Laval nozzles and spraying apparatus

Abstract

The application discloses a Laval nozzle and a spraying device. The Laval nozzle is in a straight cylinder shape, and an inner flow channel of the Laval nozzle comprises a converging section, a diverging section and a throat formed between the converging section and the diverging section. The length-diameter ratio of the Laval nozzle is (25-50):1, and the length ratio of the converging section to the diverging section is 1:(2-3). The technical scheme of the application optimizes the length-diameter ratio and the converging ratio of the Laval nozzle, reduces turbulence and lowers energy loss of airflow in the spraying process under the premise of ensuring sufficient compression and acceleration of the airflow, ensures the speed and direction of the sprayed particles, and improves the spraying efficiency and quality.

Description

Technical Field

[0001] This application relates to the field of spraying technology, and in particular to a Laval nozzle and spraying equipment. Background Technology

[0002] Spray coating technology, as an important surface treatment and functionalization method, plays an irreplaceable role in many industrial fields such as aerospace, automobile manufacturing, energy equipment, and biomedicine. The Laval nozzle is a typical supersonic nozzle, which accelerates gas from subsonic to supersonic speeds through a unique contraction-expansion flow channel design. In spray coating technology, Laval nozzles designed based on the Laval nozzle principle are widely used in advanced processes such as plasma spraying, high-velocity oxygen fuel (HVOF) spraying, and cold spraying.

[0003] Currently, most mainstream Laval nozzles on the market employ a high contraction ratio design, which achieves rapid compression and acceleration of the airflow in the contraction section through a large ratio of inlet diameter to throat diameter. Theoretically, this design maximizes the outlet velocity of the airflow. However, in practical applications, the high contraction ratio causes a sharp turn in the airflow from the end of the contraction section to the inlet of the expansion section. This abrupt change in the flow channel cross-section triggers boundary layer separation and airflow swirling, forming a significant turbulent region. This easily leads to energy loss in the airflow, reducing spraying efficiency and quality.

[0004] Therefore, it is necessary to improve the structure of the Laval nozzle. Utility Model Content

[0005] This application provides a Laval nozzle and spraying equipment, aiming to solve the problem that the existing Laval nozzle has large peripheral turbulence during use, which easily causes loss of airflow energy and reduces spraying efficiency and quality.

[0006] To achieve the above objectives, this application proposes a Laval nozzle. The Laval nozzle has an overall cylindrical shape, and its internal flow channel includes a constriction section, an expansion section, and a throat formed between the constriction section and the expansion section; the length-to-diameter ratio of the Laval nozzle is (25-50):1, and the length ratio of the constriction section to the expansion section is 1:(2-3). In some embodiments, the wall thickness of the Laval nozzle is 1 to 2 mm.

[0007] In some embodiments, the ratio of the diameter of the inlet end of the constriction section to the diameter of the throat and the diameter of the outlet end of the expansion section is (1.5 to 1.75): 1: (1.75 to 2).

[0008] In some embodiments, a recess is formed on the outer circumference of the Laval nozzle near the incident end, the length of the recess is greater than the depth of the inner hole to which it is fitted, and the depth of the recess is between 0.1 and 0.2 mm.

[0009] In some embodiments, the filling shape of both the contraction segment and the expansion segment is frustum-shaped.

[0010] This application also provides a spraying device, including the Laval nozzle as described above.

[0011] This application proposes a Laval nozzle. The Laval nozzle has an overall cylindrical shape, and its internal flow channel includes a contraction section, an expansion section, and a throat formed between the contraction and expansion sections. The length-to-diameter ratio of the Laval nozzle is (25-50):1, and the length ratio of the contraction to expansion sections is 1:(2-3). In this application, the longer length-to-diameter ratio helps maintain stable fluid flow, reducing boundary layer separation and turbulence. Simultaneously, optimizing the length ratio of the contraction to expansion sections helps optimize the fluid acceleration process and also reduces turbulence generation. Therefore, this application, through optimizing the length-to-diameter ratio and contraction ratio of the Laval nozzle, reduces turbulence to lower energy loss during spraying while ensuring sufficient airflow compression and acceleration, thus ensuring the velocity and direction of the sprayed particles and improving spraying efficiency and quality. This application also proposes a spraying device including this Laval nozzle. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a cross-sectional structural schematic diagram of a Laval nozzle according to an embodiment of this application. Detailed Implementation

[0013] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0014] See Figure 1As shown, this application proposes a Laval nozzle 100. The Laval nozzle 100 is generally cylindrical, and its internal flow channel includes a contraction section 10, an expansion section 20, and a throat 30 formed between the contraction section 10 and the expansion section 20. The length-to-diameter ratio of the Laval nozzle is (25-50):1, and the length ratio of the contraction section 10 to the expansion section 20 is 1:(2-3). A larger length-to-diameter ratio means that there is sufficient space inside the nozzle for fluid acceleration and stabilization, thereby improving spraying efficiency and quality. A reasonable length ratio of the contraction section 10 to the expansion section 20 ensures that the fluid is smoothly accelerated to the throat 30 in the contraction section 10 and continues to accelerate to supersonic speeds in the expansion section 20, while avoiding excessive pressure gradients that could lead to turbulence.

