CN206967925U - Embedded short spiral shell rib asymmetric multi-screw extruder in the same direction - Google Patents

Abstract

The utility model discloses an embedded low helix co-directional asymmetric multi-screw extruder. The screw mechanism in the extruder includes a first screw and a second screw that engage with each other. The first screw is a single-head thread structure, and the second The screw has a four-start thread structure; the channel of the groove formed between two adjacent main flights in the first screw has an embedded short flight as a secondary flight, and the height of the secondary flight is less than or equal to the main flight the height of. The processing method is to use the axial positive displacement conveying force of the screw mechanism and the friction force between the first screw and the second screw to realize the material transportation, and use the embedded short screw edge to introduce the "8" shape homoclinic orbital flow disturbance to Trigger the whole process of chaotic mixing in the flow channel of the screw channel, the flow channel composed of the first screw and the second screw forms a topological chaotic effect, the periodic compression and expansion of the flow channel of the screw mechanism and the differential rotation of the two screws function, so that the material is fully mixed, melted and kneaded and plasticized.

Description

Embedded short flight co-rotating asymmetric multi-screw extruder

technical field

The utility model relates to the technical field of multi-screw extruders, in particular to an embedded low helix co-directional asymmetric multi-screw extruder.

Background technique

The co-rotating twin-screw extruder with self-cleaning function is a widely used mixing processing equipment at present. This type of equipment mainly includes a barrel and two twin-screws installed in parallel in the inner cavity of the barrel. In order to generate high shear, the multi-thread structure is often used, which leads to different topological routes of material flow. When the processed material enters the inner cavity of the barrel from the feed port, the material will enter different topological flow channels, such as double The head thread will divide the flow channel in the barrel into three disconnected flow channels. The materials will not mix with each other during the forward conveying process. The unevenness of the feed composition may lead to uneven composition of the materials entering different flow channels. , this unevenness will not be improved by mixing with each other during the forward process of materials, which often leads to unstable product quality. Only in the area where the kneading block is installed can it be mixed with each other, but the kneading block will cause many problems such as high shear, material accumulation, dead space and reduced self-cleaning. On the other hand, due to the geometric meshing relationship, the use of multi-start threads will also lead to shallower grooves and lower production. The traditional co-rotating twin-screw extruder only provides disturbance in the meshing area to improve the mixing quality, and lacks a chaotic mixing trigger mechanism away from the meshing area. Moreover, the volume of the material in the left and right screw grooves is the same, and the mechanism of the tensile force field cannot be introduced. , the main part of the screw channel volume lacks an effective structure for promoting mixing, which will lead to the inability to further improve the distribution mixing effect, and the lack of tensile force field effect will lead to unsatisfactory dispersion mixing. In addition, most of the processing process of the twin-screw extruder is in a non-full state, and the almost unchanged flow path leads to a great reduction in the plasticization and mixing of materials. In order to improve the mixing effect and increase the output, high speed is often used to achieve high shear in engineering practice. Cutting, the large length-to-diameter ratio screw prolongs the processing process, but this method brings many problems such as high energy consumption, low efficiency and material degradation. In recent years, differential twin-screw extrusion technology has emerged. Although chaotic mixing and tensile force field effects have been successfully introduced, it still lacks the topological chaos effect of runner segmentation, melt blending and exhaust during twin-screw extrusion. There is still a lot of room for improvement in functionality.

Utility model content

The purpose of the utility model is to overcome the deficiencies of the prior art, and provide an embedded low screw flight co-directional asymmetric multi-screw extruder. The extruder with this structure can realize the mixing of chaos, topological chaos and tensile force field. The combination of functions can improve the processing efficiency.

The technical scheme of the utility model is: an embedded low-screw co-directional asymmetric multi-screw extruder, including a barrel and a screw mechanism, the screw mechanism is installed in the inner cavity of the barrel, and the screw mechanism includes a first intermeshed A screw and a second screw, the first screw has a single-start thread structure, and the second screw has a four-start thread structure; in the first screw, there is a screw channel formed between two adjacent main screw flights as a secondary flight The embedded short flight, the height of the secondary flight is less than or equal to the height of the main flight. Among them, a single-threaded screw and a four-threaded screw are used to cooperate, and an asymmetric differential structure is formed between the two, which means that there are four enhanced mixing mechanisms in the screw mechanism (i.e. (1) the introduction of "8"-shaped homoclinic orbital flow Disturbance triggers the whole process of chaotic mixing in the screw channel. (2) The flow channel in the screw mechanism forms a topological chaotic effect of cutting in two. (3) Periodic compression, expansion and recompression are realized between the two screws and the second screw. , The effect of re-expansion, (4) the strengthening effect of the differential rotation of the two screws) provides a structural basis.

