JP5501435B2 - Laser multi-point ignition device - Google Patents

Description

  The present invention relates to a multi-point output laser generator that emits a plurality of parallel lasers, and in particular, is a seed of a high-intensity laser used in a new laser multi-point ignition gas combustion engine that forms a distributed ignition point and operates efficiently. The present invention relates to a multi-point output laser generator for generating a plurality of lasers and a laser multi-point ignition device using the same.

  If the gas engine is laser-ignited and a plurality of ignition points are distributed appropriately and laser ignition is performed simultaneously or according to an appropriate sequence, the combustion speed of the gas in the engine can be improved or unburned gas components can be reduced. Thus, the combustion efficiency can be greatly improved.

  In particular, in order to improve fuel efficiency and suppress NOx in a gas combustion engine, a method in which the fuel gas is diluted and burned in abundant air has been studied. Since the lean gas mixture has poor ignitability, the conventional spark plug does not sufficiently ignite because the heat escapes to the wall and the temperature does not rise sufficiently, so a method of performing multi-point ignition using a laser at a position away from the wall is adopted. By using the laser ignition device, it is possible to select a number of positions away from the wall in the combustion chamber more easily than the spark plug, and to ignite by focusing on that point.

  However, in the laser ignition device, in order to avoid igniting the fuel gas before reaching the target position, the energy density of the laser beam is suppressed to an appropriate value, and the ignition energy is not started until the laser is focused on the ignition position. Need to reach. For this reason, the laser beam before condensing is required to have an appropriate thickness and an appropriate energy density.

  In order to ignite simultaneously at a plurality of ignition points, it is desirable that the intensity and energy distribution of the incident laser beam are the same, and the optical paths are almost equal to the ignition point.

  Patent Document 1 discloses a laser-type multipoint ignition device. In the disclosed apparatus, the laser light emitted from the laser generation source is magnified by an expander lens, adjusted to a parallel beam having a predetermined diameter by a condenser lens and a collimating lens, and then passed through a microlens array. To introduce. The laser light divided into a plurality of light beams according to the number of microlenses concentrates energy at a predetermined depth according to the focal length of each microlens and ignites the mixture.

  However, the laser ignition device according to the disclosed invention is structured to obtain a plurality of beams by irradiating a large-diameter parallel laser beam onto the microlens array. Since the position is limited to just below the optical window, the ignition point cannot be distributed in a wide range of optimum positions in the combustion chamber, and truly efficient combustion cannot be performed.

In order to obtain a laser type multi-point ignition device that can withstand practical use, it is necessary to provide a multi-point output laser device that generates a plurality of independent laser beams that can be freely converged to an optimum position in the combustion chamber.
The laser beam is a beam having an appropriate cross-sectional area having an energy density that reaches an ignition energy by being converged, and a plurality of beams have the same shape and intensity, and have the same optical mechanism. It is preferable that it can be used and introduced into the combustion chamber to ignite the combustion gas.

Patent Document 2 includes one optical resonator using a solid-state laser medium for a semiconductor laser element array in which a plurality of semiconductor laser elements are arranged in a row, and laser beams emitted from the laser elements are individually received. A semiconductor laser device is disclosed that is configured to be incident on an optical resonator, and to be independently amplified by resonance and emitted.
In the apparatus disclosed in the document, a plurality of laser beams are emitted from independent semiconductor laser elements, amplified at different positions of the optical resonator, and emitted. Therefore, homogeneity between the multiple beams is not guaranteed.
Japanese Patent Laying-Open No. 2005-147109 JP 2004-111542 A

  The problem to be solved by the present invention is a multi-point output laser generator for generating a plurality of homogeneous parallel laser beams, particularly a laser multi-point for efficiently igniting and burning by distributing a plurality of ignition points at appropriate positions. To provide a multi-point output laser generator for generating a plurality of lasers as seeds for a multi-point high-intensity laser used in an ignition gas combustion engine, and a laser multi-point ignition device using the same.

