GB2455532A - Rotary gas heat exchanger - Google Patents

Rotary gas heat exchanger Download PDF

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Publication number
GB2455532A
GB2455532A GB0724213A GB0724213A GB2455532A GB 2455532 A GB2455532 A GB 2455532A GB 0724213 A GB0724213 A GB 0724213A GB 0724213 A GB0724213 A GB 0724213A GB 2455532 A GB2455532 A GB 2455532A
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United Kingdom
Prior art keywords
matrix
housing
assembly
ducts
entry
Prior art date
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Application number
GB0724213A
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GB0724213D0 (en
Inventor
Thomas Tsoi-Hei Ma
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Individual
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Individual
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Publication date
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Priority to GB0724213A priority Critical patent/GB2455532A/en
Publication of GB0724213D0 publication Critical patent/GB0724213D0/en
Publication of GB2455532A publication Critical patent/GB2455532A/en
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D19/00—Regenerative heat-exchange apparatus in which the intermediate heat-transfer medium or body is moved successively into contact with each heat-exchange medium
    • F28D19/04—Regenerative heat-exchange apparatus in which the intermediate heat-transfer medium or body is moved successively into contact with each heat-exchange medium using rigid bodies, e.g. mounted on a movable carrier
    • F28D19/041—Regenerative heat-exchange apparatus in which the intermediate heat-transfer medium or body is moved successively into contact with each heat-exchange medium using rigid bodies, e.g. mounted on a movable carrier with axial flow through the intermediate heat-transfer medium
    • F28D19/042—Rotors; Assemblies of heat absorbing masses
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
    • F02M26/22—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
    • F02M26/40—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with timing means in the recirculation passage, e.g. cyclically operating valves or regenerators; with arrangements involving pressure pulsations
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
    • F23L15/00—Heating of air supplied for combustion
    • F23L15/02—Arrangements of regenerators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D19/00—Regenerative heat-exchange apparatus in which the intermediate heat-transfer medium or body is moved successively into contact with each heat-exchange medium
    • F28D19/04—Regenerative heat-exchange apparatus in which the intermediate heat-transfer medium or body is moved successively into contact with each heat-exchange medium using rigid bodies, e.g. mounted on a movable carrier
    • F28D19/047—Sealing means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D21/00—Heat-exchange apparatus not covered by any of the groups F28D1/00 - F28D20/00
    • F28D21/0001—Recuperative heat exchangers
    • F28D21/0003—Recuperative heat exchangers the heat being recuperated from exhaust gases
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

Abstract

A rotary gas heat exchanger 16 comprises a housing 14 having entry 22, 24, 26, 28 and exit 22', 24', 26' ducts, a rotating matrix 10 with through flow passages 11 supported for rotation within the housing 14 via a central shaft 12 passing through the matrix 10, perforated end plates 6 mounted on the shaft 12 and located at each end of the matrix 10 whereby a clearance gap 2 is provided between the end plates 6 and the housing 14, and a mesh 4 of resilient material sandwiched between each end plate 6 and the ends of the rotating matrix 10 to seal off a pattern of rows of the flow passages 11 at the ends of the matrix 10. Resilient mesh 4 may have links (4a, fig 3) so that it resembles a wheel with spokes and may be secured to the end plates 6 by compression or by an adhesive. Perforations in the end plates 6 may be slot openings (8, fig 4) that may be tapered in a direction through each plate 6. Ring sleeves (6a, fig 6) extending from the end plates 6 may engage axially with the matrix 10 via o-rings (9) so that the matrix 10 is supported axially and laterally by resilient material. The heat exchanger 16 may be connected to a supercharged 124 or turbocharged internal combustion engine 100, or to gas turbines, Stirling engines and other industrial plants.

Description

ASSEMBLY OF A ROTARY GAS AND/OR HEAT EXCHANGER
Field of the invention
The present invention relates to an assembly of a rotary gas exchanger, a rotary heat exchanger, or a combined rotary gas and heat exchanger.
Background of the invention
GB852204 and GB1136122 provide teaching in the gas sealing system of a rotary heat exchanger or regenerator.
The heat exchanger comprises a housing having inlet and outlet apertures for the heat exchange gases and a flow guiding matrix which is rotatable in the housing and through which the gases can flow. A sealing means is necessary to prevent leakage of the gases between the end faces of the rotating matrix and the adjacent end walls of the housing.
In GB852204, the sealing gap is supported by a bearing race and maintained substantially constant while the bearing assembly could move as an integral unit with any thermal expansion or mechanical vibration between the rotating matrix and the housing.
In GB1l36l22, the sealing means is a controlled gap of less than half the hydraulic diameter of the flow guiding channels of the matrix. Because of differential thermal expansion, this gap could vary, increasing leakage if the gap increases, and risking contact causing damage of the fragile matrix if the gap closes. To minimise the change in the width of the gap, both the housing and the matrix are made of ceramic material of similar thermal expansion.
Recent examples of applications of a rotary heat exchanger used as an EGR cooler for cooling recirculated exhaust gases fed through the gas exchanger into the intake system of a reciprocating internal combustion engine may be found in EP1586842 and US6161528 where special attention has been paid in the design of the rotating matrix and the clearance of the sealing gap between the end faces of the matrix with the adjacent end walls of the housing in order to withstand the exhaust gas pressure and air blower pressure connected to the gas exchanger. In US6161528, the sealing means is a spring-loaded contact sliding member of solid lubricating material which does not damage the fragile matrix but the contact pressure could cause friction and wear and increase the power requirement for driving the rotating matrix.
GB2428465 describes a rotary gas exchanger used as an EGR dispenser in a reciprocating internal combustion engine for metering some exhaust gases from the exhaust system of the engine and transferring the gases to the intake system of the engine by lateral displacement of sealed gas columns within the rotary gas exchanger. In this case, the effectiveness of the end seals in the rotating matrix becomes even more important which is specifically mentioned, quote: "A very small minimum clearance is maintained between the end faces of the rotating matrix butting with the end walls of the housing in order to stop to all intents and purposes any gas leakage at the perimeters of the entry and exit ducts and to maintain different gas pressures within each set of ducts". However, no detail is given in how the very small minimum clearance could be achieved during assembly and how this clearance could be maintained in use under high thermal load conditions.
GB2438274 describes a similar EGR dispenser with the addition of an integrated EGR cooler. The requirement for effective gas seals between the rotating matrix and the end walls of the housing will be the same as in GB2428465.
It is mentioned in GB2428465 that the walls of the flow guiding passages in the matrix may be constructed of thin foils of stainless steel or extruded ceramic in a honeycomb structure akin to that of the substrate of a catalytic converter commonly used in the automotive exhaust system.
Such a substrate would have been ideal for use in the rotary gas exchanger because of the relatively low cost due to high volume production for automotive applications. However the dimensional tolerance is poor though adequate for its original application but falls far short of the micron level accuracy needed for use in the rotary gas exchanger. It is impractical to apply additional machining to the substrate to produce better dimensional accuracy because of the very fragile nature of the material. There are also difficulties in mounting the substrate for rotation and maintaining micron level accuracy in the assembly and alignment of the matrix within the housing in order to achieve the required minimum clearance for effective sealing of the gases.
Apart from the difficulties in achieving the precise clearance during assembly of the rotating matrix, there are further difficulties in maintaining a stable clearance after assembly when the exchanger is in use under high thermal loads and mechanical vibration conditions. Differential thermal expansion and mechanical movements between the matrix and the housing could cause the clearance to change substantially, but there is as yet rio reliable proposal in the prior art that could offer a satisfactory solution.
Aim of the invention The present invention aims to mitigate all the above problems during assembly and in use, and proposes to include a matrix of low dimensional accuracy in the assembly of a rotary gas and/or heat exchanger.
Summary of the invention
According to the present invention, there is provided an assembly of a rotary gas and/or heat exchanger comprising a housing with entry and exits ducts and a rotor supported for rotation within the housing, the rotor further comprising a central shaft, two perforated end plates mounted rigidly to the shaft at a precise distance apart between the outward facing end surfaces of the plates for the rotor to fit within the housing with a precise clearance from the end walls of the housing, and a matrix structure of thin-walled flow passages from one end of the matrix to the other end mounted axially for rotation and resiliently between the two rigidly mounted end plates with the central shaft passing through it, characterised in that the mounting of the matrix is achieved during assembly by bringing the end plates and the matrix towards each other and sandwiching a web-like mesh of resilient material between each inward facing surface of the plate and outward facing surface of the matrix for the mesh to come to firm contact with the matrix and seal off a pattern of continuous rows of flow passages at the end surface of the matrix thereby sub-dividing the through-flow cross-section of the matrix into a plurality of separate bunches of flow passages, each bunch connected through the perforated end plates to the entry and exit ducts of the housing as the rotor rotates.
