EP2567375A1

EP2567375A1 - Seal and method for producing a flashover barrier

Info

Publication number: EP2567375A1
Application number: EP11722284A
Authority: EP
Inventors: Hans Ruegg; Peter Ruf
Original assignee: Explo Engineering AG
Current assignee: Explo Engineering AG
Priority date: 2010-05-04
Filing date: 2011-04-28
Publication date: 2013-03-13
Also published as: WO2011137543A1; JP2013534606A; CH703104A2

Abstract

The invention relates to a seal for a pressure wave generator, which seal seals a movable piston (3) with respect to a housing and is in the form of a fluid seal. The seal acts as a flashover barrier between two explosion chambers (6, 11) and consists of a non-explosive, non-ignitable fluid. The invention also relates to a method for producing an ignition barrier, in which a non-explosive, non-ignitable fluid is introduced into a sealing area between a movable piston and a housing wall and thus temporarily seals two areas filled with explosive material with respect to one another.

Description

SEAL AND METHOD FOR MANUFACTURING ONE

DURCHZÜNDSPERRE

The invention relates to a seal for pressure wave generators, in particular a seal for moving parts in explosion chambers, which acts as Durchzündsperre. It also relates to a method of making a flash-through device for such devices.

In pressure wave generators, as described in WO 2007/028264 and in particular in WO 2010/025574, an auxiliary and a main explosion are ignited in chambers separated from one another. The auxiliary explosion serves to release a closure of the main explosion chamber directly or via other locking mechanisms, so that a subsequent main explosion does not act with full force on the closure and affects or destroys it accordingly. Between the auxiliary and main explosion accordingly takes place an explosion delay. Such a delay preferably takes place by means of a delay line, in which an explosion is conducted from an auxiliary chamber into a main chamber or by means of delayed ignition in the two chambers via separate ignition devices present in the chambers.

Concerning construction and execution of the ignition and explosion delay, as well as regarding exemplary designs and functions of a Pressure wave generator, they refer to the two aforementioned documents WO 2007/028264 and WO 2010/025574 at this point.

Specifically in the pressure wave generator of document WO 2010/025574, an auxiliary chamber and a main explosion chamber are sealed against one another via a movable piston. The piston also closes a Ablassöffhung for a pressure wave generated in the main explosion chamber. Immediately before an ignition triggering of an explosion, auxiliary and main explosion chambers of the pressure wave or explosion generator are filled with an explosive gas mixture, typically with overpressure. Between the piston and the housing there is a thin gap, which can not be completely avoided due to a required clearance of the piston. This gap is also filled with the explosive gas mixture. However, it must be prevented that the explosion is passed directly through the gap in the main explosion chamber and there trigger a major explosion premature, so even before the piston was moved sufficiently far by the auxiliary explosion.

In the device described in WO 2010/025574, the piston can be provided with an O-ring seal for this purpose. The O-ring is exposed to very high loads. The gas explosions in the auxiliary and main explosion chambers produce very high pressures of up to 100 Obar and temperatures of up to 4000 ° C. The piston is also moved very fast. The sum of these loads reduces the life of the O-ring seal.

It is an object of the invention to provide a seal which overcomes existing disadvantages of O-ring seals. It is a particular object of the invention to provide a seal for a pressure wave generator, which high withstands mechanical and thermal stresses and at the same time acts as a flameproof device.

The object is achieved by the gasket and the method for producing a strike-through barrier, as described in the independent claims.

The improved seal for a pressure wave generator is designed as a fluid seal. Instead of an O-ring, a non-explosive, non-flammable fluid, such as a non-explosive, non-flammable gas or a non-explosive fluid, is used. Such a fluid may be, for example, nitrogen, oxygen, natural gas, air or water. Preferably, a fluid is used which is already used in the pressure wave generator.