The multi-point output laser generator according to the present invention includes an unstable resonator formed by interposing a laser medium between a rear mirror and an extraction mirror, and a plurality of single-mode laser beams generated by the unstable resonator. Distribution means for cutting out the laser beam.
In the unstable resonator, the laser beam is amplified by the laser medium and expanded by the extraction mirror and the rear mirror, and a high-quality single-mode ring laser beam is emitted from the periphery of the extraction mirror.

In the present invention, a plurality of laser beams are cut out from the single mode laser beam by the distributing means.
The distribution means may be provided with a plurality of openings through which the laser light is transmitted at a position irradiated with the ring-shaped laser light emitted from the periphery of the take-off mirror of the unstable resonator.
Since the ring-shaped laser beam has a uniform energy distribution in the circumferential direction, a plurality of laser beams obtained from a plurality of openings distributed on concentric circles have the same quality and have the same energy.

  The distribution means is a ring-shaped scraper mirror having a reflection surface at the periphery and an opening at the center, and is arranged in an unstable resonator to generate laser light generated at the periphery of the resonator. You may take out outside. When a ring-shaped scraper mirror is used, a plurality of laser beams may be directly cut out using a scraper mirror having a plurality of reflecting surfaces formed corresponding to a plurality of laser beams to be extracted, or once extracted into a ring shape. A plurality of laser beams may be cut out using a distribution plate having a plurality of openings.

Further, a beam expander may be provided between the unstable resonator and the distribution means.
By widening the laser beam output from the resonator, the distribution to the distribution means can be performed easily and accurately.
Further, a focusing unit that refracts the plurality of beams in the central axis direction is disposed downstream of the distributing unit, and the generated plurality of laser beams can travel in parallel to each other and can be supplied as a parallel beam to the downstream amplification device. You may do it.
In addition, an image relay may be arranged downstream of the distributing means so that the beam intensity profile at the opening of the distributing means is maintained and transmitted downstream.

Multiple cut laser beams are further passed through an excited laser medium to increase the light intensity and injected into the combustion chamber of a multi-point ignition gas combustion engine, which is used to ignite a lean mixture efficiently. can do.
The laser multipoint ignition device of the present invention focuses the multipoint output laser generator of the present invention, a focusing means for refracting a plurality of laser beams taken out from the multipoint output laser generator, and a plurality of laser beams. A laser amplifying apparatus having an optical amplifier for amplifying each laser beam disposed at a position, a reflecting mirror for deflecting the amplified laser beam to a combustion chamber of a multi-point ignition gas combustion engine, and a condensing beam for condensing the laser beam And a lens for efficiently igniting the lean air-fuel mixture in the combustion chamber.
A laser supply device for a multi-point ignition gas combustion engine is configured to focus a plurality of seed laser beams emitted from a multi-point output laser generator that emits a plurality of laser beams by a focusing means so that the beam axis is within a solid-state laser medium. The laser beam is guided so as to pass therethrough, and each laser beam is optically amplified in the laser medium and emitted as an independent laser beam.
The solid-state laser medium can be excited using a semiconductor laser device placed outside the medium.

  According to the above laser multipoint ignition device, a plurality of seed laser beams emitted from the laser generator are each optically amplified in a solid laser medium excited to an appropriate intensity from the outside, so that a larger appropriate As a plurality of substantially homogeneous independent laser beams having light intensity, they can be focused through a condenser lens into a combustion chamber of a gas combustion engine and ignited at a plurality of positions.

Hereinafter, a multipoint output laser generator and a laser multipoint ignition device of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory diagram of a multi-point output laser generator according to a first embodiment of the present invention, FIG. 2 is a conceptual diagram of a laser multi-point ignition apparatus using the laser generator of the first embodiment, and FIG. FIG. 4 shows a multi-point output laser generator according to the third embodiment of the present invention, FIG. 4 shows a multi-point output laser generator according to the third embodiment of the present invention, and FIG. 5 shows a fourth embodiment of the present invention. FIG. 6 is a diagram showing a multi-point output laser generator according to a fifth embodiment of the present invention.

