Compressor wheel for a compressor of an internal combustion engine

Abstract

The invention relates to a compressor wheel for an exhaust-gas turbocharger of an internal combustion engine, comprising a hub which extends around a central axis of the compressor wheel and compressor wheel blades which are connected to the hub, the blade inlet edge of the compressor wheel blades extending in the radial direction and having an end region on the hub side and an end region which is radially remote from the hub, wherein the blade inlet edge is more blunt in the end region which is radially remote from the hub.

Description

TECHNICAL FIELD

[0001] The present invention relates to a compressor wheel for a compressor of an internal combustion engine. BACKGROUND

[0002] Exhaust-gas turbochargers are known. They have, inter alia, a turbine and a compressor, wherein the turbine is equipped with a turbine wheel and the compressor is equipped with a compressor wheel.

[0003] It is furthermore known to use exhaust-gas recirculation in the exhaust system of an internal combustion engine equipped with an exhaust-gas turbocharger in order to reduce the exhaust-gas emissions, in particular the nitrogen oxide emissions, which are undesirable in gasoline and diesel engines. In the case of external exhaust-gas recirculation, exhaust gas is taken out of the exhaust system. In particular when low-pressure exhaust-gas recirculation is used, the exhaust gas is taken out downstream of the exhaust-gas aftertreatment and input again upstream of the compressor of the exhaust-gas turbocharger after passing through the exhaust-gas aftertreatment. The mixing of exhaust gas with fresh air takes place in the compressor.

[0004] It is furthermore known to manufacture the compressor wheel of an exhaust-gas turbocharger in automotive applications by means of a milling process or a casting process. The milled compressor wheel is usually manufactured from a forgeable aluminum alloy.

[0005] In the operation of a motor vehicle, different components of the exhaust gas can cause damage on the compressor wheel. One damage mechanism is the corrosion of the compressor wheel material by corrosive elements in the exhaust gas. In addition to water vapor and carbon dioxide, the exhaust gas also contains harmful substances which are produced in the combustion process and particles which originate from the exhaust-gas aftertreatment.

[0006] Depending on the operating point of the internal combustion engine, water vapor condenses, thus forming water droplets. Not only the mentioned harmful substances but also the water droplets can lead to damage in the form of erosion after exhaust-gas recirculation when they impinge on the blade inlet edges of the compressor wheel. Such damage of the compressor wheel leads to a significant deterioration of the operating behavior and service life of the exhaust-gas turbocharger.

[0007] In order to protect the compressor wheel of an exhaust-gas turbocharger from corrosion as well as from particle and droplet damage, it is known to equip the compressor wheel with a coating, in particular a so-called NiP coating (chemical nickel).

[0008] In order to obtain the best possible fluid-mechanical properties, not only the main blades of the compressor wheel but also, if present, the splitter blades of the compressor wheel are made as thin and pointed as possible. As a result of this, the inlet edges of the compressor wheel blades are made sharply or slightly oval over their entire radial extension. Here, the shape of the main blade inlet edges corresponds to the shape of the splitter blade inlet edges, if present.

[0009] The thickening of the compressor wheel blades is to be avoided in order to improve the robustness of the compressor wheel against droplet and particle impacts, since such a thickening would have a disadvantageous effect on the fluid-dynamic and thermodynamic properties of the compressor. SUMMARY

[0010] The task of the present application is to configure a compressor of a turbocharger in such a way that the damage to the compressor wheel by components contained in the exhaust gas during operation of the motor vehicle is reduced.

[0011] This task is solved by a compressor wheel having the features specified in claim 1. Advantageous embodiments and refinements of the application are specified in the dependent claims. BRIEF DESCRIPTION OF DRAWINGS

[0012] The advantage of the present application lies, inter alia, in the fact that the robustness of the compressor wheel against droplet and particle impacts is improved compared to the prior art, while the deterioration of the fluid-dynamic and thermodynamic properties of the compressor is negligible. Further advantageous properties of the present application result from the following exemplary explanations thereof with the aid of the drawings, in which:

[0013] - Figure 1 a simplified diagram of a conventional compressor wheel is shown,

[0014] - Figure 2 simplified diagrams of two different conventional compressor wheels are shown,

[0015] - Figure 3 a simplified diagram for the graphical illustration of the end region of the shroud side of the blade entry edge of a conventional and of a compressor wheel blade according to the application is shown,

[0016] - Figure 4 a simplified diagram for the graphical illustration of the shape of the blade entry edge according to the application in the shroud region and in the hub region of a compressor wheel blade is shown,

[0017] - Figure 5 a further simplified diagram for the graphical illustration of the shape of the blade entry edge in the shroud region and in the hub region of a compressor wheel blade is shown,

[0018] - Figure 6 a further simplified diagram for the graphical illustration of the present application is shown, and

[0019] - Figure 7 a simplified diagram for the graphical illustration of a further embodiment of the present application is shown. DETAILED DESCRIPTION

[0020] Figure 1 a simplified diagram of a conventional compressor wheel is shown. Here,Figure 1 The simplified diagram on the left shows a perspective view of a conventional compressor impeller, and the simplified diagram on the right shows a cross-sectional view of this compressor impeller. The compressor impeller shown has a hub 2 extending around the central axis 1 of the compressor impeller. Compressor impeller blades 3a and 3b are disposed on this hub. Preferably, the hub and the compressor impeller blades disposed thereon are integrally formed as a single piece and are either milled or cast. The radially inner region of the hub 2 is hollowed out, so that the hub can be fastened to the shaft of the exhaust gas turbocharger.