Preferably, the web-like mesh is secured by compression of the mesh between the end plates. Alternatively, an adhesive may be used to secure the mesh between the end plate and the matrix. As a further alternative, the web-like mesh may be produced in situ by injecting a liquid adhesive on one of the component parts before assembly which sets to form a resilient seal after assembly.
The assembled rotor will be mounted for rotation within the housing with a precise clearance between the end plates of the rotor and the end walls of the housing formed by the boundary walls of the entry and exit ducts emerging at the internal end faces of the housing, the ends of these walls co-operating with the ends of the rotor to produce the precise clearance as the rotor rotates.
Preferably, the perforations in the end plates are slots openings spaced between the links of the web-like mesh of resilient material. This makes the end plate resembling a wheel with spokes connected to a central shaft. The sides of the spokes support the web- like mesh and provide the gripping torque for holding the matrix and rotating it at the same speed as the plate, while the spaces between the spokes (i.e. the slot openings) allow gas flow through the sub-divided bunches of flow passages in the matrix to connect with the entry and exit ducts in the housing. The outward facing surfaces of the spokes define a very small and precise clearance with the end walls of the housing, thus forming an effective gas seal to stop to all intents and purposes any gas leakage at the perimeters of the entry and exit ducts and to maintain different gas pressures within the different sets of ducts, as stipulated in GB2428465.
In order to avoid short-circuiting of gases between the adjacent ducts in the housing at the connection with each passing slot in the plate as the rotor rotates, it is important that the opening of each slot does not exceed the boundary of the partitioning wall separating the ducts and passed by the slot as the rotor rotates. This may be achieved by either selecting the thickness of the partitioning wall emerging at the internal end face of the housing to be greater than the width of the slot opening at the end face of the plate, or tapering each slot opening in the end plate in the direction through the plate from a wider opening at the side of the web-like mesh to a narrower opening at the side of the end clearance surface of the plate, not exceeding the thickness of the partitioning wall emerging at the internal end face of the housing passed by the slot as the rotor rotates.
In the invention, where the slot openings in the end plates match the cross-sections of the sub-divided bunches of flow passages in the matrix, there is no blocking of the passages because of the presence of the end plates. On the other hand, where the slot openings are tapered, there is some partial blocking of the flow passages but this could be minimised by smooth transition of the divergent opening of the slots towards the sub-divided bunches. In general, the presence of the end plates will not cause any additional restriction in the overall volumetric efficiency of the gas exchanger provided that the combined effective flow cross-section of all the slots passing within an entry or exit duct in the housing is the same as or greater than the respective supply or discharge flow cross-section of those ducts connecting with the exchanger.
The above assembly of the rotary gas and/or heat exchanger will function as a rotary gas dispenser having a plurality of dispensing volumes defined by the volume of each sub-divided bunch of flow passages, and as a rotary heat regenerator having a plurality of recuperative heat transfer elements defined by the surface area of each sub-divided bunch of flow passages.
Unique to the bunch concept of the present invention, the location of the slot openings in the end plates relative to the associated sub-divided bunches of flow passages is not important because as soon as a slot opening is exposed to gas flow, the gases will spread across the intervening space to fill all the flow passages within the bunch. Each slot opening and the associated bunch of flow passages will undergo the same filling processes as the slot passes the various entry and exit ducts in the housing. The time of exposure of each slot across a given set of entry and exit ducts determines the length of travel of the gases at a given mean velocity along all the flow passages in the bunch. Where there are many slots passing within a given set of entry and exit ducts, the volume flow through the ducts is shared by all these slot openings and the mean gas velocity through the slots is therefore reduced, which also reduces the length of travel of the gases along the bunches of flow passages in a given exposure time determined by the rotating speed of the rotor.
The matrix can have crude external dimensions and any misalignment in the assembly will be fully taken up by resilience of the mesh material (for example silicone rubber), while its function as a support structure for the flow guiding passages remains effective. Precise control of the end clearance between the rotor and the housing rests entirely on the precision machined components in the rotor and housing similar to a rotary air blower (for example the Roots blower) using established technology for manufacture and with proven reliability. The torque required for driving the rotor will be very low since no work is done on the working fluids and there is no touching contact between the rotor and the housing except at the bearings.
To assist assembly, the matrix is cylindrical in shape and hollow through its central axis. Each end plate has a ring sleeve extending from the inside face of the plate concentric with the central shaft to engage axially with the matrix and guide the matrix during assembly towards the end plate until it meets firmly with the web-like mesh which is sandwiched between. A resilient 0-ring between the sleeve and the matrix may be provided to cushion the assembly and position the matrix concentrically with the end plates.
Thus the matrix is fully supported axially and laterally by resilient material when assembled to the rotor and there is no area of the matrix that is highly stressed.
By the same token, any differential thermal expansion and mechanical movement between the matrix and the end plates of the rotor when the exchanger is in use will be safely absorbed by the resilient material of the web-like S mesh with little or no effect on the precise clearance between the end plates and the housing. Thus the rotary gas and/or heat exchanger of the present invention could be operated with a wide range of gas temperatures and still maintain a stable and precise clearance at the end faces of the rotor which is essential for effective sealing of the gases connected to the exchanger.
In a typical application of a rotary heat exchanger of the present invention for example in a gas turbine or Stirling engine, the housing has a first set of entry and exit ducts for the hot gases and a second set of entry and exit ducts for the cold gases, and the ratio of the flow cross-section areas of the ducts emerging at the internal end faces of the housing between the hot and cold sets of ducts is typically 1:1.
In a particular application of a rotary gas exchanger of the present invention used as an EGR dispenser in a reciprocating internal combustion engine according to GB2428465, the ducts in the housing comprise a first set of entry and exit ducts taking an engine exhaust gas stream from the engine through the housing and matrix towards the ambient atmosphere and a second set of entry and exit ducts taking an engine intake air stream from the ambient atmosphere through the housing and matrix towards the engine. The respective sets of ducts are disposed in the housing with the entry and exit ducts of each set opposite one another facing the ends of the rotating matrix and each set is positioned eccentrically to the axis of rotation of the matrix apart from and in rotational sequence with the other set.
In the above application, because the maximum power of the engine is directly related to the intake air pressure that is available in the intake system, it is important that the intake air flow through the matrix should encounter as low a pressure drop as possible. Consequently, for a given matrix, a larger proportion of the flow cross-section across the matrix should be allocated for the intake air flow which could pass through the matrix at a relatively low velocity and consequently incur a smaller pressure drop and maintain good volumetric efficiency for the engine. On the other hand, the exhaust gas velocity through the matrix should be relatively high compared with the speed of rotation of the matrix in order to permit effective dispensing of EGR. Thus taking into account the maximum volumetric flow rate and kinematic velocity associated with each flow stream in the rotary gas exchanger, for a given cross-section of the matrix shared by the engine intake and exhaust gas streams, the ratio of the flow cross-section areas of the ducts emerging at the internal end faces of the housing between the second set of entry and exit ducts for the intake air and the first set of entry and exit ducts for the exhaust gases should be at least 2:1, and preferably greater than 3:1.
In another application of a rotary gas and/or heat exchanger of the present invention used as a combined EGR dispenser and EGR cooler in a supercharged or turbocharged reciprocating internal combustion engine according to Cr32438274, the ducts in the housing comprise a first set of entry and exit ducts taking an engine exhaust gas stream from the engine through the housing and matrix towards the ambient atmosphere, a second set of entry and exit ducts positioned in rotational sequence after the first set of entry and exit ducts taking a boosted intake air stream from the supercharger or turbocharger through the housing and matrix towards the engine, at least one re-expansion duct positioned in rotational sequence after the second set of -10 -entry and exit ducts for discharging a re-expanded cool air stream out of the matrix, and a third set of entry and exit ducts positioned in rotational sequence after the re-expansion duct and connected to the re-expansion duct for directing the re-expanded cool air stream from the re-expansion duct back through the housing and matrix to the ambient atmosphere. Compared with the previous application, whilst a small proportion of the flow cross-section of the matrix is now allocated for the cooling air stream, the remaining larger proportion of the matrix shared between the engine intake air and exhaust gas streams should take into account the same design criterion that the ratio of the flow cross-section areas of the ducts emerging at the internal end faces of the housing between the second set of entry and exit ducts for the intake air and the first set of entry and exit ducts for the exhaust gases should be at least 2:1, and preferably greater than 3:1.
