⚙️ Principle of Operation of Centrifugal Compressors
Centrifugal compressors are widely used in industries for gas compression because of their efficiency, reliability, and ability to handle large volumes of air or gas. Their operation is based on the principle of converting kinetic energy into pressure energy.
🌡️ How Centrifugal Compressors Work
- A centrifugal compressor accelerates the velocity of gases using a rotating impeller.
- The gas gains kinetic energy as it moves outward from the impeller eye to the vane tips.
- This kinetic energy is then converted into static pressure as the gas slows down in the volute and enters the discharge pipe.
- The process involves:
- Stationary casing that houses the impeller.
- Rotating impeller that imparts high velocity to the gas.
- Fixed diverging passages (diffusers) where velocity decreases and pressure rises.
🔧 Basic Components of Centrifugal Compressors
- Impellers: Rotating discs with vanes that accelerate the gas.
- Vanes: Guide the gas flow through the impeller.
- Volutes: Spiral-shaped casings that collect and direct compressed gas to the discharge line.
- Suction Eye: Entry point where gas enters the impeller.
- Discharge Line: Outlet where compressed gas exits the compressor.
- Diffuser Plates: Convert velocity into pressure.
- Seals: Prevent leakage of gas and oil.
- Shaft: Connects the impeller to the driver (motor or turbine).
- Casing: Provides structural support and houses all components.
Key Terms
- Suction Vane Tips: The part of the impeller vane that first contacts the gas.
- Discharge Vane Tips: The part of the impeller vane that last contacts the gas before discharge.
🔄 Types of Centrifugal Compressors
1. Single-Stage Compressors
- Compress the gas once.
- Suitable for high gas flow rates but low discharge pressures.
- Commonly used in applications requiring moderate compression.
2. Multi-Stage Compressors
- Gas discharged from one stage is passed to the suction of the next stage.
- Suitable for high gas flow rates and high discharge pressures.
- Typically operate at speeds greater than 3,000 rpm.
- Used in industries where large-scale compression is required.
📈 Pressure Rise in Centrifugal Compressors
- Gas enters through the impeller eye and is accelerated by the impeller vanes.
- Static pressure increases from the eye to the vane tips.
- The remaining pressure rise occurs in the diffusers.
- Normally, about 50% of the pressure rise occurs in the impeller and the other 50% in the diffuser.
- Some stagnation pressure loss is inevitable due to friction and turbulence.
🌍 Why Centrifugal Compressors Are Popular
- Oil-Free Operation:
Most centrifugal compressors are close to being oil-free. While oil is used in the system, advanced sealing mechanisms minimize contamination, making them suitable for sensitive applications.
- Large Capacity: Capable of handling very large volumes (>100,000 CFM) with a single compressor.
- High Pressure Capability: Can achieve pressures in the range of 100 to 350 kg/cm².
- Economic Advantage: More cost-effective when handling high flow rates compared to other compressor types.
- Reliability: Robust design ensures long service life and reduced maintenance needs.
✅ Conclusion
Centrifugal compressors operate on the principle of converting velocity into pressure, making them highly efficient for large-scale industrial applications. With their ability to deliver high capacities, achieve significant pressures, and maintain near oil-free operation, they remain one of the most popular choices in industries ranging from power generation to petrochemicals.
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