Blades with an S-shaped profile in the flow direction for a radially structured impeller

Abstract

The present invention relates to an impeller (14) for a turbine (10), in particular a radial turbine. The impeller (14) has a plurality of blades (16), which are received on the circumference of the impeller (14) at intervals from one another. The blades (16) are configured to have a radially extending S-shaped profile (26).

Description

Field of the Invention

[0001] The present invention relates to a blade having an S-shaped profile in the flow direction for an impeller in a radial configuration, which blade is used in a turbine. Background Art

[0002] In the context of current developments, saving energy and thus reducing CO 2 emissions is a declared goal in all fields. In the European Union, a large part of the total energy consumption is caused by turbines, mainly pumps and ventilators. Due to increasingly strict EU regulations, pump and ventilator manufacturers should continuously improve the efficiency of their turbines (EuP Directive). By increasing the efficiency of the turbine, the energy that must be provided to drive the machine can be converted into more available fluid energy. The non-usable and irreversible part of the energy is reduced.

[0003] DE 10 2010 021 220 A1 discloses a rotor and a turbine. According to this solution, the rotor includes a rotor body and a plurality of blades, which blades are arranged along the circumference of the rotor body. At least one first rope is provided to receive centrifugal force, and the first rope extends in the circumferential direction with respect to the rotation axis of the rotor. On the radially outer side, a shroud is connected to the blade, and the shroud has at least one first rope to receive the centrifugal force acting on the shroud. The shroud has a cavity or a channel, and at least one first rope is arranged in the cavity or the channel. The aim of this solution is to receive the centrifugal force generated during rotation by means of ropes instead of single fibers. The use of ropes can provide a certain elasticity so as to be able to withstand large impacts. In addition, the use of ropes also provides a cost-effective solution. By receiving at least a part of the acting centrifugal force by at least one rope, the possibility of reducing the material thickness of the components of the rotor (for example, the blade or the rotor body) is opened up.

[0004] CH 698 109 B1 relates to a turbine blade. The turbine blade includes a blade wing, and the blade wing longitudinal extension of the blade wing extends from the blade root to the blade tip. The turbine blade has an installation radial direction, an installation circumferential direction, and an installation axial direction. In addition, it also has a stacking line. The inclination angle is defined as the angle that the projection of the stacking line on the plane spanned by the installation circumferential direction and the installation radial direction has with the installation radial direction, wherein the inclination angle varies along the blade wing longitudinal extension.

[0005] DE 10 2014 104 726 A1 relates to a rotor and a fluid turbine having a rotor. The rotor includes a vertical rotation axis and at least two rotor blades. They are arranged at the rotation axis, and at least one rotor blade includes at least one opening having an openable closing element.

[0006] DE 10 2011 080 804 A1 relates to a two-piece impeller for use in compressor stages, turbocompressors, and turbochargers. The impeller is configured as two-piece and is used in the compressor stage of a turbocompressor (especially a radial compressor or an axial compressor). The impeller is formed by a wheel member on the inflow side and a wheel member on the outflow side, wherein the wheel member on the outflow side has a first number of blades and the wheel member on the inflow side has a second number of blades, especially a smaller number of blades. The wheel member on the inflow side includes an internal thread for screwing onto the shaft end of a shaft to fasten the impeller to the shaft, wherein the outflow edge of the blades of the wheel member on the inflow side is offset from the inflow edge of the blades of the wheel member on the outflow side.

[0007] In turbines of radial construction, such as in radial fans, the prior art is to use simple arcuate blades or blades with a logarithmic profile. Individually, profiled blades are also used, however, profiled blades are mainly used to increase the stiffness of the impeller. The disadvantages of blades with an S-bend may be, for example: for high-load impellers, there is a relatively high mechanical load on the cover plate and the support plate, and this mechanical load must be compensated for by the structure. In addition, due to the inflection point in the blade geometry, the production cost is slightly higher compared to arcuate blades. The blades are overall longer and thus heavier, which requires more material input. Since such turbines usually operate continuously for many years, the cost savings achieved through energy conservation far exceed the additional cost of materials and the increased construction cost.