Brief description of the drawings
The invention will now be described further by way of example with reference to the accompanying drawings in which Figure 1 is a schematic view of an assembly of a rotary gas and heat exchanger of the present invention, used by way of example as a combined EGR dispenser and EGR cooler in a boosted internal combustion engine, Figure 2 is an end view of a matrix structure of thin-walled flow passages used in the assembly of Figure 1, Figure 3 is a plan view of one of two web-like meshes of resilient material used in the assembly of Figure 1, Figure 4 is a plan view of one of two perforated end plates used in the assembly of Figure 1, Figure 5 is an internal view of the bottom end face of the housing used in the assembly of Figure 1, -11 -showing the entry and exit ducts emerging at the end face, Figure 6 is a cross-section view of the assembly of the rotor, also showing an additional feature of a s ring sleeve extending from the inside faces of the end plates, Figure 7 s an end view of the separate bunches of flow passage sub-divided by the web-like mesh across the end face of the matrix after assembly of the rotor, and Figure 8 is a developed view of the assembly of Figure 1, showing the rotation of the rotor between the top and bottom end faces of the housing.
Detailed description of the preferred embodiment
The assembly of the present invention will be described by way of example for a combined rotary EGR dispenser and EGR cooler in a boosted reciprocating internal combustion engine. The invention can of course be used in a variety of other applications such as gas turbines, Stirling engines and industrial plants.
Figure 1 shows a boosted internal combustion engine 100 with an intake manifold 114 admitting pressurised intake air from a supercharger 124 (and/or from an exhaust gas driven turbocharger) via a rotary gas and heat exchanger 16 to the engine cylinders along an intake path comprising elements 124, 24, 14, 10, 24', 114 in the flow direction indicated by arrows, and an exhaust manifold 112 discharging exhaust gases from the engine cylinders via one or both of two exhaust ducts 32, 22. A proportioning valve 36 is also shown for regulating the relative flow of exhaust gases between the ducts 32, 22 where the latter duct 22 is connected via the rotary gas and heat exchanger 16 to the ambient atmosphere along a path comprising elements 112, 22, 14, 10, 22' in the flow direction also indicated by arrows.
-12 -Rotation of the matrix 10 facilitates the dispensing of EGR from the duct 22 to the duct 24' rnetere'd by the valve 36.
It also facilitates the cooling of the EGR by making use of an available stream of boosted air extracted internally from one part (duct 28) of the rotary gas exchanger and re-routed back through the matrix 10 via the ducts 26, 26'. Further details of the operation of the rotary EGR dispenser and EGR cooler may he found in GB2428465 and G82438274.
The matrix 10 in Figure 1 is part of a rotor assembly comprising components 6, 4, 10, 4, 6 (shown in Figures 2, 3 and 4) mounted along a shaft 12 and supported for rotation within the housing 14 with a very small and precise clearance 2 between each end face of the rotor butting against each end wall of the housing. The end clearance 2 (which is largely exaggerated in the drawing) provides effective gas seal between the rotor and the housing while the rotor is free to rotate without touching the end walls of the housing.
In Figure 1, the rotary gas and heat exchanger 16 comprises a housing 14 with entry and exits ducts 22, 22', 24, 24', 28, 26, 26' and a rotor assembly supported for rotation within the housing 14. The rotor assembly further comprises a central shaft 12, two perforated end plates 6 mounted rigidly to the shaft 12 at a precise distance apart between the outward facing end surfaces of the plates 6 for the rotor to fit within the housing with a precise clearance from the inward facing end surfaces of the housing, and a matrix structure 10 of thin-walled flow passages from one end of the matrix to the other end mounted axially for rotation and resiliently between the two rigidly mounted end plates 6 with the central shaft 12 passing through it.
In Figure 1, the mounting of the matrix 10 is achieved during assembly by bringing the end plates 6 and the matrix towards each other and sandwiching a web-like mesh 4 of -13 -resilient material between each inward facing surface of the plate 6 and outward facing surface of the matrix 10 for the mesh 4 to come to firm contact with the matrix 10 and seal off a pattern of continuous rows of flow passages at the end surface of the matrix 10 thereby sub-dividing the through-flow cross-section of the matrix into a plurality of separate bunches of flow passages 11 (also shown in Figures 6, 7 and 8 surrounded by the redundant flow passages covered by the links of the web-like mesh 4), each bunch connected through the perforated end plates 6 to the entry and exit ducts of the housing 14 as the rotor rotates.
Preferably, the web-like mesh 4 is secured by compression of the mesh 4 between the end plates 6.
Alternatively, an adhesive may be used to secure the mesh 4 between the end plate 6 and the matrix 10. As a further alternative, the web-like mesh 4 may be produced in situ by injecting a liquid adhesive on one of the component parts before assembly which sets to form a resilient seal after assembly.
The assembled rotor 6, 4, 10, 4, 6 will be mounted for rotation within the housing 14 with a precise clearance 2 between the end plates 6 of the rotor and the end walls of the housing 14 formed by the boundary walls of the entry and exit ducts emerging at the internal end faces of the housing, the ends of these walls co-operating with the ends of the rotor to produce the precise clearance as the rotor rotates.
In Figure 4, the perforations in the end plate 6 are slots openings 8 spaced between the links 4a of the web-like mesh 4 in Figure 3. This makes the end plate 6 resembling a wheel with spokes connected to a central shaft 12. The sides of the spokes support the web-like mesh 4 and provide the gripping torque for holding the matrix 10 and rotating it at the same speed as the plate 6, while the spaces -14 -between the spokes (i.e. the slot openings 8) allow gas flow through the sub-divided bunches of flow passages 11 in the matrix to connect with the entry and exit ducts in the housing 14. The outward facing surfaces of the spokes define a very small and precise clearance 2 with the end walls of the housing, thus forming an effective gas seal to stop to all intents and purposes any gas leakage at the perimeters of the entry and exit ducts and to maintain different gas pressures within the different sets of ducts.
In order to avoid short-circuiting of gases between the adjacent ducts in the housing 14 at the connection with each passing slot in the plate as the rotor rotates, it is important that the opening of each slot 8 does not exceed the boundary of the partitioning wall separating the ducts and passed by the slot as the rotor rotates. In Figures 4 and 5 and in Figure 8, this is achieved by either selecting the thickness of the partitioning wall emerging at the internal end face of the housing 14 to be greater than the width of the slot opening 8 at the end face of the plate 6, or tapering each slot opening 8 in the end plate 6 in the direction through the plate from a wider opening at the side of the web-like mesh to a narrower opening at the side of the end clearance surface of the plate 6, not exceeding the thickness of the partitioning wall emerging at the internal end face of the housing 14 passed by the slot 8 as the rotor rotates.
In the invention, where the slot openings 8 in the end plates 6 match the cross-sections of the sub-divided bunches of flow passages 11 in the matrix 10, there is no blocking of the passages because of the presence of the end plates 6.
On the other hand, where the slot openings 8 are tapered, there is some partial blocking of the flow passages but this could be minimised by smooth transition of the divergent opening of the slots 8 towards the sub-divided bunches 11.
In general, the presence of the end plates 6 will not cause -15 -any additional restriction in the overall volumetric efficiency of the gas exchanger provided that the combined effective flow cross-section of all the slots 8 passing within an entry or exit duct in the housing 14, for example duct 24 in Figures 5 and 8, is the same as or greater than the respective supply or discharge flow cross-section of those ducts connecting with the exchanger, for example ducts (24) and 24' in Figure 8.
The rotary gas and heat exchanger 16 in Figure 1 will function as a rotary gas dispenser having a plurality of dispensing volumes defined by the volume of each sub-divided bunch of flow passages 11 (also shown in Figures 6, 7 and 8), and as a rotary heat regenerator having a plurality of recuperative heat transfer elements defined by the surface area of each sub-divided bunch of flow passages 11.
Unique to the bunch concept of the present invention, the location of the slot openings 8 in the end plates 6 relative to the associated sub-divided bunches of flow passages 11 is not important because as soon as a slot opening 8 is exposed to gas flow, the gases will spread across the intervening space to fill all the flow passages within the bunch 11. In Figure 8, which shows a developed view of the rotor assembly (labelled R) traversing as it rotates in the direction of the arrow (the same rotational arrow is also shown in Figure 7) between the top and bottom end faces of the housing 14, each slot opening 8 and the associated bunch of flow passages 11 will undergo the same filling processes as the slot 8 passes the various entry and exit ducts in the housing 14. The time of exposure of each slot 8 across a given set of entry and exit ducts determines the length of travel of the gases at a given mean velocity along all the flow passages in the bunch 11. Where there are many slots passing within a given set of entry and exit ducts, the volume flow through the ducts is shared by all these slot openings and the mean gas velocity through the -16 -slots is therefore reduced, which also reduces the length of travel of the gases along the bunches of flow passages 11 in a given exposure time determined by the rotating speed of the rotor.
