CN102927060B - A kind of suction port improving cavitation performance of centrifugal pump - Google Patents

Abstract

The invention discloses a suction port for improving the cavitation performance of a centrifugal pump, and relates to the technical field of centrifugal pump manufacturing. A return sleeve (2) is arranged at the pump inlet, and the return sleeve (2) is composed of an inner and outer two-layer annular inner ring and an outer ring. The inner diameter of the inner ring of the return sleeve is consistent with the size of the pump flow channel. The outer diameter is consistent with the size of the pump inlet of the pump body, and the gap between the inner ring and the outer ring is one-twentieth of the outer diameter of the return sleeve, which is used for backwater. There are 4 cube supports between the inner ring and the outer ring for connecting the inner ring and the outer ring. At the same time, 4 threaded holes are evenly distributed in the circumferential direction of the return sleeve to prevent the longitudinal movement of the return sleeve, and 4 threaded holes are evenly distributed in the direction of the return sleeve near the pump inlet to prevent the axial movement of the return sleeve. The invention has simple structure, convenient maintenance and can effectively improve the cavitation performance of the pump.

Description

A Suction Port for Improving Cavitation Performance of Centrifugal Pump

technical field

The invention belongs to the technical field of centrifugal pump manufacturing, in particular to a suction port for improving the cavitation performance of a centrifugal pump.

Background technique

In centrifugal pumps, cavitation is a common phenomenon. Cavitation can lead to damage to blades, induce vibration and noise, reduce efficiency, and increase pump use and maintenance costs. The main cause of cavitation: when the pump is running at a large flow rate, there is a fluid backflow vortex at the impeller suction inlet, and part of the fluid enters from the suction section, and flows to the impeller inlet because it cannot enter the impeller, turbulent flow will occur before the impeller suction inlet, The vortex, and due to the generation of the vortex, the internal pressure of the fluid decreases and the temperature rises, resulting in cavitation.

After retrieval, the patent applications related to the present invention include: anti-cavitation centrifugal pump (public number: CN101968064A), which guides a small amount of high-pressure water back to the impeller inlet, and injects the low-pressure area of the impeller inlet through the nozzle to improve the low-pressure area of the impeller inlet. Pressure, so as to avoid the occurrence of pump cavitation, but after the high-pressure liquid is introduced into the inlet, it mixes with the inlet liquid, resulting in a decrease in the pumping volume, which affects the working efficiency of the pump.

Anti-cavitation double-suction split-split centrifugal pump (public number: CN102042232A), with an inducer on both sides of the impeller, and a conical helical blade with no sweep angle on the inducer, so that the blade inlet and outlet angles are easy to adjust, and the anti-corrosion The cavitation performance is good, but the existing structure needs to be changed, and the manufacture and installation are more complicated.

A method for suppressing cavitation and flow separation in blades of liquid machinery (publication number: CN101734345A), in which cavitation or flow separation is likely to occur at the leading edge of the blade or a low-pressure area on the blade, and a moving surface is installed to cause local movement of the blade surface, thereby realizing Inhibition or control of cavitation and separation flow, but the processing and manufacturing are more complicated, and the efficiency is low due to the change of the original blade structure.

Contents of the invention

The technical problem to be solved by the present invention is that the cavitation performance of the existing centrifugal pump is poor and the efficiency of the pump is low when the existing centrifugal pump is at a small flow point. The NPSH of the pump can be reduced under the premise of affecting the efficiency.

The technical solution of the invention is: a suction port for improving the cavitation performance of a centrifugal pump, including a return sleeve for reducing the NPSH. Add a return sleeve between the pump inlet and the impeller inlet (that is, the suction flow channel), and place the return sleeve at a distance of 0.5 times the diameter of the impeller inlet from the impeller inlet, that is, the distance between the outer end of the return sleeve and the outer edge of the pump inlet is 0.5 The length of the diameter of the impeller inlet is doubled to prevent the liquid in the return sleeve from affecting the flow field at the impeller inlet. The return sleeve is composed of an inner and outer ring-shaped inner ring and an outer ring. The inner diameter of the inner ring of the return sleeve is consistent with the size of the pump flow channel. The outer diameter of the inner ring of the return sleeve is consistent with the size of the pump inlet of the pump body. The inner ring and the outer ring The gap between them is one-twentieth of the outer diameter of the return sleeve, which is the return water flow channel, and the axial ends of the inner ring are shorter than the outer ring by one-twentieth of the outer diameter of the return sleeve, which is the return water There are 4 cubic supports between the inner ring and the outer ring to connect the inner ring and the outer ring; at the same time, 4 threaded holes are evenly distributed in the circumferential direction in the middle of the return sleeve, and the return sleeve (2) is passed through the screw and the pump inlet Fix the backflow sleeve to prevent longitudinal movement, drill 4 threaded holes evenly distributed in the direction of the backflow sleeve near the pump inlet, and fix the backflow sleeve (2) to the pump inlet through screws to prevent the backflow sleeve from axial movement.