[0008] Advantages of the Invention

[0009] The present invention is based on the following object: to improve the efficiency of a turbine, especially a radial turbine, so that the energy that must be provided to drive a machine can be converted into more useful fluid energy. According to the present invention, it is proposed that a plurality of blades are provided on a turbine, especially a radial turbine, and the blades are received at intervals on the circumference of the impeller, and the blades are configured to have an S-shaped profile extending radially. By the solution proposed according to the present invention, it is achieved that the expansion of the flow channel in the rotor (i.e., the impeller) is reduced or achieved more gently, and in this way, the alternating region of the fluid flow that is otherwise common on the suction side of the blades is reduced. This in turn leads to a reduction in the "trailing indentations (Nachlaufdellen)" in the outflow section of the impeller, thereby reducing the mixing losses in the subsequent annular diffuser or in the spiral housing. Compared with traditional configurations, especially compared with simple arcuate blades or logarithmic blades, this in turn allows an increase in efficiency, or alternatively allows the efficiency to be maintained at a larger pressure difference and at the same time with an adapted discharge angle.

[0010] In an advantageous embodiment of the solution according to the invention, the S-shaped profile can include a first arc segment and a second arc segment, and the first arc segment and the second arc segment transition tangentially into each other at the inflection point. The S-shaped profile of the blade according to the invention can be manufactured in the following way: First, an arc piece, a straight extension part connected thereto, and then another arc piece are joined to each other. There is also the possibility of showing the S-shaped profile by joining three arc pieces to each other. Importantly, by implementing a substantially S-shaped profile of the blade profile, the channel expansion between two adjacent blade wings is reduced, and in an ideal case, the channel expansion is completely eliminated.

[0011] Advantageously, the first and second arc segments can be configured with arc radii r 1 、r 2 , and the arc radii r 1 、r 2 can be the same as or different from each other. The joining of the two arc segments shows a very cost-effective and easily achievable configuration possibility of the S-shaped profile.

[0012] The blades of the impeller extend from the inlet edge to the outlet edge. Its geometry is clearly defined by the construction parameters listed below:

[0013] - The radius r E of the blade inlet edge,

[0014] - The inlet angle β S,E ,

[0015] - The radius r 1 、r 2 of the first or second arc segment,

[0016] - The radius r W of the inflection point,

[0017] - The outlet angle β S,A , and

[0018] - The radius R A of the blade outlet edge.

[0019] Regarding the inlet angle β S,E at the inlet edge of the blade, the achievable efficiency of the turbine and the flow with a small amount of eddy current in the turbine housing are achieved. The inlet angle in turn depends on the design point, i.e., the optimal operating point of the fan (i.e., the turbine).

[0020] According to the required pressure increase and the design of the turbine, the outlet angle β S,A at the outlet edge of the blade can vary between 30° and 120°.

[0021] In the impeller according to the invention, the first arc segment of the S-shaped profile is configured to be overbent, the first arc segment extending from the hub, while the second arc segment of the S-shaped profile is configured to be bent in the opposite direction to the first arc segment and to define the discharge angle β S,A , and the second arc segment is connected to the first arc segment. In the present case, "overbent" means that, for the case where no S-bend is provided in the blade profile, the curvature is greater than the curvature necessary to achieve the desired discharge angle.

[0022] Advantageously, the geometry of the blade (i.e., the S-shaped profile) is configured such that the geometry substantially corresponds to the frame line of the blade of the impeller, thickened by the material thickness.

[0023] Preferably, the impeller according to the invention is used in a turbine, in particular a radial turbine (e.g., a radial flow fan).

[0024] By means of the S-shaped profile according to the invention, it is advantageously possible to reduce or more gently effect the expansion of the flow channel between two adjacent blades at the impeller, and thus in this way to reduce the otherwise common alternating zones of the fluid flow on the suction side of the blade. This results in a reduced "Jet-Wake-Struktur" in the outflow section of the rotor, and significantly fewer mixing losses in the subsequent annular diffuser or in the spiral housing. The "Jet-Wake-Struktur" is generated by the alternating zones within the rotor. In the relative system of the rotor, the velocity is 0 in the alternating zones of the fluid flow, and thus these zones are not traversed. As a result, the entire fluid flow is squeezed by the remaining channel cross-section, and thus the self-regulated velocity there is significantly higher than the velocity when the entire fluid flow traverses the entire channel cross-section. This alternation between velocity = 0 and high velocity causes a "Jet-Wake-Struktur" (jet = beam, wake = still water) to occur immediately behind the rotor.

