RU2043789C1 - Supersonic burner for gas flame spray-deposition of coatings - Google Patents

Abstract

FIELD: installation for spray deposition of coatings. SUBSTANCE: nozzle has the form of a circular aerodynamic nozzle with a flat profiled central body whose internal space is in communication with the powder supply line and the region adjoining the external surface of the profiled portion of the central body. The longitudinal axis of each fuel supply channel may lie in a plane tangent to the circle perpendicular to the longitudinal axis of the combustion chamber and form an angle other than he right angle with said axis. The outer end of the nozzle head opposite the inlet portions of the fuel channels may have two circular grooves communicating with said inlet portions. Said grooves are tightly sealed by covers and form two circular collector channels one of which communicates with the fuel supply system while the other one, with the oxidant supply system. The internal space of the central body may communicate with the space adjoining the external surface of the profiled portion of the central body through holes in its side wall, preferably on the supercritical portion of the nozzle and has the form of a longitudinal through channel. The burner may have a pipe branch and a pipe disposed therein and extending beyond the limits of the branch pipe. At one end said branch pipe is tightly secured on the pipe at the side opposite the central body. The injector head has the form of a circular disc fitting around the branch pipe and secured to its middle portion while the central body is a hollow shell enveloping the branch pipe and forming a circular gap therebetween, communicated in a spaced relation through the nonfastened end of the branch pipe. The ends of the shell are secured on one of the protruding ends of the pipe and on the injector head and can be made integral with it. The wall of the combustion chamber and the subsonic portion of the nozzle are preferably made in the form of internal, intermediate and external shells arranged so as to form an inlet slotted duct between the internal and intermediate shells, said duct being connected to the cooling liquid supply system and an outlet slotted duct between the intermediate and external shells, said duct being connected to the cooling liquid outlet system. One end of the shells is secured to the injector head while the other one interconnects the inlet and outlet slotted ducts through the nonfastened end of the intermediate shell, forming a combustion chamber cooling duct. The injector head may be provided with circular collector recesses on the periphery and opposite the branch pipe, said recesses being interconnected by radial channels so that one of the recesses communicates with the coolant supply system and the other one, with the coolant outlet system. As an alternative, the peripheral circular recess may communicate with the inlet slotted duct and the other one, with the circular slot. The fuel supply channels may then be disposed between the radial channels. The injector head may also be made of two parts of which the first one has the form of a disc with a cylindrical channel coaxial with the disc and the second one, the form of a cylindrical bushing with flanges, inserted into the through channel. The internal, intermediate and external shells are secured on the first portion which also accommodates circular collector recesses and radial channels and the branch pipe is secured on the cylindrical bushing. The collector recess communicating with the circular gap is sealed on the cylindrical bushing by circular seals disposed on both sides of the collector recess. The branch pipe can also be made integral with the cylindrical bushing EFFECT: higher acceleration velocity of the powder particles injected into the stream of the combustion products at a minimum energy losses.

Description

 The invention relates to installations for spraying coatings, in particular, to designs of burners for supersonic gas-flame spraying of coatings.

Known burner for flame spray coating, containing a combustion chamber with a cooling path and a nozzle head with fuel supply channels, a nozzle, a powder supply line to the combustion product stream and a coolant supply and discharge system [1]
In this burner, the powder is fed directly into the supersonic stream.

 A disadvantage with low degrees of expansion and low speeds to which powder particles can be dispersed. In addition, such a scheme for transferring the flow of combustion products through the speed of sound is associated with significant energy losses, since with the free expansion of the flow, a system of direct and oblique shock waves is formed in it, the passage through which is associated with loss of total pressure.

