Heat exchanging apparatus

Abstract

A heat exchanging apparatus for a gas turbine engine. The heat exchanging apparatus comprises a first end (5, fig 4a), a second end 8, and a plurality of radially offset portions 13 extending between

Description

FIELD AND BACKGROUND

[0001] The present invention is concerned with a heat exchanging apparatus. The heat exchanging apparatus may be used in aerospace applications such as gas turbine engines. Alternatively, the invention may be used in other applications where a high heat transfer is desired with a relatively low component weight. For example, the heat exchanging apparatus may also be used in land, marine, industrial or other applications.

[0002] In conventional gas turbine engines, 50% or more of the energy contained in the core engine gas flow is discharged into the environment. Furthermore, existing gas turbine engines have large carbon dioxide and nitrous oxide emissions and also lead to the formation of harmful contrails. To address these issues, a concept has been developed for incorporation into existing gas turbine engines. The concept comprises a heat exchanging apparatus which vaporises water using the heat from the engine exhaust gas. The water input into the heat exchanging apparatus is extracted from the exhaust gas using a condenser. The vaporised water is expanded in a steam turbine, to extract most of its energy, and then the remaining low energy steam is routed to the combustor.

[0003] Significant advantages are achieved by using a heat exchanging apparatus in this way. By recovering more of the exhaust heat for vaporising the water, the thermal efficiency of the engine is increased. Furthermore, the carbon dioxide and nitrous oxide emissions are reduced and contrail formation minimised by injecting the vaporised water into the combustion part of the engine.

[0004] The present inventors have developed a new heat exchanging apparatus which is suitable for integrating with a jet engine. This approach enables energy to be more efficiently captured and emissions and contrail formations to be reduced. The present invention therefore enhances the performance and efficiency of jet engines. The heat exchanging can also be used in a number of other applications.

[0005] The skilled reader will be familiar with the operation and construction of a gas turbine engine. However, to summarise the operation, a typical engine comprises one or more compressors, namely a first upstream low pressure compressor and a second, downstream, high pressure compressor. The compressors compress air entering the air intake of the engine before the compressed gas is communicated into the combustors where fuel is introduced and combusted with the compressed air.

[0006] An invention described herein is concerned with a heat exchanger suitable for a gas turbine engine and its installation in a gas turbine engine. As would be understood by the skilled person, the invention is not limited to use in gas turbine engines. For example, the heat exchanging apparatus of the present invention may be used in other areas of aerospace, industrial applications or in other transportation applications. SUMMARY

[0007] Particular aspects and embodiments are set out in the appended claims.

[0008] Viewed from a first aspect, there is provided a heat exchanging apparatus for a gas turbine engine. The heat exchanging apparatus comprises a first end, a second end, and a plurality of radially offset portions extending between the first and second ends, each portion comprising at least two radially offset rows of fluid passageways configured to transport fluid between the first end and the second end. Each portion is fixed at the first end and is axially moveable at the second end with respect to adjacent portions.

[0009] When integrated with a gas turbine engine, the heat exchanging apparatus is configured to heat fluid such as water using heat from the gas turbine engine exhaust gas. The portions, although fixed at the first end, are discrete and separate in that they are not connected to one another as they extend from the first end. In this way, and due to them being axially moveable at the second end, the separate portions can expand and the distal ends can move axially with respect to one another. Portions which are closer to the exhaust gases will be heated up more than those further from the exhaust gases and will therefore expand more and move further in the axial direction. Therefore, differential axial thermal expansion is enabled. In some examples, the portions may additionally be radially moveable at the second end due to thermal expansion. By splitting the apparatus into separate portions, the temperature differential across each portion is much smaller than if tubes across the entire heat exchanging apparatus were connected together. This means the differential expansion (in the axial direction) of the tubes at the inner and outermost radii is much smaller, so there is a much reduced impetus for distortion of the structure.

[0010] The fluid passageways may be in the form of tubes or pipes extending between the first and second ends and with gaps formed between them.

[0011] The heat exchanging apparatus may additionally comprise a plurality of connecting regions at the first end fluidly connecting radially adjacent portions. Specifically, fluid flowing into the connecting region will be able to travel into a radially adjacent row of fluid passageways through the connecting region. The use of a connecting region such as this enables a compact heat exchanging apparatus to be provided as it is not required to have bending pipes with a minimum bend radius. This enables more efficient heat transfer in a smaller area.

[0012] Each portion may comprise a manifold at the second end, wherein the manifold fluidly connects each of the at least two rows of the fluid passageways. The manifolds may be configured to receive fluid from a first of the two radially offset rows of fluid passageways and 3 may be configured to redirect the fluid into a second of the two radially offset rows of fluid passageways. As with the connecting region, the use of the manifold allow a compact heat exchanging apparatus to be provided. The mixing of the fluid in the connecting regions and manifolds helps solve the Ledinegg instability. If Ledinegg instability does occur, it will be limited to a single axial tube rather than a complete “pass” for a single tube across the entire heat exchanging apparatus, which would occur if the tubes were one long piece (as in a conventional shell-and-tube heat exchanger), and not fed into manifolds at the end of each pass.