The matrix 10 can have crude external dimensions and any misalignment in the assembly will be fully taken up by resilience of the mesh 4 material (for example silicone rubber), while its function as a support structure for the flow guiding passages remains effective. Precise control of the end clearance 2 between the rotor 6, 4, 10, 4, 6 and the housing 14 rests entirely on the precision machined components in the rotor and housing similar to a rotary air blower (for example the Roots blower) using established technology for manufacture and with proven reliability. The torque required for driving the rotor will be very low since no work is done on the working fluids and there is no touching contact between the rotor and the housing except at the bearings.
In Figure 6, to assist assembly, the matrix 10 is cylindrical in shape and hollow through its central axis.
Each end plate 6 has additionally a ring sleeve 6a extending from the inside face of the plate 6 and concentric with the central shaft 12 to engage axially with the matrix 10 and guide the matrix 10 during assembly towards the end plate 6 until it meets firmly with the web-like mesh 4 which is sandwiched between. A resilient 0-ring 9 between the sleeve 6a and the matrix 10 is provided to cushion the assembly and position the matrix 10 concentrically with the end plates 6.
Thus the matrix is fully supported axially and laterally by resilient material when assembled to the rotor and there is no area of the matrix that is highly stressed.
By the same token, any differential thermal expansion and mechanical movement between the matrix 10 and the end plates 6 of the rotor assembly when the exchanger is in use -17 -will be safely absorbed by the resilient material of the web-like mesh 4 with little or no effect on the precise clearance 2 between the end plates 6 and the housing 14.
Thus the rotary gas and heat exchanger 16 could be operated with a wide range of gas temperatures and still maintain a stable and precise clearance 2 at the end faces of the rotor 6, 4, 10, 4, 6 which is essential for effective sealing of the gases connected to the exchanger.
In Figure 1, because the maximum power of the engine is directly related to the intake air pressure that is available in the intake system, it is important that the intake air flow through the matrix 10 should encounter as low a pressure drop as possible. Consequently, for a given matrix, a larger proportion of the flow cross-section across, the matrix 10 should be allocated for the intake air flow which could pass through the matrix at a relatively low velocity and consequently incur a smaller pressure drop and maintain good volumetric efficiency for the engine. On the other hand, the exhaust gas velocity through the matrix 10 should be relatively high compared with the speed of rotation of the matrix in order to permit effective dispensing of EGR. Thus taking into account the maximum volumetric flow rate and kinematic velocity associated with each flow stream in the rotary gas exchanger, for a given cross-section of the matrix shared by the engine intake and exhaust gas streams, the ratio of the flow cross-section areas of the ducts emerging at the internal end faces of the housing between the entry and exit ducts 24, 24' for the intake air and the entry and exit ducts 22, 22' for the exhaust gases should be at least 2:1, and preferably greater than 3:1, as shown in Figures 5 and 8; ASSEMBLY OF A ROTARY GAS AND/OR HEAT EXCHANGER
Field of the invention
The present invention relates to an assembly of a rotary gas exchanger, a rotary heat exchanger, or a combined rotary gas and heat exchanger.
Background of the invention
GB852204 and GB1136122 provide teaching in the gas sealing system of a rotary heat exchanger or regenerator.
The heat exchanger comprises a housing having inlet and outlet apertures for the heat exchange gases and a flow guiding matrix which is rotatable in the housing and through which the gases can flow. A sealing means is necessary to prevent leakage of the gases between the end faces of the rotating matrix and the adjacent end walls of the housing.
In GB852204, the sealing gap is supported by a bearing race and maintained substantially constant while the bearing assembly could move as an integral unit with any thermal expansion or mechanical vibration between the rotating matrix and the housing.
In GB1l36l22, the sealing means is a controlled gap of less than half the hydraulic diameter of the flow guiding channels of the matrix. Because of differential thermal expansion, this gap could vary, increasing leakage if the gap increases, and risking contact causing damage of the fragile matrix if the gap closes. To minimise the change in the width of the gap, both the housing and the matrix are made of ceramic material of similar thermal expansion.
Recent examples of applications of a rotary heat exchanger used as an EGR cooler for cooling recirculated exhaust gases fed through the gas exchanger into the intake system of a reciprocating internal combustion engine may be found in EP1586842 and US6161528 where special attention has been paid in the design of the rotating matrix and the clearance of the sealing gap between the end faces of the matrix with the adjacent end walls of the housing in order to withstand the exhaust gas pressure and air blower pressure connected to the gas exchanger. In US6161528, the sealing means is a spring-loaded contact sliding member of solid lubricating material which does not damage the fragile matrix but the contact pressure could cause friction and wear and increase the power requirement for driving the rotating matrix.
GB2428465 describes a rotary gas exchanger used as an EGR dispenser in a reciprocating internal combustion engine for metering some exhaust gases from the exhaust system of the engine and transferring the gases to the intake system of the engine by lateral displacement of sealed gas columns within the rotary gas exchanger. In this case, the effectiveness of the end seals in the rotating matrix becomes even more important which is specifically mentioned, quote: "A very small minimum clearance is maintained between the end faces of the rotating matrix butting with the end walls of the housing in order to stop to all intents and purposes any gas leakage at the perimeters of the entry and exit ducts and to maintain different gas pressures within each set of ducts". However, no detail is given in how the very small minimum clearance could be achieved during assembly and how this clearance could be maintained in use under high thermal load conditions.
GB2438274 describes a similar EGR dispenser with the addition of an integrated EGR cooler. The requirement for effective gas seals between the rotating matrix and the end walls of the housing will be the same as in GB2428465.
It is mentioned in GB2428465 that the walls of the flow guiding passages in the matrix may be constructed of thin foils of stainless steel or extruded ceramic in a honeycomb structure akin to that of the substrate of a catalytic converter commonly used in the automotive exhaust system.
Such a substrate would have been ideal for use in the rotary gas exchanger because of the relatively low cost due to high volume production for automotive applications. However the dimensional tolerance is poor though adequate for its original application but falls far short of the micron level accuracy needed for use in the rotary gas exchanger. It is impractical to apply additional machining to the substrate to produce better dimensional accuracy because of the very fragile nature of the material. There are also difficulties in mounting the substrate for rotation and maintaining micron level accuracy in the assembly and alignment of the matrix within the housing in order to achieve the required minimum clearance for effective sealing of the gases.
Apart from the difficulties in achieving the precise clearance during assembly of the rotating matrix, there are further difficulties in maintaining a stable clearance after assembly when the exchanger is in use under high thermal loads and mechanical vibration conditions. Differential thermal expansion and mechanical movements between the matrix and the housing could cause the clearance to change substantially, but there is as yet rio reliable proposal in the prior art that could offer a satisfactory solution.
Aim of the invention The present invention aims to mitigate all the above problems during assembly and in use, and proposes to include a matrix of low dimensional accuracy in the assembly of a rotary gas and/or heat exchanger.
Summary of the invention
According to the present invention, there is provided an assembly of a rotary gas and/or heat exchanger comprising a housing with entry and exits ducts and a rotor supported for rotation within the housing, the rotor further comprising a central shaft, two perforated end plates mounted rigidly to the shaft at a precise distance apart between the outward facing end surfaces of the plates for the rotor to fit within the housing with a precise clearance from the end walls of the housing, and a matrix structure of thin-walled flow passages from one end of the matrix to the other end mounted axially for rotation and resiliently between the two rigidly mounted end plates with the central shaft passing through it, characterised in that the mounting of the matrix is achieved during assembly by bringing the end plates and the matrix towards each other and sandwiching a web-like mesh of resilient material between each inward facing surface of the plate and outward facing surface of the matrix for the mesh to come to firm contact with the matrix and seal off a pattern of continuous rows of flow passages at the end surface of the matrix thereby sub-dividing the through-flow cross-section of the matrix into a plurality of separate bunches of flow passages, each bunch connected through the perforated end plates to the entry and exit ducts of the housing as the rotor rotates.
Preferably, the web-like mesh is secured by compression of the mesh between the end plates. Alternatively, an adhesive may be used to secure the mesh between the end plate and the matrix. As a further alternative, the web-like mesh may be produced in situ by injecting a liquid adhesive on one of the component parts before assembly which sets to form a resilient seal after assembly.