Known burners for supersonic gas-flame spraying of coatings containing a combustion chamber with a nozzle head, a powder supply line to the combustion product stream, a fuel supply system and a nozzle [2]
A distinctive feature of this and other similar burners is that the powder is introduced into the subsonic flow of combustion products at the subcritical section of the nozzle. Despite the advantages of such a scheme of the powder into the stream, for example, a high degree of uniformity of the distribution of powder particles over the cross section of the stream, a high degree of heating of the particles due to their sufficiently long residence time in the high temperature stream, the known schemes have disadvantages due to the following. The introduction of powder into the flow part of the nozzle leads to the ingress of particles on the walls of the nozzle, their adhesion and erosion wear of the material of the walls. The latter factor makes it almost impossible to use supersonic nozzle blocks bounded by walls.

 In addition, the adherence of powder particles to the walls leads to periodic separation of the conglomerates from the particles from the walls and their removal to the surface of the workpiece, which affects the quality of the coating. It should also be noted that the flow is accelerated to supersonic speeds when the jet expands freely in the environment due to its rotation around the nozzle exit edge. However, in this mode of expiration, the achieved expansion rates are small, which leads to the fact that one of the main parameters determining the quality of the applied coating, namely, the particle velocity, which is determined by the flow rate, is not slightly higher than its values that occur during subsonic spraying.

 The disadvantage of this scheme is that the supply of powder directly into the subsonic flow makes it practically impossible to use one of the most effective methods to increase the efficiency of the combustion process and increase the flow rate, namely, the process of burning fuel at high pressures, since with increasing pressure in the combustion chamber it is necessary to increase the pressure in the container with the powder to the same extent, which requires the development of a special system for pressurizing the container and changing its design with safety perspectives, but in practice will lead to a sharp complication of the design of the burner.

 The purpose of the invention is to increase the acceleration rate of particles introduced into the flow of combustion products of the powder with minimal energy loss.

 This is achieved by the fact that in a supersonic burner for gas-flame spraying of coatings containing a combustion chamber with a cooling duct and a nozzle head with fuel supply channels, a supersonic nozzle, a powder supply line to the combustion product stream and a coolant supply and discharge system, according to the invention, the nozzle is made in in the form of an annular aerodynamic nozzle with a hollow profiled central body, the inner cavity of which is in communication with the powder supply line and the area adjacent to the outer the surface of the profiled portion of the central body. In this case, the longitudinal axis of each of the fuel supply channels can lie in a plane tangent to a circle perpendicular to the longitudinal axis of the combustion chamber and make an angle different from the straight line with the specified axis.

 At the outer end of the nozzle head opposite the inlet sections of the fuel channels, two annular grooves communicated with the latter can be made, hermetically sealed with covers to form two annular collector channels, one of which is in communication with the fuel supply system and the other with the oxidizer supply system. The inner cavity of the central body can be in communication with the area adjacent to the outer surface of the profiled portion of the central body through holes made in its side wall, most preferably in the supercritical portion of the nozzle, and made in the form of a through longitudinal channel.

 The burner can be equipped with a nozzle and a tube located in it with a gap protruding outside the nozzle, the latter at one of its ends being hermetically fixed to the tube from the side opposite to the central body. The nozzle head is made in the form of an annular disk enclosing the nozzle and fixed in its middle part, the central body in the form of a hollow shell enclosing the nozzle with the formation of an annular gap between it, communicating with a gap through the loose end of the nozzle, the gap is connected to the supply system, and the gap to the system coolant drain. In this case, the shell ends are fixed on one of the protruding ends of the tube and on the nozzle head and can be made integrally with the nozzle head.

 The wall of the combustion chamber and the subsonic portion of the nozzle is preferably made in the form of an inner, intermediate and outer shells, which are formed between the inner and intermediate shells of the inlet slot path connected to the coolant supply system, and between the intermediate and outer shells of the outlet slot path connected to the system coolant drain, while the shells are attached to one of the ends of the nozzle head, the other inner and outer shells are interconnected ermetichno, and the inlet and outlet slot paths are interconnected through the loose end of the intermediate shell to form a combustion chamber cooling path.

 In the nozzle head, annular collector grooves communicated with each other via radial channels can be made around the periphery and opposite the nozzle, while one of the grooves is in communication with the supply system, and the other with the coolant drainage system, or the peripheral collector groove can be communicated with the inlet slot path, and the other with an annular gap.