[0013] In many types of conventional heat exchanger, for example shell-and-tube heat exchangers, pipes extend between a first and second end with the pipes being bent at either end to redirect the flow by 180 degrees. The requirement for this bend in the pipes prevents the pipes being located too close to one another. In the present invention, the use of the connecting regions at the first end and the manifolds at the second end removes the need for pipes or passageways with bends at either end. This allows a tighter packing of passageways or pipes per unit area leading to more efficient heat transfer. Furthermore, the manifolds enable blockages to be limited to a single tube. Specifically, if a passageway becomes blocked, fluid can be redistributed into adjacent parallel tubes such that fluid can still travel into the manifold in that portion through an adjacent passageway. Therefore, the mixing of the flow at each end allows a “blocked” tube to be bypassed, preserving function of the heat exchanging apparatus to a much greater degree than if a tube is blocked in a conventional heat exchanger.

[0014] The manifolds may be configured to receive fluid from a greater number of rows of fluid passageways than are configured to receive the redirected flow. This is enabled by the use of the manifold and multiple rows of passageways being fluidly connected with the manifold. The fact that the flow mixes into a manifold at the end of each segment means that there does not need to be a 1 -to-1 correspondence between the incoming and outgoing tubes. This provides the following significant advantages: Different (greater or fewer) numbers of fluid passageways can be used at adjacent radii, allowing for greater and more efficient tube packing densities. Different size tubes can be used at different radii as equally at the same radii, allowing for highly customised tube patterns to be developed. Largely arbitrary incoming and outgoing tube patterns become possible since there is no requirement for a hard correspondence between the incoming and outgoing tubes.

[0015] Ths manifolds may bs configured to rscsivs fluid from a smallsr numbsr of rows of fluid passageways than are configured to receive the redirected flow. The direction of flow in each row of passageways is dictated by the pressure difference between the connecting region at the first end and the manifold at the second end. If the pressure in all passageways are equal, then the flow will also be equal (i.e. will travel into the manifold and out of the manifold through the same number of passageways).

[0016] The fluid passageways in each row may be arranged in a staggered circumferential arrangement with respect to fluid passageways in adjacent rows. Specifically, each passageway may be circumferentially offset with respect to a passageway in a radially adjacent row. The staggered design is beneficial as it gives the most compact design which in turn results in the highest heat transfer. As the heat exchanger of the present invention may be wrapped around a gas turbine engine axis, all rows of passageways may not be staggered with respect to one another. However, by using the manifold design, the arrangement of the passageways can be controlled and the number and the diameters of the passageways in each row varied based on the application. This can be done to ensure that the rows of passageways are as staggered as possible with respect to one another. In other examples, rather than using a staggered design, the fluid passageways may be in line with those in adjacent rows.

[0017] The fluid may be configured to travel from the outer radial side of the heat exchanging apparatus to the inner radial side of the heat exchanging apparatus or from the inner radial side of the heat exchanging apparatus to the outer radial side of the heat exchanging apparatus. In the former configuration, cold fluid such as water is input into the heat exchanging apparatus at an outer radial side and the hot exhaust gas starts on the inner radial side and travels outwards. Therefore, a counter flow heat exchanger is provided. In the latter configuration, fluid such as water is input into the heat exchanging apparatus at an inner radial side on the same side as the hot exhaust gas. Thus, both the exhaust gas and the fluid to be heated start on the inner radial side and travel outwards. Therefore, a parallel flow heat exchanger is provided. The present invention may use a gas flow orthogonal to the flow in the fluid passageways. However, a collinear / coaxial flow could also be used either in the counter flow or parallel design.

[0018] The fluid passageways may be cylindrical. This enables a large surface area around the passageway circumference for heat transfer with the exhaust gas.

[0019] The diameter of each fluid passageway may vary with respect to its radial and / or circumferential position. As discussed above, by varying the diameter of the fluid passageways based on the position, the staggering of the adjacent rows of passageways can be ensured to increase the compactness of the heat exchanging apparatus.

[0020] The heat exchanging apparatus may be formed of a plurality of circumferentially distributed annular sectors. For example, the heat exchanging may be made up of twelve sectors. In other examples, greater or fewer sectors than this may be used. The number of sectors can be selected to optimize economy / service / inspections.

[0021] A radially extending gap may be formed between each sector. This is to enable circumferential expansion of the sectors upon heating. The size of the gap depends on the material (i.e. thermal expansion coefficient of the material) used for the construction of the sliding manifolds, and the temperatures the heat exchanging apparatus is exposed to. In other examples, there may be no gap between each sector. Instead, the sectors may be configured to expand radially outwards as they heat.

[0022] Each sector may be independently removable from the apparatus. Thus, each sector can be removed and replaced since each sector comprises its own set of sliding and fixed manifolds and passageways.

[0023] The first end of each portion may be fixed within a first frame portion by welding or brazing or by other means. The second end of each portion may be located and axially moveable within a second frame portion. The second end may also be radially moveable within the second frame portion. By positioning the second ends of each portion within the second frame portion, the movement of the second end of each portion is contained.

[0024] The interface between the portions at the second end may have a sinusoidal shape when viewed in cross section. This prevents circumferential sliding between adjacent manifolds and sections. Other designs of interface may be used. For example, the interface may have saw tooth or zig zag shapes. In other examples, the manifolds may have smooth interacting surfaces. By using interfaces such as sinusoidally shaped interfaces, the pipe packing density can be increased which increases the heat transfer per unit area.

[0025] A low friction material may be coated on the radially outer and inner sides of each portion to facilitate axial movement of the sections with respect to each other. This enables the manifolds to move axially with respect to one another. For example, a nickel-based coating may be used. In other examples, other materials may be used for the coating.

[0026] The heat exchanging apparatus may be at least two metres in length.

