Relationship between air compressor suction volume and exhaust volume

There is a direct relationship between the suction volume and the exhaust volume of the air compressor, but affected by many factors, the actual exhaust volume is usually less than the suction volume. The following is a detailed technical explanation:

1. theoretical relationships

according to the ideal gas equation of state, in adiabatic compression in the process, the relationship between the suction volume (V suction) and the exhaust volume (V row) is:

where & Delta;V temperature rise is the increase in volume caused by the increase in gas temperature during compression. The greater the compression ratio (& pi;= P suction and P row), the more significant the temperature rise, and the greater the V temperature rise.

2. Actual Relationships and Influencing Factors

in actual operation, the following factors lead exhaust volume <suction volume:

1. Volumetric efficiency (& eta;_v)

• definition: & eta;v = V suction V row, theoretical × 100%, reflecting compressor sealing and design efficiency.
• Measured data:
  • piston compressor: & eta;_v & asymp; 75-85% (affected by clearance volume and valve resistance).
  • Screw compressor: & eta;_v & asymp; 80-90% (depending on screw gap tightness).
  • centrifugal compressor: & eta;_v & asymp; 85-95% (applicable to high flow and low pressure scenarios).

2. Leakage loss

• internal leakage: High-pressure gas leaks to the low-pressure area (such as screw gap), reducing compression efficiency.
• External leakage: Gas leaks directly from the compression chamber to the suction channel, resulting in a reduction in V-row.

3. Compression ratio (& pi;)

• formula: & pi;= P suction p row, & pi; The larger the temperature rise, the more significant the temperature rise, which needs to be compensated & Delta; The greater the V temperature rise.
• Case: When & pi; rises from 3 to 5, & Delta;V temperature rise increases by about 30%.

4. Cooling method

• water-cooled compressor: The temperature control is more stable, & eta;_v is 5-10% higher than air cooling.
• air-cooled compressor: Affected by ambient temperature, & eta;_v fluctuates greatly.

Comparison of 3. Measured Data

4. selection recommendations

1. high compression ratio scenario(e. g. high pressure gas filling): screw machine is preferred (temperature rise effect is small, & eta;_v is high).
2. Low pressure and large flow demand(such as industrial gas supply): choose centrifuge (continuous suction, optimal efficiency).
3. Mobile or small applications: Piston selection machine (low cost, but lower & eta;_v).

5. efficiency improvement measures

1. optimized sealing: Using precision machining and high-quality sealing materials to reduce leakage.
2. waste heat recovery: Use the heat generated by the compression process to reduce the influence of temperature rise.
3. frequency conversion control: Dynamically adjust the speed according to the load to improve the partial load efficiency.

Conclusion: The relationship between suction volume and exhaust volume is affected by compressor type, working conditions, design efficiency and so on. In the actual selection, it is necessary to combine the compression ratio, cooling mode, sealing performance and other parameters, select the model with high & eta;_v and less leakage to match the demand and reduce energy consumption.