HK1200516B - Two-stage supercharging device - Google Patents

Description

Two-stage supercharging device

Technical Field

The invention relates to a two-stage supercharging device for an internal combustion engine having a high-pressure turbine and a low-pressure turbine, according to the preamble of claim 1.

Background

Modern internal combustion engines are usually equipped with a two-stage supercharging device. The first stage of the supercharging device is a high-pressure stage, and the second stage is a low-pressure stage. Here, the high-pressure stage includes a high-pressure turbine and a high-pressure compressor. The low pressure stage includes a low pressure turbine and a low pressure compressor. The high-pressure stage and the low-pressure stage of the charging device are each equipped with a rotor wheel, which comprises a high-pressure turbine rotor or a low-pressure turbine rotor, a respective shaft and a high-pressure compressor rotor or a low-pressure compressor rotor. In operation, an exhaust gas flow flows from the internal combustion engine through the exhaust gas line into the high-pressure turbine and subsequently through the exhaust gas duct into the low-pressure turbine. In the high load range of the internal combustion engine, the exhaust gas flow is so high that the running wheels of the high-pressure stage rotate at such a high speed that they can be damaged by the centrifugal forces occurring. To prevent this, the exhaust gas flow is split into a main exhaust gas flow and a sub exhaust gas flow at a branching point in the exhaust line. The main exhaust gas flow flows into the high-pressure turbine, and the sub-exhaust gas flow flows around the high-pressure turbine in the bypass device. The bypass device comprises in the simplest case a branch line branching off from the exhaust line at a branching point and a shut-off valve arranged therein. In the high-load range, therefore, the partial exhaust gas flow is branched off from the exhaust gas flow upstream of the high-pressure turbine in the branch line, regulated with the shutoff valve and conducted into the exhaust gas duct downstream of the high-pressure turbine. The main exhaust gas flow into the high-pressure turbine therefore falls and, as a result, the running wheels of the high-pressure stage are not damaged thereby. The partial exhaust gas flow flowing around the high-pressure turbine in the bypass device is combined in the exhaust gas duct with the main exhaust gas flow flowing out of the high-pressure turbine in order to continue flowing into the low-pressure turbine. The bypass device with its structural connection to the exhaust gas channel is the main point of the invention and will be explained further below.

Examples of different embodiments of structural connections are known from the prior art. Thus, DE 102007046667 a1 shows an annular channel surrounding the exhaust channel as a connection. According to the illustration, the sub-exhaust flows flow into the annular channel, are evenly dispersed in the annular channel, and then flow radially into the exhaust channel. The problem of inflow conditions from one fluid into another has been discussed basically in this description, but has not been optimally achieved. A disadvantage of this publication is that strong vortices occur at the edge of the annular channel when the sub-exhaust gas flows radially into the exhaust channel. This is associated with a high pressure loss and requires a long exhaust gas duct for the combined exhaust gas flow to settle in order to flow uniformly into the low-pressure turbine arranged downstream. Pressure losses represent a high efficiency loss for the low-pressure turbine. The annular duct and the long exhaust duct arranged downstream of the high-pressure turbine result in a large installation space requirement. The efficiency losses and the large installation space requirements are disadvantageous for internal combustion engines.

Another prior art is known from document EP 1710415 a 1. The bypass device here comprises a branch line, a shut-off valve, a coupling flange and an annular channel. In this case, the partial exhaust gas flow is split off in a branch line upstream of the high-pressure turbine. For regulating the partial exhaust gas flow, a shut-off valve is arranged in the branch line. The partial exhaust gas flows open via the coupling flange into an annular channel which is arranged helically around the exhaust gas channel. In this case, separate flow guidance of the main exhaust gas flow and the partial exhaust gas flow is present up to immediately before the low-pressure turbine rotor. The disadvantage here is that the main exhaust gas flow and the partial exhaust gas flow cannot be combined before the low-pressure turbine. This results in a radially uneven inflow of the low-pressure turbine rotor. The combination of the swirling flow of the sub-exhaust flow due to the helical shape of the annular channel thus results in a poorer efficiency of the low-pressure turbine. A further disadvantage is the considerable installation space and component requirements of the bypass device for the line guidance and the shut-off valves of the branch lines and for the annular channel together with the separate coupling flange.

