Patent Application
20230010643
The invention relates to a device and a method for generating high intensity pressure pulses. In particular, it relates to a pressure wave generator and a method of operating a pressure wave generator according to the preamble of the independent patent claims.
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 each other. The auxiliary explosion serves to release a shutter of the main explosion chamber directly or via other latch mechanisms, so that a subsequent main explosion does not act with full force on the shutter and impair or destroy it accordingly. An explosion delay takes place between the auxiliary and main explosion. Such a delay takes place, for example, by means of a delay line in which an explosion is conducted from an auxiliary to a main chamber or by means of delayed ignition in the two chambers via separate ignition devices present in the chambers.
There is a need for a simplified pressure wave generator.
It is thus a possible objective of the invention to provide a pressure wave generator which is simplified with respect to the known devices.
It is a possible further objective of the invention to provide a pressure wave generator which is more robust and/or durable compared to known devices.
At least one of these objectives is solved by a pressure wave generator and a method of operating a pressure wave generator according to the patent claims.
The method is for operating a pressure wave generator having a pressure chamber, the pressure wave generator comprising
Within the discharge time period, the pressure in the pressure chamber has dropped to the ambient pressure.
In embodiments, a volume of the pressure chamber is more than three liters, more particularly more than four liters, more particularly more than five liters.
In embodiments, the area at a narrowest point of the outlet is more than twenty square centimeters, more particularly more than eighty square centimeters, more particularly more than one hundred eighty square centimeters.
In the case of a circular outlet, the above values for the area at the narrowest point, relative to its diameter and rounded, correspond to the diameter being more than five centimeters, in particular more than ten centimeters, in particular more than fifteen centimeters.
In embodiments, an opening speed of the closure element is more than ten meters/second, more particularly more than twenty meters/second, more particularly at least thirty meters/second.
In embodiments, a stroke of the closure element during the opening and closing movement is between thirty and one hundred and fifty millimeters, in particular between forty and one hundred millimeters, in particular between fifty and eighty millimeters.
In embodiments, filling the pressure chamber with the working medium occurs at a pressure of more than one hundred fifty bar, in particular more than two hundred bar.
In embodiments, the discharge time duration is less than ten milliseconds, more particularly less than five milliseconds, more particularly less than three milliseconds.
In embodiments, the working medium is one of air, nitrogen, and steam, particularly superheated steam or saturated steam.
In embodiments, the method comprises the following step performed after filling and before opening the pressure chamber:
In embodiments, the method comprises the following step performed during filling of the pressure chamber:
In embodiments, the working medium is heated to a temperature of 150 degrees Celsius to 250 degrees Celsius, in particular to 230 degrees Celsius, or to a temperature of 200 degrees Celsius to 450 degrees Celsius, in particular to 250 degrees Celsius. Relatively speaking, the heating can take place, for example, by a temperature difference of more than 100 degrees Celsius, in particular more than 200 degrees Celsius, in particular more than 300 degrees Celsius, and in some circumstances more than 400 degrees Celsius. The heating can be done, for example, with an electric heating element. The outflow velocity and thus a pulse of the outflowing working medium increase with the square root of the temperature.
Another effect of heating the working medium is that the working medium can be prevented from cooling down too much when it flows out of the pressure chamber. As it flows out, the working medium relaxes to ambient pressure and can thus cool to a temperature below its liquefaction temperature, depending on the circumstances and which working medium is present. As a result, the jet spreads out after discharge at no more than the speed of sound, which limits the effect of the device.
In embodiments, a heater is present, which is arranged to heat the working medium in the pressure chamber, in particular an electric heater.
In embodiments, a heater is provided which is disposed in the working medium fill line for heating the working medium.
In embodiments, the heater is a heat exchanger, in particular with heat exchanger elements, in particular with electrically heated heat exchanger elements.
In embodiments, the method is performed using a pneumatic actuator, which comprises
In embodiments, the method is performed using a pneumatic actuator, which comprises:
The pneumatic actuator can be used to move the closure element from the closed position to the open position and, in particular, from the open position to the closed position.
