Flanged connection of a turbocharger to an exhaust manifold

Abstract: An internal combustion engine has a turbocharger inlet flange (19) mounted to the outlet flange (21) of the exhaust manifold (16) of the engine. The exhaust gas flow out of the manifold (16) is through two ports (46 and 47) having a centrally located guide wall directing flow from the manifold (16) out the flange (21) into the turbocharger inlet. The two ports (46 and 47) are trapezoidal in shape with a short common dividing wall which, for each port (46,47), blends at a short radius into two diverging straight walls, one at each end of the common wall, and which blend from their ends into the outer wall of the port (46,47), resulting in a trapezoidal port shape. The inlet flange (19) of the turbocharger casing has ports matching and in registry with the two ports (46 and 47) of the exhaust manifold flange (21).

Description: This invention relates generally to an internal combustion engine exhaust manifold flange for receiving thereon a turbocharger casing inlet flange, the exhaust manifold flange having four outer corners and two exhaust ports inboard of the corners, the ports having a common dividing wall, each port having two generally straight walls extending outward from the dividing wall towards two of the corners, and each port having an outer wall extending generally parallel to the dividing wall. The invention also relates generally to an exhaust inlet flange in a turbocharger casing, the exhaust inlet flange having four outer corners and two exhaust ports inboard of the corners, the ports having a common dividing wall, each port having two generally straight walls extending outward from the dividing wall towards two of the corners, and each port having an outer wall extending generally parallel to the dividing wall. Furthermore, the invention relates generally to an internal combustion engine exhaust manifold outlet to turbocharger inlet assembly. The invention also generally relates a turbocharger casing for mounting to an engine exhaust manifold outlet flange comprising a turbine intake passageway inlet face having four outer corners for receiving fasteners for connection to an engine exhaust manifold flange, said inlet face having two exhaust ports inboard of the corners, the ports having a common dividing wall, each port having two generally straight walls extending outward from the dividing wall towards two of the corners and each port having an outer wall extending generally parallel to the dividing wall. In many multi-cylinder in-line engines, the exhaust manifold has a flange to which a turbocharger is mounted. The exhaust passageways from the opposite ends of the engine merge towards the flange, but there is a dividing wall in the region of the manifold near the flange, for guiding and improving the exhaust gas flow from the opposite ends into the turbocharger. UK Patent Application GB 2 095 329 discloses an exhaust manifold flange to connect with a turbocharger turbine and an internal combustion engine exhaust manifold outlet to turbocharger inlet assembly in which the exhaust manifold outlet flange or portion has four outer corners and two exhaust ports in board of the corners, the ports having a common dividing wall, each port having two generally straight walls extending outward from the dividing wall towards two of the corners, and each port having an outer wall extending generally parallel to the dividing wall. The branch ducts which receive exhaust gases from pairs of engine cylinders are formed symmetrically with respect to the ports in the exhaust manifold flange, or with respect to the centre of that flange. Similarly, in some turbochargers, the exhaust gas inlet flange of the casing has a dividing wall considered desirable for its effect of the direction of the gas flow to the turbine. UK Patent Application GB 1 370 962 discloses a turbocharger housing having a flanged inlet end designed to be bolted or otherwise secured to the outlet end of a divided exhaust housing. This document describes a turbine intake passageway inlet face or exhaust inlet flange having four outer corners for receiving fasteners for connection to an engine exhaust manifold flange, the inlet face or flange having two exhaust ports inward of the corners, the ports having a common dividing wall, each port having two generally straight walls extending outward from the dividing wall towards two of the corners, and each port having an outer wall extending generally parallel to the dividing wall. In such cases, it is desirable that the exhaust manifold flange to which the casing flange is mounted, and the gasket between the turbocharger casing flange and the manifold flange, also having a dividing wall at the mating mounting flanges. With conventional arrangement, cracking at the dividing wall of the flange on the turbocharger casing and at the dividing wall of the manifold flange has occurred after a prolonged period of use. It is believed that this cracking is the result of thermal stresses occurring as an engine warms up or endures changes in power output, either of which changes the exhaust temperature. There has been a need to extend the life of manifold-to-turbocharger flanges. According to a first aspect of this invention there is provided an exhaust outlet manifold outlet flange of an internal combustion engine for receiving thereon a turbocharger casing inlet flange, the exhaust outlet manifold flange having four outer corners and two exhaust ports inboard of the corners, the exhaust ports having a common dividing wall, each exhaust port having two generally straight walls extending outward from the common dividing wall towards two of the corners, and each exhaust port having an outer wall extending generally parallel to the common dividing wall, characterised in that the two generally straight