Multi-nozzle balanced gas injection system for underground coal gasification

Abstract

The invention relates to a multi-nozzle balanced gas injection system for underground coal gasification, which comprises a drill bit and a nozzle pipeline which are connected with each other, a plurality of nozzle pipe rings are arranged on the nozzle pipeline, and the plurality of nozzle pipe rings are uniformly arranged along the length direction of the nozzle pipeline; two holes are formed in the middle of the nozzle pipe ring and used for mounting the nozzles respectively, and the two holes are symmetrically arranged with the central axis of the nozzle pipe ring as the center, so that the two nozzles release gasifying agents towards the two sides of the nozzle pipeline respectively; the inner diameter of the outer end of each inner hole of the nozzle is larger than that of the inner end, and the inner diameters of the outer ends of all the inner holes of the nozzle are the same; from the drill bit, the inner diameters of the inner ends of the inner holes of the nozzles on the same side of the nozzle pipeline are gradually reduced in the length direction of the nozzle pipeline, so that the nozzles on the same side of the nozzle pipeline spray the same amount of gasifying agent within the same time, and it is guaranteed that the nozzle pipeline evenly releases the gasifying agent.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of underground coal gasification, and particularly relates to a multi-nozzle balanced gas injection system for underground coal gasification. BACKGROUND

[0002] The underground coal gasification technology is to drill a well to a target depth in the ground, and there are injection wells and production wells. The gasification agent is input into the ground along the injection well, and then the underground coal is ignited to burn in the atmosphere of the gasification agent. The coal gas produced by the burning is discharged from the production well. At present, the process of inputting the gasification agent into the ground mainly is to guide the gas transmission pipeline into the injection well, and the bottom end of the gas transmission pipeline is open for releasing the gasification agent. However, this release method makes the gasification agent very unevenly distributed in the ground, which directly leads to uneven coal gasification and affects the utilization rate of coal. SUMMARY

[0003] In view of the above problems, the present application provides a multi-nozzle balanced gas injection system for underground coal gasification, which comprises a drill bit and a nozzle pipeline connected with each other, and a plurality of nozzle pipe rings are arranged on the nozzle pipeline and evenly arranged along the length direction of the nozzle pipeline.

[0004] The middle part of the nozzle pipe ring is provided with two eyelets for mounting nozzles, and the two eyelets are symmetrically arranged with the center axis of the nozzle pipe ring as the center, so that the two nozzles release the gasification agent to the two sides of the nozzle pipeline, respectively.

[0005] The outer end inner diameter of the inner eyelet of the nozzle is larger than the inner end inner diameter, and the outer end inner diameters of all the inner eyelets of the nozzles are the same. The inner end inner diameters of the inner eyelets of the nozzles on the same side of the nozzle pipeline gradually decrease from the drill bit along the length direction of the nozzle pipeline, so that each nozzle on the same side of the nozzle pipeline sprays the same amount of gasification agent at the same time, and the nozzle pipeline uniformly releases the gasification agent.

[0006] Optionally, the nozzle pipe ring is a hollow cylinder, and the two ends of the nozzle pipe ring are connected with the nozzle pipelines on the two sides, respectively. The two sides of the outer side wall of the nozzle pipe ring are respectively provided with eyelets, and the positions of the two eyelets correspond to each other. The eyelets connect the external and internal spaces of the nozzle pipe ring.

[0007] The eyelet is trumpet-shaped, the end of the eyelet facing the inside of the nozzle pipe ring is the tail part, the end of the eyelet facing the outside of the nozzle pipe ring is the head part, the inner diameter of the tail part of the eyelet is larger than the inner diameter of the head part, so that the head part of the eyelet can constrain the position of the nozzle, and the nozzle is prevented from being pushed out of the nozzle pipe ring by the gasification agent.

[0008] Optionally, the shape of the outer side wall of the nozzle is matched with the shape of the corresponding eyelet, and the end of the nozzle facing the inside of the nozzle pipe ring is the tail part, and the end of the nozzle facing the outside of the nozzle pipe ring is the head part. The outer diameter of the tail part of the nozzle is larger than the outer diameter of the head part.

[0009] The inner side wall of the nozzle encloses an inner hole, the outer end of the inner hole faces the outside of the nozzle pipe ring, and the inner end of the inner hole faces the inside of the nozzle pipe ring, so that the gasification agent in the inside of the nozzle pipe ring is sprayed out in a diffusion manner through the inner hole.