[0025] Compared to the use of simple circular arc blades (i.e., blade geometries without an S-shaped profile) or the use of logarithmic blades in the conventional construction form, due to the reduced mixing losses, this also results in a higher efficiency of the impeller according to the invention. On the other hand, there is also the possibility that, by additionally increasing the discharge angle β S,A , a greater pressure difference can be achieved with the same efficiency as in the standard configuration. A higher efficiency η means a lower power consumption of the turbine with the same pressure difference and the same volume flow rate, or, on the other hand, a greater pressure difference with the same efficiency and the same volume flow rate. Ultimately, this results in a reduction in emissions and a decrease in CO 2 emissions. Description of the Drawings

[0026] The present invention will be explained below with reference to the drawings.

[0027] The accompanying drawings show:

[0028] Figure 1 A comparison diagram showing a conventional straight - extending blade profile opposite to the S - shaped profile of the blade according to the present invention;

[0029] Figure 2 Shows the basic structural parameters for defining the S - shaped profile of the blade;

[0030] Figure 3 and Figure 4 A comparison diagram showing the alternating regions of the fluid flow on the suction side of the impeller blade with a straight profile and the alternating regions of the fluid flow on the suction side of the impeller blade configured with the S - shaped profile proposed according to the present invention;

[0031] Figure 5 and Figure 6 Shows a comparison diagram of the self - adjusting channel expansion in an impeller with a conventional blade geometry and in an impeller whose blades are provided with the S - shaped profile proposed according to the present invention; and

[0032] Figure 7 and Figure 8 Shows a comparison diagram of the adjusted jet wake structure ("trailing indentation") that appears in the housing of the turbine in terms of the conventional configuration of the blade geometry and in terms of the blade geometry with the S - shaped profile proposed according to the present invention. Detailed Description

[0033] In the illustration according to Figure 1 a conventional blade geometry for an impeller blade and the S - shaped profile proposed according to the present invention are shown in comparison.

[0034] In Figure 1 the turbine, only partially shown in Figure 1 includes a housing 12 (such as a volute housing) and is provided with an impeller 14. The turbine is a radial turbine, such as a radial - flow fan. The impeller 14 (only partially shown in Figure 1It is known that the blade 16 of the traditional structural form has a straight profile 24, while the blades 16, 18 proposed according to the present invention are provided with an S-shaped profile 26. The alternating regions of the fluid flow are denoted by the reference numeral 22, and the alternating regions are respectively located on the suction sides of the blades 16, 18. The suction sides of the blades 16, 18 are denoted by the reference numeral 28. Regarding the rotational direction of the impeller 14, the suction sides 28 are respectively located on the back sides of the blades 16, 18. On the discharge side (i.e., at the ends of the blades 16, 18), a "jet wake structure" denoted by the reference numeral 30 can be recognized. This "jet wake structure" is generated in the rotor through self-regulating alternating regions. In the relative system of the rotor, the velocity of the fluid flow in the alternating regions is 0, so that the fluid flow does not pass through this region. This means that the entire fluid flow passes through the remaining channel cross-section passively, so that the adjusted velocity appearing in the remaining channel cross-section is significantly higher than the velocity when the (jet) fluid flow passes through the entire channel cross-section. This alternation between velocity = 0 and high velocity results in the generation of a "jet wake structure" immediately behind the rotor, where the term "jet" represents a beam and the term "wake" represents "still water".

[0035] From the illustration according to Figure 2 the construction parameters can be learned, and through these construction parameters, the S-shaped profile of the blade proposed according to the present invention can be clearly defined.