[0027] The fluid passageways may be spread circumferentially by a first distance and radially by a second distance. For example, the first distance may be larger or smaller than the second distance. These may be varied based on particular requirements of a particular heat exchanging apparatus. The passageways may be arranged as close as manufacturing allows in both the circumferential and radial directions in order to increase the compactness of the heat exchanger. However, it may be desirable to spread the passageways either radially or circumferentially in order to reduce flue gas pressure losses.

[0028] The portions may be made of different materials based on their radial position. For example, higher density materials may be used at the inner radial portion where the temperatures are higher and lower density materials may be used at the outer radial portions where the temperatures are lower. This can lead to an overall weight reduction of the heat exchanging apparatus which in turn can lead to fuel consumption savings when the heat exchanging apparatus is installed in an aeroplane. The portions may be formed of one or more of the following materials: Inconel 625 Inconel 718 - Titanium 64 Steel

[0029] Inconel-625 is beneficial as it works well in an 02-rich environment as well as with elevated temperatures.

[0030] The heat exchanging apparatus may further comprise a plurality of gas guide surfaces arranged to cause gas flow in a generally radial direction through the apparatus. Specifically, the gas guide surfaces or baffles are used to turn the exhaust gas flow from an axial to a radial direction. Thus, a cross-flow heat exchanger is formed.

[0031] The gas guide surfaces may be formed by a plurality of baffles. The baffles may be arranged orthogonal to the plurality of passageways. The baffles encourage the exhaust gas to flow across the heat exchanging apparatus.

[0032] The heat exchanging apparatus may further comprise guide vanes attached to the end of each baffle. The guide vanes may be curved in order to aid the turning of the flow of the gas from travelling along the length of the apparatus to traveling across the apparatus.

[0033] The heat exchanging apparatus may further comprise a perforated plate located on the side of the heat exchanging apparatus on which the heating gas is flowing. The perforated plate may be used in combination with the gas guide surfaces in addition to or instead of the guide vanes. Specifically, the heat exchanging apparatus may comprise the baffles in combination with the guide vanes and / or the perforated plate. The perforated plate may be in contact with the baffles or the guide vanes.

[0034] The perforated plate may comprise a plurality of openings, wherein the openings may vary in size from a first size at a first end of the plate adjacent to the first end of the heat exchanging apparatus to a second size smaller than the first size at a second end of the plate adjacent to the second end of the heat exchanging apparatus.

[0035] By using the perforated plate, the flow of the heating gas is balanced along the length of the heat exchanging apparatus. Due to the larger size of openings or perforations at the first end of the plate, the aerodynamic resistance to the flow is lower than at the second end of the plate. This assists to equalise the flow across the heat exchanger at each axial location along its (axial) length.

[0036] The perforated plate also serves the function of preventing high energy debris such as blades or parts of fractured blades (from the last stage of the turbine, earlier turbine stages or other sources upstream of the last low pressure turbine stage) from coming into contact with the plurality of passageways of the heat exchanger. Specifically, the openings in the perforated plate may be sized in order to prevent debris from passing through or in order to act as an obstruction to the debris in order to reduce its kinetic energy as it passes through the plate. In this way, when it does come into contact with the passageways of the heat exchanging apparatus, the kinetic energy of the debris is reduced and damage to the passageways is prevented. The material from which the perforated plate is made is chosen in order to withstand impact with the high energy debris. For example, the perforated plate may be made of Inconel 600 or high ductility steel.

[0037] According to a second aspect, there is provided a gas turbine engine comprising a turbine exhaust casing, a heat exchanging apparatus and a perforated plate located radially inwards of the heat exchanging apparatus. The perforated plate comprises a plurality of openings varying in size from a first size at a first end of the plate adjacent the turbine exhaust casing to a second size smaller than the first size at a second end of the plate distal from the exhaust casing.

[0038] By using the perforated plate, the flow of the exhaust gas is balanced along the length of the heat exchanging apparatus. Due to the larger size of openings or perforations at the first end of the plate, the aerodynamic resistance to the flow is lower than at the second end of the plate. This assists to equalise the flow across the heat exchanger at each axial location along its (axial) length.

[0039] The perforated plate also serves the function of preventing high energy debris such as blades or parts of fractured blades (from the last stage of the turbine, earlier turbine stages or other sources upstream of the last low pressure turbine stage) from coming into contact with the plurality of passageways of the heat exchanger. Specifically, the openings in the perforated plate may be sized in order to prevent debris from passing through or in order to act as an obstruction to the debris in order to reduce its kinetic energy as it passes through the plate. In this way, when it does come into contact with the passageways of the heat exchanging apparatus, the kinetic energy of the debris is reduced and damage to the passageways is prevented. The material from which the perforated plate is made is chosen in order to withstand impact with the high energy debris. For example, the perforated plate may be made of Inconel 600 or high ductility steel.

[0040] According to a third aspect, there is provided a gas turbine engine comprising a heat exchanging apparatus as set out in the first aspect. By recovering more of the exhaust heat for vaporising the water, the thermal efficiency of the engine is increased. Furthermore, the carbon dioxide and nitrous oxide emissions are reduced and contrail formation minimised by injecting the vaporised water into the combustion part of the engine. Thus, a gas turbine engine is provided with reduced emissions and with greater thermal efficiency.

[0041] When incorporated in a gas turbine engine, the heat exchanging apparatus vaporises water using the heat from the engine exhaust gas. The water input into the heat exchanging apparatus is extracted from the exhaust gas using a condenser. The vaporised water is injected into the combustion part of the engine via a steam turbine. The steam turbine is attached to the low pressure shaft of the engine. By first injecting the steam into the turbine, the previously lost heat energy is returned back into the engine as “shaft power”. This results in the increase of the thermal efficiency of the cycle and the reduction of specific fuel consumption (SFC).

