A water feeding pump or a fertilizer applying pump for a pump station of a fertilization and irrigation system, wherein the water feeding pump (2) or the fertilizer applying pump (3) is a centrifugal pump, the centrifugal pump comprises a pump body portion (6), the pump body portion comprises a volute (9) and an impeller, the impeller is mounted in the volute and comprises a front disc (12), a rear disc (13), a plurality of main blades (14), and an inlet ring (15), the plurality of main blades are distributed along a circumferential direction and connected between the front disc and the rear disc, a plurality of back blades (18) distributed along the circumferential direction are disposed on a back surface of the rear disc, and the impeller is mounted on a rotating shaft (10), wherein an auxiliary rotating disc (11) is disposed between the impeller and a rear side wall of the volute, the auxiliary rotating disc is a rotating member and is driven by the back blades of the impeller to rotate;
- the auxiliary rotating disc (11) comprises a first radial disc (19), an axial ring (20), and a second radial disc (21) which are sequentially connected, a support cylinder (22) is disposed at a center of the first radial disc, and a plurality of auxiliary blades (23) distributed along the circumferential direction are disposed on a side face, close to the back blades (18), of the first radial disc, the position of the auxiliary blades corresponds to the position of the back blades, a radial length of the auxiliary blades is equal to a radial length of the back blades, the support cylinder is rotatably connected to the rotating shaft (10) and/or a volute cylinder portion (25) of the volute, a plurality of communication grooves (24) distributed along the circumferential direction are disposed on the first radial disc, the communication grooves are in communication with a first chamber that is between the rear disc (13) of the impeller and the auxiliary rotating disc and a second chamber that is between the auxiliary rotating disc and the rear side wall of the volute, and the second radial disc is disposed in a diffuser that is between an outer circumferential surface of the impeller and a pressurized water chamber of the volute;
- a first injection hole is disposed on the rear side wall of the volute, the first injection hole is in communication with a second injection hole on an inlet pipe (31) of the volute through an injection pipeline (32), the second injection hole is used for injecting a high-pressure liquid to an inlet end of the impeller, and a control valve is disposed on the injection pipeline;
- an outer circumferential surface of the support cylinder (22) is rotatably connected to an inner circumferential surface of the volute cylinder portion (25) of the volute (9) through one or more first bearings (26), an inner circumferential surface of the support cylinder is rotatably connected to an outer circumferential surface of the rotating shaft (10) through one or more second bearings (27), a first channel is formed between the outer circumferential surface of the support cylinder and the volute cylinder portion, and a second channel is formed between the inner circumferential surface of the support cylinder and the rotating shaft;
- and a plurality of radial holes (28) and an axial hole (29) are disposed on the rotating shaft (10), wherein the plurality of radial holes are distributed along the circumferential direction, the axial hole penetrates through an end of the rotating shaft located at an impeller cavity, and the radial holes are in communication with the axial hole and the impeller cavity;
- and a protruding step segment is disposed on the rotating shaft (10), a spiral groove (30) is disposed on the protruding step segment, the protruding step segment is disposed at a position corresponding to a right end of the support cylinder (22), the protruding step segment is disposed between the one or more second bearings (27) and the radial holes (28), and the spiral groove is used for improving fluidity of liquid in the second channel flowing to a side of the radial holes.