EP3239533A1 - Axial turbomachine - Google Patents

Abstract

An axial turbomachine comprises a rotor (1) with hub (3) and blades (4) and a fixed tubular housing (5). On the inner wall of the housing (5) a radially encircling annular web (7) is applied. The blades (4) have at their ends corresponding radial grooves (8). In the area of the annular web (7), the head gap (6) is defined by the contours of the annular web (7) and the corresponding radial grooves (8). This results in a higher efficiency and a quieter operating noise.

Description

The invention relates to axial turbomachinery such as fans, pumps, compressors, air, steam and gas turbines.

Such a turbomachine or turbomachine has a rotor which rotates about a fixed axis of rotation. The rotor includes a hub and a number of blades or rotor blades which project radially outwardly from the hub. The blades can but need not necessarily have a profiled cross section. The blades are also inclined so that they extend in the axial direction between a front edge and a trailing edge in the depth.

The rotor with the blades is surrounded by a tubular housing. In certain turbomachinery, the tubular housing merges at its air inlet side into a funnel-shaped inlet nozzle of steadily widening radius.

Between the radial ends of the blade heads and the inner wall of the housing results structurally unavoidable, a radial head gap, which works as a non-contact seal between the suction and pressure chamber or inlet and outlet side of the machine. The unavoidable flow across the head gap due to the pressure difference between the front and back of the rotor reduces the overall efficiency of the engine while increasing the emission of flow-induced sound. This is due to vortex-like secondary flow phenomena in the region of the head gap.

In order to reduce pressure losses and to reduce unwanted sound radiation, it is endeavored to keep the radial head gap as small as possible. However, there are constructive limits. Because on the one hand rotor and housing can be slightly out of round due to production. Further, due to manufacturing tolerances, the rotor may make eccentric or tumbling movements, so that there is a risk that the blade heads will come into contact with the inner wall of the housing. Due to residual imbalances, the rotor can also vibrate in the rotor plane.

Contact between the blade ends and the inner wall of the housing, especially in the case of rapidly rotating blades, can result in strong noises, sparking or even tearing off of a blade with total failure of the machine. Therefore, the head gap must not be made too small, but must not fall below a certain minimum, which is predetermined by construction and material.

There have been proposed various constructive measures to improve the efficiency and to reduce the Kopfspaltgeräusches.

DE 4310104 A1 proposes to limit the noise emission of the turbomachine, a turbulence generator in the annular gap between the blade tips of the blades and the inner surface of the housing. This turbulence generator can be attached by a to the inner surface of the housing Sandpaper, a wire mesh or textile fabric or a roughening of the inner surface of the housing.

EP 1 278 943 B and the associated WO 01/083950 describe a turbomachine with a sealing element between the rotor and the housing. The sealing member protrudes from the entire inner surface of the housing and into a gap extending between an outer surface of an annular tire and the inner surface of the housing to reduce swirls and minimize air leakage through the gap. The sealing element may be formed from fibers, bristles or threads.

US Pat. No. 6,471,472 B1 or the parallel EP 1 081 388 B1 disclose a fan in which a blocking device in the form of a strip-shaped brush is provided between inlet side and pressure side.

Another known measure to allow very small head gaps lies in the lining or coating of the inner wall of the housing with an easily abradable material, such as foam or porous plastic, so that a brief contact of the blades, so-called tarnishing, without significant damage remains. During operation, this additional soft material is removed so that automatically sets a sufficient head gap. Disadvantages are the significantly increased production costs and the low stability of the material, as well as problems in the break-in phase.

To reduce the noise caused by the secondary flow at the head gap between the blade and the housing, it has also been attempted to reduce this secondary flow at the blade tips by a co-rotating belt and at the same time supply the unavoidable recirculation flow in the region of the gap to the rotor.

DE 20 2004 005 548 U proposes to provide co-rotating plate-shaped elements, so-called winglets, at the head of the blade.

All of these measures described are structurally complex, have moderate effect and / or reduce the service life of the machine.

The technical problem to be solved is thus in the structural design of an axial turbomachine of the type described above so that a significant improvement in the efficiency and a quieter run is achieved without substantial reduction of the head gap.

