EP3298285B1 - Guide vane for a bladed diffuser of a centrifugal compressor - Google Patents

Description

The invention relates to a guide vane for a diffuser of a centrifugal compressor according to the preamble of patent claim 1.

Such guide vanes for diffusers of centrifugal compressors are already well known from the general state of the art. The radial compressor usually has a receiving region in which a compressor wheel of the centrifugal compressor can be received or, in the finished state of the radial compressor, is accommodated. Furthermore, the radial compressor has a downstream of the receiving region arranged diffuser, which extends, for example, at least substantially in the radial direction. During operation of the centrifugal compressor air is compressed by means of the compressor wheel, which flows off the compressor and flows through the diffuser.

The aforementioned guide vane can be arranged in the diffuser designed, for example, as a radial diffuser, or-in the ready-made state of the radial compressor-is arranged and serves to guide the air flowing through the diffuser. In this case, the guide vane on a skeleton line, wherein the guide vane may be formed, for example, as a wing profile.

Usually, a plurality of guide vanes are arranged in the diffuser, which are arranged in the circumferential direction of the compressor wheel over its circumference successively. Through the plurality of vanes, a guide is formed, which is also referred to as Nachleitgitter. The guide is namely arranged in the flow direction of the air downstream of the compressor wheel or the receiving area and provides advantageous flow conditions in the diffuser.

Further, the WO 2006/053579 A1 a turbocharger with a turbine, which comprises a turbine wheel and a guide grid arranged upstream of the turbine wheel with a plurality of guide vanes.

Conventional guide vanes, which are used in conventional centrifugal compressors and are arranged or can be arranged in the diffuser, have blade geometries, which lead to unfavorable and thus unfavorable flow conditions in the diffuser. Such a blade geometry is, for example, a geometry in the form of a profile drop, which leads to a strong constriction of a flow channel through which air can flow, so that only a small maximum mass flow of the air can flow through the flow channel. Another blade geometry is the so-called NACA profile, which is optimized for aircraft wings, but ensures high losses in the diffuser. Another blade geometry is the so-called wedge blade, which leads to high losses due to a sudden increase in channel diameter at the blade end. If the respective guide blade is designed, for example, as a straight blade of constant thickness, this leads to an undesirably strong delay in the flow of the air, resulting in high losses. Another blade geometry is the so-called circular arc geometry with constant thickness. In this case, there is an insufficiently high number of free geometry parameters and this blade geometry leads to strong delays, in particular in the middle part of the guide blade.

Object of the present invention is therefore to develop a guide vane of the type mentioned in such a way that particularly advantageous flow conditions can be realized in the diffuser.

This object is achieved by a guide blade having the features of patent claim 1. Advantageous embodiments with expedient developments of the invention are specified in the remaining claims.

In order to further develop a guide vane of the type specified in the preamble of patent claim 1 in such a way that particularly advantageous flow conditions can be realized in the diffuser, it is provided according to the invention that the entire skeleton line, ie along its entire extent, is elliptical. Because of the engagement a vane having an elliptical skeleton line, an at least nearly uniform deceleration in a flow channel at least partially delimited by the vane can be realized without excessive constriction at the leading edge of the vane. In addition, the use of a vane with an elliptical skeleton line provides a high degree of free geometry parameters.

The invention also includes a radial compressor, in particular for an exhaust gas turbocharger of an internal combustion engine, having a receiving area for a compressor wheel of the centrifugal compressor, with a diffuser arranged downstream of the receiving area, and with at least one guide vane according to the invention arranged in the diffuser. The diffuser itself is a flow channel through which air can pass, the air being compressed by means of the compressor wheel, flowing off the compressor wheel and flowing through the diffuser. Because the guide vane has an at least substantially elliptical skeleton line, particularly advantageous flow conditions can be realized in the diffuser without undue disadvantages, so that a particularly efficient operation of the radial compressor can be realized.

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the figure description and / or alone in the single figure can be used not only in the respectively indicated combination but also in other combinations or alone, without the frame to leave the invention.

The drawing shows in the single figure a schematic sectional view of a guide vane for a downstream of a receiving area for a compressor wheel arranged diffuser of a centrifugal compressor, with a skeleton line, which is elliptical in at least a partial region.

The FIGURE shows a schematic sectional view of a generally designated 10 guide vane for a downstream of a receiving area for a compressor wheel arranged diffuser of a centrifugal compressor. The radial compressor is preferably part of an exhaust gas turbocharger, with which an example designed as a reciprocating internal combustion engine internal combustion engine of a motor vehicle Is provided. In this case, the internal combustion engine is designed to drive off the motor vehicle and comprises a exhaust tract of the internal combustion engine through which can flow exhaust tract and an air-flowable intake tract. By means of the intake tract, the air flowing through the intake tract is guided into at least one combustion chamber, in particular cylinder, of the internal combustion engine.

The exhaust gas turbocharger has a turbine, which is arranged in the exhaust tract and can be driven by the exhaust gas. For this purpose, the turbine comprises a turbine housing and a turbine wheel arranged in the turbine housing, which can be driven by the exhaust gas. The turbine wheel is rotatable about an axis of rotation relative to the turbine housing and part of a rotor of the exhaust gas turbocharger. The rotor further comprises the aforementioned compressor wheel and a shaft to which the turbine wheel and the compressor are rotatably connected. As a result, the compressor wheel can be driven by the turbine wheel via the shaft, so that - during the operation of the radial compressor - air is compressed by means of the compressor wheel. As a result, energy contained in the exhaust gas can be used to compress the air.