 The fuel supply channels in this case can be placed between the radial channels. The nozzle head can also be made of two parts, the first of which has the form of a disk with a cylindrical channel, a coaxial disk, and the second in the form of a cylindrical sleeve with flanges inserted into the through channel. In this case, the inner, intermediate and outer shells are fixed on the first part, the annular collector grooves and radial channels are located in it, the nozzle is fixed on the cylindrical sleeve, and the collector groove communicated with the annular gap is sealed relative to the cylindrical sleeve by means of ring seals placed on both side of the collector groove. The pipe may also be made integrally with a cylindrical sleeve.

 Figure 1 presents the burner, a longitudinal section; figure 2 section aa in figure 1; figure 3 diagram of the nozzle head with annular collector channels; in Fig.4 a section bB in Fig.3; 5 is a diagram of a burner with a composite nozzle head; in Fig.6 view along arrow B in Fig.5.

 The supersonic burner for gas-flame spraying of coatings contains a combustion chamber 1 with a cooling tract and an injector head 2 with fuel supply channels 3 and 4, a supersonic nozzle 5, a powder supply line to the combustion product stream, and a coolant supply and discharge system. The nozzle 5 is made in the form of an aerodynamic annular nozzle with a hollow profiled central body, the inner cavity of which is in communication with the powder supply line and an area adjacent to the outer surface of the profiled section of the central body.

 The longitudinal axis of the fuel supply channels lies in a plane tangent to the circle perpendicular to the longitudinal axis of the combustion chamber 1, and makes an angle different from the straight line with the specified axis. On the outer end of the nozzle head 2 opposite the inlet sections of the fuel channels 3 and 4, two annular grooves communicated with the latter are made, hermetically sealed with caps 6 and 7 to form two annular collector channels 8 and 9. One of the annular channels 8 is in communication with the oxidizer supply system, and another 9 with a fuel supply system.

 The inner cavity of the central body can be communicated with the region adjacent to the outer surface of the profiled portion of the central body through the holes 10, and the holes can be located on the supercritical portion of the nozzle 5. The inner cavity of the central body is made in the form of a through longitudinal channel 11 in it. The burner is equipped with a pipe 12 and a pipe 14 located therein with a gap 13, protruding beyond the pipe 12, the latter at one of the ends 15 is hermetically fixed to the pipe 14 from the side opposite to the central body. The nozzle head 2 is made in the form of an annular disk wrapping around the pipe 12 and fixed in its middle part, the central body in the form of a female pipe 12 covering the hollow shell 17 with the formation of an annular gap 18 between them, communicated with a gap 13 through the loose end 19 of the pipe 12. The gap 13 connected to the supply system, and the gap 18 to the coolant drainage system, while the shell 17 ends fixed on one of the protruding ends 20 of the tube 14, and on the nozzle head 2. The shell 17 can be made integrally with the nozzle head 2 nd.

 The wall of the combustion chamber 1 and the subsonic section 21 of the nozzle 5 is made in the form of an inner 22, an intermediate 23, and an outer 24 shell, located between the inner and intermediate shells 22 and 23 of the input slit path 25 connected to the coolant supply system, and between the intermediate and the outer shells 23 and 24 of the outlet slit path 26 connected to the coolant drainage system, while the shells 22-24 are attached to the nozzle head 2 by one of the ends, the inner and outer shells 22 and 24 are connected to the other They are tightly sealed to each other, and the inlet and outlet slit paths 25 and 26 are communicated to each other through an unsecured end 27 of the intermediate shell 23 to form a cooling path for the combustion chamber.

 On the periphery of the nozzle head 2 and opposite the nozzle 12, annular collector grooves 28 and 29 are made, interconnected by means of radial channels 30, while one of the grooves is in communication with the supply system and the other with the coolant drain system. The peripheral collector groove 28 can be communicated with the input slot path 25, and the other 29 with the annular gap 18, and the channels 3 and 4 of the supply and removal of fuel are placed between the radial channels 30.