[0015] In summary, the technical solution of this application can reduce turbulence by optimizing the length ratio and aspect ratio, thereby reducing the energy loss of the airflow during the spraying process, helping to maintain the speed and direction of the sprayed particles, and improving the spraying efficiency and quality.

[0016] The Laval Nozzle 100 features a wall thickness of 1–2 mm. While ensuring a lightweight nozzle, it provides sufficient mechanical strength to resist the erosion and wear of high-speed airflow (especially with spray media containing solid particles). The 1–2 mm wall thickness, achieved by using high-hardness, wear-resistant materials (such as low-carbon, medium-carbon, and high-carbon steel), fully leverages the material's wear resistance, extending service life. Furthermore, compared to thinner designs, a 1–2 mm wall thickness provides better heat conduction and dissipation, reducing the impact of thermal deformation on nozzle geometry.

[0017] Furthermore, the ratio of the diameter of the inlet end of the contraction section 10 to the diameter of the throat 30 and the diameter of the outlet end of the expansion section 20 is (1.5~1.75):1:(1.75~2). This allows for smooth acceleration of the fluid in the contraction section 10 with controllable pressure and temperature changes, successful attainment of the critical state in the throat 30, and full acceleration to supersonic speed in the expansion section 20 while avoiding shock waves. In terms of spraying performance, it improves spray speed and uniformity, thereby reducing coating porosity, increasing bonding strength, and improving coating quality. It also reduces high-speed airflow erosion damage to the nozzle itself, optimizes material performance to enhance wear resistance, improves heat conduction and heat dissipation, reduces thermal deformation to improve thermal stability, thus extending nozzle lifespan and ensuring stable operation.

[0018] Furthermore, a recessed platform 40 is formed on the outer circumference of the Laval nozzle 100 near the incident end, such as Figure 1As shown, the length of the recess 40 is greater than the depth of the inner hole to which it is assembled, and the depth of the recess 40 is between 0.1 and 0.2 mm. This ensures that the diameter of the portion of the Laval nozzle near the injection end is slightly smaller than the diameter of the other portions, allowing the Laval nozzle to be inserted more smoothly into the corresponding inner hole during assembly. This avoids jamming or damage due to dimensional tolerances or assembly errors.

[0019] Furthermore, both the contraction section 10 and the expansion section 20 are filled in a frustum shape. This frustum-shaped structural design not only facilitates manufacturing but also effectively reduces fluid disturbance during flow, further improving the fluid's acceleration efficiency and flow stability.

[0020] In a specific example, the total length of the Laval nozzle 100 in this application is 150 mm, wherein the length of the contraction section 10 is 50 mm, the length of the expansion section 20 is 100 mm, the outer diameter of the nozzle is 6 mm, the diameter of the throat 30 is 2.5 mm, the diameter of the inlet end of the contraction section 10 is 3.8 mm, and the diameter of the outlet end of the expansion section 20 is 4.5 mm; the length of the recess 40 is 30 mm, and the depth of the recess 40 is 0.15 mm.

[0021] This application also provides a method for processing the Laval nozzle of this application, comprising: 1. Design and manufacture various lengths of steel nozzle pipes. Nozzle materials include: stainless steel pipes, tool steel pipes, tungsten steel pipes, copper pipes, and welded composite pipes. 2. Use electrical discharge machining to machine tapered holes at both ends of the nozzle tube, forming a contraction section and an expansion section respectively; 3. Use polishing to remove burrs and rough surfaces inside the holes; 4. Use external cylindrical grinding to grind the inlet end of the multi-nozzle pipe, controlling the grinding length and depth; 5. Inspect the packaging and send it for connector matching test.

[0022] This application also provides a spraying apparatus, including the Laval nozzle 100 as described above. This spraying apparatus also employs all the technical solutions of all embodiments of the Laval nozzle described above, and therefore possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated upon here.

[0023] The above description is only a part or preferred embodiment of this application. Neither the text nor the drawings should limit the scope of protection of this application. All equivalent structural transformations made using the content of this application's specification and drawings under the overall concept of this application, or direct / indirect applications in other related technical fields, are included within the scope of protection of this application.

Claims

1. A Laval nozzle, characterized in that, The Laval nozzle has an overall cylindrical shape, and its internal flow channel includes a constriction section, an expansion section, and a throat formed between the constriction section and the expansion section; the length-to-diameter ratio of the Laval nozzle is (25-50):1; the length ratio of the constriction section to the expansion section is 1:(2-3).

2. The Laval nozzle according to claim 1, characterized in that, The wall thickness of the Laval nozzle is 1-2 mm.

3. The Laval nozzle according to claim 1, characterized in that, The ratio of the diameter of the inlet end of the contraction section to the diameter of the throat and the diameter of the outlet end of the expansion section is (1.5~1.75):1:(1.75~2).

4. The Laval nozzle according to claim 1, characterized in that, A recess is formed on the outer circumference of the Laval nozzle near the incident end. The length of the recess is greater than the depth of the inner hole to which it is fitted, and the depth of the recess is between 0.1 and 0.2 mm.

5. The Laval nozzle according to claim 1, characterized in that, Both the contraction section and the expansion section are filled in a frustum shape.

6. A spraying device, characterized in that, Includes the Laval nozzle as described in any one of claims 1-5.

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