The outer contours of the first screw and the second screw are tangent to the inner wall of the barrel, and a flow channel is formed between the screw mechanism and the inner cavity of the barrel;

The first screw and the second screw rotate in the same direction and keep meshing at all times, and the rotation speed ratio of the first screw and the second screw is 2.

The radial cross-section of the first screw and the radial cross-section of the second screw are all composed of a plurality of circular arcs and non-circular arcs with different radii of curvature connected alternately, forming the total number of circular arcs and non-circular arcs of the second screw. Twice the total number of arcs and non-circular arcs that make up the first screw.

Combining factors such as the differential speed and meshing principle of the two screws, as a preferred solution, the radial section of the first screw is composed of four sections of circular arcs and four sections of non-circular arcs alternately connected, and the radial section of the second screw The cross-section is composed of eight circular arcs and eight non-circular curved arcs connected alternately.

In the screw mechanism, the screw flight structure on each screw can adopt the following structural methods:

(1) The main flight, the secondary flight of the first screw and the flight of the second screw are all flight structures with smooth edges. This construction provides a fully self-cleaning mix with positive displacement delivery capability for extra capacity.

(2) The main flight of the first screw and the flight of the second screw are intermittent flight structures with notches on the edges; the secondary flight of the first screw is a flight structure with smooth edges. In addition to providing self-cleaning mixing with positive displacement conveying capacity and super large output, this structure also introduces a more complex cutting and splitting principle to provide more powerful distribution and mixing capabilities, but the self-cleaning ability will be somewhat lower than that of the first method. decline.

(3) The first screw is composed of a plurality of first kneading blocks with the same structure interleaved, and the second screw is composed of a plurality of second kneading blocks with the same structure interlaced. In addition to providing fully self-cleaning mixing with positive displacement delivery capacity and super large output, this structure also introduces stronger tensile force field effect to provide more powerful dispersion mixing ability.

As a further preferred solution, the screw mechanism further includes a third screw, the first screw, the second screw and the third screw form an inline three-screw arrangement, and the structure of the third screw is the same as that of the first screw.

The processing method of the above-mentioned embedded short flight co-directional asymmetric multi-screw extruder is as follows: after the material enters the inner cavity of the barrel, the axial positive displacement conveying force of the screw mechanism and the distance between the first screw and the second screw Material transportation is realized under the joint action of friction. At the same time, the embedded short flight on the first screw is used to introduce the "8"-shaped homoclinic orbital flow disturbance to trigger the whole process of chaotic mixing in the channel of the screw channel. Using the first screw and the second The flow channel composed of the screw forms a topological chaotic effect of dividing into two, coupled with the periodic compression and expansion of the flow channel formed by the screw mechanism and the differential rotation of the two screws in the screw mechanism, the materials are fully mixed and Melting and kneading plasticizing.

The barrel is provided with a conveying section, a melting section, an exhaust section and a mixing and extruding section, and the conveying section, melting section, exhausting section and mixing and extruding section are arranged in sequence along the conveying direction of the material; A feed port connected to the inner cavity of the barrel, an exhaust port connected to the inner cavity of the barrel is provided on the exhaust section, and a discharge port is provided at the end of the mixing extrusion section;

The processing process of materials in the barrel is as follows:

(1) After the material enters the flow channel of the conveying section from the feed port, the first screw and the second screw rotate at the same speed along their respective screw axes in the same direction; The friction force between the first screw and the second screw realizes the feeding and conveying. At the same time, it is realized by the axial mixing effect of the embedded short flight on the first screw and the cutting and separating channel formed by the meshing of the two screws. The material components are mixed between the two screws, and the material is forced to move to the flow channel of the melting section;

(2) When the material moves to the flow channel of the melting section, due to the turning action of the embedded short flight on the first screw to the material and the interface renewal effect caused by the two-separated flow channel formed by the meshing of the two screws. The heat transfer process is strengthened, and the expansion and compression of the runner section of the second screw compress and extrude the material to achieve pre-melting of the material, and the high-speed rotation of the first screw and the second screw generates frictional heat, and at the same time in the barrel The combined effect of external heating makes the material further melt, and accelerates the separation of the melted material and the solid material; at the same time, the embedded short flight on the first screw will cause the flow disturbance of the "8"-shaped homoclinic orbit, and the two The topological channel cutting dichotomy of the screw together triggers chaotic mixing throughout the screw channel, which will further accelerate the melting process of solid materials, making the materials a melt;

