Regarding centrifugal compressors!
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What do the terms “stage,” “section,” “cylinder,” and “row” specifically refer to in a centrifugal compressor?
Stage: It refers to a single-stage impeller； Section: Composed of one or several levels ； Cylinder: Compressors are divided into high-pressure cylinders and low-pressure cylinders ； One cylinder can be divided into several sections ；
Do centrifugal compressors also have “rows”? I don’t seem to have heard of it.
A stage refers to an impeller, while a section is composed of multiple stages; one or several stages make up a section. As for the cylinders, they are the high-pressure cylinder and the low-pressure cylinder mentioned earlier. For example, in a compressor, it can be divided into a compression section and a circulation section.
One impeller represents one stage, one suction and discharge section constitutes one segment, and one casing is the cylinder. A section can be of one level or multiple levels, and a compression cylinder can consist of one section or multiple sections.
The number of columns refers to the count of cylinders in a reciprocating compressor; for example, a four-column three-stage compressor means that two first-stage cylinders form one stage, while the second, third, and fourth-stage cylinders each form their own stage. For a centrifugal compressor, each impeller represents one stage ； A stage is a compression unit composed of one or more stages of impellers ； A cylinder refers to a compression unit that consists of one or multiple stages ；
Working principle of screw refrigeration compressors: The screw rotors are installed in a horizontal housing, which provides an inlet and an outlet. A very small gap between the rotors and the housing is dynamically sealed by an oil film that is directly sprayed onto the rotor teeth. The compression process occurs as the motor drives the rotor to rotate, causing the volume to gradually decrease: several compression chambers are formed between the rotating rotor and the housing, and as these chambers move along the axial direction, their volumes gradually shrink. This process can basically be divided into three stages: inhalation. Initially, when the protruding teeth of the male rotor begin to engage with the grooves of the female rotor, the compression chamber opens toward the inhalation side, and gas flows into the tooth grooves through the inhalation port. As the rotor rotates, the volume of these tooth grooves gradually increases, allowing more gas to enter the space where the teeth are engaged, until the tooth grooves at the inhalation end close off this chamber; at that point, the inhalation process is complete. Compression: As the rotor continues to rotate, the volume of the compression chamber gradually decreases. At the same time, the compression chamber moves along the axis toward the exhaust port, which causes the pressure of the refrigerant gas contained within the chamber to increase continuously. Exhaust: This exhaust port, determined by the geometry of the housing, is connected to the compression chamber; here, the compressed refrigerant gas is expelled from the compression chamber as a result of further engagement between the protruding teeth and the grooves. Oil separation and oil cooling: The gas-oil mixture discharged by the compressor enters the oil separator, where the oil is separated. The oil then flows out from the bottom of the oil separator; after being filtered through an oil filter to remove impurities, it is drawn in by an oil pump and sent to the oil cooler. There, it is cooled by cooling water, and after further filtration through an oil fine filter, it is sent to the main oil distribution pipe, from where it is delivered to the various parts of the system that require lubrication for reuse. The high-pressure refrigerant gas that has been separated is sent to the condenser in the system, thus returning to the overall circulation system.
What this person said is more or less correct; one impeller corresponds to one stage； In a compressor, the first stage refers to the section from the inlet of the impeller to the outlet of the diffuser and return vessel; the inlet and outlet volutes, along with several stages, constitute one stage. One stage represents several consecutive compression steps, and segmentation is necessary due to the presence of cooling systems or other process components in between. Several such stages together form a cylinder, and one housing constitutes one cylinder. Since a single cylinder cannot achieve the desired pressure level, it is necessary to add more cylinders
Where does the oil at the outlet of the screw compressor come from?