Disclosure of Invention

The object of the invention is to improve the flow guidance of the partial exhaust gas flow from the annular channel into the exhaust gas channel and to arrange the bypass device together with the annular channel in a manner that optimizes the installation space and the components.

The solution is achieved with a two-stage supercharging device with the features of claim 1. Advantageous embodiments of the invention are indicated in the dependent claims.

According to the invention, a two-stage charging device for an internal combustion engine is provided, comprising a high-pressure turbine and a low-pressure turbine, wherein the high-pressure turbine is designed as a radial turbine with a spiral housing and the low-pressure turbine is designed as an axial turbine, wherein the spiral housing has an exhaust gas inlet connection connected to an exhaust gas line, through which an exhaust gas flow flows from the internal combustion engine to the high-pressure turbine, wherein the high-pressure turbine and the low-pressure turbine are arranged face to face on an axis and an exhaust gas outlet of the high-pressure turbine is connected in terms of flow to an exhaust gas inlet of the low-pressure turbine via an exhaust gas duct, wherein a partial exhaust gas flow of the exhaust gas flow can be guided around the high-pressure turbine in a bypass device, wherein the bypass device comprises a branch line and an annular duct housing, wherein the annular duct housing forms an annular duct and the branch line opens into the, wherein the partial exhaust gas flow is branched off in part from the exhaust gas flow upstream of the high-pressure turbine rotor of the high-pressure turbine, and an annular channel is arranged around and connected with the exhaust gas channel downstream of the high-pressure turbine, so that the main exhaust gas flow leaving the high-pressure turbine is combined with the partial exhaust gas flow of a bypass device in the exhaust gas channel in order to continue flowing into the low-pressure turbine, wherein a shut-off valve is arranged in the bypass device. The spiral housing of the high-pressure turbine is designed in one piece with the annular channel housing.

The advantage is that only one component is produced cost-effectively and therefore also an advantageous assembly takes place without a large number of complicated assembly steps. In addition, the one-piece design (for example as a casting) makes it possible to achieve a short and space-saving design, which is manifested in that the channel shape of the spiral channel and the annular channel formed by the spiral housing is selected such that the largest cross section of the spiral channel and the annular channel is located on one side. The channel shape is novel in terms of casting technology and, with a flow-technically optimized transition, generally ensures a significantly better flow guidance of the partial exhaust gas flow than before. As a result of the embodiment of the casting technique, a better flow guidance of the partial exhaust gas flow from the annular channel into the exhaust gas channel is also obtained.

According to a preferred embodiment of the invention, the spiral housing and the annular channel housing are connected at the end face (stinnestig) by a common wall region.

According to a further preferred embodiment of the invention, the spiral housing of the high-pressure turbine is formed in one piece with the branch line.

According to a further preferred embodiment of the invention, the branch line branches off from the exhaust gas inlet connection of the spiral housing and is formed in one piece with the spiral housing.

The advantage of the embodiment of the one-piece housing is that the components described therein are present in the housing and the housing can be produced, for example, as a compact casting. This reduces the number of components and, as a result, also the costly processing of the components during production. The housing is shorter and more compact and therefore requires little installation space at the internal combustion engine.

According to a further preferred embodiment of the invention, the annular channel has its largest cross section in the inflow region of the branch line, and the cross section decreases starting from the inflow region in both circumferential directions of the annular channel up to a point at the annular channel which lies opposite the inflow region of the branch line.

In this case, it is advantageous if the partial exhaust gas flows flowing into the annular channel are distributed uniformly over the annular channel and therefore flow into the exhaust gas channel likewise uniformly and without swirl and are combined with the main exhaust gas flow. This also uniformly loads the exhaust gas on the low-pressure turbine, which increases its efficiency.