(3) After the material that becomes the melt enters the flow channel of the exhaust section from the flow channel of the melting section, the first screw is a single-head screw flow channel and communicates with four separate flow channels in the second screw respectively, expanding the The exhaust surface area of the material, and the turning action of the embedded short flight in the first screw and the compression and cutting separation of the second screw flow channel accelerate the discharge of the gas from the exhaust port, and the molten material is affected by the first screw and The action of the second screw further moves towards the flow channel direction of the mixing extrusion section;

(4) After the melted material enters the flow channel of the mixing extrusion section, the molten material is subjected to the cutting one-point-two topological chaos effect caused by the two screws forming the flow channel, and the embedded short helicoid on the first screw It will lead to the "8"-shaped homoclinic orbital flow disturbance, and trigger chaotic mixing in the whole screw groove, coupled with the periodic compression and expansion of the flow channel formed by the two screws and the differential rotation of the two screws, so that The melt material is mixed and plasticized, and the melt material is stably extruded from the discharge port; at the same time, the mutual wiping action between the first screw and the second screw realizes the self-cleaning effect.

Compared with the prior art, the utility model has the following beneficial effects:

1. The first screw of the utility model is a single-threaded screw with an embedded short flight, the second screw is a four-thread structure, and the two screws rotate at a differential speed, which can effectively solve the problem caused by the fluctuation of the raw material composition. The problem of unstable product quality, taking into account the strong conveying efficiency of the single-thread deep groove, improves the solid conveying efficiency, can increase the extrusion output to a greater extent, and is suitable for large-volume processing.

2. The utility model adopts four kinds of enhanced mixing mechanisms: (1) The embedded short screw edge introduces the "8"-shaped coclinic orbital flow disturbance to trigger the whole chaotic mixing of the screw groove; (2) The flow path formed by two screws The topological chaos effect of cutting into two is eliminated, and the axial mixing effect is improved; (3) The periodical compression expansion, recompression, and reexpansion can be realized between the two screws and the second screw, and the mechanism of tensile force field is introduced , effectively realize the compression preheating and dispersion mixing; (4) The differential rotation of the two screws strengthens. Therefore, the utility model fully strengthens the process of mixing and kneading and heat transfer, greatly shortens the thermal and mechanical process for completing plasticization, has low energy consumption, and has remarkable effects of energy saving and consumption reduction.

3. In the screw mechanism of the utility model, it is ensured that the first screw and the second screw are tightly meshed and rotate in the same direction at a differential speed, and the mutual wiping effect between the two screws realizes the self-cleaning effect in the processing process.

4. The utility model introduces an embedded short flight into the first screw, which is especially suitable for the non-full extrusion process, and can realize the tensile force field effect of the first screw and the second screw flow channel, and comprehensively strengthen the mixing and mixing Strength and effect, with extremely excellent dispersion distribution mixing effect, can greatly improve the self-cleaning function of the processing process without using kneading blocks, make the residence time distribution of the processing process narrower, and improve the processing efficiency and effect, especially suitable for High-throughput, nanomaterial processing.

Description of drawings

Fig. 1 is a structural schematic diagram of the screw mechanism and part of the barrel of the embedded short-flight co-rotating asymmetric multi-screw extruder in Example 1.

FIG. 2 is a plan view of FIG. 1 .

Fig. 3 is a sectional view of the screw mechanism along the direction A-A in Fig. 2 .

Fig. 4 is a schematic diagram of the realization of figure-eight homoclinic orbital disturbance, bipartite topological chaos and tensile force field action of the screw mechanism in embodiment 1.

Fig. 5 is a structural schematic diagram of the screw mechanism of the co-rotating asymmetric self-cleaning multi-screw extruder with embedded short flight in Example 2.

Fig. 6 is a structural schematic diagram of the screw mechanism of the co-rotating asymmetric self-cleaning multi-screw extruder with embedded short flight in Example 3.

Fig. 7 is a structural schematic diagram of the screw mechanism of the co-rotating asymmetrical self-cleaning multi-screw extruder with embedded short flight in embodiment 4.

Detailed ways

The utility model will be further described in detail below in conjunction with the examples, but the implementation of the utility model is not limited thereto.