  The multipoint output laser generator of this embodiment includes an unstable resonator 1 formed by disposing a solid-state laser medium 13 between a rear mirror 11 having a concave reflecting surface and an extraction mirror 12 having a convex reflecting surface, Distributing means 2 is provided where the output laser of the stable resonator hits.

  The unstable resonator 1 is generally configured as a right-branch confocal type in which the relationship of R1-R2 = 2L is established, where R1 and R2 are the radii of curvature of the rear mirror 11 and the extraction mirror 12, respectively, and the resonator length is L. ing. The laser light introduced into the solid-state laser medium 13 through the rear mirror 11 is amplified while being repeatedly reflected between the rear mirror 11 and the take-out mirror 12, and the beam diameter is enlarged and output as a ring-shaped parallel laser beam 14.

In the unstable resonator 1, the laser oscillates in a single mode, the inner diameter of the extracted laser beam 14 is the outer diameter 2A of the extraction mirror 12, and the outer diameter is M × 2A. Here, M is an enlargement ratio, and M = R1 / R2.
The energy of the ring-shaped laser beam 14 is uniform in the circumferential direction and has a distribution that decreases in the radial direction along the outline of the Gaussian distribution toward the outside.

  A similar ring-shaped laser beam is also used when a negative branch confocal unstable resonator is used that uses a take-out mirror 12 having a concave reflecting surface with a radius of curvature R2 so that the relationship R1 + R2 = 2L is established. Can be taken out.

The distribution means 2 is a metal disk provided with a plurality of openings 21 at the circumferential position where the ring-shaped output laser 14 hits.
The ring-shaped laser beam 14 is split by passing through the distribution means 2 and emitted as a plurality of columnar laser beams 22. The plurality of laser beams 22 are single mode lasers having the same output and the same energy distribution.

    In the multipoint output laser generator of the present embodiment, a plurality of laser beams 35 in the combustion chamber 51 are obtained by branching a ring-shaped laser beam having a uniform energy distribution in the circumferential direction on the circumference to obtain a plurality of laser beams 35. They are arranged at approximately equal intervals around the periphery and have substantially the same cross-sectional area and light energy intensity. For this reason, a mechanism for allowing the laser beam 35 to enter the combustion chamber 51 can be easily configured.

The multipoint output laser generator of the present embodiment is used, for example, as an ignition device for a laser multipoint ignition type gas combustion engine.
FIG. 2 is a view for explaining the concept of a laser multipoint ignition device using the multipoint output laser generator of this embodiment. Note that the same reference numerals as those in FIG. 1 are used for the elements representing the same functions as those in FIG.

The multi-point laser beam 22 output from the multi-point output laser generator 110 is supplied to the combustion chamber of the gas combustion engine 150 as a plurality of laser beams 35 supplied to the laser amplifier 130 and having increased light intensity.
As described above, the multipoint output laser generator 110 is formed by the unstable resonator 1 in which the solid-state laser medium 13 is disposed between the rear mirror 11 having a concave reflecting surface and the take-out mirror 12 having a convex reflecting surface, and the distributing means 2. Then, the laser beam is divided into a plurality of laser beams 22 having the same energy distribution and emitted from the ring-shaped laser beam 14.

The laser amplification device 130 includes a focusing unit 31 and an optical amplifier 32. The converging means 31 is, for example, a polygonal frustum-shaped optical component, and a laser beam 34 that refracts the laser beam 22 emitted from the multipoint output laser generator 110 incident on the wedge portion at the peripheral portion inward and focuses it to one point. And
The optical amplifier 32 is a solid-state laser medium, which is disposed at a position where a plurality of laser beams 34 are focused, and amplifies each laser beam equally to produce a high-intensity laser beam 35 having the same light intensity, thereby producing a region 150 of the gas combustion engine. To supply.