According to a further preferred embodiment of the invention, the shut-off valve is arranged in the branch line.

The advantage here is that a compact arrangement of the components and a reduction in components are thereby achieved. Furthermore, the arrangement of the shut-off valve in the vicinity of the high-pressure turbine or in the bypass device enables a rapid and delay-free reaction of the high-pressure turbine to the adjustment at the shut-off valve.

According to a further preferred embodiment of the invention, the shut-off valve is designed with a flap, and the flap is arranged in the wall of the exhaust gas inlet connection in the region of the branching point of the branch line and forms, in the closed state, a wall for the exhaust gas flow that approximately follows the wall contour of the exhaust gas inlet connection.

The advantage here is that the exhaust gas flow can flow into the high-pressure turbine with an approximately undisturbed flow contour in the closed state of the flap, which is necessary for good efficiency.

According to a further preferred embodiment of the invention, the flow-guiding surface for the main exhaust gas flow leaving the high-pressure turbine is integrated into the component forming the annular channel and the spiral housing.

The advantage here is that the functions of the housing and of the flow guide surfaces thus coexist in one component and form a compact and space-saving arrangement.

According to a further preferred embodiment of the invention, the annular duct is designed as an annular duct with an annular gap which opens in the direction of the low-pressure turbine and via which the annular duct is connected in terms of flow technology to the exhaust duct.

In this case, it is advantageous that the partial exhaust gas flow flows uniformly and without pressure loss through the annular channel in the direction of the low-pressure turbine and thus increases the efficiency of the low-pressure turbine.

According to a further preferred embodiment of the invention, the outer diameter of the annular gap and the nominal diameter of the exhaust duct are as large as the outer diameter of the low-pressure turbine rotor of the low-pressure turbine.

The advantage here is that the partial exhaust gas flows out of the annular gap without noticeable pressure loss points flow to the low-pressure turbine and are combined with the main exhaust gas flow here. As a result, the low-pressure turbine is subjected to a relatively high pressure, which results in a high efficiency.

According to a further preferred embodiment of the invention, the radially outer wall of the annular channel housing ends at a coupling flange (auslaufen) for coupling to a compensator at the axial turbine.

In this case, it is advantageous if the coupling flange is cast, for example, on the annular channel housing. Thereby, a direct coupling of the compensator, or a coupling of other components, can be achieved without additional coupling components.

Drawings

Embodiments of the invention are illustrated in the drawings and are described further below. Wherein:

fig. 1 shows a section of a longitudinal section of a two-stage supercharging assembly with a high-pressure turbine and a low-pressure turbine;

fig. 2 shows a section along section line a-a through the exhaust gas outlet, the annular channel and at the beginning through the spiral channel and through the exhaust gas inlet connection, the branch line and the flap arranged in the branch location;

FIG. 3 shows a section along section line A-A as in FIG. 2, wherein the shutter is open;

fig. 4 shows a section through the annular gap along section line B-B.

