COMPRESSOR ARRANGEMENT SUPPLYING CHARGED AIR TO A COMBUSTION ENGINE

Abstract

Provided is a compressor arrangement in an air line supplying charged air to a combustion engine. The compressor arrangement comprises a compressor unit comprising a housing including an air intake passage, a compressor wheel arranged in said air intake passage, and an additional air passage allowing recirculation of air from the air intake passage in a position radially outwardly of a part of the compressor wheel. The additional air passage is configured to allow recirculation of air to an air conduit delivering an air flow to the air intake passage of the compressor unit.

Claims

1. A compressor arrangement in an air line supplying charged air to a combustion engine, wherein the compressor arrangement comprises: a compressor unit comprising a housing including an air intake passage; a compressor wheel arranged in said air intake passage; and an additional air passage allowing recirculation of air from the air intake passage in a position radially outwardly of a part of the compressor wheel to an air conduit delivering an air flow to the air intake passage of the compressor unit in a position located at a flow distance from the compressor wheel corresponding to at least 1 to 5 times the inlet diameter of the compressor wheel, wherein the additional air passage comprises a return conduit having an extension between a downstream end connected to an opening in the housing and an upstream end connected to an opening in the air conduit and that the air conduit has a curved portion close to the intake passage of the compressor unit, wherein the return conduit is configured to return air to an upstream position of said curved portion of the air conduit.

2. A compressor arrangement according to claim 1, wherein the additional air passage is configured to return air to the air conduit in a position located at a flow distance from the compressor wheel within the range of 2 to 5 times the inlet diameter of the compressor wheel.

3. A compressor arrangement according to claim 1, wherein a part of the additional air passage is defined by an annular air gap extending around the compressor wheel in the air intake passage.

4. A compressor arrangement according to claim 3, wherein the additional air passage is defined by an annular space receiving air from the annular air gap.

5. A compressor arrangement according to claim 4, wherein the housing comprises a tubular portion defining a wall between the air intake passage and the annular space.

6. A compressor arrangement according to claim 5, wherein the the tubular portion is made in one piece with the housing.

7. A compressor arrangement according to claim 5, wherein the tubular portion comprises an upstream located end portion forming a closed wall section between the air intake passage and the annular space.

8. A compressor arrangement according to claim 7, wherein the tubular portion comprises a downstream located end portion defining a side surface of the air gap.

9. A compressor arrangement according to claim 1, wherein the housing comprises a inlet portion defining at least a first part of the air intake passage, wherein the inlet portion comprises a connection surface be connected to an end portion of the air conduit.

10. A compressor arrangement according to claim 1, wherein the housing comprises a hollow portion configured to receive a shaft providing a connection between the compressor wheel and a turbine wheel.

11. A compressor arrangement according to claim 1, wherein the additional air passage comprises flow restricting means.

12. A turbo charger comprising a compressor arrangement in an air line supplying charged air to a combustion engine, wherein the compressor arrangement comprises: a compressor unit comprising a housing including an air intake passage; a compressor wheel arranged in said air intake passage; and an additional air passage allowing recirculation of air from the air intake passage in a position radially outwardly of a part of the compressor wheel to an air conduit delivering an air flow to the air intake passage of the compressor unit in a position located at a flow distance from the compressor wheel corresponding to at least 1 to 5 times the inlet diameter of the compressor wheel, wherein the additional air passage comprises a return conduit having an extension between a downstream end connected to an opening in the housing and an upstream end connected to an opening in the air conduit and that the air conduit has a curved portion close to the intake passage of the compressor unit, wherein the return conduit is configured to return air to an upstream position of said curved portion of the air conduit.

13. (canceled)

14. A turbo charger according to claim 12, wherein the additional air passage is configured to return air to the air conduit in a position located at a flow distance from the compressor wheel within the range of 2 to 5 times the inlet diameter of the compressor wheel.

15. A turbo charger according to claim 12, wherein a part of the additional air passage is defined by an annular air gap extending around the compressor wheel in the air intake passage.

16. A turbo charger according to claim 15, wherein the additional air passage is defined by an annular space receiving air from the annular air gap.

