Calculation method of discharge volume of screw air compressor
The calculation of the exhaust volume of a screw air compressor involves multiple factors. The following are several common calculation methods:
1. Basic formula method
Formula:
Parameter description:
- Exhaust pressure: The pressure at the exhaust port of the screw air compressor, in MPa or bar.
- Exhaust flow: The volume flow of gas through the exhaust port per unit time, in m³/min.
- Atmospheric pressure: The atmospheric pressure of the current environment, in MPa or bar.
2. Power conversion method
formula:
Instructions:
- Use this formula, you can divide the product of the exhaust volume (in m³/min) and the exhaust pressure (in MPa) by 367 to convert it into the power of the air compressor (in kW).
- This method is mainly used to estimate the power of an air compressor by known exhaust pressure and exhaust flow, but in turn can also be used to calculate the exhaust gas by known power and exhaust pressure.
3. Method of the relationship between speed and exhaust volume
Formula:
Instructions:
- Speed rotation speed:
- Roar speed: The rotor speed of the air compressor, unit is rotation/min.
- Single-turn displacement: The volume of gas that can be discharged by each rotor for one cycle, in m³/turn.
- This method requires knowing the specific speed and single-turn displacement of the air compressor, which may be difficult to obtain in some cases.
IV. Calculation of equal exhaust volume (based on speed calculation table)
Instructions:
- calculation of equal exhaust volume: When the exhaust volume remains unchanged, as the exhaust pressure increases or decreases, the motor power increases or decreases accordingly.
- This method is usually calculated based on empirical formulas or speed calculation tables. For example, it is known that the exhaust volume and power of a certain type of air compressor under a certain exhaust pressure, and the exhaust volume and power of a certain type of air compressor can be calculated through a speed calculation table.
- Precautions: When using the speed calculation table for calculation, it is necessary to ensure that the selected speed calculation table is suitable for the calculated air compressor model and operating conditions.
5. Method for correcting actual exhaust volume
Formula:
Instructions:
- Theoretical exhaust volume: The exhaust volume calculated based on the design parameters and ideal operating conditions of the air compressor.
- Corrective coefficient: The coefficient introduced considering the influence of actual factors such as leakage, suction state, cooling effect on the exhaust volume.
- This method is used to correct the theoretical exhaust volume to more accurately reflect the actual exhaust volume of the air compressor.
VI. Other considerations
When calculating the exhaust volume of a screw air compressor, the following factors need to be considered:
- Leakage problem: Leakage between the rotor and between the rotor and the casing will affect the exhaust volume.
- Inhalation status: Factors such as inhalation temperature and inhalation pressure will affect the density of inhaled gas, thereby affecting the exhaust volume.
- Cooling effect: Poor cooling will lead to preheating of inhaled air and reduce the inhalation volume.
Summary:
When calculating the exhaust volume of a screw air compressor, the appropriate calculation method should be selected according to the specific situation. For most users, the basic formula method and power conversion method are relatively common methods. When more accurate calculations are needed, you can consider using equal-discharge calculation method, actual exhaust gas correction method and other methods, and correct them in combination with the specific parameters and working conditions of the air compressor.
