EP1222399B1 - Method and device for cooling the flow in the radial gaps formed between rotors and stators of turbine-type machines - Google Patents

Description

Technical field

The invention relates to a method and a device for cooling the flow in radial gaps formed between rotors and stators of turbomachinery, according to the preamble of claim 1 and the preamble of Claim 7, but especially for cooling the flow in the radial gap between the compressor wheel and the housing of a radial compressor.

State of the art

To seal rotating systems, non-contact is used in turbomachinery Seals, especially labyrinth seals, are widely used. In fluid flow Separation gap between rotating and standing parts occurs as a result of forming flow boundary layers on a high friction. This leads to heating of the fluid in the separation gap and thus also to heating the components surrounding the separation gap. The high material temperatures result in a reduction in the lifespan of the corresponding components.

A simple radial compressor without one in the separating gap Sealing geometry is known from DE 195 48 852 A1. This also ensures that of flow shear layers on the rear wall of the compressor wheel Frictional heat for heating the compressor wheel and thus for a reduction in its lifespan.

Air cooling for radial compressors with a sealing geometry is known from EP 0 518 027 B1 known on the back of the compressor wheel. This is between the individual sealing elements an additional annulus on the housing wall side of the radial compressor. A cold gas is introduced into this annulus which is higher than that prevailing at the outlet of the compressor wheel Has pressure. The air supplied acts as impingement cooling. In doing so, she shares in the sealing area and flows mainly radially inwards and outwards. This should also have a blocking effect against the flow of Separation gap achieved with hot compressor air from the outlet of the compressor wheel become.

However, the cooling effect that can be achieved in this way is due to several factors limited. For example, the air injection leads to an increase in pressure and thrust, which increases the bearing load. It also sets the temperature the available air is a limiting element. In particular with high-speed compressor wheels and with high pressure ratios, As they are common in modern turbocharger construction, situations can arise come where this type of cooling is not sufficient.

In addition to direct cooling, DE 196 52 754 A1 also includes indirect cooling Cooling the rear wall of the compressor wheel or the one flowing through the separation gap Known medium. For this is on or in the back wall and with this housing part forming the separation gap, one with the lubricating oil system of the turbocharger connected supply and distribution device. As a cooling medium the oil used for bearing lubrication, including the lubricating oil circuit of the turbocharger is tapped. A disadvantage of this cooling is the relatively high level Oil requirement and the additional amount of heat to be dissipated by the oil cooler. This leads to an increased volume of the cooler. There is also one Accident with damage to the corresponding components increases the risk of deflagration. Just as with direct cooling is the same with indirect cooling Cooling achievable cooling effect is limited, for which in addition to the temperature of the in cooling fluids that can be used in practice, in particular the small amount available Construction volume can be identified as the cause.

From US 2,384,251 A a compressor is known in which one Stator blading-receiving housing cavities for the passage a coolant.

Presentation of the invention

The invention tries to avoid all these disadvantages. You have the task is based on a method for cooling that is improved with regard to its cooling effect the flow in between rotors and stators of turbomachinery Creating radial gaps. In addition, a simple, inexpensive and robust device for implementing the method can be specified.

According to the invention, this is achieved in that in a method according to the preamble of claim 1, both a stator part adjacent to the radial gap acted upon with a first cooling fluid as well as a second, gaseous one Cooling fluid is introduced into the radial gap.

Due to the use of a first cooling fluid for indirect and additional a second cooling fluid for direct cooling of the radial gap Partial flow of the working fluid of the turbomachine can be clearly improved cooling effect and also a better cooling effectiveness can be achieved. It is only this double cooling of the radial gap that enables another Lowering the temperature of the thermally heavily loaded rotor down to temperature ranges, which cannot be achieved with conventional cooling configurations were.

For this purpose, there is at least one inside the stator part adjacent to the radial gap Recess formed or arranged at least one cavity on the stator. The recess or cavity is both with a feed line as well connected to a discharge line for the first cooling fluid. In addition, are at the radial gap at least one feed channel and a discharge device for the second cooling fluid arranged.

