Blade and axial flow impeller using same

Disclosed in the present application is a blade and an axial flow impeller using same. The blade comprises a blade tip, a blade root, a leading edge, a trailing edge, an upper surface and a lower surface. The upper surface and lower surface are disposed opposite each other; the blade tip, the blade root, the leading edge and the trailing edge surround the upper surface and the lower surface, and connect the upper surface and the lower surface. The blade is rotatable about a rotation axis, the rotation axis being perpendicular to a normal plane. The blade tip comprises a blade tip base part and a blade tip trailing part, the blade tip base part being close to the leading edge, and the blade tip trailing part being close to the trailing edge and being bent upwards relative to the blade tip base part. An angle of attack of a chord of the blade tip trailing part is greater than an angle of attack of a chord of the blade tip base part, wherein the angle of attack is an acute included angle between the chord and the normal plane. The blade of the present application can provide a large air volume, and has higher static pressure and higher efficiency.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from and the benefit of Chinese Patent Application No. 202010290698.0, filed Apr. 14, 2020, which is herein incorporated by reference in its entirety for all purposes.

TECHNICAL FIELD

The present application relates to the field of rotary machinery such as fans, pumps and compressors, in particular to a blade and an axial flow impeller using same.

BACKGROUND ART

The leading edge and trailing edge of a conventional blade are generally monotonous, smooth curves. Due to serious flow separation at the surface of the blade, vortices are formed, and consequently the blade has low aerodynamic performance and high noise.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present application can solve at least some of the above-mentioned problems.

According to a first aspect of the present application, the present application provides a blade, comprising a blade tip, a blade root, a leading edge, a trailing edge, an upper surface and a lower surface. The upper surface and lower surface are disposed opposite each other; the blade tip, the blade root, the leading edge and the trailing edge surround the upper surface and the lower surface, and connect the upper surface and the lower surface. The blade is rotatable about a rotation axis, the rotation axis being perpendicular to a normal plane. The blade tip comprises a blade tip base part and a blade tip trailing part, the blade tip base part being close to the leading edge, and the blade tip trailing part being close to the trailing edge and being bent upwards relative to the blade tip base part. An angle of attack of a chord of the blade tip trailing part is greater than an angle of attack of a chord of the blade tip base part, wherein the angle of attack is an acute included angle between the chord and the normal plane.

In the blade according to the abovementioned first aspect, the upper surface extends smoothly from the blade tip to the blade root.

In the blade according to the abovementioned first aspect, the range of values of the angle of attack of the chord of the blade tip trailing part is greater than or equal to 200 and less than or equal to 30°.

In the blade according to the abovementioned first aspect, the proportion of the length of the blade tip taken up by the blade tip trailing part is greater than or equal to 1/12 and less than or equal to ⅛.

In the blade according to the abovementioned first aspect, a projection of the leading edge on the normal plane in the direction of the rotation axis is a first curve, and the first curve has an even number of inflection points.

In the blade according to the abovementioned first aspect, a line connecting any point on the first curve and the perpendicular foot is a first connecting line. A line connecting the perpendicular foot and a point of projection of the intersection point of the blade root and the leading edge on the normal plane in the direction of the rotation axis is a second connecting line. An included angle between the first connecting line and the second connecting line is called a leading edge angle θ. The leading edge angle θ of any point on the first curve satisfies θ∈[0°,20°].

In the blade according to the abovementioned first aspect, the trailing edge is provided with multiple grooves, and a projection of the trailing edge on the normal plane in the direction of the rotation axis is a second curve, wherein an included angle between groove walls of each groove is a, a groove depth is H, and the length of the second curve is L.

The included angle and the groove depth satisfy:
α∈[10°,110°];
H=W×L, W∈[1.5%,20%].

In the blade according to the abovementioned first aspect, the included angle α between the groove walls of the groove closest to the blade tip in the multiple grooves satisfies: α∈[80°, 110°].

In the blade according to the abovementioned first aspect, the length of the trailing edge between groove walls of two adjacent said grooves is the same.

In the blade according to the abovementioned first aspect, on the trailing edge of the blade, the upper surface of the blade extends further than the lower surface in a circumferential direction, and a cross section of the trailing edge in the circumferential direction of the blade is arc-shaped.

According to a second aspect of the present application, the present application provides an axial flow impeller, comprising a hub and at least two blades according to the abovementioned first aspect. The hub has a rotation axis, the hub being rotatable about the rotation axis. The at least two blades are arranged on an outer circumferential face of the hub.

The blade of the present application can provide a large air volume, and has higher static pressure and higher efficiency.

