EP2275643B1 - Engine blade with excess front edge loading - Google Patents

Description

The invention relates to a fluid power machine comprising an engine blade with excessive leading edge load.

The aerodynamic load capacity and efficiency of fluid flow machines, such as fans, compressors, pumps, and fans, is limited particularly by the growth and separation of boundary layers in the area of rotor and stator radial gaps and fixed blade ends near the annular channel walls. The state of the art provides only limited solutions to this fundamental problem. The general idea of boundary effect by changing the skeleton line type along the blade height is included in the prior art, but the known solutions, especially for the flow conditions at a blade end with radial gap, are not sufficiently targeted.

In particular, the invention relates to a fluid flow machine with a blade according to the preamble of claim 1. The blading in question is provided within a main flow path, bounded on the outside by a housing and internally bounded by a hub. While a rotor comprises a plurality of rotor blades attached to a rotating shaft and emits energy to the working fluid, a stator consists of a plurality of fixed, mostly in the housing mounted stator blades.

On the one hand, the fluid flow machine comprises a rotor with a fixed connection to a rotating hub and a free blade end with a gap on the housing. In an analogous manner, the fluid flow machine alternatively comprises a stator which has a fixed connection to the edge on the housing side and has a free blade end with a gap to the hub on the hub side.

The present invention relates to fluid flow machines such as fans, compressors, pumps and fans in axial, semi-axial or also radial design. The working medium (fluid) can be gaseous or liquid. The following is known from the prior art:
The Fig. 1 1 shows, on the left side, a schematic representation of two blade configurations according to the prior art in the meridian plane formed by the radial direction r and the axial direction x. It is a rotor blade row 4 with a gap on the housing 1 (top), wherein the housing 1 is or in special cases also rotates and the blade row rotates about the machine axis 3. It is also a row of stator blades 5 with a gap on the hub 2 (bottom), wherein the hub 2 rotates about the machine axis 3 or, in special cases, also rests and the row of blades 5 stands. According to the prior art, the blade profile cut directly on the running gap of a rotor 4 or stator 5 is designed such that the profile load and thus the profile curvature in the region of the leading edge does not exceed a certain level, because conventional design rules based on considerations of the nature of two-dimensional flows around profiles recommend this.

The right side of the Fig. 1 shows different, the prior art corresponding distributions of the skeleton line curvature in the profile section directly on the running gap, shown as a relative curvature α * over the related run length s * (for definitions see Fig. 3 ). Characteristic for all vault distributions is that with a related run length of s * = 0.1 by far not values of the relative curvature of α *> = 0.35 or even α *> = 0.50 or α *> = 0.65 be provided. As a result, an extreme leading edge load is deliberately avoided. This category includes the so-called CDA (controlled diffusion aerofoils) US 4431376 A , From an aerodynamic point of view, the CDA aims for a moderate profile frontload.

It is disadvantageous in the prior art that the corresponding blade shapes are often deliberately designed with little complexity with respect to the skeleton line shape. In the case of strong run gap leakage flows, there is a lack of excessive profile camber in the leading edge region of the airfoil sections in the vicinity of the air gap to adequately combine a conventional skeleton line curvature distribution favorable in the airfoil region with a skeleton line curvature distribution more favorable to the edge regions.

Furthermore, from the DE 10 2005 042 115 A1 a turbomachine according to the preamble of claim 1.

The present invention has for its object to provide a fluid flow machine of the type mentioned, which while avoiding the disadvantages of In the prior art, a very effective influencing of the edge flow is achieved by an excessive skeleton curve curvature in the region of the front edge of the blade profile cuts located near the running gap.

According to the invention the object is achieved by the combination of features of claim 1, the dependent claims show further advantageous embodiments of the invention.

Thus, according to the present invention, a blade of a fluid flow machine is provided with a skeleton line curvature distribution at least within the 5% of the main flow path width adjacent the gap, which at an averaged run length of s * = 0.1, exaggerates the relative skeleton line curvature of at least α * = 0.35 having.

As can be seen in particular from the Fig. 4c (see description below), a very high rise in the flow deflection is provided at the front of the blade.