Water is particularly advantageous as the first cooling fluid and water as the second cooling fluid Air used.

Water has a slightly higher density than the known lubricating oils as well a specific heat capacity that is about twice as large. Because of a cooling medium dissipated heat flow proportional to the product of density and specific heat capacity is the first thing to appear when using water Cooling fluid is a clear advantage over oil cooling. With the same mass flow and the same temperature of the water can thus be obtained from the Radial gap flowing medium over the stator to be cooled larger Amount of heat is withdrawn. The cooling effect on those adjacent to the radial gap Areas of the rotor are therefore also larger. Conversely becomes a smaller one for dissipating the same amount of heat compared to lubricating oil Mass flow of cooling water needed, which means the supply and discharge for the cooling fluid can be dimensioned correspondingly smaller.

Depending on the wall thickness on the rotor side, which is kept as low as possible can be, by the water gap immediately adjacent to the radial gap an improved cooling effect can be achieved inside the stator part. However, instead of the recess in the stator part, the cavity described on Stator part formed, so with a good cooling effect, a simpler and cheaper production can be realized.

The use of air as the second cooling fluid proves to be particularly so as beneficial because it is both in the environment and in the turbomachine even in sufficient quantity, with sufficient pressure and with suitably lower Temperature is available.

In one of an internal combustion engine, a charge air cooler and an exhaust gas turbocharger existing system is either fresh water from outside the System or advantageously water present in the system is used as the first cooling fluid. In the latter case, this takes place in a cooling water circuit of the charge air cooler located cooling water use, which is upstream of the charge air cooler is branched off. The fixed stator part is a housing part of a Radial compressor, which the radial gap to the rotor, i.e. for rotating Compressor wheel of an exhaust gas turbocharger limited.

If, on the other hand, oil is used as the first cooling fluid, this can be advantageous the lubricating oil system that is already present in the bearing housing of the turbomachine be branched off. In this way it can be a relatively simple and therefore inexpensive device can be created. Is it the first cooling fluid a gaseous medium, this can be used for both direct and can be used for indirect cooling.

When using helium or gases from low-temperature fluids, such as liquid nitrogen, carbon tetrachloride and benzene nitride first and / or second cooling fluid, a particularly good cooling effect can be achieved.

Brief description of the drawing

In the drawing is an embodiment of the invention using one with a Internal combustion engine connected exhaust gas turbocharger shown.

Fig. 1

eine schematische Darstellung des mit der Brennkraftmaschine verbundene Abgasturboladers;

Fig. 2

einen Teillängsschnitt durch den Radialverdichter des Abgasturboladers;

Show it:

Fig. 1

a schematic representation of the exhaust gas turbocharger connected to the internal combustion engine;

Fig. 2

a partial longitudinal section through the radial compressor of the exhaust gas turbocharger;

Only the elements essential for understanding the invention are shown. The direction of flow of the work equipment is indicated by arrows.

Way of carrying out the invention

FIG. 1 shows a schematic illustration of one with a diesel engine trained internal combustion engine 1 interacting exhaust gas turbocharger 2. The latter consists of a radial compressor 3 and an exhaust gas turbine 4, which have a common shaft 5. The radial compressor 3 is via a charge air line 6 and the exhaust gas turbine 4 via an exhaust gas line 7 with the internal combustion engine 1 connected. In the charge air line 6, i.e. between the radial compressor 3 and the internal combustion engine 1, a charge air cooler 8 is arranged. The charge air cooler 8 has a cooling water circuit 9 with one, not shown Supply or discharge.