The fluid is guided via a supply line, preferably via a bore in the housing, into the sealing region of a piston and pressed between the piston and the housing. The fluid can be pressurized, which pressure preferably corresponds to that of a flowable, explosive gas mixture in one or both areas, which are separated from each other by the piston.

The piston may be provided in the sealing area with one or more grooves, preferably circumferentially. In the groove (s), the fluid is distributed over as far as possible the entire circumference of the piston. It is also possible to introduce the groove or grooves in the housing in the sealing area. With one or more grooves, a barrier fluid amount can be increased so that a passage of an explosion from one area to the other, even at very high pressures, is reliably prevented. Several grooves also act much like a labyrinth seal in which an explosion pressure over each groove due to the Flow resistance undergoes a pressure drop and the flow thereby also a time delay.

Now, if an explosion in one area, typically in a pressure-resistant chamber, with a suitable ignition device, such as a spark plug or glow plug ignited and delayed triggered in the other area by means of delay line or other ignition device and delay circuit - so the fluid seal acts as long as Durchzündsperre , Typical periods of time for which a fluid must prevent the flash-through are in the range of <1 millisecond to a few milliseconds, typically 0.2-2ms, e.g. 0.5- 0.8ms.

In a preferred operation of a pressure wave generator, two chambers separated from one another by the piston are now filled with a flowable, explosive material. A non-explosive, non-ignitable fluid is introduced through a passage in the chamber wall into the sealing area of the piston, between the piston and the chamber wall. In this case, the two chambers are preferably subjected to an overpressure and the fluid at about the same or a slightly higher pressure, so that the fluid completely displaces the explosive material from the gap. It is possible to fill the fluid _"in portions" or to ensure that there is a constant supply of fluid. With the latter, it can be ensured that the fluid seal is constantly maintained, even with a prevailing overpressure on one or the other side of the sealing area.

The fluid is distributed in the gap between the piston and the housing wall and / or in an existing groove. Now an explosion in a chamber is ignited and delays the explosion in the other chamber. In a repetitive method, the said steps are repeated accordingly.

To create a Durchzündsperre preferably gases are used. These have the advantage of quickly spreading in the sealing area. If inorganic gases such as nitrogen or oxygen are used, they have the additional advantage that they do not cause any irritation in contrast to combustible gases. It is also possible to use a liquid, such as water.

Exemplary embodiments of the invention are shown in schematic figures. It shows

1 shows a pressure wave generator with fluid seal in a circumferential groove.

2 shows a pressure wave generator with fluid seal without groove.

FIG. 1 shows an explosion generator with pressure-resistant container 1 and a discharge opening 2 located in the container. A displaceably arranged in the container piston 3 serves as a valve for closing and keeping closed the drain opening. The rear end 4 of the piston has an enlarged diameter and a seal such that the rear end preferably slides completely close to the inner container wall. The pressure-resistant container has in a rear region a first chamber, which is divided by the rear end of the piston into two sub-chambers. The one compartment chamber is the gas spring chamber 5, the other the auxiliary explosion chamber 6. The gas spring chamber. 5

E RS ATZ BLADE ^" (REG EL 26) is filled with a gas, such as air, nitrogen, C02, etc., which gas is passed through a dedicated Gaseinfüllöffhung 7 in the gas spring chamber 5.

By the gas or closing pressure in the gas spring chamber, the foremost end of the piston 3, the valve, is pressed against the valve seat 8 in the discharge opening. This closing pressure is so high that it is able to guide the piston into a closed position and hold it there, even against a filling pressure in the auxiliary explosion chamber, and thus reliably closes off the discharge opening.

The main explosion chamber 1 1 is connected via a supply line 9 with an explosive mixture, e.g. Oxygen and ethane, filled. The filling of the auxiliary explosion chamber 6 with an explosive mixture takes place via the delay line 22 from the main to the auxiliary explosion chamber, which line also serves as the ignition line. The explosive material for the main and auxiliary explosion is accordingly preferably the same. However, it is also possible with separate feeds into the chambers to use other mixtures or to connect a supply only to the main explosion chamber and to fill the auxiliary explosion chamber accordingly by the delay line 22.

