A fast switching structure of a single-stage and multi-stage centrifugal pump and a working method thereof

Abstract

The present invention discloses a rapid switching structure of a single-stage and multi-stage centrifugal pump, comprising a mechanical seal bracket, the mechanical seal bracket is fixed on a motor middle cover, a motor end cover is arranged on the front side of the motor middle cover, a motor front cover is arranged on the front side of the motor end cover, a main shaft is arranged in the mechanical seal bracket, a shaft sleeve, a secondary impeller, a friction ring A, a primary impeller and an inducer are sequentially sleeved on the main shaft from the back to the front, and a first regulating device for controlling the first-stage guide vane outlet position to be connected or blocked with the motor end cover channel A and a second regulating device for controlling the first-stage guide vane outlet position to be connected or blocked with the secondary impeller inlet is arranged on the motor front cover. The present invention also discloses a working method of the rapid switching structure. The rapid switching structure of a single-stage and multi-stage centrifugal pump and its working method provided by the present invention can quickly switch the single-stage / multi-stage centrifugal pump structure, ensure that the pump unit can replace the single / multi-stage impeller in time to match the best environmental conditions, and save manpower and financial costs on site.

Description

Technical Field

[0001] The invention relates to a fast switching structure of a single-stage and multi-stage centrifugal pump and a working method thereof, belonging to the technical field of fluid machinery. Background Art

[0002] At the same flow rate and speed, compared with a single-stage centrifugal pump, a multi-stage centrifugal pump can provide a higher head by consuming more power. In scenarios such as mine drainage, it is necessary to use single-stage / multi-stage centrifugal pumps according to the amount of water on site. In the existing multi-stage centrifugal pump structure, it is necessary to disassemble the motor front cover, the first-stage impeller, the first-stage guide vane and other flow-through components in turn, and then reinstall the motor front cover and other components to switch the multi-stage pump to a single-stage pump structure. Due to the complex structure of the flow-through components, the disassembly and assembly process is relatively cumbersome, wasting a lot of manpower, material resources and precious time. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a quick switching structure for single-stage and multi-stage centrifugal pumps, which can quickly switch the single-stage / multi-stage centrifugal pump structure, ensure that the pump unit can replace the single / multi-stage impeller in time to match the optimal environmental working conditions, and save on-site manpower and financial costs.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A fast switching structure between a single-stage and a multi-stage centrifugal pump comprises a mechanical seal bracket, wherein the mechanical seal bracket is fixed on a motor middle cover, a motor end cover is arranged on the front side of the motor middle cover, a motor front cover is arranged on the front side of the motor end cover, a main shaft is arranged in the mechanical seal bracket, a shaft sleeve, a secondary impeller, a friction ring A, a primary impeller and an inducer are sequentially sleeved on the main shaft from the back to the front, the primary impeller is in direct contact with the main shaft, the secondary impeller is not in contact with the main shaft, a secondary guide vane is arranged at the outlet of the secondary impeller, a one-way channel structure is arranged at the outlet of the secondary guide vane, a primary guide vane is arranged at the outlet of the primary impeller, the secondary guide vane is located between the motor middle cover and the motor end cover, the primary guide vane is located between the motor end cover and the motor front cover, a friction ring D matching the friction ring A is arranged at the front end of the secondary impeller, and the The motor end cover is provided with a motor end cover channel A and a motor end cover channel B, the rear end of the motor end cover channel A is connected to the secondary guide vane outlet area, the motor front cover is provided with a first regulating device for controlling the first-stage guide vane outlet position to be connected or blocked with the motor end cover channel, and a second regulating device for controlling the first-stage guide vane outlet position to be connected or blocked with the secondary impeller inlet, a piston cavity is provided on the rear side of the motor end cover, the front end of the motor end cover channel B is connected to the first-stage guide vane anti-guide vane area, and the rear end is connected to the piston cavity, a cover ring for sealing the piston cavity is provided in the motor end cover, a piston is provided in the piston cavity, the piston rod of the piston contacts the secondary impeller after passing through the cover ring, the bottom of the piston is connected to one end of a spring, and the other end of the spring is connected to the bottom of the piston cavity.

