CN102062116A - Gap diversion type axial-flow pump impeller - Google Patents

Abstract

The invention relates to a slit drainage type axial flow pump impeller. It includes a hub and blades fixed on the hub, and the blades have gaps for drainage. When the fluid passes through the gap, a new boundary layer is generated on the back of the blade, which can withstand the reverse pressure gradient of the fluid and effectively eliminate the flow separation of the boundary layer, thereby reducing energy loss and ensuring that the axial flow pump has a good performance under all working conditions. higher efficiency.

Description

Slit drainage axial flow pump impeller

technical field

The invention relates to a slit drainage type axial flow pump impeller, which belongs to the field of fluid machinery.

Background technique

Axial flow pumps have the characteristics of large flow and low head, and are widely used in fields such as water diversion in river basins, farmland irrigation, flood control and drainage, municipal water supply, and water circulation in power plants. Axial flow pump is used. Axial flow pumps have higher efficiency at the design point, but the range of high efficiency is narrow and there is an unstable operation area. During the actual operation of the axial flow pump, it often deviates from the design point, and the boundary layer flow separation is easy to occur on the back of the impeller to form backflow, as shown in Figure 1. The flow separation of the boundary layer leads to a large wake vortex resistance, and the wake vortex resistance is often dozens of times the friction resistance of the boundary layer without flow separation, resulting in excessive energy loss and directly affecting the efficiency of the water pump. It can be seen that at a certain incoming flow angle of attack, controlling the flow separation of the boundary layer on the back of the blade can effectively improve the performance of the impeller, thereby helping to improve the performance of the axial flow pump under all working conditions. Therefore, it is particularly important to design an axial flow impeller that can effectively eliminate the wake vortex resistance caused by flow separation.

Contents of the invention

The purpose of the present invention is to address the defects of the prior art, to provide a gap drainage type axial flow pump impeller, to improve the performance of the axial flow water pump under all working conditions, to eliminate flow structures such as backflow caused by boundary layer separation, and to avoid unnecessary energy loss, thereby improving the efficiency of the impeller.

To achieve the above object, the present invention adopts the following technical solutions:

A slit drainage type axial flow pump impeller includes a hub and blades fixed on the hub, each blade has a gap to divide the blade into a front blade and a rear blade.

The position of the slot of the blade is located within the range of 5-40% of the chord length close to the leading edge of the blade.

The flow direction of the slit, that is, the average normal direction of the flow surface of the slit forms an included angle of 10-60° with the axis of the hub.

The flow direction of the slit, that is, the average normal direction of the flow surface of the slit forms an included angle of 10-60° with the chord line of the airfoil.

The flow channel direction of the slit of the blade should follow the flow direction of the fluid in the impeller.

The slit centerline surface of the blade is a spatial curved surface approximately vertical to the hub, formed by the trailing edge of the front blade and the front edge of the rear blade.

Shape determines.

The gap width of the blade is 0.5 to 3 times the maximum thickness of the blade.

Compared with the prior art, the present invention has the following obvious outstanding substantive features and significant advantages: before the boundary layer on the back of the blade is separated from the flow, the original boundary layer on the back of the blade is brought into the main flow by the fluid passing through the gap , thus forming a new boundary layer, which can withstand the reverse pressure gradient of the fluid to avoid flow separation. The gap drainage structure of the present invention can effectively eliminate the wake vortex resistance caused by flow separation, thereby improving the working efficiency of the impeller, especially the efficiency of the axial flow water pump at the non-design working point, and finally ensuring the axial flow water pump. All-condition performance.

Description of drawings

Figure 1. Schematic diagram of the flow field in the wake vortex area generated by the boundary layer flow separation of the blades of the traditional axial flow pump impeller;

Fig. 2 Schematic diagram of the structure of the impeller of the slit drainage axial flow pump;

Fig. 3 Schematic diagram of the structure of the impeller blade of the slit drainage axial flow pump;

Figure 4 is a schematic diagram of the flow field after using the slot-draining impeller blades.

Detailed ways

In order to make the technical means realized by the present invention and its effects easy to understand, the following preferred embodiments further illustrate the present invention in conjunction with the accompanying drawings.