DETAILED DESCRIPTION OF THE INVENTION

Various specific embodiments of the present application will be described below with reference to the drawings which form a part of this description. In the following drawings, identical parts and components are indicated by identical reference numerals.

FIG.1shows a three-dimensional drawing of an axial flow impeller100using the blade in an embodiment of the present application. As shown inFIG.1, the axial flow impeller100comprises a hub110and three blades112. The hub110has a rotation axis X: a cross section of the hub110perpendicular to the rotation axis X is circular. The three blades112are evenly arranged on an outer circumferential face of the hub110, and are integrally connected to the hub110. The hub110and the blades112may rotate about the rotation axis X together. As an example, the axial flow impeller100of the present application rotates around the rotation axis X clockwise (that is, in the rotation direction indicated by the arrow inFIG.1). Those of ordinary skill in the art can understand that the hub110may also have another shape, and the number of blades112may be at least two. The hub110may be shaped in accordance with the number of blades112. For example, when the number of blades112is three, the cross section of the hub110perpendicular to the rotation axis X is triangular; when the number of blades112is four, the cross section of the hub110perpendicular to the rotation axis X is quadrilateral.

FIG.2shows a three-dimensional drawing of the blade112used in the axial flow impeller100inFIG.1. As shown inFIG.2, the blade112comprises an upper surface242, a lower surface244, a blade tip216, a blade root218, a leading edge222and a trailing edge220. The upper surface242and lower surface244are disposed opposite each other. “Leading edge222” refers to the front-end edge in the direction of blade rotation. “Trailing edge220” refers to the rear-end edge in the direction of blade rotation. “Blade root218” refers to an edge where the blade and the hub intersect. “Blade tip216” refers to the other edge opposite the blade root. The blade tip216, blade root218, leading edge222and trailing edge220surround the upper surface242and the lower surface244. That is to say, the upper surface242and the lower surface244each extend from the blade tip216to the blade root218, and also each extend from the leading edge222to the trailing edge220. The trailing edge220of the blade112of the present application is provided with multiple grooves232, each of the multiple grooves232extending towards the leading edge222.

The axial flow impeller100has a normal plane (not shown) that is perpendicular to the rotation axis X, and the rotation axis X and the normal plane perpendicularly intersect at the perpendicular foot O (seeFIG.3). Those of ordinary skill in the art can understand that the normal plane is a virtual plane intended to better illustrate the specific structure of the blade112.

FIG.3shows a projection of the blade112inFIG.1on the normal plane in the direction of the rotation axis X. A projection of the leading edge222of the blade112on the normal plane in the direction of the rotation axis X is a first curve, wherein the first curve has two inflection points a and b. The inflection points are demarcation points between concave arcs and convex arcs.

As shown inFIG.3, the first curve has two inflection points, inflection point a and inflection point b. A point of projection of the intersection point of the blade root218and the leading edge222on the normal plane in the direction of the rotation axis X is a point A, and a point of projection of the intersection point of the blade tip216and the leading edge222on the normal plane in the direction of the rotation axis X is a point B. The curve from point A to inflection point a and the curve from inflection point b to point B are concave arcs; the curve from inflection point a to inflection point b is a convex arc. A point P is any point on the first curve, and a line connecting point P and the perpendicular foot O is a first connecting line. A line connecting point A and the perpendicular foot O is a second connecting line. An included angle between the first connecting line and the second connecting line is a leading edge angle θ. In an embodiment of the present application, the leading edge angle θ of any point P on the first curve satisfies θ∈[0°, 20°], and the line connecting any point P on the first curve and the perpendicular foot O is on the same side of the second connecting line.

Those skilled in the art will understand that the first curve in the present application can have any even number of inflection points, with no restriction to the two inflection points shown in the present application.

The inventors of the present application have found that when the leading edge angle θ satisfies θ∈[0°, 20°], the work length of the leading edge222having the concave arcs and convex arc can be increased effectively, thereby reducing the load on the leading edge222of the blade112. When the blade112rotates, the concave arcs and convex arc on the leading edge222can forcibly split a large shed vortex that originally gathered on the upper surface of the blade112near the leading edge222into multiple small vortices, and as the blade112rotates, this causes the multiple small vortices to be located in a middle region of the blade112and at positions close to the trailing edge220. Thus, the multiple small shed vortices located in the middle region of the blade112and at positions close to the trailing edge220can effectively reduce the intensity of turbulence as well as dissipation losses caused by turbulence, thus improving aerodynamic performance. As an example, the static efficiency value of a conventional blade is about 40%, whereas the static efficiency value of the blade112of the present application can reach 50%; this can effectively improve aerodynamic performance by 25%. In addition, when the multiple small vortices produced by splitting are flowing towards the trailing edge220, they are not prone to mutual movement in the radial direction of the blade112to cause secondary flows, and relative speed flow lines of air on the surface of the blade112cross over each other as little as possible; thus, at the same time as the aerodynamic performance is improved, it is also possible to reduce noise. As an example, the blade112of the present application can reduce the noise value by 4 dB compared with a conventional blade (a reduction of 13%).