[0006] The first adjustment device includes an adjustment cover A, which passes through the motor end cover and the motor front cover. The adjustment cover A is provided with an adjustment cover A channel. When the adjustment cover A channel is in different positions, the adjustment cover A channel is connected to or blocked from the front end of the motor end cover channel A.

[0007] The cross-sectional shape of the contact position between the regulating cover A channel and the motor end cover channel A is an arc-shaped structure arranged oppositely.

[0008] The second adjusting device includes an adjusting cover B, which passes through the motor front cover, and is fitted and sealed with the first-stage guide vane outlet. The rear side of the adjusting cover B is fitted and sealed with the motor end cover. An adjusting cover B channel is provided in the adjusting cover B, and an adjusting cover C is provided in the adjusting cover B channel. An adjusting cover C channel is provided in the adjusting cover C. When the adjusting cover C channel is in different positions, the adjusting cover C channel is connected to or blocked from the inlet of the second-stage impeller.

[0009] The cross-sectional shapes of the regulating cover B channel and the regulating cover C channel are cross-shaped.

[0010] The one-way channel structure comprises a secondary guide vane stopper, wherein the secondary guide vane stopper is fixed at the secondary guide vane outlet, a stopper channel is arranged in the secondary guide vane stopper, and a one-way valve is arranged in the stopper channel.

[0011] A friction ring C is fixed to the inner side of the rear ring of the secondary impeller through a fastener, and the secondary impeller is positioned through the friction ring C and the friction ring B installed on the mechanical seal bracket.

[0012] A working method of a fast switching structure of a single-stage and multi-stage centrifugal pump comprises the following steps:

[0013] When it is necessary to use it as a single-stage pump, adjust the positions of the regulating cover B and the regulating cover C so that the regulating cover B channel and the regulating cover C channel are connected at the outlet of the first-stage guide vane, and the regulating cover B channel and the regulating cover C channel are blocked at the anti-guide vane flow channel of the first-stage guide vane;

[0014] Adjust the position of the adjusting cover A so that the channel of the adjusting cover A is connected with the connecting position of the channel A of the motor end cover;

[0015] The liquid flow passes through the inducer, the first-stage impeller, the first-stage guide vane, the regulating cover B channel, the regulating cover C channel, the regulating cover B channel, the first-stage guide vane outlet area, the regulating cover A channel, the motor end cover channel A and the second-stage guide vane outlet area in sequence;

[0016] There is no liquid flow passing through the secondary impeller and the secondary guide vane, and the axial force on the secondary impeller is insufficient to push the secondary impeller to drive the friction ring D forward. At this time, the friction ring A and the friction ring D are not in contact, and the secondary impeller does not rotate. The piston is extended backward by the spring force and contacts the secondary impeller, further overcoming the forward movement trend caused by the secondary impeller's own gravity and other reasons;

[0017] When a multi-stage pump is required, adjust the positions of the regulating cover B and the regulating cover C so that the regulating cover B channel and the regulating cover C channel are connected at the first-stage guide vane outlet position, and the regulating cover B channel and the regulating cover C channel are connected at the first-stage guide vane anti-guide vane flow channel position;

[0018] Adjust the position of the adjusting cover A so that the connection between the adjusting cover A channel and the motor end cover channel A is blocked;

[0019] The liquid flow passes through the inducer, the first-stage impeller, the first-stage guide vane, the regulating cover B channel, the regulating cover C channel, the regulating cover B channel, the first-stage guide vane outlet area, the regulating cover B channel, the regulating cover C channel, the regulating cover B channel, the first-stage guide vane anti-guide vane flow channel, the second-stage impeller, the second-stage guide vane, the block channel and the second-stage guide vane outlet area in sequence;

[0020] At this time, liquid flows through the motor end cover channel B into the rodless chamber of the piston chamber. The piston overcomes the spring force generated by the spring due to the liquid pressure and moves forward, and no longer provides axial backward force to the secondary impeller. At this time, liquid flows through the secondary impeller and the secondary guide vane. The axial force on the secondary impeller is sufficient to push the secondary impeller and drive the friction ring D to move forward together. That is, at this time, the friction ring A and the friction ring D are in contact, and the friction ring A drives the secondary impeller and the main shaft to rotate.

