Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D9/00—Stators
  • F01D9/02—Nozzles; Nozzle boxes; Stator blades; Guide conduits, e.g. individual nozzles
  • F01D9/026—Scrolls for radial machines or engines
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B37/00—Engines characterised by provision of pumps driven at least for part of the time by exhaust
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2220/00—Application
  • F05D2220/40—Application in turbochargers

Definitions

• the present invention relates to a turbine housing and in particular to an axially divided twin-volute turbine housing comprising first and second volute tongues defining different radii relative to a turbine axis so as to reduce the risk of thermo-mechanical fatigue crack initiation in the vicinity of the first and second volute tongues.
• Turbochargers are well known devices for supplying air to the intake of an internal combustion engines at pressures above atmospheric pressure (boost pressures) .
• a conventional turbocharger comprises an exhaust gas driven turbine wheel mounted on a rotatable shaft within a turbine housing. Rotation of the turbine wheel rotates a compressor wheel mounted on the other end of the shaft within a compressor housing. The compressor wheel delivers compressed air to the intake manifold of the engine, thereby increasing the amount of oxygen available for combustion and increasing engine power.
• the turbocharger shaft is conventionally supported by journal and thrust bearings, including appropriate lubricating systems, located within a central bearing housing connected between the turbine and compressor wheel housings.
• the turbine typically comprises a turbine housing defining a volute, a turbine wheel chamber, and an outlet passageway.
• exhaust gas is delivered to the volute by the internal combustion engine.
• the volute causes the exhaust gas to spiral inwardly about a turbine axis towards the turbine wheel.
• the turbine wheel comprises blades that receive an impulse from the exhaust gas so as to cause rotation of the turbine wheel about the turbine axis.
• the blades of the turbine wheel re-direct the exhaust gas so that it flows in a generally axial direction away from the turbine wheel and into the outlet passageway.
• the outlet passageway is connected to an aftertreatment system for chemical processing of the exhaust gas to reduce harmful emissions.
• the turbine housing is typically mounted to the bearing housing on an axially opposite side to the outlet passageway.
• the turbine housing comprises a mounting aperture for receiving a heat shield configured to protect the bearing housing from the heat of the exhaust gas passing through the turbine wheel.
• the mounting aperture is sized to fit circumferentially around and receive the heat shield and a portion of the bearing housing.
• the diameter of the mounting aperture is larger than the diameter of the inducer of the turbine wheel so as to enable the turbine wheel to be received within the turbine wheel chamber.
• Turbines may be of a single-entry or multiple-entry type.
• Single-entry turbines comprise a single volute that typically receives all of the exhaust gas from an internal combustion engine.
• Multiple-entry turbines comprise more than one volute which typically receive separate streams of exhaust gas from different cylinder banks of the internal combustion engine.
• One form of multiple-entry turbine is a “twin-entry” turbine in which two volutes are separated by a dividing wall in an axial direction.
• Each volute comprises a volute inlet that receives exhaust gas from the internal combustion engine and terminates in a respective volute tongue that radially separates the downstream exhaust gas from incoming exhaust gas entering the volute inlet.
• volute tongues as close as possible to the inducer portion of the turbine wheel improves the efficiency of the turbine by directing exhaust gas directly onto the turbine blades and minimising the amount of exhaust gas that is able to spill over the tongue and interact with the incoming exhaust gas from the volute inlets.
• the axial widths of volutes decreases with proximity to the turbine wheel and therefore positioning the volute tongues at such a close radial distance to the inducer portion of the turbine wheel requires a tight geometric arrangement. Often, this necessitates the use of small edge geometries (e.g. sharp fillets or radii between two joining surfaces) which induces high internal stresses and is therefore more susceptible to cracking due to thermo-mechanical fatigue.
• volute tongues closer to the inducer of the turbine wheel reduces the radial clearance between the tongue and the mounting aperture for the bearing housing. This may cause high internal stresses within the material of the turbine housing which may result in cracking due to thermo-mechanical fatigue cracking.
• an axially divided twin-volute turbine housing comprising: a first inlet volute defining a first volute tongue; a second inlet volute positioned axially adjacent to the first inlet volute relative to a turbine axis and defining a second volute tongue; and a dividing wall separating the first inlet volute from the second inlet volute; wherein the first volute tongue defines a first radius (R1) relative to the turbine axis and the second volute tongue defines a second radius (R2) relative to the turbine axis, the first radius (R1) being larger than the second radius (R2) .
