WO2020001752A1

WO2020001752A1 - A compressor device for an internal combustion engine

Info

Publication number: WO2020001752A1
Application number: PCT/EP2018/067112
Authority: WO
Inventors: Peter TENNEVALL
Original assignee: Volvo Truck Corporation
Priority date: 2018-06-26
Filing date: 2018-06-26
Publication date: 2020-01-02

Abstract

The invention relates to a compressor device (20) for a turbo-charging arrangement of an internal combustion engine (1), the compressor device (20) comprising: a compressor housing (2); a compressor rotor (5) with blades arranged inside the compressor housing (2), wherein the compressor rotor (5) is arranged to rotate around an rotational axis (15); and an annular shroud member (6) mounted in the compressor housing (2) around the rotational axis (15) between the blades and the compressor housing (5). The invention is characterized in that an annular mounting flange (7) is provided for mounting the shroud member (6) to the compressor housing (2), wherein the shroud member (6) is made of a first material having a first thermal expansion coefficient, wherein the mounting flange (7) is made of a second material having a second thermal expansion coefficient, and wherein the compressor housing (2) is made of a third material having a third thermal expansion coefficient, wherein each of the second and third thermal expansion coefficients is smaller than the first thermal expansion coefficient, wherein the shroud member (6) is arranged in relation to the mounting flange (7) and the compressor housing (2) so that a radial clearance (C1, C2, C3) is provided at room temperature between the shroud member (6) and radially mating surfaces of the mounting flange (7) and the compressor housing (2). The invention also relates to an engine provide with such a compressor device and to a vehicle provided with such an engine. The invention further relates to a shroud member for use in a compressor device of the above type.

Description

A compressor device for an internal combustion engine

TECHNICAL FIELD

The invention relates to a compressor device for a turbo charging arrangement of an internal combustion engine. It also relates to an engine provided with such a compressor device and to a vehicle provided with such an engine. The invention further relates to a shroud member for use in a compressor device of the above type.

The invention can be applied in heavy-duty vehicles, such as trucks, buses and construction equipment. Although the invention will be described with respect to a truck it may also be used in other vehicles such as buses, construction equipment, cars and boats etc.

BACKGROUND

Compressors are widely used in the area of internal combustion engines. Commonly, the purpose of the compressor is to compress intake air to be fed to the engine and a compressor rotor is typically driven via an exhaust gas turbine in a turbo charging arrangement.

Such a compressor typically comprises a compressor housing, a compressor rotor with blades and an annular shroud mounted in the compressor housing between the blades and the compressor housing.

It is well known that the compression efficiency can be increased by decreasing the gap between the blades and the shroud. However, decreasing this gap increases the risk of having the blades damaged if they come into contact with the shroud due to vibrations or for some other reason.

A known solution to this problem is to provide the shroud with an abradeable material that reduces the risk of damages to the blades. Such a material, or at least the process for applying such a material onto a shroud made of e.g. aluminium, is rather costly.

US2017/0350408A1 discloses another approach, namely to make use of thermoplastic material for forming the shroud or at least a part of the shroud. A general challenge of using thermoplastic material together with a metal in an elevated temperature environment is the significant difference in thermal expansion rate. Teflon for instance has a linear thermal expansion coefficient of 120x1 O ⁶ (K ¹) compared to 23x1 O ⁶ (K ¹) for aluminium, which makes it difficult having a conventional press fit support and guiding design without getting distortion and plastic deformation. The structure proposed in US2017/0350408A1 is relatively complex and since the structure involves radial pressfitting it appears that a relatively greater radial expansion of the thermoplastic material at elevated temperatures may lead to stress and tension in at least the radial direction of the structure. This is undesirable since it might result in, for instance, durability problems.

There is thus still a need for a less costly and less complex compressor device that allows for a minimized gap between blades and shroud without risking damage of the blades or building up of internal tensions in the device.

SUMMARY

An object of the invention is to provide a compressor device that allows for a minimized gap between blades and shroud without requiring any abradeable coating and without building up of internal tensions. Although the invention is described mainly in relation to turbochargers it is applicable also in other compressor devices of similar type.