The method comprises the repeated performance of the following steps:
Steps a), b) and c) can be performed simultaneously or overlapping in time. Step d) is typically performed after steps a), b) and c). In step d), the opening of the pressure chamber, triggered by the opening of the inlet/outlet port, passes directly into step e).
In embodiments, a time duration between the initiation of the opening movement of—the closure element, for example by actuation of a discharge solenoid valve, and the maximum opening of the closure element is in the range of 20 milliseconds to 120 milliseconds, in particular between 40 milliseconds and 60 milliseconds.
In embodiments, the time duration for opening the closure element is thereby less than ten milliseconds, in particular less than five milliseconds, in particular less than three milliseconds. It may be substantially equal to the discharge time duration.
The pressure wave generator according to a first aspect is used to perform the method described above. It comprises a pressure chamber, and
This allows the pressure wave generator to produce an exit jet which, after free jet expansion in the free space, generates the greatest possible maximum pressure there, or the greatest possible force. For this purpose, the mass flow generated by the pressure wave generator is made as large as possible. The mass flow is proportional to the density and exit velocity of the working medium and to the area of the exit opening. Thus, starting from a predefined filling pressure of the gaseous working medium in the pressure chamber, a combination of parameters can be determined within the limits defined above, which generates the maximum pressure of the exit jet.
In embodiments, a closure area of a closure opening that is respectively closed and opened by the closure element is at least as large as the area at the narrowest point of the outlet, in particular at least ten percent larger than the area at the narrowest point of the outlet.
This is in contrast to a usual valve, where the valve forms the narrowest point. In the narrowest cross-section, the gas flows at the speed of sound. If this point is not at the end of the outlet, supersonic flow occurs after the narrowest point. This leads to compression shocks in the outlet, which impede the performance of the device. By having the expansion of the exit jet outside the outlet, this is prevented.
In embodiments, the closure element is hollow cylindrical and arranged to close or open a closure opening corresponding to a cylindrical surface.
The hollow cylindrical design allows a reduction in the mass of the closure element. In addition, the annular surface of the piston surrounding the hollow cylindrical recess determines a recoil force with which the escaping gases drive the piston back. In embodiments, when viewed in cross-section, the area of the hollow cylindrical recess is more than twenty-five, particularly more than fifty, percent of the area of the closure element. The cylindrical closure surface allows for a large change in area of the closure surface as a function of movement of the closure.
In embodiments, a sum of areas on the closure element where the pressurized working medium exerts a force on the closure element in the closing direction is less than ten percent of the cross-sectional area of the outlet at the point where the outlet is closed by the closure element.
In embodiments, an area of the inlet/outlet opening of the first volume is between two hundred square millimeters and five hundred square millimeters, or a maximum of one thousand five hundred square millimeters. For a round cross-section of the opening, this corresponds to a diameter, rounded, of between sixteen millimeters and twenty-five millimeters, or a maximum of forty-four millimeters. This allows sufficiently rapid emptying of the first volume and, in turn, a correspondingly rapid opening movement. It results that these diameters are by and large independent of the first piston area, i.e. the area of the piston in the first volume.
In embodiments, during an opening movement of the closure element, starting from an end position in which the closure element closes the closure opening, the closure element opens the closure opening only after covering a minimum distance. This distance is different from zero. In particular, this distance is more than five millimeters or more than eight millimeters.
A pressure wave generator according to a second aspect is used to perform the method described above. It comprises a pressure chamber, and
A pneumatic actuator, particularly for use in a pressure wave generator, comprises:
In embodiments, the pneumatic actuator has end position damping, in particular by closing the inlet/outlet opening. Thus, the inlet/outlet opening is closed with respect to the first volume.
In embodiments, a piston closure element is arranged to close the inlet/outlet opening. Thus, the end position damping can be realized in a simple manner by an element of the piston itself.
In a method of operating the pneumatic actuator, the following steps are performed:
It is thus possible to realize a reciprocating movement of the actuator with simple means—only the filling valve and the inlet/outlet opening. This is a consequence, on the one hand, of the surface difference between the piston surfaces and, on the other hand, of the throttle between the two volumes.
