A water discharge device for increasing the head of an axial flow pump under non-design conditions

Abstract

The present invention belongs to the field of hydraulic machinery and equipment, and discloses a water discharge device for improving the head of an axial flow pump under non-design conditions. It mainly includes an axial flow pump impeller, an impeller chamber, a guide vane body and a water discharge baffle cylinder. The impeller is installed on the rotating shaft through a key and an impeller nut, the impeller chamber is connected to the guide vane body through a flange, and a bearing installation position is designed in the middle part of the guide vane body to place the rotating shaft. The water discharge baffle cylinder is connected to the guide vane body, and a gap flow channel is formed between the guide vane hub. By controlling the size and position of the water discharge baffle cylinder, the flow turbulence after the impeller outlet under non-design conditions of the axial flow pump can be suppressed, the interlayer influence of the flow in the guide vane body can be reduced, the saddle area in the head-flow curve of the axial flow pump under small flow rate can be improved or even eliminated, the flow separation at the outlet of the diffusion guide vane flow channel of the axial flow pump under large flow rate can be suppressed, the head of the axial flow pump under non-design conditions can be improved, and the efficient operation range of the axial flow pump can be expanded.

Description

Technical Field

[0001] The invention belongs to the field of hydraulic machinery equipment in fluid machinery, and relates to a novel outlet device for an axial flow pump, which is suitable for all axial flow pumps and has the most obvious lifting effect on a submersible axial flow pump with a built-in motor. Background Art

[0002] The head-flow curve of a traditional axial flow pump has a narrow efficient operating range and usually has a saddle area, where the same head can correspond to two flow rates, and the operating efficiency on both sides of the design flow point in the curve decays rapidly.

[0003] When the axial flow pump enters a small flow range that is not in the design condition due to changes in the inlet water level, flow regulation, etc., the axial flow pump is prone to rotational stall, causing violent vibration and causing damage to the unit.

[0004] When entering the large flow range, the diffusion flow of the guide vane flow channel is prone to boundary layer flow separation, resulting in vortex blocking the main flow channel, causing the head to decrease. At present, there is no effective measure to solve the problem of non-design conditions.

[0005] The purpose of the present invention is to suppress the flow turbulence after the impeller outlet, reduce the interlayer influence of the flow in the guide vane body, improve or even eliminate the saddle area in the head-flow curve of the axial flow pump at a small flow rate, and at the same time optimize the internal flow of the axial flow pump guide vane at a large flow rate, suppress the flow separation at the guide vane outlet, increase the head of the axial flow pump under non-design conditions, and expand the efficient operation range of the axial flow pump. Summary of the invention

[0006] The present invention is achieved through the following technical solutions:

[0007] The water discharge device for improving the head of the axial flow pump under non-design conditions mainly includes the axial flow pump impeller, impeller chamber, guide vane body and water discharge baffle cylinder. The impeller is installed on the rotating shaft through a key and an impeller nut. The impeller chamber and the guide vane body are connected through a flange. A bearing installation position is designed in the middle part of the guide vane body to place the rotating shaft.

[0008] The feature of the water outlet device is that a cylindrical water outlet baffle is added behind the impeller, and the baffle cylinder is connected to the guide vane body. The diameter of the baffle cylinder is larger than the hub diameter of the guide vane body, and a radial gap is formed between the two parts, and the gap size is within 50% of the radial distance of the flow channel, and the ratio of the distance between the end of the baffle cylinder and the axial projection of the impeller outlet side to the impeller diameter is within 10%.

[0009] The cylinder of the water outlet device of the present invention is a rotating body, the generatrix is ​​parallel to the generatrix of the guide vane body hub, the cylinder intersects with the guide vane blades, and is connected to the guide vane body in two ways. The first way is to manufacture it together with the guide vane body, and the second way is to manufacture it separately, and the connection with the guide vane is completed by welding or a circle of connecting bolts are arranged along the circumference of the partition cylinder mouth to connect the partition cylinder to the guide vane body hub.