According to a first aspect of the invention, the object is achieved by a compressor device for a turbo-charging arrangement of an internal combustion engine, the compressor device comprising: a compressor housing; a compressor rotor with blades arranged inside the compressor housing, wherein the compressor rotor is arranged to rotate around a rotational axis; and an annular shroud member mounted in the compressor housing around the rotational axis between the blades and the compressor housing.

The device is characterized in that an annular mounting flange is provided for mounting the shroud member to the compressor housing, wherein the shroud member is made of a first material having a first thermal expansion coefficient, wherein the mounting flange is made of a second material having a second thermal expansion coefficient, and wherein the compressor housing is made of a third material having a third thermal expansion coefficient, wherein each of the second and third thermal expansion coefficients is smaller than the first thermal expansion coefficient, wherein the shroud member is arranged in relation to the mounting flange and the compressor housing so that a radial clearance is provided at room temperature between the shroud member and radially mating surfaces of the mounting flange and the compressor housing.

The shroud member can thus expand radially at these clearances when the temperature increases without pressing onto parts of the mounting flange or of the compressor housing, which expand less than the shroud member. In other words, the relative dimensions of the shroud member allows for radial thermal dimensions of the shroud member without generating tension in the structure due to different thermal expansion coefficients of different materials in the shroud member on the one hand and the mounting flange and the compressor supporting on the other hand. This allows for the use of e.g. Teflon or other suitable thermoplastic material for the shroud member, while the mounting flange and the compressor housing can be made of different or the same metallic material, e.g. both can be made of aluminium (in which case the second and third materials as well as the second and third thermal thermal expansion coefficients are the same). In turn, the gap between the blades and the shroud member can be decreased compared to the case where also the shroud is made of aluminium since a thermoplastic material does not damage the blades. Teflon and similar materials have the further advantage that soot and dirt etc. stick to the surface to a lesser extent than to a surface of e.g. aluminium.

It is not necessary for the principle of the invention that there are radially mating surfaces on both the mounting flange and the compressor housing, the compressor device may be arranged so that radially mating surfaces are arranged on only one of these components or on additional parts that can be regarded to form part of the mounting flange or the compressor housing, but in most embodiments the structure as a whole can be made less complex if there are radially mating surfaces arranged on both the mounting flange and the compressor housing.

The term“room temperature” is a well-established notion used to denote a typical indoor temperature, i.e. around 20-22°C. The temperature of the compressor device increases when started and it reaches a much higher steady-state operation temperature, perhaps around 100°C, after some time. (The normal operation temperature varies among different types and sizes of compressor devices and depends also on the particular application and operational condition.) At the higher temperature the material with the larger thermal expansion coefficient will have expanded more than the other material(s).

In an embodiment the magnitude of the radial clearance is adapted to be closed by the shroud member at a higher temperature corresponding to a typical operational temperature of the compressor when the shroud member has expanded more than the mounting flange and the compressor housing in the radial direction. Preferably, the clearance is adapted so that a slight press fit is achieved at the operation temperature.

In an embodiment the shroud member comprises at least three, preferably more, guide fins distributed along/around and extending radially outwards from an outer circumference of the shroud member, wherein the guide fins are held between the mounting flange and a mating annular flange of the compressor housing. The term outer circumference refers here to the outer circumference of a main central part of the shroud member, i.e. typically the entire shroud member except for the guide fins. This design allows for the use of axially extending screws or bolts for fixing the mounting flange to the compressor housing, preferably between the fins to avoid having to make holes in the guide fins, and to hold the shroud member in place axially via the guide fins.

In an embodiment each circumferential side of each guide fin extends in the radial direction of the shroud member.

In an embodiment the mounting flange comprises a plurality of axially extending protrusions that are arranged to fit circumferentially between the at least three guide fins of the shroud member and to abut the compressor housing between the guide fins of the shroud member in the mounted state of the mounting flange. There is thus a plurality of circumferentially distributed spaces provided for receiving the guide fins between the axially extending protrusions.

