Advantages and Features of Closed Impellers in Centrifugal Compressors

1. Key Advantages

✅ High Efficiency (85~92%)

• Fully enclosed flow path design significantly reduces gas leakage, achieving much higher energy conversion efficiency than open/semi-open impellers.

✅ High-Pressure Capability

• Can withstand working conditions >5MPa, making it the preferred choice for high-pressure applications like natural gas pipeline compression and air separation.

✅ Low Turbulence Loss

• Smooth enclosed flow path optimizes airflow, reducing vortex and friction losses.

✅ Long Service Life

• Shrouds protect blades from direct media erosion, ideal for continuous industrial operations (e.g., refinery compressors).

2. Structural Features

🔧 Dual-Shroud Design

• Front shroud + back shroud fully enclose the blades, forming a sealed flow channel.

🔧 Precision Manufacturing

• Typically produced via 5-axis milling or investment casting, ensuring flow path dimensional tolerance ≤±0.05mm.

🔧 Material Selection

• Clean gases: Stainless steel (SS304/316)

• Corrosive environments: Titanium alloy (Ti-6Al-4V) or Nickel-based alloy (Inconel 718)

3. Typical Applications

⚙️ High-Pressure Clean Gases

• Natural gas compression

• Air separation units

• Refrigeration cycles

⚙️ High-Speed Conditions

• Centrifugal refrigeration compressors (>20,000 RPM)

• Aircraft auxiliary power units (APUs)

4. Comparison with Open Impellers

5. Selection Guidelines

• Prefer Closed Impellers When:

  • Media is clean (solid content <0.1%)

  • High efficiency or high-pressure output is required

  • Long-term continuous operation is needed (e.g., petrochemical main compressors)

• Avoid in These Scenarios:

  • Dusty/viscous media (use open or semi-open impellers)

  • Frequent cleaning requirements