The radial compressor 3 is equipped with a compressor housing 10 in which a rotor 11 designed as a compressor wheel and connected to the shaft 5 is arranged is. The compressor wheel 11 has one with a large number of moving blades 12 occupied hub 13. Between the hub 13 and the compressor housing 10 a flow channel 14 is formed. Connects downstream of the blades 12 a radially arranged, bladed diffuser 15 on the flow channel 14, which in turn opens into a spiral 16 of the radial compressor 3. The compressor housing 10 mainly consists of an air inlet housing 17, a Air outlet housing 18, a diffuser plate 19 and one as a partition to one Bearing housing 21 of the exhaust gas turbocharger 2 designed stator part 20 (Fig. 2).

The hub 13 has a rear wall 22 and a fastening sleeve on the turbine side 23 for shaft 5. The fastening sleeve 23 is from the intermediate wall 20th of the compressor housing 10 added. Of course, another suitable one Compressor wheel-shaft connection can be selected. The same is true Use of a non-bladed diffuser possible.

Between the rotating compressor wheel 11, i.e. its rear wall 22 and the fixed partition 20 of the compressor housing 10 inevitably exists a separation gap, which is formed as a radial gap 24 in a radial compressor 3 is. The radial gap 24 is with a between the fastening sleeve 23 and the intermediate wall 20 arranged sealing ring 34 opposite the bearing housing 21 sealed. Of course, this seal can also be made in a Radial gap 24 arranged labyrinth seal can be realized (not shown). In the intermediate wall 20 of the compressor housing 10 is a circumferential recess 26 designed and with both a supply and a discharge line 27, 28 connected for a first cooling fluid 29. To achieve the highest possible cooling effect To achieve the adjacent compressor wheel 11, the partition 20 on the compressor wheel side of the recess 26 is made as thin as possible. This is done at the manufacture of the intermediate wall 20 is cast in a corresponding core, which must then be removed again. Of course, can be in the partition 20 also cast a thin-walled tube sealed at both ends be, the interior of which then forms the recess 26 (not shown).

When the exhaust gas turbocharger 2 is operating, the compressor wheel 11 sucks as the working medium 31 ambient air acting as a main flow 32 through the flow channel 14 and the diffuser 15 elongated in the spiral 16, further compressed there and finally via the charge air line 6 for charging the turbocharger 2 connected internal combustion engine 1 is used. Before that, however, takes place in the charge air cooler 8 a corresponding cooling of the heated during the compression process Working medium 31.

On its way from the flow channel 14 to the diffuser 15, it acts on the radial compressor 3 heated main flow 32 of the working medium 31 as a leakage flow 33 also the radial gap 24, whereby the compressor wheel 11 additionally is heated. However, because the operating temperature in the outer area of the compressor wheel 11 is largest, there is a particularly high material load there on. In the recess immediately adjacent to this critical area 26 of the intermediate wall 20 is used as cooling fluid 29 from the cooling water circuit 9 of the intercooler 8 branched cooling water. It is coming thus for indirect cooling of the leakage flow located in the radial gap 24 33 and thus also the compressor wheel 11. The branching takes place of the cooling fluid 29 upstream of the charge air cooler 8, so that with the relative cold cooling water effective cooling can be achieved. After the cooling process the now heated cooling fluid 29 is downstream via the discharge line 28 of the charge air cooler 8 fed back into the cooling water circuit 9 (Fig. 1). Naturally can instead of in the system of internal combustion engine 1, intercooler 8 and Exhaust gas turbocharger 2 existing cooling water and fresh water from outside of the system are supplied as cooling fluid 29 (not shown).

In addition to the indirect cooling described so far, there is direct cooling the leakage flow 33 is provided. There are several tangential to the back wall 22 of the compressor wheel 11 in the radial gap 24 opening feed channels 40 for a second cooling fluid 41 both the bearing housing 21 and the diffuser plate 19 arranged penetrating (Fig. 2). The feed channels 40 are downstream of the charge air cooler 8 connected to the charge air line 6, so that second Cooling fluid 41 cooled charge air is used (Fig. 1). Of course you can the second cooling fluid 41 is also introduced into the radial gap at another point (not shown).

