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Analysis of the Four System Processes of the Screw Air Compressor
(Summary description)After the gas is filtered by the air filter, it enters the machine head through the intake valve to be compressed and mixed with the lubricating oil. The compressed air mixed with oil is discharged to the oil and gas separation barrel, and then enters the gas pipe network after passing through the oil and gas separator, the pressure maintenance valve and the after-cooler.
Analysis of the Four System Processes of the Screw Air Compressor
(Summary description)After the gas is filtered by the air filter, it enters the machine head through the intake valve to be compressed and mixed with the lubricating oil. The compressed air mixed with oil is discharged to the oil and gas separation barrel, and then enters the gas pipe network after passing through the oil and gas separator, the pressure maintenance valve and the after-cooler.
- Categories:Principle
- Author:
- Origin:
- Time of issue:2017-09-27 09:01
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1. Air flow
After the gas is filtered by the air filter, it enters the machine head through the intake valve to be compressed and mixed with the lubricating oil. The compressed air mixed with oil is discharged to the oil and gas separation barrel, and then enters the gas pipe network after passing through the oil and gas separator, the pressure maintenance valve and the after-cooler.
2. Lubricating oil process
1. Since the pressure in the oil and gas barrel is higher than that in the air inlet cavity of the machine head, the lubricating oil passes through the temperature control valve, oil cooler and oil filter under the drive of the differential pressure, and then enters the machine head in two ways, and one way is directly injected into the compression cavity , the other way passes through the bearing group and then enters the compression chamber, where it is mixed with air in the compression chamber and then discharged into the oil and gas barrel. Most of the oil is deposited in the lower part of the oil and gas barrel after rough separation, and a small amount of oil mist is deposited on the bottom of the filter element after passing through the oil and gas separation filter element, and then introduced into the air inlet cavity of the machine head by the oil return pipe.
2. In addition to the lubricating function of the lubricating oil in the machine head, it also plays the role of cooling and sealing. The heat capacity of lubricating oil is relatively large, and the heat required for each degree of increase is much greater than that of air. The energy input by the driver to the machine head will be converted into heat. In order to control the temperature rise, lubricating oil is sprayed into the machine head, and most of the heat is absorbed by the lubricating oil. The lubricating oil is distributed in the mist state in the machine head, and the contact area with the air is large, so the heat exchange is very fast and perfect. There is a long gap between the rotors and between the rotor and the casing. The leakage through the gap not only reduces the flow, but also leads to high temperature, high energy consumption and high noise. The oil film formed by the lubricating oil between the relatively moving parts has an excellent sealing effect, which can effectively prevent the leakage of high-pressure gas to the low-pressure side.
3. Control system
1. The role of the control system
A. Automatically adjust the displacement of the compressor to keep the pressure of the air storage tank within the set range.
B. In the computer temperature regulation system, the fan motor is automatically stopped and started to keep the exhaust temperature of the machine head within the set range.
C. Alarm or shutdown in case of over temperature, over voltage, over current, etc.
D. Turn on and off the electrical components according to the set sequence when starting and stopping.
2. The control system consists of detection elements, analysis elements, executive elements and human-machine interface. The detection elements include temperature sensors (or temperature switches), pressure transmitters (or pressure switches), differential pressure switches, etc.; the analysis elements are mainly PLC (computer boards); the executive elements include loading solenoid valves, venting solenoid valves, and contactors; The human-machine interface is mainly a liquid crystal display, buttons and signal lights.
4. Transmission system
According to the different transmission methods, screw compressors are divided into direct-connected compressors, belt-driven compressors and gear-driven compressors.
The transmission mode has a significant impact on the energy consumption, economical operation and reliability of the screw compressor. The source of the machine head has an important influence on the transmission mode of the machine.
1. Directly connected compressor
The direct-connected compressor transmits the power of the motor to the machine head through the elastic coupling. The transmission link of the direct-connected compressor consumes almost no energy and is the most efficient transmission method. There is no maintenance work on the coupling except that the elastomer is replaced every 3 years. Using the new flange type elastic coupling, it is very convenient to replace the elastic body without disassembling the machine head, pipeline and valve. The rotational speed of the male rotor of the direct-connected compressor is equal to the rotational speed of the motor, so the rotational speed of the direct-connected screw compressor is relatively low, and the service life and reliability are the highest.
2. Belt drive compressor
The belt drive has the functions of transmitting power and changing the speed. The belt drive relies on friction to transmit power, and it needs to consume a certain amount of energy, accounting for about 2% to 3% of the transmitted power. The belt must have a certain tension to obtain sufficient friction, and the belt tension makes the bearings of the motor and the head bear additional radial load, and the belt drive compressor has higher requirements on the bearings of the motor and the head. The production cost of belt-driven compressors is low, and they are generally only used for small compressors and economical compressors. When the belt tension is insufficient, the belt will slip and the transmission power will be insufficient, which will not only cause high temperature wear of the belt, but also reduce the compressor speed and reduce the displacement. The belt tension needs to be checked frequently, and the belt should be pulled closer or replaced in time. Belts must be replaced in groups.
3. Gear drive compressor
The gear transmission also has the functions of transmitting power and changing the speed. The gear transmission itself also needs to consume a certain amount of energy, but the efficiency is higher than that of the belt transmission. Gear transmission requires additional bearings, and also has higher requirements on the lubrication system of the machine. Because the gears of screw compressors are high-speed and heavy-duty gears, the requirements for machining accuracy and materials are high, and the production cost is high. There are two main advantages of gear transmission: the first product modification is easier, by changing the gear ratio to change the head speed, the same head can be used to produce machines with different displacements. Secondly, there are no consumables and wearing parts in the transmission link of the gear drive compressor.
4. Composite drive compressor
A direct-drive compressor with an internal speed-increasing gear. The external coupling is used to transmit power, and the internal gear is used to change the speed.
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