What is the working principle of single-stage centrifugal water pump structure?

　　Single-stage centrifugal water pumps are more widely used in the water treatment industry, which is due to its performance with a wide range of use (including flow, pressure head and the nature of the medium of the loss of welcoming), small size, simple structure, easy to operate, uniform flow, long life, acquisition and operation costs are lower and other outstanding advantages.

　　The basic structure of single-stage centrifugal water pump

　　Single-stage centrifugal water pump is the basic components of the high-speed rotation of the impeller and the fixed snail-shaped pump casing, with a number of (usually 4 to 12) backward curved vane of the impeller is fastened to the pump shaft, and with the pump shaft driven by the motor for high-speed rotation.

　　Impeller is directly on the pump liquid work parts, for the centrifugal pump energy supply device, the suction port in the center of the pump casing is connected to the suction pipeline, the bottom of the suction pipeline is equipped with a one-way foot valve, the pump casing side of the discharge outlet is connected to the discharge pipeline equipped with a regulating valve.

　　Working principle of single-stage centrifugal water pump

　　When the single-stage centrifugal water pump is started, the pump shaft drives the impeller to make high-speed rotary movement, forcing the pre-filled liquid rotation between the blades, under the action of centrifugal force of inertia, the liquid from the center of the impeller to the periphery of the radial movement.

　　Liquid in the flow through the impeller movement process has gained energy, static pressure energy increases, the flow rate increases, when the liquid leaves the impeller into the pump casing, due to the gradual expansion of the flow channel in the shell and deceleration, part of the kinetic energy into static pressure energy, and finally along the tangential flow into the discharge pipeline.

　　So the worm-shaped pump casing is not only a collection of liquid outflow from the impeller parts, but also a transfer device, when the liquid from the impeller center thrown to the periphery at the same time, the impeller center to form a low-pressure area, in the reservoir level and the impeller center of the total potential difference in the role of the impeller center, resulting in the liquid is sucked into the center of the impeller. Relying on the continuous operation of the impeller, the liquid will be continuously inhaled and discharged, the liquid in the centrifugal pump to obtain the mechanical energy is ultimately expressed in the static pressure energy increase.

　　It should be emphasized that, if the single-stage centrifugal pump before the start of the pump casing is not filled with liquid being transported, due to the low density of air, the impeller rotates after the centrifugal force generated by a small impeller center area is not enough to form a suction of the liquid in the reservoir of the low-pressure, and thus can not be transported despite the start of the single-stage centrifugal pump liquid. This indicates that the centrifugal pump has no self-priming ability, this phenomenon is called air binding.

　　Suction piping to install a one-way foot valve is to prevent the pump casing before the start of the liquid from the casing out of the air from the suction pipe into the pump casing will cause air binding.

　　1 single-stage centrifugal water pump impeller

　　Impeller is the key component of single-stage centrifugal water pump.

　　(1) According to its mechanical structure can be divided into closed, semi-closed and open three kinds of

　　Closed impeller is suitable for transporting clean liquids; semi-closed and open impeller is suitable for transporting suspensions containing solid particles, the efficiency of such pumps is low.

　　Closed and semi-closed impeller in operation, leaving the impeller part of the high-pressure liquid can be funneled into the impeller and the pump casing between the cavity, because the impeller front side of the liquid suction inlet pressure is low, so the liquid acts on the impeller before and after the side of the pressure is not the same, it produces an axial thrust directed to the side of the impeller suction port.

　　This force pushes the impeller to move to the suction port side, causing friction at the contact of the impeller and pump casing, causing pump vibration in serious cases, destroying the normal operation of the pump. In the impeller back cover plate drilling a number of small holes, can reduce the pressure difference between the two sides of the impeller, thus reducing the adverse effects of the axial thrust, but also reduces the efficiency of the pump. These small holes are called balance holes.

　　(2) according to the suction method can be divided into single suction impeller and double suction two kinds of different

　　Single suction impeller structure is simple, the liquid can only be inhaled from one side. Double suction impeller can be symmetrically inhaled from both sides of the impeller liquid, it not only has a larger suction capacity, and basically eliminates the axial thrust.

　　(3) According to the geometry of the blade on the impeller, the blade can be divided into backward curved, radial and forward curved three kinds, due to the backward curved blade is conducive to the conversion of the kinetic energy of the liquid into static pressure energy, so it is widely used.

　　2 single-stage centrifugal pump guide wheel

　　In order to reduce the impeller to leave the liquid directly into the pump casing due to the impact of the energy loss caused by the impeller and the pump casing is sometimes installed between a fixed and immobile with a vane guide wheel. The vane in the guide wheel makes the liquid entering the pump casing gradually turn and the flow channel expand continuously, so that part of the kinetic energy is effectively converted into static pressure energy. Multi-stage centrifugal pumps are usually installed guide wheel.

　　Snail-shaped pump casing, impeller on the back of the curved blades and guide wheel can improve the conversion rate of kinetic energy to static pressure energy, so they can be regarded as energy transfer device.

　　3 Shaft sealing device

　　As the pump shaft rotates and the pump casing is fixed, there must be a certain gap between the shaft and the pump casing contact. In order to avoid the pump high pressure liquid leakage along the gap, or to prevent the outside air from the opposite direction into the pump.