RU2033864C1 - Gas-flame spraying burner - Google Patents

Abstract

FIELD: gas-thermal coatings. SUBSTANCE: end of tip has an additional cavity. An air nozzle has an additional bell mouth whose length is 0.07-0.5 of bell mouth diameter at the inlet with circular gap and gas nozzles inclined to the axis of central channel in the tip at 30-75 deg and 6-24 deg, respectively. The diameter of the bell mouth at the inlet ranges from 0.5-1.5 of the tip cavity diameter. Gas nozzle axes are disposed on the circle whose diameter is from 0.5 to 0.8 the diameter of the tip cavity. The tip has an additional row of gas nozzles arranged concentrically around the central channel. The additional row of gas nozzles is disposed on the circle whose diameter is 0.2-0.5 the diameter of the tip cavity. The total area of gas nozzles in the additional row is 0.1-0.5 the total area of the gas nozzles in the main row. The gas nozzles of the additional and main rows are slot-shaped. The gas nozzles of the additional row are set at an angle of 1-6 deg to the axis of the central channel. Depth of the tip cavity is 0.4-1.2 the cavity diameter. Width of the circular gap is 0.05-0.4 the cavity diameter. The air nozzle has an additional channel (or several channels) putting said circular gap at the outlet in communication with the atmosphere. The end of the tip is separable from the rest of the tip. Two washers in the tip function as valves and flame arresters. EFFECT: improved design. 13 cl, 2 dwg

Description

 The invention relates to thermal spray coatings, in particular to a flame spraying apparatus operating primarily on a mixture of gases of acetylene substitutes (methane, natural gas, propane-butane, etc.) with oxygen.

 Currently, flame spraying due to a number of advantages (mobility, simplicity of equipment, efficiency, versatility, etc.) has been widely used to obtain various types of coatings of wear-resistant, decorative, corrosion-resistant, anti-friction, lapping, anti-adhesive, reflective, temperature-controlled, sealing, and others.

 The further spread of this cost-effective method of spraying is hampered by an acute deficit of acetylene, so the replacement of acetylene with other combustible gases is of practical interest.

 Known burner for flame spraying, containing a spray head and a housing with channels for supplying combustible gas and an oxidizing agent. The mouthpiece includes a mouthpiece with a powder channel and gas nozzles concentrically arranged around it [1] When using acetylene substitute gases as combustible gas in this burner, the sprayed coatings easily peel off and have a non-marketable appearance.

The closest in technical essence and the achieved effect to the proposed one is a flame-spraying burner containing a housing with channels for supplying combustible gas, oxidizer and air, a mouthpiece with a central channel for supplying sprayed material, around which a series of gas nozzles are concentrically located, an air nozzle connected to the air supply channel, forming with the mouthpiece an annular gap with an angle of inclination to the axis of the mouthpiece [2]
The disadvantages of this burner are the low quality of coatings applied with the use of acetylene substitute gases as combustible gas, the large losses of the sprayed material caused by the low utilization rate of the sprayed material.

 The aim of the invention is to improve the quality of the applied coatings and reduce losses of the sprayed material.

The goal is achieved by the fact that in the burner for flame spraying, comprising a housing with channels for supplying combustible gas, an oxidizing agent and air, a mouthpiece with an end face and a central channel for supplying a spray material, around which a series of gas nozzles are concentrically arranged, an air nozzle connected to the air supply channel forming an annular gap with the mouthpiece with an angle of inclination to the axis of the mouthpiece, according to the invention, an additional cavity is made in the end face of the mouthpiece, and an additional 0.07-0.5 diameter bell is additionally made in the air nozzle pa funnel inlet at the angles of inclination to the central axis of the channel of the mouthpiece ^of the annulus 30-75 and 6-24 ^of gas nozzles, wherein the diameter of the socket inlet is 0.5-1.5 diameter die cavity.

 The axis of the gas nozzles can be made on a circle whose diameter is 0.5-0.8 of the diameter of the cavity at the end of the mouthpiece.

