TURBOCIFIER WITH ADAPTED MERIDIAN CONTOUR OF THE BLADES AND COMPRESSOR WALL

Description

[0001] The invention relates to a turbo compressor with a compressor housing and a compressor wheel with blades, in which the compressor wheel is rotatably mounted relative to the compressor housing and is spaced apart by a head gap between cover-free blade upper edges of the blades and a compressor wall of the compressor housing facing the blade upper edges.

[0002] In state-of-the-art turbo compressors, the bladed compressor wheel rotates relative to the stationary compressor casing, generating a main flow with axial intake and radial discharge. A minimum head gap is provided between the blades of the compressor wheel and the casing wall to enable contact-free rotation of the compressor wheel. The head gap runs along the top edge of the blade and the casing wall, viewed in the meridian plane of the compressor wheel, with both the casing wall and the top edge of the blade exhibiting a continuous profile from the axial intake side to the radial discharge side. In turbo compressors, the meridian plane is defined as any plane passing through the axis of rotation, viewed in the circumferential direction.

[0003] The problem is that at small mass flows the compressor characteristic curve, which is determined by a constant speed characteristic curve in the pressure build-up versus mass flow diagram, is aerodynamically limited by the flow separation limit or the surge limit.

[0004] Printed prior art in the present technical field is disclosed in the documents DE 10 2013 201 763 A1, DE 10 2016 001 484 A1 and WO 2014 / 004238 A1. The document FR 893 205 A discloses a turbo compressor with a compressor wheel arranged in a compressor housing with cover-free blade upper edges of the compressor blades, wherein the blade upper edges are provided with a plurality of elevations and the opposite housing wall is provided with a plurality of recesses interacting with the elevations.

[0005] The invention is therefore based on the object of shifting the compressor characteristic curve of the turbocompressor at low mass flows in such a way that the flow separation limit or surge limit is shifted toward smaller mass flows, thereby expanding the operating range of the turbocompressor. At the same time, efficiency and pressure build-up are to be increased.

[0006] This problem is solved by the combination of features according to patent claim 1.

[0007] According to the invention, a turbocompressor with a compressor housing and a compressor wheel with blades is proposed. The compressor wheel is rotatably mounted relative to the compressor housing and is spaced apart by a head gap between the cover-free upper blade edges of the blades and a compressor wall of the compressor housing facing the upper blade edges. Both the upper blade edges of the blades and the housing wall each have at least one recess and at least one elevation along their respective meridian contours, which interact locally, so that the head gap defines a Z-shaped profile in the region of the recess and elevation when viewed in a meridian plane.

[0008] The special design of the facing blade upper edges and casing wall creates a backflow within the tip gap, counter to the axially drawn and radially discharged main flow. The blade upper edges and casing wall exhibit a discontinuous contour across the continuous meridian line, formed by interacting recesses and immediately adjacent elevations on the blade upper edges and casing wall relative to the continuous meridian line. The Z-shaped shape of the tip gap is determined by two transverse limbs and a connecting limb connecting the transverse limbs. The recesses serve to form the two transverse limbs, while the elevations form the one connecting limb.

[0009] Preferably, the recesses of the blade upper edges are shaped complementarily to the elevation of the housing wall and the recesses of the housing wall are shaped complementarily to the elevation of the blade upper edges in order to design the Z-shaped course of the head gap.

[0010] The return flow through the tip gap, counter to the main flow generated by the compressor wheel, encounters the recesses or elevations of the blade top edges or the casing wall, is thereby obstructed, and flows back into the main flow. This achieves the advantageous flow effects necessary to achieve the tasks.

[0011] The positioning of the recesses or the complementary elevations on the blade upper edges or the casing wall also has a beneficial effect. A meridian length L of the compressor wheel, from its intake-side axial leading edge to its discharge-side radial trailing edge, is set between the values ​​0 <L<1 bestimmt. Bevorzugt und strömungstechnisch optimal ist eine Ausführung, bei welcher der mindestens eine Rücksprung sowie die mindestens eine Erhöhung der Gehäusewand und der Schaufeloberkanten in einem Bereich 0,3<L<0,7, weiter bevorzugt 0,4<L<0,5 ausgebildet sind.