The tangential introduction of the second cooling fluid 41 results in pure film cooling the entire rear wall 22 of the compressor wheel 11 realized. The second Cooling fluid 41 replaces the hot leakage flow 33, so that the Back wall 22 of the boundary layer forming the compressor wheel 11 from the very beginning is mainly formed by the cooled charge air. The subsequent one The second cooling fluid 41 is discharged via a in the intermediate wall 20 of the Compressor housing 10 attacking discharge device, not shown 42. This combination of indirect and direct cooling has a special one Cooling effect because the two cooling options complement each other in their effect and thus for a very high temperature reduction in the compressor wheel 11 to care.

Of course, other cooling media, such as helium or gases from cryogenic fluids (e.g. liquid nitrogen, carbon tetrachloride, benzene nitride, etc.) can be used.

If oil is used as the first cooling fluid 29, this can be supplied externally or advantageously from the in the bearing housing 21 of the exhaust gas turbocharger 2 anyway existing lubricating oil system can be branched off (not shown). To this A relatively simple and therefore inexpensive supply is also possible suitable cooling fluids possible.

LIST OF REFERENCE NUMBERS

1

Internal combustion engine

2

turbocharger

3

centrifugal compressors

4

exhaust turbine

5

wave

6

Turbo pipe

7

exhaust pipe

8th

Intercooler

9

Cooling water circuit

10

compressor housing

11

Rotor, compressor wheel

12

blade

13

hub

14

flow channel

15

diffuser

16

spiral

17

Air intake housing

18

Air outlet housing

19

diffuser plate

20

Stator part, partition

21

bearing housing

22

rear wall

23

mounting sleeve

24

Radial gap, separation gap

25

labyrinth seal

26

recess

27

supply line

28

discharge line

29

first cooling fluid

31

working medium

32

mainstream

33

leakage flow

34

sealing ring

40

feed

41

second cooling fluid

42

removal device

Claims (10)

1. Method for cooling the flow in radial gaps formed between rotors and stators of turbomachines, characterized in that a first cooling fluid (29) is admitted to a stator part (20) adjacent to the radial gap (24) and a second, gaseous cooling fluid (41) is introduced into the radial gap (24).
2. Method according to Claim 1, characterized in that the first cooling fluid (29) is introduced into a recess (26) formed in the stator part (20) or into a cavity arranged at the stator part (20).
3. Method according to Claim 1 or 2, characterized in that water is used as first cooling fluid (29).
4. Method according to Claim 3, characterized in that fresh water from outside a system consisting of an internal combustion engine (1), a charge-air cooler (8) and an exhaust-gas turbocharger (2) is used as first cooling fluid (29).
5. Method according to Claim 3, characterized in that water present in a system consisting of an internal combustion engine (1), a charge-air cooler (8) and an exhaust-gas turbocharger (2) is used as first cooling fluid (29).
6. Method according to Claim 5, characterized in that cooling water present in a cooling-water circuit (9) of the charge-air cooler (8) is used as first cooling fluid (29) and the latter is branched off upstream of the charge-air cooler (8).
7. Method according to Claim 1, characterized in that oil, helium or gases from very-low-temperature fluids are used as first cooling fluid (29).
8. Method according to Claim 1, characterized in that air, helium or gases from very-low-temperature fluids are used as second, gaseous cooling fluid (41).
9. Arrangement for carrying out the method according to Claim 1, in which a fixed stator part (20) is arranged so as to define the radial gap (24) relative to the rotor (11), characterized in that

   a) at least one recess (26) is formed in the interior of the stator part (20) or at least one cavity is arranged at the stator part (20), and the recess (26) or the cavity is connected to both a feed line (27) and a discharge line (28) for the first cooling fluid (29) and

   b) at least one feed passage (40) as well as a discharge device (42) for the second cooling fluid (41) are arranged at the radial gap (24).
10. Arrangement according to Claim 9, characterized in that the fixed stator part (20) is designed as part of a compressor casing (10) of a radial compressor (3), and this part bounds the radial gap (24) relative to a rotating compressor impeller (11) of an exhaust-gas turbocharger (2).

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