 An additional row of gas nozzles arranged concentrically around the central channel may be made in the mouthpiece.

 This additional row of gas nozzles can be located on a circle whose diameter is 0.2-0.5 of the diameter of the cavity in the end part of the mouthpiece.

 The total area of gas nozzles of the additional row may be 0.1-0.5 of the total area of gas nozzles of the main row.

 Gas nozzles of an additional row can be made in the form of grooves.

 Gas nozzles of the main row can be made in the form of grooves.

Gas nozzles additional number may be made at an angle ^of 1-6 to the central axis of the channel.

 The depth of the cavity in the end of the mouthpiece can be 0.4-1.2 of the diameter of the cavity.

 The width of the annular gap may be 0.05-0.4 diameter of the cavity.

 An additional channel (or channels) can be made in the air nozzle connecting the annular gap at the inlet with the surrounding atmosphere.

 The end part of the mouthpiece with a cavity can be made detachable relative to the rest of the mouthpiece.

 Two washers can be installed in the mouthpiece, acting as flame arresters and valves.

 The design of the flame spraying burner provides a significant increase in the thermal efficiency of the gas flame due to double compression of the gas-powder jet. Compression takes place in two zones of the gas-powder jet: in the cavity of the end part of the mouthpiece, i.e. in the zone of the hottest part of the gas flame and at the exit of the gas-powder jet from the cavity.

 In the first zone, the compression occurs under the action of the dynamic pressure of gas flames from gas nozzles radially located around the central channel, without the participation of an air flow, which eliminates any cooling of the flame in its hot zone.

 In the second zone, the compression occurs under the action of a powerful air stream emerging from the annular gap, made at a significant angle to the central axis of the mouthpiece. At the same time, the gas flame itself is crimped, which leads to an increase in the temperature of the flame. Thus, an increase in the length of the hot zone of the gas flame is achieved, therefore, the duration of the contact of the particles of the sprayed material with the hot zone of the gas flame also increases. This is also facilitated by a certain inhibition of the movement of particles in this zone due to the powerful compressing effect. The result is a significant improvement in the heat transfer conditions of the particles of the sprayed material with a gas flame, which improves the quality of the resulting coatings, and due to the production of a concentrated gas-powder jet, a significant reduction in losses of the sprayed material is achieved, especially when spraying on small-sized bodies.

 The execution in the air nozzle of a bell with a sufficiently small diameter at its inlet causes a marked increase in the velocity of the gas-powder flow at the exit of the nozzle. The latter also leads to an increase in the quality of sprayed coatings for two reasons. Firstly, the cooling effect of the air flow is reduced, since the time of contact of the particles with the cold zone of the gas flame is reduced. Secondly, a noticeable increase in the particle velocity leads to an increase in the kinetic energy of the flow and, as a result, the energy of impact of particles on the treated surface increases and the adhesion strength of the coating to the substrate increases.

The implementation of gas nozzles in the cavity of the end face of the mouthpiece at an angle of 6-24 ^about to the central axis of the mouthpiece, together with the angle of inclination of the annular gap within 30-75 ^about to the axis of the mouthpiece, provides the most highly concentrated gas powder jet and reduces the speed of particles of the sprayed material in the hottest part of the gas flame and lengthens the hot flame zone. The execution in the end part of the mouthpiece of the cavity with a diameter of 0.5-1.5 of the input diameter of the bell of the air nozzle increases the speed of advancement in the cold zone of the gas flame and increases the kinetic energy of the impact of particles on the sprayed surface. The execution at the exit of the air nozzle of the bell with a length of 0.07-0.5 of the diameter of the bell at the inlet contributes to an additional increase in the particle velocity in the coldest part of the gas flame.

 Figure 1 shows a burner, in section; figure 2 is the same, with additional nozzles and washers.