The inlet/outlet opening can be made relatively large to effect the rapid pressure drop in the first volume.
In embodiments, the piston closure element is also arranged to isolate a control medium filling line with respect to the first volume. Thus, high pressure surges in the filling line can be avoided.
In embodiments, the two volumes are realized as parts of a common working chamber of a cylinder, in which a single piston is arranged, on which the two piston surfaces are formed.
This makes the sealing of the pistons against the (now common) cylinder non-critical. There may even be a gap between the piston and cylinder. This has the function of a throttle between the two volumes. Pressure compensation therefore takes place through this gap. This allows a further simplification of the design. In this embodiment, the throttle is thus formed by the gap between the cylinder and the piston. This dispenses with an otherwise customary seal for the piston.
In another embodiment, the two volumes and piston surfaces are on separate pistons in separate cylinders, and the two separate pistons are mechanically coupled and their movements are also coupled.
In embodiments, the first piston surface and a piston closure element for closing the inlet/outlet opening are formed on the same piston. This allows for a particularly simple and reliable design.
In embodiments, the pneumatic actuator comprises a cylinder discharge valve for rapidly discharging the control medium from the first volume by opening the inlet/outlet port. The cylinder discharge valve has a piston surface on which a force is generated to close the cylinder discharge valve when the control medium is applied, and a valve surface on which a force is generated in the opening direction of the cylinder discharge valve when the control medium is applied, wherein the valve surface is smaller than the piston surface. Thus, by applying the same pressure to both surfaces, the cylinder discharge valve can be brought into the closed position and held there.
In embodiments, the pneumatic actuator includes a discharge pilot valve for discharging control medium from a discharge valve volume in which the control medium acts on the piston surface. This can be used to create a momentary, temporary imbalance of pressure on the two surfaces, thereby opening the cylinder discharge valve.
In embodiments, a control medium filling line is arranged for filling both the discharge valve volume and the first volume with control medium under the same pressure. Thus, on the one hand, the same pressure can be achieved in the two volumes, and on the other hand—by the filling line acting as a throttle between the two volumes—the temporary imbalance can be realized.
The pressure in the control medium is, for example, between 50 and 140 bar, in particular between 80 bar and 100 bar.
In embodiments, a section of the control medium filling line, through which the first volume is supplied with the control medium, runs through the cylinder discharge valve, in particular a plug of the valve. For example, this section is a passage in the plug, which allows a small flow through the valve even in the closed position of the valve.
In embodiments, a portion of the control medium fill line through which the first volume is supplied with the control medium extends through a housing of the pressure wave generator.
In embodiments, a linear guide of the piston is formed by the piston enclosing a rear closure guide and being linearly movable along the rear closure guide in a direction of movement, and a hollow cylindrical piston connecting element extending away from the piston in the direction of movement enclosing a bearing element fixed to the rear closure guide. Here, the second volume is formed between the piston, an inner surface of the piston connecting element, the bearing element, and the rear closure guide. Typically, the rear closure guide is fixedly connected to the housing.
Thus, as an extension of the hollow-cylindrical piston connecting element, a hollow-cylindrical element can be driven, which is advantageous in certain applications. For example, this is the case with the pressure wave generator described here with a hollow cylindrical closure element.
Further preferred embodiments are shown in the dependent patent claims. Features of the method claims can be combined mutatis mutandis with the device claims and vice versa.
In particular, the pressure wave generator can have a controller which is configured to control the pressure wave generator in order to carry out the method according to at least one of the method claims. The control is performed by controlling at least the valves of the pressure wave generator.
In the following, the subject matter of the invention is explained in more detail on the basis of preferred embodiment examples, which are shown in the accompanying drawings. They show schematically:
In principle, same parts are given same reference signs in the figures.
The closure element 9 is guided on a bearing element 14, which allows a linear opening and closing movement of the closure element 9. In the embodiment of
The outlet 15 is used for the directional discharge or dischargeage of the working medium. A pressure wave can thus be generated.
