Core structure composition of centrifugal compressor

As a widely used gas compression equipment in industrial field, centrifugal compressor occupies an irreplaceable position in many industries such as petrochemical industry, natural gas transportation and air separation with its obvious advantages of large displacement, stable operation and low maintenance cost. Understanding the core structure of centrifugal compressor is of great significance for equipment selection, daily operation and maintenance and troubleshooting. In this paper, Turbo-Tech will start with the core components and analyze the main components of centrifugal compressor one by one.
Core structure composition of centrifugal compressor
I. Rotor assembly
Rotor assembly is the core rotating component in centrifugal compressor, which undertakes the direct task of doing work on gas. It mainly consists of the following parts:
Main shaft: As the skeleton of the entire rotor, the main shaft is usually forged from high-strength alloy steel. It is subjected to precise heat treatment and dynamic balance verification to ensure stability and reliability under high-speed rotation.
Impeller: The impeller is the core part of the rotor, which directly determines the working capacity of the compressor. According to different structural forms, they can be divided into three types: closed impellers, semi-open impellers and open impellers. When the impeller rotates at high speed, centrifugal force is used to throw the gas from the core to the edge, thereby completing the process of accelerating and pressurizing the gas. The design, number and material of the blades have a direct impact on the efficiency of the compressor.
Shaft sleeves and couplings: The shaft sleeves are used to protect the main shaft from wear and also serve to position the impeller; the coupling is responsible for transmitting power from a driving machine (such as a motor or steam turbine) to the compressor rotor.
Ⅱ. Stator components
The stator part is a fixed shell structure. Its core function is to guide the direction of air flow, convert the kinetic energy of the gas into pressure energy, and provide a reliable working space for the rotor.
Housing (cylinder): The housing is the outer pressure container of the compressor and is usually made of cast iron or cast steel.
Diffuser: The role of the diffuser is to effectively convert the kinetic energy of the high-speed gas at the outlet of the impeller into static pressure energy. It is a key structure to improve the efficiency of the compressor.
Ⅱ. Sealing system
Due to the presence of high-pressure gas inside the compressor, the design of the sealing system is directly related to the efficiency and reliability of the equipment.
Interstage seal: It is installed between the wheel cover and the casing of each stage of impellers to prevent high-pressure gas from flowing back to the low-pressure stage. It is usually in the form of labyrinth seals. Labyrinth seals rely on multi-stage throttling effects to reduce leakage, have a simple structure and require no lubrication.
Shaft end seal: Set at the position where the shaft passes through the casing to prevent process gas from leaking out or external air from being *ed in. Depending on the pressure level of the working conditions, different types such as labyrinth seals, mechanical seals, floating ring seals or dry gas seals can be selected. Among them, dry gas seals are becoming more and more widely used in modern high-pressure centrifugal compressors due to their advantages such as no oil pollution and minimal leakage.
Ⅳ. Bearing system
Bearings provide radial and axial support for high-speed rotating rotors, ensuring positional accuracy and stability of the rotors during operation.
Radial bearing: Withstands the radial load of the rotor. Common forms include sliding bearings (oil film bearings) and tilting pad bearings. Tilting pad bearings have excellent anti-vibration properties because the angle of each pad can be automatically adjusted, making them especially suitable for high-speed and light-load conditions.
Thrust bearing: Withstands the axial thrust generated by the rotor during operation to prevent axial movement of the rotor. Bidirectional thrust bearings can handle axial loads in both directions.
Ⅴ. Lubrication and oil system
Bearings, gears, seals and other components of centrifugal compressors require a continuous supply of clean lubricating oil to reduce friction losses and remove operating heat.
A complete oil system usually includes: main oil pump, auxiliary oil pump, oil cooler, oil filter, high-level oil tank and various valve pipelines. The main oil pump is generally driven by the compressor spindle, and the auxiliary oil pump is automatically put into work during the start-up and shutdown phase or when the main oil pump fails to ensure uninterrupted lubrication. The role of the high-level oil tank is to use gravity to provide short-term lubrication protection for the bearings in emergency situations such as sudden power outages to prevent burning accidents.
Ⅵ. Regulation and control system
Modern centrifugal compressors are generally equipped with complete automatic control systems to achieve reliable and energy-efficient operation.
Anti-surge control: Surge is a dangerous unstable working condition for centrifugal compressors, which may cause severe vibration or damage to equipment. The anti-surge control system monitors inlet and outlet pressure and flow parameters in real time, and automatically opens the return valve or vent valve when the surge boundary is approached, keeping the operating point away from the surge area.
Inlet guide vane adjustment: Install adjustable guide vanes at the inlet of the compressor to adjust the performance curve of the compressor by changing the pre-rotation angle of the gas to achieve flexible adjustment of load.
Interlocking protection system: It continuously monitors key parameters such as bearing temperature, vibration amplitude, lubricating oil pressure, and shaft displacement. Once the limit exceeds the limit, it will automatically alarm or emergency shutdown to ensure the reliability of equipment and personnel.
VII. Auxiliary equipment
In addition to the core components mentioned above, centrifugal compressor systems typically include:
– Intercooler: Cooling the gas between stages of multi-stage compression, reducing the compression power consumption of the next stage and improving the efficiency of the entire machine.
– Intake filter: removes dust and impurities in the intake air and protects the impeller and flow channel from erosion.
– Muffler: installed on the intake and exhaust pipes to reduce the impact of aerodynamic noise on the environment.
The above is a detailed explanation of the core structure and composition of centrifugal compressors. Centrifugal compressors are a highly integrated precision rotating mechanical system. Each component undertakes irreplaceable functions. The coordination and cooperation between various components determines the performance of the whole machine. A deep understanding of its structural composition not only helps engineers and technicians to better manage and maintain equipment, but also lays a solid theoretical foundation for the optimization and upgrading of compressors.