[0010] Further, a clamping groove is arranged at the inner side of the hole and close to the tail of the hole, the diameter of the clamping groove is slightly larger than the maximum inner diameter of the hole, and the clamping groove is used for clamping the clamping ring; the inner diameter of the clamping ring is smaller than the outer diameter of the tail of the nozzle.

[0011] After the nozzle is installed in the hole, the clamping ring is inserted into the clamping groove, at this time, the clamping ring is between the tail of the nozzle and the tail of the hole, and the nozzle can be prevented from being separated from the tail of the hole and entering the inside of the nozzle pipe ring.

[0012] Further, the clamping ring is circular and has a truncated notch, so that the clamping ring has elasticity and can be inserted into the clamping groove of the hole.

[0013] Optionally, the distance between two adjacent nozzles on the same side of the nozzle pipe line is 3-5 m along the length direction of the nozzle pipe line; and the lengths of all the nozzle pipe rings are equal.

[0014] Optionally, when a plurality of injection wells are arranged in a row to gasify underground coal, a horizontal well is drilled to the bottom of each injection well towards the injection wells on the left and right sides, the drill bit leads the nozzle pipe line to extend in the injection well and the horizontal well, the total length of the nozzle pipe line on one side of the bottom of the injection well is 1 / 2 of the distance between the adjacent two injection wells, and is approximately 150 m, 200 m or 250 m, and the average diameters of the nozzles corresponding to the three types are 9 mm, 7.8 mm and 7 mm respectively.

[0015] Optionally, the length of the nozzle pipe ring is 100-200 mm, the length of the nozzle pipe ring is too short to cause stress concentration, and the welding opening between the nozzle and the nozzle pipe ring is prone to cracking; the inner diameter of the nozzle pipe ring is 100 mm, and the outer diameter is 124 mm; the inner diameter of the tail of the hole is 15-16 mm, and the inner diameter of the head of the hole is 14-15 mm; preferably, the diameter of the clamping groove is 16 mm.

[0016] Optionally, the outer diameter of the tail of the nozzle is 15-16 mm, the outer diameter of the head of the nozzle is 14-15 mm, the height of the inner hole of the nozzle is 9 mm, and the inner diameter of the inner wall of the hole between the tail of the nozzle and the tail of the hole is consistent, so that the nozzle can be inserted into the hole.

[0017] The inner diameter of the outer end of the inner hole is 10 mm, and the inner diameter of the inner end of the inner hole is 6.5-9.5 mm.

[0018] The nozzle diameter, nozzle line length, and number of installed nozzles are related. The sum of the inner diameters of all nozzles roughly corresponds to the inner diameter of the nozzle line. As the distance between adjacent nozzles on the same side of a nozzle line increases (for example, to more than 3 meters), the inner diameter of the inner end of the inner eyelet also increases appropriately.

[0019] Further optionally, when the length of the nozzle pipeline is 150 meters, the inner diameter of the inner end of the inner hole is 8.5-9.5 mm; when the length of the nozzle pipeline is 200 meters, the inner diameter of the inner end of the inner hole is 7.3-8.3 mm; when the length of the nozzle pipeline is 250 meters, the inner diameter of the inner end of the inner hole is 6.5-7.5 mm.

[0020] Further optionally, the inner diameters of the inner ends of the inner holes of several nozzles on the same side of the nozzle pipeline are reduced in steps, that is, 5-10 adjacent nozzles form a step section, and the inner diameters of the inner ends of the inner holes of the nozzles in the same step section are the same.

[0021] Optionally, before the gasification agent is sprayed, a high-temperature resistant resin is used to fill the inner hole. When the coal is ignited and gasified underground, the resin automatically melts in the high-temperature environment and the nozzle opens. For example, the high-temperature resistant resin can withstand temperatures above 200°C.

[0022] During underground coal gasification, the drill bit guides the nozzle pipeline into the injection well. When the thickness of a single coal seam exceeds 10 meters, the diameters of the injection and production wells can be increased. The diameter of the nozzle pipeline and the inner and outer diameters of the nozzles can also be appropriately increased to increase production capacity. The diameters of the nozzle pipeline and nozzles are determined by the amount of gasifying agent injected.