[0042] After the steam has been reused in the steam turbine, this lower energy steam is then injected into the combustor, where it leads to a reduction in NOx and CO2 emissions and contrail production.

[0043] According to a fourth aspect, there is provided a heat exchanging apparatus comprising a first end, a second end, and a plurality of laterally spaced portions extending between the first and second ends, each portion comprising at least two laterally offset rows of fluid passageways configured to transport fluid between the first end and the second end. Each portion is fixed at the first end and is moveable at the second end with respect to adjacent portions along their direction of extension between the first and second end.

[0044] The term ‘lateral’ is intended to mean a direction perpendicular to the extension direction of the portions extending between the first and second ends. The term ‘extension direction’ is intended to mean the direction along which the passageways extend between the first and second end. The portions, although fixed at the first end, are discrete and separate in that they are not connected to one another as they extend from the first end. In this way, and due to them being moveable at the second end along their extension direction, the separate portions can expand and the distal ends can move with respect to one another. Portions which are heated to higher temperatures will therefore expand more and move further in their extension direction. Therefore, differential thermal expansion is enabled. In some examples, the portions may additionally be laterally moveable (i.e. perpendicular to the extension direction) at the second end due to thermal expansion. By splitting the apparatus into separate portions, the temperature differential across each portion is much smaller than if tubes across the entire heat exchanging apparatus were connected together.

[0045] The fluid passageways may be in the form of tubes or pipes or tubes extending between the first and second ends and with gaps formed between them.

[0046] The heat exchanging apparatus may additionally comprise a plurality of connecting regions at the first end fluidly connecting radially adjacent portions. Specifically, fluid flowing into the connecting region will be able to travel into a laterally adjacent row of fluid passageways through the connecting region. The use of a connecting region such as this enables a compact heat exchanging apparatus to be provided as it is not required to have bending pipes with a minimum bend radius. This enables more efficient heat transfer in a smaller area.

[0047] Each portion may comprise a manifold, wherein the manifold fluidly connects each of the at least two rows of the fluid passageways. The manifolds may be configured to receive fluid from a first of the two laterally offset rows of fluid passageways and may be configured to redirect the fluid into a second of the two laterally offset rows of fluid passageways. As with the connecting region, the use of the manifold allow a compact heat exchanging apparatus to be provided. The mixing of the fluid in the connecting regions and manifolds helps solve the Ledinegg instability. If Ledinegg instability does occur, it will be limited to a single axial tube rather than a complete “pass” for a single tube across the entire heat exchanging apparatus, which would occur if the tubes were one long piece (as in a conventional shell-and-tube heat exchanger), and not fed into manifolds at the end of each pass.

[0048] In many types of conventional heat exchanger, for example shell-and-tube heat exchangers, pipes extend between a first and second end with the pipes being bent at either 10 end to redirect the flow by 180 degrees. The requirement for this bend in the pipes prevents the pipes being located too close to one another. In the present invention, the use of the connecting regions at the first end and the manifolds at the second end removes the need for pipes or passageways with bends at either end. This allows a tighter packing of passageways or pipes per unit area leading to more efficient heat transfer. Furthermore, the manifolds enable blockages to be limited to a single tube. Specifically, if a passageway becomes blocked, fluid can be redistributed into adjacent parallel tubes such that fluid can still travel into the manifold in that portion through an adjacent passageway. Therefore, the mixing of the flow at each end allows a “blocked” tube to be bypassed, preserving function of the heat exchanging apparatus to a much greater degree than if a tube is blocked in a conventional heat exchanger.

[0049] The manifolds may be configured to receive fluid from a greater number of rows of fluid passageways than are configured to receive the redirected flow. This is enabled by the use of the manifold and multiple rows of passageways being fluidly connected with the manifold. The fact that the flow mixes into a manifold at the end of each segment means that there does not need to be a 1 -to-1 correspondence between the incoming and outgoing tubes. This provides the following significant advantages: Different (greater or fewer) numbers of fluid passageways can be used at adjacent lateral positions, allowing for greater and more efficient tube packing densities. Different size tubes can be used at different lateral positions as equally at the same lateral positions, allowing for highly customised tube patterns to be developed. Largely arbitrary incoming and outgoing tube patterns become possible since there is no requirement for a hard correspondence between the incoming and outgoing tubes.

[0050] The manifolds may be configured to receive fluid from a smaller number of rows of fluid passageways than are configured to receive the redirected flow. The direction of flow in each row of passageways is dictated by the pressure difference between the connecting region at the first end and the manifold at the second end. If the pressure in all passageways are equal, then the flow will also be equal (i.e. will travel into the manifold and out of the manifold through the same number of passageways).

[0051] The fluid passageways in each row may be arranged in a staggered arrangement with respect to fluid passageways in adjacent rows. Specifically, each passageway may be offset with respect to a passageway in a laterally adjacent row. The staggered design is beneficial as it gives the most compact design which in turn results in the highest heat transfer. By using the manifold design, the arrangement of the passageways can be controlled and the 11 number and the diameters of the passageways in each row varied based on the application. This can be done to ensure that the rows of passageways are as staggered as possible with respect to one another. In other examples, rather than using a staggered design, the fluid passageways may be in line with those in adjacent rows.

