Screw refrigeration compressor screw refrigeration compressor is with spiral groove of one or two rotor (screw) in rotation in the air cylinder to gas compression refrigeration compressor. The work volume of the screw refrigeration compressor is rotary movement of the volume type compressor, according to the number of different screw rotor, the screw compressor with double screw and single screw two.
一： screw compressor working process
一, working principle and working process
1. The screw refrigeration compressor is mainly composed of rotor, chassis (including central suction, exhaust at the ends of the cylinder block and block, etc.), bearings, shaft seal, balance of piston and capacity adjusting device. Figure 3-1 is a typical open a pair of screw compressor rotor, on both ends of the cylinder and the end of the shape of the graph.
1 - suction side 2 - Yin rotor 3 - cylinder 4 - valve 5 - exhaust side 6 - Yang rotor
2. The working principle of the screw compressor's job is to rely on meshing movement with a male rotor with a female rotor, surrounded by and with the aid of the pair of the rotor of the casing wall around the space.
3. The working process of the figure 3-2 for screw compressor working process diagram. Among them, the top view of a and b are a pair of rotor, c, d, e, f for a pair of rotor looked up from the bottom up.
Second, the characteristics in terms of the principle of the compressed gas, screw refrigeration compressor and reciprocating piston compressor, both belong to the volumetric compression machinery, in terms of its movement form, screw type compressor rotor with centrifugal compressor rotor, high-speed rotary motion. So has the characteristics of both screw refrigeration compressor. 1. The advantages
1) higher speed, and quality of light, small volume, cover an area of an area small, and a series of advantages.
(2) dynamic balance performance is good, so the foundation can be very small.
(3) simple and compact structure, less wearing parts, maintenance is simple, reliable use, to achieve automatic operation.
(4) is not sensitive to liquid impact, single stage pressure ratio is high.
(5) capacity is almost not affected by the influence of the exhaust pressure. In the wider range of conditions, can still keep high efficiency
2. The defects
(1) large noise.
(2) requires special equipment and tools for processing of rotor. (3) large auxiliary equipment.
The structure and basic parameters of the second quarter
A, the structure of the main components
The main screw refrigeration compressor parts, including casing, rotor, bearing, balance piston and shaft seal and capacity control device, etc.
1. The chassis
The screw refrigeration compressor casing is usually split. It is composed of the body (cylinder block), suction side, exhaust side and end cover on both ends, as shown in figure 3-3.
1 - suction end cover
2 - suction side
3 - the body
4 - exhaust side
5 - exhaust end cove
2. The rotor
Is a major part of the screw refrigeration compressor rotor. As shown in figure 3-4, often adopts integral structure, make the screw on the shaft
1 - Yin screw 2, Yang screw (3) bearing and hydraulic balance piston screw refrigeration compressor is a high-speed overloading. In order to ensure accurate positioning of the rotor of the Yin and Yang and balance the axial force and radial force, must choose high precision, high speed and overloaded bearings and the corresponding balance mechanism, ensure the rotor reliable operation. Generally said, low load, small machine, using rolling bearing; High load, large and medium-sized machine, we adopt sliding bearing. In order to balance some or all of the axial force, usually with a balance piston to achieve this goal. As shown in figure 3-5 for a hydraulic balance piston structure. 4. Refrigeration system is very important for the seal of the shaft sealing, so in open overhung rotor shaft of the screw refrigeration compressor, usually adopt sealed performance is good contact type mechanical seal, it is mainly shown in figure 3-6 spring loaded and shown in figure 3 to 7 bellows type two kinds.
1, 2 - drive pin
3 - transmission set
The spring seat 4 -
5 - spring
6 - ring auxiliary seal ring
7 - ring
8 - card ring
9 - static ring
10 - static ring auxiliary seal ring
11 - stop pin
5. Capacity regulating valve Capacity regulating valve is used to adjust the screw refrigeration compressor capacity of a structure element, although there are many types of screw refrigeration compressor capacity adjustment method, but the slide valve adjusting method obtained widespread application. As shown in figure 3-8 a.
1 - lock nut
2, sealing gasket
3 - screw
4, drive set
5 - bellows
6 - ring
7 - static ring auxiliary seal ring
8 - static ring
9 - stop pin
A) valve working schematic diagram b) valve structure diagram 1, Yang rotor
2 - Yin rotor
3 - slide valve
4, hydraulic piston
6. Injection structure of screw refrigeration compressor are mostly adopt injection structure. As shown in figure 3-8 b.
7. Coupling
Open the screw refrigeration compressor by coupling and motor. 2, 1. The basic parameters of rotor tooth profile: driving rotor and driven the tooth surface of the rotor are profile, is the space curved surface.
Open the screw refrigeration compressor by coupling and motor.
2, 1. The basic parameters of rotor tooth
Profile: active driven rotor and rotor tooth surfaces are profile, is the space curved surface.
A) symmetric circular arc tooth profile b) asymmetric arc tooth profile
Tooth: type surface on the perpendicular to the axis of the rotor plane (face) projection is called the rotor tooth shape, is a plane curve.
Meshing line: Yin and Yang rotor tooth meshing movement of mesh point on the surface of the platforms, trajectory, called tooth meshing line, as shown in figure
3-9, general by a circular arc tooth profile, cycloid, elliptic, parabolic and radial line, etc.
Lines: the tooth profile curve of rotor is called lines.
(1) the basic requirement of tooth shape
1) good air tightness Leaking ways as shown in figure 3-10. The direction of the contact wire leakage as shown in figure 3 to 11. As shown in figure 3-12, called leakage triangle.
2) the contact line length of short 3) as far as possible the larger area of utilization coefficient. (2) typical tooth In the screw compressor, for the same on both sides of the center line of the tooth shape contour line according to symmetrical line (FIG. 3-9 a), according to different asymmetric lines (FIG. 3-9 b), tooth profile are pitch outside or inside of the pitch circle type according to the single line (FIG. 3-9), otherwise known as bilateral lines. 1) X X tooth shape of tooth profile as shown in figure 3-13, it is composed of Atlas copco company of Sweden in arc cycloid unilateral asymmetric tooth shape on the basis of improvement. 2) the Sigma Sigma tooth shape of tooth profile as shown in figure 3 to 14, it is composed of German Kaeser compressor company in arc cycloid unilateral asymmetric tooth shape on the basis of successful development.
3) CF tooth profile CF tooth shape as shown in figure 3 to 15, which is designed by German GHH company.
Should see, in order to evaluate or comparing different tooth profile of a number of factors are mutually restricted. Such as: in order to reduce leakage triangle, ensure the screw's axial air tightness using point meshing cycloid, will inevitably increase the contact line length; In order to protect the occurrence of cycloidal point, use small circular arc or straight line type line addendum, then increase the leak triangles, and so on. So should be used according to different occasions to choose different tooth profile. Now all kinds of new tooth profile emerge in endlessly, such as Japan's Hitachi a tooth shape, of kobe b tooth shape (FIG. 3-16 a), Sweden, darfur (Stals) tooth shape (FIG. 3-16 b), greatly improve the performance of the screw compressor.
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