[0023] The nozzle pipeline designed by the present invention has reasonable size design, and the appropriate inner hole size is matched with the nozzle spacing and the nozzle pipe ring size, so that the release of the gasifying agent is relatively uniform, the overall structural reliability of the nozzle pipeline is good, and the service life of the nozzle pipeline is extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural diagram of the nozzle pipeline and the nozzle pipe ring;

[0025] Figure 2 is a schematic diagram of the holes on the nozzle tube ring;

[0026] Figure 3 It is a schematic diagram of the nozzle installed in the hole;

[0027] Figure 4 Schematic diagram of the clamping ring.

[0028] In the accompanying drawings, 1-nozzle pipeline, 2-clamp ring, 3-nozzle pipe ring, 4-eyelet, 5-inner eyelet, 6-nozzle, 7-groove. DETAILED DESCRIPTION

[0029] Example 1

[0030] This embodiment provides a multi-nozzle balanced gas injection system for underground coal gasification. Figures 1-4 As shown, it includes a drill bit and a nozzle pipeline 1 connected to each other, and a plurality of nozzle pipe rings 3 are provided on the nozzle pipeline 1. The plurality of nozzle pipe rings 3 are evenly arranged along the length direction of the nozzle pipeline 1;

[0031] Two holes 4 are provided in the middle of the nozzle pipe ring 3, each for mounting a nozzle 6. The two holes 4 are symmetrically arranged with the central axis of the nozzle pipe ring as the center, so that the two nozzles 6 release the gasifying agent toward both sides of the nozzle pipeline 1 respectively.

[0032] The inner diameter of the outer end of the inner hole 5 of the nozzle 6 is larger than the inner diameter of the inner end, and the inner diameter of the outer ends of the inner holes 5 of all nozzles is the same; starting from the drill bit and along the length direction of the nozzle pipeline, the inner diameter of the inner ends of the inner holes 5 of several nozzles on the same side of the nozzle pipeline gradually decreases, so that each nozzle 6 on the same side of the nozzle pipeline sprays the same amount of gasifying agent in the same time, ensuring that the nozzle pipeline releases the gasifying agent evenly.

[0033] The nozzle ring 3 is a hollow cylinder, with both ends of the nozzle ring 3 connected to the coiled tubing 2 on both sides. Holes 4 are provided on both sides of the outer wall of the nozzle ring 3. The positions of the two holes 4 correspond to each other, and the holes connect the outside and the inside of the nozzle ring.

[0034] The hole 4 is trumpet-shaped, with the end of the hole 4 facing the inside of the nozzle tube ring being the tail, and the end facing the outside of the nozzle tube ring being the head. The inner diameter of the hole tail is larger than the inner diameter of the head, so that the head of the hole can constrain the position of the nozzle and prevent the nozzle from being pushed out of the nozzle tube ring by the gasifying agent.

[0035] The shape of the outer wall of the nozzle 6 is adapted to the shape of the corresponding hole 4, and the end of the nozzle facing the inside of the nozzle tube ring is the tail, and the end facing the outside of the nozzle tube ring is the head. The outer diameter of the nozzle tail is larger than the outer diameter of the head.

[0036] The inner side wall of the nozzle 6 forms an inner hole 5, the outer end of the inner hole faces the outside of the nozzle ring, and the inner end of the inner hole faces the inside of the nozzle ring, so that the gasifying agent inside the nozzle ring 3 is sprayed out in a diffused manner through the inner hole 5.

[0037] A circle of clamping grooves 7 is provided inside the eyelet 4 and near the tail of the eyelet. The diameter of the clamping grooves 7 is slightly larger than the maximum inner diameter of the eyelet 4 and is used to clamp the clamping ring 2. The inner diameter of the clamping ring 2 is smaller than the outer diameter of the tail of the nozzle.

[0038] After the nozzle is installed inside the hole, insert the clamping ring into the groove. At this time, the clamping ring is between the tail of the nozzle and the tail of the hole, which can prevent the nozzle from falling out from the tail of the hole to the inside of the nozzle pipe ring.

[0039] The clamping ring 2 is circular and has a truncated notch, so that the clamping ring has elasticity and can be inserted into the clamping groove of the eyelet.