The invention can also be represented as follows:
A fluid power machine comprising a blade disposed in a main flow path bounded by a hub and a housing, wherein a gap is provided between an end of the blade and the main flow path boundary, hub or housing, and thus a free blade end is formed, wherein in at least one blade profile streamline section in the area between the gap and one

Blade section at a distance of 30% of the main flow path width W from the gap is provided a skeleton line curvature distribution having an excessive value of the relative skeleton line curvature of at least α * = 0.35 with a related run length of s * = 0.1, where s * on the Represents the total run length of the profile skeleton line-related local run length and α * is formed as the angle change of the skeleton line relative to the total curvature of the skeleton line from the leading edge to a related run length s *, the skeletal line curvature distribution in this representation at the leading edge point V (s * = 0, α * = 0) starts and ends in the trailing edge point H (s * = 1, α * = 1), wherein in particular at least directly at the gap a skeleton line curvature distribution is provided, which with a related run length of s * = 0.1 an excessive value of relative skeleton line curvature of at least α * = 0.35,
and at least within the 5% of the main flow path width adjacent to the gap, there is provided a skeleton line curvature distribution having an excessive relative skeletal line curvature value of at least α * = 0.35 for a related run length of s * = 0.1,
wherein, given a related run length of s * = 0.1, an excessive value of the relative skeleton line curvature of at least α * = 0.50 is preferably provided,
wherein preferably the skeleton line curvature distribution starts with high gradients in the leading edge point V and, in the further course, approaches the related run length s * = 0.1 with decreasing gradient,
preferably the skeleton line curvature distribution continues from the related run length s * = 0.1 in the direction of the trailing edge point H, kink-free and with decreasing or constant gradient to the trailing edge point H, the point of greatest curvature of the skeleton line curvature distribution in the range 0 <= s * < = 0.2 is provided
wherein advantageously the skeleton line curvature distribution of the related run length s * = 0.1 out in the direction of the trailing edge point H going kink-free initially with decreasing gradient continues and from a point T, in which the curvature changes its sign, for at least a portion of the range 0.1 <= s * <= 1 has again rising gradients,
more preferably, the skeleton line curvature distribution has only a single curvature sign change and thus shows an S-shaped course,
and / or that the point T of the first curvature sign change is provided in the range 0.35 <= s * <= 0.65,
furthermore preferably the skeletal line curvature distribution runs in at least part of the range 0.1 <= s * <= 1 at constant values of the relative skeleton curve curvature α *,
and / or the skeleton line curvature distribution with a related run length of s * = 0.9, a value of the relative skeleton line curvature of α * <α * (s * = 0.1) + 0.75 (1-α * (s * = 0, 1)),
and / or the skeleton line curvature distribution curved, partially curved or sectionally rectilinear and in this way between the leading edge point V and the trailing edge point H has any number of kinks,
more preferably, with a related run length of s * = 0.1, an excessive value of the relative skeleton line curvature of at least α * = 0.65 is provided,
more preferably with a related run length of s * = 0.1 an excessive value of the relative skeleton line curvature of at least α * = 1.0 is provided,
and / or in at least a part of the run length of 0.1 <s * <1 values of the relative skeleton line curvature of α *> 1 are provided.

Fig.1:

eine schematische Darstellung zum Stand der Technik,

Fig.2:

die Definition von Meridianstromlinien und Stromlinienprofilschnitten,

Fig.3:

die Definition der Skelettlinie eines Stromlinienprofilschnitts,

Fig.4a:

erfindungsgemäße Lösungen,

Fig.4b:

weitere erfindungsgemäße Lösungen,

Fig.4c:

weitere erfindungsgemäße Lösungen.

In the following the invention will be described by means of embodiments in conjunction with the figures. Showing:

Fig.1:

a schematic representation of the prior art,

Figure 2:

the definition of meridian streamlines and streamline profile sections,

Figure 3:

the definition of the skeleton line of a streamline profile section,

4a:

solutions according to the invention,

4b:

further solutions according to the invention,

4c:

further solutions according to the invention.

The Fig.2 gives a precise definition of the meridional flow lines and the streamline profile sections. The mean meridional flow line 7 is formed by the geometric center of an annular channel 6. If one establishes a normal at each location of the middle streamline 7, one obtains the course of the ring channel width W along the flow path and, on the other hand, a number of normals with whose help further meridional flow lines result with the same relative subdivision in the direction of the channel height. The intersection of a meridional streamline with a blade results in a streamline profile intersection.

The respective skeleton line type for a streamline profile intersection is defined in relative representation by means of the relative curvature α * and the related run length s *, see Figure 3 , The figure shows a streamline profile section of the blade on a meridian flow surface (um plane).