The assembled rotor will be mounted for rotation within the housing with a precise clearance between the end plates of the rotor and the end walls of the housing formed by the boundary walls of the entry and exit ducts emerging at the internal end faces of the housing, the ends of these walls co-operating with the ends of the rotor to produce the precise clearance as the rotor rotates.
Preferably, the perforations in the end plates are slots openings spaced between the links of the web-like mesh of resilient material. This makes the end plate resembling a wheel with spokes connected to a central shaft. The sides of the spokes support the web- like mesh and provide the gripping torque for holding the matrix and rotating it at the same speed as the plate, while the spaces between the spokes (i.e. the slot openings) allow gas flow through the sub-divided bunches of flow passages in the matrix to connect with the entry and exit ducts in the housing. The outward facing surfaces of the spokes define a very small and precise clearance with the end walls of the housing, thus forming an effective gas seal to stop to all intents and purposes any gas leakage at the perimeters of the entry and exit ducts and to maintain different gas pressures within the different sets of ducts, as stipulated in GB2428465.
In order to avoid short-circuiting of gases between the adjacent ducts in the housing at the connection with each passing slot in the plate as the rotor rotates, it is important that the opening of each slot does not exceed the boundary of the partitioning wall separating the ducts and passed by the slot as the rotor rotates. This may be achieved by either selecting the thickness of the partitioning wall emerging at the internal end face of the housing to be greater than the width of the slot opening at the end face of the plate, or tapering each slot opening in the end plate in the direction through the plate from a wider opening at the side of the web-like mesh to a narrower opening at the side of the end clearance surface of the plate, not exceeding the thickness of the partitioning wall emerging at the internal end face of the housing passed by the slot as the rotor rotates.
In the invention, where the slot openings in the end plates match the cross-sections of the sub-divided bunches of flow passages in the matrix, there is no blocking of the passages because of the presence of the end plates. On the other hand, where the slot openings are tapered, there is some partial blocking of the flow passages but this could be minimised by smooth transition of the divergent opening of the slots towards the sub-divided bunches. In general, the presence of the end plates will not cause any additional restriction in the overall volumetric efficiency of the gas exchanger provided that the combined effective flow cross-section of all the slots passing within an entry or exit duct in the housing is the same as or greater than the respective supply or discharge flow cross-section of those ducts connecting with the exchanger.
The above assembly of the rotary gas and/or heat exchanger will function as a rotary gas dispenser having a plurality of dispensing volumes defined by the volume of each sub-divided bunch of flow passages, and as a rotary heat regenerator having a plurality of recuperative heat transfer elements defined by the surface area of each sub-divided bunch of flow passages.
Unique to the bunch concept of the present invention, the location of the slot openings in the end plates relative to the associated sub-divided bunches of flow passages is not important because as soon as a slot opening is exposed to gas flow, the gases will spread across the intervening space to fill all the flow passages within the bunch. Each slot opening and the associated bunch of flow passages will undergo the same filling processes as the slot passes the various entry and exit ducts in the housing. The time of exposure of each slot across a given set of entry and exit ducts determines the length of travel of the gases at a given mean velocity along all the flow passages in the bunch. Where there are many slots passing within a given set of entry and exit ducts, the volume flow through the ducts is shared by all these slot openings and the mean gas velocity through the slots is therefore reduced, which also reduces the length of travel of the gases along the bunches of flow passages in a given exposure time determined by the rotating speed of the rotor.
The matrix can have crude external dimensions and any misalignment in the assembly will be fully taken up by resilience of the mesh material (for example silicone rubber), while its function as a support structure for the flow guiding passages remains effective. Precise control of the end clearance between the rotor and the housing rests entirely on the precision machined components in the rotor and housing similar to a rotary air blower (for example the Roots blower) using established technology for manufacture and with proven reliability. The torque required for driving the rotor will be very low since no work is done on the working fluids and there is no touching contact between the rotor and the housing except at the bearings.
To assist assembly, the matrix is cylindrical in shape and hollow through its central axis. Each end plate has a ring sleeve extending from the inside face of the plate concentric with the central shaft to engage axially with the matrix and guide the matrix during assembly towards the end plate until it meets firmly with the web-like mesh which is sandwiched between. A resilient 0-ring between the sleeve and the matrix may be provided to cushion the assembly and position the matrix concentrically with the end plates.
Thus the matrix is fully supported axially and laterally by resilient material when assembled to the rotor and there is no area of the matrix that is highly stressed.
By the same token, any differential thermal expansion and mechanical movement between the matrix and the end plates of the rotor when the exchanger is in use will be safely absorbed by the resilient material of the web-like S mesh with little or no effect on the precise clearance between the end plates and the housing. Thus the rotary gas and/or heat exchanger of the present invention could be operated with a wide range of gas temperatures and still maintain a stable and precise clearance at the end faces of the rotor which is essential for effective sealing of the gases connected to the exchanger.
In a typical application of a rotary heat exchanger of the present invention for example in a gas turbine or Stirling engine, the housing has a first set of entry and exit ducts for the hot gases and a second set of entry and exit ducts for the cold gases, and the ratio of the flow cross-section areas of the ducts emerging at the internal end faces of the housing between the hot and cold sets of ducts is typically 1:1.
In a particular application of a rotary gas exchanger of the present invention used as an EGR dispenser in a reciprocating internal combustion engine according to GB2428465, the ducts in the housing comprise a first set of entry and exit ducts taking an engine exhaust gas stream from the engine through the housing and matrix towards the ambient atmosphere and a second set of entry and exit ducts taking an engine intake air stream from the ambient atmosphere through the housing and matrix towards the engine. The respective sets of ducts are disposed in the housing with the entry and exit ducts of each set opposite one another facing the ends of the rotating matrix and each set is positioned eccentrically to the axis of rotation of the matrix apart from and in rotational sequence with the other set.
In the above application, because the maximum power of the engine is directly related to the intake air pressure that is available in the intake system, it is important that the intake air flow through the matrix should encounter as low a pressure drop as possible. Consequently, for a given matrix, a larger proportion of the flow cross-section across the matrix should be allocated for the intake air flow which could pass through the matrix at a relatively low velocity and consequently incur a smaller pressure drop and maintain good volumetric efficiency for the engine. On the other hand, the exhaust gas velocity through the matrix should be relatively high compared with the speed of rotation of the matrix in order to permit effective dispensing of EGR. Thus taking into account the maximum volumetric flow rate and kinematic velocity associated with each flow stream in the rotary gas exchanger, for a given cross-section of the matrix shared by the engine intake and exhaust gas streams, the ratio of the flow cross-section areas of the ducts emerging at the internal end faces of the housing between the second set of entry and exit ducts for the intake air and the first set of entry and exit ducts for the exhaust gases should be at least 2:1, and preferably greater than 3:1.
In another application of a rotary gas and/or heat exchanger of the present invention used as a combined EGR dispenser and EGR cooler in a supercharged or turbocharged reciprocating internal combustion engine according to Cr32438274, the ducts in the housing comprise a first set of entry and exit ducts taking an engine exhaust gas stream from the engine through the housing and matrix towards the ambient atmosphere, a second set of entry and exit ducts positioned in rotational sequence after the first set of entry and exit ducts taking a boosted intake air stream from the supercharger or turbocharger through the housing and matrix towards the engine, at least one re-expansion duct positioned in rotational sequence after the second set of -10 -entry and exit ducts for discharging a re-expanded cool air stream out of the matrix, and a third set of entry and exit ducts positioned in rotational sequence after the re-expansion duct and connected to the re-expansion duct for directing the re-expanded cool air stream from the re-expansion duct back through the housing and matrix to the ambient atmosphere. Compared with the previous application, whilst a small proportion of the flow cross-section of the matrix is now allocated for the cooling air stream, the remaining larger proportion of the matrix shared between the engine intake air and exhaust gas streams should take into account the same design criterion that the ratio of the flow cross-section areas of the ducts emerging at the internal end faces of the housing between the second set of entry and exit ducts for the intake air and the first set of entry and exit ducts for the exhaust gases should be at least 2:1, and preferably greater than 3:1.