[0040] Along the length of the nozzle pipeline, the distance between two adjacent nozzles on the same side of the nozzle pipeline is 3m, that is, the length of the nozzle pipeline between the two nozzle pipe rings and the nozzle pipe ring connected on one side is 3m; the lengths of all nozzle pipe rings are equal.

[0041] The length of the nozzle tube ring is 100mm, the length of the nozzle pipeline between the two nozzle tube rings is 2.9m, the inner diameter is 100mm, and the outer diameter is 124mm; the inner diameter of the eyelet tail is 15mm, and the inner diameter of the eyelet head is 14mm; the diameter of the slot is 16mm, and the diameter of the slot in its natural state is 17mm.

[0042] The nozzle is made of tungsten alloy, with an outer diameter of 15mm at the tail end of the nozzle and 14mm at the head end of the nozzle. The height of the inner hole of the nozzle is 9mm, and the inner diameter of the inner wall of the hole between the tail end of the nozzle and the tail end of the hole is consistent, making it easy to insert the nozzle into the hole.

[0043] The inner diameter of the outer end of the inner hole is 10 mm, and the inner diameter of the inner end of the inner hole is 8.5-9.5 mm, so that the gasifying agent is in a divergent state when sprayed out, which is conducive to the uniform dispersion of the gasifying agent.

[0044] When several injection wells are arranged in a row to gasify underground coal, horizontal wells are drilled from the bottom of an injection well toward the injection wells on the left and right sides. The drill bit leads the nozzle pipeline to extend in the injection well and the horizontal well. The total length of the nozzle pipeline on one side of the bottom of the injection well is 1 / 2 of the distance between the two adjacent injection wells. The nozzle pipeline length of this embodiment is 150 meters. The average inner diameter of the inner holes of all nozzles is 9 mm. Taking 9 mm as the median, 50 pairs of nozzles (100 nozzles) are installed. Starting from near the drill bit, 5 pairs of 9.5mm nozzles are installed, 5 pairs of 9.4mm nozzles are installed, 5 pairs of 9.3mm nozzles are installed, 5 pairs of 9.2mm nozzles are installed, 5 pairs of 9.1mm nozzles are installed, 5 pairs of 8.9mm nozzles are installed, 5 pairs of 8.8mm nozzles are installed, 5 pairs of 8.7mm nozzles, 5 pairs of 8.6mm nozzles are installed, and 5 pairs of 8.5mm nozzles are installed.

[0045] The nozzle line and the nozzle ring are made of the same material, which is a high-temperature resistant flexible material, so that the drill bit can lead the nozzle line and the nozzle ring to move in the injection well and the horizontal well.

[0046] Before the gasifier is sprayed, a high-temperature resistant resin is used to fill the inner hole. When the coal is ignited and gasified underground, the resin automatically melts in the high-temperature environment and the nozzle opens. For example, the high-temperature resistant resin can withstand temperatures above 200°C.

[0047] This embodiment uses thermal-structural coupling analysis and finite element simulation (ANSYS) to verify the rationality of the above structural design. The results are as follows:

[0048] The external industrial control conditions of the nozzle pipeline are: 650-900℃ in the coal seam reaction zone and a maximum pressure of 35MPa;

[0049] The internal gasifier operating conditions of the nozzle pipeline are: maximum pressure 35Mpa, maximum temperature 900℃;

[0050] It can ensure that the amount of gasifying agent (mixed gas of water vapor and air) sprayed out by each nozzle per second is equal;

[0051] Gasification uniformity: nozzle flow deviation <5%;

[0052] Structural reliability: Under 35MPa formation pressure and 25MPa internal pressure, the maximum deformation of the nozzle ring is less than 0.1% of the nozzle pipeline length;

[0053] Improved service life: The service life of the nozzle tube ring is more than 1 year.

[0054] Example 2

[0055] This embodiment provides a multi-nozzle balanced gas injection system for underground coal gasification, which is the same as Example 1, except that the length of the nozzle pipe ring is 0.21m. The length of the nozzle pipe ring is too long, which affects the overall flexibility of the nozzle pipeline and cannot be normally led by the drill bit for drilling.

