RU2644422C1 - Method for ultra-fine spraying of liquid fuel and device therefor - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to methods for spraying liquids, as well as emulsions (for example, water-fuel emulsions) and suspensions (for example, water-coal suspensions), etc., in various power and process plants. Disclosed is a method for ultra-fine spraying of liquids and liquid-based media, which includes feeding a liquid or liquid-based medium to fragmentation region in which the fed liquid or liquid-based medium is periodically subjected to a strong shock wave with the formation of a cone with an ultra-fine spray. Device for carrying out the method for ultra-fine liquid spraying is disclosed. Device includes a nozzle for supplying a liquid or liquid-based medium, a pulsed shock wave generator with a section of shock-wave fragmentation, wherein the nozzle for supplying the liquid or liquid-based medium is installed in the shock wave fragmentation section of the pulsed shock wave generator.

EFFECT: invention provides ultra-fine spraying of a liquid or liquid-based medium, with a fragment size of 10–15 mcm in a spray cone.

3 cl, 3 dwg

Description

Technical field

The invention relates to methods for sawing liquids, as well as emulsions (e.g., water-fuel emulsions) and suspensions (e.g., water-coal suspensions), etc. in various power and technological installations.

In modern power and technological installations, a heterogeneous mode of fuel combustion is preferred, since in comparison with homogeneous combustion, the latter has several advantages:

- safety, since the combustible mixture is prepared directly in the combustion chamber (reactor);

- the possibility of using several fuels with direct supply to the combustion chamber (reactor);

- the ability to reduce the average combustion temperature due to depletion of the composition of the mixture, etc.

The disadvantages of burning fuel in a heterogeneous mode include a longer process time compared to homogeneous combustion. This is because the preparation of the combustible mixture occurs directly in the combustion chamber (reactor). To reduce the duration of combustion, it is necessary to reduce the time required for mixture formation, for example, by reducing the size of the droplets of fuel supplied to the combustion chamber (reactor). So in the work of Basevich V.Ya., Belyaev A.A. and Frolova S.M. Modeling the propagation of two-phase laminar and turbulent flames / Chemical Physics, 2000, v. 9, No. 10, p. 89-97 it is shown that for drops with a diameter of about 10 microns, the difference between homogeneous and heterogeneous combustion is negligible. Therefore, the development of methods and devices that provide ultra-thin atomization of fuel is an urgent task, especially when it comes to methods and devices applicable to liquid fuels of various kinds - liquids, emulsions and suspensions.

One of the most effective methods of spraying liquids and media based on them is aerodynamic crushing of a jet using a strong shock wave. As a result of exposure to a jet by a strong shock wave propagating with high supersonic speed, the characteristic values of the Weber number reach very high values and there is a rapid catastrophic destruction of droplets and jets with the formation of crushing fragments of ultra-small size (at the level of 10-15 microns (“ultra-thin spray”) regardless of the viscosity and surface tension of the material of the droplet [Nigmatulin RI Dynamics of multiphase media, part- I. M: Nauka. Gl. ed. Phys.-Math. lit., 1987-467 p.].

State of the art

A known method of atomizing fuel and a device for its implementation, proposed in patent RU 2569797 C2, B05B 7/04 (2006.01); F02M 29/00 (2006.01); F02M 61/18 (2006.01); F02M 67/02 (2006.01), published on 05/20/2010. The device comprises a housing having a fuel supply channel and at least one main opening configured to fragment the fuel — to disperse the fuel flow into many drops of fuel. A plurality of fuel droplets come into contact with the collision surface to break the plurality of fuel droplets into a plurality of smaller secondary droplets and create a thin film of secondary droplets on the collision surface. At least one channel for compressed air supplies the air stream in contact with the secondary droplets to break a thin film of secondary droplets of fuel at the peripheral edge of the collision surface to reduce the size of the secondary droplets. Secondary droplets pass through a plurality of secondary outlet openings, leaving the housing. The size of the plurality of secondary drops decreases upon exiting the plurality of secondary holes. The technical result consists in improving the quality of atomization and evaporation of liquid fuel. The main disadvantage of this method is that when using suspension fuels with solid particles (e.g., water-coal suspensions), the rapid interaction of droplets of such fuel with the impact surface will lead to its rapid erosion wear, i.e., the durability of the device when using suspension fuel will be significantly lower.