In solving this problem is based on an axial turbomachine according to the preamble of claim 1. The problem is solved according to the characterizing part of claim by the fact that on the inner wall of the housing, a radially encircling annular ridge is applied, and that the blade heads have corresponding radial grooves ,

Due to the inventive interaction of annular web and corresponding radial grooves which reduces the swirling secondary flow in the head gap or suppressed. This also reduces or prevents an interaction of the vortex-like secondary flow with other regions of the blade or neighboring blades and without the annular web of the invention and corresponding radial grooves, and ultimately the emission of flow-induced sound. In addition, the interaction of annular web and corresponding radial grooves leads to a better sealing effect between the pressure and suction side, without the minimum radial dimension of the head gap would have to be reduced. The head gap is folded only in its axial extent and thus somewhat extended, but with unchanged length of the housing and unchanged axial extension (depth) of the blades at the head end.

Measurements showed an increase in efficiency of up to 10 percent in comparison to a structurally identical turbomachine without an annular web and corresponding radial grooves.

Acoustic measurements resulted in a surprisingly large reduction of the sound pressure of more than 5 dB in the audible frequency range and in certain frequency ranges even a sound pressure reduction of more than 10 dB.

The construction according to the invention has the great advantage that the radially encircling ring land can be produced in a very simple manner in terms of production and also that the introduction of the corresponding radial grooves into the blade heads does not require much effort. Another advantage is that even existing machines can be easily retrofitted. Ring web and radial grooves are not subject to greater wear than the machine itself, so that no disadvantages are to be feared in terms of stability.

The head gap is defined in the region of the ring land by the contours of the ring land and the corresponding contours of the radial grooves on the blades. The minimum distance between housing and rotor is not required by the inventive displacement of the head gap in the region of the ring land inward, or at least not necessarily smaller than anyway necessary. However, it is possible to optionally select the minimum distance between the walls of the annular web and the radial grooves as the measure of the head gap outside the region of the annular land, for example, to further reduce the risk of tarnishing especially in the region of the annular land.

Advantageously, the annular land projects at least a little way into the radial grooves. This creates a labyrinthine head gap with a particularly good sealing effect. Preferably, the height of the annular web corresponds approximately to the depth of the corresponding radial grooves, and the distance between the annular web and the groove wall corresponds approximately to the dimension of the head gap outside the region of the annular web.

The axial extent, ie the width of the annular web, preferably has a dimension that is significantly smaller than the axial extension, that is to say the so-called depth of the blade at the head end. The optimal ratio between the width of the ring land and the depth of the blade is between 1: 5 and 1:10.

The ring land may have rectangular, in particular square cross-section. Particularly preferred is a triangular cross section, in particular a cross section in the form of an approximately equilateral triangle, the tip of which points radially in the direction of the axis of rotation. The contour or cross-sectional shape of the radial grooves on the blades preferably follows the cross-sectional shape of the annular web, but also slightly different contours are conceivable. It is important, above all, that the annular web and radial grooves are precisely aligned in the axial direction.

The annular land is advantageously integrally formed on the housing. As a material for the housing in particular plastic or metal into consideration. In particular in plastic, a housing with an inventive annular web can be produced very easily, for example by injection molding.

Alternatively, the ring land can of course be made separately and subsequently applied to the inner wall of the housing, for example by gluing. Optionally, the ring land can also be prefabricated as an open ring, so that it can easily be subsequently inserted into the tubular housing.

Since the outer shape of the housing has no influence on the aerodynamic properties of the machine, the annular web could also be produced by a constriction or, in the case of a metal housing, by rolling. This results in rather round contours or cross-sectional shapes of annular web and corresponding radial grooves.

Although the annular web is preferably made of the same material as the rest of the housing, it may be advantageous in special cases when the Alternatively, ring bridge is made of a softer, easily removable material. The ring land can also be designed as a replaceable wearing part.

Particularly preferred is an axial position of the annular land and the corresponding radial grooves not exactly in the middle of the axial extent or depth of the blade heads, but an asymmetrical position in the region of the rear blade edge. This has proven to be particularly acoustically particularly advantageous.

The provision according to the invention of an annular web on the inner wall of the housing and of corresponding radial grooves on the blade ends has proved to be very advantageous and effective, in particular in turbomachines in which the blade heads have cylindrical end surfaces at their radially outer ends, which extend coaxially to the inner wall of the housing and thus define the head gap. The radial grooves are then in these cylindrical end surfaces, between the leading edge and trailing edge of the blade heads. Due to the inclination of the blade, the radial groove does not run parallel to the main axis of the blade profile, but necessarily exactly in the circumferential direction, that is, the central axis of the radial groove extends obliquely relative to the main profile axis.