[0056] Example 3

[0057] This embodiment provides a multi-nozzle balanced gas injection system for underground coal gasification, which is the same as Example 1, except that the distance between two adjacent nozzles on the same side of the nozzle pipeline is 3.1m, and the length of the nozzle pipe ring is still 0.1m. For the nozzle pipeline of the same length as a whole, the reduction in the number of nozzle pipe rings will affect the sufficient supply of gasification agent, and the nozzle diameter must be increased accordingly. The increase in nozzle diameter will lead to an increase in the wall thickness of the nozzle pipe ring, affecting the overall flexibility of the nozzle pipeline, which cannot be normally led by the drill bit for drilling, and will lead to changes in the wellbore structure and a series of tools.

[0058] Example 4

[0059] This embodiment provides a multi-nozzle balanced gas injection system for underground coal gasification, which is the same as Example 1, except that the distance between two adjacent nozzles on the same side of the nozzle pipeline is 2.9m, and the length of the nozzle pipe ring is still 0.1m. For the nozzle pipeline of the same length as a whole, the number of nozzle pipe rings increases, resulting in a decrease in the flexibility of the entire nozzle pipeline, affecting the bending of the nozzle pipeline, and thus affecting construction.

[0060] Example 5

[0061] This embodiment provides a multi-nozzle balanced gas injection system for underground coal gasification, which is the same as Example 1, except that the inner diameter of the outer end of the inner hole is 9 mm, and the gasification agent is not well dispersed when sprayed, which is not conducive to uniform dispersion of the gasification agent.

[0062] Example 6

[0063] This embodiment provides a multi-nozzle balanced gas injection system for underground coal gasification, which is the same as Example 1, except that the inner diameter of the outer end of the inner hole is 11 mm, resulting in the wall thickness of the nozzle head being too thin, which is not conducive to resisting the strong friction loss generated by the high-pressure airflow ejected from the nozzle, resulting in a shortened nozzle life.

[0064] Example 7

[0065] This embodiment provides a multi-nozzle balanced gas injection system for underground coal gasification, which is the same as Example 1, except that the nozzle pipeline length is 200 meters, the average inner diameter of the inner holes of all nozzles is 7.8 mm, and 66 pairs of nozzles (132 nozzles) are installed with 7.8 mm as the median. Starting from near the drill bit, 6 pairs of 8.3 mm nozzles are installed, 6 pairs of 8.2 mm nozzles are installed, 6 pairs of 8.1 mm nozzles are installed, 6 pairs of 8.0 mm nozzles are installed, 6 pairs of 7.9 mm nozzles are installed, 6 pairs of 7.8 mm nozzles are installed, 6 pairs of 7.7 mm nozzles are installed, 6 pairs of 7.6 mm nozzles are installed, 6 pairs of 7.5 mm nozzles are installed, 6 pairs of 7.4 mm nozzles are installed, and 6 pairs of 7.3 mm nozzles are installed.

[0066] Example 8

[0067] This embodiment provides a multi-nozzle balanced gas injection system for underground coal gasification, which is the same as Example 1, except that the nozzle pipeline length is 250 meters, the average inner diameter of the inner holes of all nozzles is 7 mm, and 83 pairs of nozzles (166 nozzles) are installed with 7 mm as the median. Starting from near the drill bit, 8 pairs of 7.5 mm nozzles are installed, 7 pairs of 7.4 mm nozzles are installed, 8 pairs of 7.3 mm nozzles are installed, 7 pairs of 7.2 mm nozzles are installed, 8 pairs of 7.1 mm nozzles are installed, 7 pairs of 7.0 mm nozzles are installed, 8 pairs of 6.9 mm nozzles are installed, 7 pairs of 6.8 mm nozzles are installed, 8 pairs of 6.7 mm nozzles are installed, 7 pairs of 6.6 mm nozzles are installed, and 8 pairs of 6.5 mm nozzles are installed.

Claims

1. A multi-nozzle balanced gas injection system for underground coal gasification, characterized in that: The drill bit and the nozzle pipeline are connected to each other, and the nozzle pipeline is provided with a plurality of nozzle rings, and the plurality of nozzle rings are evenly arranged along the length direction of the nozzle pipeline; There are two holes in the middle of the nozzle ring, each for installing a nozzle. The two holes are symmetrically arranged with the central axis of the nozzle ring as the center, so that the two nozzles release the gasifying agent to both sides of the nozzle pipeline respectively. The inner diameter of the outer end of the inner hole of the nozzle is larger than the inner diameter of the inner end, and the inner diameter of the outer end of the inner hole of all nozzles is the same; starting from the drill bit and along the length direction of the nozzle pipeline, the inner diameter of the inner end of the inner hole of several nozzles on the same side of the nozzle pipeline gradually decreases, so that each nozzle on the same side of the nozzle pipeline sprays the same amount of gasifying agent in the same time, ensuring that the nozzle pipeline releases the gasifying agent evenly.

