Patent Application
20210199284
The present invention concerns a device and a method for generating high amplitude pressure waves, in particular for cleaning boilers.
Such a device for generating high amplitude pressure waves is known from U.S. Pat. No. 5,864,517. This device generates acoustic oscillations which are significantly stronger than those which can be generated by loudspeakers. They can be used in particular for boiler cleaning, as these pressure waves lead to a detachment of attached particles. In the case of U.S. Pat. No. 5,864,517 two different pulsed burns are discussed, i.e. the detonation and the deflagration. Detonative combustion has an extremely fast flame speed of 2,000 to 4,000 m/s, while deflagrative combustion has much slower flame speeds such as less than 200 m/s and the pressure waves are of significantly lower amplitude.
EP 2 319 036 concerns a method and device for generating explosions, in particular high intensity pressure pulses. It consists of a pressure-resistant container with a main explosion chamber as in the above-mentioned US patent with an outlet for the pressure pulses and a piston closing the outlet. The piston is displaced in its position by an auxiliary explosion in an auxiliary explosion chamber in such a way that it releases the outlet opening. This procedure requires precise timing coordination between the triggering of the main explosion and the preceding auxiliary explosion. The device then also has a gas spring chamber that brakes the piston that has been pushed back and, after the gases have been blown out of the main explosion chamber, pushes the said piston back to its initial position.
EP 1 922 568 shows a further method and device for producing explosions. The gas spring mechanism has a relief mechanism which is revealed as a spring mechanism.
The article by Tibor Horst Rile “Cleaning technologies with sonic horns and gas explosions at the waste-fired power plant in Offenbach (Germany), cleaning with sonic horns and gas explosions at the waste-fired power plant Offenbach” in VGB Powertech, Vol. 93, No. 8, 1 Aug. 2013, pages 67-72, ISSN; 1435-3199 also reveals a method and device for generating explosions for cleaning with sonic horns.
Furthermore, the FR 2,938,623 shows an explosion cylinder with a piston that can be moved between an open and a closed position to cyclically generate explosions of gas or air under pressure for cleaning purposes.
Based on this prior art, the invention has inter alia the object of specifying an improved device and method which is easier and safer to ignite.
In addition, one of the objectives of the invention is to provide the device with a longer maintenance interval, since the wear of the moving parts in the pressure-resistant container by the explosions is considerable and, in the state of the art, allows only a limited number of repetitions of the cleaning ignitions before the equipment needs to be maintained. Since in power plant engineering, primary industry and technical chemistry, the processes are usually carried out in complex chemical plants, a number of such devices for generating high-amplitude pressure waves are usually provided for cleaning the various vessels, which then have to be maintained accordingly.
The device is preferably used for cleaning boilers in large technical plants, such as waste incineration plants, coal-fired power stations, silos, for removing slag or deposits, etc. There the main advantage is that the individual cleaning cycles can be repeated very quickly and several times. Also, the use of gases as cleaning material to generate the sequence of pressure waves and associated pressure pulses is relatively inexpensive and high pressures can be generated. The addition of two chemical fluids, which do not burn or explode per se, at a time just before the pressure wave is triggered, also increases safety. It also makes it possible to clean while the plant is still warm and possibly still in operation, since the reacting substances are exposed to the hot environment for a long time.
The generated pressure wave can be directed via a tube over longer distances into a boiler to the place to be cleaned. The tube can be fixed to the plant to be cleaned, but can also be inserted from the outside, e.g. telescopically sliding into a plant or boiler. The pressure pulse generated during the burn-up blows off deposits and dirt from inner tubes in the boiler and its walls and at the same time sets the tubes or walls vibrating. Both actions cause an efficient cleaning of the equipment to be cleaned.
Various other uses are conceivable where a high, rapid force pulse, pressure pulse or pressure wave of high intensity and/or (rapid) repeatability is required. Examples are pressure generators for sheet metal forming or as a drive for firearms, where the pressure pulse is used to accelerate a projectile. It is also possible to use such systems in the field of controlled avalanche triggering.
A device for generating high amplitude pressure waves, especially for cleaning boilers, has a pressure-resistant container. This can be made up of several parts. It has at least one burn-up chamber placed inside it. Several burn-up chambers can be connected to each other. At least one ignition device reaching into the combustion chamber(s) is provided. There shall be at least one supply line for supplying a flowable combustible material to the combustor, preferably separately a fuel and an oxidant, for example natural gas and air or methane and oxygen. Various other liquid or gaseous fuels may also be used. In this case, the pressure-resistant container shall have a discharge opening for the directional release of gas pressure generated by the ignition of the combustible material in the combustion chamber. Before and during ignition, a closure means is provided which closes the discharge opening, is designed to open the discharge opening for directional discharge, and which can then be moved by a spring device into the initial position after burning down. The closing means is a piston which is displaceable in its longitudinal direction and which has a rear section aligned in the direction of the spring device and a front section aligned in the direction of the discharge opening.