walls of each exhaust port diverge from the common dividing wall towards the respective outer wall so that each of the exhaust ports has a generally trapezoidal shape, the length of the common dividing wall being less than the length of each outer wall. According to a second aspect of this invention there is provided a turbocharger casing for mounting to an engine exhaust manifold outlet flange, comprising an exhaust inlet flange having four outer corners and two inlet ports inboard of the corners, the inlet ports having a common dividing wall, each inlet port having two generally straight walls extending outward from the common dividing wall towards two of the corners, and each inlet port having an outer wall extending generally parallel to the common dividing wall, characterised in that the two generally straight walls of each inlet port diverge from the common dividing wall towards the respective outer wall so that each of the inlet ports has a generally trapezoidal shape, the length of the common dividing wall being less than the length of each outer wall. According to an embodiment of this invention, an internal combustion engine exhaust manifold outlet flange is provided with at least two ports for discharging exhaust gas into a turbocharger inlet, the two ports having a common dividing wall, each port having two walls diverging from the common wall toward an outer wall in a manner creating a generally trapezoidal port cross sectional configuration at the flange, the length of the common wall at the face of the flange being less than that of any of the other three walls of the trapezoid, at each end of the common wall, there being a small radius blending from the common wall to the adjacent divergent straight wall where thermal stress is distributed along the length of the straight wall, avoiding stress concentration, and the turbocharger casing exhaust inlet flange being of the same configuration as the exhaust manifold flange and the two being bolted together with the gas flow ports in registry with each other. It will be appreciated that, in this specification, the term trapezoidal should be taken to have its American English meaning, i.e. a quadrilateral having two parallel sides, rather than its meaning in British English. Description of the Preferred Embodiment For the purposes of promoting an understanding of the principles of the invention, preferred embodiments will be described by way of example, and with reference to the accompanying drawings. Brief Description of the Drawings Fig. 1 is a diagrammatic rear end view of a diesel engine including exhaust manifold, turbocharger, and intake manifold. Fig. 2 is a face view showing a prior art turbocharger case mounting flange configuration. Fig. 3 is a face view of the exhaust manifold outlet flange connection in which the present invention is embodied. Fig. 4 is a face view of a turbocharger inlet flange in which the present invention is embodied. Fig. 5 is a fragmentary side-elevational view of the engine showing the turbocharger secured to the exhaust manifold. Fig. 6 is a fragmentary top plan view on a larger scale with portions of the exhaust manifold wall broke out to show the outlet passages from the front and rear portions of the exhaust manifold into the turbocharger mounting flange. Referring now the drawings in detail, Fig. 1 illustrates an internal combustion diesel engine 11 having a cylinder block 12, cylinder head 13, intake manifold 14, exhaust manifold 16, and turbocharger 17. The turbocharger casing intake passageway 18 to the turbine therein has a mounting flange 19 mounted on the exhaust manifold flange 21, with a gasket 22 between the flanges. The flanges are held together by bolts 23. The turbocharger outlet 24 is piped through an intercooler (not shown) to the inlet 26 of the intake manifold 14. The other end of the intake manifold is mounted by flange 27 to the cylinder head 13. Similarly, the exhaust manifold 16 is mounted to the opposite side of the cylinder head by flanges 28. The flanges of particular interest for the purposes of the present invention are flanges 19 and 21 where the turbocharger is fastened to the exhaust manifold. Fig. 2 shows the configuration of a prior art exhaust manifold outlet flange face 31. It has two generally rectangular ports 32 and 33 and a dividing wall 34 considered useful for directing exhaust flow form the exhaust manifold into the turbocharger turbine (not shown). The ports 32 and 33 are identical and separated by the common centre dividing wall 34. When flange face 31 is considered with reference to intersecting planes 30 and 35 which are perpendicular to the plane of face 31 and to each other, it is symmetrical about both planes. Port 32 to the left of plane 35 is D-shaped. Port 33 is a mirror image thereof. After a significant period of use in service, cracking has occurred at one or more of the regions 36. Referring now to Fig. 3, the exhaust manifold outlet flange of the present invention is symmetrical with respect to two planes 41 and 42 which are perpendicular to each other and perpendicular to the plane of the face 43 of the flange. Those portions of the flange to the right-side of plane 42 are mirror images of those at the left-side of plane 42. Similarly, the portions above plane 41 are mirror images of those below plane 41. The turbocharger is of the twin entry type having a center guide wall 45 (Fig. 4) extending from the flange 360° around the volute and connected on both sides for a length of about 5 centimeters (cm.) into casing 18. The rear portion of the exhaust manifold for the back three cylinders, and the front portion of the exhaust manifold for the front three cylinders blend into the center dividing wall 44 at flange 21 which is in registry with wall 45 of the turbocharger casing inlet flange 19 and divides the exhaust passage