Centrifugal pump

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1. What is a centrifugal pump? Briefly describe the working principle of a centrifugal pump? A pump that uses the centrifugal force generated by the rotation of the impeller to transport liquid is called a centrifugal pump. Its working principle is as follows: The electric motor drives the impeller to rotate at high speed, generating centrifugal force. Due to this centrifugal force, the liquid is forced into the side channels and discharged from the pump, or it enters the next stage of impellers, thereby reducing the pressure at the inlet of the impeller. This creates a pressure difference with the pressure acting on the liquid being drawn in, and it is this pressure difference that draws the liquid into the pump. As the centrifugal pump keeps rotating, liquid is continuously drawn in and discharged. 2. What are the advantages and disadvantages of centrifugal pumps compared to other types of pumps? Compared with other types of pumps, centrifugal pumps have a series of advantages such as simple structure, small size, light weight, stable flow rate, ease of manufacture, and convenience in maintenance. However, centrifugal pumps are less suitable for high-viscosity liquids, as well as situations involving low flow rates and high pressures. Additionally, they usually require priming before starting up; these are their shortcomings. 3. How are different types of pumps classified? There are several methods for classifying pumps: 1. By principle: they can be divided into positive displacement pumps, vane pumps, jet pumps, etc. Positive displacement pumps are pumps that transport liquids by changing the volume of the working chamber, such as reciprocating pumps, rotor pumps, and gear pumps. Vane pumps are pumps that use the rotation of impellers to transport liquids, such as centrifugal pumps and axial flow pumps. A jet pump relies on the energy of a working fluid to transport another fluid; examples include jet pumps and water lifters. 2. Classified by prime mover: they can be divided into steam turbines, steam reciprocating pumps, electric centrifugal pumps, and electric reciprocating pumps. 3. Classified by the conveying medium: there are water pumps, oil pumps, acid pumps, and alkali pumps. 4. Classified by the installation position of the shaft: there are vertical pumps and horizontal pumps. 5. Classified by the temperature of the conveyed medium ； There are cold medium pumps and hot medium pumps. 6. Classified by the number of impeller stages: there are single-stage pumps, two-stage pumps, and multi-stage pumps. 7. Classified by the impeller feeding method: there are single-suction and double-suction types. 8. Classified by the type of pump casing joint: there are horizontal split-type and vertical segmented types. 4. Briefly describe the classification of centrifugal pumps. Depending on the application requirements, centrifugal pumps come in different types. Based on the number of impellers, they can be divided into single-stage pumps and multi-stage pumps ； Based on the way fluid enters the impeller, they can be divided into single-suction and double-suction types ； Based on the pump casing division pattern, they can be classified into horizontally split pumps and vertically split pumps along with the pump shaft ； Based on the structure of the pump casing, they can also be divided into volute pumps and turbine pumps. In addition, pumps are classified according to their head into low-pressure pumps (head less than 20 meters of water column), medium-pressure pumps (20–160 meters of water column), and high-pressure pumps (head greater than 160 meters of water column). Eucalyptus transfer pumps are further divided into water pumps, oil pumps, and corrosion-resistant pumps, among others. 5. What is the flow rate of a pump? The amount of fluid discharged by the pump per unit of time is called the pump’s flow rate, and this flow rate is determined by the manufacturer. Flow rate can be divided into mass flow rate and volume flow rate: mass flow rate refers to the weight of the fluid that passes through in a unit of time, with units such as Kg/S or t/h; volume flow rate refers to the volume of the fluid that passes through in a unit of time, with units such as liters per minute or m3/h. 6. What is the head of a pump? The head of a pump refers to the increase in energy per unit weight of liquid after work is done by the pump; the unit is meter, denoted as H. H = h_table + h_vacuum + (V2_out - V2_in) / 2g. Here, h_table represents the head for water discharge, in meters ； h vacuum refers to the water inlet head, unit: m ； V_out and V_in refer to the average flow velocities at the outlet and inlet, respectively; unit: m/s ； g refers to the acceleration due to gravity, 9.8 m/s2. 7. What is the specific gravity of a fluid? The specific gravity of a fluid refers to the weight per unit volume, commonly denoted by the symbol γ. γ=G/V kilograms per cubic meter; G represents the weight of the fluid, in kilograms ； V represents the volume of the fluid, in cubic meters; γ has the unit of g/cm3 ； Kg/cm3 ； T/m3, etc. The specific gravity of a fluid changes with temperature; the higher the temperature, the greater the volume expansion of the substance, and accordingly its specific gravity decreases