With respect to its longitudinal direction, the seat of the piston has a piston surface inclined obliquely to the discharge opening, which is arranged opposite a housing surface also inclined obliquely to the discharge opening, whereby the housing surface opens opposite the piston surface at an angle directed towards the discharge opening from a closure line oriented perpendicularly to the piston direction.
The angle can be between 0.5 and 5 degrees, preferably between 1 and 3 degrees, especially 2 degrees.
The closure line oriented perpendicular to the piston direction can be located within the piston wall of the lower section so that a rounded static pressure opening area exists between the closure line and the piston wall.
A flange surface perpendicular to the piston axis, which is connected to or belongs to the combustion chamber, may have an area size between 50 and 200 percent of an area size given by the area size of the piston surface.
A transition area may be provided between these two sections. The front section is located in the area of the combustion chamber when the piston closes the discharge opening. In relation to the longitudinal direction of the piston, the front section is tapered in relation to the rear section, so that the transition area forms an effective surface oriented transversely to the longitudinal direction of the piston, on which a pressure is exerted that drives the piston back when the combustible material ignites, so that the front section of the piston opens the discharge opening. This makes cleaning easier, as the pressure build-up can also be achieved by burning off and is then itself responsible for opening the path to the discharge funnel.
The transition area can be an area that tapers continuously in the longitudinal direction of the piston of the gas spring from a larger piston diameter to a smaller piston diameter, which is located in the area of the combustion chambers. On the other hand, the transition area can also be formed by a flange-like taper of the piston.
In particular, a hollow central guide string may be provided in the pressure-resistant vessel, which in its interior guides the piston in the front area. This has advantages in terms of wear and tear of the piston guide, as it allows guidance over sections of the piston which are further apart. In this case, at least one connecting gap is provided between the combustion chambers and an auxiliary pressure chamber in the area of the flange-like taper of the piston.
The combustion chamber can be arranged in a ring around the piston around its longitudinal axis. In particular, the annular walls of the combustion chamber can then be stacked ring segments connected in a sealing manner, which are advantageously closed off by a top plate and a bottom plate at the top and bottom respectively. Thus, the height and volume of the cylindrical combustion chamber is easily scalable, since no special chambers of different sizes have to be provided. The only part of such a scaled combustion chamber is the correspondingly length-adjusted piston as a sealing unit.
At least two combustion chambers can be arranged in one plane at an angular distance from each other radially to a central axis. In particular, two combustion chambers can be arranged diametrically opposite each other. Then either the longitudinal axis of the gas spring coincides with the central axis; three burn-up chambers could then have an angular distance of 120 degrees in the common plane. Or the longitudinal axis of the gas spring also lies in the same plane as the at least two combustion chambers, so that with three combustion chambers an angular distance of 90 degrees between the individual elements is possible.
The exhaust port usually has a tube with a longitudinal direction of the tube. In this case, either the longitudinal direction of the tube can coincide with the central axis, i.e. the discharge opening is in the extension of the piston, or the longitudinal axis of the gas spring is in the same plane as the at least two combustion chambers. In this case, it is also possible, for example in the case of two combustion chambers, to provide an angular distance of less than 120 degrees between the two combustion chambers, so that they are more aligned with the outlet opening.
The gas spring can have a front gas spring chamber space opposite the piston and a rear gas spring chamber space separated from the piston by a partition, whereby between the front gas spring chamber space and the rear gas spring chamber space there is a first connection as a backflow connection and a second connection with a non-return valve, whereby the non-return valve is arranged in such a way that it allows an unhindered flow of medium from the front gas spring chamber into the rear gas spring chamber, but essentially blocks the opposite direction out of the rear gas spring chamber.
The first and second connections may be provided in the partition. On the other hand, the second connection can have at least two partial connections which, on the one hand, open laterally in the longitudinal direction of the piston movement one above the other in the wall of the gas spring in the front gas spring chamber space and, on the other hand, end in the rear gas spring chamber space, so that the openings are covered one after the other in time when the piston enters the front gas spring chamber space, each of the said partial connections having its own non-return valve. As a result, the individual non-return valves are successively switched off, so that the flow of medium from the front to the rear gas spring chamber slows down, i.e. the braking effect is reduced by the gas pressure build-up in the front gas spring chamber.