The design of the flame spraying burner (Fig. 1) includes a housing 1 with channels 2, 3 and 4 for supplying oxygen, combustible gas and air, respectively, a cap 5, an air nozzle 6 with a socket 7 of length l and a diameter D _at the inlet, a mouthpiece 8 s gas nozzles 9, a central channel 10 for supplying the sprayed material and an end part 11 of diameter d. The air nozzle 6 forms with the mouthpiece 8 an annular gap 12 made at an angle γ to the axis of the channel 10.

 Gas nozzles 9 are made in the mouthpiece 8 at an angle α to the axis of the central channel 10.

In the end part of the mouthpiece 8, a cavity 13 is made with a diameter of D _p . At the entrance to the mouthpiece 8, a curly washer 14 is installed with mixing chambers 15, nozzles of the injectors 16 and a slot 17 for suction of combustible gas.

 To fix the mouthpiece 8 in the housing 1 there is a nut 18. In the air nozzle 6 there are radial holes 19 for the passage of compressed air. In the housing 1 there is a cavity 20 in which a washer or washers can be installed that act as a flame arrester and valve (Fig. 1).

 The burner is equipped with a device 21. When spraying coatings of powder materials, this device is a powder feeder; when spraying coatings of wire, rods, flexible cords, an air or electric motor drive is equipped with a reduction gear.

A positive effect is obtained by the use of a design variant of the gas-flame spraying burner (FIG. 2), in which gas nozzles 9 can be made on a circle D _{1 of} 05, -0.8 diameter D _{p of} cavity 13.

An additional series of gas nozzles 22 located in the mouthpiece 8 concentrically around the central channel 10 can be made in the burner. Nozzles 22 can be made on a circle with a diameter D _{2 of} 0.2-0.5 diameter D _p cavity 13. Nozzles 22 can be made at an angle β to the axis of the Central channel 10 within 1-8 ^about .

 In the air nozzle 6 can be made channels 23 for communication through channels 24 in the cap 5 with the surrounding atmosphere.

 The end part 11 of the mouthpiece 8 together with the cavity 13 can be made detachable relative to the rest of the mouthpiece 8.

 In the cavity 25 of the mouthpiece 8, you can install the washers 26 and 27, performing the role of flame arresters.

 The burner operates as follows.

 In channels 2, 3 and 4, respectively, oxygen, combustible gas and compressed air are supplied. Oxygen from the channel 2 enters the cavity 20, then into the nozzles of the injectors 16. Then, oxygen, bypassing the gap 17, enters the mixing chambers 15. As a result, there is a suction of combustible gas through the gap 17 into the mixing chambers 15, where the formation of a combustible mixture, which then it is supplied to the gas nozzles 9. Combustible gas enters the slot 17 from the channel 3. Upon exiting the gas nozzles 9, the gas mixture is ignited and a flame forms.

 Compressed air from the channel 4 is fed into the cavity of the cap 5, from where it enters the annular gap 12, made at an angle to the axis of the central channel 10. As a result, a powerful compression of the gas flame in the cavity of the air nozzle 6 is achieved.

 From the device 21, the sprayed material enters the central channel 10 in the mouthpiece 8, from where it enters the cavity 13. Here, the formed gas-powder jet is crimped under the influence of the dynamic pressure of the flames from the gas nozzles 9. The jet becomes more compact, and the particle velocity of the sprayed material in the initial zone gas flame i.e. in its hottest part, it decreases, which contributes to the desired increase in the heat content of particles. This is also facilitated by the complete absence in the cavity 13 of the stator of air having an undesirable cooling effect of a gas flame.

 At the outlet of the cavity 13, the gas flame and the gas-powder jet are additionally crimped by a powerful stream of compressed air coming out at a high speed from the annular gap 12. As a result, a highly concentrated gas stream is obtained. Further, this flow enters the inlet of the socket 7 of the air nozzle 6, where the cross section is small enough, which leads to a significant increase in the rate of flow of the gas stream, and therefore the speed of the particles. As a result, the time of contacting the particles with the “cold” part of the gas flame is reduced, therefore, the heat content obtained by the particles is not lost. The high particle velocity leads to an increase in the kinetic energy of particle impact on the sprayed surface. As a result, the adhesion strength of the coating to the substrate increases and the density of the coating increases.

