WO2001029425A1

WO2001029425A1 - Method and device for cooling the flow in the radial gaps formed between rotors and stators of turbine-type machines

Info

Publication number: WO2001029425A1
Application number: PCT/CH1999/000496
Authority: WO
Inventors: Dirk Wunderwald; Mihajlo-Rüdiger BOTHIEN; Ulf Christian MÜLLER; Joachim Bremer; Jürg Greber; Helmut Gieszauf
Original assignee: Abb Turbo Systems Ag
Priority date: 1999-10-20
Filing date: 1999-10-20
Publication date: 2001-04-26
Also published as: KR20020041437A; CN1375041A; EP1222399A1; DE59906615D1; CN1258648C; JP2003515690A; EP1222399B1; AU6075799A; KR100637643B1

Abstract

The aim of the invention is to provide a method for cooling the flow in the radial gaps formed between rotors and stators of turbine-type machines which is improved in terms of the cooling effect; and a simple, economical and robust device for carrying out this method. To this end, the invention provides that a stator part (20) that is adjacent to the radial gap (24) is subjected to the effects of a first cooling fluid (29) and that a second, gaseous cooling fluid (41) is guided into the radial gap (24). At least one recess (26) is configured inside the stator part (20) that is adjacent to the radial gap (24) or at least one cavity is provided on the stator part (20) to this end. The recess (26) or cavity is connected to a delivery line (27) and to a discharge line (28) for the first cooling fluid (29). At least one delivery channel (40) and a discharge device (42) for the second cooling fluid (41) are also located on the radial gap (24).

Description

Method and device for cooling the flow in radial gaps formed between rotors and stators of turbomachinery

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 in particular 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 seals, especially labyrinth seals, are widely used in turbomachinery construction. In the fluid-flow separation gap between rotating and standing parts, a high level of friction occurs as a result of the flow boundary layers that form. This leads to heating of the fluid in the separation gap and thus also to heating of the components surrounding the separation gap. The high material temperatures reduce the lifespan of the corresponding components.

A simply constructed radial compressor without a sealing geometry formed in the separating gap is known from DE 195 48 852 A1. Here, too, the frictional heat generated on the rear wall of the compressor wheel as a result of flow shear layers causes the compressor wheel to heat up and thus reduces its service life.

Air cooling for radial compressors with a sealing geometry on the rear side of the compressor wheel is known from EP 0 518 027 B1. This is between the individual sealing elements, an additional annular space is formed on the housing wall side of the radial compressor. A cold gas is introduced into this annular space, which has a higher pressure than the pressure prevailing at the outlet of the compressor wheel. The air supplied acts as impingement cooling. It divides in the sealing area and flows mainly radially inwards and outwards. This is also intended to achieve a blocking effect against the flow of hot compressor air from the outlet of the compressor wheel.

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

In addition to direct cooling, indirect cooling of the rear wall of the compressor wheel or of the medium flowing through the separation gap is also known from DE 196 52 754 A1. For this purpose, a supply and distribution device connected to the lubricating oil system of the turbocharger is arranged on or in the rear part of the housing part which forms the separating gap. The oil used for bearing lubrication serves as the cooling medium, for which purpose the lubricating oil circuit of the turbocharger is tapped. A disadvantage of this cooling is the relatively high oil requirement and the additional amount of heat to be dissipated by the oil cooler. This leads to an increased construction volume of the cooler. In addition, there is an increased risk of deflagration in the event of an accident with damage to the corresponding components. Just as with direct cooling, the cooling effect that can be achieved with indirect cooling is also limited, for which, in addition to the temperature of the cooling fluids that can be used in practice, the small construction volume available can be identified as the cause. Presentation of the invention

The invention tries to avoid all these disadvantages. It is the object of the invention to provide a method for cooling the flow in radial gaps formed between rotors and stators of turbomachines which is improved with regard to its cooling effect. In addition, a simple, inexpensive and robust device for implementing the method is to be specified.

This is achieved according to the invention in that, in a method according to the preamble of claim 1, both a stator part adjacent to the radial gap is acted on by a first cooling fluid and a second, gaseous cooling fluid is introduced into the radial gap.

Due to the use of a first cooling fluid for indirect and additionally a second cooling fluid for direct cooling of the partial flow of the working medium of the turbomachine acting on the radial gap, a significantly improved cooling effect and also a better cooling effectiveness can be achieved. It is only this double cooling of the radial gap that enables the temperature of the thermally highly loaded rotor to be reduced further down to temperature ranges which were not achievable with the conventional cooling configurations.

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

Water is particularly advantageously used as the first cooling fluid and air as the second cooling fluid.