The second connection can have a controllable non-return valve, which can optionally have a control valve connected in series and a non-return valve, which controllable non-return valve is connected to a control unit with which the ignition can be triggered, the control unit being designed to open the controllable non-return valve at a first predetermined time interval after the ignition of the flowable, combustible material. This is to ensure that the burn-off in the combustion chamber is complete before allowing the piston to move back further.
The first connection may include a controllable backflow valve which may optionally include a control valve connected in series and a backflow guide, which controllable backflow valve is connected to the control unit with which the ignition is triggered, the control unit being arranged to open the controllable backflow valve at a second predetermined time interval after the opening of the controllable backflow valve. This makes it possible to activate the backflow delayed after the opening of the controllable non-return valve and thus the pressure equalisation between the front and rear gas spring pressure chamber, i.e. to trigger the closing movement of the piston later so that the combustion gases still under pressure leave the combustion chamber completely.
Two gas spring gas connections can also be provided separately for the front and rear gas spring chamber, whereby the control unit has a gas filling control unit with which the gas filling pressure in the front and in the rear gas spring chamber can be set to a predetermined value each before ignition, whereby the gas filling pressure in the front gas spring chamber can be set higher than in the rear gas spring chamber. In particular, the gas filling pressure in the front gas spring chamber can be set to be at least twice, preferably at least three times or five times higher than in the rear gas spring chamber, so that on the one hand the front gas spring pressure chamber does not recede or only slightly recedes on ignition, since the pressure prevailing in it on ignition opposes the pressure building up in the combustion chamber, and the receding only occurs completely and quickly when the non-return valve is opened, since a gas pressure difference has already been set. Especially in the rear chamber atmospheric pressure can prevail, while only the front gas spring pressure chamber has been pressurised with the inert gas.
In order to solve the problem of specifying an improved device and method which is easier and safer to ignite, a device for generating high amplitude pressure waves, in particular for cleaning boilers, comprising a pressure-resistant container with a combustion chamber inserted therein and at least one ignition device extending into the combustion chamber, with at least one supply line for supplying a flowable combustible material to the combustion chamber, the pressure-resistant container having a discharge opening for the directional discharge of gas pressure generated by the ignition of the combustible material in the combustion chamber and a closure means which closes the discharge opening, which is designed to release the discharge opening for the directional discharge and which can be displaced into the initial position by a spring device, characterised in that the closure means is a piston which is displaceable in its longitudinal direction and has a rear section aligned in the direction of the spring device and a front section aligned in the direction of the discharge opening, in that the front section is arranged in the region of the combustion chamber when the piston is in a position closing the discharge opening, in that, in relation to the longitudinal direction of the piston, the seat of the piston has a piston surface which is inclined obliquely to the discharge opening, opposite which is arranged a housing surface which is likewise inclined obliquely to the discharge opening, the housing surface opening opposite the piston surface at an angle, which is oriented towards the discharge opening, from a closure line which is oriented perpendicularly to the piston direction. This angle is advantageously between 0.5 and 3, especially 1 degree. The closure line oriented perpendicular to the piston direction is advantageously located within the piston wall of the lower section, so that a rounded static pressure opening surface exists between the closure line and the piston wall. This device also has the feature that the front section is tapered in relation to the longitudinal direction of the piston compared to the rear section. The taper concerns the inner piston seat wall and then preferably has an opposite outer housing valve seat wall, which opens inwards towards the outlet at a small angle.
Further embodiments are given in the dependent requirements.