 The nozzle head 2 can also be made of two parts, the first of which has the form of a disk 31 with a cylindrical through channel 32, a coaxial disk 31, and the second in the form of a cylindrical sleeve 33 with flanges 34 inserted into the through channel 32. In this case, the inner, intermediate and the outer shells 22, 23 and 24 are fixed on the first part 31, the ring collector grooves 28 and 29 and the radial channels 30 are located in it, the pipe 12 is mounted on the cylindrical sleeve 33, and the collector groove 29 communicated with the annular gap 18 is sealed relative to qi of the indian sleeve 33 by means of ring seals 35 and 36 located on both sides of the collector groove 29. In addition, the pipe may be integrally made with a cylindrical sleeve 33, and the flange 34 may have a curly (non-circular) shape, for example cross-shaped (Fig.6) .

 The burner operates as follows. The fuel mixture (or fuel and oxidizer separately) are fed through channels 3 and 4 to the combustion chamber, where they are ignited (for example, by means of a candle) and burned. The inclination of the longitudinal axis of the channels 3 and 4 with respect to the longitudinal axis of the combustion chamber allows the injection fuel mixture to be twisted somewhat, thereby increasing its residence time in the combustion chamber and improving the quality of the course of the evaporation processes (in the case of using liquid fuel) and mixing, and as a result increase completeness of fuel combustion.

 Further, the combustion products are accelerated in the nozzle 5, a powder is supplied to them, which is accelerated, heated and sent to the surface of the product to form coatings. Acceleration of combustion products to supersonic speeds is carried out using an annular aerodynamic nozzle with a central body. The main feature of such nozzles is that, due to the special profiling of the central body, it is possible, in contrast to the expansion of the flow when turning around the nozzle exit edge, to provide almost any degree of expansion, and consequently, the gas flow velocity, while the supersonic flow will be decelerated only after he reaches the calculated speed, and therefore, formation of shock waves will not take place in the main part of the flow, and consequently, energy losses due to acceleration of powder particles will are minimal. These types of nozzles are self-adjusting, i.e. when the pressure in the combustion chamber changes, the nozzle operates in the so-called design mode, i.e. an expiration mode in which the pressure at the nozzle “cut” is equal to the pressure in the environment, and therefore, when the pressure in the combustion chamber changes, no changes to the burner design are required, and in particular, is not required to ensure the flow in the nozzle with minimal losses changes in the nozzle profile (in practice, when using conventional round nozzles, this is simply a replacement for the latter, or, without replacing, increased energy consumption for dispersing particles). The powder may be introduced into the flow of combustion products through the central body when hollow.

 The powder from the powder supply line enters the tube 14, and from it either through the openings 10 or through the channel 11 is introduced directly into the flow of combustion products. When powder is introduced only through the open end of the tube 14, the particles are fed into the zone adjacent to the end of the tube, in which a vacuum is created due to suction by supersonic gas flow. Such a scheme for introducing powder particles into the stream makes it possible to ensure a non-pressure supply of powder into the stream of combustion products, regardless of the pressure at which the fuel is in the combustion chamber, and thereby realize all the advantages mentioned above related to the combustion process at high pressure.

 However, if necessary, in particular when using refractory powders, or to ensure maximum dispersal of the powder particles to increase their residence time in the stream of combustion products, the particles can be introduced into the stream in the subsonic section of nozzle 5, for example, through openings 10. In this case, it is possible to feed powder into the central part of the supersonic flow, which is usually not achievable without destroying or changing the flow structure using any other known methods. This allows you to drastically increase the flow rate of the powder without changing the flow rate of the combustion products, increase the spraying performance and ensure uniform distribution of the powder across the flow cross section.

