1.1 Preliminary understanding of several common types of positive displacement compressors
1. Reciprocating compressor
(1)Reciprocating piston compressor (commonly known as the piston machine or,
Figure 3-2 of the compression element including piston and cylinder, through the piston in the cylinder for reciprocating motion to achieve gas compression.
Piston compressor is the most widely used
Figure 3-2 piston compressor
(2)Diaphragm compressor refers to the compressors that rely on the diaphragm deformation caused volume change in the cylinder.
Diaphragm compressor (see Figure 3-3) of the special structure, making its flow smaller,
but the compressed gas does not stain the gas lubrication, can ensure a high degree of purity of the gas,
suitable for compression of a small amount of gas does not allow
lubricants contamination of the gas, especially for precious and high purity of rare gases as well as extremely dangerous gases compression, transport.
Figure 3-3
The special structure of diaphragm compressor (see Figure 3-3) makes its flow smaller, but the compressed gas does not contact with any lubricant,
which can ensure the high purity of the gas, suitable for compression of small amounts of gases that are not allowed to be contaminated by the lubricant.
This kind of compressors are especially suitable for the compression and transport of precious and highly pure rare gases and extremely dangerous gases.
2.Rotary compressor
(1) Rotary screw compressor is divided into single screw compressor and twin screw compressor.
① single screw compressor, as the name suggests, single screw compressor only a screw (rotor), the screw at the same time
with a few star wheel engagement, screw type surface, star wheel end face, the screw ends of the cover plate together into a number of closed volume for the realization of the gas compression.
Figure 3-4 is commonly used in air compression of a screw, two star wheel structure of the single screw compressor.
Figure 3-4 single screw compressor
② twin-screw compressor (see Figure 3-5) is formed by the male and female rotor meshing vice, through the screw rotor teeth to achieve the purpose of compression of the volume change,
is the most widely used rotary compressor of a kind.
Figure 3-5 Twin screw compressor
(2) sliding vane compressor
(see Figure 3-6), the axial slide in the same cylindrical cylinder eccentric rotor for radial sliding, trapped in the air between the slide with
the rotation of the rotor and constantly be squeezed, so as to achieve compression.
3-6 Compression
(3) scroll compressor (see Figure 3-7), is a compressor consisting of a fixed involute scroll disc and an involute motion scroll disc that is eccentric gyratory flat.
Figure 3-7 Scroll compressor
2.1.2 Advantages and Disadvantages of Several Commonly Used Models
This section will focus on the application of air compression of positive displacement compressors several common models of the characteristics.
(1) Reciprocating piston air compressor
This is the earliest development of various types of compressors, the widest range of application of a class of compressors. Almost in a variety of uses in the compressor,
you can always see the figure of reciprocating piston compressor. Almost all the new structure of the compressor came out, mostly to replace the reciprocating piston compressor
in some areas of application for the purpose. So far, reciprocating piston compressors are still irreplaceable in some areas, such as ultra-high pressure.
the main advantages of reciprocating piston compressors are as follows.
① strong adaptability, regardless of the size of the flow rate, can achieve the required pressure. In general, a single-stage compression end pressure up to 0.3 ~ 1.0MPa,
multi-stage compression end pressure up to 300MPa or more!
② high adiabatic efficiency. Medium and large units adiabatic efficiency up to 0.7 ~ 0.85.
③ When adjusting the gas volume, the exhaust pressure is almost unchanged, the exhaust range is wider, and it can adapt to a wider pressure range.
pressure range.
(4) In the general pressure range, the material requirements are low, processing is easier, and the cost is cheaper.
(5) The characteristics of the gas have little influence on the performance of the compressor, and the same compressor can be used for different gases.
(6) The driving machine is relatively simple, most of them adopt electric motor, generally without speed regulation, and can be maintained.
(7) more mature technology, in the production and use of the accumulated experience.
The main disadvantages of reciprocating piston compressor are as follows.
(1) the speed is not high, if the exhaust volume is large, the machine volume is large.