Example 1

In this embodiment, a co-directional asymmetric multi-screw extruder with embedded short flight, its structure is shown in Figure 1-4, including a barrel 1 and a screw mechanism, the barrel 1 is provided with an inner chamber 2, and the screw The mechanism is installed in the cavity, the screw mechanism includes a first screw 3 and a second screw 4, the first screw and the second screw are engaged with each other, and the outermost edges of the first screw and the second screw are tangent to the inner wall of the cavity The inner chamber of the first screw rod, the second screw rod and the machine barrel forms a flow path; as shown in Figure 3, the cross-sectional profile of the first screw rod is made up of 4 sections of circular arcs and 4 sections of non-circular curve arcs, and the cross-sectional profile of the second screw rod It is composed of 8 segments of arcs and 8 segments of non-circular curved arcs; and the first screw is a single thread, and the screw groove of the first screw (that is, the groove formed between any two adjacent main screw edges 13) is provided with Embedded short flights less than the depth of the screw groove, these embedded short flights are used as secondary flights 5, the second screw is a four-start thread, when the first screw and the second screw rotate in the same direction, the speed of the first screw is The rotation speed of the second screw is twice that of the second screw, and the two screws always keep in contact with each other to realize the self-cleaning function. As shown in FIG. 1 , the main flight, the secondary flight of the first screw and the flight of the second screw are all flight structures with smooth edges.

The inner cavity of the barrel is composed of two connected cylindrical grooves, and the cross-sectional shape of the inner cavity is a lying "8".

As shown in Figure 3, the distance between the rotation center O1 of the first screw ₃ and the rotation center _O2 of the second screw 4 is C, and the maximum outer diameters of the first screw and the second screw are both D, and the minimum inner diameters are both d, then the screw inner diameter d is:

d=2C-D.

The cross-sectional profile of the first screw rod is composed of 4 segments of circular arcs and 4 segments of non-circular curve arcs, and the cross-sectional profile of the second screw rod is composed of 8 segments of circular arcs and 8 segments of non-circular curve arcs.

Among them, the four circular arcs that make up the cross section of the first screw are M ₁ M ₂ , M ₃ M ₄ , M ₅ M ₆ and M ₇ M ₈ , and the four non-circular arcs are M ₂ M ₃ , M ₄ M ₅ , M ₆ M ₇ and M ₈ M ₁ . The cross-section of the first screw is symmetrical about the O ₁ O ₂ axis. The arc M ₅ M ₆ is tangent to the inner cavity, the corresponding radius is D/2, the corresponding central angle is α, and it is symmetrical about the O ₁ O ₂ axis. At the same time, the central angles corresponding to the arcs M ₁ M ₂ , M ₃ M ₄ and M ₇ M ₈ are also α. The radius of the arc M ₁ M ₂ is R _m , and d/2≤R _m ≤D/2; and the radius corresponding to the arcs M ₃ M ₄ and M ₇ M ₈ is the inner diameter of the screw d/2.

Specifically, the central angles corresponding to the non-circular arcs M ₂ M ₃ and M ₈ M ₁ are both β _m , and

Taking O ₁ M ₈ as the polar axis, for the non-circular arc M ₈ M ₁ , given:

The polar angle corresponding to the non-circular arc M ₈ M ₁ is:

The polar diameter corresponding to the non-circular arc M ₈ M ₁ is:

In addition, the central angle of M ₄ M ₅ and M ₆ M ₇ is β, and Taking O ₁ M ₄ as the polar axis, given:

The polar angle corresponding to the non-circular arc M ₄ M ₅ is:

The polar diameter corresponding to the non-circular arc M ₈ M ₁ is:

As shown in Figure 3, the cross-sectional profile of the second screw is symmetrical about the O ₁ O ₂ axis and the straight line passing through O ₂ and perpendicular to the O ₁ O ₂ axis, which consists of 8 arcs and 8 non-circular arcs.