into the flange 21 into two ports 46 and 47 which are mirror images of each other and share the common wall 44. It is important that the area of the ports 46 and 47 be at least equal to the area of the ports 32 and 33 of the flange of the prior art (Fig. 2), if they are to serve the same engine, which is the intent. But the configuration makes a large difference in longevity. In this example, that portion of wall 44 facing the port 46 blends at inner transition regions 48 and 49 of less than 7 mm radius, and/or a length of 8% or less (each) of the port perimeter, into the straight walls 51 and 52 which as they extend outward from the center wall 44, diverge from a plane parallel to plane 41 at a trapezoidal angle A of 30 to 35°. These walls 51 and 52 blend at outer transition regions in a smooth curve such as at 53 for wall 52, into an intermediate straight wall 54 which blends at 56 into a straight wall 57 parallel to wall 44. The configuration of each other quarter section (with respect to planes 41 and 42) of the flange and the port through it is the same as, or a mirror image of the quarter section just described. Thus, each port, whether considered as a quarter section of the face or in its entirety, has a trapezoidal shape. Since there are the four bolt holes 58 at the four remote corners of the flange, and it is necessary to provide sufficient wrench clearance centered on those bolt holes, and this is a particularly important consideration for smaller engines with smaller manifolds and turbocharger flanges, the intermediate wall 54 is preferably located tangent to a circle 59 centered at the bolt hole 58. The same port wall relationship is established for all four bolt holes. Due to the configuration of the flange of the present invention, the pair of ports 46 and 47 together with common wall 44 resembles a bow tie. This configuration enables the ports to have the same area as in the prior art flange of Fig. 2 while preserving the relationship of the bolt holes 58 which have the same spacing as in the prior art flange of Fig. 2. In order to reduce thermal inertia and stiffness of surrounding constraining material in the flanges, and thereby improve transient response, provide suitable thermal stress distribution and lower stress, and yet provide adequate port size and gasket sealing width as at locations B and C, for example in Fig. 3, the sides are scalloped as at D, and E. As an example, where the distance between the bolt holes measured in a direction perpendicular to the plane 42 is 127 mm, and the distance between the bolt holes measured in a direction perpendicular to the plane 41 is 85.8 mm, the depth of the scallop side at F is 11.1 mm and at E is R = 35 mm to a depth of G = 15 mm. As indicated above, there is a gasket between the two flanges. Typically it is stainless steel with a small bead on one face around the pair of ports 46 and 47. The configuration of the gasket and the inlet ports in the turbocharger inlet flange face (Fig. 4) engaging the gasket, is identical to the configuration and ports of the manifold exhaust outlet flange face except that on the gasket there is no dividing wall in the location of flange walls 44 45. The preferred minimum gasket sealing width at B and C in Fig. 3 is 13 mm. The minimum desired wrench clearance radius WCR is 21.8 mm. By comparison of the illustrations of Fig. 2 and Fig. 3, and although the drawings are not to scale, it should be noted that the length L of the center wall 44 of the flange according to the present invention is much less than that of the center wall 34 of the prior art flange. It is preferable that this length be no greater than 15.5 percent of the total internal perimeter of the port 47 at the flange face 43. It is also desirable that the length of the straight wall 52 at the trapezoidal angle A be at least 22.0 percent of the total internal perimeter of the port 46 and that the length of the curved transition wall 49 be equal to or less than 8% of the total internal perimeter of port 46. It is also desirable that the trapezoidal angle A be at least 30°. Fig. 4 shows the exhaust inlet flange 19 of the turbocharger casing 18. The configuration is identical to that of Fig. 3, and the ports and holes thereof are in registry with those of the exhaust manifold flange of Fig. 3. The faces of the flanges 21 and 19 are flat. The material of both the turbocharger housing flange and manifold flange is ductile iron. Changing from the D-shaped port of the prior art to the trapezoidal port shape of the present invention minimizes the length of the center dividing wall between the ports, while maximizing port area. Decreasing the size of the center dividing wall blend radius 49 (Fig. 3) from that at 61 (Fig. 2) of the prior art, moves the thermal stress concentration into a lower stress area. The result is that thermal stress is distributed along the long straight side 51, 52 of the trapezoid, resulting in minimal stress concentration. Thus, the present invention: 1. Maintains required port cross sectional area; 2. Maintains wrench clearance for attachment hardware; 3. Minimizes transient thermal stresses of a type which causes cracking; 4. Maintains the current bolt pattern size; 5. Minimizes the cost and complexity of the components; and 6. Maintains sufficient width for the gasket which seals this joint. It will be recognized that the use of two straight portions such as 54 and 57 with a blend 56 between them in the outer wall two quartets from diverging wall 51 to diverging wall 52 of each port helps optimize port area. A curved wall could be used in these quarters and still provide a generally trapezoidal port with its advantages according to the present invention. In either case, the length L of the common wall is less than half the length of the outer wall between the ends of the diverging walls 51 and 52.