[0012] In order to form the Z-shaped profile of the head gap, as seen in the meridian plane, the invention provides that the casing wall and the blades each have stop surfaces facing one another for flow through the head gap. The stop surfaces therefore extend perpendicularly or at an angle to the previous or following flow section of the head gap, as seen in the meridian plane, so that the return flow through the head gap impacts the stop surface and is fed back into the main flow running in the opposite direction. Because recesses and elevations are provided both on the upper edges of the blades and on the casing wall, the stop surfaces extend perpendicular or essentially perpendicular to the return flow, but the head gap is nevertheless maintained in the entire area between the compressor wheel and the compressor casing, i.e. also in the area of ​​the Z-shaped section of the recesses and elevations.According to the invention, it is further provided that the stop surfaces run parallel at an angle α=±15° with respect to a perpendicular to a tangent of the meridian course of the housing wall and / or the upper blade edges of the compressor wheel.

[0013] In an advantageous design variant, the stop surfaces on the casing wall and the upper blade edges run parallel to an axial plane perpendicular to the rotational axis of the compressor wheel at an angle α that is greater than 0°, preferably 15-45°, toward the intake side of the compressor wheel. This allows the stop surface on the casing wall to be inclined to the main flow, and the return flow in the head gap is already deflected back toward the main flow via the stop surface.

[0014] In one embodiment of the turbocompressor, the head gap is designed to have a constant head gap width. The "head gap width" is determined by the distance between the top edge of the blade and the casing wall. This is achieved by a precisely complementary shape of the elevations and recesses on the top edges of the blades and the casing wall across the entire length of the meridian contour.

[0015] Alternative embodiments of the turbo compressor are characterized in that the head gap has a first head gap width a in a section adjacent to the intake-side blade edge, a second head gap width b in a section adjacent to the discharge-side blade edge and a radial head gap length c extending between the stop surfaces in the region of the recess and the elevation, wherein it is provided that the head gap widths or head gap length a <c <b (erste variante) oder a>c>b (second variant). In the first variant, the flow cross-section of the tip gap decreases from the axial intake side to the radial discharge side; in the second variant, it increases. This is implemented as a design variant by means of enlarged recesses provided on one side, i.e., only at the upper blade edges or only on the casing wall, or alternatively, by enlarged elevations.

[0016] Another design includes turbocompressors in which both the upper edges of the blades and the casing wall each have several recesses and several elevations along their respective meridional contours, which interact locally so that the tip gap in the area of ​​the recesses and elevations defines a repeating Z-shaped profile in the meridional plane. In other words, the special discontinuous contour can be repeated along the meridional length of the blades.

[0017] In a further development, the turbo compressor is characterized in that the compressor wheel has blades with different axial extensions, which are arranged alternately in the circumferential direction and are curved in the circumferential direction. The blades with shorter axial extensions are preferably arranged as intermediate blades (also called splitter blades) between blades with a larger axial extension.

[0018] In a special design, the blades with a larger axial extension overlap the intermediate blades in an intake-side axial plan view or projection of the compressor wheel. This is achieved by the curved shape of the blades with a larger axial extension, which continues in an area of ​​the circumference of the compressor wheel where the intermediate blades do not extend.

[0019] A further design variant of the turbo compressor provides that at least or exclusively the blades with a greater axial extension have at least one recess and at least one elevation along their respective meridional contour. This means that compressor wheels with intermediate blades are also included, whose meridional contour is continuous and without recesses or elevations.

[0020] Other advantageous developments of the invention are characterized in the subclaims or are presented in more detail below, together with the description of the preferred embodiment of the invention, with reference to the figures. They show: Fig. 1 shows a turbocompressor sectioned in the meridian plane according to a first embodiment; Fig. 2 shows the turbocompressor according to Figure 1 ; Fig. 3 a detailed view of the head gap of the turbo compressor according to Figures 1 and 2 ; Fig. 4 the compressor wheel of the turbo compressor according to Figures 1 and 2 in a perspective view Fig. 5 an alternative embodiment of a compressor wheel in a perspective view.