For this purpose, the inclination angle α _p and the run length s _{P covered} up to this point are determined in all points of the skeleton line. As reference values, the inclination angles at the leading and trailing edges α ₁ and α ₂ as well as the total running length of the skeleton line S are used. The following applies: $$\begin{array}{cc}\mathrm{\alpha }*=\frac{{\mathrm{\alpha }}_1-{\mathrm{\alpha }}_{\mathrm{P}}}{{\mathrm{\alpha }}_1-{\mathrm{\alpha }}_2}& \mathrm{S}*=\frac{{\mathrm{s}}_{\mathrm{P}}}{\mathrm{s}}\end{array}$$

The Fig. 4a shows a family of inventive crevices near the profile skeleton curves. They are characterized in that the relative skeleton curve curvature α * always has values greater than or equal to 0.35 for related run lengths of s *> 0.1.

According to the invention, it is further advantageous if the relative skeleton curve curvature α * always has values equal to or greater than 0.50 for related run lengths of s *> 0.1. In special cases, it may even be favorable according to the invention if the relative skeleton curve curvature α * assumes the value 0.65 or even 1.0 from a related run length of s * = 0.1.

The top in Fig. 4a The distribution shown shows the special case according to the invention of a change of the skeleton curve curvature sign. In this illustrated case, the skeleton line is convexly curved towards the profile suction side in a part of the run length s * and concave in a lower part of the run length s *, as is the case if values of α *> 1 at least in part of the run length s * are provided.

The value of α * present at s * = 0.1 is hereinafter referred to as α * _B , ie α * _B = α * (s * = 0.1). In an analogous manner, the value of α * present at s * = 0.9 is also denoted by α * _C , ie α * _C = α * (s * = 0.9). The corresponding points on the skeleton line curvature distribution are called B and C, see Fig. 4c ,

In accordance with the invention, there is thus a deliberate departure from the solution principles known from the prior art. According to the invention, the excessive leakage of the profile leading edge region in the vicinity of the running gap influences the leakage flows occurring at the running gap. This is achieved according to the invention by values of the relative skeleton curve curvature α * of greater than or equal to 0.35 or even greater than 0.5 or in special cases greater than or equal to 0.65 or in extreme cases greater than 1.0 already at a relative run length of s * = 0.1.

Skeleton line curvature distributions according to the invention can be curved, sectionally curved or sectionally rectilinear, and between their starting point V (s * = 0, α * = 0) at the leading edge and their end point H (s * = 1, α * = 1) at the trailing edge have any number of kinks, as long as they the inventive basic criterion α * _B = α * (s * = 0.1)> = 0.35 or α * _B > = 0.5 or α * _B > = 0.65 or α * _B > = 1.0.

According to the invention is low, like the Fig. 4a shows, a curvature distribution α * = f (s *), the high gradient at the starting point A, starting in the further course of the point B approaches with decreasing gradient. Likewise favorable according to the invention is a kink-free continuation of the curvature distribution from the point B with a further decreasing or constant gradient up to the trailing edge point H, the strongest curvature of the curvature distribution being provided in the range 0 <= s * <= 0.2, corresponding to FIG Fig. 4a illustrated crowd of curvature distributions according to the invention, which are particularly suitable for low and moderate aerodynamic profile loads.

The Fig. 4b shows an also according to the invention Schar of Skelettlinienwölbungsverteilungen, which is also suitable for aerodynamically highly loaded profiles. In this case, it is favorable according to the invention to initially provide the skeleton line curvature distribution starting from large gradients in the range 0 <= s * <= 0.1 in the further course with further decreasing gradients and from a point T in the range 0.1 <= s * <= 1 to increase the gradient again. Accordingly, the curvature at point T changes its sign. For the special case that the gradient increases continuously from the point T to the gradient, an S-shaped skeleton line curvature distribution results according to the invention, corresponding to FIG Fig. 4b shown crowd. According to the invention, a position of the point T in the range 0.35 <= s * <= 0.65 is particularly favorable.

It can also be favorable according to the invention if the skeletal line curvature distribution runs at least in a part of the range 0.1 <= s * <= 1 at constant values of α *, see the lowest skeletal line curvature distribution in FIG Fig. 4b ,

The Fig. 4c shows another Skelettlinienwölbungsverteilung invention, which divides the achieved in the range 0.1 <= s * <= 1 increase of the curvature in a certain way. For this purpose, the value α * _C provided at s * = 0.9 and thus the position of the point C is restricted. Thus, according to the invention, particularly favorable solutions result if α * _C <α * _B + 0.75 (1-α * _B ).

The skeleton line curvature distribution according to the invention is to be provided in at least one vane stream section in the region between the gap and a vane section at 5% of the main flow path width (0.05 W).

This skeleton line curvature distribution can be provided directly at the gap, but according to the invention must be provided at least within the 5% of the main flow path width W adjacent to the gap.