[0052] The heat exchanging apparatus may function as a counter flow or a parallel flow heat exchanger. Specifically, a heat source such as a stream of hot gas may enter the apparatus from the opposite side to that which the fluid in the fluid passageways enters the heat exchanging apparatus. Therefore a counter flow heat exchanger is formed. Alternatively, the heat source and the fluid to be heated may be added from the same side to from a parallel flow heat exchanger. The present invention may use a gas flow orthogonal to the flow in the fluid passageways. However, a collinear / coaxial flow could also be used either in the counter flow or parallel design.

[0053] The fluid passageways may be cylindrical. This enables a large surface area around the passageway circumference for heat transfer with the heat source.

[0054] The diameter of each fluid passageway may vary with respect to its lateral position. As discussed above, by varying the diameter of the fluid passageways based on the position, the staggering of the adjacent rows of passageways can be ensured to increase the compactness of the heat exchanging apparatus.

[0055] The first end of each portion may be fixed within a first frame portion by welding or brazing or by other means. The second end of each portion may be located and axially moveable within a second frame portion. The second end may also be radially moveable within the second frame portion. By positioning the second ends of each portion within the second frame portion, the movement of the second end of each portion is contained.

[0056] The interface between the portions at the second end may have a sinusoidal shape when viewed in cross section. This prevents circumferential sliding between adjacent manifolds and sections. Other designs of interface may be used. For example, the interface may have saw tooth or zig zag shapes. In other examples, the manifolds may have smooth interacting surfaces. By using interfaces such as sinusoidally shaped interfaces, the pipe packing density can be increased which increases the heat transfer per unit area.

[0057] A low friction material may be coated on the radially outer and inner sides of each portion to facilitate axial movement of the sections with respect to each other. This enables the manifolds to move axially with respect to one another. For example, a nickel-based coating may be used. In other examples, other materials may be used for the coating.

[0058] The heat exchanging apparatus may be at least two metres in length.

[0059] The fluid passageways may be spread by a first direction by first distance and a second direction perpendicular to the first direction by a second distance. For example, the first distance may be larger or smaller than the second distance. These may be varied based on particular requirements of a particular heat exchanging apparatus. The passageways may be arranged as close as manufacturing allows in both the first and second directions in order to increase the compactness of the heat exchanger.

[0060] The heat exchanging apparatus may further comprise a plurality of gas guide surfaces arranged to cause gas flow through the apparatus to cause an increase in temperature.

[0061] The gas guide surfaces may be formed by a plurality of baffles. The baffles may be arranged orthogonal to the plurality of passageways. The baffles encourage the gas to flow across the heat exchanging apparatus.

[0062] The heat exchanging apparatus may further comprise guide vanes attached to the end of each baffle. The guide vanes may be curved in order to aid the turning of the flow of the gas from the axial direction to the radial direction.

[0063] The heat exchanging apparatus may further comprise a perforated plate located radially inwards of the heat exchanging apparatus. The perforated plate may be used in combination with the gas guide surfaces in addition to or instead of the guide vanes. Specifically, the heat exchanging apparatus may comprise the baffles in combination with the guide vanes and / or the perforated plate. The perforated plate may be in contact with the baffles or the guide vanes.

[0064] The perforated plate may comprise a plurality of openings, wherein the openings may vary in size from a first size at a first end of the plate adjacent to the first end of the heat exchanging apparatus to a second size smaller than the first size at a second end of the plate adjacent to the second end of the heat exchanging apparatus.

[0065] By using the perforated plate, the flow of the heating gas is balanced along the length of the heat exchanging apparatus. Due to the larger size of openings or perforations at the first end of the plate, the aerodynamic resistance to the flow is lower than at the second end of the plate. This assists to equalise the flow across the heat exchanger at each axial location along its (axial) length.

[0066] The perforated plate also serves the function of preventing high energy debris such as blades or parts of fractured blades from coming into contact with the plurality of passageways of the heat exchanger. Specifically, the openings in the perforated plate may be sized in order to prevent debris from passing through or in order to act as an obstruction to the debris in order to reduce its kinetic energy as it passes through the plate. In this way, when it does come into contact with the passageways of the heat exchanging apparatus, the kinetic energy of the debris is reduced and damage to the passageways is prevented. The material from which the perforated plate is made is chosen in order to withstand impact with the high energy debris. For example, the perforated plate may be made of Inconel 600 or high ductility steel.

[0067] Other aspects will also become apparent upon review of the present disclosure, in particular upon review of the Brief Description of the Drawings, Detailed Description and Claims sections. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Examples of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

[0069] Figure 1 shows a turbine exhaust casing of a gas turbine engine according to the present invention with a heat exchanging apparatus installed in an annular sector;

[0070] Figure 2 shows a cross sectional view of the turbine exhaust casing of the gas turbine engine according to the present invention with the heat exchanging apparatus installed in an annular sector;

[0071] Figures 3A and 3B show a perforated plate for incorporating with the heat exchanging apparatus;

[0072] Figure 4A shows a radially cross sectional view of a first end of the heat exchanging portion;

[0073] Figure 4B shows an axially cross sectional view of the annular sector of the heat exchanging apparatus;

[0074] Figure 4C shows a radially cross sectional view of a second end of the heat exchanging apparatus;

[0075] Figure 5 shows a schematic drawing of the heat exchanging apparatus and the movement of fluid within it; and

[0076] Figure 6 shows a cross sectional view of a portion of the annular sector of the heat exchanging apparatus.