17. A vehicle comprising a turbo charger having a compressor arrangement in an air line supplying charged air to a combustion engine, wherein the compressor arrangement comprises: a compressor unit comprising a housing including an air intake passage; a compressor wheel arranged in said air intake passage; and an additional air passage allowing recirculation of air from the air intake passage in a position radially outwardly of a part of the compressor wheel to an air conduit delivering an air flow to the air intake passage of the compressor unit in a position located at a flow distance from the compressor wheel corresponding to at least 1 to 5 times the inlet diameter of the compressor wheel, wherein the additional air passage comprises a return conduit having an extension between a downstream end connected to an opening in the housing and an upstream end connected to an opening in the air conduit and that the air conduit has a curved portion close to the intake passage of the compressor unit, wherein the return conduit is configured to return air to an upstream position of said curved portion of the air conduit.

18. A vehicle according to claim 17, wherein the additional air passage of the compressor arrangement is configured to return air to the air conduit in a position located at a flow distance from the compressor wheel within the range of 2 to 5 times the inlet diameter of the compressor wheel.

19. A vehicle according to claim 17, wherein a part of the additional air passage of the compressor arrangement is defined by an annular air gap extending around the compressor wheel in the air intake passage.

20. A vehicle according to claim 19, wherein the additional air passage is defined by an annular space receiving air from the annular air gap.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In the following a preferred embodiments of the invention is described, as an example, with reference to the attached drawings, in which:

[0016] FIG. 1 shows a turbo charger including a compressor arrangement according to the present invention,

[0017] FIG. 2 shows the compressor arrangement in FIG. 1 more in detail and

[0018] FIG. 3 shows a second embodiment of the compressor arrangement.

DETAILED DESCRIPTION OF THE INVENTION

[0019] FIG. 1 shows a compressor for a combustion engine 2 powering a schematically indicated vehicle 1. The vehicle 1 may be a heavy vehicle and the combustion engine 2 may be an internal combustion engine such as a diesel engine. The exhaust gases from the cylinders of the combustion engine 2 are led via an exhaust manifold 3 to an exhaust line 4. The combustion engine 2 is provided with a turbo charger 5 comprising a turbine wheel 6 and a compressor wheel 7. The exhaust gases are initially led, via the exhaust line 4, to the turbine wheel 6. The pressure of the exhaust gases provide a driving power of the turbine wheel 6 which is transmitted, via a shaft 8, to the compressor wheel 7. As a consequence, the exhaust gases leaving the turbine wheel 6 have a reduced pressure. The compressor wheel 7 is arranged in a charge air line 9 directing charge air to the combustion engine 2. During operation of the compressor wheel 7, air is drawn from the surrounding, via a first air line 9a of the charge air line 9, to the compressor wheel 7. The air leaves the compressor wheel 7 with an increased pressure and an increased temperature. The charge air line 9 comprises a second air line 9b directing the charge air from the compressor 7 to at least one charge air cooler 10. In this case, the charged air cooler is exemplified as an air cooled charge air cooler 10 arranged in a front position of the vehicle together with a radiator 11. The charge air is cooled in the charge air cooler 10 by air of ambient temperature which is forced through the charged air cooler 10 and the radiator 11 by a radiator fan 12 and the ram air of the vehicle 1. The cooled charged air is directed from the charged air cooler 10, via a third air line 9c of the charge air line 9 and an inlet manifold 13, to the cylinders of the combustion engine 2.

[0020] The turbo charger 5 comprises a compressor unit 14 which is shown in FIG. 2. The compressor unit 14 comprises a housing 15 enclosing the compressor wheel 7. The housing 15 comprises further an inlet portion 16 receiving air from the first air line 9a. The inlet portion 16 forming a first part of an air intake passage 17 directing air to the compressor wheel 7. The inlet portion 16 comprises a connecting surface 16a configured to receive an end of the first air line 9a. Furthermore, the housing 15 comprises an outlet volute 18 delivering charged air to the second air line 9b. The compressor unit 14 comprises a tubular portion 19 having a radially inner surface 20 defining a second part of the air intake passage 17 directing air the compressor wheel 7. The tubular portion 19 has in an upstream position a closed wall section 21 fixedly connected to the inlet portion 16 and in a downstream position a free end portion 22 located at an axial distance from a radial surface 23 of the housing 15.

