Structure and principle of screw air compressor 1.Basic Structure Generally, what we call a screw compressor refers to a twin screw compressor, and its basic structure is shown in the figure above. A group of interlocking spiral rotors are arranged in parallel in the main machine of the compressor. Usually, the rotor with convex teeth outside the pitch circle (viewed from the cross section) is called the male rotor or the male screw; The toothed rotor (viewed from the cross section) is called a female rotor or a female screw. Generally, the male rotor acts as the active rotor, and the female rotor drives the female rotor to rotate. Rotating ball bearings enable the rotor to achieve axial positioning and withstand axial forces in the compressor. The tapered tube thrust bearings at both ends of the rotor enable the rotor to achieve radial positioning and bear the radial and axial forces in the compressor. Orifices of a certain shape and size are opened at both ends of the compressor main unit, one for the strange use is called the suction port; the other for the discharge schedule is called the exhaust port.
2. Working principle The working cycle of screw compressor can be divided into suction process (including suction and closing process), compression process and exhaust process. As the rotor rotates each pair The meshing teeth complete the same working cycle one after another. For simplicity, we only study one pair of teeth. 1.Inhalation proce (A) Inhalation process (b) Closing process With the movement of the rotor, one end of the rotor teeth is gradually disengaged to form an interdental volume. The expansion of the interdental solution creates a certain vacuum in the interior, and at this time, the interdental volume is only in communication with the suction port. Therefore, the gas flows into it under the pressure difference. During the subsequent rotation of the rotor, the teeth of the male rotor are continuously detached from the grooves of the female rotor. At this time, the volume between the teeth is also continuously expanding and maintaining communication with the suction port. With the rotation of the rotor, the volume between the teeth reaches the maximum value, and at this position, the volume between the teeth is disconnected from the suction port, and the suction process results. At the end of the suction process, the tooth peaks of the yin and yang rotors are sealed with the casing, and the gas in the tooth groove is surrounded by the rotor teeth and the casing in a closed space, that is, the closing process. 2. Compression process With the rotation of the rotor, the volume between the teeth is continuously reduced due to the engagement of the rotor teeth, and the volume occupied by the gas sealed in the interdental solution is also reduced, causing the gas pressure to increase, thereby achieving the compression process of the gas. The compression process can continue until the interdental volume is just before communicating with the exhaust port. 3. The scheduling process After the volume between the teeth is connected to the exhaust port, the exhaust process begins. As the volume between the teeth shrinks, the gas with internal compression pressure is gradually discharged through the exhaust port. This process continues until the end of the tooth. Until the thread is fully engaged, the gas in the interdental volume is completely discharged through the exhaust port, and the volume of the closed interdental volume will become zero. From the above working principle, it can be seen that the screw compressor changes the working volume through a pair of rotors in the casing to make the gas volume shrink and the density increase, thereby increasing the gas pressure.
3. Composition of screw air compressor An oil injection screw air compressor unit is mainly composed of a main machine and an auxiliary machine. The main machine includes a screw air compressor machine and a main motor. The auxiliary machine includes an intake and exhaust system, an oil injection and oil and gas separation system, a cooling system, and a control. System and electrical system lights. In the intake and exhaust system, free air passes through the air intake filter to filter out dust and impurities hi, then enters the air compressor's suction port, and is mixed with the injected lubricating oil during the compression process. The compressed oil-gas mixture is discharged into the oil-gas separation barrel. The lubricating oil in the first and second oil-gas separation barrels depends on the air compressor's discharge pressure and the pressure difference at the fuel injection port to maintain the flow in the circuit. Under the effect of this pressure difference, the lubricating oil enters the oil cooler through the temperature control valve, and then passes through the oil filter to get out the foreign particles. Most of the lubricating oil is sprayed into the compression chamber of the air compressor to lubricate, seal, and cool. And noise reduction; the remaining lubricant is sprayed into the bearing chamber and the speed-increasing gear box. The part of the oil injected into the compression force is discharged into the oil and gas separation barrel together with the compressed air. After centrifugal separation, most of the lubricating oil is separated out, and a small amount of moisturizer passes through the filter core for secondary separation. The separated lubricating oil returns to the low-pressure end of the suction lamp of the air compressor through the oil return pipe. ①The role of lubricating oil: Cooling effect As a coolant, it can effectively control the temperature rise caused by compression heat release; Lubrication As a lubricant, it can form a lubricant film between the rotors; Sealing function As a sealant, it can fill the leakage gap between the rotor and the casing and between the rotor and the rotor. Noise reduction effect The injected oil is a viscous fluid, which has absorption and damping effects on sound energy and sound waves. Generally, the noise can be reduced by 10-20dB(A) after oil injection. ②The role of the minimum pressure valve Ensure the lowest lube oil circulation pressure: As a check valve, to avoid the recompression of the air compressor or no load, the compressed air in the air supply line returns to the unit; Ensure that there is a certain pressure difference between the front and back of the filter element of the oil and gas separator, so as to avoid the phenomenon of squeeze and breakage caused by the excessive pressure difference between the front and back of the filter element just after starting. ③The role of temperature control valve Maintain the lubricating oil temperature above the pressure dew point temperature to prevent moisture in the air from precipitating. ④The role of oil and gas separation barrels As a primary oil and gas separation device, it can effectively separate oil droplets with a diameter greater than 1µm by mechanical collision method; As an oil reservoir for air compressor lubricating oil; As the support body of the oil and gas separator filter element, the filter element can coalesce oil droplets with a diameter of less than 1µm into larger diameter oil droplets and then separate them.