Among them, the 8 arcs are N ₁ N ₂ , N ₃ N ₄ , N ₅ N ₆ , N ₇ N ₈ , N ₉ N ₁₀ , N ₁₁ N ₁₂ , N ₁₃ N ₁₄ and N ₁₅ N ₁₆ , these 8 The central angles corresponding to the segment arcs are all α/2, and the arcs N ₃ N ₄ , N ₇ N ₈ , N ₁₁ N ₁₂ and N ₁₅ N ₁₆ are all tangent to the inner wall of the barrel, and their radii are all D/2 , while the radii of arcs N ₅ N ₆ and N ₁₃ N ₁₄ are both d/2, and the radii of arcs N ₁ N ₂ and N ₉ N ₁₀ are both CR _m (wherein, C is the first screw rotation center O ₁ and the distance between the second screw rotation center O ₂ , R _m is the radius of the arc M ₁ M ₂ );

The 8 non-circular arcs are respectively N ₂ N ₃ , N ₄ N ₅ , N ₆ N ₇ , N ₈ N ₉ , N ₁₀ N ₁₁ , N ₁₂ N ₁₃ , N ₁₄ N ₁₅ and N ₁₆ N ₁ , where, The central angles corresponding to N ₄ N ₅ , N ₆ N ₇ , N ₁₂ N ₁₃ and N ₁₄ N ₁₅ are β/2. For the non-circular arc N ₆ N ₇ , take O ₂ N ₆ as the polar axis, given :

The polar angle corresponding to the non-circular arc N ₆ N ₇ is:

The polar diameter corresponding to the non-circular arc N ₆ N ₇ is:

In addition, the central angle corresponding to N ₂ N ₃ , N ₈ N ₉ , N ₁₀ N ₁₁ and N ₁₆ N ₁ is β _m /2, and for non-circular arc N ₂ N ₃ , take O ₂ N ₂ as the polar axis ,given:

The polar angle corresponding to the non-circular arc N ₂ N ₃ is:

The polar radius corresponding to the non-circular arc N ₂ N ₃ is:

At the same time, D/d=1.1-5.5, and the pitches L of the first screw and the second screw are both 0.01D-10000D.

The first screw rod is a single-threaded screw rod, and an embedded short flight as a secondary flight 5 is arranged in the screw groove, while the second screw rod is a four-started screw rod.

As shown in Figure 2, barrel 1 is provided with conveying section 6, melting section 7, exhaust section 8 and mixing extrusion section 9; conveying section 6, melting section 7, exhaust section 8 and mixing extrusion section 9 Arranged sequentially from the moving direction of the processed materials; the top of the conveying section is provided with a feed port 10 connected to the inner cavity, and the upper surface of the exhaust section is provided with an exhaust port 11 connected with the inner cavity; The end is provided with a discharge port 12.

The processing method realized by the above-mentioned co-rotating asymmetric multi-screw extruder comprises the following steps:

(1) After the material enters the flow channel of the conveying section from the feed port, the first screw and the second screw rotate in the same direction and at a differential speed along their respective screw axes; And the friction between the first screw and the second screw can realize the feeding and conveying. At the same time, the two screws can be realized through the axial mixing effect of the secondary flight 5 of the first screw and the cutting and separation topology of the two screws. Mixing of the material components between them, and forcing the material to move towards the flow channel of the melting section;

(2) When the material moves to the flow channel of the melting section, the heat transfer process is enhanced due to the turning action of the secondary flight of the first screw on the material, while the expansion and compression of the flow channel section of the second screw (as shown in Figure 4 (shown in the shaded part at c) to compress and extrude the material to achieve pre-melting of the material, and the high-speed rotation of the first screw and the second screw generates frictional heat, and the external heating of the barrel makes the material further generated Melting; because the flow channel formed by the first screw and the second screw has a bifurcated topological flow channel characteristic (as shown by the solid line and the dashed line at b in Figure 4), and the cross-sectional shape of the flow channel expands, compresses, and then The expansion effect accelerates the separation of the material of the melt and the material of the solid, and at the same time, the secondary flight 5 on the first screw will cause the disturbance of the "8" homoclinic orbit and trigger chaotic mixing in the whole process of the screw groove (a in Fig. 4 As shown in the horizontal "8"-shaped area at the position), the melting process of the solid material will be further accelerated, so that the material becomes a melt;

(3) After the material of the melt enters the flow channel of the exhaust section from the flow channel of the melting section, the first screw is a single-head screw flow channel and communicates with the four separate flow channels of the second screw respectively, which expands the material discharge. The surface area of the gas, and the turning action of the secondary flight in the first screw and the compression and expansion of the second screw flow channel accelerate the discharge of the gas from the exhaust port, and the molten material is further affected by the action of the first screw and the second screw. Move towards the direction of the flow path of the mixing extrusion section;

(4) After the molten material enters the flow path of the mixing extrusion section, see Fig. 4, the molten fluid is subject to the one-point-two topological chaos effect caused by the flow path composed of two screws (as shown in Fig. 4, the solid line at b and As shown by the dotted line), the secondary flight of the first screw will cause the disturbance of the "8"-shaped homoclinic orbit and trigger chaotic mixing in the whole screw groove (as shown in the horizontal "8"-shaped area at a in Figure 4), and the second The effect of the tensile field generated by the periodic compression and expansion of the flow channel composed of the first screw and the second screw (as shown in the shaded part of c in Figure 4), and the effect of four enhanced mixing mechanisms such as the differential speed of the two screws, In this way, the melt material is kneaded and plasticized, and the melt material is stably extruded from the discharge port; at the same time, the mutual wiping action between the first screw and the second screw realizes the self-cleaning effect.

