Conversion of air compressor air volume and power
The conversion of air production capacity and power of an air compressor needs to be combinedEfficiency, compression ratio, cooling methodand other parameters, the following are specific conversion methods and examples:
1. Theoretical conversion formula
forpiston air compressor, the relationship between gas production volume (Q, unit: m³/min) and power (P, unit: kW) is:
- parameter description：
- : Mechanical efficiency (piston machine approximately 0.75-0.85)
- 、: Suction/discharge pressure (Pa)
- : Thermal insulation index (1.4 for air)
- : Gas constant (287 J/kg·K)
- : Inhalation temperature (K)
example computing：
- Power P=15kW, efficiency η=0.8, suction pressure P1=101325Pa (atmospheric pressure), discharge pressure P2=700000Pa (7bar), temperature T1=293K (20℃)
- Substitute into the formula to obtain: Q≈2.15 m³/min
2. Simplified formula for screw air compressor
forscrew machine, the approximate relationship between gas production volume (Q) and power (P) is:
- parameter description：
- : Specific power efficiency (screw machine approximately 0.08-0.12 kW/m³/min)
- : Pressure rise (bar, i.e. discharge pressure-suction pressure)
example computing：
- Power P=37kW, efficiency η=0.1 kW/m³/min, pressure rise ΔP=7bar
- Substitution gives Q≈5.28 m³/min
Third, the actual selection reference table
| Air compressor type | Power (kW) | Gas production capacity (m³/min) | Efficiency ( %) |
|---|---|---|---|
| piston machine | 7.5 | 1.2-1.5 | 75-80 |
| screw machine | 37 | 5.0-6.5 | 82-88 |
| scroll machine | 5.5 | 0.8-1.2 | 65-75 |
4. Rapid estimation method
-
empirical formula：
For a 7bar pressure system, air production volume (m³/min) ≈ power (kW) × (0.12-0.15)
example: 22kW screw machine → 22×0.13≈2.86 m³/min -
Manufacturer performance curve：
Check the “Power-Flow Curve” in the air compressor technical manual to directly match the corresponding working condition values.
5. Matters needing attention
- Effect of cooling method: The efficiency of air-cooled machines is 5%-10% lower than that of water-cooled machines.
- altitude correction: For every 1000m increase in altitude, the gas production volume decreases by about 1%-1.5%.
- Load factor impact: At part load, the air production volume decreases proportionally but the power changes non-linearly.
Note: Accurate calculation requires taking into account the corrections such as volumetric efficiency and leakage coefficient in ISO 1217 Annex C.