In an open position, the closure element 9 releases a closure surface of a closure opening. In the closed position, the closure opening is closed by the closure element 9. Here, the closure surface is that of a cylinder. The pressure chamber 2 is annular. The pressure chamber 2 encloses the closure element 9. Starting from the pressure chamber 2, the closure opening leads inward in the radial direction—with respect to the annular pressure chamber 2. Working medium exiting through the closure opening flows inward in the radial direction and then in the axial direction—again with respect to the annular pressure chamber 2—through the outlet 15.
In the closed state, the closure element 9 is in contact with a valve seat of the housing 16. The valve seat can be designed with a collar, which means that when the closure element is moved in the opening direction, starting from an end position in the closed position, the closure opening is only opened and the working medium can flow out after the closure element 9 has covered a certain distance. This path is shown as collar width 77. This makes it possible to accelerate the movement of the closure element 9 before the closure opening is opened, which in turn makes it possible to open the closure opening sufficiently quickly to allow the working medium to flow out abruptly.
The size of the closure area is larger than the area of the outlet or outlet area, i.e. the cross-sectional area at which the outlet merges into the free space. In particular, the outlet 15 corresponds to the narrowest point along the path of the working medium out of the pressure chamber 2. As a result, the velocity of the outflowing working medium is highest at the outlet 15 or shortly thereafter. In particular, this causes the outflowing working medium to reach sonic velocity only shortly after the narrowest point, i.e. after outlet 15. This is advantageous for the operation of the device.
A first filling line or working medium filling line 12 is arranged for filling the pressure chamber 2 with a working medium. It is fed by a working medium valve 10.
In a method of operating the apparatus
In embodiments, the following parameters are implemented:
In embodiments, the following parameters are implemented:
In embodiments, the following parameters are implemented:
In embodiments, the following parameters are implemented:
In all embodiments, heating of the working medium to a temperature of 150 degrees Celsius to 250 degrees Celsius, in particular to 230 degrees Celsius, or to a temperature of 200 degrees Celsius to 450 degrees Celsius, in particular to 250 degrees Celsius, may be realized.
The opening movement of the closure element 9 is effected by an active gas spring or pneumatic actuator 4b. This has a cylindrical working chamber 43 with a piston 93 moving therein, the movement of which is coupled to the movement of the closure element 9, in particular by being firmly connected to one another, in particular by being formed in one piece. In the embodiments of
The piston 93 divides the working chamber 43 into a first volume 41 and a second volume 42. There is no seal between an inner cylinder wall 44 of the working chamber 43 and the piston 93. In particular, there may also be a small gap, hereinafter referred to as piston gap 96. This allows gas exchange between the two volumes and in particular acts as a throttle. In other embodiments, a separate conduit may be arranged between the first volume 41 and the second volume 42, and have a throttle which permits gas exchange in addition to or as an alternative to the piston gap 96. Such a throttle may also be implemented as a piston throttle 100 through one or more holes through the piston 93, which thus also allows gas exchange between the two volumes.
A gas pressure of the control medium in the first volume 41 causes a force against the direction of the opening movement of the closure element 9, whereby a surface effective in this case is a first piston surface 91.
A gas pressure of the control medium in the second volume 42 causes a force in the direction of the opening movement of the closure element 9, a surface effective in this case being a second piston surface 92.
Here, the second piston area 92 is smaller than the first piston area 91, for instance at least five or ten or twenty percent smaller.
The piston 93 has a piston closure element 95, which closes a cylinder inlet/outlet 45 or inlet/outlet opening of the first volume 41 in the course of the opening movement. The cylinder inlet/outlet 45 is drawn here concentric with the working chamber 43, but could alternatively be arranged laterally. By closing the cylinder inlet/outlet 45, a braking or end position damping of the opening movement is effected. At the same time, the compressed air valve 49 is also protected from a pressure surge through the compressed air filling line 48.