In an embodiment the protrusions are arranged to fit tightly between the at least three guide fins so as to provide for a substantial absence of clearance (i.e. so as to provide for a tight fit) between circumferentially mating surfaces of the guide fins and the protrusions, wherein the guide fins and the corresponding protrusions are distributed around the outer circumference of the shroud member so as to, in combination with the absence of circumferential clearance, ensure that the shroud member is centered in the mounting flange. Besides holding the shroud member in place rotationally (i.e. in the circumferential direction), such a design centers the shroud member in relation to the mounting flange and the rotational axis and thus holds the shroud member in place also in the radial direction despite the radial clearances. The reason for this is that the shroud member is not allowed to move in any radial direction since the tight fit of a first guide fin between corresponding protrusions on each side of the guide fin will prevent relative radial motion in any radial direction except for that of the first guide fin, the tight fit of a second guide fin between corresponding protrusions will prevent relative radial motion in any radial direction except for that of the second second guide fin, and so on. This can easily be understood by imagining an example where there are four guide fins evenly distributed along the circumference, one on top, one to the right, one at the bottom and one to the left, with axially extending protrusions tightly fitted between the guide fins. Radial movements of the shroud member in the vertical direction is prevented by the left and right guide fins (that are tightly fit between corresponding protrusions on each side) and radial movements in the horizontal direction is prevented by the top and bottom guide fins (that are tightly fit between corresponding protrusions on each side). So, even if there are radial clearances the shroud member is still centered and held in place in the radial direction. In a preferred example there are eight guide fins evenly distributed along the outer circumference of the shroud member (and eight corresponding axially extending protrusions provided on the mounting flange that fit tightly in the circumferential direction between the guide fins).

In an embodiment a thickness of the guide fins in the axial direction is substantially the same or slightly less than a magnitude of an axial extension of the axially extending protrusions so that, when the guide fins of the shroud member are arranged between the protrusions of the mounting flange and the protrusions abut onto the compressor housing, the guide fins are held in place in the axial direction between the mounting flange and the compressor housing while still being allowed to slide radially outwards as a result of thermal expansion. If the thickness of the guide fins are significantly larger than the axial length of the protrusions the guide fins would be clamped with a significant force between the mounting flange and the compressor housing which would not allow the shroud member to expand radially when the temperature increases. On the other hand, if the thickness of the guide fins are significantly smaller than the axial length of the protrusions the guide fins will not be held in place properly in the axial direction. In an embodiment the axially extending protrusions are provided with an axially extending screw hole adapted to receive a fastening element, such as a screw, for fastening the mounting flange to the compressor housing. The screw holes may be provided with threads to allow insertion of screws/bolts from the compressor housing for fastening in the mounting flange, or the screw holes may be through-holes to allow insertion of scews/bolts from the mounting flange-side for fastening in threads in holes in the housing. Preferably, there are eight protrusions evenly distributed circumferentially along the annular mounting flange, each being provided with a screw hole. This provides for a proper fixing of the mounting flange and the shroud member (via eight corresponding guide fins).

In an embodiment the shroud member is made of a thermoplastic material, e.g. tetraflourethylen or a similar highcrystalline thermoplastic material.

In an embodiment the compressor housing and the mounting flange are made of the same material, preferably aluminium, so that the second and third materials as well as the second and third thermal thermal expansion coefficients are the same.

According to a second aspect of the invention, the object is achieved by an internal combustion engine comprising a compressor device of the above type.

In an embodiment the compressor device is arranged to be driven by an exhaust turbine, an electric motor or a mechanical connection to the internal combustion engine.

In an embodiment the compressor device is arranged to compress air to be fed to the engine. Preferably, this is a turbo charging arrangement where the compressor is driven by exhaust gas flowing through an exhaust turbine.

According to a third aspect of the invention, the object is achieved by a vehicle comprising an internal combustion engine of the above type.

According to a fourth aspect of the invention, the object is achieved by an annular shroud member for use in a compressor device of the above type, wherein the shroud member comprises at least three, preferably more, guide fins distributed along and extending radially outwards from an outer circumference of the shroud member. In an embodiment the shroud member is made from a thermoplastic material, e.g. tetraflourethylen or a similar highcrystalline thermoplastic material.

Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

In the drawings:

Fig. 1 is a schematic drawing showing a truck provided with a compressor device according to the invention;

Fig. 2 shows an end view of a compressor device according to an embodiment of the invention;

Fig. 3A and 3B show sectional views of the compressor device according to figure 2;

Fig. 4 shows a perspective view of a shroud member of the compressor device according to figure 2;

Fig. 5 shows a perspective view of a mounting flange of the compressor device according to figure 2;

Fig. 6 shows a perspective view of the shroud and the mounting flange of figures 4 and 5 fit together; and

Fig. 7 shows an enlarged schematic sectional view of a part of the compressor device according to figure 2 indicating clearances.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

Figure 1 shows a vehicle in the form of a truck 30 provided with an internal combustion engine 1 and a compressor device (not shown in figure 1 ) according to the invention. Figure 2 shows in an end view an embodiment of a compressor device 20 having a compressor housing 2, an axial air inlet 3 and a radial air outlet 4. Figure 2 further shows a rotor 5 with rotor blades and a rotational axis 15 around which the rotor 5 rotates.

Figures 3A and 3B show sectional views A-A and C-C, respectively, of the compressor device of figure 2. As shown in figures 3A and 3B (see also figure 4), an annular shroud member 6 is mounted in the compressor housing 2 around the rotational axis 15 between the blades and an inner wall of the compressor housing 2, and an annular mounting flange 7 is provided for fixing the shroud member 6 in relation to the compressor housing 2 by means of screws/bolts 14 that fix the mounting flange 7 and indirectly the shroud member 6 to the compressor housing 2 via an annular flange thereof. In this example the screws 14 are inserted through holes 12 (see figure 5) in the mounting flange 7 and fastened to threads in the compressor housing 2. In an alternative design, the screws 14 may instead be inserted in the opposite direction through holes in the compressor housing 2 and be fastened to threads in holes in the mounting flange 7.

The mounting flange 7 is radially guided into the compressor housing 2 and radially slightly press fitted to ensure proper centering around the rotational axis 15 before being axially secured by means of the screws 14. The mounting flange 7 is preferably made of a material exhibiting thermal expansion properties identical or close to those of the compressor housing 2 and so that these two parts can expand without creating significant tensions. Both the mounting flange 7 and the compressor housing may be made of aluminium.

Figure 4 shows a perspective view of the shroud member 6, which in this example comprises eight guide fins 8 evenly distributed along, and extending radially outwards from, an outer circumference of the shroud member 6. Each circumferential side 10 of each guide fin 8 extends in this example in the radial direction of the shroud member 6, i.e. each circumferential side extends towards the rotational axis 15 when the shroud member is properly arranged in the compressor housing 2. As will be described below, the guide fins 8 are held between the mounting flange 7 and a mating annular flange of the compressor housing 2 when the compressor device 20 is assembled. Figure 4 also shows a cavity 13 for accommodating a sealing element (not shown) against the inner wall of the compressor housing 2. Figure 5 shows a perspective view of the mounting flange 7, which comprises eight axially extending protrusions 9 that are arranged to fit circumferentially between the eight guide fins 8 of the shroud member 6 and to abut the compressor housing 2 between the guide fins 8 of the shroud member 6 when the compressor device 20 is assembled. The protrusions 9 are arranged to fit tightly between the eight guide fins 8 so as to provide for a substantial absence of clearance, i.e. a tight fit, between circumferentially mating surfaces of the guide fins 8 and the protrusions 9, i.e. the circumferential sides 10 in figure 4 and circumferential sides 11 of the protrusions 9 as indicated in figure 5.

The guide fins 8 and the corresponding protrusions 9 are evenly distributed around the outer circumference of the shroud member 6 so as to, in combination with the lack of circumferential clearance, ensure that the shroud member 6 is centered in the mounting flange 7.

Figure 5 also shows the screw holes 12 for the screws/bolts 14 used for fixing of the mounting flange 7 to the compressor housing 2. Each of the axially extending protrusions 9 is provided with such an axially extending screw hole 12 adapted to receive a screw 14.

Figure 6 shows a perspective view of the shroud member 6 and the mounting flange 7 of figures 4 and 5 when fit together. The shroud member 6 is now rotationally and radially secured in the mounting flange 7 since the tight circumferential fit between the circumferentially mating surfaces 10, 11 prevents relative motion in the circumferential and radial directions (despite a radial clearance, which is described below).

