WO2022051912A1

WO2022051912A1 - Laval nozzle and manufacturing method therefor

Info

Publication number: WO2022051912A1
Application number: PCT/CN2020/114078
Authority: WO
Inventors: 李长鹏; 张卿卿; 吴琪; 陈国锋
Original assignee: 西门子股份公司; 西门子（中国）有限公司
Priority date: 2020-09-08
Filing date: 2020-09-08
Publication date: 2022-03-17
Also published as: CN115989325A

Abstract

A Laval nozzle (100) and a manufacturing method therefor. The Laval nozzle (100) comprises: a housing (160); a first cooling liquid channel (110), which is disposed in a first accommodating space and is provided with a cooling liquid inlet (110a); a second cooling liquid channel (120), which is disposed in the first accommodating space and is provided with a cooling liquid outlet (120a), wherein the first cooling liquid channel (110) and the second cooling liquid channel (120) are in communication with each other and are provided with cooling liquids that flow circularly; a first oxygen channel (130), which accommodates oxygen and transfers same to an air outlet of the Laval nozzle (100); an oxygen cavity (180); a diffusion wall (170), which is disposed at the bottom of the Laval nozzle (100) and transversely extends to the housing (160); and a second oxygen channel (140), wherein a bottom opening of the second oxygen channel (140) peripherally transversely extends to the housing (160) so as to form an isolation wall (150), and a second accommodating space is provided between the isolation wall (150) and the diffusion wall (170), such that the oxygen is transferred from the first oxygen channel (130) to the second oxygen channel (140) and is diffused in the second accommodating space through a plurality of air holes in the diffusion wall (170), thereby improving the cooling efficiency of the Laval nozzle (100) and prolonging the service life thereof.

Description

Laval nozzle and method of making the same

technical field

The invention relates to the field of additive manufacturing, in particular to a Laval nozzle and a manufacturing method thereof.

Background technique

As shown in FIG. 1 and FIG. 2 , the Laval nozzle 220 is a key element of the steelmaking furnace 300 , which is arranged at the lower end of the oxygen pipe 210 and is used to remove the molten steel 310 of the steelmaking furnace 300 by spraying the oxygen supplementary blowing amount. impurities such as carbon, silicon, manganese and phosphorus. Among them, the Laval nozzle 220 as the main element is used to act as the outlet of oxygen, and it has the precisely machined air outlet 222 to obtain the ideal flow and parameters, in addition, the Laval nozzle 220 has a first cooling liquid channel 224 and The second cooling liquid passage 226 , the first cooling liquid passage 224 and the second cooling liquid passage 226 have circulating cooling liquid in them to avoid overheating and damage of the Laval nozzle 220 . Wherein, the first cooling liquid channel 224 is used for serving as a cooling liquid inlet, and the second cooling liquid channel 226 is used for serving as a cooling liquid outlet.

In order to protect a typical Laval nozzle 220, it is necessary to utilize a high rate of cooling liquid (up to 60 cubic meters per hour). Furthermore, due to the difficulty of industrial manufacturing of the Laval nozzle 220, the cooling liquid piping design cannot be optimized. As shown in Figure 2, due to flow turbulence, there is a relatively slow flow area A in the Laval nozzle. Although the cooling liquid flow rate is very high, the cooling liquid is difficult to flow in areas like the area A and converge together. Dead water areas are created, which result in lower cooling rates and protection. Therefore, the Laval nozzle 220 is more prone to overheating or even damage in the region A.

As shown in the figure, in order to obtain sufficient oxygen outgassing efficiency, the Laval nozzle 220 is usually disposed close to the surface of the molten steel 310 whose temperature is greater than 2000 degrees Celsius. Due to the extremely high operating temperature, the cooling liquid inside the Laval nozzle 220 is not sufficient to keep the nozzle surface from melting or premature burnout. Among them, the grains of the copper forging may gradually grow, which may lead to degradation of the heat transfer coefficient and cooling efficiency of the Laval nozzle 220 . Degraded cooling efficiency can further increase the copper grain growth rate and cause rapid damage to the Laval nozzle 220 . The clogging of the molten steel 310 not only leads to corrosion of the Laval nozzle 220, but also further reduces its heat transfer coefficient and cooling efficiency.

