Centrifugal Compressors

Centrifugal compressors are a type of rotary compressor, also known as a turbine compressor. In centrifugal compressors, the high-speed rotation of the impeller imparts centrifugal force to the gas and expands the gas in the diffuser, increasing its pressure.

Initially, centrifugal compressors were not widely recognized as they were only suitable for low to medium pressure and high flow rate applications. However, with the development of the chemical industry and the establishment of various large-scale chemical plants and refineries, centrifugal compressors have become critical machines for compressing and conveying various gases in chemical production, occupying a significant position. The advancement in gas dynamics research has continuously improved the efficiency of centrifugal compressors. Technological breakthroughs in high-pressure sealing, small flow rate narrow impellers, and multi-oil wedge bearings have addressed a series of issues related to the development of centrifugal compressors for high pressure and wide flow rate ranges. As a result, the application range of centrifugal compressors has greatly expanded, and they can replace reciprocating compressors in many applications, significantly broadening their scope.

Principle: When the compressor impeller rotates, the refrigerant vapor enters the impeller passage through the inlet guide vanes from the suction chamber. The gas rotates with the impeller under the action of the blades. Due to centrifugal force, the gas flows radially along the impeller passage and leaves the impeller.

Construction: Single-stage compressors mainly consist of a suction chamber, impeller (working wheel), diffuser, volute (casing), and seals. Multi-stage compressors may include components such as bends and return passages.

Advantages of Centrifugal Compressors:

Centrifugal compressors have a large gas flow rate and a simple, compact structure. They are lightweight, have small unit sizes, and occupy less floor space. Compared to reciprocating compressors, centrifugal compressors are 5 to 8 times lighter for the same refrigeration capacity.

They have fewer vulnerable parts such as valves and piston rings and no crank-connecting rod mechanism. They operate with balance, high reliability, high operational rates, and minimal friction components, resulting in lower spare parts and maintenance costs.

There is no friction between the impeller and the casing, eliminating the need for lubrication. In chemical processes, centrifugal compressors can achieve oil-free compression of chemical media.

Centrifugal compressors are rotating machines and are suitable for direct drive by industrial steam turbines or gas turbines. In general, in large-scale chemical plants, co-produced steam is commonly used to drive industrial steam turbines, providing possibilities for comprehensive utilization of thermal energy.

Disadvantages of Centrifugal Compressors:

Centrifugal compressors are currently not suitable for applications with very low gas flow rates or excessively high pressure ratios. They are more suitable for refrigeration with large capacities, typically above 250,000 to 300,000 kcal/h.

The stable operating range of centrifugal compressors is relatively narrow. While gas flow rate adjustment is relatively convenient, their economic efficiency is poorer.

Typically, they require speed-increasing gear transmission, which results in higher rotational speeds and higher demands for shaft end sealing. These factors increase manufacturing difficulties and structural complexity.

They are prone to "surge" phenomena at low loads.