1、 Single Screw pump Meshing pair of

As the name implies, a single screw pump has only one screw in the pump. Following the habit of naming the single screw pump profession in China, the screw of the single screw pump is called the rotor, and the screw bushing is called the stator. The rotor driven by the external power source is meshed with the stator to form a sealing chamber separating the suction chamber from the discharge chamber, so that the pump can operate effectively. At present, the meshing pair composed of rotor and stator of single screw pump produced in various countries in the world, the vast majority of products are single head spiral rotor and double head inner spiral stator meshing. In recent ten years, some foreign manufacturers have developed the single screw pump with double head spiral rotor and three head internal meshing spiral stator meshing rapidly, and single manufacturers have developed to mass production and sales. There are also a few manufacturing plants in China that carry out research and development, which are still in the development stage. Compared with the single screw pump composed of single head helical rotor and double head inner helical stator, the single screw pump composed of double head helical rotor and three head inner helical stator has the following advantages:

1) In the case of spiral segments with the same speed and the same transverse scale, there is a larger flow, or the lead T has a smaller scale at the same flow.

2) Since the number of seal cavities is 2 per revolution of the rotor × 3=6, while for the pump with single head spiral rotor and double head inner spiral stator, the number of seal chambers is 1 × 2=2, so its flow fluctuation and pressure fluctuation are small.

3) The rotor has a small pitch, so the noise and vibration are also reduced. It is allowed to use a higher speed, or at the same speed and flow, the suction performance is better.

4) Volume power and mechanical power are also higher.

5) The starting distance is small.

6) Longer life.

However, its disadvantages are also very obvious: higher requirements for machining accuracy add difficulty to machining, especially if the machining accuracy is not enough, it will affect the cooperation uniformity of rotor and stator, making the advantages of points 4), 5) and 6) no longer exist; In addition, there are more processing hours and higher production costs, which is why there is less production now. Of course, it is also possible to make a single screw pump with more rotor and stator screw heads, such as a pump composed of a three head spiral rotor and a four head inner spiral stator. However, the requirements for manufacturing accuracy are higher, and the flow does not always increase with the number of screw heads, so there is no practical meaning. Although this meshing pair of rotor and stator with more screw heads has not been used in single screw pumps, it has been widely used in the field of screw drilling tools of petroleum machinery. For the screw drilling tools produced by Beijing Petroleum Machinery Factory in China, the swallowing pair with the largest number of screw heads is the rotor with nine screw heads and the stator with ten inner screws.

2、 Profile of spiral surface of single screw pump

Composition of spiral surface: the cross section of the spiral surface of the rotor is a circle with radius R. The spiral surface of the rotor is the center of the circle of its cross section. O1 rotates at a uniform speed around the rotor centerline O2 with the distance of preference e, and moves forward at a uniform speed with the lead (because it is a single headed spiral, the lead T here is the pitch t), thus forming a left-handed or right-handed spiral surface.

The biggest difference between the single screw pump and other types of pumps during operation is that when the power source is driving, the movement of its rotor in the stator can be regarded as a planetary movement, that is, the rotor with a preference for e not only rolls around its own axis (relative movement), but also rolls around the stator axis (absolute movement) because the displacement of the rotor centerline to the stator centerline is e.

The cross section of the helical surface of the stator is composed of two semicircular arcs ABC and DEF with the same radius as the rotor radius R, and a rectangular ACDF with a distance of 4e and a width of 2R between the centers of these two semicircular arcs. The helicoid is a left-handed or right-handed profile formed by an ABCDEFA surface that rotates uniformly around its axis 0 while moving forward at a constant speed with a lead of T=2t.

Obviously, the rotor is a single head convex spiral, and the stator is a double head concave inner spiral curved surface. The spiral direction of rotor and stator is the same.

Recommended reading: ALLWEILER screw pump , ALL WEILER screw pump manufacturer, ALLWEILER screw pump agent