A known method of spraying liquid hydrocarbon fuel and a nozzle for its implementation, proposed in patent RU 2348823 C2, F02K 7/22, published 12.04.2007. A method of spraying liquid hydrocarbon fuel in a stream of air compressed in a gas turbine or gas turbine compressor passing through a nozzle that receives a low-pressure fuel stream at the inlet, characterized in that the incoming fuel stream is divided into streams. The streams are evenly spaced around the circumference, giving them an additional tangential direction of movement. The trickles are poured into the fuel film on a short solid surface, covering all the trickles from the outside, and form, due to rotation, a free, bell-shaped fuel film not in contact with the solid surface. An axial air stream is blown into the cavity of the bell-shaped fuel film, equalizing the pressure on both sides of the film and enabling the rotating bell-shaped fuel film to expand without breaking as it moves to the fragmentation region — the nozzle exit nozzle. The fuel film thinned as a result of expansion in the fragmentation region is introduced into the peripheral high-speed air stream, previously swirling in the direction of rotation of the film, which sprays the film to obtain a finely dispersed spray jet with droplets of fuel uniformly distributed around the circumference. The atomizing nozzle contains a multi-start fuel auger located in the fuel channel and dividing the incoming fuel stream into separate trickles uniformly spaced around the circumference and giving them additional tangential speed. The nozzle also contains axial air flow channels and a peripheral high-speed air flow channel. The plane of the outlet end of the axial air flow channel together with the screw is displaced inside the fuel needle with the formation of a short, solid fuel jet, which merges the fuel jet into a rotating fuel film, which, after swelling from a solid surface, rotates into a bell-shaped shape. The device allows you to get fine stable spray air torch with fuel droplets evenly distributed around the circumference. The main disadvantage of this method is the presence of a solid surface (screw) that interacts with the fuel flow, which leads to its accelerated erosion wear (especially when using suspension fuel) and, as a result, to a decrease in the durability of the device.

A device for the acoustic atomization of liquid fuel is proposed in patent RU 2357150 C1, F23D 11/34, published on 05.27.2009. The device is designed for atomization of liquid fuel and can be used in chemical reactors, industrial furnaces and other units that require high quality atomization of fuel. The acoustic spray consists of a hollow cylindrical body, a conical diffuser, movably mounted on one of its ends, an internal coaxially located pipe body supplying sprayed fuel, with a tip that acts as a spray, the outer surface of the tip is made in the form of a truncated cone, the conicity of which coincides with the taper diffuser, while the tip is rigidly attached to the end of the pipe, for example, by means of a threaded connection, and consists of two separate parts, fastened interconnected by a bolt fastener in such a way that between its parts there is a gap “a” formed by two coaxial conical surfaces of these separate parts, and the direction of the conical surfaces forming the gap “a” is opposite to the conical surface of the truncated cone forming its outer surface moreover, on a smaller base of the truncated cone of the tip, a cylindrical groove is made, which forms an annular resonating cavity A with the outer surface of the pipe — the first region is a fragment a cation interacting with the nozzle gap formed by two cylindrical surfaces: the inner surface of the casing and the outer surface of the pipe, and at the end of the casing facing the tip, there is a secondary resonating cavity B — the second fragmentation region formed at the casing end and made in the form in the form open toroidal surface. The technical result is an increase in operating efficiency by preventing clogging of the nozzle gap and improving the quality of the spray of highly viscous liquids. The main disadvantage of such a device is that the parameters of the resonant cavity A depend on the type of fuel being sprayed and, therefore, when changing the type of fuel, it is necessary to change the design of the nozzle, which does not allow working on several types of fuel without stopping and changing the equipment.