Claims: An exhaust manifold outlet flange (21) of an internal combustion engine for receiving thereon a turbocharger casing inlet flange (19), the exhaust manifold outlet flange (21) having four outer corners and two exhaust ports (46,47) inboard of the comers, the exhaust ports (46,47) having a common dividing wall (44), each exhaust port (46,47) having two generally straight walls (51,52) extending outward from the common dividing wall (44) towards two of the corners, and each exhaust port (46,47) having an outer wall (57) extending generally parallel to the common dividing wall (44), characterised in that the two generally straight walls (51,52) of each exhaust port (46,47) diverge from the common dividing wall (44) towards the respective outer wall (57) so that each of the exhaust ports (46,47) has a generally trapezoidal shape, the length of the common dividing wall (44) being less than the length of each outer wall (57). An exhaust manifold outlet flange (21) according to claim 1 wherein the length of the common dividing wall (44) is no greater than 15.5% of the total internal perimeter of one of the ports (47) at the flange face (43). An exhaust manifold outlet flange (21) according to claim 1 or claim 2 wherein the exhaust manifold outlet flange (21) has a face having a shape which is symmetrical with respect to first (42) and second (41) planes, which first (42) and second (41) planes are mutually perpendicular and perpendicular to said face, and wherein the two generally straight walls (51,52) of one of the exhaust ports (46) diverge with reference to the second plane (41) towards one pair of corners on one side of the first plane (42), and the other two generally straight walls (51,52) of the other exhaust port (47) diverge with reference to the second plane (41) towards the other pair of corners on the opposite side of the first plane (42), and wherein the second plane (41) is perpendicular to the first common dividing wall (44) and bisects the common dividing wall (44), and the first plane (42) is parallel to the common dividing wall (44). An exhaust manifold outlet flange according to claim 1 or claim 3 comprising for each exhaust port (46,47) first transition walls (48,49) between the common dividing wall (44) and the two outwardly extending generally straight walls (51,52), and second transition walls (53,54) between the outwardly extending generally straight walls (51,52) and the outer wall (57). An exhaust manifold outlet flange according to claim 4, wherein each of the first transition walls (48,49) between the common dividing wall (44) and the outwardly extending generally straight walls (51,52) is curved with at least one radius less than 7mm. An exhaust manifold outlet flange according to claim 5, wherein each of the first transition walls (48,49) between the common dividing wall (44) and the outwardly extending generally straight walls (51,52) has a length not exceeding eight percent of the internal perimeter of the respective exhaust port (46,47). An exhaust manifold outlet flange according to claim 6, wherein each of the second transition walls (53,54) between the outwardly extending generally straight walls (51,52) and the outer wall (57) has a short straight portion (54) and a curved portion (53, 56) at each end of the short straight portions (54), and the two exhaust ports (46,47) are mirror images of each other. A turbocharger casing (17) for mounting to an engine exhaust manifold outlet flange (21), comprising an exhaust inlet flange (19) having four outer corners and two inlet ports inboard of the corners, the inlet ports having a common dividing wall (45), each inlet port having two generally straight walls extending outward from the common dividing wall (45) towards two of the corners, and each inlet port having an outer wall extending generally parallel to the common dividing wall (45), characterised in that the two generally straight walls of each inlet port diverge from the common dividing wall (45) towards the respective outer wall so that each of the inlet ports has a generally trapezoidal shape, the length of the common dividing wall (45) being less than the length of each outer wall. A turbocharger casing (17) according to claim 8 wherein the length of the common dividing wall (45) is no greater than 15.5% of the total internal perimeter of one of the ports at the flange face. A turbocharger casing (17) according to claim 8 or claim 9 in which the exhaust inlet flange (19) comprises a turbine intake passageway inlet face, the four outer corners of which are for receiving fasteners for connection to an engine exhaust manifold flange (21). A turbocharger casing (17) according to claim 8 or claim 10, wherein the outwardly extending generally straight walls of a first one of said inlet ports extend from one side of the common dividing wall (45) and the