall of the cold gas plenum 22 proximal to the combustion chamber outlet 8 may direct the cold gas to enter with a component of its mean flow direction parallel with and in the same direction as the primary flow path. This cold gas will have a component which is perpendicular to the primary flow path, but nevertheless the majority of its flow direction may be parallel with the combustion chamber wall 4 as illustrated in
At a location intermediate the combustion chamber outlet 8 and the primary combustion chamber inlet 6 one or more cold gas plenums 22 have outlets which direct the cold gas to provide a degree of backflow as illustrated in
As shown in
The recuperator includes hot gas conduits 26 which pass between an inner hot gas plenum 28 and an outer hot gas plenum 30. The hot gas, which may be exhaust gas from a turbine, enters the inner hot gas plenum 28 and flows radially outwardly through the hot gas conduits 26 from which it is collected into the outer hot gas plenum 30 before exiting the recuperator. In this way, the hot gas with the highest temperature is located within the inner hot gas plenum 28 which is closest to the combustion chamber, thereby tending to increase the amount of heat energy maintained within the combustion chamber.
One or more of the hot gas conduits 32 is directed to pass proximal to the fuel conduit 10 and accordingly serves to preheat (e.g. turn into gaseous form) the fuel before it reaches the nozzle 12. In other embodiments, one or more of the cold gas conduits 14, 16, 20 may be routed to be proximal to the fuel conduit 10 to preheat the fuel, or in other embodiments sufficient heat may be conducted through the body of the combined recuperator and combustor to heat the fuel within the fuel conduit 10 to the required degree.
As illustrated in
The combined recuperator and combustor illustrated in
A feature of such additively manufactured structures is that it is possible to form such structures in a way in which the material is porous to gaseous flow. Thus, for example, some of the openings in the combustion chamber wall 4 through which cold gas flows may instead (or additionally) be provided by porous openings through a porous portion of the combustion chamber wall 4. As an example, the protective cool boundary layer of cold gas introduced proximal to the combustion chamber outlet 8 may be provided by cold gas flowing through a porous combustion chamber wall bounding the cold gas plenum 22 near the combustion chamber outlet 8 instead of passing through specific openings in the cold gas plenum 22 in that region.
As previously discussed above, the cold gas flowing through the cold gas conduits 14, 16, 20 passes radially inwardly toward the combustion chamber whereas the hot gas passes radially outwardly away from the combustion chamber. This arrangement provides counterflow between the cold gas and the hot gas. The section through the combined recuperator and combustor shown in
The cold gas conduits 14, 16, 20 and the hot gas conduits 26 may share boundary walls along at least a portion of their lengths in order to reduce the amount of material required to build the combined recuperator and combustor as well as to improve the heat transfer efficiency. The interleaving of the cold gas conduits 14, 16, 20 and the hot gas conduits 26 facilitates such boundary wall sharing.
The illustration of
In the examples illustrated herein the combustion chamber is of a substantially cylindrical shape and accordingly has a circular cross section. The involute paths of the conduits accordingly are an involute of a circle. However, it will be appreciated that the combustion chamber can have shapes other than that of a cylinder and in such cases the conduits can follow involute paths that are an involute of an outer cross sectional boundary of the combustion chamber wall 4 which is other than circular, e.g. elliptical. The involute paths in the examples illustrated herein lie in a plane which is perpendicular to the primary flow path through the combustion chamber. However, it is possible that these involute paths could lie in a plane which is not perpendicular to such a primary flow path and yet still meet the requirements of the involute geometry and provide closely packed and substantially constant cross sectional area conduits.
In the example of
The examples of the recuperators shown in
Example arrangements of the present technique are set out below in the following clauses:
(1) Apparatus comprising:
a combustion chamber wall enclosing a combustion chamber; and
a heat exchanger integral with at least a portion of said combustion chamber wall.
(2) Apparatus according to clause (1), wherein said combustion chamber has a primary combustion chamber inlet and a combustion chamber outlet, and a primary fluid flow path extends between said primary combustion chamber inlet and said combustion chamber outlet.
(3) Apparatus according to clause (2), wherein said heat exchanger at least partially surrounds said combustion chamber in planes normal to at least a portion of said primary fluid flow path.
(4) Apparatus according to clause (3), wherein said heat exchanger fully surrounds said combustion chamber in said planes.
(5) Apparatus according to any one of clauses (3) and (4), wherein said portion comprises all of said primary fluid flow path.
(6) Apparatus according to any one of clauses (4) and (5), wherein said combustion chamber wall has a circular cross section in a plane normal to said primary fluid flow path and said heat exchanger has an annular cross section in said plane normal to said primary fluid flow path.
(7) Apparatus according to any one of clauses (1) to (6), wherein said heat exchanger transfers heat from a hot gas to a cold gas and comprises:
a plurality of hot gas conduits to direct hot gas along respective hot gas paths; and
a plurality of cold gas conduits to direct cold gas along respective cold gas paths.
(8) Apparatus according to clause (7), wherein said hot gas paths flow away from said combustion chamber and said cold gas paths flow toward said combustion chamber and are substantially parallel with said hot gas paths.
(9) Apparatus according to clause (7), wherein said hot gas paths are substantially perpendicular to said cold gas paths.
(10) Apparatus according to any one of clauses (7), (8) and (9), wherein said plurality of hot gas conduits and said plurality of cold gas conduits share at least some conduits boundary walls.
(11) Apparatus according to clause (8), wherein said plurality of hot gas conduits and said plurality of cold gas conduits are disposed within said heat exchanger to provide counterflow between said hot gas and said cold gas.
(12) Apparatus according to any one of clauses (7) to (11), wherein one or more of:
a turbine to extract energy from combustion gas from said combustion chamber and to exhaust said hot gas; and
a compressor to compress said cold gas for supply to said combustion chamber, wherein said recuperator is configured to transfer heat from said hot gas leaving said turbine to said cold gas for supply to said combustion chamber.
(26) Apparatus according to any one of the preceding clauses comprising a removable combustion chamber liner disposed between said combustion chamber wall and said combustion chamber.
Number | Date | Country | Kind |
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1616210.9 | Sep 2016 | GB | national |
Filing Document | Filing Date | Country | Kind |
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PCT/GB2017/052385 | 8/14/2017 | WO | 00 |