What are the advantages of double stage /two-stage compression air compressors?

1. Save power consumption

The air compressor (compressor) adopts a multi-stage compression process, which can be achieved by installing an intercooler between stages. After passing through the first stage of compression, the compressed air is first subjected to isobaric cooling to reduce temperature, and then enters the next stage of compression chamber. The temperature decreases and the density increases, making it easier to further compress, which can greatly save power consumption compared to primary compression. Therefore, at the same pressure, multi-stage compression does less work than single-stage compression, and therefore, at the same exhaust flow rate, the less power consumption. Generally speaking, the more the number of stages, the less power consumed, and the closer it is to isothermal compression.

Note: The air compressor of the oil injected screw air compressor is very close to the isothermal compression process. If compression and cooling continue after reaching the saturated state, condensed water will precipitate. If these condensed water and compressed air enter the oil gas separator (oil tank) together, it will emulsify the lubricating oil and affect the lubrication effect. With the continuous increase of condensed water, compressed air may be contaminated, causing serious consequences for the system.

Therefore, in order to prevent the generation of condensed water, the temperature in the compression chamber cannot be too low, and must be greater than the condensation temperature. For example, an air compressor with an exhaust pressure of 11 bar (A) has a condensation temperature of 68 ℃. When the temperature in the compression chamber is lower than 68 ℃, condensed water will precipitate. Therefore, the exhaust temperature of the oil injected screw air compressor cannot be too low, that is, the application of isothermal compression in the oil injected screw compressor is limited due to the problem of condensed water.

2. Improve volume utilization

Due to various reasons such as manufacturing, installation, and operation, the clearance volume in the compression chamber is always inevitable. The clearance volume not only directly reduces the effective volume of the compression chamber, but also requires the residual high-pressure gas to expand to the suction pressure before the compression chamber can begin to inhale fresh gas, which is equivalent to further reducing the effective volume of the compression chamber.

It is not difficult to understand that the greater the pressure ratio, the greater the expansion of residual gas in the clearance volume, and the smaller the effective volume of the compression chamber. In extreme cases, it can even occur that after the gas in the clearance volume has fully expanded in the compression chamber, the pressure is still not lower than the suction pressure, at which point it is impossible to continue suction and exhaust, and the effective volume of the cylinder becomes zero. If multi-stage compression is used, the compression ratio of each stage is very small, and the residual gas in the clearance volume can expand slightly to reach the suction pressure. This naturally increases the effective volume of the compression chamber, thereby improving the utilization rate of the compression chamber volume.

3. Reduce exhaust temperature

The temperature of the exhaust gas from an air compressor (compressor) increases with the increase of the compression ratio. The higher the compression ratio, the higher the exhaust temperature, but excessive exhaust temperatures are often not allowed. This is due to: In oil lubricated air compressors (compressors), the temperature of the lubricating oil decreases viscosity and increases wear. When the temperature rises too high, it is easy to form carbon deposits in the compression chamber and valves, exacerbating wear, and even causing explosions. Due to various reasons, the exhaust temperature is greatly limited, so multi-stage compression must be used to reduce the exhaust temperature.

Note: Staged compression can reduce the exhaust temperature of the screw air compressor, and it can also make the thermal process of the air compressor as close to constant temperature compression as possible to achieve energy saving effects, but it is not certain. Especially for oil injected screw air compressors with an exhaust pressure below 13 bar, due to the injection of low-temperature cooling oil during the compression process, the compression process has approached a constant temperature process, and there is no need to conduct secondary compression. If staged compression is carried out on the basis of this injection cooling, the structure is complex, the manufacturing cost is increased, and the gas flow resistance and additional power consumption are also increased, which is a bit more than worth the loss. In addition, if the temperature is too low and condensed water is formed during the compression process, it will lead to deterioration of the system state, causing serious consequences.

4. Reduce the gas pressure on the piston rod

When the compression ratio of a common piston air compressor is relatively high and single stage compression is used, the cylinder needs to have a larger diameter. If multi-stage compression is used, the gas force acting on the piston can be greatly reduced, which may make the mechanism lightweight and improve mechanical efficiency.

Of course, multi-level compression is not as good as having more stages. As the number of stages increases, the structure of air compressors (compressors) tends to become complex, with increased size, weight, and cost; Due to the increase in gas channels and pressure losses in gas valves and management, sometimes the economy decreases as the number of stages increases. As the number of stages increases, the number of moving parts increases, and the chance of air compressor failure increases. Mechanical efficiency will also decrease due to increased friction

JOY MACHINERY always adheres to the corporate vision of "building a leading brand of oil-free air compressors in the world", and hopes to provide high-quality, clean and safe air for food, beverage and other production enterprises on the road of oil-free air compressor research and development, production and sales. Source protection, and also contribute a little bit to people's health and safety.

JOY MACHINERY oil-free air compressor series is widely used in the food and beverage processing industry due to its clean air source and continuous and stable gas transmission. If you have any needs, please contact us! JOY Machinery (Shanghai) Co., Ltd. has a professional design team with rich experience and welcomes customization. Diversified products can meet most applications and meet your one-stop shopping needs. The air compressor series includes power frequency screw air compressors, variable frequency screw air compressors, permanent magnet variable frequency screw air compressors, two-stage compression screw air compressors, integrated screw air compressors, laser cutting air compressors, medium and high pressure air compressors. Air compressors, oil-free water-lubricated screw air compressors (special oil-free screw air compressors for the medical industry), diesel-moving screw air compressors, electric-moving screw air compressors and other products.

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