2. The multi-nozzle balanced gas injection system according to claim 1, characterized in that: The nozzle tube ring is a hollow cylinder, and the two ends of the nozzle tube ring are respectively connected to the nozzle pipelines on both sides; holes are respectively provided on both sides of the outer wall of the nozzle tube ring, and the positions of the two holes correspond to each other, and the holes connect the outside and the internal space of the nozzle tube ring; The hole is trumpet-shaped, with the end of the hole facing the inside of the nozzle tube ring being the tail, and the end facing the outside of the nozzle tube ring being the head. The inner diameter of the tail of the hole is larger than the inner diameter of the head, so that the head of the hole can constrain the position of the nozzle and prevent the nozzle from being pushed out of the nozzle tube ring by the gasifying agent.

3. The multi-nozzle balanced gas injection system according to claim 1, characterized in that: The shape of the outer wall of the nozzle is adapted to the shape of the corresponding hole, and the end of the nozzle facing the inside of the nozzle tube ring is the tail, and the end facing the outside of the nozzle tube ring is the head. The outer diameter of the nozzle tail is larger than the outer diameter of the head. The inner wall of the nozzle forms an inner hole, the outer end of the inner hole faces the outside of the nozzle tube ring, and the inner end of the inner hole faces the inside of the nozzle tube ring, so that the gasifying agent inside the nozzle tube ring is sprayed out in a diffused shape through the inner hole.

4. The multi-nozzle balanced gas injection system according to claim 3, characterized in that: A circle of clamping grooves is provided inside the eyelet and near the tail of the eyelet. The diameter of the clamping groove is slightly larger than the maximum inner diameter of the eyelet and is used to clamp the clamping ring. The inner diameter of the clamping ring is smaller than the outer diameter of the tail of the nozzle. After the nozzle is installed inside the eyelet, insert the clamping ring into the groove. At this time, the clamping ring is between the tail of the nozzle and the tail of the eyelet, which can prevent the nozzle from falling out from the tail of the eyelet to the inside of the nozzle tube ring.

5. The multi-nozzle balanced gas injection system according to claim 4, characterized in that: The clamping ring is circular and has a truncated notch, so that the clamping ring has elasticity and can be inserted into the clamping groove of the eyelet.

6. The multi-nozzle balanced gas injection system according to claim 1, characterized in that: Along the length of the nozzle pipeline, the distance between two adjacent nozzles on the same side of the nozzle pipeline is 3-5m; the length of all nozzle pipe rings is equal.

7. The multi-nozzle balanced gas injection system according to claim 6, characterized in that: The length of the nozzle tube ring is 100-200 mm, the inner diameter of the hole tail is 15-16 mm, and the inner diameter of the hole head is 14-15 mm.

8. The multi-nozzle balanced gas injection system according to claim 1, characterized in that: The outer diameter of the tail of the nozzle is 15-16 mm, the outer diameter of the head of the nozzle is 14-15 mm, and the inner diameter of the inner wall of the hole between the tail of the nozzle and the tail of the hole is consistent, so that the nozzle is easy to insert into the hole; The inner diameter of the outer end of the inner eyelet is 10 mm, and the inner diameter of the inner end of the inner eyelet is 6.5-9.5 mm.

9. The multi-nozzle balanced gas injection system according to claim 8, characterized in that: When the length of the nozzle pipeline is 150 meters, the inner diameter of the inner end of the inner hole is 8.5-9.5 mm; when the length of the nozzle pipeline is 200 meters, the inner diameter of the inner end of the inner hole is 7.3-8.3 mm; when the length of the nozzle pipeline is 250 meters, the inner diameter of the inner end of the inner hole is 6.5-7.5 mm.

10. The multi-nozzle balanced gas injection system according to claim 8, characterized in that: The inner diameters of the inner ends of the inner holes of the nozzles on the same side of the nozzle pipeline are reduced in steps, 5-10 adjacent nozzles form a step, and the inner diameters of the inner ends of the inner holes of the nozzles in the same step are the same.

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