Introduction of wet parts of multistage centrifugal pump
The wet parts of the multi-stage centrifugal pump are suction chamber, impeller and pressure chamber. The suction chamber is located in front of the water inlet of the impeller and plays the role of guiding the liquid to the impeller; the pressure water chamber mainly has three forms of spiral pressure water chamber (volute type), guide vane and space guide vane; the impeller is the most The important working element is the core of the over-current component. The impeller consists of a cover plate and a blade in the middle. The pump's work on the liquid through the impeller increases its energy.
(1) Suction chamber: Located before the inlet of the impeller, its function is to introduce liquid from the suction pipe to the impeller. It is required that the flow loss of liquid flowing through the suction chamber is small, and the velocity distribution when the liquid flows into the impeller is more uniform;
(2) Impeller: It is the working part in the centrifugal pump. The requirement of the impeller is to make the unit weight of liquid obtain higher energy with the smallest loss;
(3) Volute: It is located after the outlet of the impeller. Its function is to collect the liquid flowing out of the impeller and send it to the lower impeller or into the discharge pipe according to certain requirements.
Impeller of the main flow parts of the multistage centrifugal pump
The pump impeller is an important working part of the pump, and its shape, size, processing technology, etc. have a decisive influence on the performance of the pump. The role of the pump impeller is to transfer the energy input by the prime mover to the liquid. The shape and size of the pump impeller are closely related to the performance of the pump. The pump impeller can be generally divided into two types: single suction type and double suction type. The single-suction impeller absorbs water unilaterally, and the impeller of the small-flow pump is mostly in this form. The double-suction impeller absorbs water on both sides, and the high-flow pump impeller adopts double-suction impeller.
The impeller is divided into three categories according to the direction of liquid outflow:
(1) Radial impeller (centrifugal impeller) liquid flows out of the impeller in a direction perpendicular to the axis.
(2) The oblique-flow impeller (mixed-flow impeller) liquid flows out of the impeller along the direction in which the axis is inclined.
(3) The flow direction of the axial flow impeller is parallel to the axis.
The impeller is divided into two categories according to the way of inhalation:
(1) Single suction impeller (that is, the impeller sucks liquid from one side).
(2) Double suction impeller (that is, the impeller sucks liquid from both sides).
The impeller is divided into three categories according to the form of the cover:
(1) Closed impeller.
(2) Open impeller.
(3) Semi-open impeller. Among them, the closed type impeller is widely used. The aforementioned single suction impeller and double suction impeller belong to this form.
There are three main types of pump impellers: those with front and rear covers are called closed impellers. Only the back cover is called a semi-open impeller. The open impeller without front and rear covers. In addition, the structure of the blade can also be divided into two kinds of cylindrical blades and twisted blades. The blades of the centrifugal pump impeller are generally backward curved blades. There are two types of blades, cylindrical and twisted. The application of twisted blades can reduce the load of the blades, and can improve the suction performance of the centrifugal pump and improve the anti-cavitation ability, but it is more difficult to manufacture and the cost is higher. Water pump impeller centrifugal pumps for oil refining and chemical engineering require the impeller to be an integral water pump impeller cast or fully welded. Welded water pump impellers have been developed in recent years, and are mostly used for casting metal materials with poor performance, such as iron and its alloys, and manufacturing special centrifugal pumps for chemical industry. The geometric accuracy and surface finish of the welded water pump impeller are better than the cast impeller, which is beneficial to improve the efficiency of the centrifugal pump. Generally, the closed pump impeller has 2-12 backward-curved blades, which have high operating efficiency. Such impellers are used in the single-suction and double-suction centrifugal pumps mentioned above. The impeller of the single-stage single-suction centrifugal pump has axial force, so some impellers have balancing holes at the roots of the blades.
Structure of pump impeller and blade:
The number of blades of semi-open and open impellers is relatively small, generally 2 to 5 pieces, and most of them are used to pump slurry liquid or sewage, such as the impeller of sewage pumps. In the field of sewage disposal, in order to ensure that the transport of media containing solid particles, fibers and other winding materials is clogged, flow channel impellers are often used. The material of the pump impeller must have sufficient mechanical strength and a certain degree of wear resistance and corrosion resistance. According to the requirements of the transmission medium, cast iron, cast steel, stainless steel or oil pump products are usually used to transport flammable and explosive oil. Bronze impellers are used.