Laval nozzles have a very low lifespan, usually oxygen nozzles are damaged and need to be replaced after 100 to 200 furnaces. Nozzle replacement is also troublesome. The nozzle tip to be replaced needs to be cut from the oxygen pipe 210 and re-welded with a new nozzle, which not only causes extra operating costs but also affects the normal production process. This also leads to material waste and affects regular steel production processes. In addition, to improve the cooling rate, the Laval nozzle 220 is copper forged, which has a high density and small grain size, which ensures a higher thermal conductivity than cast copper. The oxygen tube 210 is stainless steel and the Laval nozzle 220 is copper (the two are connected by welding. The high temperature gradient and different thermal expansion rates of stainless steel and copper can cause welding along the oxygen tube 210 and the Laval nozzle 220 The stitches are cracked, which can lead to premature failure. The Laval nozzle 220 cannot be repaired by compensating heating or coating due to the grown grain size and degraded thermal conductivity.

SUMMARY OF THE INVENTION

A first aspect of the present invention provides a Laval nozzle, wherein the Laval nozzle includes: a casing having a first accommodating space; a first cooling liquid channel disposed in the first accommodating space and having a cooling liquid inlet; a second cooling liquid channel, which is arranged in the first accommodating space and has a cooling liquid outlet, wherein the first cooling liquid channel and the second cooling liquid channel communicate with each other and have a circulating cooling liquid liquid; a first oxygen channel, which accommodates and transports oxygen to the air outlet of the Laval nozzle; an oxygen cavity, which is communicated with the first oxygen channel and transports oxygen for the first oxygen channel; a diffusion wall, It is arranged at the bottom of the Laval nozzle and extends laterally to the casing, a second oxygen channel, which is communicated with the first oxygen channel or the oxygen chamber, and the bottom opening of the second oxygen channel is laterally around. extending to the housing to form a partition wall, wherein there is a second containment space between the partition wall and the diffusion wall, so that oxygen is transported from the first oxygen channel to the second oxygen channel and at The second accommodating space is diffused through a plurality of air holes of the diffusion wall.

Further, the first oxygen channel passes through the second accommodating space and the diffusion wall, wherein the bottom opening of the first oxygen channel serves as the air outlet of the Laval nozzle.

Further, a plurality of supporting walls are vertically arranged between the partition wall and the diffusion wall.

Further, the support wall extends from the central region of the Laval nozzle to the periphery thereof.

Further, the thickness of the diffusion wall ranges from 3 mm to 10 mm.

Further, the diameter of the pore size of the diffusion wall ranges from 5 to 30 microns.

Further, the partition wall and the diffusion wall are made of metal.

Further, the partition wall and the diffusion wall are made of metallic copper.

A second aspect of the present invention provides a method for manufacturing a Laval nozzle, wherein an additive manufacturing process is used to manufacture the Laval nozzle according to the first aspect of the present invention.

Further, the Laval nozzle is manufactured in a selective laser melting facility.

The Laval nozzle provided by the present invention has various cooling strategies, and integrates sweat cooling technology and traditional cooling liquid cooling, which can achieve better cooling efficiency and prolong service life. The Laval nozzle provided by the present invention can reduce the grain size growth and the thermal conduction attenuation of the copper layer, and thus can achieve a longer working life. The Laval nozzle provided by the present invention can protect the nozzle from possible clogging and corrosion, and further improve the life of the nozzle. Since the present invention adds a sweat cooling strategy to the traditional cooling strategy, the demand for cooling water is reduced, thus saving cooling water and energy consumption, and saving energy. At the same time, the present invention utilizes a small amount of oxygen as the working gas and cooling medium, and does not affect the normal working environment.

In addition, although the diffusion layer of the present invention is provided with tiny pores therein as microchannels, the fabrication can be facilitated by an additive manufacturing process. Also, pore size and porosity can be adjusted by printing parameters for optimized cooling.

Description of drawings

Fig. 1 is the structural representation of the oxygen delivery device in the steelmaking furnace;

Figure 2 is a schematic cross-sectional view of a Laval nozzle of the prior art;

Figure 3 is a comparison diagram of cooling efficiency using different cooling strategies;

Fig. 4 is the principle schematic diagram of sweat cooling;

5 is a schematic cross-sectional view of a Laval nozzle according to an embodiment of the present invention.

detailed description

The specific embodiments of the present invention will be described below with reference to the accompanying drawings.

The invention provides a Laval nozzle and a manufacturing method thereof. The bottom of the nozzle adopts sweating and cooling technology. By setting a plurality of microchannels in the bottom diffusion layer, when oxygen flows out through the microchannels, a gas film is formed on the bottom surface. The surface heat of the Laval nozzle is removed for cooling purposes. Among them, the diffusion layer acts as an insulating layer and a cooling layer. And, if molten steel adheres to the diffusion layer, the oxygen flowing out through the microchannels of the diffusion layer can also blow the molten steel away. The present invention can be manufactured by additive manufacturing technology, which can achieve high cooling efficiency and increase Laval nozzle life.