[0021] Beneficial effects of the present invention: The present invention provides a rapid switching structure for a single-stage and multi-stage centrifugal pump and a working method thereof, wherein an adjusting cover A penetrates a motor end cover and a motor front cover, an adjusting cover B penetrates a motor front cover, an adjusting cover B channel is provided in the adjusting cover B, and an adjusting cover C is provided in the adjusting cover B channel. By adjusting the relative positions of the adjusting cover A, the adjusting cover B and the adjusting cover C, rapid switching of the single-stage / multi-stage centrifugal pump structure can be achieved, ensuring that the pump unit can replace the single / multi-stage impeller in time to match the best environmental working conditions, saving manpower and financial costs on site. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of a fast switching structure of a single-stage and multi-stage centrifugal pump of the present invention;

[0023] Figure 2 for Figure 1 The enlarged structural diagram of position Ⅰ in the middle;

[0024] Figure 3 for Figure 1 The enlarged structural diagram of the middle part Ⅱ;

[0025] Figure 4 for Figure 1 Schematic diagram of the enlarged structure at position III;

[0026] Figure 5 for Figure 1 The enlarged structural diagram of the middle IV;

[0027] Figure 6 It is a cross-sectional position diagram of the regulating cover A, regulating cover B and regulating cover C in the use state of the single-stage impeller in the present invention;

[0028] Figure 7 It is a cross-sectional position diagram of the regulating cover A, regulating cover B and regulating cover C when the multi-stage impeller of the present invention is in use;

[0029] Figure 8 It is a flow direction diagram of the liquid when the single-stage impeller of the present invention is in use;

[0030] Fig. 9 This is a flow diagram of the liquid flow when the multi-stage impeller of the present invention is in use.

[0031] The reference numerals in the figure are as follows: Among them: 1-inducer; 2-first-stage impeller; 3-first-stage guide vane; 4-friction ring A; 5-second-stage impeller; 6-second-stage guide vane; 7-main shaft; 8-machine seal bracket; 9-shaft sleeve; 10-motor middle cover; 11-second-stage guide vane stopper; 12-check valve; 13-motor end cover; 14-motor front cover; 15-adjusting cover A; 16-adjusting cover B; 17-adjusting cover C; 18-friction ring B; 19-friction ring C; 20-friction ring D; 21-piston; 22-cover ring; 23-spring; 1101-stopper channel; 1301-motor end cover channel A; 1302-motor end cover channel B; 1303-piston chamber; 1501-adjusting cover A channel; 1601-adjusting cover B channel; 1701-adjusting cover C channel. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the protection scope of the present invention.

[0033] In this embodiment, the up-down, front-back, and back-forth directions refer to the up-down, right-left directions on the drawing, the axial direction is the direction of the motor shaft, and the radial direction is perpendicular to the motor shaft. Figures 1 to 5 As shown, the present invention discloses a fast switching structure of a single-stage and multi-stage centrifugal pump, including a mechanical seal bracket 8, the mechanical seal bracket 8 is fixed on the motor middle cover 10, the motor middle cover 10 is provided with a motor end cover 13 on the front side, the motor end cover 13 is provided with a motor front cover 14 on the front side, the mechanical seal bracket 8 is provided with a main shaft 7, and the main shaft 7 is sequentially sleeved with a shaft sleeve 9, a secondary impeller 5, a friction ring A4, a primary impeller 2 and an inducer 1 from the back to the front direction. The friction ring C19 is fixed to the inner side of the rear ring of the secondary impeller 5 by fasteners, and the secondary impeller 5 is positioned by the friction ring C19 and the friction ring B18 installed on the mechanical seal bracket 8.