[0077] While the disclosure is susceptible to various modifications and alternative forms, specific example approaches are shown by way of example in the drawings and are herein described in detail. It should be understood however that the drawings and detailed description attached hereto are not intended to limit the disclosure to the particular form disclosed but rather the disclosure is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the claimed invention.

[0078] As used in this specification, the words “comprises”, “comprising”, and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean “including, but not limited to”. It will be recognised that the features of the above-described examples of the disclosure can conveniently and interchangeably be used in any suitable combination. It will also be recognised that the invention covers not only individual embodiments but also combinations of the embodiments that have been discussed herein. DETAILED DESCRIPTION

[0079] The present invention is concerned with a heat exchanging apparatus. This may be used in, for example, a gas turbine engine, industrial applications, marine applications, or other applications.

[0080] The figures show the heat exchanging apparatus integrated with a gas turbine engine. The skilled person would understand that the heat exchanging apparatus could equally be installed in the applications discussed above. Figure 1 shows a gas turbine engine exit or turbine exhaust casing (TEC) 1 of a gas turbine engine according to the present invention. An elongate body 20 extends axially aft of the TEC and is centred on the axis of the gas turbine engine. The turbine exhaust casing 1 comprises a heat exchanging apparatus 2 located to the rear of the turbine exhaust casing 1 and coaxial with the elongate body 20. The heat exchanging apparatus 2 is integrated with the engine and configured to be attached to an aeroplane wing pylon with a frame 3.

[0081] The heat exchanging apparatus 2 in figure 1 is shown as an annular sector 4. A single annular sector is shown. When installed in the turbine exhaust casing 1, a plurality of annular sectors 4 are arranged around the circumference of elongate body 20, downstream of the turbine exhaust casing 1. In another example not shown in the figures, the sectors 4 may have flat rather than curved outer surfaces. In this way, when arranged around the machine axis, a polygonal rather than annular shape is formed.

[0082] A gap may be formed between adjacent sectors to allow room for circumferential expansion on heating. In other examples, the heat exchanging apparatus 2 may extend around the entire circumference of the turbine exhaust casing 1 in a continuous ring. Located radially outwards of the heat exchanging apparatus 2 is a condenser 16. The condenser 16 extracts water from the gas turbine exhaust gas and the extracted water is fed into the heat exchanging apparatus 2 by a pump (not shown). The condenser is 16 fluidly connected to the heat exchanging apparatus 2 by ducting 18.

[0083] Figure 2 shows a cross sectional view of the turbine exhaust casing 1 according to the present invention with the heat exchanging apparatus 2 installed. Fluid, for example water, enters a first end 5 of the heat exchanging apparatus 2 through an inlet pipe 6 at an outer radial side. The water travels axially along the heat exchanging apparatus 2 through fluid passageways 7. At a second end 8 of the heat exchanging apparatus 2, the flow is redirected by 180° back towards the first end. The flow continues traveling in this back and forth motion until it reaches the inner radial side of the heat exchanging apparatus 2. At this point, the fluid leaves the heat exchanging apparatus 2 through an outlet pipe 9.

[0084] The number of rows of passageways is chosen based on a number of factors. As the fluid passes through the tubes, it loses energy (pressure) through friction with the pipe walls, so the greater the number of rows, the greater the pressure drop of the fluid will be. The number of rows will therefore be chosen based on a limit on the allowable pressure drop and pump sizing to overcome these frictional losses.

[0085] The heat exchanging apparatus 2 additionally comprises a plurality of baffles 10a and curved guide vanes 10b connected to the baffles 10a. The combination of the baffles 10a and guide vanes act 10b as gas guide surfaces which cause exhaust gas from the turbine exhaust casing 1 to be redirected from flowing in a generally axial direction to flow in a generally radial direction through the heat exchanging apparatus 2. These baffles 10a and guide vanes 10b are also visible in figure 1.

[0086] In other examples, a perforated plate 19 may be incorporated radially inwards of the heat exchanging apparatus 2. This is shown in figures 3A and 3B. The plate therefore effectively covers the exhaust gas inlet to the heat exchanging apparatus 2. Thus, when viewed from the turbine exhaust casing looking aft down the axis, the plate 19 forms an arc. Figure 3A shows the plate 19 in a 2-dimensions and figure 3B shows the plate 19 in 3-dimensions. The perforated plate 19 comprises a plurality of openings 21 which extend through the plate 19. As can be seen in figure 3B, the plate 19 can be hollow. In other examples, the plate 19 may be solid with the openings 21 running from its upper surface to its lower surface. The diameter of the openings 21 varies along the length of the plate 19. Specifically, the diameter of the openings 21 at a first end 22 is greater than those at a second end 23. Figures 3A and 3B show the plate 19 having various sections each having openings 21 with different diameters. In other examples, the diameter of the openings 21 may vary continuously from the first end to the second end. The perforated plate 19 may be used in combination with the baffles 10a and in addition to or instead of the guide vanes 10b.

[0087] The exhaust gases cause the heat exchanging apparatus 2 to increase in temperature. In the present example, the heat exchanging apparatus 2 is designed as a vaporiser. Thus, as the fluid moves through the heat exchanging apparatus 2, it is vaporised into a gas. Therefore, when the fluid leaves the heat exchanging apparatus 2 through the outlet pipe 9, it is in a gaseous form. At this point, the vaporised water is injected into a steam turbine attached to the low pressure shaft of the engine. Thus, thermal energy is returned to the engine as shaft power. In other examples, the invention may function as a single phase heat exchanging apparatus. When used in this way, the fluid is not vaporised but remains in liquid form as it is heated.