Detailed Description

Fig. 1 shows a section of a longitudinal section of a two-stage charging device 1 with a high-pressure turbine 2 and a low-pressure turbine 4. The high-pressure turbine 2 is embodied here as a radial turbine with a spiral channel 7 formed by a spiral housing 6, and the low-pressure turbine 4 is embodied as an axial turbine. The two turbines are arranged face to face on the axis 8. The bypass device 13, which is molded to the screw housing 6 and comprises a branch line 15 and an annular channel housing 17, can be partially seen. Additionally, an exhaust gas inlet connection 9 is molded on the screw housing 6, from which a branch line 15 branches off in a branching point 14. An exhaust line 10 is connected to the exhaust inlet connection 9. In the low load range up to the medium load range of the internal combustion engine (not shown), the exhaust gas flows from the internal combustion engine through the exhaust gas line 10, the exhaust gas inlet connection 9 and the spiral channel 7 to the high-pressure turbine rotor 3. In the low-load range up to the mid-load range, the exhaust gas flow is simultaneously the main exhaust gas flow, which drives the high-pressure turbine rotor 3 and leaves the high-pressure turbine 2 via the exhaust gas outlet 11 along the flow guide surface 12. The main exhaust gas flow passes through the exhaust gas duct 20 and flows along a guide body 26 arranged in the exhaust gas duct 20 further to an exhaust gas inlet 25 of the low-pressure turbine 4 in order to drive the low-pressure turbine rotor 5 there. In the high load range of the internal combustion engine, the exhaust gas flow is sometimes so high that the high-pressure turbine 3 rotates at too high a speed and can therefore be damaged. To prevent this, the exhaust gas flow is split into a main exhaust gas flow and a partial exhaust gas flow at the branching point 14. The main exhaust gas flow flows into the high-pressure turbine 2 and the sub-exhaust gas flow flows around the high-pressure turbine 2 in the bypass device 13. For regulating the partial exhaust gas flow, a shut-off valve 22 is arranged in the branch line 15 and in the branching point 14 of the exhaust gas inlet connection 9. The shut-off valve 22 is embodied as a flap 23 and is shown in this view in perspective and not completely. The shutter 23 is opened by a driving portion (not shown) in a high load range. The partial exhaust gas flow thus flows via the branch line 15 in the inflow region 16 into the annular channel 18, which annular channel 18 is formed by the annular channel housing 17. An annular channel housing 17 is molded to the spiral housing 6. The sub-exhaust flows are dispersed in the annular channel 18 and flow evenly into the exhaust channel 20 through the annular gap 19 in the annular channel 18. The sub-exhaust-gas flows are combined with the main exhaust-gas flow in the exhaust duct 20 and both flow along the guide body 26 into the exhaust-gas inlet 25 of the low-pressure turbine 4. The radially outer wall of the annular channel housing 17 terminates in a coupling flange 24, to which coupling flange 24 a compensator 21 forming the exhaust channel 20 is coupled. The compensator 21 is generally used to connect the high-pressure turbine 2 to the low-pressure turbine 4 in the two-stage charging device 1 shown here.

Fig. 2 shows a section along section line a-a through the exhaust gas outlet 11, the annular channel 18 and at the beginning through the spiral channel 7 and through the exhaust gas inlet connection 9, the branch line 15 and the flap 23 arranged in the branch point 14. The flap 23 closes the branch line 15 in this position. The flap 23 thus forms approximately a wall for the exhaust gas flow, which follows the wall contour of the exhaust gas inlet connection 9 into the spiral channel 7. The exhaust gas flow from the internal combustion engine (not shown) flows completely as a main exhaust gas flow into the spiral channel 7, through the high-pressure turbine 3 and through the exhaust gas outlet 11 into the exhaust gas channel 20, which is not shown in this illustration.

Fig. 3 shows a section along section line a-a as in fig. 2, however, with the shutter 23 open. Thereby, the exhaust flow is divided into a main exhaust flow and a sub exhaust flow. The main exhaust gas flow flows into the spiral channel 7. The partial exhaust gas flows through the branch line 15 into the annular channel 18 in the inflow region 16. The sub-exhaust gas flows are evenly spread in the annular channel 18 in both circumferential directions and flow through an annular gap 19 (not shown, see fig. 4) into an exhaust channel 20, not shown in this view.

Fig. 4 shows a section through the annular gap 19 along section line B-B. The guide body 26 is hidden from view. The annular gap 19 has a constant width and is located concentrically with the axis 8. The partial exhaust gas flows axially through the annular gap 19 into an exhaust gas duct 20, which is not shown in this illustration.

List of reference numerals

1 two-stage supercharging device

2 high-pressure turbine

3 high-pressure turbine rotor

4 low pressure turbine

5 Low pressure turbine rotor

6 spiral shell

7 helical channel

8 axes of rotation

9 exhaust gas inlet joint

10 exhaust pipeline

11 exhaust gas separation part

12 flow guide surface

13 bypass device

14 branch site

15 branch pipeline

16 inflow region

17 annular channel housing

18 annular channel

19 annular gap

20 exhaust passage

21 compensator

22 stop valve

23 valve

24 coupling flange

25 exhaust gas inlet part

The body is guided 26.