Brief description of the drawings
The invention will now be described further by way of example with reference to the accompanying drawings in which Figure 1 is a schematic view of an assembly of a rotary gas and heat exchanger of the present invention, used by way of example as a combined EGR dispenser and EGR cooler in a boosted internal combustion engine, Figure 2 is an end view of a matrix structure of thin-walled flow passages used in the assembly of Figure 1, Figure 3 is a plan view of one of two web-like meshes of resilient material used in the assembly of Figure 1, Figure 4 is a plan view of one of two perforated end plates used in the assembly of Figure 1, Figure 5 is an internal view of the bottom end face of the housing used in the assembly of Figure 1, -11 -showing the entry and exit ducts emerging at the end face, Figure 6 is a cross-section view of the assembly of the rotor, also showing an additional feature of a s ring sleeve extending from the inside faces of the end plates, Figure 7 s an end view of the separate bunches of flow passage sub-divided by the web-like mesh across the end face of the matrix after assembly of the rotor, and Figure 8 is a developed view of the assembly of Figure 1, showing the rotation of the rotor between the top and bottom end faces of the housing.
Detailed description of the preferred embodiment
The assembly of the present invention will be described by way of example for a combined rotary EGR dispenser and EGR cooler in a boosted reciprocating internal combustion engine. The invention can of course be used in a variety of other applications such as gas turbines, Stirling engines and industrial plants.
Figure 1 shows a boosted internal combustion engine 100 with an intake manifold 114 admitting pressurised intake air from a supercharger 124 (and/or from an exhaust gas driven turbocharger) via a rotary gas and heat exchanger 16 to the engine cylinders along an intake path comprising elements 124, 24, 14, 10, 24', 114 in the flow direction indicated by arrows, and an exhaust manifold 112 discharging exhaust gases from the engine cylinders via one or both of two exhaust ducts 32, 22. A proportioning valve 36 is also shown for regulating the relative flow of exhaust gases between the ducts 32, 22 where the latter duct 22 is connected via the rotary gas and heat exchanger 16 to the ambient atmosphere along a path comprising elements 112, 22, 14, 10, 22' in the flow direction also indicated by arrows.
-12 -Rotation of the matrix 10 facilitates the dispensing of EGR from the duct 22 to the duct 24' rnetere'd by the valve 36.
It also facilitates the cooling of the EGR by making use of an available stream of boosted air extracted internally from one part (duct 28) of the rotary gas exchanger and re-routed back through the matrix 10 via the ducts 26, 26'. Further details of the operation of the rotary EGR dispenser and EGR cooler may he found in GB2428465 and G82438274.
The matrix 10 in Figure 1 is part of a rotor assembly comprising components 6, 4, 10, 4, 6 (shown in Figures 2, 3 and 4) mounted along a shaft 12 and supported for rotation within the housing 14 with a very small and precise clearance 2 between each end face of the rotor butting against each end wall of the housing. The end clearance 2 (which is largely exaggerated in the drawing) provides effective gas seal between the rotor and the housing while the rotor is free to rotate without touching the end walls of the housing.
In Figure 1, the rotary gas and heat exchanger 16 comprises a housing 14 with entry and exits ducts 22, 22', 24, 24', 28, 26, 26' and a rotor assembly supported for rotation within the housing 14. The rotor assembly further comprises a central shaft 12, two perforated end plates 6 mounted rigidly to the shaft 12 at a precise distance apart between the outward facing end surfaces of the plates 6 for the rotor to fit within the housing with a precise clearance from the inward facing end surfaces of the housing, and a matrix structure 10 of thin-walled flow passages from one end of the matrix to the other end mounted axially for rotation and resiliently between the two rigidly mounted end plates 6 with the central shaft 12 passing through it.
In Figure 1, the mounting of the matrix 10 is achieved during assembly by bringing the end plates 6 and the matrix towards each other and sandwiching a web-like mesh 4 of -13 -resilient material between each inward facing surface of the plate 6 and outward facing surface of the matrix 10 for the mesh 4 to come to firm contact with the matrix 10 and seal off a pattern of continuous rows of flow passages at the end surface of the matrix 10 thereby sub-dividing the through-flow cross-section of the matrix into a plurality of separate bunches of flow passages 11 (also shown in Figures 6, 7 and 8 surrounded by the redundant flow passages covered by the links of the web-like mesh 4), each bunch connected through the perforated end plates 6 to the entry and exit ducts of the housing 14 as the rotor rotates.
Preferably, the web-like mesh 4 is secured by compression of the mesh 4 between the end plates 6.
Alternatively, an adhesive may be used to secure the mesh 4 between the end plate 6 and the matrix 10. As a further alternative, the web-like mesh 4 may be produced in situ by injecting a liquid adhesive on one of the component parts before assembly which sets to form a resilient seal after assembly.
The assembled rotor 6, 4, 10, 4, 6 will be mounted for rotation within the housing 14 with a precise clearance 2 between the end plates 6 of the rotor and the end walls of the housing 14 formed by the boundary walls of the entry and exit ducts emerging at the internal end faces of the housing, the ends of these walls co-operating with the ends of the rotor to produce the precise clearance as the rotor rotates.
In Figure 4, the perforations in the end plate 6 are slots openings 8 spaced between the links 4a of the web-like mesh 4 in Figure 3. This makes the end plate 6 resembling a wheel with spokes connected to a central shaft 12. The sides of the spokes support the web-like mesh 4 and provide the gripping torque for holding the matrix 10 and rotating it at the same speed as the plate 6, while the spaces -14 -between the spokes (i.e. the slot openings 8) allow gas flow through the sub-divided bunches of flow passages 11 in the matrix to connect with the entry and exit ducts in the housing 14. The outward facing surfaces of the spokes define a very small and precise clearance 2 with the end walls of the housing, thus forming an effective gas seal to stop to all intents and purposes any gas leakage at the perimeters of the entry and exit ducts and to maintain different gas pressures within the different sets of ducts.
In order to avoid short-circuiting of gases between the adjacent ducts in the housing 14 at the connection with each passing slot in the plate as the rotor rotates, it is important that the opening of each slot 8 does not exceed the boundary of the partitioning wall separating the ducts and passed by the slot as the rotor rotates. In Figures 4 and 5 and in Figure 8, this is achieved by either selecting the thickness of the partitioning wall emerging at the internal end face of the housing 14 to be greater than the width of the slot opening 8 at the end face of the plate 6, or tapering each slot opening 8 in the end plate 6 in the direction through the plate from a wider opening at the side of the web-like mesh to a narrower opening at the side of the end clearance surface of the plate 6, not exceeding the thickness of the partitioning wall emerging at the internal end face of the housing 14 passed by the slot 8 as the rotor rotates.
In the invention, where the slot openings 8 in the end plates 6 match the cross-sections of the sub-divided bunches of flow passages 11 in the matrix 10, there is no blocking of the passages because of the presence of the end plates 6.
On the other hand, where the slot openings 8 are tapered, there is some partial blocking of the flow passages but this could be minimised by smooth transition of the divergent opening of the slots 8 towards the sub-divided bunches 11.
In general, the presence of the end plates 6 will not cause -15 -any additional restriction in the overall volumetric efficiency of the gas exchanger provided that the combined effective flow cross-section of all the slots 8 passing within an entry or exit duct in the housing 14, for example duct 24 in Figures 5 and 8, is the same as or greater than the respective supply or discharge flow cross-section of those ducts connecting with the exchanger, for example ducts (24) and 24' in Figure 8.
The rotary gas and heat exchanger 16 in Figure 1 will function as a rotary gas dispenser having a plurality of dispensing volumes defined by the volume of each sub-divided bunch of flow passages 11 (also shown in Figures 6, 7 and 8), and as a rotary heat regenerator having a plurality of recuperative heat transfer elements defined by the surface area of each sub-divided bunch of flow passages 11.
Unique to the bunch concept of the present invention, the location of the slot openings 8 in the end plates 6 relative to the associated sub-divided bunches of flow passages 11 is not important because as soon as a slot opening 8 is exposed to gas flow, the gases will spread across the intervening space to fill all the flow passages within the bunch 11. In Figure 8, which shows a developed view of the rotor assembly (labelled R) traversing as it rotates in the direction of the arrow (the same rotational arrow is also shown in Figure 7) between the top and bottom end faces of the housing 14, each slot opening 8 and the associated bunch of flow passages 11 will undergo the same filling processes as the slot 8 passes the various entry and exit ducts in the housing 14. The time of exposure of each slot 8 across a given set of entry and exit ducts determines the length of travel of the gases at a given mean velocity along all the flow passages in the bunch 11. Where there are many slots passing within a given set of entry and exit ducts, the volume flow through the ducts is shared by all these slot openings and the mean gas velocity through the -16 -slots is therefore reduced, which also reduces the length of travel of the gases along the bunches of flow passages 11 in a given exposure time determined by the rotating speed of the rotor.