The ignition of an auxiliary explosion in the auxiliary explosion chamber is effected via an ignition device 10, for example a spark plug or glow plug, or by means of a powerful laser beam which is conducted into the device. Due to the high pressure created by the ignition of the explosive mixture in the auxiliary explosion chamber 6, the piston is pushed backwards, against the force of the gas spring and moves. By pushing back the piston, the discharge opening 2 is opened. The main explosion chamber 1 1 is arranged in the front part of the pressure-resistant container. This consists in this embodiment of two laterally, at right angles to the piston arranged and closed on one side tubes.

When filling the two explosion chambers, the substances used for an explosive mixture can be filled in succession up to a stoichiometric ratio as far as possible. In order to achieve a good mixing, it is also possible to pre-fill individual substances in the appropriate ratio into separate pressure vessels with the same pressure and to pass these substances from the pressure vessels into the explosion chambers.

The piston has a groove 12 in a sealing area between the auxiliary and main explosion chamber and a supply line 16 leading to and into the sealing area and passage in the chamber wall. For technical reasons, the groove is preferably shaped as a simple notch. Via the supply line 16, a non-ignitable non-explosive gas is introduced into the groove. A pressure of the gas is equal to or greater than the pressure in the explosion chambers, so that no gas exchange between the chambers and through the sealing area can take place.

In an exemplary embodiment, inflation pressures in the range of 15-50 bar were used. The introduction of the fluid took place during the period between filling and igniting the explosive mixture, preferably immediately before ignition. The fluid was introduced at an overpressure of 1 to 5 bar with respect to the filling pressures in the sealing area. It is also possible to design the fluid seal without a groove, as shown in FIG. In this embodiment, the supply line 16 'also leads into the sealing area. The barrier fluid used is one of the two gas components, for example oxygen, of the explosive mixture used for the explosion. The supply line for the seal can thus be connected to a common gas supply.

The explosion delay between auxiliary and main explosion is also realized here with a delay line 22. Through this delay line 22 or ignition, the explosion of the auxiliary explosion chamber 6 is directed into the main explosion chamber 1 1. The delay time is then determined by the length of the conduit as well as the rate of explosion, and no separate detonator is required in the main explosion chamber. In the example shown, the main explosion chamber has a supply line 9 and the auxiliary explosion chamber 6 is filled via the delay line. With this filling method, the auxiliary and main explosion chambers are subjected to the same filling pressures.

The temporal offset of the two explosions in a preferred embodiment is in the range of a few milliseconds, preferably 0.2-10 milliseconds, e.g. 0.5-2 ms.

The filling of the seal can be done before, after or simultaneously with the filling of the explosion chambers. If the seal is not continuously supplied with sealing gas, this is preferably carried out simultaneously or after filling the chambers. This guarantees that the sealing area is completely filled with sealing gas just before the ignition of an explosion and that any explosive gas that has penetrated into the area is forced out of it. When two igniters are used, it is preferable to use 'fast' devices such as spark plugs or laser ignitions since both firings must be precise at a precise time. Even with a coordination of several devices according to the invention, such rapid ignition devices are preferred. By using multiple devices in parallel, mutually reinforcing effects can occur and be exploited. For example, to clean large boilers by simultaneously igniting multiple explosions in several explosion generators, the pressure waves or pulses are cumulative, thereby enhancing the cleaning effect or instead the number of cleaning devices can be reduced.