[0021] The blades mentioned are the main blade 3a and the splitter blade 3b, wherein the splitter blade 3b is arranged between the two main blades 3a. The splitter blade 3b is shorter than the main blade 3a in the axial direction along the central axis 1 and is lower than the main blade in the radial direction. The main blade 3a has a main blade inlet edge 3c, which extends radially or mainly radially and has a hub-side end region 4 and a hub-away end region 5. The splitter blade 3b has a splitter blade inlet edge 3d, which also extends radially or mainly radially and has a hub-side end region and a hub-away end region, which, in the compressor impeller mounting state, are opposite to the guide profile of the surrounding compressor impeller housing or compressor frame, the so-called "shroud". The hub-away end region of the blade inlet edge is therefore also referred to in this specification as the "shroud-side end region" or "shroud region" or "shroud-side endpoint".

[0022] Here, the blade intake edge can extend outward in a straight, purely radial direction from the hub 2. However, there is also an embodiment in which the blade intake edge extends outward in an oblique, radially deviating from the straight radial direction or in an arc from the hub 2, which is summarized here under the phrase "mainly radial," which also includes the orientation along the purely radial direction.

[0023] As by Figure 1 It is evident that not only the air intake edges of the main blades but also the air intake edges of the splitter blades are sharply formed. Alternatively, they can also be made elliptical.

[0024] from Figure 1 In the cross-sectional view shown on the right, the hub 2 and the main blade 3a mounted on the hub are clearly visible. The intake edge 3c of the main blade 3a has an endpoint 6 in its end region 4 on the hub side, which is the connection point connecting the hub and the intake edge of the main blade. Furthermore, the intake edge 3c of the main blade 3a has an endpoint 7 in its end region 5 radially away from the hub 2, which is the endpoint on the shroud side of the intake edge of the main blade.

[0025] Figure 2 A diagram of two different conventional compressor wheels is shown.

[0026] Here, Figure 2 The diagram on the left-hand side shows a perspective view of a conventional compressor wheel which has main blades 3a and splitter blades 3b. Figure 1 The diagram on the right-hand side, however, shows a conventional compressor wheel which has only main blades 3a but no splitter blades 3b. Figure 2

[0027] Figure 3 A diagram for illustrating the shroud-side end region 5 of a conventional and of a blade entry edge according to the application of a compressor wheel blade is shown, which is a main blade.

[0028] Here, Figure 3 The shroud-side end region 5 of a conventional blade entry edge is shown on the left-hand side of

[0029] This is different on the right-hand side of Figure 2 The shroud-side end region 5 of a blade entry edge according to the application is shown on the right-hand side of

[0030] The blade entry edge is made elliptically in its end region on the hub side, which is not shown in Figure 3

[0031] In the case of a compressor wheel having main blades and splitter blades, the entry edge of the splitter blades is made sharply or elliptically over its entire radial extension as in the prior art. However, it is also possible that the entry edge of the splitter blades can also be made bluntly, for example semicircularly, over its entire radial extension.

[0032] The described blunt configuration of the front of the shroud-side end region of the blade entry edge of the main blades exists not only if the compressor wheel has main blades and splitter blades, but also if the compressor wheel has only main blades without splitter blades. Furthermore, the described blunt configuration of the front of the shroud-side end region of the blade entry edge of the main blades can be used not only in milled compressor wheels but also in cast compressor wheels.

[0033] Figure 4 A diagram for illustrating the shape of a blade entry edge according to the application in the shroud region and in the hub region of a compressor wheel blade is shown. ​​

[0034] In this case, a sketch is shown on the left-hand side in which the structure of the blade inlet edge in the shroud region is illustrated in a cross-section perpendicular to the blade inlet edge. Figure 4

[0035] In the present embodiment, the blade inlet edge is configured bluntly, here in particular semi-circularly, as outlined by the circle shown in dashed lines. The following relationship applies for the blunt configuration of the blade inlet edge:

[0036] a / b < 1

[0037] where "a" is the distance of the blade end to the centre point M of the rounding, and where "b" is the distance of the blade flank to the centre point M, which extends perpendicular to "a". Here, M is the centre point of the rounding of the blade inlet edge, which is determined in the cross-section by the intersection of the chord line of the blade with the line extending through the transition point between the blade flank and the start of the rounding.

