The positive displacement air compressor is the most common type of air compressor in use today. The positive displacement function serves as the backbone of several different compression mechanisms, which we will explain in greater detail below.
The positive displacement compressor has been widely adopted across industries due to its versatility, wide variety of available specifications, broad range of price options, and relative reliability and quality of operation. But before we explain the different types of compressors in this category, we’ll first describe how this compressor works.
What Is a Positive Displacement Compressor?
A positive displacement air compressor works by drawing air into a compression chamber through an intake and mechanically reducing the volume of the chamber through motion until a set pressure is reached. The compressed air is then discharged through a valve at the rated pressure, providing a flow of air.
Positive displacement compressors can have multiple intakes and compression cavities or just one. While all operate on the same principle, there are several positive displacement air compressor types including the following:
Rotary screw compressor — The rotary positive displacement compressor is the most common type of compressor in use today. It works by drawing air in, sealing the opening and then compressing the air with two rotors that continuously rotate and pass through the cavity. With each rotation, the air is increasingly pressurized until it reaches the set pressure.
This type of compressor is lubricated with an air-oil mixture which collects contaminants from the air, self-lubricates compressor components and reduces operating temperature. While the oil must be filtered from the air before it is used in the end application, the presence of oil creates greater operational efficiency. Rotary compressors are typically available in up to 600hp.
Reciprocating piston compressor — This type of compressor uses a piston in constant motion to draw in and then compress air. In general, one movement of the piston will draw in the air, while the reverse movement will compress it. Reciprocating piston compressors are available in single- or double-chamber designs, meaning that air is compressed on only one side of the piston or on both. These types of compressors are air- or water-cooled, and can offer up to 1000hp.
Rotary vane compressor — Working on a similar principle to the rotary screw compressor, this type of compressor uses vanes instead of helical blades on a rotor to compress air that enters the cavity. Like the rotary screw compressor, it is oil-cooled.
You may also be familiar with dynamic compressors. The difference between a dynamic and positive displacement compressor is that a dynamic compressor moves air at a high speed, creating kinetic energy that is then sent through a diffuser and converted into static pressure.
At Kaishan Compressor, we offer a wide range of compressor solutions and await the opportunity to help you choose the right equipment for your application and requirements. For more information, contact us today.