② heavy parts, complex structure, more wearing parts, daily maintenance.
③ Poor power balance, machine running with vibration.
③ Poor power balance, vibration during operation.
④ Discontinuous exhaust, uneven airflow, easily caused by pipeline vibration.
⑤ Oil lubricated compressor, airflow with oil.
(2) Twin Screw Air Compressor
Compared with other types of compressors such as reciprocating piston compressors, the twin-screw compressor is relatively new. It has been widely valued by the industry
since its birth in the 1930s and 1940s, and has matured and improved in the 1970s. After years of development, twin-screw compressor in the flow range of 1 ~ 60m'/min pressure range ≤ 2.0MPa
within the widely used, in the industrial field occupancy rate has been close to 80% (almost completely replace the reciprocating piston air compressor).
(1) The main advantages of twin-screw air compressor are as follows.
① High reliability, simple structure, few moving parts, long service life.
② Good power balance, the equipment can achieve smooth and high-speed operation without foundation.
③ Strong adaptability, with the characteristics of forced gas transmission, volumetric flow is almost independent of the influence of exhaust pressure, in a wide range can maintain high efficiency.
④ Multi-phase mixed transmission, can compress wet gas and gas containing liquid droplets.
⑤ Simple operation and maintenance, high degree of automation.
(2) The main disadvantages of twin-screw air compressor are as follows.
① Higher construction cost. Screw compressor rotor tooth surface is a space surface, need to use special cutting tools, in special equipment for processing, special equipment is expensive.
In addition, the screw compressor cylinder machining accuracy is also a high requirement, making the cost increase accordingly.
② Can not be used for high-pressure occasions. By the rotor stiffness and bearing life and other aspects of the limitations of the screw compressor is only suitable for low-pressure range,
exhaust pressure is generally not more than 3.0MPa.
(3) can not be made into a miniature. Screw compressors rely on gap sealing gas, only when the volume flow is greater than 0.2mmin, screw compressors have superior performance.
Single screw air compressor was invented in the 1950s and 1960s. A single screw compressor with CP-type is a type of rotary compressor with a typical structure consisting of the primary
screw rotor, two star-wheels, and housing, where it has efficiency and performance preferable to other types.Single screw air compressors usually require fluid injection to act as a seal, cool
the gas and lubricate the engaging pair.
(3)Single Screw Air Compressor
(1) The main advantages of the single screw air compressor are as follows
① Reasonable structure with ideal force balance. This is shown in all the structure of the compressor. Acting in the screw groove of the gas,
axial load is bound to offset, and then due to the symmetrical configuration of the star wheel, for particularly prominent. Used in the screw on the radial force also cancels each other,
so the screw is not subject to any axial and radial unbalanced force. Because of its good balance of forces, compared with the twin-screw compressor, can achieve higher pressures.
② Low noise and vibration. Because of the good force balance of the single screw air compressor, there is little vibration and no foundation is required.
The star wheel is made of composite material, plus the compression chamber is lubricated by spraying liquid, and there is no speed increasing gear, so the noise is also small.
Therefore, the noise is also small. The capacity of single machine is large, and there is no gap volume.
When the single screw air compressor is working, each screw groove on the screw is used twice in one revolution, so that the space of the screw groove can be fully utilised, therefore,
compared with other rotary compressors, the size of the single screw air compressor can be smaller.
(2) The main disadvantages of the single screw air compressor are as follows.
① More moving parts. Single-screw air compressor has three rotary axis, and screw and star wheel rigidity difference is large, the movement of the thermal expansion coefficient is different,
easy to deformation is not uniform, so it is difficult to ensure the accuracy of mutual cooperation.
② star wheel and screw mesh vice composition of the gap and positional accuracy between the high requirements of today's machining process efficiency is low,
looking forward to the development of high-speed milling and grinding means of processing.
Dream Compressors has been committed to the Chinese air compressor industry for 14 years, and has helped countless customers to improve and upgrade their air-using equipment, as well as expand their new projects.
We look forward to hearing from you.
