Relationship between air compressor outlet volume and outlet pressure

There is a close relationship between the outlet volume and the outlet pressure of an air compressor, which is affected by many factors such as the type, power, and speed of the air compressor. The following provides you with a detailed analysis from four aspects: basic principles, relationship analysis, performance curves and practical applications:

1. The basic principle of air compressor

Air compressors compress the volume of the gas, increase the gas pressure, and transport the gas. It is mainly divided into two categories: volume type and speed type:

• displacement type: Including piston type, screw type, and sliding vane type, gas compression is completed by changing the working volume.
• speed-type: Including centrifugal and axial flow, the gas relies on a high-speed rotating impeller or rotor to gain kinetic energy, which is then converted into pressure energy.

2. Relationship between outgassing volume and outgassing pressure

1. core rule：
   • At constant power,When the outlet pressure increases, the outlet volume will decrease; conversely,When the outlet pressure decreases, the outlet volume increases。
   • For example, a 22KW air compressor has a displacement volume of 3.8 m³/min at a pressure of 7bar; when the pressure rises to 8 bar, the displacement volume drops to 3.6 m³/min.
2. cause analysis：
   • conservation of energy: When the input power of the air compressor is fixed, the energy used to compress the gas is certain. The increase in pressure requires more energy to overcome the repulsion between gas molecules, resulting in a decrease in the volume of gas compressed per unit of time (outgassing).
   • speed regulation: In order to keep the power from being overloaded, the speed needs to be reduced when the pressure increases to further reduce the outgassing volume.

3. Air compressor performance curve

The performance curve is an important basis for the selection and use of air compressors, showing the relationship between flow (outlet volume), pressure, power and efficiency under different working conditions:

• flow-pressure curve: Displays the changes in air outlet volume under different pressures to help you choose the right working point.
• Flow-power curve: Reflect the change of energy consumption with air outlet volume and optimize energy utilization.
• flow-efficiency curve: Demonstrate the change in efficiency with air outlet volume, guiding efficient operation.

example：
The performance curve of a centrifugal air compressor shows that when the exhaust pressure drops from 7bar to 6bar:

• The outgassing volume increased from 3.8 m³/min to 4.2 m³/min (10.5% increase).
• Power consumption dropped from 22KW to 20KW (energy saving 9.1%).

4. Considerations in practical applications

1. Selection matching：
   • Select the type of air compressor according to the required pressure: piston type is suitable for low pressure, screw type is suitable for medium pressure, and centrifugal type is suitable for high pressure.
   • Select the best operating point through the performance curve to ensure efficient operation.
2. operation optimization：
   • pressure regulating: Avoid long-term high-pressure operation and reduce energy consumption and wear.
   • leakage control: Regularly inspect pipes and joints to reduce the impact of leaks on pressure and outgassing volume.
3. environmental adaptation：
   • The air compressor should be placed in an environment with good ventilation and suitable temperature to avoid direct sunlight and rain.
   • Use lubricating oils with high viscosity in high temperature environments, and pay attention to solidification problems of lubricating oils in low temperature environments.

V. Summary

The outlet volume of an air compressor is negatively correlated with the outlet pressure, which is directly affected by power and speed. Through the performance curve, parameter changes under different working conditions can be intuitively analyzed to guide type selection and operation optimization. In practical applications, factors such as the operating environment, pressure requirements, and energy efficiency ratio need to be comprehensively considered to ensure stable and efficient operation of the air compressor.