[0036] In a schematic and highly simplified manner, Figure 2 the impeller 14 is shown, and the rotational axis of the impeller is identified by the reference numeral 42. The radius r E extends from the rotational axis 42 to the blade inlet edge of the blade 16. Starting from the inlet edge 34, the first arc segment 31 of the S-shaped profile 26 extends with a radius r 1 At the inflection point 33, the first arc segment 31 of the S-shaped profile 26 transitions into another second arc segment 32, and the inflection point is on the corresponding radius r W for the inflection point. Compared with the first arc segment, the second arc segment 32 downstream of the inflection point 33 is reversely bent, and the first arc segment is configured to be over-bent. In the radial direction, that is, when observed from the flow direction, the second arc segment 32 extends from the inflection point 33 to the discharge edge 35 of the blade. The discharge edge 35 of the blade 16 is on the radius r A At the inlet edge 34 of the blade 16, there is an inlet angle β s,E , which depends on the design. At the discharge edge 35 of the S-shaped profile 26, that is, at the end of the second arc segment 32, there is a discharge angle β s,A . This discharge angle is in the angular range of 30° to 120°.

[0037] For the following cases, the construction parameters 40, r E , β S,E , r1 and r 2 and r W and β S,A and r A Define the geometry of the S-shaped profile 26: In the simplest case, this geometry is formed by using two circular arc members (i.e., the first circular arc segment 31 and the second circular arc segment 32).

[0038] Figure 3 and Figure 4 show a comparison diagram of the turbine 10 with an impeller 14 of a conventional construction and the turbine 10 with an impeller having blades 16 with an S-shaped profile 26 according to the present invention. In Figure 3 and Figure 4 the two cases shown, the basic parameters of the impeller (i.e., the inlet angle and the outlet angle, and the inlet width and the outlet width of the channel cross-section) are the same.

[0039] As can be seen from the illustration according to Figure 3 , the straight profiles 24 of the blades 16, 18 result in an alternating zone 50 on the suction side 28 of the blade 16. The self-adjusting alternating zone 50 on the suction side 28 according to the implementation variant of Figure 3 causes relatively large eddy current losses, and these eddy current losses are not conducive to the achievable efficiency.

[0040] Conversely, according to the illustration in Figure 4 , the blades 16 of the impeller 14 are configured with an S-shaped profile 26 according to the present invention. The alternating zone 52 on the suction side 28 of the blade 16, which is significantly smaller compared to the alternating zone 50 according to Figure 3 , results in a significant reduction in the mixing losses in the radial turbine housing.

[0041] Figure 5 and Figure 6 are comparison diagrams of the channel expansion between two blades of the impeller for the conventional construction (i.e., constructed with a straight profile 24) of the blades 16 of the impeller 14, while according to Figure 6 , the blades 16 of the impeller 14 shown there are configured with an S-shaped profile 26 according to the present invention. In the illustration according to Figure 5 , two adjacent blades 16 form a channel expansion 54 with a straight profile 24, while in Figure 6In the comparison position 56, in an implementation variant of the impeller 14, the channel expansion in the impeller having blades 16 in the form of an S-shaped profile 26 is significantly reduced. Through the reduced channel expansion 56, a reduced alternating zone 52 is achieved on the suction side 28 of the blades 16, 18, which is beneficial for the efficiency class and also results in a reduced "jet wake structure" on the outflow side of the impeller 14 (see the above description). This in turn allows for a reduction in mixing losses in the subsequent annular diffuser or in the spiral housing of the turbine (especially a radial turbine).

[0042] It can be learned from the illustrations according to Figure 7 and Figure 8 about the self-regulating "jet wake structure". In Figure 7 it is shown that the "jet wake structure" 58 in the spiral housing of the turbine 10 is relatively obvious, while in the implementation variant according to Figure 8 the jet wake structure is significantly reduced (compare the reference numeral 60), in which the blades 16 of the impeller 14 are constructed with the S-shaped profile 26 proposed according to the present invention. The jet wake structures 58, 60 are basically generated in the following way: In the housing (for example, the spiral housing 12 of the radial turbine 10), there are different flow velocities. If the flow part with a high speed meets the flow part with a low speed, it leads to internal friction of the fluid and thus a deceleration process in which the high-speed fluid flow passes through the low-speed fluid flow, which results in mixing losses. The mixing losses in turn are extremely disadvantageous for the achievable efficiency of the turbine.

