一. Analysis of the Advantages and Disadvantages of Screw Air Compressors
Screw air compressors provide driving force for pneumatic systems. Their advantages and disadvantages include ease of use, the ability to control air volume by adjusting the screw rotor, a wide range of exhaust pressure variations, support for throttling, a lack of consumable parts, a low failure rate, and ease of maintenance.
Drawbacks include the unavoidable gap between the male and female screw rotors, which can reduce airtightness over time, impacting efficiency. Furthermore, if the interval between uses is too long, the internal screw rotor can easily become stuck during downtime, causing unnecessary trouble when reusing the compressor. Furthermore, after 3-5 years of operation, internal parts deteriorate significantly, typically requiring factory replacement, resulting in a shorter service life.
二. Analysis of Factors Affecting Screw Air Compressor Energy Consumption
1. Input Gas Temperature and Humidity: During operation, the output gas properties of a screw air compressor will change with changes in the compressed gas temperature and humidity. This can affect the performance of gas-consuming equipment, leading to increased energy consumption. In actual use, changes in input gas temperature have a direct impact on air compressor energy consumption, primarily in terms of compression function and cooling system. Given other parameters, the energy consumption of a screw air compressor increases with rising input gas temperature. Since gas temperature and density are inversely proportional, for the same output gas mass, a higher input gas temperature results in a larger gas volume and, consequently, higher energy consumption.
Concurrently, compression power consumption and cooling system energy consumption also increase with rising input gas temperature. Input gas humidity also has a direct proportional relationship with energy consumption: higher humidity results in greater energy consumption. This is because after the input gas enters the air compressor system, the drying equipment uses adsorption to control the gas humidity to ensure that the output compressed air meets specified parameters. Higher humidity requires more adsorbent and may result in a reduction in the output compressed air, significantly increasing the operating energy consumption of the entire screw air compressor system.
2. Inlet and outlet pressures: The inlet pressure of a screw air compressor is closely related to its energy consumption, and its impact on energy consumption cannot be ignored. Under normal circumstances, compressor exhaust volume increases with rising inlet pressure. When inlet pressure decreases, system exhaust volume also decreases, forming a linear relationship. A decrease in inlet pressure results in a decrease in compressor exhaust volume, which, in turn, increases the power consumed to compress a unit mass of gas. Therefore, adding equipment to the inlet to increase inlet pressure may help achieve energy savings. In addition to inlet pressure, outlet pressure also affects system energy consumption. During operation, as outlet pressure increases, a screw air compressor needs to provide greater compression force to ensure the proper operation of the equipment using the air. However, the volume of the clearance space occupied by the air gap is likely to increase with the increased pressure, hindering the efficient operation of the compressor system and increasing energy consumption.
3. Gas Leakage: Screw air compressors are composed of numerous components, which may have some tolerances during manufacturing.
Although these tolerances are within acceptable limits, compressed air can leak through the screw clearance during operation. Once leakage occurs, the operating efficiency of the air compressor will inevitably be affected, the volume flow rate will also drop significantly, and energy consumption will increase.
From the actual use situation, gas leakage can be divided into two categories:
(1) Internal leakage Although internal leakage will not directly reduce the volume flow rate, it will cause the temperature of the gas in the volume chamber to rise, thereby increasing the compression power consumption, such as the high-pressure part of the compressed gas leaking to the low-pressure part of the air compressor system. However, in subsequent use, in-depth research on the internal leakage problem will find that when internal leakage occurs, a thermal effect will be generated, and this thermal effect will have an indirect impact on the volume flow rate.
(2) External leakage is different from internal leakage. The occurrence of external leakage can have a direct impact on the volume flow rate. For example, gas leaks from the compression tooth tip volume to the suction tooth tip volume or the suction orifice. The impact is reflected in two aspects: one is the decrease in volume flow rate, and the other is the continuous reduction in system efficiency.
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