 The tube 14 is placed inside the nozzle 12 and forms a gap 13 with the latter. The nozzle at the end 15 is sealed on the tube 14. The central body is made in the form of a hollow nozzle 12 of the hollow shell 17 with the formation of an annular gap 18 between them, communicated with the gap 13 through the loose end 19 branch pipe 12. This embodiment allows efficient cooling of both the powder supply tube 14 and the central body (shell 17) by supplying coolant through the gap 13 and slot 18. The combustion chamber is cooled by supplying about lazhdayuschey liquid (e.g., water) in the input and output paths 25 and 26. The combustion chamber design is simple and technological. The wall of the combustion chamber and the subsonic portion of the nozzle 5 is formed by three shells 22, 23 and 24, mounted on the side of one of the ends on the nozzle head 2. An intermediate shell 23 is necessary for organizing the flow of coolant in the cooling path along the entire surface of the side wall of the combustion chamber 1 and subsonic plot nozzle 5 and the exclusion of the formation of stagnant zones in the cooling path. In some cases (and especially at high pressures in the combustion chamber), cooling of the nozzle head 2 is required.

 The cooling path of the nozzle head 2 of the burner is formed by two collector grooves 28 and 29, interconnected by radial channels 30. The cooling fluid enters one of the grooves 29 and is discharged through the groove 28.

 The advantages of such a design, if necessary, to cool all the elements of the burner is the possibility of an organic combination of the cooling paths of each of the main elements of the burner, such as a powder supply system, nozzle head 2 and combustion chamber 1. In this case, the coolant can be fed into the gap 13, from it into the annular gap 18, passing through which it will carry out heat removal from the walls of the combustion chamber. Further, the liquid can be sent to the collector groove 29, channels 30 and to the collector groove 28, and from it to the inlet and outlet slotted paths 25 and 26. To simplify the manufacturing and assembly technology of the burner, the nozzle head can be made removable from two parts, the first of which , having the form of a disk 31, is worn on the second part in the form of a sleeve 33 with a flange 34. The sealing of the cooling path of the head 2 is carried out using ring seals 35 and 36.

 For the convenience of supplying the fuel supply lines and introducing the spark plug, the flange 34 is made crosswise. This makes it possible to supply highways in the area between the flange protrusions.

 The efficiency of the fuel combustion process is largely determined by the quality of the preparatory processes — evaporation and mixing of the fuel components. To improve the distribution of fuel around the circumference of the combustion chamber, it is required to perform as many fuel channels 3 and 4 as possible. However, in this case, a special unit is needed that could ensure the distribution of fuel coming from the fuel line through all channels 3 and 4. As such a unit in the nozzle head 2 at its end opposite the inlet sections of channels 3 and 4, two annular grooves are made, hermetically sealed with caps 6 and 7 with the formation of two annular collector channels 8 and 9. Fuel and oxidizer supplied to the can The channels 8 and 9 are evenly distributed around the circumference of the head 2 and thereby along the fuel channels 3 and 4. In addition, in some cases, a certain simplification of the design is achieved by making the shell 17 integral with either the nozzle head 2 or the cylindrical sleeve 33.

 The proposed burner circuit allows us to solve two main problems when creating devices of this kind, ensuring the introduction of powder directly into the central part of the supersonic stream without destroying the structure of the supersonic stream, and using the advantages of the supersonic stream to disperse powder particles as much as possible. Existing burner circuits do not allow particles to be accelerated to speeds of the order of thousands of meters per second due to very ineffective schemes for converting a subsonic flow into a supersonic flow, with detonation spraying it is impossible to obtain supersonic flow regimes of a gas behind a detonation wave, and when using plasma methods to prevent particles from sticking to walls and erosive wear of the latter.

 The proposed burner allows you to increase the speed of the particles with almost the same (or slightly less than plasma spraying) degree of heating. In this case, due to the adopted nozzle scheme, acceleration of powder particles is carried out with minimal energy losses, since in a wide range of changes in the parameters of the combustion process both in pressure and in flow rate, the nozzle operates in the calculated mode (in the absence of shock waves in the main section of the supersonic jet).