[0043] In summary, through the S-shaped profile 26 of the blade 16 proposed according to the present invention, an impeller 14 for a turbine 10 is described, which is characterized by: a reduced channel expansion 56, a reduced alternating zone 52 on the suction side 27 of the blade 16, and a reduced jet wake structure 60 in the housing 12 of the turbine 10.

[0044] The present invention is not limited to the described embodiments. On the contrary, other variations and supplements that are obvious to those skilled in the art are possible within the given scope.

[0045] List of reference numerals

[0046] 10 Turbine

[0047] 12 Housing, spiral housing

[0048] 14 Impeller

[0049] 16 Blade

[0050] 18 Another blade

[0051] 20 Gap, flow channel

[0052] 22 Alternating region of eddy current / flow

[0053] 24 Straight profile

[0054] 26 S-shaped profile

[0055] 28 Suction side

[0056] 30 Jet wake structure

[0057] 31 First circular arc segment

[0058] 32 Second circular arc segment

[0059] 33 Inflection point

[0060] 34 Inlet edge of the blade

[0061] 35 Outlet edge of the blade

[0062] 40 Structural parameters

[0063] r E Inlet edge radius of the blade

[0064] β s,E Inlet angle

[0065] r 1,2 Circular arc radius

[0066] r w Inflection point radius

[0067] β s,A Outlet angle

[0068] r A Outlet edge radius of the blade

[0069] 42 Axis of rotation

[0070] 50 Alternating region on the suction side 28

[0071] 52 Reduced alternating region on the suction side 28

[0072] 54 Channel expansion

[0073] 56 Reduced channel expansion

[0074] 58 Apparent jet wake structure

[0075] 60 Reduced jet wake structure

Claims

1. An impeller (14) for a radial fan (10), the impeller having a plurality of blades (16) which are received at intervals from one another on the circumference of the impeller (14). Characterized in that The blade (16) is configured to have a radially extending S-shaped profile (26), the S-shaped profile (26) including a first arc segment (31) and a second arc segment (32), the first and second arc segments transitioning tangentially into each other at an inflection point (33) of the S-shaped profile. The S-shaped profile (26) of the blade (16) substantially corresponds to its frame line and is thickened by material thickness. The first and second arc segments (31, 32) are configured with arc radii r 1 , r 2 such that the arc radii r 1 , r 2 are the same as or different from each other, resulting in a reduced jet wake structure on the outflow side of the impeller.

2. The impeller (14) according to claim 1, Characterized in that the blades (16) are delimited by an inlet edge (34) and an outlet edge (35).

3. The impeller (14) according to the preceding claim 1 or 2, Characterized in that the S-shaped profile (26) of the blades (16) is defined by the construction parameters (40) listed below: - the radius r of the leading edge (34) of the blade (16) E , - Entry angle β S,E , - The radius r of the first or second arc segment (31, 32) 1 , r 2 , -Radius r of the inflection point (33) W , - Discharge angle β S,A , - The radius r of the discharge edge A .

4. The impeller (14) according to the preceding claim 3, Characterized in that At the discharge edge (35) of the blade (16), the discharge angle β S,A is between 30° and 120°.

5. The impeller (14) according to the preceding claim 1 or 2, Characterized in that the first arc segment (31) of the S-shaped profile (26) is configured to be overbent.

6. The impeller (14) according to the preceding claim 3, Characterized in that the first arc segment (31) of the S-shaped profile (26) is configured to be overbent.

7. The impeller (14) according to the preceding claim 4, Characterized in that the first arc segment (31) of the S-shaped profile (26) is configured to be overbent.

8. The impeller (14) according to the preceding claim 3, Characterized in that The second arc segment (32) is configured to bend in a direction opposite to that of the first arc segment (31) and define the discharge angle β S,A .

9. The impeller (14) according to the preceding claim 4, Characterized in that The second arc segment (32) is configured to bend in a direction opposite to that of the first arc segment (31) and define the discharge angle β S,A .

10. The impeller (14) according to the preceding claim 6, Characterized in that The second arc segment (32) is configured to bend in a direction opposite to that of the first arc segment (31) and define the discharge angle β S,A .

11. The impeller (14) according to the preceding claim 7, Characterized in that The second arc segment (32) is configured to bend in a direction opposite to that of the first arc segment (31) and defines the discharge angle β S,A .

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