[0021] In the Figures 1 and 2 A section of a turbocompressor 1 is shown schematically, cut in the meridian plane. Only the areas of the turbocompressor relevant to the invention are shown; otherwise, the person skilled in the art will use the structure known from the prior art.

[0022] The turbo compressor 1 comprises the compressor housing 2 and the compressor wheel 4 with the blades 5 arranged distributed in the circumferential direction. The compressor wheel is also in Figure 4 Driven by a motor (not shown), the compressor wheel 4 rotates around the rotation axis RA. It sucks in air axially and blows it out radially. A corresponding main flow HS is shown in Figure 2 shown.

[0023] The tip gap 7 is provided between the stationary housing wall 3 of the compressor housing 2 and the upper blade edges of the blades 5, which allows rotation of the compressor wheel 4. The upper blade edges are cover-free, i.e., they are not covered by a cover plate.

[0024] Along their respective meridian contours, both the upper edges of the blades 5 and the casing wall 3 are adapted in such a way that a return flow RS flowing through the head gap 7 (see Figure 2 ) is deflected in the opposite direction and fed back into the main flow HS. For this purpose, a recess 11 and a raised portion 10 are provided on the upper blade edges of the blades 5 opposite the meridian course in the flow direction of the main flow HS from the intake-side leading edge 12 of the compressor wheel 4 to its discharge-side trailing edge 6. In a complementary form, the housing wall 3 is formed with the recess 13 opposite the raised portion 10 of the blade 5 and the raised portion 14 opposite the recess 11 of the blade 5. The discontinuous meridian contour leads to the tip gap 7 defining a Z-shaped course when viewed in a meridian plane, which in the view according to the Fig. 1 and 2 is mirrored.

[0025] The Z-shaped or mirrored Z-shaped course, depending on the side from which the blades 5 are viewed, also results in the casing wall 3 and the blades 5 each having two transverse legs 8 that are drawn in relative to the meridian course, as well as mutually directed stop surfaces 9, 9' for the flow through the head gap 7. In the embodiment shown, the stop surface 9 of the casing wall 3 represents the main obstacle for the return flow RS and directs the return flow RS back into the main flow HS. The stop surfaces 9, 9' are inclined at an angle α relative to a perpendicular to the tangent T of the meridian course of the casing wall 3 or the upper blade edges of the compressor wheel 4 (see Figure 3 ). According to the invention, the angle α lies in a range of ±15°, and in the illustrated embodiment, it is -10°. The Z-shaped profile thus becomes a lightning-like profile with a clear reversal of the stop surface 9 back into the main flow HS and thus improved recirculation of the return flow RS.

[0026] The corresponding design of the housing wall 3 and the upper edges of the blades 5 is described in more detail in Figure 3 shown. The adjustment of the meridian contour with recess 11 and elevation 10 of the blade upper edge compared to the meridian course M' as well as the meridian contour with recess 14 and elevation 13 of the casing wall 3 compared to the meridian course M can be clearly seen. The hatched areas determine the respective size of the deviations from the continuous meridian courses M , M'. In addition, Figure 3 Also shown are the tip gap width a, b determined by the distance between the upper edge of the blade 5 and the housing wall 3, as well as the tip gap length c between the stop surfaces 9, 9', where in the illustrated embodiment a>c>b. The elevation 14 of the housing wall 3 and the recess 11 of the upper edge of the blade, as well as the elevation 10 of the upper edge of the blade and the recess 13 of the housing wall 3 are each equal, so that the tip gap widths a and b remain constant.

[0027] In Figure 1 Furthermore, the meridian length L of the compressor wheel 4 is shown from its intake-side leading edge 12 to its exhaust-side trailing edge 6, which lies between the values ​​0 <L<1 festgelegt wird, um zu bestimmen, dass der Z-förmige Verlauf gebildet durch die Rücksprunge 11, 13 und Erhöhungen 10, 14 in dem gezeigten Ausführungsbeispiel bei 0,47 liegt. Gemessen wird bei der mittleren Kopfspaltlänge c.