Figure 3 is a comparison diagram of cooling efficiency using different cooling strategies. As shown in Figure 3, commonly used cooling strategies include impingement cooling A, convective cooling B, perspiration cooling C, and full-film cooling D, where the abscissa of the coordinate system is the cooling air flow and the ordinate is the cooling efficiency. As can be seen from FIG. 3 , the sweat cooling technology has the best cooling efficiency under the same cooling air flow, so the present invention chooses to adopt the sweat cooling strategy.

The direction of the arrow in FIG. 4 shows the flow direction of oxygen. The cooling gas from the cooling pipes penetrates through the porous walls and forms a cooling gas barrier to protect the components from corrosion by high heat fluxes. For the application scenario of the oxygen vent, a small part of the working gas in the oxygen will be utilized as the coolant for the intended sweat cooling strategy, without the need for additional cooling medium and incurring additional costs, as well as avoiding the impact on the working environment. Unlike other cooling strategies, such as film cooling, sweat cooling requires only a small amount of cooling gas flow to form a barrier that does not hinder the normal operating flow conditions of Laval nozzles. In addition to cooling with sweat, the gas barrier also protects the printhead from clogging or corrosion and further increases Laval nozzle life.

As shown in FIG. 5, the Laval nozzle 100 provided by the present invention includes a casing 160, a first cooling liquid channel 110, a second cooling liquid channel 120, a first oxygen channel 130, a plurality of air outlet holes 170a, and a second oxygen channel 140 , the partition wall 150 and the oxygen chamber 180 . Specifically, the housing 160 has a first accommodating space. The first cooling liquid passage 110 is provided in the first accommodating space and has a cooling liquid inlet 110a. The second cooling liquid channel 120 is disposed in the first accommodating space and has a cooling liquid outlet 120a, wherein the first cooling liquid channel 110 and the second cooling liquid channel 120 communicate with each other and have a circulating cooling liquid. The first oxygen channel 130 accommodates and delivers oxygen to the air outlet of the Laval nozzle 100 ; the oxygen chamber 180 communicates with the first oxygen channel 130 and delivers oxygen for the first oxygen channel 130 ; the diffusion wall 170 is provided At the bottom of the Laval nozzle 100 and extending laterally to the casing 160, the second oxygen channel 140 communicates with the first oxygen channel 130 or the oxygen chamber 180, and the bottom of the second oxygen channel 140 opens to the The periphery extends laterally to the outer shell 160 to form a partition wall 150, wherein a second accommodating space is provided between the partition wall 150 and the diffusion wall 170, so that a small amount of oxygen can flow from the first oxygen channel 130 or all the The oxygen chamber 180 is delivered to the second oxygen channel 140 and diffused through the plurality of air holes of the diffusion wall 170 in the second accommodating space.

Further, the first oxygen channel 130 passes through the second accommodating space and the diffusion wall 170 , wherein the bottom opening of the first oxygen channel 130 serves as the air outlet of the Laval nozzle 100 .

The Laval nozzle provided by the present invention is still directly cooled by the cooling liquid in the heat conduction mode through the high-density pure copper layer. The additional diffusion layer added to the front surface of the Laval nozzle is supplemented by the dendritic cooling liquid channels and oxygen pipes in the first accommodation space, so as to achieve the purpose of sweat cooling. The side walls of the dendritic coolant channels ensure the mechanical strength of the Laval nozzle, therefore, the coolant channels act as reinforcement. The present invention would further control the cooling liquid channel and the oxygen channel based on optimized cooling and airflow effects.

Since the main cooling mechanism of the diffusion layer is not direct heat conduction, it is not necessary to consider the grain size and concentration as the influencing factors of thermal conductivity. The barrier is protected from the high heat flux by the diffusion layer, so grain growth and degradation are significantly slower to maintain high thermal conductivity.

Considering the complex structure and internal cooling liquid channels, the Laval nozzle provided by the present invention has a porous diffusion layer and internal cooling channels, so it can be manufactured by additive manufacturing technology, and can be manufactured by adjusting the laser scanning strategy and printing parameters The pure copper isolation layer and the porous metal copper diffusion layer of the Laval nozzle of the present invention can also adjust the size and porosity of the holes based on design requirements, so as to achieve the expected cooling effect.

Further, a plurality of support walls 150a are vertically disposed between the partition wall 150 and the diffusion wall 170 .

Preferably, the support wall 150a extends from the central region of the Laval nozzle 100 to the periphery thereof.