Water has a slightly higher density than the known lubricating oils and an approximately twice as large specific heat capacity. Since it has a cooling medium to be dissipated heat flow is proportional to the product of density and specific heat capacity, there is a clear advantage when using water as the first cooling fluid compared to oil cooling. With the same mass flow and temperature of the water, a larger amount of heat can thus be extracted from the medium flowing through the radial gap via the stator part to be cooled. The cooling effect on the areas of the rotor adjacent to the radial gap is therefore also greater. Conversely, a smaller mass flow of cooling water is required to dissipate the same amount of heat compared to lubricating oil, as a result of which the supply and discharge device for the cooling fluid can be dimensioned correspondingly smaller.

Depending on the wall thickness on the rotor side, which should be kept as small as possible, an improved cooling effect can be achieved by the water flow directly adjacent to the radial gap in the interior of the stator part. However, if the described cavity is formed on the stator part instead of the recess in the stator part, a simpler and more cost-effective production can also be achieved with a good cooling effect.

The use of air as the second cooling fluid proves to be particularly advantageous because it is available in sufficient quantities, with sufficient pressure and at a suitably low temperature both in the environment and in the turbomachine itself.

In a system consisting of an internal combustion engine, a charge air cooler and an exhaust gas turbocharger, 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, the cooling water located in a cooling water circuit of the charge air cooler is used, which is branched off upstream of the charge air cooler. In this case, the fixed stator part is a housing part ei ^¬ nes radial compressor, which delimits the radial gap to the rotor, that is, to the rotating compressor wheel of a turbocharger. If, on the other hand, oil is used as the first cooling fluid, it can advantageously be branched off from the lubricating oil system, which is already present in the bearing housing of the turbomachine. In this way, a relatively simple and therefore inexpensive device can be created. If the first cooling fluid is a gaseous medium, it can be used for both direct and indirect cooling.

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

Brief description of the drawing

In the drawing, an embodiment of the invention is shown using an exhaust gas turbocharger connected to an internal combustion engine.

Show it:

Figure 1 is a schematic representation of the exhaust gas turbocharger connected to the internal combustion engine.

2 shows 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 representation of an exhaust gas turbocharger 2 that interacts with an internal combustion engine 1 designed as a diesel engine. 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 connected to the combustion air via a charge air line 6 and the exhaust gas turbine 4 via an exhaust line 7 engine 1 connected. A charge air cooler 8 is arranged in the charge air line 6, ie between the radial compressor 3 and the internal combustion engine 1. The charge air cooler 8 has a cooling water circuit 9 with a supply or discharge, not shown.

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. The compressor wheel 11 has a hub 13 with a plurality of rotor blades 12. A flow channel 14 is formed between the hub 13 and the compressor housing 10. Downstream of the blades 12, a radially arranged, bladed diffuser 15 adjoins 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, an air outlet housing 18, a diffuser plate 19 and a stator part 20 designed as an intermediate wall to a bearing housing 21 of the exhaust gas turbocharger 2 (FIG. 2).

The hub 13 has a rear wall 22 on the turbine side and a fastening sleeve 23 for the shaft 5. The fastening sleeve 23 is received by the intermediate wall 20 of the compressor housing 10. Of course, another suitable compressor wheel / shaft connection can also be selected. It is also possible to use an unbladed diffuser.

Between the rotating compressor wheel 11, ie its rear wall 22 and the fixed intermediate wall 20 of the compressor housing 10, there is inevitably a separating gap which is designed as a radial gap 24 in a radial compressor 3. The radial gap 24 is sealed off from the bearing housing 21 by a sealing ring 34 arranged between the fastening sleeve 23 and the intermediate wall 20. Of course, this seal can also be realized via a labyrinth seal arranged in the radial gap 24 (not shown). A circumferential recess 26 is formed in the intermediate wall 20 of the compressor housing 10 and is connected to both a supply line and a discharge line 27, 28 for a first cooling fluid 29. To ensure the highest possible cooling To achieve the effect of the adjacent compressor wheel 11, the intermediate wall 20 on the compressor wheel side of the recess 26 is made as thin as possible. For this purpose, a corresponding core is cast in during the manufacture of the intermediate wall 20, which must then be removed again. Of course, a thin-walled tube that is closed at both ends can also be cast into the intermediate wall 20, the interior of which then forms the recess 26 (not shown).

When the exhaust gas turbocharger 2 is operating, the compressor wheel 11 sucks in ambient air as the working medium 31, which, as a main flow 32, enters the spiral 16 via the flow channel 14 and the diffuser 15, compresses there further and finally via the charge air line 6 for charging the exhaust gas turbocharger 2 connected internal combustion engine 1 is used. However, the working medium 31 heated during the compression process is cooled beforehand in the charge air cooler 8.