Example 2

In this embodiment, a co-rotating asymmetrical multi-screw extruder with an embedded short flight, compared with Embodiment 1, the difference is that: as shown in Figure 5, the main flight of the first screw and the second The flight of the screw rod is an intermittent flight structure with notches on the edge, and this structure has the effect of further strengthening the mixing; the secondary flight of the first screw rod is a flight structure with smooth edges.

Example 3

This embodiment is a co-rotating asymmetrical multi-screw extruder with embedded short flight. Compared with Embodiment 1, the difference is that: as shown in Figure 6, the first screw is composed of a plurality of first screws with the same structure. One kneading block is formed by interlaced connection, and the second screw rod is composed of a plurality of second kneading blocks with the same structure intertwined, and this structure has the effect of further strengthening melting and kneading.

Example 4

This embodiment is a co-rotating asymmetric multi-screw extruder with embedded short flight, compared with Embodiment 1, the difference is that: as shown in Figure 7, the screw mechanism also includes a third screw 14, the second The first screw, the second screw and the third screw form an in-line three-screw arrangement, and the structure of the third screw is the same as that of the first screw.

As mentioned above, the utility model can be better realized, and the above-described embodiment is only a preferred embodiment of the utility model, and is not used to limit the scope of implementation of the utility model; that is, all equal changes made according to the contents of the utility model and modifications are all covered by the scope of protection required by the claims of the present utility model.

Claims (7)

1. Embedded short flight co-directional asymmetric multi-screw extruder, including a barrel and a screw mechanism, the screw mechanism is installed in the inner cavity of the barrel, it is characterized in that the screw mechanism includes a first screw and a second screw meshing with each other Two screws, the first screw has a single-start thread structure, and the second screw has a four-start thread structure; in the first screw, the screw channel formed between two adjacent main flights has an embedded short flight as a secondary flight screw flight, the height of the secondary flight is less than or equal to the height of the main flight; The radial cross-section of the first screw and the radial cross-section of the second screw are all composed of a plurality of circular arcs and non-circular arcs with different radii of curvature connected alternately, forming the total number of circular arcs and non-circular arcs of the second screw. Twice the total number of circular arcs and curved arcs that make up the first screw. 2. The co-directional asymmetrical multi-screw extruder of embedded short flight according to claim 1, wherein the outer contour lines of the first screw and the second screw are all tangent to the inner wall of the barrel, A flow channel is formed between the screw mechanism and the inner cavity of the barrel; The first screw and the second screw rotate in the same direction and keep meshing at all times, and the rotation speed ratio of the first screw and the second screw is 2. 3. The embedded short flight co-directional asymmetric multi-screw extruder according to claim 1, wherein the radial section of the first screw is alternated by four sections of circular arcs and four sections of non-circular curved arcs The radial section of the second screw rod is composed of eight sections of circular arcs and eight sections of non-circular curved arcs alternately connected. 4. The embedded short flight co-directional asymmetric multi-screw extruder according to claim 1, wherein the flight of the main flight of the first screw, the auxiliary flight and the flight of the second screw are all Spiral structure with smooth edges. 5. The co-rotating asymmetrical multi-screw extruder with embedded short flight according to claim 1, characterized in that the main flight of the first screw and the flight of the second screw both have concave edges on the edges. The discontinuous flight structure of the mouth; the secondary flight of the first screw is a flight structure with smooth edges. 6. The embedded short flight co-directional asymmetric multi-screw extruder according to claim 1, wherein the first screw is composed of a plurality of first kneading blocks with the same structure interlaced, and the second screw It is composed of a plurality of second kneading blocks with the same structure interlaced. 7. The co-rotating asymmetrical multi-screw extruder with low helix embedded in claim 1, wherein the screw mechanism also includes a third screw, and the first screw, the second screw and the third screw form a Inline three-screw arrangement, the structure of the third screw is the same as that of the first screw.