FIG.4is a projection, on the normal plane in the direction of the rotation axis X. of a blade112whose trailing edge220is not provided with multiple grooves232, and is intended to show multiple distribution points K of grooves232. Multiple grooves232are provided according to the positions of the multiple distribution points K, thereby obtaining the blade112ofFIG.3, which has multiple grooves232provided on the trailing edge220. As shown inFIG.4, the trailing edge220has a contour line402. The trailing edge220is provided with multiple grooves232, each groove has a distribution point K. and the distribution point K of each groove is located on the contour line402.

FIG.5Ais an enlarged projection of the groove232shown inFIG.2on the normal plane in the direction of the rotation axis X. and is intended to show the specific structure of the groove232. The shape of the groove232shown inFIG.5Ais determined on the basis of one distribution point K inFIG.4. As shown inFIG.4, the projection of the trailing edge220of the blade112without grooves on the normal plane in the direction of the rotation axis X is a second curve, and the length of the second curve is L. The groove232has a groove wall NE, a groove wall MF and a groove bottom EF. Lines of extension of the groove wall NE and groove wall MF intersect at a point G, and the groove wall NE and groove wall MF form an included angle α. A line connecting the distribution point K and point G is perpendicular to the tangent to the contour line402at the distribution point K. The line connecting the distribution point K and point G forms the groove depth H. The groove bottom EF is arc-shaped, and is tangent to the groove wall NE and the groove wall MF at a point E and a point F respectively.

As an example, a straight line perpendicular to the contour line402is drawn at the distribution point K, and the position of the bottom point G is determined according to the groove depth H. The groove depth H satisfies:
H=W×L, W∈[1.5%,20%].

A groove wall line NG and a groove wall line MG form an included angle α, and the included angle α satisfies α∈[10°, 110°].

MN is the opening width of the groove232. The groove bottom EF is arc-shaped, and has radius r. The groove bottom EF is tangent to the groove wall line NG and the groove wall line MG at points E and F, respectively, thereby forming the groove wall NE and groove wall MF. The radius r satisfies r∈[ 1/25H, ⅕H].

FIG.5Bis a schematic drawing of the specific structure of the groove232in another embodiment of the present application. The groove232shown inFIG.5Bis substantially the same as the groove232shown inFIG.5A, so a superfluous description is not given here. Unlike the groove232shown inFIG.5A, a straight line perpendicular to the contour line402is drawn at a point C close to the distribution point K. and the position of the bottom point G is determined according to the groove depth H. The groove depth H satisfies:
H=W×L, W∈[1.5%,20%].

A groove wall line NG and a groove wall line MG form an included angle α, and the included angle α satisfies α∈[10°, 110°].

In addition, an offset angle θ is formed between the straight line KG and the straight line CG; the offset angle Ω satisfies Ω∈[0°, 15°]. Point C may be at the left side of point K, or at the right side of point K.

As an example, the length of the trailing edge220between groove walls of adjacent grooves232is the same.

As another example, the multiple grooves232are configured such that the groove depths H thereof increase progressively by equal increments from the blade root218to the blade tip216.

Continuing to refer toFIG.3, in the present application, the groove232closest to the blade tip216is configured such that the included angle α satisfies α∈[80°, 110°].

The grooves232at the trailing edge220in the present application can reduce the power consumption of the blade112.

FIG.6is a side view of one of the blades112and the hub110inFIG.1, and is intended to show the specific structure of the blade tip216.FIG.7is a simplified diagram showing the relationship of a blade tip trailing part610shown inFIG.6to a blade tip base part612. As shown inFIGS.6-7, the blade tip216comprises the blade tip base part612and the blade tip trailing part610. The blade tip base part612and the blade tip trailing part610are smoothly connected, such that the blade112extends smoothly from the leading edge222to the trailing edge220, and extends smoothly from the blade tip216to the blade root218. That is to say, there is no inflection point between the blade tip base part612and the blade tip trailing part610. The blade tip trailing part610is bent upwards relative to the blade tip base part612. Specifically, a straight line connecting two ends of the blade tip base part612is a chord L1. A straight line connecting two ends of the blade tip trailing part610is a chord L2. An acute included angle between the chord and the normal plane perpendicular to the rotation axis X is an angle of attack §. The angle of attack §2of the chord L2of the blade tip trailing part610is greater than the angle of attack § 1 of the chord L1of the blade tip base part612.