The matrix 10 can have crude external dimensions and any misalignment in the assembly will be fully taken up by resilience of the mesh 4 material (for example silicone rubber), while its function as a support structure for the flow guiding passages remains effective. Precise control of the end clearance 2 between the rotor 6, 4, 10, 4, 6 and the housing 14 rests entirely on the precision machined components in the rotor and housing similar to a rotary air blower (for example the Roots blower) using established technology for manufacture and with proven reliability. The torque required for driving the rotor will be very low since no work is done on the working fluids and there is no touching contact between the rotor and the housing except at the bearings.
In Figure 6, to assist assembly, the matrix 10 is cylindrical in shape and hollow through its central axis.
Each end plate 6 has additionally a ring sleeve 6a extending from the inside face of the plate 6 and concentric with the central shaft 12 to engage axially with the matrix 10 and guide the matrix 10 during assembly towards the end plate 6 until it meets firmly with the web-like mesh 4 which is sandwiched between. A resilient 0-ring 9 between the sleeve 6a and the matrix 10 is provided to cushion the assembly and position the matrix 10 concentrically with the end plates 6.
Thus the matrix is fully supported axially and laterally by resilient material when assembled to the rotor and there is no area of the matrix that is highly stressed.
By the same token, any differential thermal expansion and mechanical movement between the matrix 10 and the end plates 6 of the rotor assembly when the exchanger is in use -17 -will be safely absorbed by the resilient material of the web-like mesh 4 with little or no effect on the precise clearance 2 between the end plates 6 and the housing 14.
Thus the rotary gas and heat exchanger 16 could be operated with a wide range of gas temperatures and still maintain a stable and precise clearance 2 at the end faces of the rotor 6, 4, 10, 4, 6 which is essential for effective sealing of the gases connected to the exchanger.
In Figure 1, because the maximum power of the engine is directly related to the intake air pressure that is available in the intake system, it is important that the intake air flow through the matrix 10 should encounter as low a pressure drop as possible. Consequently, for a given matrix, a larger proportion of the flow cross-section across, the matrix 10 should be allocated for the intake air flow which could pass through the matrix at a relatively low velocity and consequently incur a smaller pressure drop and maintain good volumetric efficiency for the engine. On the other hand, the exhaust gas velocity through the matrix 10 should be relatively high compared with the speed of rotation of the matrix in order to permit effective dispensing of EGR. Thus taking into account the maximum volumetric flow rate and kinematic velocity associated with each flow stream in the rotary gas exchanger, for a given cross-section of the matrix shared by the engine intake and exhaust gas streams, the ratio of the flow cross-section areas of the ducts emerging at the internal end faces of the housing between the entry and exit ducts 24, 24' for the intake air and the entry and exit ducts 22, 22' for the exhaust gases should be at least 2:1, and preferably greater than 3:1, as shown in Figures 5 and 8;

Claims (16)

  1. -18 -C1AIMS 1. An assembly of a rotary gas and/or heat exchanger comprising a housing with entry and exits ducts and a rotor supported for rotation within the housing, the rotor further comprising a central shaft, two perforated end plates mounted rigidly to the shaft at a precise distance apart between the outward facing end surfaces of the plates for the rotor to fit within the housing with a precise clearance from the end walls of the housing, and a matrix structure of thin-walled flow passages from one end of the matrix to the other end mounted axially for rotation and resiliently between the two rigidly mounted end plates with the central shaft passing through it, characterised in that the mounting 1.5 of the matrix is achieved during assembly by bringing the end plates and the matrix towards each other and sandwiching a web-like mesh of resilient material between each inward facing surface of the plate and outward facing surface of the matrix for the mesh to come to firm contact with the matrix and seal off a pattern of continuous rows of flow passages at the end surface of the matrix thereby sub-dividing the through-flow cross-section of the matrix into a plurality of separate bunches of flow passages, each bunch connected through the perforated end plates to the entry and exit ducts of the housing as the rotor rotates.
  2. 2. An assembly of a rotary gas and/or heat exchanger as claimed in claim 1, wherein the web-like mesh is secured by compression of the mesh between the end plates.
  3. 3. An assembly of a rotary gas and/or heat exchanger as claimed in claim 1, wherein an adhesive is used to secure the mesh between the end plate and the matrix.
  4. 4. An assembly of a rotary gas and/or heat exchanger as claimed in claim 1, wherein the web-like mesh is produced in situ by injecting a liquid adhesive on one of the -19 -component parts before assembly which sets to form a resilient seal after assembly.
  5. 5. An assembly of a rotary gas and/or heat exchanger as claimed in claim 1, wherein the end walls of the housing are formed by the boundary walls of the entry and exit ducts emerging at the internal end faces of the housing, the ends of these walls co-operating with the ends of the rotor to produce the precise clearance as the rotor rotates.
  6. 6. An assembly of a rotary gas and/or heat exchanger as claimed in claim 1, wherein the perforations in the end plates are slot openings spaced between the links of the web-like mesh of resilient material.
  7. 7. An assembly of a rotary gas and/or heat exchanger as claimed in claim 6, wherein each slot opening at the side of the end clearance surface of the end plate does not exceed the boundary of the end clearance surface of the partitioning wall separating the ducts emerging at the internal end face of the housing and passed by the slot as the rotor rotates.
  8. 8. An assembly of a rotary gas and/or heat exchanger as claimed in claim 7, wherein each slot opening in the end plate is tapered in the direction through the plate from a wider opening at the side of the web-like mesh to a narrower opening at the side of the end clearance surface of the plate.
  9. 9. An assembly of a rotary gas and/or heat exchanger as claimed in claim 8, wherein the combined effective flow cross-section of all the slots passing within an entry or exit duct in the housing is the same as or greater than the respective supply or discharge flow cross-section of those ducts connecting with the exchanger.
    -20 -
  10. 10. An assembly of a rotary gas and/or heat exchanger as claimed in any preceding claim, wherein the matrix is cylindrical in shape and each end plate has a ring sleeve extending from the inside face of the plate concentric with the central shaft to engage axially with the matrix and guide the matrix during assembly towards the end plate until it meets firmly with the web-like mesh which is sandwiched between.
  11. 11. An assembly of a rotary gas and/or heat exchanger as claimed in 10, wherein a resilient 0-ring is provided between the sleeve and the matrix to cushion the assembly and position the matrix concentrically with the end plates until the matrix meets firmly with the web-like mesh.
  12. 12. A rotary gas dispenser comprising an assembly as claimed in any one of claims 1 to 11, having a plurality of dispensing volumes defined by the volume of each sub-divided bunch of flow passages.
  13. 13. A rotary heat regenerator comprising an assembly as claimed in any one of claims 1 to 11, having a plurality of recuperative heat transfer elements defined by the surface area of each sub-divided bunch of flow passages.
  14. 14. A rotary gas and/or heat exchanger comprising an assembly as claimed in any one of claims 1 to 11, connected to a reciprocating internal combustion engine, wherein the ducts in the housing comprise a first set of entry and exit ducts taking an engine exhaust gas stream from the engine through the housing and matrix towards the ambient atmosphere and a second set of entry and exit ducts taking an engine intake air stream from the ambient atmosphere through the housing and matrix towards the engine, and wherein the respective sets of ducts are disposed in the housing with the entry and exit ducts of each set opposite one another facing the ends of the rotating matrix and each -21 -set is positioned eccentrically to the axis of rotation of the matrix apart from and in rotational sequence with the other set.
  15. 15. A rotary gas and/or heat exchanger comprising an assembly as claimed in any one of claims 1 to 11, connected to a supercharged or turbocharged reciprocating internal combustion engine, wherein the ducts in the housing comprise a first set of entry and exit ducts taking an engine exhaust gas stream from the engine through the housing and matrix towards the ambient atmosphere, a second set of entry and exit ducts positioned in rotational sequence after the first set of entry and exit ducts taking a boosted intake air stream from the supercharger or turbocharger through the housing and matrix towards the engine, at least one re-expansion duct positioned in rotational sequence after the second set of entry and exit ducts for discharging a re-expanded cool air stream out of the matrix, and a third set of entry and exit ducts positioned in rotational sequence after the re-expansion duct and connected to the re-expansion duct for directing the re-expanded cool air stream from the re-expansion duct back through the housing and matrix to the ambient atmosphere.
  16. 16. A rotary gas and/or heat exchanger comprising an assembly as claimed in claim 14 or 15, wherein for a given cross-section of the matrix shared by the engine intake and exhaust gas streams, the ratio of the flow cross-section areas of the ducts emerging at the internal end faces of the housing between the second set of entry and exit ducts for the intake air and the first set of entry and exit ducts for the exhaust gases is at least 2:1.