• volute tongue encompasses the portion of the turbine housing that separates the most angularly downstream part of each respective volute from the incoming exhaust gas delivered to the turbine housing by the inlet conduits. Because the volute tongues are positioned at different radial distances from the turbine axis this ensures that one of the volute tongues is at a position where the respective volute has a greater axial width and therefore the tongue geometry (e.g. any fillets, radii, etc. ) do not need to be formed so tightly. Because the tongue geometry is formed less tightly, this reduces the chance of crack initiation at that volute tongue and slows the rate of crack propagation, thus increasing the in-service life of the turbine housing.
• the invention can be seen as striking a balance between reducing the chance of crack initiation and rate of crack propagation whilst maintaining high turbine efficiency.
• the turbine housing may further comprise: a turbine wheel chamber configured to contain a turbine wheel and to receive exhaust gas from the first inlet volute and the second inlet volute; an outlet passageway configured to receive exhaust gas from the turbine wheel chamber; and a mounting aperture on an opposite side of the turbine wheel chamber to the outlet passageway and configured for connection to a bearing housing.
• the first inlet volute may be adjacent to the mounting aperture and the second inlet volute may be adjacent to the outlet passageway. Because the first volute tongue has a larger radius than the second volute tongue and because the first inlet volute is on the same side of the turbine housing as the mounting aperture for the bearing housing, this ensures that there is a spacing between the mounting aperture and the first volute tongue.
• the first radius (R1) may be up to around 50 %larger than the second radius (R2) .
• the first radius (R1) may be between around 5 %to around 20 %, and preferably around 12 %larger than the second radius (R2) .
• the first volute tongue and the second volute tongue may be angularly aligned about the turbine axis.
• the first volute tongue may define a first angular position relative to the turbine axis; and the second volute tongue may define a second angular position relative to the turbine axis.
• the first angular position may be different to the second angular position. That is to say, the first volute tongue and the second volute tongue may be positioned at different angular positions. Because the tongues are at different angular positions, this provides reduced vibrational loading upon the turbine wheel and therefore improved high cycle fatigue performance.
• the first angular position and the second angular position may be spaced apart by up to around 180 °, or preferably up to around 90 °, or most preferably up to around 45 °.
• the dividing wall may be integrally formed with the turbine housing.
• a turbine comprising: an axially divided twin-volute turbine housing according to the first aspect of the invention: and a turbine wheel comprising an inducer portion defining a third radius (R3) .
• the first radius (R1) may be up to around 50 %larger than the third radius (R3) , or more preferably between around 15 %to 30 %larger than the third radius (R3) , or more preferably between around 20 %to 25 %larger than the third radius (R3) , or most preferably around 23 %larger than the third radius (R3) .
• the second radius (R2) may be up to around 20 %larger than the third radius (R3) , or preferably between around 5 %to around 15 %larger than the third radius (R3) , or most preferably around 10 %larger than the third radius (R3) .
• the turbine housing may be further comprise a bearing housing received within the mounting aperture.
• a turbocharger comprising a turbine according to the second aspect of the invention.
• Figure 1 is a schematic cross-sectional drawing of a known turbocharger
• Figure 2 is a schematic cross-sectional diagram of a turbine according to an embodiment of the present invention.
• Figure 3 is a schematic cross-sectional diagram of the turbine of Figure 2.
• Figure 4 is a schematic cross-sectional diagram of a further embodiment of a turbine according to the present invention.
• FIG. 1 shows a schematic cross-section through a known turbocharger.
• the turbocharger comprises a turbine 1 joined to a compressor 2 via a central bearing housing 3.
• the turbine 1 comprises a turbine wheel 4 for rotation within a turbine housing 5.
• the compressor 2 comprises a compressor wheel 6, of the centrifugal type, which can rotate within a compressor housing 7.
• the compressor housing 7 defines a compressor chamber within which the compressor wheel 6 can rotate.
• the turbine wheel 4 and compressor wheel 6 are mounted on opposite ends of a common turbocharger shaft 8 which extends through the central bearing housing 3.
• the turbine housing 5 has two inlet volutes 9 located annularly around the turbine wheel 4, and an axial exhaust gas outlet 10.
• the inlet volutes 9 are configured to receive exhaust gas from separate cylinder banks of the internal combustion engine.
• the compressor housing 7 has an axial air intake passage (compressor inlet) 11 and an outlet volute 12 arranged annularly around the compressor chamber.
• the outlet volute 12 is in gas flow communication with a compressor outlet 13 that delivers the compressed air onwards to an internal combustion engine (not shown) .
• the bearing housing 3 defines a bearing chamber through which the turbocharger shaft 8 passes.