The centrifugal compressor is arranged in the intake tract and comprises a compressor housing in which the compressor wheel is arranged. In this case, the compressor wheel or the rotor is rotatable about said rotation axis relative to the compressor housing. Said receiving region, in which the compressor wheel is arranged, is limited by the compressor housing.

The radial compressor further comprises the aforementioned diffuser, which is arranged in the flow direction of the air through the radial compressor downstream of the receiving region and thus of the turbine wheel. The diffuser is a channel which can be flowed through by the air compressed by the compressor wheel and flowing away from the compressor wheel or through which flows during operation of the centrifugal compressor. Preferably, the diffuser is designed as a radial diffuser, wherein the diffuser extends at least substantially in the radial direction.

The centrifugal compressor further comprises a guide, which is also referred to as Nachleitgitter. The guide device comprises a plurality of guide vanes arranged in the diffuser and thus downstream of the receiving region or the compressor wheel, of which the guide vane designated by 10 is shown in the FIG. The vanes arranged in the diffuser serve to guide the air flowing through the diffuser so that advantageous flow conditions are realized in the diffuser can be. The previous and following versions of the guide vane 10 can be readily transferred to the other vanes of the secondary lattice.

From the Fig. It can be seen that the vane 10 has a skeleton line X. In order to be able to realize particularly advantageous flow conditions in the diffuser, the entire skeleton line X is elliptical in shape. This means that the skeleton line X is elliptical, that is, formed as part of an ellipse along its entire extension.

The figure also shows a diagram 12, which is used as an auxiliary diagram for constructing the skeleton line X. It can be seen particularly clearly from the figure that the skeleton line X of the guide vane 10 is constructed as an ellipse with an elliptical thickening over the length of the chord C of the guide vane 10. In this case, the guide blade 10 has a blade inlet 14, via which the guide blade 10 is impinged by the air during operation of the radial compressor. Furthermore, the guide vane 10 has a vane outlet 16, via which the air flows off the vane 10. The blade inlet 14 and the blade outlet 16 intersect a common straight line and thus define the chord C.

Since the skeleton line X is formed elliptical, the skeleton line X is also referred to below as an ellipse. The ellipse has exactly two intersecting angles with the chord C, wherein the intersection angle of the ellipse with the chord C of the guide vane 10 respectively, that is individually considered, less than 45 ° and together, that is, in sum, always less than 80 °.

With f _{r, 3} , an entry _{radius of} the guide vane 10 is designated, wherein f _{r, 4 is} an exit _{radius of} the vane 10 is designated. The entry _radius f _{r, 3} is also illustrated by r ₃ in the figure, wherein the exit _radius f _{r, 4 is} also illustrated by r ₄ . Furthermore, in the figure, a radius r _{2 can be seen} . In addition, the guide vane 10 has an entry angle α _{b, 3} and an exit angle α _{b, 4} , wherein the guide vane 10, in particular its inlet area, in which the vane 10 is flown by air, the entry angle α _{b, 3} encloses with the radial , Further, the guide vane 10, in particular its outlet region, over which the guide vane 10 is flowed away from the air, the exit angle α _{b, 4} with the radial includes, said radials in the Fig. Each with r is illustrated.

Furthermore, the guide vane 10 has a maximum thickness d _b and a so-called thickness reserve f _b . The length of the chord C is also denoted by l _b . In addition, it has been found to be particularly advantageous if the center M of the ellipse with respect to the chord axis of the vane 10 is not more than half the length l _{b of} the chord C from the center S of the chord C.

By means of the embodiment of the guide vane 10 illustrated in the FIGURE, an at least substantially uniform deceleration without excessive constriction on the vane leading edge can be realized in a flow channel which is at least partially traversed by the vane 10 and can be traversed by the air Measurements of free geometry parameters can be displayed. As a result, it is possible to create a tracking grating design with an elliptical characteristic for the diffuser, which is preferably designed as a radial diffuser, as a result of which particularly advantageous flow conditions in the diffuser can be represented.

LIST OF REFERENCE NUMBERS

10

vane

12

diagram

14

vane inlet

16

blade outlet

C

tendon

S

Focus

M

Focus

X

skeleton line

d _b

maximum thickness

f _b

Dick reserve

f _{r, 3}

inlet radius

for _{, 4}

exit radius

l _b

length

r ₂

radius

r ₃

Eintritssradius

r ₄

exit radius

r

radial

α _{b, 3}

entry angle

α _{b, 4}

exit angle

Claims (5)

1. Guide vane (10) for a diffuser of a of a centrifugal compressor, which diffuser is located downstream of a reception region for a compressor impeller, with a skeleton line (X),
   characterised in that
   the whole skeleton line (X) is designed to be elliptical.
2. Guide vane (10) according to any of the preceding claims,
   characterised in that
   the angle of intersection of the ellipse with the chord (C) of the guide vane (10) is less than 45 degrees and in sum less than 80 degrees.
3. Guide vane (10) according to any of the preceding claims,
   characterised in that
   the distance of the centre (M) of the ellipse from the centre (S) of the chord (C) of the guide vane (10) relative to the chord axis is no more than half the length (l_b) of the chord (C).
4. Centrifugal compressor, in particular for a turbocharger of an internal combustion engine, with a reception region for a compressor impeller of the centrifugal compressor, with a diffuser located downstream of the reception region and with at least one guide vane (10) according to any of the preceding claims.
5. Turbocharger for an internal combustion engine, in particular of a motor vehicle, with a centrifugal compressor according to claim 4.

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