Centrifugation is actually a manifestation of the inertia of objects, such as water droplets on an umbrella. When the umbrella rotates slowly, the water droplets will follow the umbrella. This is because the friction between the umbrella and the water droplets acts as a centripetal force for the water droplets. But if the umbrella turns faster, this friction is not enough to make the water droplets move in a circular motion, then the water droplets will move away from the umbrella to the outer edge, just like a rope pulling a rock in a circular motion, if the speed is too fast, the rope will move disconnect, the rocks will fly out. This is called centrifugation.
The main working principle of centrifugal pump
(1) The impeller is driven to rotate by the pump shaft and does work on the fluid located between the blades. The fluid is thrown from the center of the impeller to the periphery under the action of centrifugal force. When the fluid reaches the outer circumference of the impeller, the flow rate is very high.
(2) The pump casing collects the liquid ejected from between the blades. These liquids flow in the casing along the direction of the volute-shaped channel gradually expanding, so that the kinetic energy of the fluid is converted into static pressure energy and energy loss is reduced. Therefore, the role of the pump casing is not only to collect liquid, it is also an energy conversion device.
(3) The principle of liquid suction: relying on the high-speed rotation of the impeller, the liquid in the center of the impeller is forced to be thrown away at a high speed, thereby forming a low pressure in the center of the impeller, and the liquid in the low tank is continuously sucked up. Gas binding phenomenon: If the casing of the centrifugal pump is filled with gas before starting, when the gas in the center of the impeller is thrown after starting, a sufficient vacuum cannot be formed there, so that the liquid in the tank cannot be sucked up. This phenomenon is called gas binding.In order to prevent the occurrence of air binding, the centrifugal pump should be filled with external liquid before the start of the pump housing. This step is called priming the pump. In order to prevent the liquid poured into the pump casing from flowing into the low tank due to gravity, a check valve (bottom valve) is installed at the inlet of the pump suction pipeline; if the pump position is lower than the liquid level in the tank, no filling is required when starting Pump.
(4) A guide wheel is installed on the outer circumference of the impeller to make the liquid energy conversion efficiency in the pump high. The guide wheel is a fixed bladed ring located on the outer periphery of the impeller. The bending direction of the blades is opposite to the bending direction of the impeller blades, and the bending angle is just in line with the direction of the liquid flowing out of the impeller, guiding the liquid to change direction smoothly in the pump casing channel, minimizing energy loss, and converting dynamic pressure energy into High static pressure energy efficiency.
(5) The balance hole on the rear cover eliminates the axial thrust. The pressure of the liquid leaving the periphery of the impeller is already high, and some of it will seep to the back of the rear cover of the impeller, and the liquid inlet on the front side of the impeller is low pressure, thus generating an axial thrust that pushes the impeller to the inlet side of the pump. This is easy to cause abrasion of the contact between the impeller and the pump casing, and vibration may occur in severe cases. The balance hole allows a part of the high-pressure liquid to leak to the low-pressure area, reducing the pressure difference between the front and rear of the impeller. But this will also reduce the efficiency of the pump.
(6) The shaft sealing device ensures the normal and efficient operation of the centrifugal pump. The centrifugal pump is working when the pump shaft rotates but the shell does not move. If the annular gap in between is not sealed or the seal is not good, the outside air will penetrate into the low pressure area in the center of the impeller, which will reduce the flow rate and efficiency of the pump. In severe cases, the flow is zero-air binding. Generally, mechanical seals or packing seals can be used to achieve the seal between the shaft and the shell.
Introduction to the working principle of centrifugal pump
The main flow components of centrifugal pumps 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 important part of the pump. The important working element is the heart of the flow part. The impeller consists of a cover plate and a middle blade.
Before the centrifugal pump works, fill the pump with liquid, and then start the centrifugal pump. The impeller rotates quickly. The blades of the impeller drive the liquid to rotate. When the liquid rotates, it flows to the outer edge of the impeller by inertia. At the same time, the impeller sucks in the liquid from the suction chamber. In this process, the liquid in the impeller flows around the blades. In the circumfluence movement, the liquid exerts a lift on the blades. In turn, the blades act on the liquid with a force equal to the lift and opposite in direction. This force does work on the liquid. Make the liquid get energy and flow out of the impeller, at this time the kinetic energy and pressure energy of the liquid both increase.
The centrifugal pump relies on the action of the rotating impeller on the liquid to transfer the mechanical energy of the prime mover to the liquid. Due to the action of the centrifugal pump, when the liquid flows from the impeller inlet to the outlet, its speed and pressure energy are increased. The liquid discharged by the impeller passes through the extruder chamber, and most of the speed can be converted into pressure energy, and then transported along the discharge pipeline. At this time, vacuum or low pressure is formed at the inlet of the impeller due to the discharge of liquid. The liquid in the suction pool is pressed into the inlet of the impeller under the action of the liquid surface pressure (atmospheric pressure), so the rotating impeller is continuous Inhale and discharge liquids.