[0010] The water outlet device of the present invention is characterized by adding a concentric cylinder to form a double-layer flow channel after the impeller outlet, and the cylinder is close to the hub side. The relative flow angles of the impeller blades at different radii at the outlet edge are greatly different. When the flow rate is lower than the design flow rate, the axial components of the absolute velocity at different radii are reduced at the same time according to the flow theory, but the circumferential components of the absolute velocity will form obvious differences due to different flow angles according to the velocity triangle theory, thereby causing differences in head at different radii and causing backflow at the hub.

[0011] At low flow rates, the double-layer flow channel formed by the added cylinder plays a guiding role, reducing the impact of impeller outlet backflow on the mainstream. At design flow rates and large flow rates, the inner cylinder plays a separating role, reducing the interlayer impact of the flow in the guide vane body, and plays a multi-channel water outlet role for the flow downstream of the guide vane. When the water flows out of the guide vane body, the flow separation phenomenon is improved and the head value is increased.

[0012] The practicality of the present invention lies in that, through structural improvement, the internal flow of the axial flow pump under two non-design conditions, small flow and large flow, is improved at the same time, the flow behind the impeller, inside the guide vane body and behind the guide vane outlet is optimized, the head value of the axial flow pump is increased, and the application range of the axial flow pump is expanded. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the water outlet device of the axial flow pump of the present invention.

[0014] The markings in the figure are: 1. impeller; 2. impeller chamber; 3. guide vane body; 4. key; 5. rotating shaft; 6. bearing; 7. water outlet baffle cylinder; 8. flange bolt; 9. impeller nut. DETAILED DESCRIPTION

[0015] This section will disclose detailed embodiments of the present invention.

[0016] The structure of the water outlet device behind the impeller in this embodiment is as shown in the attached figure. Figure 1As shown, it mainly includes an axial flow pump impeller (1), an impeller chamber (2), a guide vane body (3) and a water outlet baffle cylinder (7). The impeller (1) is assembled with the shaft (5) through a key (4) and is locked by an impeller nut (9). The impeller chamber (2) and the guide vane body (3) are connected together by flange bolts (8). A bearing (6) is provided in the middle of the guide vane body to install and fix the rotating shaft. The water outlet baffle cylinder (7) intersects with the guide vane blades in the guide vane body and is welded together. The cylinder is close to the guide vane body hub and is a rotating body. The generatrix is ​​the same as the guide vane body hub and the thickness is 1% of the outer diameter of the impeller. A gap flow channel is formed between the cylinder and the guide vane body hub, and water can flow downstream or upstream through the gap. The size of the gap does not exceed 50% of the radial size of the guide vane flow channel, the length of the cylinder extending into the guide vane body does not exceed 1 / 4 of the length of the guide vane axial surface, and the distance from the end of the cylinder on the axial surface to the impeller outlet edge is less than 10% of the outer diameter of the impeller. After the cylinder is installed, the rotation of the impeller (1) is not affected.

Claims

1. A water discharge device for improving the non-design working head of an axial flow pump, mainly comprising an axial flow pump impeller, an impeller chamber, a guide vane body and a cylindrical water discharge baffle, the impeller is mounted on the rotating shaft through a key and an impeller nut, the impeller chamber and the guide vane body are connected through a flange, a bearing seat is designed in the middle of the guide vane body, and the shaft is connected by placing a bearing, and the characteristics are: A cylindrical water outlet baffle is added behind the outlet of the axial flow pump impeller. The cylindrical water outlet baffle is geometrically a body of revolution about the axis of rotation, and intersects with the guide vane blade space in the guide vane body. The baffle can be manufactured in an integrated manner with the guide vane body; or it can be manufactured separately and connected to the guide vane blade by welding; or it can be manufactured separately and fastened to the guide vane body hub by bolts. The diameter of the baffle barrel is larger than the diameter of the guide vane body hub, and a radial gap is formed between the cylindrical baffle and the guide vane body hub.

2. The water outlet device according to claim 1, characterized in that: The gap between the cylindrical water outlet baffle and the guide vane body hub is less than 50% of the radial width of the flow channel.

3. The water outlet device according to claim 1, characterized in that: The length of the cylindrical water outlet baffle extending into the guide vane body shall not exceed 1 / 4 of the length of the guide vane axial surface.

4. The water outlet device according to claim 1, characterized in that: The distance between the end of the cylindrical water outlet baffle and the projection of the axial surface of the impeller outlet edge on the axial surface is less than 10% of the impeller diameter.

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