Instead of blades with airfoil-like profiling, it is equally possible to use simple blades pressed from sheet metal with a constant thickness. Even with such blades, the invention works very well.

Figur 1a

eine axiale Turbomaschine nach dem Stand der Technik, in einem stark vereinfachten Prinzipbild;

Figur 1b

eine erfindungsgemäße Turbomaschine im Prinzip;

Figur 2a

eine erfindungsgemäße Turbomaschine in einer Ansicht von der Seite, teilweise geschnitten;

Figur 2b

eine Ausschnittsvergrößerung des Bereichs A von Figur 2a

Figur 2c

eine vergrößerte Draufsicht auf das Kopfende der Schaufel im Bereich B von Figur 2a;

Figur 3

Gehäuse und Rotor der Turbomaschine gemäß Figur 2a, perspektivisch.

The principle of the invention and an embodiment of a turbomachine according to the invention are explained below with reference to the accompanying drawings. Show it:

FIG. 1a

an axial turbomachine according to the prior art, in a simplified schematic diagram;

FIG. 1b

a turbomachine according to the invention in principle;

FIG. 2a

a turbomachine according to the invention in a view from the side, partially in section;

FIG. 2b

a detail enlargement of the area A of FIG. 2a

Figure 2c

an enlarged plan view of the head end of the blade in the area B of FIG. 2a ;

FIG. 3

Housing and rotor of the turbomachine according to FIG. 2a , in perspective.

The basic picture of FIG. 1a shows an axial turbomachine with a rotor 1, which rotates about a fixed axis of rotation 2. The rotor 1 comprises a hub 3 and radially outwardly projecting blades 4. A fixed, designed as a round tube housing 5 surrounds the rotor 1 coaxially. The rotor 1 is driven by a motor (not shown). Air or another gaseous fluid is sucked in on the inlet side (here on the left), compressed and blown out again on the outlet side (on the right).

Between the axially outer end of the blades 4 and the inner wall of the housing 5 remains a radial head gap 6, the dimension S must not be exceeded, if contact between blades 4 and 5 housing to be reliably avoided during operation. The head gap 6 represents a non-contact seal between the suction and pressure chamber of the machine. The smaller the dimension S of the head gap, the greater the sealing effect and the higher the efficiency of the turbomachine. The head gap flow causes noise.

FIG. 1b explains the principle of the invention. On the inner wall of the housing 5, a radial annular web 7 is applied. The blades 4 have a radial groove 8, which corresponds to the annular web 7 in position and cross section. Without the radial groove 8, the applied annular web 7 would reduce the diameter of the housing 5 and reduce the head gap 6 to the dimension S '. However, such a small head gap would not be sufficient to reliably prevent the starting of the blades 4. The radial groove 8, in shape and dimensions corresponds to the contour of the annular web 7, ensures a sufficiently large head gap 6, approximately with the dimension S, over the entire axial length of the blade 4 and in particular in the region of the annular web. 7

The turbomachine according to FIG. 2a has a rotor 10 which rotates about a rotation axis 20. The rotor 10 has a hub 30 which carries a number of radially outwardly projecting blades 40. A designed as a short round tube housing 50 surrounds the rotor 10 coaxially. To release the view of the blades 40 is in FIG. 2a the housing 50 drawn in a horizontal section through the axis of rotation 20.

On the inner wall of the housing 50, a small annular ridge 70 is applied. The contour of the annular web 70 corresponds approximately to an equilateral triangle whose tip points radially inwards to the axis of rotation 20. At the ends of the blades 40 radial grooves 80 are incorporated, which correspond to the annular ridge 70, that is, they also have triangular contour.

Towards the suction side, the housing 50 widens in a funnel shape to a suction nozzle 51. The housing 50 is made of metal, but may as well be made of plastic. The annular ridge 70 is integrally formed.

The rotor 10 is driven by a motor 90 via a shaft 100.