[0021] The distance between the free end portion 22 of the tubular portion 19 and the radial surface 23 of the housing 15 forms an annular axial gap 24. The annular axial gap 24 is located in a radially outer position of a part compressor wheel 7. The housing 15 has a curved inner surface 25 defining a third part of the air intake passage 17. The annular axial gap 24 is connected to an annular space 26 defined by a surface of the housing 15 and a radially outer surface 27 of the tubular portion 19. The housing 15 comprises at least one radial opening 28 to the annular space 26. The radial opening 28 is configured to receive a first end 29a of a return conduit 29. A second end 29b of the return conduit 29 is arranged in an opening 30 in the first air line 9a. The second end 29b of the return conduit 29 is located in an upstream position in relation to the inlet portion 16 of the housing 15 and the compressor wheel 7. In this case, the first air line 9a comprises a curved portion 9a.sub.1 in the vicinity of the compressor unit 14. The second end 29b of the return conduit 29 is connected to an opening 30 in the first air line 9a located upstream of the curved portion 9a.sub.1 of the first air line 9a. The housing 15 comprises a hollow portion 31 configured to receive the shaft 8 connecting the compressor wheel 7 and the turbine wheel 6.

[0022] During operation of the compression engine 2, the exhaust gases in the exhaust line 4 drives the turbine wheel 6. The turbine wheel 6 in turn drives, via the shaft 8, the compressor wheel 7. The compressor wheel 7 drawn air from the surrounding, via the first air line 9a, to the compressor unit 14. During operating conditions when the compressor wheel 7 works close to choke with a high speed and supplies a large quantity of charge air to the combustion engine 2, the static pressure in the air intake passage in a position radially inside the air gap 24 will be lower than the static pressure in the inlet line 9a at the opening 30. In this case, an air flow is entering the opening 30, via the return conduit 29, the radial opening 28, the annular space 26 and the air gap 24, to the flow passage. Thus, during such operating conditions, the return conduit 29 provides an additional air flow to the compressor wheel 7.

[0023] During operating conditions when the compressor wheel 7 runs close to surge and provides a low air flow at a relatively high pressure through the air intake passage 17, the static pressure in a position radially inside the air gap 24 increases to a higher value than the static pressure in the first air line 9a at the opening 30. In this case, a part of the air flow in the air intake passage 17 is led into the air gap 24, whereupon it is directed, via the annular space 26, the radial opening 28 and the return conduit 29, to the opening 30. Consequently, a part of the air flow entering the inlet portion 16 is recirculated to the first air line 9a at a distance from the compressor unit 14. This recirculating part of the air flow is mixed with the ordinary air flow in the first air line 9a and again directed to the compressor unit 14. The opening 30 in the first air line 9a is arranged in a first transverse plane A.sub.1 through first air line 9a. The compression of the air starts in the air intake passage 17 in a second transverse plane A.sub.2 extending through a front surface of the compression wheel 7.

[0024] The average flow distance D of the air along a center axis in the first air line 9a from the first plane A.sub.1 to the second plane A.sub.2 is indicated in FIG. 2. It is important to supply a relatively uniform air flow to the compressor wheel 7 in order to provide a stable operation of the compressor. A relatively uniform supply of air to the compressor wheel 7 may provide a large stable operating region in a compressor map plotting mass flow as a function of pressure ratio. The supply of the air flow from the returning line 29 to the first air line 9a disturbs the relatively uniform air flow in the first plane A.sub.1. However, after a certain flow distance from the first plane A.sub.1, the air flow will again become relatively uniform. The flow distance D between the first plane A.sub.1 and the second plane A.sub.2 is chosen such the air flow has become sufficiently uniform when it reaches the compressor wheel 7. The value of the distance D depends on a number of factors such as the dimension of the first air line 9a, the air flow rate in the first air line 9a, the air flow rate in the air intake passage 17, the air flow rate in the return conduit 29 etc. The distance D is at least 1-5 times the inlet diameter d to the compressor wheel 7 but preferably longer and within the range of 2-5 times the inlet diameter d to the compressor wheel 7.

[0025] FIG. 3 shows a second embodiment of the invention. In this case, the return conduit 29 has been equipped with a throttle valve 31. Furthermore, the air gap 24 has been increased. As a consequent, the air flow through the return conduit 29 is mainly restricted by the throttle valve 31. The throttle valve 31 may have an adjustable throttle area. In this case, the throttle vale 31 is controlled by a control unit 32. The control unit 32 receives information about suitable operating parameters and controls the throttle valve 31 by means of this information. In this case, it is possible to adjust the air flow through the return conduit 29 during different operating conditions in order to optimize the operating properties of the compressor wheel 7 in a large operating region. Alternatively, the throttle valve have a constant throttle area. In this case, the throttle area is dimensioned to allow an air flow through the return conduit 29 such that it allows substantially optimal operating properties of the compressor wheel 7 in a large operating region.

[0026] The invention is in no way limited to the embodiments described with reference to the drawings but may be varied freely within the scopes of the claims. It is, for example, possible to use more than one return conduit 29.