 When using an additional series of gas nozzles 22 (FIG. 2), the thermal power of the gas flame increases, which leads to undesirable overheating of the mouthpiece 8, its end portion 11 and air nozzle 6, although such a powerful flame makes it possible to obtain high-quality coatings from such refractory sprayed materials, like nichrome, mixtures of self-fluxing alloys with tungsten carbides, etc.

 To eliminate overheating, it is necessary to sharply increase the flow of compressed air. To exclude the growth of the cooling effect of a gas flame with compressed air, the latter can be divided into two streams. One stream moves along a normal path, i.e. along the annular gap 13, and the other more powerful, enters the channels 23, after passing through the channels in the end part of the housing 1 (not shown), and then passes through the channels 24 in the cap 5 into the surrounding atmosphere, cooling the mouthpiece 8, the air nozzle 6 and cap 5.

 To protect against possible reverse impacts, washers 26 and 27, which act as flame arrestor valves, can be installed in the cavity 25 of the mouthpiece 8. When the flame passes through the nozzle 9, the resulting stream presses on the plane of the washer 26, the latter pushes the washer 27, which closes the holes of the mixing chambers 15. The flow of the combustible mixture into the mouthpiece 8 is stopped, and the gas flame goes out. In addition, the washer 27 prevents the passage of flame into the holes 15. Thus, the washers 26 and 27 act as valves and flame arresters.

The effect of double crimping a gas-powder jet, and therefore the quality of the sprayed coatings, to a decisive extent depends on the inclination angles of the annular gap 12 and gas nozzles 9 to the central axis (Fig. 1), as well as on the ratio of the diameter D _{in the} socket 7 of the air nozzle 6 and the diameter D _p cavity 13 (figure 1).

 The heat content of the particles of the sprayed material, and therefore the quality of the resulting coatings, depends on the presence of a cavity 13 in the end part of the mouthpiece 8, on the presence of a socket 7 in the air nozzle 6 and on the length l of the socket 7 (Fig. 1), since the parameters of the socket determine the flow rate gas flow from the air nozzle, and therefore the particle velocity.

When the angle of inclination γ to the axis of the Central channel is less than 30 ^{about the} required concentration of the gas stream flowing from the cavity of the mouthpiece is not achieved.

With γ greater than 75 ^on a partial closing of the gas flame in a cavity of the mouthpiece, which leads to disruption of the gas combustion flame stability: there claps and backward strokes.

When the angle of inclination of the gas nozzles α to the axis of the central channel is less than 6 ^° in the cavity of the mouthpiece, a sufficient compression of the gas-powder jet is not provided and powder particles begin to settle on the edges of the mouthpiece cavity. As a result, the cavity becomes clogged, the spraying becomes intermittent and unstable, and the quality of the resulting coating deteriorates.

At an angle α of more than 24 ^° , a strong overheating of the mouthpiece cavity is observed, as a result of which the burner can work in a stable mode only for a short time (usually no more than 15-20 s).

When the diameter of the socket at the inlet D _is less than 0.5 of the diameter of the cavity D _p (Fig. 1), the resistance to the gas-powder flow flowing out of the cavity becomes significant, which leads to a decrease in the productivity of the sprayed material. In addition, there is a strong overheating of the air nozzle due to a large excess of the outlet diameter D _p in front of the inlet D _c .

With a diameter D _of more than 1.5 D _p (Fig. 1), the gas flow rate from the air nozzle is reduced, the time of contact of the particles with the “cold” zone of the gas flame increases, the heat content of the particles decreases and, as a result, the losses of the sprayed material increase coating, and the quality of the coatings deteriorates (increases porosity, decreases adhesion to the substrate, etc.).