[0034] The outlet of the secondary impeller 5 is provided with a secondary guide vane 6, and a one-way channel structure is provided at the outlet of the secondary guide vane 6. The one-way channel structure allows the flow direction to flow from the secondary guide vane 6 flow channel to the outlet area of ​​the secondary guide vane 6. In this embodiment, the one-way channel structure includes a secondary guide vane stopper 11, which is fixed at the outlet of the secondary guide vane 6, and a stopper channel 1101 is provided in the secondary guide vane stopper 11, and a one-way valve 12 is provided in the stopper channel 1101.

[0035] A first-stage guide vane 3 is provided at the outlet of the first-stage impeller 2, a second-stage guide vane 6 is located between the motor middle cover 10 and the motor end cover 13, the first-stage guide vane 3 is located between the motor end cover 13 and the motor front cover 14, and a friction ring D20 cooperating with the friction ring A4 is provided at the front end of the second-stage impeller 5.

[0036] The primary impeller 2 is in direct contact with the main shaft 7, and the rotation of the main shaft 7 directly drives the primary impeller 2 to rotate. The secondary impeller 5 is not in contact with the main shaft 7. Only when the friction ring A4 contacts the friction ring D20, the main shaft 7 cooperates with the friction ring A4 and the friction ring D20 to indirectly drive the secondary impeller 5 to rotate. The motor end cover 13 is provided with a motor end cover channel A1301 and a motor end cover channel B1302. The rear end of the motor end cover channel A1301 is connected to the outlet area of ​​the secondary guide vane 6. The motor front cover 14 is provided with a first regulating device for controlling the outlet position of the primary guide vane 3 to be connected or blocked with the motor end cover channel A1301, and a second regulating device for controlling the outlet position of the primary guide vane 3 to be connected or blocked with the inlet of the secondary impeller 5.

[0037] In this embodiment, the first adjustment device includes an adjustment cover A15, which passes through the motor end cover 13 and the motor front cover 14. The adjustment cover A channel 1501 is opened on the adjustment cover A15, and the adjustment cover A channel 1501 is selectively connected with the front end of the motor end cover channel A1301. The cross-sectional shape of the contact position between the adjustment cover A channel 1501 and the motor end cover channel A1301 is an arc structure (approximately crescent-shaped) arranged oppositely.

[0038] In this embodiment, the second regulating device includes an regulating cover B16, the regulating cover B16 penetrates the motor front cover 14, the regulating cover B16 is sealed with the outlet of the first-stage guide vane 3, the rear side of the regulating cover B16 is sealed with the motor end cover 13, the regulating cover B16 is provided with an regulating cover B channel 1601, the regulating cover B channel 1601 is provided with an regulating cover C17, the regulating cover C channel 1701 is provided in the regulating cover C17, and the regulating cover C channel 1701 is selectively connected with the inlet of the second-stage impeller 5. The cross-sectional shape of the regulating cover B channel 1601 and the regulating cover C channel 1701 is a cross.

[0039] like Figure 6 As shown, in the single-stage impeller of the present invention, when in use, the AA position is in a blocked state, and the BB position and the CC position are in a connected state, as shown in FIG. Figure 7 As shown, when the multi-stage impeller of the present invention is in use, the AA position and the BB position are in a connected state, and the CC position is in a blocked state.

[0040] A piston cavity 1303 is provided at the rear side of the motor end cover 13. The front end of the motor end cover channel B1302 is connected to the anti-guide vane area of ​​the first-stage guide vane 3, and the rear end is connected to the piston cavity 1303. A cover ring 22 for sealing the piston cavity 1303 is provided in the motor end cover 13. The cover ring 22 forms a closed cavity for the piston cavity 1303. A piston 21 is provided in the piston cavity 1303. The piston 21 is located in the piston cavity 1303 and divides the piston cavity into a rod cavity and a rodless cavity, wherein the rod cavity is close to the side of the second-stage impeller 5. The spring 23 is located in the rodless cavity, one end of which is connected to the piston 21, and the other end is connected to the bottom of the rodless cavity. The piston rod passes through the cover ring 22. When there is no additional liquid pressure applied to the rodless cavity, the piston rod is extended to the rear end by the spring force to support the fixation of the axial position of the front side of the second-stage impeller 5.