[0088] Figure 4A shows a zoomed in cross sectional view of the first end 5 of the heat exchanging portion 2. The first end 5 comprises a plurality of connecting portions 11. The connecting portions 11 connect radially adjacent fluid passageways 7 to enable the fluid to be redirected at the first end 5. The fluid passageways 7 are fixed at the first end 5 of the heat exchanging apparatus 2 for example by welding or brazing within a first frame portion 12.

[0089] Figure 4B shows an axially cross sectional view of the annular sector of the heat exchanging apparatus 2. As can be seen from this figure, the heat exchanging apparatus 2 comprises a number of rows of fluid passageways 7. At the outer radial side of the heat exchanging apparatus 2, there are a greater number of fluid passageways 7 in each row than at an inner radial side of the heat exchanging apparatus 2. The fluid passageways 7 in each row are arranged in a staggered arrangement with respect to fluid passageways 7 in radially adjacent rows. In other examples, rather than having more fluid passageways 7 in each row at the outer radial side of the heat exchanging apparatus 2, the diameter of the fluid passageways 7 may be larger.

[0090] Although not shown in this figure, the heat exchanging apparatus 2 comprises a plurality of radially offset portions 13 extending between the first end 5 and second end 8, each portion 13 comprising at least two radially offset rows of fluid passageways 7 configured to transport fluid between the first end 5 and the second end 8.

[0091] Figure 4C shows a zoomed in cross sectional view of the second end 8 of the heat exchanging apparatus 2. Each radially offset portion 13 comprises a manifold 14. In the present example, the manifold 14 fluidly connects four rows of fluid passageways 7. Fluid enters the manifold 14 through one or more of the rows of fluid passageways 7 and leaves the manifold 14 through one or more of the rows of fluid passageways 7. For example, the fluid may enter the manifold 14 through the top two rows, each at different radii and leave through the bottom two rows, also at different radii. By pumping the fluid through two rows of passageways rather than one, the pressure drop across the pipes is reduced which in turn leads to a reduction in power consumption of the pump. For example, fluid may enter the manifold 14 through the top row and be redirected back towards the first end 5 of the heat exchanging apparatus 2 through the other three rows.

[0092] In the present example, fluid enters the manifold 14 through two rows of inlet passageways 7a and leaves the manifold by two rows of outlet passageways 7b. By having this set up, flow enters the manifold from two rows of passageways 7 at different radii and flow leaves the manifold in two rows of passageways 7 at different radii. This enables the flow area both in and out of the manifold to be doubled which reduces the pressure drop in the water circuit. However, in other examples, there may be more or fewer rows of fluid passageways in each manifold. For example, the manifolds may have one row of passageways 7 bringing fluid into the manifold and one row of passageways transporting it away from the manifold. In other examples, each section may have six rows of passageways 7, with three bringing fluid in and three taking the fluid away from the manifold.

[0093] The manifolds 14 are located within a second frame portion 15. The ends of the fluid passageways 7 and their respective manifolds 14 are axially moveable within the second frame portion 15. For example, the ends of the fluid passageways may be moveable within the second frame portion 15 by up to 25 mm. In other examples, the ends may be moveable more or less than this, depending on the material from which the passageways are formed which affects their coefficient of thermal expansion and the temperatures involved. When exhaust gas is leaving the turbine exhaust casing 1, the inner radial side of the heat exchanging apparatus 2 will heat up much more than the outer radial side. The temperature differential will cause the fluid passageways 7 on the inner radial side to axially expand more than the fluid passageways 7 on the outer radial side. Thus, since the manifolds 14 are moveable within the second frame portion 15, they are able to axially shift as a result of this expansion. As the radially offset portions 13 are not fixed at the second end 8, the axial movement can be different based on the radial position of the respective portion.

[0094] As can be seen from figure 4C, the ends of the interface between the portions 13 at the second end has a sinusoidal shaped interface 17 when viewed in cross section. The use of the sinusoidal shaped interface 17 prevents relative movement between the sliding manifolds in the circumferential direction. There may be a low friction material located between the portions 13 so that they can move axially with respect to each other as the portions 13 slide axially relative to one another. Furthermore, the sliding manifolds 14 in the frame 15 are also able to move radially within the frame 15 sufficiently to reduce any forces generated on the adjacent radial sectors as a result of internal fluid pressure, in each manifold, as well as thermal expansion in the radial direction, of each manifold.

[0095] Figure 5 shows a schematic drawing of the heat exchanging apparatus 2 and the movement of fluid within it Arrows show the fluid travelling into the apparatus 2, being redirected in a manifold 8 at the second end before being redirected in the connecting region 11 at the first end. The figure also shows the axial sliding motion of radially offset adjacent portions 13 with respect to one another. Specifically, the upper portion 13 in this figure may slide to a lesser extent that the lower portion 13 if the hot exhaust gas is entering from the bottom of the figure as the lower portion 13 will be heated and will therefore expand more than the upper portion 13. The figure shows the length of the heat exchanging apparatus 2 being 2.3 metres. In other examples it may be longer or shorter than this. For example, it may be at least 2 metres.

[0096] Figure 6 shows a cross sectional view of a portion 13 of the annular sector of the heat exchanging apparatus 2. This portion has two rows of fluid passageways 7. The sinusoidal upper and lower surface can also be seen from this figure. Rather than using sinusoidal shaped interfaces, in some locations, the surfaces may be curved or cylindrical.