Claims (14)

 1. A supersonic burner for gas-flame spraying of coatings, comprising a combustion chamber with a cooling duct and a nozzle head with fuel supply channels, a supersonic nozzle, a powder supply line to the combustion product stream and a coolant supply and discharge system, wherein the nozzle is made in the form of rings aerodynamic nozzle with a hollow profiled central body, the inner cavity of which is in communication with the powder supply line and with the area adjacent to the outer surface of the profiles nnogo central body portion.  2. The burner according to claim 1, characterized in that the longitudinal axis of the fuel supply channels lies in a plane tangent to a circle perpendicular to the longitudinal axis of the combustion chamber, and makes an angle different from the straight line with the specified axis.  3. The burner according to claim 1 or 2, characterized in that on the outer end of the nozzle head opposite the inlet portions of the fuel supply channels, two annular grooves are connected with the latter, hermetically closed by covers to form two annular collector channels.  4. The burner according to claim 3, characterized in that one of the annular channels is in communication with the fuel supply system, and the other oxidizer.  5. The burner according to claim 1, or 2, or 3, or 4, characterized in that the inner cavity of the central body is in communication with the region adjacent to the outer surface of the profiled portion of the central body through openings made in its side wall.  6. The burner according to claim 1, or 2, or 3, or 4, or 5, characterized in that the inner cavity of the central body is in communication with the atmosphere at the supercritical portion of the nozzle.  7. The burner according to claim 1, or 2, or 3, or 4, or 5, or 6, characterized in that the inner cavity of the central body is made in the form of a through longitudinal channel in it.  8. The burner according to claim 7, characterized in that it is equipped with a nozzle and a tube located therein with a gap protruding outside the nozzle, the latter at one of its ends being hermetically fixed to the tube from the side opposite to the central body, the nozzle head is made in the form of an annular a disk enclosing the nozzle and fixed in its middle part, the central body in the form of a hollow shell enclosing the nozzle with the formation of an annular gap between them, communicating with a gap through the loose end of the nozzle, the gap is connected to the system Me supply, and a gap to the coolant drainage system, while the shell ends are fixed on one of the protruding ends of the tube and on the nozzle head.  9. The burner according to claim 1, or 2, or 3, or 4, or 5, or 6, 7, or 8, characterized in that the wall of the combustion chamber and the subsonic portion of the nozzle is made in the form of an inner, intermediate and outer shells, located with the formation between the inner and intermediate shells of the input slit path connected to the coolant supply system, and between the intermediate and outer shells of the output slit path connected to the coolant drain system, while the shells are attached to one of the ends on the nozzle head, etc. gim inner and outer shells are connected together hermetically and inlet and outlet slot paths are interconnected through the unattached end to form an intermediate shell combustor cooling path.  10. The burner according to claim 1, or 2, or 3, or 4, or 5, or 6, or 7, or 8, or 9, characterized in that on the periphery of the nozzle head and opposite the nozzle are made annular collector grooves communicated between by means of radial channels, while one of the grooves is in communication with the supply system, and the other with the coolant drain system.  11. The burner according to claim 10, characterized in that one of the collector grooves, peripheral, is in communication with the inlet slot path, and the other with an annular gap, wherein the fuel supply and exhaust channels are located between the radial channels.  12. The burner according to claim 11, characterized in that it is made of two parts, the first of which is in the form of a disk with a through cylindrical channel coaxial with the disk, and the second in the form of a cylindrical sleeve with flanges inserted into the through channel, while the inside , the intermediate and outer shells are fixed on the first part, the annular collector grooves and radial channels are located in it, the nozzle is fixed on the cylindrical sleeve, and the collector groove communicated with the annular gap is sealed relative to the cylindrical sleeve redstvom annular seals arranged on both sides of the collecting groove.  13. The burner according to claim 8, characterized in that the shell is made integrally with the nozzle head.  14. The burner according to item 12, characterized in that the pipe is made integrally with a cylindrical sleeve.

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