• the shaft 8 is rotatably supported by a bearing assembly which comprises two journal bearings 14 and 15 housed towards the turbine end and compressor end respectively of the bearing housing 3.
• Oil is supplied to the bearing assembly from the oil system of the internal combustion engine via oil inlet 18 and is fed to the bearings 14, 15 by oil passageways 19.
• the oil fed to the bearings 14, 15 may be used to both lubricate the bearings and to remove heat from the bearings.
• the turbine wheel 4 is rotated about an axis 25 by the passage of exhaust gas from the exhaust gas inlet 9 to the exhaust gas outlet 10. Exhaust gas is provided to exhaust gas inlet 9 from an exhaust manifold (also referred to as an outlet manifold) of the engine. The turbine wheel 4 in turn rotates the compressor wheel 6 which thereby draws intake air through the compressor inlet 11 and delivers boost air to an inlet manifold of the engine via the volute 12 and then the outlet 13.
• the compressor chamber is defined between a shroud portion 17 of the compressor housing 7 and a hub portion 20 of the bearing housing 3.
• the compressor housing 7 shown in Figure 1 may be formed as a one-piece (i.e. integral) unit including the shroud portion 17, although in alternative embodiments may comprise multiple components.
• the shroud portion 17 has an inwardly facing shroud surface 21 which is circularly symmetric about the rotational axis 25.
• FIG. 2 shows a turbine 100 according to an embodiment of the present invention.
• the turbine 100 comprises an axially divided twin-volute turbine housing 102, a bearing housing 104, a turbine wheel 106 and a shaft 108.
• the turbine wheel 106 is mounted to the shaft 108 for rotation therewith, the shaft 108 in turn being supported for rotation about a turbine axis A by bearings 110 received within the bearing housing 104.
• the turbine housing 102 defines a first inlet volute 112, and a second inlet volute 114 separated by a dividing wall 116.
• the first and second inlet volutes 112, 114 are generally symmetrical, however it will be appreciated that in alternative embodiments the first and second inlet volutes 112, 114 may be asymmetrical.
• the dividing wall 116 extends generally orthogonally relative to the turbine axis A, and in this manner the turbine housing 102 is said to be ‘axially divided’ and ‘twin-volute’ . However, it will be appreciated that it is not necessary for the dividing wall 116 to be exactly orthogonal to the turbine axis A, and may in some embodiments be inclined relative to the orthogonal direction to the turbine axis A by up to 45 °.
• the turbine housing 102 further defines a turbine wheel chamber 117 containing the turbine wheel 106 an outlet passageway 118 which receives exhaust gas from the turbine wheel 106.
• first inlet volute 112 defines a first volute tongue 120 and the second inlet volute 114 defines a second volute tongue 122, which are shown superimposed in Figure 3 for clarity.
• the volute tongues 120, 122 define the most angularly downstream part of each respective volute 112, 114.
• the first volute tongue 120 defines a first radius R1 relative to the turbine axis A and the second volute tongue 122 defines a second radius R2 relative to the turbine axis A.
• Each radius R1, R2 is measured from the turbine axis A to the closest part of the relevant volute tongue 120, 122.
• Both the first volute tongue 120 and the second volute tongue 122 are positioned close to the turbine wheel 106. However, as shown in Figures 2 and 3, the first radius R1 is larger than the second radius R2.
• the first and second inlet volutes 112, 114 are generally symmetrical about a plane normal to the turbine axis A, and therefore the first volute tongue 120 and the second volute tongue 122 extend generally axially.
• the volute tongues 120 122 may be inclined relative to the turbine axis, for example as shown in US 10, 487, 676. In such cases, the radii of the volute tongues 120, 122 may be measured as the shortest distance between the turbine axis and the volute tongues 120, 122 in the radial direction.
• volute tongues 120, 122 As explained in the introduction, it is beneficial to position the volute tongues 120, 122 as close as possible to the turbine wheel 106 for the sake of turbine efficiency.
• the first radius R1 is greater than the second radius R2 this means that that the first volute tongue 120 is positioned at a location with greater axial width, thus enabling the use of more rounded edge geometry which reduces internal stresses and prolongs component lifetime. Nevertheless, the first volute tongue 120 remains in close enough proximity to the turbine wheel 106 so as to minimise any detrimental effects on turbine efficiency.
• the turbine housing 102 defines a mounting aperture 124 configured to receive a heat shield 125 for protecting the bearing housing 104 from the heat of the exhaust gas flowing through the turbine wheel 106.