Embodiment 1: Referring to Fig. 2 and Fig. 3, the impeller of the slit-drainage axial flow pump includes a hub 1 and a blade 2 fixed thereon. There is a gap 6 in the middle of the blade, so that the blade 2 is divided into front blade 3 and Back blade 4.

Embodiment 2: This embodiment is basically the same as Embodiment 1, and the special features are as follows: Referring to accompanying drawings 2 and 3, the impeller of an axial-flow water pump is composed of a hub 1 and a blade 2 fixed thereon, wherein the blade 2 Evenly distributed on the hub 1, the number of blades 2 can be three, four or other numbers, and the number of blades is mainly selected according to the design requirements of the pump.

The impeller in this embodiment can be a cast impeller made of grease sand, resin sand or paste gold sand, or a precision cast impeller, or can be a metal processing impeller or a welded impeller. In addition, the idea of this embodiment is not only applied to the impeller of the axial flow water pump, but also applicable to centrifugal or mixed flow impeller blades. Regardless of the type of impeller blade, the opening direction of the gap 6 should conform to the flow direction of the fluid, and at the same time be located within the range of 5-40% of the chord length from the leading edge of the blade.

In the impeller of this embodiment, the blade 2 is divided into a front blade 3 and a rear blade 4 by performing slit processing on the blade 2 . The flow channel direction of the gap 6 should conform to the flow direction of the fluid. The opening position of the gap 6 is located at a distance of 5-40% of the chord length from the leading edge 5 of the blade 2. The average normal direction of the gap flow surface along the flow direction of the gap 6 is the same as The included angle of the chord line in the shape plane is 10~60°, the average normal direction of the gap 6 along the flow direction and the axis of the hub 1 form an included angle of 10~60°, and the centerline surface of the slot 6 is approximately The spatial curved surface of the vertical hub 1 is determined by the shape of the trailing edge of the front blade 3 and the front edge of the rear blade 4, and the width of the gap 6 ranges from 0.5 to 3 times the maximum thickness of the blade.

Axial flow pumps have the best efficiency at the optimum working point, but in general use, axial flow pumps often operate at non-design working points. During the rotation of a traditional axial-flow impeller, the fluid often produces flow separation in the boundary layer shortly after passing through the leading edge 5 of the blade, thus affecting the working efficiency of the blade, as shown in Figure 1 . By adopting the slit treatment, part of the fluid enters the flow channel of the impeller through the slit 6, thereby forming a new boundary layer, which can withstand the reverse pressure gradient of the fluid and eliminate the flow separation of the boundary layer, as shown in Figure 4. Due to the disappearance of the separation zone, the flow resistance is greatly reduced, thereby improving the performance of the axial flow water pump under all working conditions.

Claims (7)

1. slit drainage type axial-flow pump impeller comprises wheel hub (1) and fixes blade (2) on it, it is characterized in that having slit (6) in the middle of the described blade, thereby blade (2) is divided into front vane (3) and rear blade (4).

2. slit according to claim 1 drainage type axial-flow pump impeller is characterized in that: described slit (6) are positioned at 5 ~ 40% chord length positions near the leading edge (5) of blade (2).

3. slit according to claim 1 drainage type axial-flow pump impeller is characterized in that: the flow direction of described slit (6) is that the average Normal direction of slit flow-passing surface becomes 10 ~ 60 ° angle with the axis of wheel hub (1).

4. slit according to claim 1 drainage type axial-flow pump impeller is characterized in that: the width of described slit (6) is 0.5 ~ 3 times of blade (2) maximum ga(u)ge.

5. slit according to claim 1 drainage type axial-flow pump impeller is characterized in that: the runner direction of described slit (6) should be complied with the flow direction of fluid in impeller.

6. slit according to claim 1 drainage type axial-flow pump impeller is characterized in that: the flow direction of described slit (6) is that the average Normal direction of slit flow-passing surface becomes 10 ~ 60 ° angle with the string of a musical instrument of place aerofoil profile.

7. slit according to claim 1 drainage type axial-flow pump impeller is characterized in that: described slit (6) center line face is for being similar to the space curved surface of vertical wheel hub (1), by the shape decision of front vane (3) trailing edge and rear blade (4) leading edge.

Images