In order to successfully form the gas film, the diameters of the diffusion wall and the size of the pores are also selected specifically, wherein the thickness of the diffusion wall 170 ranges from 3 mm to 10 mm, and the diameter of the size of the pores of the diffusion wall 170 ranges from 5 to 30 mm. microns.

Further, the partition wall and the diffusion wall are made of metal. Preferably, the partition wall and the diffusion wall are made of metallic copper. In addition, the improvement of cooling efficiency can reduce the requirements for the thermal conductivity of the separation wall and the diffusion wall, so that copper alloys that are more suitable for additive manufacturing processes can be selected instead of pure copper materials in material selection.

A second aspect of the present invention provides a method for manufacturing a Laval nozzle, characterized in that the Laval nozzle according to the first aspect of the present invention is manufactured using an additive manufacturing process. Preferably, the Laval nozzle is manufactured in a selective laser melting apparatus.

The Laval nozzle provided by the present invention has various cooling strategies, and integrates sweat cooling technology and traditional cooling liquid cooling to achieve better cooling efficiency. The Laval nozzle provided by the present invention can reduce the grain size growth and the thermal conduction attenuation of the copper layer, and thus can achieve a longer working life. The Laval nozzle provided by the present invention protects the spray head from possible clogging and corrosion, and further improves the life of the spray head. Since the present invention adds a sweat cooling strategy to the traditional cooling strategy, the demand for cooling water is reduced, thus saving cooling water and energy consumption, and saving energy. At the same time, the present invention utilizes a small amount of oxygen as the working gas and cooling medium, and does not affect the normal working environment.

While the content of the present invention has been described in detail by way of the above preferred embodiments, it should be appreciated that the above description should not be construed as limiting the present invention. Various modifications and alternatives to the present invention will be apparent to those skilled in the art upon reading the foregoing. Accordingly, the scope of protection of the present invention should be defined by the appended claims. Furthermore, any reference signs in a claim shall not be construed as limiting the claim involved; the word "comprising" does not exclude other claims or means or steps not listed in the specification; Words such as "two" are used only to denote names and do not denote any particular order.

Claims

A Laval nozzle, characterized in that the Laval nozzle (100) comprises:

a housing (160) having a first accommodating space;

a first cooling liquid passage (110), which is arranged in the first accommodating space and has a cooling liquid inlet (110a);

A second cooling liquid channel (120) is provided in the first accommodating space and has a cooling liquid outlet (120a), wherein the first cooling liquid channel (110) and the second cooling liquid channel (120) ) communicated and has a circulating cooling liquid;

a first oxygen channel (130) that accommodates and delivers oxygen to the air outlet of the Laval nozzle (100);

an oxygen chamber (180), which is communicated with the first oxygen channel (130) and delivers oxygen for the first oxygen channel (130);

a diffuser wall (170) disposed at the bottom of the Laval nozzle (100) and extending laterally to the housing (160),

The second oxygen channel (140) communicates with the first oxygen channel (130) or the oxygen cavity (180), and the bottom opening of the second oxygen channel (140) extends laterally to the outer casing (140). 160) to form a partition wall (150), wherein there is a second accommodation space between the partition wall (150) and the diffusion wall (170), so that oxygen is transported from the first oxygen channel (130) to the second oxygen channel (140) and diffuse through a plurality of air holes (170a) of the diffusion wall (170) in the second accommodation space.
The Laval nozzle according to claim 1, wherein the first oxygen channel (130) passes through the second accommodating space and the diffusion wall (170), wherein the first oxygen channel The bottom opening of (130) acts as the air outlet of the Laval nozzle (100).
The Laval nozzle according to claim 1, wherein a plurality of supporting walls (150a) are vertically arranged between the partition wall (150) and the diffusion wall (170).
The Laval nozzle according to claim 3, characterized in that the support wall (150a) extends from a central area of the Laval nozzle (100) to its periphery.
The Laval nozzle according to claim 1, wherein the thickness of the diffuser wall (170) ranges from 3 mm to 10 mm.
The Laval nozzle according to claim 1, wherein the diameter of the pores of the diffuser wall (170) ranges from 5 to 30 microns.
The Laval nozzle according to claim 1, wherein the partition wall (150) and the diffusion wall (170) are made of metal.
The Laval nozzle according to claim 7, wherein the partition wall (150) and the diffusion wall (170) are made of metallic copper.
A method for manufacturing a Laval nozzle, characterized in that the Laval nozzle according to any one of claims 1 to 7 is manufactured using an additive manufacturing process.
The method of manufacturing a Laval nozzle according to claim 9, wherein the Laval nozzle is manufactured in a selective laser melting apparatus.