Relative motion between the shroud member 6 and the mounting flange 7 in the axial direction is prevented when these two parts are fixed to the compressor housing 2 by means of the screws 14.

Figure 6 further indicates that a thickness of the guide fins 8 in the axial direction is substantially the same or slightly less than a magnitude of an axial extension of the axially extending protrusions 9. Thus, the combined thickness of the shroud member 6 and the mounting flange 7 along the outer circumference when fit to each other is substantially uniform. This means that, when the guide fins 8 of the shroud member 6 are arranged between the protrusions 9 of the mounting flange 7 and the protrusions 9 abut the compressor housing 2, the guide fins 8 are held in place in the axial direction between the mounting flange 7 and the compressor housing 2 while still being allowed to slide radially outwards as a result of thermal expansion. This can be seen in figures 3A, 3B and 7.

Figure 7 shows an enlarged schematic sectional view of a part of the compressor device according to figure 2 indicating clearances. Figure 7 shows a cross section taken along the rotational axis 15 (as in figures 3A and 3B) through one of the guide fins 8, i.e. somewhere in-between two of the protrusions 9 of the mounting flange 7.

Figure 7 indicates clearances between the shroud member 6 (including one of the guide fins 8) and the compressor housing 2 as well as the mounting flange 7. The clearances C1 , C2 and C3 indicate radial clearances that allow for a larger (thermally induced) radial expansion of the shroud member 6 in relation to the compressor housing 2 and the mounting flange 7. The clearances C1 , C2 and C3 are typically in the magnitude 0.1-0.3 mm.

As described above, the axial clearance C4 between the compressor housing 2 and the shroud member 6 as well as the axial clearance C5 between the shroud member 6 and the mounting flange 7 are zero or close to zero in order to firmly hold the shroud member 6 axially in place but still allow for radial expansion. The clearance C6 is likewise approximately zero as the mounting flange is preferably press fitted into the housing 2.

In the example described above the shroud member 6 is made of Teflon, whereas the mounting flange 7 and the compressor housing 2 are made of aluminium.

Figures 1-7, and in particular figure 7, thus show an example of a compressor device 20, wherein the shroud member 6 is made of a material (Teflon) having a first thermal expansion coefficient and wherein each of the mounting flange 7 and the compressor housing 2 is made of another material (aluminium, in both cases) having a second thermal expansion coefficient that is smaller than the first thermal expansion coefficient. Thus, the shroud member 6 will expand more than the mounting flange 7 and the compressor housing 2 when the temperature of the compressor device 20 increases from room temperature (or lower, or somewhat higher) to an operation temperature of the compressor device 20. Further, the shroud member 6 is arranged in relation to the mounting flange 7 and the compressor housing 2 so that the radial clearance C1 , C2, C3 is provided at room temperature between the shroud member 6 and radially mating surfaces of the mounting flange 7 and the compressor housing 2, i.e. the surfaces of the mounting flange 7 and the compressor housing 2 that radially inwards face the radial clearances C1 , C2, C3.

The magnitude of the radial clearances C1 , C2, C3, i.e. the width of the radial gap, is preferably adapted to be closed by the shroud member 6 at the operation temperature of the compressor device 20 to achieve a slight press fit during operation.

It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.

Claims

1. A compressor device (20) for a turbo-charging arrangement of an internal combustion engine (1 ), the compressor device (20) comprising:

- a compressor housing (2);

- a compressor rotor (5) with blades arranged inside the compressor housing (2), wherein the compressor rotor (5) is arranged to rotate around a rotational axis (15); and

- an annular shroud member (6) mounted in the compressor housing (2) around the rotational axis (15) between the blades and the compressor housing (5), characterized in that an annular mounting flange (7) is provided for mounting the shroud member (6) to the compressor housing (2), wherein the shroud member (6) is made of a first material having a first thermal expansion coefficient, wherein the mounting flange (7) is made of a second material having a second thermal expansion coefficient, and wherein the compressor housing (2) is made of a third material having a third thermal expansion coefficient, wherein each of the second and third thermal expansion coefficients is smaller than the first thermal expansion coefficient, wherein the shroud member (6) is arranged in relation to the mounting flange (7) and the compressor housing (2) so that a radial clearance (C1 , C2, C3) is provided at room temperature between the shroud member (6) and radially mating surfaces of the mounting flange (7) and the compressor housing (2).