On its way from the flow channel 14 to the diffuser 15, the main flow 32 of the working medium 31 heated in the radial compressor 3 also acts on the radial gap 24 as a leakage flow 33, as a result of which the compressor wheel 11 is additionally heated. However, because the operating temperature is greatest in the outer area of the compressor wheel 11, a large material load occurs in particular there. Cooling water which is branched off from the cooling water circuit 9 of the charge air cooler 8 is introduced as cooling fluid 29 into the recess 26 of the intermediate wall 20 which is arranged directly adjacent to this critical area. There is thus indirect cooling of the leakage flow 33 located in the radial gap 24 and thus also of the compressor wheel 11. The cooling fluid 29 is branched off upstream of the charge air cooler 8, so that effective cooling can be achieved with the relatively cold cooling water. The now heated Kuhlfluid is after the cooling ^¬ process stream 29 via the drain line 28 ^¬ fed back into the cooling water circuit 9 from the charge air cooler 8 (Fig. 1). Na ^¬ Türlich can take place in the system of the internal combustion engine 1, the charge air cooler 8 and Exhaust gas turbocharger 2 existing cooling water and fresh water from outside the system as cooling fluid 29 (not shown).

In addition to the indirect cooling described so far, direct cooling of the leakage flow 33 is provided. For this purpose, a plurality of feed channels 40 for a second cooling fluid 41 opening tangentially to the rear wall 22 of the compressor wheel 11 and arranged in the radial gap 24 are arranged so as to penetrate both the bearing housing 21 and the diffuser plate 19 (FIG. 2). The supply channels 40 are connected downstream of the charge air cooler 8 to the charge air line 6, so that cooled charge air is used as the second cooling fluid 41 (FIG. 1). Of course, the second cooling fluid 41 can also be introduced into the radial gap at a different point (not shown).

A pure film cooling of the entire rear wall 22 of the compressor wheel 11 is achieved by the tangential introduction of the second cooling fluid 41. The second cooling fluid 41 replaces the hot leakage flow 33, so that the boundary layer which forms on the rear wall 22 of the compressor wheel 11 is formed from the start, above all, by the cooled charge air. The subsequent discharge of the second cooling fluid 41 takes place via a discharge device 42 which engages in the intermediate wall 20 of the compressor housing 10. This combination of indirect and direct cooling has a special cooling effect because the two cooling options complement each other in their effect and thus ensure a very high temperature reduction in the compressor wheel 11.

Of course, other cooling media such as helium or gases from low-temperature fluids (e.g. liquid nitrogen, carbon tetrachloride, benzene nitride, etc.) can also be used as the first and second cooling fluids 29, 41.

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

LIST OF REFERENCE NUMBERS

1 internal combustion engine

2 turbochargers

3 radial compressors

4 exhaust gas turbine

5 wave

6 charge air line

7 exhaust pipe

8 intercoolers

9 cooling water circuit

10 compressor housing

11 rotor, compressor wheel

12 moving blade

13 hub

14 flow channel

15 diffuser

16 spiral

17 air inlet housing

18 air outlet housing

19 diffuser plate

20 stator part, partition

21 bearing housing

22 rear wall

23 fastening sleeve

24 radial gap, separation gap

25 labyrinth seal recess

supply line

Drain line first cooling fluid

working medium

mainstream

leakage flow

sealing ring

Second cooling fluid supply channel

removal device

Claims

claims

1. A method for cooling the flow in radial gaps formed between rotors and stators of turbomachinery, characterized in that a stator part (20) adjacent to the radial gap (24) is acted upon by a first cooling fluid (29) and a second, gaseous cooling fluid (41) in the radial gap (24) is initiated.

2. The 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 on the stator part (20).

3. The method according to claim 1 or 2, characterized in that water is used as the first cooling fluid (29).

4. The method according to claim 3, characterized in that fresh water from outside of a system consisting of an internal combustion engine (1), a charge air cooler (8) and an exhaust gas turbocharger (2) is used as the first cooling fluid (29).

5. The method according to claim 3, characterized in that existing in an internal combustion engine (1), an intercooler (8) and an exhaust gas turbocharger (2) existing water is used as the first cooling fluid (29).

6. The method according to claim 5, characterized in that in a cooling water circuit (9) of the charge air cooler (8) existing cooling water is used as the first cooling fluid (29) and the latter is branched upstream of the charge air cooler (8).

7. The method according to claim 1, characterized in that oil, helium or gases from low-temperature fluids are used as the first cooling fluid (29).

8. The method according to claim 1, characterized in that air, helium or gases from low-temperature fluids are used as the second, gaseous cooling fluid (41).

9. The device for carrying out the method according to claim, in which a fixed stator part (20) is arranged to limit the radial gap (24) to the rotor (11), characterized in that a) at least one recess (26) in the interior of the stator part (20) ) or at least one cavity is arranged on the stator part (20) and the recess (26) or the cavity is connected both to a supply line (27) and to a discharge line (28) for the first cooling fluid (29) and b) at least one Feed channel (40) and a discharge device (42) for the second cooling fluid (41) are arranged on the radial gap (24).

10. The device according to claim 9, characterized in that the fixed stator part (20) is formed as part of a compressor housing (10) of a radial compressor (3) which the radial gap (24) to a rotating compressor wheel (11) of an exhaust gas turbocharger (2) limited.