A device for atomizing water-carbon fuel is proposed in the patent RU 2492390 C2, F23D 11/16 (2006/01), published on 10/06/2011. The invention relates to a power system and is intended for spraying with superheated steam or compressed air and burning water-coal fuels in boiler furnaces. The nozzle for spraying water-coal fuel includes a hollow cylindrical body with a nozzle device — a fragmentation region — and a fuel swirl and emitter installed inside the body with an annular gap, which are hollow bodies of revolution with flat ends. The fuel swirl at the end facing the nozzle device has an annular protrusion along the inner diameter, and the radiator at the end facing the nozzle device also has an annular protrusion along the inner diameter, and the frontal part of the nozzle device is made in the form of a truncated cone. The invention provides a high degree of fuel preparation in the internal cavity of the nozzle by increasing the residence time of the fuel in the area of its interaction with the atomizer, intensive crushing of fuel droplets by supersonic atomizer jets flowing from the channels. The main disadvantage of this method is the interaction of supersonic jets with the walls of the calibrated holes of the nozzle device, which leads to their accelerated wear (especially when using suspension fuel) and, as a result, to a decrease in the durability of the device.

Known nozzle for pumping and pneumatic spraying of fuel, proposed in patent RU 2378529 C2, F02M 47/00 (2006.01), F02B 39/00 (2006/01) published April 10, 2007, which allows you to prepare for burning all grades of liquid fuel, light, heavy with the addition of coal dust and liquefied gas and at the same time approach the Bode Roche cycle, which is the most thermodynamically favorable. The proposed nozzle contains a cylindrical body open at the top and bottom, made with a circular protrusion, a pressure flange that is integral with the body, the body cover, the cone valve with a groove in the upper part, the valve seat with a protrusion, a rod with a hole for the entire length of the rod, clamps vertical displacement limiters, hollow with free space inside the nozzle piston, nozzle cylinder, discs spraying with holes, forming a hole labyrinth, disk mounting nut, fittings for compressed air and Fuel stroke electrically driven valves and compressed air regulation and fuel supply, an oval projection on the piston head, the axial compressor, the compressed air receiver tank. The nozzle is driven by electric valves by acting on the piston to open and close the valve and on the fuel to be sprayed with compressed air or high pressure of the fuel itself without compressed air, the valve is connected with a rod to the rod and inserted into the housing from top to bottom until the protrusion on the seat and in the case. Latching stops limiting the amount of vertical displacement when opening and closing the valve enter the valve groove and are screwed into the threaded holes in the valve seat. The size of the tabs protruding into the groove is smaller than the width of the groove on the valve. The piston stroke limiter is inserted into the housing. The lower support part of the housing is installed with the possibility of free running inside the nozzle body and is made of a larger diameter than the other part of the piston stroke limiter, a spring is installed on it, the lower end resting on the lower support part of the piston stroke limiter, and the upper end touching the lower plane of the nozzle piston. The nozzle cylinder is inserted into the housing, rests on the piston stroke limiter and is pressed against the housing cover. The clamping force of the cap acts through the cylinder on the piston stop and on the valve seat. Spraying discs with holes are inserted into the piston space, forming a fragmentation region. One of the disks has the entire area in the holes, the second disk has holes only in the center, and the first one has holes at the edges. A thread is cut in the upper part of the piston, a nut is pressed into this thread, which presses the discs. Two threaded holes are made in the cylinder cover, a fitting for compressed air is screwed into one of them and a fitting for fuel entry is screwed into the other. Threaded holes and holes in the fittings are fuel supply and air supply channels. An electric valve for regulating and supplying fuel is installed on the pipeline for supplying fuel directly near the nozzle for supplying fuel. An electric actuator valve for supplying and regulating compressed air is installed on the air duct.

The principle of the proposed device is based on the interaction of the air flow supplied from the compressor under high pressure (20-30 atm) and the fuel flow in narrow channels, which leads to their accelerated wear (especially when using suspension fuel based on coal dust) and, as consequence, to reduce the durability of the device.

A device for creating aerosol media, proposed in the thesis by Korovina N.V. “The creation of aerosol media using autonomous spray devices, their evolution and propagation in confined spaces”, in which the shock wave atomizer has an explosive chamber in which an explosive charge and a portion of the atomized liquid limited by membranes are located. The outflow of fluid is carried out from the nozzle hole, its width is limited by the reflector and the edges of the housing. The volume of the blast chamber is denoted by V1. In an explosive chamber of volume V1, an explosive is triggered in about a microsecond. In this case, gases are formed - reaction products that are under pressure. In a liquid, under the influence of a pulse, a shock wave arises and propagates from these gases. Gases push the liquid, acting like a piston, through the gap (nozzle) - the area of fragmentation. This ensures complete displacement of the liquid (this is facilitated by a sufficiently large nozzle cross-sectional area).