When the length of the bell l is less than 0.07 of its diameter D _{, the} effect of compression of the gas-powder stream decreases, its concentration does not reach the required level.

With a length l greater than 0.5 of the diameter D _{, the} resistance to the gas-powder flow increases significantly, the heating of the air nozzle increases, particles stick to the edges of the socket, the stability of the spraying process decreases, and the quality of the sprayed coating deteriorates.

The proposed burner for flame spraying due to the use of successive double crimping of the gas powder stream in the cavity of the mouthpiece with a gas flame in the complete absence of air and then concentrated compressed air at the outlet of the gas powder stream from the cavity of the mouthpiece has the following advantages compared to the known one:
the possibility of obtaining high-quality coatings with less heating of the sprayed surface;
a sharp expansion of the range of brands of sprayed materials due to the ability to control the flame temperature over a wide range;
increasing the utilization rate of the sprayed material due to the reduction of losses during spraying, which is due to the high concentration of the gas-powder stream;
the possibility of using the sprayed material not only in the form of powder, but also in the form of wire, rods, cords, etc.

improving the quality of sprayed coatings (increasing adhesion to the substrate, reducing porosity, etc.);
the possibility of using network natural gas as combustible gas, since the proposed burner allows operation at low pressures of the combustible gas.

Claims (13)

1. A GAS-FLAME SPRAYING BURNER, comprising a housing with channels for supplying combustible gas, an oxidizing agent and air, a mouthpiece with an end face and a central channel for supplying a spray material, around which a series of gas nozzles are concentrically arranged, an air nozzle connected to the air supply channel forming the mouthpiece has an annular gap with an angle of inclination to the axis of the mouthpiece, characterized in that an additional cavity is made in the end face of the mouthpiece, and a socket is made in the air nozzle with a length of 0.07 0.5 of the diameter of the mouth inlet at angles of inclination to the axis of the Central channel of the mouthpiece of the annular gap 30 75 ^o and gas nozzles 6 24 ^o , while the diameter of the socket at the inlet is 0.5 to 1.5 the diameter of the cavity of the mouthpiece.  2. The burner according to claim 1, characterized in that the axis of the gas nozzles are made on a circle whose diameter is 0.5 to 0.8 the diameter of the cavity in the end of the mouthpiece.  3. Burner op PP 1 and 2, characterized in that in the mouthpiece made an additional row of gas nozzles located concentrically around the Central channel.  4. The burner according to claims 1 to 3, characterized in that the additional row of gas nozzles is made on a circle whose diameter is 0.2 0.5 of the diameter of the cavity at the end of the mouthpiece.  5. The burner according to claims 1 to 4, characterized in that the total area of gas nozzles of the additional row is 0.1 to 0.5 of the total area of gas nozzles of the main row.  6. The burner according to claims 1 to 5, characterized in that the gas nozzles of the additional row are made in the form of grooves.  7. The burner according to claims 1 to 5, characterized in that the gas nozzles of the main row are made in the form of grooves. 8. The burner according to claims 1 to 5, characterized in that the gas nozzles of the additional row are made at an angle of 1 6 ^o to the axis of the central channel.  9. The burner according to PP.1 to 8, characterized in that the depth of the cavity in the end of the mouthpiece is 0.4 to 1.2 diameter of the cavity.  10. Burner for flame spraying according to claims 1 to 9, characterized in that the width of the annular gap is 0.05 to 0.4 diameter of the cavity.  11. The burner according to claims 1 to 8, 10, characterized in that an additional channel or channels are made in the air nozzle connecting the annular exit gap with the surrounding atmosphere.  12. The burner according to claims 1 to 8 and 10, characterized in that the end part of the mouthpiece is made detachable relative to the rest of the mouthpiece.  13. The burner according to claims 1 to 8, 10 and 12, characterized in that two washers are installed in the mouthpiece, which serve as valves and flame arresters.

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