[0028] The Figures 4 and 5 show different embodiments of compressor wheels 4, wherein the compressor wheels 4 each have blades 5 with different axial extensions, which are arranged alternately in the circumferential direction and are curved in the circumferential direction. The blades with shorter axial extension or meridional extension are arranged as intermediate blades 5' between the blades 5 with greater axial extension or meridional extension. The curved shape of the longer blades 5 results in the intermediate blades 5' being covered in axial projection. In the embodiments shown according to the Figures 4 and 5 Both the blades 5 and the intermediate blades 5' are designed with the elevation 10 and recess 11, but only the blades 5 can be shaped accordingly and the intermediate blades 5' can have a continuous meridian contour. The design of the compressor wheel 4 according to Figure 5 differs in that the discontinuous meridian contour of the blade upper edges is formed multiple times along the meridian. The casing wall 3 is then shaped accordingly in a complementary manner.

[0029] The entire disclosure applies to both radial compressor wheels and diagonal compressor wheels.

Claims

1. Turbocompressor (1) with a compressor housing (2) and a compressor wheel (4) with blades (5), wherein the compressor wheel (4) is mounted rotatably relative to the compressor housing (2) and is spaced apart by a head gap (7) between cover-free blade upper edges of the blades (5) and a compressor wall (3) of the compressor housing (2) facing the blade upper edges, wherein both the blade upper edges of the blades (5) and the housing wall (3) each have at least one recess (11, 13) and at least one elevation (10, 14) over their respective meridian contour, which interact locally, so that the head gap (7) in the area of the recesses (11, 13) and the elevations (10, 14) defines a Z-shaped course when viewed in a meridian plane, wherein the housing wall (3) and the blades (5) each have stop surfaces (9, 9') directed towards one another for a flow through the head gap (7), wherein the stop surfaces (9, 9') run parallel at an angle α=±15° with respect to a perpendicular to a tangent (T) of the meridian course of the housing wall (3) and / or the blade upper edges of the compressor wheel (4).

2. Turbocompressor according to claim 1, characterised in that a meridian length (L) of the compressor wheel from its intake-side leading edge (12) to its exhaust-side trailing edge (6) is determined between the values 0<L<1 and the at least one recess and the at least one elevation are formed in a range 0.3<L<0.7, in particular 0.4<L<0.5.

3. Turbocompressor according to any one of the preceding claims, characterised in that the head gap (7) has a constant head gap width, wherein the head gap width is determined by the distance between the upper edge of the blade and the housing wall.

4. Turbocompressor according to one of the preceding claims 1 or 2, characterised in that the head gap (7) has a first head gap width (a) in a section adjacent to the intake-side blade edge (12), a second head gap width (b) in a section adjacent to the exhaust-side blade edge (6) and a radial head gap length (c) extending between the stop surfaces in the region of the recess and the elevation, where: a<c<b.

5. Turbocompressor according to one of the preceding claims 1 or 2, characterised in that the head gap (7) has a first head gap width (a) in a section adjacent to the intake-side blade edge (12), a second head gap width (b) in a section adjacent to the exhaust-side blade edge (6) and a radial head gap length (c) extending between the stop surfaces in the region of the recess and the elevation, where: a>c>b.

6. Turbocompressor according to any one of the preceding claims, characterised in that both the upper edges of the blades (5) and the housing wall (3) each have a plurality of recesses (11, 13) and a plurality of elevations (10, 14) over their respective meridian contour, which each interact locally, so that the head gap (7) determines a repeating Z-shaped course in the region of the recesses and the elevations in the meridian plane.

7. Turbocompressor according to any one of the preceding claims, characterised in that the compressor wheel (4) has blades (5) each with a different axial extent, which are arranged alternately to one another in the circumferential direction and are curved in the circumferential direction.

8. Turbocompressor according to any one of the preceding claims, characterised in that the blades with a smaller axial extent are arranged as intermediate blades (5') between blades (5) with a greater axial extent and the blades (5) with a greater axial extent cover the intermediate blades (5') in an intake-side axial plan view of the compressor wheel (4).

9. Turbocompressor according to any one of the preceding claims, characterised in that at least or exclusively the blades (5) with a larger axial extent over their respective meridian contour have the at least one recess (11) and the at least one elevation (10).