Preferred embodiments of the invention are described below on the basis of the drawings, which are for explanatory purposes only and should not be interpreted restrictively. The drawings show:
The function of the device for generating pressure waves is now described in conjunction with the schematic diagram of the device shown in
In the central body 30 there is a piston 70, which will be shown in more detail in the following drawings, which separates the chambers 121 and 122 in front of each other when closed and closes the outlet with its front end 72 of the piston 70 towards the discharge funnel 61. The piston 70 projects with its upper part 71 into the gas spring pressure body 40 as shown in more detail in
The purpose of the device for generating high amplitude pressure waves is to generate them in the first and second pressure chambers 121 and 122 by burning off a fluid fuel or explosive. This fuel is preferably formed by the mixing of components which are not flammable or explosive per se and which are stored in the first and second gas storage vessels 51 and 52. These gas reservoirs 51 and 52 are fed via external gas supply lines 53 and 54 from corresponding gas connections 57 and 58 which are controlled by external gas supply valves 55 and 56. The first gas storage vessel 51 is connected to the combustion chambers 121 and 122 via a first gas filling line 151 and an intermediate first gas filling valve 153. The illustration in
Furthermore, a gas spring gas connection 47 is provided, whereby the gas for the gas spring 40 is fed into the gas spring interior 41 or 42, as shown in
In this embodiment we are talking about a first and a second gas. The first gas can, for example, be methane or natural gas, whereas the second gas can be oxygen or air or an oxygen-containing air mixture. In other embodiments, the flowable combustible material may be an explosive mixture, it may be gaseous, liquid, powder or a mixture of such materials.
The combustion chambers 121 and 122 are additionally connected to an ignition device which simultaneously triggers an ignition of the combustible material in the combustion chambers 121 and 122. If, as in the design of
When the ignition is triggered, a controlled burning or a controlled explosion of the combustible or explosive mixed components takes place in the combustion chambers 121 and 122, which exert a pressure on the piston 70 and there especially on the intermediate area 75, as it will be described in connection with
Prior to this, the outlet opening of the pressure-resistant container is kept closed by piston 70 as a closing means. The gas spring allows the closure to be kept closed even against the filling pressure of the combustible elements in the combustion chambers 121 and 122. Only when the pressure is increased during ignition of the flowable mixture is the pressure on the intermediate area 75 increased in such a way that piston 70 is pushed back accordingly. Subsequently, as will be described in connection with
The piston 70 is opened so quickly that the pressurised mixture in the combustion chambers 121 and 122 is still not completely burnt off when it escapes, so that the gas mixture in the discharge funnel continues to burn off, generating a pressure pulse with a high pressure peak.
When air is used as one of the two media besides CH4 or natural gas, the chemical reaction takes place inside the combustion chambers 121 and 122 and all the energy is converted in the device. The gas is then released into the atmosphere by a subsequent, i.e. time-delayed rapid opening of piston 70 after the initial pressure build-up.
The first and second pressure-resistant containers 21 and 22 are adjacent to the discharge funnel 61 inserted in them, which has a rounded valve seat contact 65 at its inner end. This valve seat contact 65, which is designed as a horizontal, essentially circular contact line running perpendicularly and concentrically to the piston longitudinal axis 90, is adjoined by the front end 72 of the piston 70, which is followed by the tapered piston area 73. Adjoining this tapered piston area 73 is a piston transition area 75, where the diameter of the piston is increased in order to have a larger diameter at the rear end of the piston 71. The rear piston diameter 171 is thus larger than the front piston diameter 172. In particular, the piston 70 has an area 91 (as shown in
The piston 70, which is thus passed through the central body 30 with the pressure-resistant containers 21 and 22, then projects sealingly against the front gas spring chamber space 41 in the gas spring pressure body 40, which is separated from the rear gas spring chamber space 42 by a gas spring partition wall 43. A non-return valve 44 and a gas backflow opening 45 are provided in the gas spring partition wall.
The function of the gas spring is as follows. The two components of the combustible gas mixtures are fed through the gas filling lines 151 and 152 into chambers 121 and 122. These gases are ignited by an ignition device not shown in the drawing in
The drain opening 61 is shown here in all three drawings
It is also possible to have two, three, four or more combustion chambers arranged in the plane of the combustion chambers 121 and 122 of
It can be seen that from the longitudinal axis 90 of the piston there is a first diameter 121, which is smaller than the rear piston diameter 171. Thus the transition area 75 forms two rectangular strips 91 in a section in the projection of the longitudinal axis 90, which serve as pressure transmission strips. When filling the combustion chambers 121 and 122, the pressure exerted on these strips 91 is not sufficient to push the piston 70 back against the gas spring pressure. This changes abruptly after ignition of the gas mixture, as a pressure difference of up to 25 to 30 times the filling pressure can occur, which is then sufficient to push back piston 70 with an appropriately adjusted gas spring tension. In the exemplary embodiments, the burnable chambers have a volume of between one and two litres, whereby the gas filling pressure can be between 10 and 30 bar, for example between 15 and 25 bar. The diameter of the annular opening closed by the piston is between 40 and 15 mm, in particular between 60 and 100 mm, and 80 mm in particular.
Ignition can be designed in a similar way to the prior art document WO 2010/025574 and can therefore be electrical or by light ignition, for example.