    16. A rotary gas and/or heat exchanger comprising an assembly as claimed in claim 14 or 15, wherein for a given cross-section of the matrix shared by the engine intake and exhaust gas streams, the ratio of the flow cross-section areas of the ducts emerging at the internal end faces of the housing between the second set of entry and exit ducts for the intake air and the first set of entry and exit ducts for the exhaust gases is at least 2:1.
    -18 -C1AIMS 1. An assembly of a rotary gas and/or heat exchanger comprising a housing with entry and exits ducts and a rotor supported for rotation within the housing, the rotor further comprising a central shaft, two perforated end plates mounted rigidly to the shaft at a precise distance apart between the outward facing end surfaces of the plates for the rotor to fit within the housing with a precise clearance from the end walls of the housing, and a matrix structure of thin-walled flow passages from one end of the matrix to the other end mounted axially for rotation and resiliently between the two rigidly mounted end plates with the central shaft passing through it, characterised in that the mounting 1.5 of the matrix is achieved during assembly by bringing the end plates and the matrix towards each other and sandwiching a web-like mesh of resilient material between each inward facing surface of the plate and outward facing surface of the matrix for the mesh to come to firm contact with the matrix and seal off a pattern of continuous rows of flow passages at the end surface of the matrix thereby sub-dividing the through-flow cross-section of the matrix into a plurality of separate bunches of flow passages, each bunch connected through the perforated end plates to the entry and exit ducts of the housing as the rotor rotates.
    2. An assembly of a rotary gas and/or heat exchanger as claimed in claim 1, wherein the web-like mesh is secured by compression of the mesh between the end plates.
    3. An assembly of a rotary gas and/or heat exchanger as claimed in claim 1, wherein an adhesive is used to secure the mesh between the end plate and the matrix.
    4. An assembly of a rotary gas and/or heat exchanger as claimed in claim 1, wherein the web-like mesh is produced in situ by injecting a liquid adhesive on one of the -19 -component parts before assembly which sets to form a resilient seal after assembly.
    5. An assembly of a rotary gas and/or heat exchanger as claimed in claim 1, wherein the end walls of the housing are formed by the boundary walls of the entry and exit ducts emerging at the internal end faces of the housing, the ends of these walls co-operating with the ends of the rotor to produce the precise clearance as the rotor rotates.
    6. An assembly of a rotary gas and/or heat exchanger as claimed in claim 1, wherein the perforations in the end plates are slot openings spaced between the links of the web-like mesh of resilient material.
    7. An assembly of a rotary gas and/or heat exchanger as claimed in claim 6, wherein each slot opening at the side of the end clearance surface of the end plate does not exceed the boundary of the end clearance surface of the partitioning wall separating the ducts emerging at the internal end face of the housing and passed by the slot as the rotor rotates.
    8. An assembly of a rotary gas and/or heat exchanger as claimed in claim 7, wherein each slot opening in the end plate is tapered in the direction through the plate from a wider opening at the side of the web-like mesh to a narrower opening at the side of the end clearance surface of the plate.
    9. An assembly of a rotary gas and/or heat exchanger as claimed in claim 8, wherein the combined effective flow cross-section of all the slots passing within an entry or exit duct in the housing is the same as or greater than the respective supply or discharge flow cross-section of those ducts connecting with the exchanger.
    -20 - 10. An assembly of a rotary gas and/or heat exchanger as claimed in any preceding claim, wherein the matrix is cylindrical in shape and each end plate has a ring sleeve extending from the inside face of the plate concentric with the central shaft to engage axially with the matrix and guide the matrix during assembly towards the end plate until it meets firmly with the web-like mesh which is sandwiched between.
    11. An assembly of a rotary gas and/or heat exchanger as claimed in 10, wherein a resilient 0-ring is provided between the sleeve and the matrix to cushion the assembly and position the matrix concentrically with the end plates until the matrix meets firmly with the web-like mesh.
    12. A rotary gas dispenser comprising an assembly as claimed in any one of claims 1 to 11, having a plurality of dispensing volumes defined by the volume of each sub-divided bunch of flow passages.
    13. A rotary heat regenerator comprising an assembly as claimed in any one of claims 1 to 11, having a plurality of recuperative heat transfer elements defined by the surface area of each sub-divided bunch of flow passages.
    14. A rotary gas and/or heat exchanger comprising an assembly as claimed in any one of claims 1 to 11, connected to a reciprocating internal combustion engine, wherein the ducts in the housing comprise a first set of entry and exit ducts taking an engine exhaust gas stream from the engine through the housing and matrix towards the ambient atmosphere and a second set of entry and exit ducts taking an engine intake air stream from the ambient atmosphere through the housing and matrix towards the engine, and wherein the respective sets of ducts are disposed in the housing with the entry and exit ducts of each set opposite one another facing the ends of the rotating matrix and each -21 -set is positioned eccentrically to the axis of rotation of the matrix apart from and in rotational sequence with the other set.
    15. A rotary gas and/or heat exchanger comprising an assembly as claimed in any one of claims 1 to 11, connected to a supercharged or turbocharged reciprocating internal combustion engine, wherein the ducts in the housing comprise a first set of entry and exit ducts taking an engine exhaust gas stream from the engine through the housing and matrix towards the ambient atmosphere, a second set of entry and exit ducts positioned in rotational sequence after the first set of entry and exit ducts taking a boosted intake air stream from the supercharger or turbocharger through the housing and matrix towards the engine, at least one re-expansion duct positioned in rotational sequence after the second set of entry and exit ducts for discharging a re-expanded cool air stream out of the matrix, and a third set of entry and exit ducts positioned in rotational sequence after the re-expansion duct and connected to the re-expansion duct for directing the re-expanded cool air stream from the re-expansion duct back through the housing and matrix to the ambient atmosphere.
GB0724213A 2007-12-11 2007-12-11 Rotary gas heat exchanger Withdrawn GB2455532A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
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US20110167809A1 (en) * 2008-09-26 2011-07-14 Renault Trucks Energy recovering system for an internal combustion engine
CN103697733A (en) * 2013-12-10 2014-04-02 浙江天石纳米科技有限公司 Damp and hot waste gas recycling wheel-type heat exchanger and using method thereof
US20150159542A1 (en) * 2013-12-11 2015-06-11 Hyundai Motor Company Engine system having turbocharger
US20150167595A1 (en) * 2013-12-16 2015-06-18 Hyundai Motor Company Cooling system for diesel engine having turbocharger
CN108980955A (en) * 2018-05-23 2018-12-11 中国科学院上海应用物理研究所 Matrix management formula solid temperature subregion energy storage method and device

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GB790270A (en) * 1954-12-16 1958-02-05 Svenska Rotor Maskiner Ab Improvements in or relating to rotary regenerative heat exchangers
GB1455269A (en) * 1972-11-29 1976-11-10 Bbc Brown Boveri & Cie Supercharged internal combustion engine
WO2001081837A1 (en) * 2000-04-19 2001-11-01 Mg Innovations Corp. Air conditioning device

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Publication number Priority date Publication date Assignee Title
GB790270A (en) * 1954-12-16 1958-02-05 Svenska Rotor Maskiner Ab Improvements in or relating to rotary regenerative heat exchangers
GB1455269A (en) * 1972-11-29 1976-11-10 Bbc Brown Boveri & Cie Supercharged internal combustion engine
WO2001081837A1 (en) * 2000-04-19 2001-11-01 Mg Innovations Corp. Air conditioning device

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110167809A1 (en) * 2008-09-26 2011-07-14 Renault Trucks Energy recovering system for an internal combustion engine
CN103697733A (en) * 2013-12-10 2014-04-02 浙江天石纳米科技有限公司 Damp and hot waste gas recycling wheel-type heat exchanger and using method thereof
US20150159542A1 (en) * 2013-12-11 2015-06-11 Hyundai Motor Company Engine system having turbocharger
US9435250B2 (en) * 2013-12-11 2016-09-06 Hyundai Motor Company Engine system having turbocharger
US20150167595A1 (en) * 2013-12-16 2015-06-18 Hyundai Motor Company Cooling system for diesel engine having turbocharger
US9464599B2 (en) * 2013-12-16 2016-10-11 Hyundai Motor Company Cooling system for diesel engine having turbocharger
CN108980955A (en) * 2018-05-23 2018-12-11 中国科学院上海应用物理研究所 Matrix management formula solid temperature subregion energy storage method and device
CN108980955B (en) * 2018-05-23 2020-05-15 中国科学院上海应用物理研究所 Matrix management type solid temperature partition energy storage method and device

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