The cylinder inlet/outlet 45 can be opened by a cylinder discharge valve 46. The control medium flows out, for example, through a discharge or vent line 102. The cylinder discharge valve 46 may have a relatively large valve cross-section compared to a fill line. Thus, an abrupt pressure reduction in the first volume 41 can be realized. The cylinder discharge valve 46 is held closed by a pressure in a compressed air fill line 48. This pressure can be reduced by opening a discharge pilot valve 47. Thus, opening the bleed pilot valve initiates the opening movement of the closure element.
The cylinder discharge valve 46 is exemplarily a poppet valve with a movable plug. The plug has a piston surface 52 at which it is acted upon by the compressed air from the compressed air filling line 48 in a discharge valve volume 51. A valve surface 53, which is acted upon by the pressure in the cylinder inlet/outlet 45, is smaller than the piston surface 52, and the forces on the piston surface 52 and the valve surface 53 are opposite to each other. When the discharge pilot valve 47 is closed, the gas pressure on the two surfaces is the same, and the force on the piston surface 52 is higher than that on the valve surface 53, which keeps the plug or cylinder discharge valve 46 in the closed position.
The compressed air fill line 48 also feeds, via a portion 101 of the compressed air fill line 48, the first volume 41. The compressed air fill line 48 is in turn fed via a compressed air valve 49.
A ventilation line 97 provides pressure equalization between the ambient air and an intermediate cylinder. The intermediate cylinder is located between a rear end of the closure element 9 and the active gas spring or pneumatic actuator 4b.
In the variant of the embodiment of
In the embodiments of
In embodiments, a heating element 99 is provided. This can be used to heat the pressurized working medium in the pressure chamber 2. This can increase the energy of the generated pressure wave.
In the operation of this variant, the following method steps can be performed:
When using the pneumatic actuator 4b as described above, moving the closure element in the opening direction is done by moving the pneumatic actuator in the second direction. Moving the closure element in the closing direction is done by moving the pneumatic actuator in the first direction.
The operation is basically the same as that of the embodiment of
The piston connecting element 94, which connects the piston 93 to the closure element 9, is formed by a hollow cylinder. The piston 93 encloses a rear closure guide 98, which can be designed as a general cylinder, in particular as a circular cylinder, and can be moved linearly along the same in the direction of movement. The piston connecting element 94 surrounds the bearing element 14, which is fixedly connected to a housing 16. The second volume 42 is located between the rear closure guide, the piston 93 and the inside of the hollow cylinder or piston connecting element 94.
The throttle between the first volume 41 and the second volume 42 is implemented as a piston throttle 100 through one or more holes through the piston 93. In addition or alternatively, however, the function of the piston throttle can also be performed by a gap between the piston 93 and the rear closure guide 98.
The section 101 of the compressed air filling line 48, through which the first volume 41 is supplied with the control medium, does not run through the housing 16 but through the plug of the cylinder discharge valve 46, for example as a bore, and can also be called the piston throttle of the cylinder discharge valve 46. Thus, the first volume 41 is supplied with the control medium via the discharge valve volume 51.
End position damping can be dispensed with. If end position damping is to be implemented in the embodiment of
In embodiments (not shown), two or three or more closure elements 9 are arranged parallel to each other to increase a total outlet area. They can be triggered synchronously with each other or simultaneously, respectively, to generate a pressure wave of higher energy than with a single closure element 9. In this case, multiple closure elements are connected to a single pressure chamber 2 and are actuated by a single pneumatic actuator. Such a parallel arrangement of closure elements 9 can also be realized with pressure wave generators, which use explosions to generate the pressure in the pressure chamber and/or to drive the closure element.
A controller 20 is configured to carry out the method steps described. For this purpose, the controller 20 is configured to control the compressed air valve 49, the working medium valve 10 and the cylinder discharge valve 46. The cylinder discharge valve 46 can be controlled by means of the discharge pilot valve 47.
The heater can each have a heat exchanger 81 with heat exchanger elements 82 around which the working medium flows. The heat exchanger elements 82 can be heated by an electric heater 83.
In another embodiment, not shown, heat exchanger elements 82 are arranged in the pressure chamber 2.
| Number | Date | Country | Kind |
|---|---|---|---|
| 01347/19 | Oct 2019 | CH | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/079524 | 10/20/2020 | WO |