When the pump is running at a high flow point, the inflow medium is divided into two parts, one part flows directly into the impeller inlet through the inner diameter of the spacer, and the other part flows into the impeller inlet through the gap between the pump body and the spacer. It will not affect the flow of the medium into the impeller, and the pump efficiency will not change. At the same time, due to the existence of the spacer, the gas in the medium will be broken and fully mixed with the medium, which can reduce cavitation and effectively protect the impeller mouth ring and seal. However, when the pump is running at a small flow point, the excess medium flows back to the inlet of the pump body through the return sleeve. Vortex; at the same time, due to the pressure of the backflow fluid, the pressure of the fluid at the inlet of the impeller increases, which improves the ability of the pump to resist cavitation.

Description of drawings

Fig. 1 is a three-dimensional schematic diagram of the reflux sleeve of the present invention.

Figure 2 is a schematic diagram of the working of the return water jacket when the flow rate is large.

Fig. 3 is a schematic diagram of the working of the return water jacket at a small flow rate.

In the figure: 1. Pump body, 2. Return water jacket, 3. Impeller, 4. Impeller nut, 5. Pump cover, 6. Mechanical seal, 7. Pump shaft.

Detailed ways

With reference to Fig. 1, the centrifugal inlet structure of the present invention includes a return sleeve for reducing NPSH. The return sleeve is composed of an inner and outer ring-shaped inner ring and an outer ring. The size of the return sleeve is the same. The outer diameter of the inner ring of the return sleeve is consistent with the size of the pump inlet of the pump body. The gap between the inner ring and the outer ring is one-twentieth of the outer diameter of the return sleeve, which is the flow channel of the return water. The inner ring The two ends of the axial direction are shorter than the outer ring by one-twentieth of the outer diameter of the return sleeve, which is the inlet and outlet of the return water; there are 4 cube supports between the inner ring and the outer ring to connect the inner ring and the outer ring. Other structures of the centrifugal pump in the present invention are the same as those of the conventional centrifugal pumps, and will not be repeated here.

Referring to Figure 2, when the pump is running at a relatively large flow point, the inflow medium is divided into two parts, one part flows directly into the impeller inlet through the inner diameter of the spacer, and the other part flows into the impeller inlet through the gap between the pump body and the spacer. There are changes, so it will not affect the flow of the medium into the impeller, and the pump efficiency will not change. At the same time, due to the existence of the spacer, the gas in the medium will be broken and fully mixed with the medium, which will reduce the cavitation and effectively protect the impeller mouth ring. and seal.

Combined with Figure 3, the inlet of the pump is located between the pump inlet and the impeller inlet (that is, the suction flow channel), and then the return sleeve is added to flow to the impeller inlet medium, and the excess medium flows back to the pump body inlet through the return sleeve. At this time, the total flow rate at the inlet of the pump body does not change, and because the medium does not appear to accelerate and then decelerate, there will be no vortex. Eventually vibration and cavitation disappear. And the pressure of the backflow medium promotes the pressure of the impeller inlet medium to increase, which improves the anti-cavitation ability of the pump.

Claims (1)

1. A suction port for improving the cavitation performance of a centrifugal pump, characterized in that a return sleeve (2) is arranged in the flow channel at the pump inlet, and the return sleeve (2) is an annular inner ring and an annular outer ring. The inner diameter of the inner ring of the return sleeve is consistent with the size of the pump flow channel, the outer diameter of the inner ring of the return sleeve is consistent with the size of the pump inlet of the pump body, and the gap between the inner ring and the outer ring is 20% of the outer diameter of the return sleeve. One of them is the flow channel of the return water. The axial ends of the inner ring are shorter than the outer ring by one-twentieth of the outer diameter of the return sleeve, which is the inlet and outlet of the return water; there are 4 holes between the inner ring and the outer ring. A cube is supported to connect the inner ring and the outer ring; at the same time, 4 threaded holes are uniformly distributed in the middle of the return sleeve in the circumferential direction, and the return sleeve (2) is fixed to the pump inlet by screws to prevent the return sleeve from moving longitudinally. When the return sleeve is close to the pump Four threaded holes are evenly distributed in the inlet direction, and the return sleeve (2) is fixed to the pump inlet by screws to prevent the axial movement of the return sleeve; the distance between the outer end of the return sleeve (2) and the outer edge of the pump inlet is 0.5 times Impeller inlet diameter length.