[0097] The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only, and are not exhaustive and / or exclusive. It is to be understood that advantages, embodiments, examples, functions, features, structures, and / or other aspects described herein are not to be considered limitations on the scope of the invention as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilised and modifications may be made without departing from the spirit and scope of the claimed invention. Various embodiments of the invention may suitably comprise, consist of, or consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc., other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future.

Claims

1. A heat exchanging apparatus for a gas turbine engine comprising:a first end;a second end; anda plurality of radially offset portions extending between the first and second ends, each portion comprising at least two radially offset rows of fluid passageways configured to transport fluid between the first end and the second end,wherein each portion is fixed at the first end and is axially moveable at the second end with respect to adjacent portions.

2. The heat exchanging apparatus of claim 1, additionally comprising a plurality of connecting regions at the first end fluidly connecting radially adjacent portions.

3. The heat exchanging apparatus of claims 1 or 2, wherein each portion comprises a manifold at the second end, wherein the manifold fluidly connects each of the at least two rows of the fluid passageways.

4. The heat exchanging apparatus of claim 3, wherein the manifolds are configured to receive fluid from a first of the two radially offset rows of fluid passageways and are configured to redirect the fluid into a second of the two radially offset rows of fluid passageways.

5. The heat exchanging apparatus of claim 4, wherein the manifolds are configured to receive fluid from a greater number of rows of fluid passageways than are configured to receive the redirected flow.

6. The heat exchanging apparatus of claim 4, wherein the manifolds are configured to receive fluid from a smaller number of rows of fluid passageways than are configured to receive the redirected flow.

7. The heat exchanging apparatus of any of claims 1 to 6, wherein an outer radial side of the heat exchanging apparatus comprises more fluid passageways around its circumference than an inner radial side.

8. The heat exchanging apparatus of claim 7, wherein the fluid passageways in each row are arranged in a staggered circumferential arrangement with respect to fluid passageways in adjacent rows.

9. The heat exchanging apparatus of any preceding claim wherein the first of the two radially offset rows of fluid passageways is located radially outwards of the second of the two radially offset rows of fluid passageways such that the fluid is configured to travel from the outer radial side of the heat exchanging apparatus to the inner radial side of the heat exchanging apparatus.

10. The heat exchanging apparatus of any of claims 1 to 8, wherein the first of the two radially offset rows of fluid passageways is located radially inwards of the second of the two radially offset rows of fluid passageways such that the fluid is configured to travel from the inner radial side of the heat exchanging apparatus to the outer radial side of the heat exchanging apparatus..

11. The heat exchanging apparatus of any of claims 1 to 10, wherein the fluid passageways are cylindrical.

12. The heat exchanging apparatus according to claim 11, wherein the diameter of each fluid passageways varies with respect to its radial and / or circumferential position.

13. The heat exchanging apparatus of any preceding claim being formed of a plurality of circumferentially distributed annular sectors.

14. The heat exchanging apparatus of claim 13 being formed of twelve sectors.

15. The heat exchanging apparatus of claim 13 or 14, wherein a radially extending gap isformed between each sector.

16. The heat exchanging apparatus of any preceding claim, wherein the first end of each portion is fixed within a first frame portion.

17. The heat exchanging apparatus of any preceding claim, wherein the second end of each portion is located and axially moveable within a second frame portion.

18. The heat exchanging apparatus of any preceding claim, wherein the interface between the portions at the second end has a sinusoidal shape when viewed in cross section19. The heat exchanging apparatus of any preceding claim, wherein a low friction material is coated on the radially outer and inner sides of each portion to facilitate axial movement of the sections with respect to each other.

20. The heat exchanging apparatus of any preceding claim, wherein the fluid passageways are spread circumferentially by a first distance and radially by a second distance.

21. The heat exchanging apparatus of claim 20, wherein the first distance is larger than the second distance.

22. The heat exchanging apparatus of claim 20, wherein the first distance is smaller than the second distance.

23. The heat exchanging apparatus of any preceding claim, wherein the portions are made of different materials based on their radial position.

24. The heat exchanging apparatus of claim 13, wherein each sector is independently removable from the apparatus.

25. The heat exchanging apparatus of any preceding claim further comprising a plurality of gas guide surfaces arranged to cause gas flow in a generally radial direction through the apparatus.

26. The heat exchanging apparatus of claim 25, wherein the gas guide surfaces are formed by a plurality of baffles.

27. The heat exchanging apparatus of claim 26, wherein guide vanes are attached to the end of each baffle.

28. The heat exchanging apparatus of claim 26 or 27, wherein a perforated plate is located radially inwards of the heat exchanging apparatus, wherein the perforated plate comprises a plurality of openings, wherein the openings vary in size from a first size at a first end of the plate adjacent to the first end of the heat exchanging apparatus to a second size smaller than the first size at a second end of the plate adjacent to the second end of the heat exchanging apparatus.

29. A gas turbine engine comprising a heat exchanging apparatus as claimed in claims 1 to 28.

30. A gas turbine engine comprising:a turbine exhaust casing;a heat exchanging apparatus; anda perforated plate located radially inwards of the heat exchanging apparatus and comprising a plurality of openings varying in size from a first size at a first end of the plate adjacent the turbine exhaust casing to a second size smaller than the first size at a second end of the plate distal from the exhaust casing.

31. A heat exchanging apparatus comprising:a first end;a second end; anda plurality of laterally spaced portions extending between the first and second ends, each portion comprising at least two laterally offset rows of fluid passageways configured to transport fluid between the first end and the second end,wherein each portion is fixed at the first end and is moveable at the second end with respect to adjacent portions along their direction of extension between the first and second end.

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