• the first inlet volute 112 is positioned on the same side of the dividing wall 116 as the mounting aperture 124, and the second inlet volute 114 is positioned on the opposite side of the dividing wall 116. That is to say, the second inlet volute 114 is positioned on the same side of the dividing wall as the outlet passageway 118. Accordingly, the first inlet volute 112 is positioned adjacent to the mounting aperture 124 and the second inlet volute is positioned adjacent to the mounting aperture 124.
• first volute tongue 120 has a larger radius R1 than the radius R2 of the second volute tongue 122 and because the first inlet volute 112 is on the same side of the turbine housing 102 as the mounting aperture 124, this ensures that there is a spacing 126 between the mounting aperture 124 and the first volute tongue 120.
• the presence of such a spacing 126 acts to reduce the magnitude of any internal stresses within the material of the turbine housing by providing more room between edge geometry, and thereby correspondingly acts to reduce the likelihood of crack initiation due to thermo-mechanical fatigue in the vicinity of the first volute tongue 120.
• any cracks that do form will propagate more slowly, thus increasing the in-service life of the turbine housing.
• the first radius R1 is preferably no more than around 50 %larger than the second radius R2.
• the first radius R1 is no more than around 20 %larger than the second radius R2.
• the first radius is also preferably at least around 5 %larger than the second radius R2.
• first volute tongue 120 and the second volute tongue 122 are generally angularly aligned relative to the turbine axis A.
• This has the advantage that the housing 102 is relatively compact.
• this may result in high vibrational strain on the turbine wheel 106 due to a large fluidic force being applied to the turbine wheel 106 at a single angular position.
• the first volute tongue 120 defines a first angular position ⁇ 1 and the second volute tongue 122 defines a second angular position ⁇ 2 that is displaced from the first angular position ⁇ 1 by a displacement angle ⁇ .
• the displacement angle ⁇ should be no more than around 180 °, and is preferably up to around 90 °, or more preferably up to around 45 °. It has been found that the property of reduced vibrational loading of the turbine wheel 106 is provided irrespective of whether the first volute tongue 120 is positioned forward (relative to the direction of rotation of the turbine wheel 106 in use) of the second volute tongue 12 or vice versa.
• the dividing wall 116 is integrally formed with the turbine housing 102, such that the two are monolithic.
• the turbine housing 102 may be formed from casting, such as investment casting or sand casting.
• the turbine 100 does not comprise a variable geometry mechanism and therefore the turbine housing 102 may be said to be of a fixed geometry type.
• the function of the dividing wall 116 is principally to separate the first and second volutes 112, 114 from one another.
• the dividing wall 116 does not form part of or function to support any variable geometry mechanisms. Nevertheless, it will be appreciated that in alternative embodiments the turbine housing 102 may be incorporated within a variable geometry turbine.
• the turbine wheel 106 comprises an inducer portion 128.
• the inducer portion 128 is the part of the turbine wheel 106 that receives exhaust gas from the inlet volutes 112, 114.
• the inducer portion defines a third radius R3 relative to the turbine axis A.
• the first radius R1 is up to around 50 %larger than the third radius R3.
• the first radius is between around 15 %to 30 %larger than the third radius R3, or more preferably between around 20 %to 25 %larger than the third radius R3, or most preferably around 23 %larger than the third radius R3.
• the first radius R1 is larger than the third radius R3 by an amount within these ranges, this strikes a balance between the adverse effect on turbine efficiency and the improved thermo-mechanical fatigue performance afforded by increased spacing 126 between the mounting aperture 124 and the first volute tongue 120.
• the second radius R2 is no more than around 20 %larger than the third radius R3. In general, minimising the distance between the second radius R2 and the third radius R3 will further improve the efficiency of the turbine. Nevertheless, in order to enable the turbine wheel 106 to spin a clearance must be present between the tip 130 of the dividing wall 116 and the inducer portion 128 of the turbine wheel 106. Whilst the second volute tongue 122 can be at the same radial distance from the turbine axis A as the tip 130 of the dividing wall, it is nevertheless preferable that the second radius R2 is between around 5 %to around 15 %larger than the third radius R3, or most preferably around 10%larger than the third radius R3. When the first volute tongue 120 and the second volute tongue 122 are positioned at locations within the ranges given above, this provides a good balance between turbine efficiency and improved thermos-mechanical fatigue performance.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Supercharger (AREA)

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• 2024
  • 2024-02-28 EP EP24763200.3A patent/EP4673636A1/de active Pending
  • 2024-02-28 WO PCT/CN2024/079050 patent/WO2024179520A1/en not_active Ceased

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