In the above-described shock wave sprayer, crushing occurs when the sprayed medium exits the nozzle. The disadvantage of this method is a single pulsed spraying of the liquid.

Closest to the proposed invention in technical essence is the method of atomization of fuel, described in the work "Results of studies of atomization of coal-water fuel pneumatic nozzles" // Yu.A. Senchurova, V.I. Murco, V.I. Fedyaev D.A. Dzyuba, E.M. Bubbles / Energy ( prototype method ), and the device for its implementation is the nozzle AMG-VUT-3750-45, manufacturer of the NPP "Implementation", Kazan ( prototype device ).

In the prototype method, the fuel is sprayed due to the gas-dynamic effect of the spraying agent (air, steam, etc.) in the fragmentation area on the fuel stream, almost at the moment of its exit from the fuel supply channel. A significant disadvantage of this method is the need to create a significant speed difference between the acting stream and fuel. In addition, the spraying of fuel in a combustion chamber (reactor) of complex geometry can lead to uncontrolled sedimentation of fuel on the walls of the chamber and, as a result, to an uncontrolled change in the phase and chemical composition of the fuel mixture in the combustion chamber (reactor).

The proposed prototype method is carried out on a prototype device containing a housing and an aeromechanical head. A central fuel supply channel and lateral spray air supply channels are made in the housing. In the aeromechanical head, a central fuel supply channel and side profiled air supply channels are made. In the output section of the central channel, an expanding nozzle, a fragmentation region, is installed. A significant disadvantage of the prototype device is the presence of a significant number of large particles with a diameter of more than 160 μm (at least 47%) in the spray torch, which can lead (especially in the case of suspension fuels) to an increase in the burning time, uncontrolled sedimentation of the fuel on the chamber walls and, as a result, an uncontrolled change in the phase and chemical composition of the fuel mixture in the combustion chamber (reactor) of a complex configuration.

Disclosure of invention

The objective of the invention is the creation of such a method of spraying a liquid or medium based on it (emulsion, suspension, etc.), which will provide a torch with ultra-thin spray.

The objective of the invention is to provide a device for implementing a method of spraying a liquid or medium based on it (emulsion, suspension, etc.), which will provide a torch with ultra-thin spray.

The solution to this problem is achieved by the proposed:

- a method comprising supplying a liquid or a medium based on it to a fragmentation region, in which a supplied liquid or a medium based on it is periodically exposed to a strong shock wave with the formation of a torch with ultra-thin spray;

A liquid or a medium based on it is supplied to the fragmentation region continuously or pulsed in any known manner.

- a device comprising a nozzle for supplying a liquid or medium based on it, which further comprises a pulse shock wave generator with a shock wave fragmentation section, the nozzle for supplying a liquid or medium based on it is installed in the section of shock wave fragmentation of a pulse shock generator.

Brief Description of the Drawings

In FIG. 1 shows a diagram of a device in which the inventive method is implemented (T is a jet of liquid or a medium based on it; shock wave is a shock wave).

In FIG. 2a shows a photograph of a plume of a water-coal slurry flowing out of the outlet nozzle of the prototype device.

In FIG. 2b shows a photograph of a plume of a water-coal slurry flowing from an outlet nozzle of the device of the invention.

An embodiment of the invention

In FIG. 1 shows a diagram of a device in which the inventive method is implemented. The device includes a nozzle for supplying a liquid or medium based on it (1), an oxidizer (2), fuel (3) and ignition (not shown) supply system for a pulsed shock wave generator (4), a shock-wave fragmentation section (5), and a system control (not shown).

The proposed device operates as follows.

