The main flow parts of a segmented multistage centrifugal pump are suction chamber, impeller and pressurized water 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 pressurized water chamber mainly has three forms of spiral pressurized water chamber (volute type), guide vane and space guide vane; the impeller is the most advanced pump. The important working element is the core of the flow component. The impeller is composed of a cover plate and a middle blade. The pump works on the liquid through the impeller to increase its energy.
(1) Suction chamber: Located in front of the impeller inlet, its function is to introduce liquid from the suction pipe into the impeller, requiring less flow loss of the liquid flowing through the suction chamber, and making the velocity distribution of the liquid more even when flowing into the impeller;
(2) Impeller: It is the work component in the centrifugal pump. The requirement for the impeller is to obtain higher energy per unit weight of liquid with minimal loss;
(3) Volute: located behind 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.
The main flow component impeller of segmented 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 function of the pump impeller is to transfer the energy input from the prime mover to the liquid. The shape and size of the pump impeller are closely related to the pump performance. Water pump impellers can generally be divided into single-suction type and double-suction type. Single-suction impellers absorb water on one side, and the impellers of small-flow pumps are mostly of this form. The double-suction impeller sucks water on both sides, and the large-flow water pump impeller adopts double-suction impeller.
The impeller is divided into three categories according to the direction of the liquid outflow:
(1) Radial flow impeller (centrifugal impeller) liquid flows out of the impeller in a direction perpendicular to the axis.
(2) Diagonal flow impeller (mixed flow impeller) The liquid flows out of the impeller along the inclined direction of the axis.
(3) The direction of liquid flow in 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 cover plate:
(1) Enclosed impeller.
(2) Open impeller.
(3) Semi-open impeller. The enclosed impeller is widely used, and the aforementioned single-suction impeller and double-suction impeller all belong to this form.
There are three main structural forms of water pump impellers: those with front and rear cover plates are called closed impellers. Only the rear cover is called a semi-open impeller. The one without front and rear covers is called an open impeller. In addition, the structure of the blades can also be divided into 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 use of twisted blades can reduce the load of the blades, improve the suction performance of the centrifugal pump, and improve the anti-cavitation ability, but the manufacturing is more difficult and the cost is higher. Centrifugal pumps used in water pump impellers for refining and chemical industries require that the impellers be cast or fully welded integral water pump impellers. Welded pump impellers have been developed in recent years, and are mostly used for special centrifugal pumps made of metal materials with poor casting properties, such as iron and its alloys. The geometric accuracy and surface finish of the welded water pump impeller are better than those of the cast impeller, which is beneficial to improve the efficiency of the centrifugal pump. Generally, closed-type water pump impellers have 2-12 back-curved blades, which have high operating efficiency. For example, the aforementioned single-suction and double-suction centrifugal pumps use this impeller. Among them, the single-stage single-suction centrifugal pump impeller has axial force, so some impellers have balance holes at the roots of the blades.
The structure of water pump impeller and blade:
Half-open and open impellers have fewer blades, generally 2 to 5, and are mostly used for pumping slurry or granular liquid or sewage, such as the impeller of a sewage pump. In the field of sewage discharge, in order to ensure that the conveying medium containing solid particles, fibers and other entanglements is blocked, the runner-type impeller is often used. The impeller material of the water pump must have sufficient mechanical strength, and a certain degree of wear resistance and corrosion resistance. According to the requirements of the conveying medium, cast iron, cast steel, stainless steel or, for example, oil pump products, are usually used for conveying flammable and explosive oil with bronze impellers.
Types of suction chambers for the main flow-through components of segmented multistage centrifugal pumps
The suction chamber of the water pump is located in front of the impeller, and its function is to guide the liquid to the impeller. There are three forms: straight cone, elbow and spiral. as the picture shows:
The main flow-passing parts of the segmented multi-stage centrifugal pump pressurized water chamber type
The pressurized water chamber is located on the periphery of the impeller, sometimes also called the pump body. Its function is to collect the liquid flowing out of the impeller, convert most of the kinetic energy into pressure energy, and then send it to the discharge pipe. The type of pressurized water chamber is shown in the figure:
The materials of the suction chamber and the pressurized water chamber should have sufficient mechanical strength, wear resistance and corrosion resistance. Cast iron, cast steel and stainless steel are generally used for casting.
