Oil injection volume of screw air compressor
The oil injection volume of screw air compressors is a key parameter that affects equipment performance and life. Its design, control and monitoring must follow strict principles of heat balance and lubrication efficiency. The following fromDesign logic, influencing factors, control strategy, typical scopeThe analysis is carried out in four dimensions:
1. Design logic of injection quantity
The oil injection quantity is determined by the thermal balance calculation of the compressor. The core formula is:
Q₁ = (T₂ – T₁) × C × m / (ΔH)
- T₂: Exhaust temperature (usually ≤ 110 ℃)
- T₁: Intake air temperature (ambient temperature)
- C: Specific heat capacity of air (1.005 kJ/kg·K)
- m: Mass air flow (kg/s)
- ΔH: Heat absorption per unit mass of lubricating oil (experimental value)
The design needs to simultaneously meet:
- Lubrication requirements: Lubrication amount of moving parts such as bearings and gears
- cooling requirements: The amount of circulating oil required for compressed air and head cooling
- efficiency optimization: Reduce carbon deposition and increased energy consumption caused by excessive injection
II. Key influencing factors
| factors | influence mechanism | Quantitative trends |
|---|---|---|
| compression ratio | Compression ratio ↑, gas density ↑, carrying heat ↑, oil demand ↓ | For every 1 increase in compression ratio, the fuel injection volume is reduced by about 5% to 8% |
| exhaust pressure | Pressure ↑, leakage ↑, sealing needs to be strengthened → fuel injection ↑ | For every 0.1 MPa increase in pressure, the fuel injection volume increases by 1% to 3% |
| speed | Speed ↑, disturbing fuel consumption ↑, but leakage ↑, requiring comprehensive balance | When the speed is>3000 rpm, the fuel injection volume needs to be reduced by 10% to 15% |
| lubricating oil viscosity | Viscosity ↑, fluidity ↓, need to increase the injection amount to ensure lubrication | For every 10 cSt increase in viscosity, the injection volume needs to increase by 5% to 7% |
| ambient temperature | Temperature ↑, intake air density ↓, need to increase the injection volume to compensate for cooling efficiency | For every 10℃ increase in temperature, the fuel injection volume increases by 3% to 5% |
3. Control strategies and monitoring indicators
- oil supply valve adjustment
- typical opening: 90%(full opening may cause excessive injection)
- Adjustment basis: Exhaust temperature (target ≤95℃) and oil content (target ≤3 ppm)
- intelligent control scheme
- the sensor-linked: Adjust the opening of the oil supply valve in real time through the exhaust temperature sensor and the oil partial pressure difference sensor.
- Frequency conversion optimization: At partial load (such as 50% load), the fuel injection volume can be automatically reduced by 30% to 40%.
- monitoring indicators
- oil content: The oil content of compressed air is ≤3 ppm (if the oil core or oil return system is exceeded, the oil separation core or oil return system is required).
- Carbon deposit thickness: Regularly disassemble and inspect the main engine, and the carbon deposit thickness should be ≤0.5 mm (excessive injection will accelerate carbon deposit).
4. Typical injection volume range
| models | Displacement (m³/min) | Fuel injection volume (L/min) | Oil content (ppm) | Exhaust temperature (℃) |
|---|---|---|---|---|
| Micro oil screw machine (low pressure) | 1~3 | 0.5~1.2 | ≤1 | 85~95 |
| Standard oil-injected screw machine (medium pressure) | 5~10 | 2.0~4.5 | ≤3 | 90~100 |
| Two-stage compression screw machine (high pressure) | 15~20 | 6.0~8.0 | ≤5 | 95~105 |
5. Fault warning and solutions
- Insufficient injection: Exhaust temperature>110℃, bearing vibration intensifies →Clean the oil cooler or increase the opening of the oil supply valve。
- Excessive injection: Oil content>5 ppm, carbon deposit thickness>1 mm→Replace the high-precision oil dividing core or adjust the oil supply valve。
- Oil deterioration: Viscosity drops by>15%→Replace lubricating oil immediately (recommended cycle: 4000~6000 hours)。
conclusion: The oil injection volume of screw air compressor needs to be determined through thermal balance calculation and experimental optimization. Combined with intelligent control and regular monitoring, equipment life can be extended and energy consumption can be reduced. It is recommended to conduct a quarterly lubrication system audit to update fuel injection strategies in a timely manner based on process adjustments or environmental changes.