[0041] The working method of the present invention is: when it is needed to be used as a single-stage pump, the positions of the regulating cover B16 and the regulating cover C17 are adjusted so that the regulating cover B channel 1601 and the regulating cover C channel 1701 are located at the outlet position of the first-stage guide vane 3 and are connected ( Figure 6 As shown in the BB polishing surface, the regulating cover B channel 1601 and the regulating cover C channel 1701 are located at the position of the first-stage guide vane 3 anti-guide vane flow channel and are blocked ( Figure 6 (shown in the AA polished surface).

[0042] Adjust the position of the adjustment cover A15 so that the channel 1501 of the adjustment cover A is connected to the connection position of the motor end cover channel A1301 ( Figure 6 (as shown in the CC polishing surface).

[0043] At this time, the flow direction is Figure 8 As shown by the middle arrow: inducer 1 - first-stage impeller 2 - first-stage guide vane 3 - regulating cover B channel 1601 (first-stage guide vane 3 outlet position) - regulating cover C channel 1701 (first-stage guide vane 3 outlet position) - regulating cover B channel 1601 (first-stage guide vane 3 outlet position) - first-stage guide vane 3 outlet area - regulating cover A channel 1501 - motor end cover channel A1301 - second-stage guide vane 6 outlet area.

[0044] At this time, there is no liquid flow passing through the secondary impeller 5 and the secondary guide vane 6, and the axial force on the secondary impeller 5 is insufficient to push the secondary impeller 5 to drive the friction ring D20 to move forward together, that is, at this time, the friction ring A4 and the friction ring D20 are not in contact, and the secondary impeller 5 does not rotate. In addition, the piston 21 extends backward under the action of the spring 23 and contacts the secondary impeller 5, further overcoming the forward movement trend caused by the secondary impeller 5's own gravity and other reasons.

[0045] When a multi-stage pump is required, adjust the positions of the regulating cover B16 and the regulating cover C17 so that the regulating cover B channel 1601 and the regulating cover C channel 1701 are located at the outlet of the first-stage guide vane 3 and connected ( Figure 7As shown in the BB polishing surface, the regulating cover B channel 1601 and the regulating cover C channel 1701 are located at the anti-guide vane flow channel position of the first-stage guide vane 3 and are connected ( Figure 7 (shown in the AA polished surface).

[0046] Adjust the position of the adjustment cover A15 to block the connection between the adjustment cover A channel 1501 and the motor end cover channel A1301 ( Figure 7 (as shown in the CC polishing surface).

[0047] At this time, the flow direction is Fig. 9 As indicated by the middle arrow: inducer 1 - first-stage impeller 2 - first-stage guide vane 3 - regulating cover B channel 1601 (first-stage guide vane 3 outlet position) - regulating cover C channel 1701 (first-stage guide vane 3 outlet position) - regulating cover B channel 1601 (first-stage guide vane 3 outlet position) - first-stage guide vane 3 outlet area - regulating cover B channel 1601 (first-stage guide vane 3 anti-guide vane flow channel position) - regulating cover C channel 1701 (first-stage guide vane 3 anti-guide vane flow channel position) - regulating cover B channel 1601 (first-stage guide vane 3 anti-guide vane flow channel position) - first-stage guide vane 3 anti-guide vane flow channel - second-stage impeller 5 - second-stage guide vane 6 - block channel 1101 - second-stage guide vane 6 outlet area.

[0048] At this time, liquid flows through the motor end cover channel B1302 and flows into the rodless cavity of the piston cavity 1303. The piston 21 overcomes the spring force generated by the spring 23 due to the liquid pressure and moves forward, and no longer provides an axial backward force to the secondary impeller 5. At this time, liquid flows through the secondary impeller 5 and the secondary guide vane 6. The axial force on the secondary impeller 5 is sufficient to push the secondary impeller 5 and drive the friction ring D20 to move forward together. That is, at this time, the friction ring A4 is in contact with the friction ring D20, and the friction ring A4 drives the secondary impeller 5 and the main shaft 7 to rotate.