In the present application, the upward-bent structure of the blade tip trailing part610of the blade112has the advantage of reducing blade noise w % bile increasing blade air volume. Specifically, the inventors of the present application have found that in a conventional blade, when the blade rotates, vortices on the blade will be shed from the trailing edge. This rapid shedding of vortices will increase the vortex intensity, thereby causing an increase in noise. In the blade112of the present application, the upward-bent structure of the blade tip trailing part610is disposed close to the trailing edge220, and will not cause an adverse effect whereby the leading edge222has a large load while the trailing edge220has a small load. The blade tip trailing part610close to the trailing edge220has maximum tangential speed (the speed in a direction perpendicular to the radial direction), and can split vortices at the trailing edge220so as to form smaller vortices, thereby delaying the shedding of vortices on the lower surface244. This splitting into small vortices can effectively reduce noise and also improve sound quality.

In addition, the upward-bent structure of the blade tip trailing part610can increase the work angle of the blade112while causing virtually no additional force to the blade112, and thereby increase the work done by the blade112, so as to increase the air volume of the blade112and increase the static pressure.

It must be explained that while the upward-bent structure of the blade tip trailing part610is provided on the blade112of the present application, the multiple grooves232mentioned above are also provided at the trailing edge220. In this case, the technical effect achieved by the grooves232will be added to the technical effect achieved by the blade tip trailing part610, so that the air volume of the blade112can still be increased while reducing the work done by the blade112. In other embodiments, either the upward-bent structure or the grooves may be provided alone.

As an example, the proportion of the length of the blade tip216taken up by the length of the blade tip trailing part610is greater than or equal to 1/12 and less than or equal to ⅛.

As another example, the angle of attack

FIG.8Ais a top view of one of the blades112and the hub110inFIG.1.FIG.8Bis a section taken along a centre line A-A of the blade112and hub110inFIG.8A. It can be seen fromFIGS.8A-8Bthat the blade tip216of the blade112has the blade tip trailing part610. The upper surface242of the blade112extends smoothly from the blade root218to the blade tip216.

FIG.9is a sectional drawing of the trailing edge220of the blade112in a circumferential direction. As an example,FIG.9shows a sectional drawing of the trailing edge220within the circle inFIG.6in the circumferential direction. As shown inFIG.9, the trailing edge220and the lower surface244form a bevel. Specifically, the upper surface242extends further than the lower surface244. The trailing edge220connects the upper surface242and the lower surface244, and the trailing edge220is smoothly connected to the lower surface244. As an example, a circumferential section of the trailing edge220is arc-shaped.

The inventors of the present application have found that, compared with a conventional blade having a trailing edge and lower surface that do not form a bevel, the efficiency of a blade112having a trailing edge220that forms a bevel with the lower surface244can be increased by about 4%, and noise can be reduced by about 12%.

FIG.10is a graph of the relationship between static pressure and air volume, for the blade112of the present application and a conventional blade. It can be seen fromFIG.10that, for the same air volume, the static pressure of the blade of the present application is higher than the static pressure of the conventional blade by approximately 60 pa, so the blade of the present application can satisfy application scenarios with higher static pressure requirements.

FIG.11is a graph of the relationship between efficiency and air volume, for the blade112of the present application and a conventional blade. It is clear fromFIG.11that for the same air volume, the efficiency of the blade of the present application is higher than that of the conventional blade. In particular when the air volume increases, the efficiency of the blade112of the present application does not fall by much, whereas the efficiency of the conventional blade falls more quickly.

FIG.12is a graph of the relationship between noise and air volume, for the blade112of the present application and a conventional blade. It is clear fromFIG.12that for the same air volume, the noise of the blade of the present application is lower than that of the conventional blade. In addition, the noise sound quality produced by the blade112of the present application is superior to that produced by the conventional blade.

Moreover, it can also be seen fromFIGS.10-12that for the same input power, the range of air volumes that the blade112of the present application is able to provide is higher, specifically 17000 m3/h-23000 m3/h, so the blade of the present application can satisfy application scenarios with higher air volume requirements.

It must be explained that a blade profile cross section of the blade112from the leading edge to the trailing edge may be of various types; it may be a cross section of equal thickness or any two-dimensional airfoil profile.

Although only some characteristics of the present application are shown and described herein, those skilled in the art can make various improvements and modifications. Therefore, it should be understood that the attached claims are intended to cover all of the above-mentioned improvements and modifications falling within the scope of the substantive spirit of the present application.