Very favorable is an application of the skeleton line curvature distribution according to the invention at least directly at the gap. In the flow machine according to the invention, such as, for example, blowers, compressors,

Pumps and fans have an edge flow control which, while maintaining the same stability, can increase the efficiency of each stage by approximately 0.3%. In addition, a reduction in the number of blades of up to 20% is possible. The inventive concept is applicable to different types of turbomachines and, depending on the degree of utilization of the concept, leads to reductions in costs and weight for the turbomachine of 2% to 10%. In addition, there is an improvement in the overall efficiency of the fluid flow machine, depending on the application, of up to 1.5%.

LIST OF REFERENCE NUMBERS

1

casing

2

hub

3

Machine axis (rotation axis)

4

Rotor (rotor blade row)

5

Stator (stator blade row)

6

Ring channel (main flow path)

7

Mean meridian current line

8th

Profile skeleton line

9

Streamlined cross-section

10

gap

Claims (11)

1. Fluid-flow machine including a blade arranged in a main flow path (6) confined by a hub (2) and a casing (1), with a gap (10) being provided between one end of the blade and a main flow path boundary formed by a hub (2) or a casing (1), and with a free blade end thus being provided, with a skeleton line camber distribution having an excessive value of the relative skeleton line camber of at least α* = 0.35 for a related running length of s* = 0.1 being provided in at least one blade profile flow line section in the area between the gap (10) and a blade section at a distance of 30 percent of the main flow path width W from the gap (10), with s* being the local running length relative to the total running length of the profile skeleton line and α* being formed as the angular change of the skeleton line relative to the total camber of the skeleton line achieved from the leading edge to a related running length s*, with the skeleton line camber distribution in this representation commencing in the leading edge point V of the blade (s* = 0, α* = 0) and terminating in the trailing edge point H of the blade (s* = 1, α* = 1), and with the total camber of the skeleton line being defined by the angular change of the skeleton line from the leading edge point (V) to the trailing edge point (H) of the blade, characterized in that a skeleton line camber distribution is provided at least within 5 % of the main flow path width adjoining the gap, said distribution, for a related running length of s* = 0.1, having an excessive value of the relative skeleton line camber of at least α* = 0.35.
2. Fluid-flow machine in accordance with Claim 1, characterized in that a skeleton line camber distribution is provided at least directly at the gap (10), which for a related running length of s* = 0.1 has an excessive value of the relative skeleton line camber of at least α* = 0.35.
3. Fluid-flow machine in accordance with one of the Claims 1 or 2, characterized in that for a related running length of s* = 0.1 an excessive value of the relative skeleton line camber of at least α* = 0.50 is provided.
4. Fluid-flow machine in accordance with one of the Claims 1 to 3, characterized in that the skeleton line camber distribution starts with high gradient in the leading edge point V and, in the further course, approaches with descending gradient the related running length s* = 0.1.
5. Fluid-flow machine in accordance with one of the Claims 1 to 4, characterized in that the skeleton line camber distribution continues from the related running length s* = 0.1 in the direction of the trailing edge point H up to the trailing edge point H without bent and with descending or constant gradient, with the point of maximum curvature of the skeleton line camber distribution being provided in the range of 0 <= s* <= 0.2.
6. Fluid-flow machine in accordance with one of the Claims 1 to 4, characterized in that the skeleton line camber distribution continues from the related running length s* = 0.1 in the direction of the trailing edge point H without bent with initially further descending gradient and, from a point T in which the camber changes its sign, has again rising gradients for at least a part of the range of 0.1 <= s* <= 1.
7. Fluid-flow machine in accordance with Claim 6, characterized in that the skeleton line camber distribution has only a single camber sign change and shows an S-shaped course.
8. Fluid-flow machine in accordance with one of the Claims 6 and 7, characterized in that the point T of the first camber sign change is provided in the range of 0.35 <= s* <= 0.65.
9. Fluid-flow machine in accordance with one of the Claims 1 to 8, characterized in that the skeleton line camber distribution extends, at least in a part of the range of 0.1 <= s* <= 1, at constant values of the relative skeleton line camber α*.
10. Fluid-flow machine in accordance with one of the Claims 1 to 9, characterized in that the skeleton line camber distribution, for a related running length of s* = 0.9, has a value of the relative skeleton line camber of α* < α*(s* = 0.1) + 0.75 (1 - α*(s* = 0.1)).
11. Fluid-flow machine in accordance with one of the Claims 1 to 10, characterized in that the skeleton line camber distribution extends cambered, cambered in sections or rectilinear in sections, thus having any number of bending points between the leading edge point V and the trailing edge point H.

Images