In the Newtonian fluid, non-Newtonian fluid and gas-liquid two-phase fluid delivery, screw pump has its unique advantages. The most widely used single, double and triple screw pump structure, working principle is very different. From an economic point of view, these three types of screw pumps have other pump can not be replaced applications. Due to the simple profile and low precision of profile, the single screw pump can adopt the high efficiency process without chip processing, so the low price has many advantages in terms of structure and adaptability. In non-lubricating media, including solid media and corrosion Sexual media delivery unique. At present, the domestic production of single screw pump far more than the production of enterprises double and triple screw pump. Single-screw single-screw single screw pump (ie, 1/2 profile) accounted for the vast majority, and the world has gradually promoted the advanced double-headed single screw pump (ie, 2/3 profile). This paper analyzes their advantages and disadvantages and discusses the process route and cross-sectional profile (the formula derivation process omitted), for the promotion of new lines and applications provide a reference.
1 type of line type 1.1 conventional line (1/2 cross-section profile shown in Figure l, referred to as type A, is the oldest type line, first proposed by the French engineer Myan0 rotor truncated circle. Diameter D = 2 a, eccentricity e, pitch t, ​​single head. The stator truncation is an ellipse with radius a and center distance 4e. Its parameters: pitch T = 2t, double head. Center of gravity e is a radius of 2e radius of the circle rolling r is the so-called Cardanodon circular motion. Planet movement. The number of rotor head and stator head ratio of 12.
1.2 new line (2/3 type surface)
Cross-section shown in Figure l (b) (c), referred to as B-type, C-type, in recent years at home and abroad proposed a new type of line.
B-type rotor truncated radius a, the center of the circle 4 e long circle, the diameter D = 2 a, eccentricity e, pitch t, ​​double-headed. C-type rotor truncation is an oval, its diameter D = 2a, eccentricity e, the maximum radius b = a +2 e, pitch t, ​​double-headed.
The formation of stator truncation as shown in Figure I (d) Shenzhen. As described above, a circular motion of the cardanoy circle with a rolling radius of 1.5 e and a radius of e on the circle indicates the skeleton line (triangular prism hypocycle K in Fig. 2). Rotor movement, the axis of symmetry 49 ask the line segment and the bone line conjugate, during the movement of the rotor profile of the line is the stator profile. Although the motion trajectories are the same, due to the different rotor truncated, the formation of the stator profile vary greatly, B-type three-petal-shaped C-like triangle. Its pitch Ding = 1.5 t, three. The ratio of rotor head to stator head is 23.










2-type line equation
A Type B Rotor Equations The same type of C rotor equation is elliptical.
The new line-granting equation is related to the bone line. In Fig. 2, point A1 on the circle is moved to the point when the circle center rotates through the corner, and the equation of the bony line is formula (I). B-type stator profile is the radius of the bone a isometric line (L-line) and a radius of the arc. Lough line equation (2). The pure circular section is the circular equation where the center of the circle is not at the origin is formula (3). X0 and Y0 for the cusp coordinates. C-type stator and B-type line equation similar, so slightly.
3 various types of advantages and disadvantages (1) A type
Advantages: Rotor and stator profile is simple, long production history, processing experience, efficient and economical process. If the rotor adopts the continuous stamping process to make the hollow screw rod factory (Fig. 3), it will not only be efficient and save materials, but also improve the efficiency and life of the pump. Usually, the stator is made of mold rubber. However, in the case of high pressure, due to the compression of rubber deformation, the media back to the pump efficiency dropped sharply, and some high-pressure pump efficiency only l. 0% or so. Solve this problem, rigid sleeve is an effective way. Due to the simple type A stator profile, the rigid sleeve makes it easier to manufacture (Figure 3)
Disadvantages: Due to the relative movement between the rotor and the stator contact surface is not pure rolling, especially in the straight line two segments of the stator slip rate, easy to wear.
2: 2/3 type
With the same parameters, 2/3 type than A-type flow, and therefore the same volume flow smaller. E.g. . e = 0.2 cm, D 亍 1.75 cm, theoretical flow Q (m / r):
Type A: Q = 1.36 T
Type B Q = 1.612T
Type C Q = 1.6041T
With the same parameters, the B-type theoretical flow is 2Ï€e2 larger than that of the A-type, and the C-type flow is slightly smaller than the B-type.
The rotor is double-headed, so its center-of-gravity offset is half that of Type A. This allows higher speeds and less noise. Each revolution of the chamber by 2x3 instead of 1x2, the pump pulsation decreased more. The increase in chamber also allows the zone of higher slip rate to ask for lower instantaneous velocities than Type A, thereby reducing wear and increasing longevity. In addition, the new surface seal, can improve the volumetric efficiency.
In the new line, since the B-type stator profile is derived from a discontinuous equation curve, there are six hard transition points in the profile (bony loophole and cusp arc at the excessive), obviously affect the operational life . However, C-type stator profile is developed by the continuous equation curve, so no such phenomenon.
Comprehensive analysis, at present, China should promote C-type pump. It is reported that C-type has been commercialized in some countries, such as the German Alvieh AG company launched the AED series pumps.
4 process discussion.
A-type rotor technology is more mature, can be used forming vehicles, mold cars, cyclone milling, continuous stamping and other methods. Continuous stamping is currently one of the best A-type rotor production methods.
Foreign multi-axis cavity machining 2/3 type rotor, the higher the cost. Domestic units have introduced its processing machine tools, such as WEIN-GARTNER's VARID five-axis CNC milling machine, can process a variety of types of screw precision profile and single-screw pump rotor, core and rigid sleeve. However, the characteristics of single screw pump structure is mostly hard rotor, soft motion is a complex and not complex (relative double, three screw pump in terms of) products, so if only as a single machine for processing single screw machine, then Obviously excess function. Moreover, this type of medium-sized equipment, priced at about 10 million yuan, is also worth considering. According to the author's empirical analysis, the prototype or small-batch production can be completed by ordinary machine tools with a mastering device. If the mass production is carried out, an imitation milling head is installed on the existing A-type rotor processing machine and the author has completed the structural training to be competent .
A-type rubber stator core processing can be car, milling, grinding and other methods, the plant has a wealth of experience. A new type of wire core technology and A type of similar methods. The key is to have the correct line coordinate information linear or nonlinear contraction of the compensatory prosthesis. A-type rigid sleeve can be used to process ordinary universal machine, 2/3-type rigid sleeve processing is extremely expensive equipment.
5 CAD Model Line Design Example This article uses a similar three-screw pump model used to improve the trajectory programming. The method is simple and reliable, without the need to establish the envelope equation, the program has been used for double and triple screw pump profile design.
Program for the modular design, the package into the tool design software, not only can calculate the single screw pump rotor, stator end, shaft, cross section, but also calculate the rotor, stator core forming car, milling, rolling, Grinding and other tooling line and the tool shovel grinding wheel process parameters. The program also has various types of rubber core shrinkage compensation function, for the new single screw pump research and production of the old line provides a convenient.
Table l for the calculation of CAD. The calculation parameters for e = 20, D = 1 70. Practical, dot density can be arbitrarily set. Line coordinate values, the rotor is l / 4-type line segment; the stator is 1/6 line segment. Symmetrical use of the full profile. The third point in the table is the B-line hard transition point.

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