Claims (10)

1. A two-stage supercharging device (1) for an internal combustion engine, comprising a high-pressure turbine (2) and a low-pressure turbine (4),

wherein the high-pressure turbine (2) is configured as a radial turbine with a spiral housing (6) and the low-pressure turbine (4) is configured as an axial turbine,

wherein the screw housing (6) has an exhaust gas inlet connection (9) which is connected to an exhaust gas line (10) through which an exhaust gas flow flows from the internal combustion engine to the high-pressure turbine (2),

wherein the high-pressure turbine (2) and the low-pressure turbine (4) are arranged face-to-face on an axis (8), and an exhaust outlet (11) of the high-pressure turbine (2) is fluidically connected to an exhaust inlet (25) of the low-pressure turbine (4) via an exhaust channel (20),

wherein a sub-exhaust-gas flow of the exhaust-gas flow can be guided around the high-pressure turbine (2) in a bypass device (13),

wherein the bypass device (13) comprises a branch line (15) and an annular channel housing (17),

wherein the annular channel housing (17) forms an annular channel (18) and the branch line (15) opens into the annular channel (18),

wherein the sub-exhaust-gas flow is branched off in part from the exhaust-gas flow upstream of a high-pressure turbine rotor (3) of the high-pressure turbine (2), and the annular channel (18) is arranged around and fluidly connected with the exhaust channel (20) downstream of the high-pressure turbine (2), so that the main exhaust-gas flow leaving the high-pressure turbine (2) combines with the sub-exhaust-gas flow of the bypass device (13) in the exhaust channel (20) for continuing flow into the low-pressure turbine (4),

wherein a shut-off valve (22) is arranged in the bypass device (13),

characterized in that the spiral housing (6) of the high-pressure turbine (2) is constructed in one piece with the annular channel housing (17), wherein the radially outer wall of the annular channel housing (17) ends at a coupling flange (24) for a compensator (21) which is coupled to the axial turbine.

2. Supercharging device according to claim 1, characterized in that the spiral housing (6) and the annular channel housing (17) are connected at the end sides by a common wall region.

3. Supercharging device according to claim 1 or 2, characterized in that the spiral housing (6) of the high-pressure turbine (2) is constructed in one piece with the branch line (15).

4. Supercharging device according to claim 3, characterized in that the branch line (15) branches off from the exhaust gas inlet connection (9) of the spiral housing (6) and is constructed in one piece with the spiral housing (6).

5. Supercharging device according to claim 1 or 2, characterized in that the annular channel (18) has its largest cross section in the inflow region (16) of the branch line (15) and this cross section decreases starting from the inflow region (16) in both circumferential directions of the annular channel (18) up to a point at the annular channel (18) which lies opposite the inflow region (16) of the branch line (15).

6. Supercharging device according to claim 4, characterized in that the shut-off valve (22) is arranged in the branch line (15).

7. Supercharging device according to claim 6, characterized in that the shut-off valve (22) is configured with a flap (23) and the flap (23) is arranged in the wall of the exhaust gas inlet fitting (9) in the region of the branching point (14) of the branch line (15) and, in the closed state, forms a wall for the exhaust gas flow which approximately follows the wall contour of the exhaust gas inlet fitting (9).

8. Supercharging device according to claim 1 or 2, characterized in that a flow guide surface (12) for the main exhaust gas flow leaving the high-pressure turbine (2) is integrated into the component forming the annular channel (18) and the spiral housing (6).

9. Supercharging device according to claim 1 or 2, characterized in that the annular channel (18) is configured with an annular gap (19) which opens in the direction of the low-pressure turbine (4), and the annular channel (18) is fluidically connected to the exhaust channel (20) via the annular gap (19).

10. Supercharging device according to claim 9, characterized in that the outer diameter of the annular gap (19) and the inner diameter of the exhaust channel (20) are as large as the outer diameter of the low-pressure turbine rotor (5) of the low-pressure turbine (4).