outwardly extending walls of a second one of said inlet ports extend from the other side thereof. A turbocharger casing (17) according to claim 11, wherein each outwardly extending generally straight wall extends outward from the common dividing wall at an angle of between 120 and 125 degrees. A turbocharger casing (17) according to claim 12, wherein each outwardly extending generally straight wall blends into an end of the common dividing wall (45) in a transition blend whose length is no greater than eight percent of the perimeter of the respective inlet port. A turbocharger casing (17) according to claim 13, wherein said outer wall of each inlet port extends between the outer ends of the generally straight walls which extend from the common dividing wall (45) and which is about twice as long as the common dividing wall (45). A turbocharger casing (17) according to any one of claims 11 to 14 when dependent on claim 10, wherein the outer perimeter wall of the turbine intake passageway inlet face is scalloped with a first curve through a first plane above a second plane and a second curve through the first plane below the second plane, the first and second planes being mutually perpendicular and perpendicular to said face, the first plane being parallel to the common dividing wall (45), the second plane being perpendicular to the common dividing wall (45), and the shape of the face being symmetrical with respect to the first plane. A turbocharger casing (17) according to claim 15, wherein the curves are centred in the first plane. A turbocharger casing (17) according to claim 15, wherein the outer perimeter wall includes straight portions extending from the curves out to the corners, two of the straight portions diverging with reference to the second plane as they extend out from the curves to the corner on one side of the first plane, and two of the straight portions diverging with reference to the second plane as they extend out from the curves to the corners on the opposite side of the first plane. A turbocharger casing (17) according to claim 8 or Claim 10, comprising for each inlet port first transition walls between the common dividing wall (45) and the two outwardly extending generally straight walls, and second transition walls between the outwardly extending generally straight walls and the outer wall. A turbocharger casing (17) according to claim 18, wherein each of the first transition walls between the common dividing wall (45) and the outwardly extending walls is curved with at least one radius less than 7mm. A turbocharger casing (17) according to claim 19, wherein each of the first transition walls between the common dividing wall and the outwardly extending generally straight walls has a length not exceeding eight percent of the internal perimeter of the respective inlet port. A turbocharger casing (17) according to claim 18, wherein each of the second transition walls between the outwardly extending generally straight walls and the outer wall has a short straight portion and a curved portion at each end of the short straight portions, and the two inlet ports are mirror images of each other. An internal combustion engine exhaust manifold outlet to turbocharger inlet assembly comprising an exhaust manifold outlet flange (21) according to any one of claims 1 to 7 and a turbocharger casing (17) according to any of claims 8 to 21. An exhaust manifold outlet flange according to any one of claims 1 to 7, or an assembly according to claim 22, wherein the length of the respective common dividing wall (44,45) between each of the two respective ports (46,47) of a flange (19,21) is less than the length of any of the other three walls (51,52,57) of the respective ports (46,47). An assembly according to claim 22 or claim 23, wherein the exhaust manifold outlet flange (21) has a bolt hole (58)in each of the four corners thereof, the turbocharger inlet flange (19) has a bolt hole in each of the four corners thereof, and bolts received in the bolt holes (58) fasten the turbocharger inlet flange (19) and the exhaust manifold outlet flange (21) together. An assembly according to claim 24, further comprising a gasket (22) sandwiched between the turbocharger inlet flange (19) and the exhaust manifold outlet flange (21) and having a port in registry with the exhaust ports (46,47) of the exhaust mainfold outlet flange (21) and the inlet ports of the turbocharger inlet flange (19) and shaped like the exhaust ports (46,47) of the exhaust manifold outlet flange (21) and the inlet ports of the turbocharger inlet flange (19) but without a common dividing wall (44,45).

Inventors: BAKER GLENN L, RAUB JONATHAN H, BAKER, GLENN L., RAUB, JONATHAN H.
Applicants: CUMMINS ENGINE CO INC, CUMMINS ENGINE COMPANY, INC.
Application year: 1995
Main classification: F02B37
IPC codes: F01D9, F02B37, F02B39, F02B67, F01N13