Especially FIG. 2b shows the non-contact engagement of the annular ridge 70 and the corresponding radial groove 80 on one of the blades 40. The two oblique edges of the annular ridge 70 are approximately parallel to the opposite walls of the radial groove 80. The tip of the annular ridge 70 and the triangle or V of the radial groove 80 aligned in the axial direction. The flanks of the annular web 70 and the walls of the radial groove 80 are at a distance from each other; In this area, the head gap 60 is thus defined by the contours of the annular web 70 and the corresponding radial groove 80. The harmful vortex structure of the flow in the area of the head gap is thereby dissolved, sometimes the flow over the head gap from the pressure on the suction side is also blocked. As a result, the machine runs much quieter and there is an increased sealing effect compared to a straight head gap (see. FIG. 1a ).

As in particular from Figure 2c can be seen, the blades 40 have a wing-like profiling. In addition, the blades 40 are at an oblique angle relative to the axis of rotation 20 (see. FIG. 2a ) and also show a twist. The blade heads 41 have a smaller width than the blade roots 42. The axial extent or depth between the leading edge 44 and the trailing edge 45 is smallest at the upper end of the blade heads 41.

Out Figure 2b and Figure 2c It will further be seen that the blade heads 41 have end surfaces 43; these are cylindrically curved in the radial direction and extend coaxially to the inner wall of the housing 50. The axial position of the annular web 70 is located near the trailing edge 45 of the blade head 41. In other embodiments, the end surfaces 43 are additionally contoured in the axial direction, the head gap narrows thereby constantly up to a minimum between Schaufelvorder- and trailing edge.

In particular from Figure 2c It is also clear that the radial grooves 80 extend at an acute angle obliquely with respect to the major axis of the airfoil-like profile of the blade head 41.

Instead of the wing-like profiled blades 40 as well as simple blades with a constant thickness, in particular pressed from a piece of sheet metal blades can be used.

reference numeral

1

rotor

2

axis of rotation

3

hub

4

shovel

5

casing

6

head gap

7

ring land

8th

radial groove

10

rotor

20

axis of rotation

30

hub

40

shovel

41

shovel head

42

blade root

43

end face

44

leading edge

45

trailing edge

50

casing

51

inlet nozzle

60

head gap

70

ring land

80

radial groove

90

engine

100

wave

Claims (10)

Axial turbomachine comprising
at least one rotor (1, 10) revolving around a fixed axis of rotation (2, 20) with a hub (3, 30) and radially outwardly projecting blades (4, 40)
a stationary tubular housing (5, 50) coaxially surrounding the rotor (1, 10) such that a radial head gap (6, 60) remains between the blade heads (41) and the inner wall of the housing (5, 50),
characterized in that
on the inner wall of the housing (5, 50) a radially encircling annular web (7, 70) is applied,
the blade heads (41) corresponding radial grooves (8, 80), so that the head gap (6, 60) in the region of the annular web (7, 70) by the contours of the annular web (7, 70) and the corresponding radial groove (8, 80 ) is defined. Turbomachine according to claim 1, characterized in that the annular web (7, 70) extends in the radial direction a little way into the radial grooves (8, 80). Turbomachine according to one of the preceding claims, characterized in that the height of the annular web (7, 70) and the depth of the corresponding radial grooves (8, 80) approximately to the extent of the head gap (6, 60) outside the region of the annular web (7, 70 ) corresponds. Turbomachine according to one of the preceding claims, characterized in that the annular web (7, 70) and the radial grooves (8, 80) have a cross section in the form of a triangle, wherein the apex of the triangle radially to the axis of rotation (2, 20) have. Turbomachine according to one of claims 1 to 3, characterized in that the annular web (7, 70) and the radial grooves (8, 80) have a rectangular cross section, in particular approximately square cross section. Turbomachine according to one of the preceding claims, characterized in that the annular web (7, 70) is integrally formed on the housing (5, 50). Turbomachine according to one of the preceding claims, characterized in that the annular web (7, 70) consists of an easily abradable material. A turbomachine according to any one of the preceding claims, characterized in that the blade heads (41) have at their radially outer ends cylindrical end surfaces (43) coaxial with the inner wall of the housing (50) and the radial grooves (80) in these end surfaces (43 ). Turbomachine according to one of the preceding claims, characterized in that the radial grooves (80) between the leading edge (44) and trailing edge (45) of the blade heads (41) are arranged. Turbomachine according to claim 9, characterized in that the radial grooves (80) in the vicinity of the pressure side facing the rear edge (45) are arranged.

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