The sprayed liquid or medium on its basis continuously or

is cyclically fed by means of a nozzle for supplying a liquid or a medium based on it (1) to a section of shock-wave fragmentation (5). A pulsed shock wave generator (4), operating, for example, on the principle described in patent WO / 2015/099553 A1, Method for grinding and melting snow-ice mass and a device for its implementation Е01Н 5/10 (2006.01), published on 02.07.2015 periodically generates strong shock waves. In the case of a continuous supply of liquid or a medium based on it through the nozzle (1), the length of the shock wave fragmentation section and the frequency of generation of shock waves should be such as to ensure fragmentation of the liquid or medium based on it, supplied through the nozzle during the time between two subsequent shock wave impulses. In the case of a cyclic supply of liquid or a medium based on it through the nozzle (1), the frequency of operation of the pulsed shock generator (4) and the frequency of the nozzle (1) are synchronized, and the length of the shock-wave fragmentation section should ensure fragmentation of the entire portion of the liquid or medium on it basis filed in one cycle. The shock wave enters the shock wave fragmentation section (5), where it acts on a stream of liquid or a medium based on it. As a result of the shock-wave action, aerodynamic fragmentation of a jet of liquid or a medium based on it takes place with the formation of a torch with ultrafine spray in the output section of the shock-wave fragmentation section (5).

We give an example embodiment of the invention on a prototype of the proposed device, equipped with recording equipment.

The device includes a pulsed shock wave generator, a section of shock wave fragmentation and a nozzle for supplying a coal-water suspension, as well as an air and fuel supply system for supplying a pulsed shock wave generator and a control system. A pulsed shock wave generator consists of a combustion chamber with an internal diameter of 80 mm and a length of 170 mm, to which a flame accelerator with an internal diameter of 50 mm and a length of 790 mm and a detonation tube with an internal diameter of 50 mm and a length of 660 mm are connected in series. The combustion chamber contains a mixing device with a check valve, a fuel supply device and two automobile spark plugs, and is connected to an air supply system. At the exit from the detonation tube, a section of shock wave fragmentation is installed, made in the form of a pipe with an inner diameter of 100 mm, bent at an angle of 90 ° with respect to the longitudinal axis of the detonation tube of a pulsed shock generator. In the rotary part of the shock-wave fragmentation section, a nozzle for supplying a water-coal suspension is installed in such a way that the direction of supply of the sprayed water-coal suspension coincides with the axis of the output section of the section of shock-wave fragmentation. Liquefied petroleum gas (propane-butane) was used as fuel for the pulsed shock wave generator, and the air and fuel consumption were chosen so that the composition of the fuel mixture filling the gasdynamic path of the pulsed shock wave generator was close to the stoichiometric composition and the fuel supply time was set so as to ensure incomplete filling of the detonation tube with a stoichiometric fuel mixture.

In FIG. 2a and 2b are photographs of spray torches obtained using the prototype device — the AMG-VUT-3750-45 nozzle (Fig. 2a) and using the proposed device (Fig. 2b) for the case of shock-wave action with a frequency of generation of shock waves 10 Hz In both cases, the flow rate of the water-coal suspension was 1 l / s. In the case of shock-wave fragmentation of a water-carbon suspension, the jet looks like a cloud of water vapor, which indicates a high atomization quality. An analysis of the dispersion of the particle flow of the sprayed suspension by the trace method showed that particles with a diameter of about 10-15 microns (mainly coal particles included in the suspension) constitute up to 95% of the flare. The range of the jet of the sprayed suspension was comparable to the range of the jet during conventional spraying (about 5 m). The torch opening angle increased to ~ 90 ° (instead of 30-60 °).

Thus, the proposed method and device for its implementation, providing ultra-thin spray of a liquid or medium based on it.

Claims (3)

1. A method of ultrafine atomization of a liquid, comprising supplying a liquid or a medium based on it with a nozzle to a fragmentation region, characterized in that the liquid or medium supplied therefrom is periodically exposed to a strong shock wave to form a torch with an ultra-thin atomization. 2. The method according to p. 1, characterized in that the liquid or medium based on it is supplied to the fragmentation region continuously or pulsed in any known manner. 3. A device for implementing a method of ultrafine spraying of liquid, comprising a nozzle for supplying a liquid or medium based on it, characterized in that the device further comprises a pulsed shock wave generator with a section of shock wave fragmentation, wherein the nozzle for supplying a liquid or medium based on it is installed in a section shock wave fragmentation of a pulsed shock wave generator.

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