2. A compressor device (20) according to claim 1 , wherein the magnitude of the radial clearance (C1 , C2, C3) is adapted to be closed by the shroud member (6) at a higher temperature corresponding to a typical operational temperature of the compressor when the shroud member (6) has expanded more than the mounting flange (7) and the compressor housing (2) in the radial direction.

3. A compressor device (20) according to anyone of the above claims, wherein the shroud member (6) comprises at least three, preferably more, guide fins (8) distributed along and extending radially outwards from an outer circumference of the shroud member (6), wherein the guide fins (8) are held between the mounting flange (7) and a mating annular flange of the compressor housing (2).

4. A compressor device (20) according to claim 3, wherein each circumferential side (10) of each guide fin (8) extends in the radial direction of the shroud member (6).

5. A compressor device (20) according to claim 3 or 4, wherein the mounting flange (7) comprises a plurality of axially extending protrusions (9) that are arranged to fit circumferentially between the at least three guide fins (8) of the shroud member (6) and to abut the compressor housing (2) between the guide fins (8) of the shroud member (6) in the mounted state of the mounting flange (7).

6. A compressor device (20) according to claim 5, wherein the protrusions (9) are arranged to fit tightly between the at least three guide fins (8) so as to provide for a substantial absence of clearance between circumferentially mating surfaces (10, 1 1 ) of the guide fins (8) and the protrusions (9), wherein the guide fins (8) and the corresponding protrusions (9) are distributed around the outer circumference of the shroud member (6) so as to, in combination with the absence of circumferential clearance, ensure that the shroud member (6) is centered in the mounting flange (7).

7. A compressor device (20) according to claim 5 or 6, wherein a thickness of the guide fins (8) in the axial direction is substantially the same or slightly less than a magnitude of an axial extension of the axially extending protrusions (9) so that, when the guide fins (8) of the shroud member (6) are arranged between the protrusions (9) of the mounting flange (7) and the protrusions (9) abut the compressor housing (2), the guide fins (8) are held in place in the axial direction between the mounting flange (7) and the compressor housing (2) while still being allowed to slide radially outwards as a result of thermal expansion.

8. A compressor device (20) according to any one of claims 5-7, wherein the axially extending protrusions (9) are provided with an axially extending screw hole (12) adapted to receive a fastening element, such as a screw (14), for fastening the mounting flange (7) to the compressor housing (2).

9. A compressor device (20) according to any one of the preceding claims, wherein the shroud member (6) is made of a thermoplastic material, e.g. tetraflourethylen or a similar highcrystalline thermoplastic material.

10. A compressor device (20) according to any one of the preceding claims, wherein the compressor housing (2) and the mounting flange (7) are made of the same material, preferably aluminium, so that the second and third materials as well as the second and third thermal thermal expansion coefficients are the same.

1 1. An internal combustion engine (1 ), characterized in that it comprises a compressor device (20) according to any one of the preceding claims.

12. An internal combustion engine (1 ) according to claim 1 1 , wherein the compressor device (20) is arranged to be driven by an exhaust turbine, an electric motor or a mechanical connection to the internal combustion engine (1 ).

13. An internal combustion engine (1 ) according to claim 11 or 12, wherein the compressor device (20) is arranged to compress air to be fed to the engine (1 ).

14. A vehicle (30) characterized in that it comprises an internal combustion engine (1 ) according to anyone of claims 11-13.

15. An annular shroud member (6) for use in a compressor device (20) according to any one of claims 1 -10, characterized in that the shroud member (6) comprises at least three, preferably more, guide fins (8) distributed along and extending radially outwards from an outer circumference of the shroud member (6).

16. An annular shroud member (6) according to claim 15, wherein the shroud member (6) is made from a thermoplastic material, e.g. tetraflourethylen or a similar highcrystalline thermoplastic material.