The rear area of the piston 70 has sufficient height from the transition area 75 to its upper flat end face which defines the lower gas spring chamber space 41, so that even if the piston is pushed back into this front gas spring chamber space 41, the piston 70 will still be in substantial sealing contact with the inner walls of the gas spring 40 by means of the following sealing elements. According to the embodiment in
Such an annular gap 123 can also be guided on one side, i.e. only on the side of the spark plug 59 and it can also be used in other embodiments with two or more other combustion chambers.
The gas spring 40 is formed in the same way as the other embodiments. There are two major structural differences compared to these other embodiments, which have been used together here. However, in other embodiments not shown in the figures, it is also possible to combine only one of the two differences described in the following examples with the other embodiments.
The first difference to the other embodiments is that there is an annular combustion chamber 125 which completely surrounds the piston 70. Thus there are ring-shaped elements of a pressure-resistant vessel 25, in this case three rings, which have been drawn as one ring due to the smooth flush outer surfaces in
The second difference between the other designs and the embodiments in
Thus, shortly after ignition, the internal pressure of the annular combustion chamber 125 acts on the underside of the rear end 71 of the piston 70 with its surface protruding over the core 191 in the auxiliary pressure chamber 95. Thus the pressure exerted on this surface 191, which corresponds to the pressure on the projection of the pressure surface 91 from the other embodiment, moves the piston 70 in its strand 96 backwards through the increasing auxiliary pressure chamber 95 into the front gas spring chamber 41, whereby here too a bronze seal 81 and an O-ring 82 are provided between the rear end of the piston 71 and the inner wall of the gas spring 40.
When the piston 70 moves backwards, the connection between the annular combustion chamber 125 and the exhaust funnel 61, which is not shown here, opens. The latter is characterised by the distance below the strand 96 and the valve seat 65. Also in this case the pressure of the burning or detonation of the media existing in the annular combustion chamber 125 acts on the receding piston 70.
It is a piston 70 according to the embodiment in
The piston 70 itself can be hollow to save weight, being open to the front in the longitudinal direction 90, or it can also be made of a solid material, especially steel, or it can be hollow and have a plug inserted from the front, especially screwed in. This can also form the sealing surface to the valve seat 65.
Finally,
All of the embodiments shown above in connection with
A line 301 is drawn on the valve seat 300, indicating a distance from the side wall of the piston diameter 172. This is a distance that belongs to a bend R2, which belongs from the side wall 172 to the inner piston seat wall 302, which can be seen better in the detailed views of
The apex of the opening angle 304 is located at the intersection of the line 301, which indicates the end of the curvature of the piston 70, with the opposite outer casing side wall 303 and closes there in a circular ring the outer exhaust funnel chamber 306 from the (here shown) first combustion chamber 121, but of course also opposite the second combustion chamber 122.
This design of the valve seat 300 is shown in the chronological sequence of the explosion-like opening of the piston travel in
The optional pre-chamber surface 311 is the flange extension in the auxiliary chamber pressure chamber 95. The static auxiliary surface 312 is the curved surface resulting from the distance 301 and the corresponding radius R2 at the front end of the piston in
This force builds up until piston 70 lifts off the seat at time 520. Then the dynamic surface 313 comes into play and results in a boost, which is marked by line 413, and the effect is marked as an increase in force by the surface 513 located between line 412 and 413. A little later and with a slight delay, the counteraction of gas spring 40 comes into play, whose force effect is marked as line 415.
The increase in force known as boost ends at a point in time when the boost curve 413 is reversed at a slightly later point in time 521, when the diverging gap as shown in
With the line 414 and the corresponding force effect in the area 415, the emptying of the piston chambers is added in the downturn area, whereby the characteristic line 419 then forms a cumulative line and swings out in opposition to the gas spring line. In summary, the geometry of the valve seat has a positive effect on the opening behaviour of the piston.
During opening, the narrowest cross section shifts radially from the outside to the inside, so that the advantages are small projected areas in the closed state, which prevents unintentional opening. In the embodiment shown, the prechamber 95 ensures the initial opening at the desired time. However, it is possible to replace this auxiliary chamber by arranging the surfaces 191 in the main chamber 121 (i.e. without separate ignition, similar to the embodiment in
Because the narrowest cross-section shifts radially from the outside to the inside, the enlargement of the active area directly after the initial opening leads to a boost effect of the piston movement, which are shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 18165013.6 | Mar 2018 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/057752 | 3/27/2019 | WO | 00 |