[0049] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A fast switching structure for single-stage and multi-stage centrifugal pumps, characterized in that: The invention comprises a mechanical seal bracket (8), wherein the mechanical seal bracket (8) is fixed on a motor middle cover (10), a motor end cover (13) is arranged on the front side of the motor middle cover (10), a motor front cover (14) is arranged on the front side of the motor end cover (13), a main shaft (7) is arranged in the mechanical seal bracket (8), and a shaft sleeve (9), a secondary impeller (5), a friction ring A (4), a primary impeller (2) and an inducer (1) are sequentially sleeved on the main shaft (7) from the back to the front, the primary impeller (2) is in direct contact with the main shaft (7), and the secondary impeller (5) is in direct contact with the main shaft (7). ), the outlet of the secondary impeller (5) is provided with a secondary guide vane (6), the outlet of the secondary guide vane (6) is provided with a one-way channel structure, the outlet of the primary impeller (2) is provided with a primary guide vane (3), the secondary guide vane (6) is located between the motor middle cover (10) and the motor end cover (13), the primary guide vane (3) is located between the motor end cover (13) and the motor front cover (14), the front end of the secondary impeller (5) is provided with a friction ring D (20) that cooperates with the friction ring A (4), and the motor end cover (13) is provided with a motor end cover passage A channel A (1301) and a motor cover channel B (1302), the rear end of the motor cover channel A (1301) being connected to the outlet area of ​​the secondary guide vane (6), the motor front cover (14) being provided with a first regulating device for controlling the outlet position of the primary guide vane (3) to be connected to or blocked from the motor cover channel A (1301) and a second regulating device for controlling the outlet position of the primary guide vane (3) to be connected to or blocked from the inlet of the secondary impeller (5), the rear side of the motor cover (13) being provided with a piston chamber (1303), the motor The front end of the end cover channel B (1302) is connected to the anti-guide vane region of the first-stage guide vane (3), and the rear end is connected to the piston chamber (1303). A cover ring (22) for sealing the piston chamber (1303) is arranged in the motor end cover (13). A piston (21) is arranged in the piston chamber (1303). The piston rod of the piston (21) contacts the second-stage impeller (5) after passing through the cover ring (22). The bottom of the piston (21) is connected to one end of a spring (23), and the other end of the spring (23) is connected to the bottom of the piston chamber (1303). The first adjustment device comprises an adjustment cover A (15), the adjustment cover A (15) passing through the motor end cover (13) and the motor front cover (14), the adjustment cover A (15) being provided with an adjustment cover A channel (1501), and when the adjustment cover A channel (1501) is in different positions, the adjustment cover A channel (1501) is connected to or blocked from the front end of the motor end cover channel A (1301); The second regulating device comprises a regulating cover B (16), the regulating cover B (16) passing through the motor front cover (14), the regulating cover B (16) and the outlet of the first-stage guide vane (3) being fitted and sealed, the rear side of the regulating cover B (16) and the motor end cover (13) being fitted and sealed, the regulating cover B (16) being provided with a regulating cover B channel (1601), the regulating cover B channel (1601) being provided with a regulating cover C (17), the regulating cover C (17) being provided with a regulating cover C channel (1701), and when the regulating cover C channel (1701) is in different positions, the regulating cover C channel (1701) is connected to or blocked from the inlet of the second-stage impeller (5).

2. The fast switching structure of a single-stage and multi-stage centrifugal pump according to claim 1, characterized in that: The cross-sectional shape of the contact position between the regulating cover A channel (1501) and the motor end cover channel A (1301) is a relatively arranged arc-shaped structure.

3. The fast switching structure of a single-stage and multi-stage centrifugal pump according to claim 1, characterized in that: The cross-sectional shapes of the regulating cover B channel (1601) and the regulating cover C channel (1701) are cross-shaped.