Preferably, however, only one igniter is used in an auxiliary explosive chamber and one delay line. Then, for example, this can be a rather 'slow' glow plug, which requires a few seconds, about 3 seconds, to heat up. An ignition device by laser, a laser ignition, is possible. In this case, a laser beam is coupled into the pressure-resistant container. The laser beam can directly ignite the gas or else it heats a certain point of the surface in the container, at which the explosive gas located in the container then ignites. For this purpose, the pressure-resistant container on a continuous for the corresponding laser wavelength window. Advantage of this device is that no ignition elements are in the chamber, which are subject to wear, dirty or can be destroyed by the explosion. Also, no electrical feedthroughs are required in the pressure-resistant container. A laser beam can be focused on very high energy densities, is very precise, highly accurate in time, and can even use surface contaminants that would be detrimental to other igniters. The forces acting on the piston or generally on the closure means and in particular the heat arising in the area of the piston discharge opening when the pressure wave escapes are extremely high. Due to the auxiliary explosion, the piston is already displaced from the area of the exhaust opening to the rear before the actual explosion and thus spared. At the same time but also causes the generated pressure wave unhindered and unrestrained leave the device.

The gas in the gas spring chamber is compressed by the receding piston more and more. As a result, on the one hand prevents the piston unbraked due to the explosion hits the rear wall of the pressure vessel, on the other hand, the piston is then returned to its original position, the closing position of the discharge port, as soon as the actual explosion is over. Thus, the device is automatically returned to its original position after an explosion and the explosion production process can be restarted with the filling of the chambers. With the inventive seal, which acts as Durchzündsperre, also an unwanted premature main explosion can be prevented.

The inventive seal has been described in detail for use in an explosion generator. Such a seal can also be used in other devices where a Durchzündsperre required or advantageous.

Claims

Seal for a pressure wave generator comprising a pressure-resistant container (1) with chambers introduced therein, a supply for supplying fluent explosive material into two chambers, these two chambers being separated from each other by a movable piston (3), characterized in that a seal of the Piston with respect to a container wall is designed as a fluid seal and Durchzündsperre.

Seal according to claim 1, comprising a non-explosive, non-flammable fluid, for example a non-explosive, non-flammable gas or a non-explosive liquid, such as water.

A gasket according to claim 2, wherein the non-explosive non-flammable gas is nitrogen, oxygen, natural gas or air.

Seal according to one of the preceding claims, with a supply line (16) for supplying a non-explosive, non-ignitable fluid in a sealing region.

Seal according to one of the preceding claims, wherein the piston (3) or a housing in a sealing region is provided with a groove (12).

A gasket according to claim 5, wherein the groove (12) is circumferential.

7. Seal according to one of the preceding claims, wherein the non-explosive, non-ignitable fluid is pressurized, which pressure corresponds to a pressure of the flowable explosive material in at least one chamber.

A seal as claimed in any one of the preceding claims, including an ignition device (10) in one chamber for causing an explosion of said one chamber and a delay line (22) to conduct the explosion into the other chamber or to a first explosion delayed release circuit an explosion in the other chamber via a further ignition device mounted in the other chamber, wherein the fluid seal over at least the duration of a delay acts as a strike-through barrier from one to the other chamber.

9. A method for producing a Durchzündsperre in a pressure wave generator, comprising two flowable, explosive material-containing areas and a movable, the two areas against each other sealing piston (3), characterized in that a sealing area between the piston and the two explosive material-containing areas by a non-explosive, non-ignitable fluid is sealed.

10. The method of claim 9, wherein the fluid is supplied to the sealing area and pressurized.

REPLACEMENT TABLE (REGEt26) - -

1 1. The method of claim 10, wherein the pressurization of the fluid substantially corresponds to a pressurization of a flowable explosive material in at least one of the areas.

12. The method according to any one of claims 9-11, wherein the fluid is introduced into a circumferential groove (12) in the piston (3).

13. The method according to any one of claims 9-12, wherein the fluid is supplied via a separate feed line (16).

14. The method according to any one of claims 9-13, comprising the following steps: a) filling both areas with a flowable, explosive material;

b) filling the non-explosive, non-ignitable fluid into one

Sealing area;

c) igniting the explosive material in one area;

d) delayed ignition of the explosive material in the other area;

If necessary, repeat steps a) -d)