[0038] For the structure of the blade inlet edge in the shroud region shown in Figure 4 the centre point of the mentioned circle or semi-circle is denoted by the letter M, and the relationship a / b = 1 applies here. In further configurations, the ratio a / b can advantageously be a / b < 0.8, in particular also a / b < 0.5, which represents a more blunt configuration.

[0039] On the right-hand side of Figure 4 a sketch is shown in which the structure of the blade inlet edge in the hub region is illustrated. In the present embodiment, the blade inlet edge is configured sharply, here in particular elliptically, in the hub region, as outlined by the ellipse shown. Here, the relationship indicated in the sketch applies for the sharp configuration:

[0040] a / b > 1, for example a / b = 3.

[0041] For the structure of the blade inlet edge in the hub region shown in Figure 4 the centre point of the mentioned ellipse is denoted by the letter M.

[0042] Figure 5 A further sketch for illustrating the shape of the blade inlet edge in the shroud region and in the hub region of a compressor wheel blade is shown.

[0043] ​As can be seen from this simplified diagram, in the prior art, the inlet edge of the compressor impeller blade shown is elliptical, i.e., sharp, in its end region away from the hub, while in the present invention it is more blunt, preferably semi-circular. Furthermore, as can be seen from this simplified diagram, the inlet edge of the compressor impeller blade shown is elliptical in its hub region, both in the prior art and in the present invention.

[0044] Figure 6 Another simplified diagram is shown for illustrating the invention.

[0045] exist Figure 6 In the diagram shown on the left, the radial position *r* at the inlet edge of the main blades of the compressor impeller is drawn upwards, and the ratio *a / b* of the half-shaft is drawn to the right. Figure 6 The simplified diagram shown on the right illustrates a cross-sectional view of a portion of the compressor impeller, which in particular reveals the entire radial extension of the blade inlet edge.

[0046] It can be seen that in the outer diameter region B of the blade intake edge, that is, in the end region of the blade intake edge away from the hub, the blade intake edge is formed to be relatively blunt, while in the inner diameter region A, that is, in the end region of the blade intake edge on the hub side, it is formed to be elliptical.

[0047] In the illustrated embodiment, the outer diameter region B approximately corresponds to half the radial extension of the blade inlet edge. Figure 6 The diagram shown on the left illustrates the relevant ratio a / b of the half-axis at the corresponding position r on the inlet edge of the blade, in the form of a range window. All geometries can exist within this range window.

[0048] exist Figure 7 Different embodiments are shown. Particularly, the direction of the blade intake section from the hub towards the shroud side, i.e., the direction of the blade intake edge from the end point 6 of the end section 4 on the hub side to the end section 5 away from the hub (see [reference]). Figure 6 The linear orientation of the ratio a / b of the half-axis is possible, as in... Figure 7 The diagram on the upper left is as illustrated. Furthermore, a discontinuous transition from a pointed to a blunt shape in the inlet edge of the compressor impeller blades is possible, such as... Figure 7 As illustrated in the middle and right side diagrams, the transition from an elliptical shape to a blunt shape is geometrically smooth. Furthermore, it is possible to achieve the blunter region of the blade's intake edge through a combination of semi-circular and elliptical shapes, as in... Figure 7The upper right corner is outlined by the letters k and e. Here, the side surface of the compressor blade runs in the region before the more blunt rounded transition of the blade inlet edge via a partial region on an elliptical trajectory towards the blade inlet edge.

Claims

1. A compressor impeller for an exhaust gas turbocharger of an internal combustion engine, the compressor impeller comprising a hub (2) extending about a central axis (1) of the compressor impeller and compressor impeller blades (3a) disposed on the hub, the inlet edge (3c) of the compressor impeller blades extending primarily in the radial direction and having an end region (4) on the hub side and an end region (5) radially away from the hub, characterized in that, The blade intake edge (3c) is bluntly formed in its radially distant end region (5) from the hub, and the blade intake edge (3c) is sharp and elliptical in its hub-side end region (4).

2. The compressor impeller according to claim 1, characterized in that, The blade intake edge (3c) is semi-circularly formed in the end region (5) that is radially away from the hub.

3. The compressor impeller according to claim 1, characterized in that, The compressor impeller blade (3a) is the main blade.

4. The compressor impeller according to claim 3, characterized in that, In addition to the main blades, the compressor impeller also has a splitting blade (3b), the inlet edge (3d) of which extends radially and has an end region on the hub side and an end region radially away from the hub.

5. The compressor impeller according to claim 4, characterized in that, The air intake edge (3d) of the splitter blade (3b) is sharply or elliptically formed over its entire radial extension.

6. The compressor impeller according to claim 4, characterized in that, The air intake edge (3d) of the splitter blade (3b) is bluntly formed over its entire radial extension.

7. The compressor impeller according to claim 6, characterized in that, The air intake edge (3d) of the splitter blade (3b) is semi-circularly formed over its entire radial extension.

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