4. The fast switching structure of a single-stage and multi-stage centrifugal pump according to claim 1, characterized in that: The one-way channel structure comprises a secondary guide vane stopper (11), the secondary guide vane stopper (11) being fixed at the outlet of the secondary guide vane (6), a stopper channel (1101) being provided in the secondary guide vane stopper (11), and a one-way valve (12) being provided in the stopper channel (1101).

5. The fast switching structure of a single-stage and multi-stage centrifugal pump according to claim 1, characterized in that: A friction ring C (19) is fixed to the inner side of the rear ring of the secondary impeller (5) via a fastener, and the secondary impeller (5) is positioned via the friction ring C (19) and a friction ring B (18) mounted on the mechanical seal bracket (8).

6. A method for operating the fast switching structure of the single-stage and multi-stage centrifugal pumps according to claim 1, characterized in that: The following steps are involved: When it is necessary to use the pump as a single-stage pump, the positions of the regulating cover B (16) and the regulating cover C (17) are adjusted so that the regulating cover B channel (1601) and the regulating cover C channel (1701) are connected at the outlet of the first-stage guide vane (3), and the regulating cover B channel (1601) and the regulating cover C channel (1701) are blocked at the anti-guide vane flow channel of the first-stage guide vane (3); Adjust the position of the adjustment cover A (15) so that the channel (1501) of the adjustment cover A is connected to the connection position of the channel A (1301) of the motor end cover; The liquid flow sequentially passes through the inducer (1), the first-stage impeller (2), the first-stage guide vane (3), the regulating cover B channel (1601), the regulating cover C channel (1701), the regulating cover B channel (1601), the first-stage guide vane (3) outlet area, the regulating cover A channel (1501), the motor end cover channel A (1301) and the second-stage guide vane (6) outlet area; There is no liquid flow passing through the secondary impeller (5) and the secondary guide vane (6), and the axial force on the secondary impeller (5) is insufficient to push the secondary impeller (5) and the friction ring D (20) to move forward. At this time, the friction ring A (4) and the friction ring D (20) are not in contact, the secondary impeller (5) does not rotate, and the piston (21) is extended backward by the spring (23) to contact the secondary impeller (5), further overcoming the forward movement tendency caused by the secondary impeller (5)'s own gravity and other reasons; When a multi-stage pump is required, the positions of the regulating cover B (16) and the regulating cover C (17) are adjusted so that the regulating cover B channel (1601) and the regulating cover C channel (1701) are connected at the outlet position of the first-stage guide vane (3), and the regulating cover B channel (1601) and the regulating cover C channel (1701) are connected at the anti-guide vane flow channel position of the first-stage guide vane (3); Adjust the position of the adjustment cover A (15) so that the connection position between the adjustment cover A channel (1501) and the motor end cover channel A (1301) is blocked; The liquid flow sequentially passes through the inducer (1), the first-stage impeller (2), the first-stage guide vane (3), the regulating cover B channel (1601), the regulating cover C channel (1701), the regulating cover B channel (1601), the first-stage guide vane (3) outlet area, the regulating cover B channel (1601), the regulating cover C channel (1701), the regulating cover B channel (1601), the first-stage guide vane (3) reverse guide vane flow channel, the second-stage impeller (5), the second-stage guide vane (6), the block channel (1101) and the second-stage guide vane (6) outlet area; At this time, liquid flows through the motor end cover channel B (1302) and flows into the piston chamber (1303). The piston (21) overcomes the spring force generated by the spring (23) due to the liquid pressure and moves forward and no longer contacts the secondary impeller (5). At this time, liquid flows through the secondary impeller (5) and the secondary guide vane (6). The axial force on the secondary impeller (5) is sufficient to push the secondary impeller (5) and the friction ring D (20) to move forward together. That is, at this time, the friction ring A (4) and the friction ring D (20) are in contact, and the friction ring A (4) drives the secondary impeller (5) and the main shaft (7) to rotate.

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