A reflecting mirror 41 for deflecting each high-intensity laser beam 35 toward the engine head is provided around the gas combustion engine 5, and the high-intensity laser beam 35 is introduced into the combustion chamber 51 through a condenser lens 42.
The high-intensity laser beam 35 contracts the diameter in the combustion chamber 51 to increase the energy density, reaches the ignition energy of the fuel gas at the focal position, and ignites the gas.

  The combustion speed can be improved by appropriately distributing the focal point of the laser beam so that the combustion chamber 51 is covered with a small fireball. Further, by setting the focal point in the air away from the wall, it is possible to prevent ignition energy from escaping through the wall and improve the ignition efficiency.

FIG. 3 is a view showing a multipoint output laser generator according to a second embodiment of the present invention.
In the laser generator of this embodiment, instead of extracting the output beam from the periphery of the extraction mirror 12, a donut-shaped scraper mirror 15 is provided between the rear mirror 11 and the extraction mirror 12 so as to be inclined by 45 ° with respect to the optical axis. The ring-shaped laser beam 16 is extracted in a direction perpendicular to the axis of the stable resonator.
The extracted ring-shaped laser beam 16 has the same properties as those shown in FIG. 1 and passes through the opening 21 of the distribution means 2 to become a plurality of laser beams 22 having a flat energy distribution, and downstream. Is supplied to the process.

FIG. 4 is a drawing showing a multipoint output laser generator according to a third embodiment of the present invention. In the laser generator of this embodiment, a beam expander 17 is provided between the take-out mirror 12 and the distribution means 2 to supply a beam 18 obtained by enlarging the ring-shaped beam 14 and facilitate distribution in the distribution means 2. The beam diameter required in the downstream process can be adjusted.
Since the ring-shaped beam 14 exists on the circumference, the beam expander 17 can be configured by arranging, for example, a combination of annular prisms having a triangular cross section in the circumferential portion where the beam exists.

FIG. 5 is a drawing showing a multi-point output laser generator according to a fourth embodiment of the present invention. The laser generator of this embodiment is a ring-shaped laser beam 20 that is widened by providing a diffusing means such as a concave lens 19 between the take-out mirror 12 and the distributing means 2 or behind the distributing means 2. This is applied to the case where a plurality of laser beams 23 formed by passing through the laser beam 23 are diffused with a radiation angle, and a focusing means 24 such as a convex lens is disposed behind the distributing means 2 and supplied to a subsequent process. The laser beams 25 are made parallel to each other.
When it is required to supply as a parallel beam, such as when the post-process is a laser amplification device, it can be handled by attaching a focusing means 24 as shown in FIG.

FIG. 6 is a drawing showing a multi-point output laser generator according to a fifth embodiment of the present invention. The laser generator of this embodiment is characterized in that an image relay 26 is arranged behind each opening 21 of the distribution means 2.
The image relay 26 transmits the energy image of the laser beam generated in the opening 21 as it is to the laser beam input position in the subsequent process. The laser generator of the present embodiment can be applied, for example, when the parallel laser beam 22 is supplied to the focusing means 31 of a laser amplifier used in a laser multipoint ignition gas combustion engine.

When the object image side focal position of the image relay 26 is adjusted to the aperture 21 and the image side focal position is adjusted to the beam input position of the focusing means 31, the intensity distribution of the laser beam 22 in the aperture 21 is incident on the focusing means 31. Therefore, the high-quality single-mode laser beam generated by the unstable resonator is transmitted to the focusing means 31 as it is.
Therefore, when the multipoint output laser generator of the present embodiment is used, extremely efficient engine ignition can be performed.

  The multi-point output laser generator of the present invention can supply a high-quality beam to those requiring a plurality of laser beams. In particular, a laser ignition device configured in combination with a laser amplification mechanism is useful for efficiently igniting a laser ignition type gas combustion engine.

It is a conceptual diagram explaining the multipoint output laser generator concerning 1st Example of this invention. It is a conceptual diagram of the laser multipoint ignition device using the laser generator of 1st Example. It is a conceptual diagram of the multipoint output laser generator which concerns on 2nd Example of this invention. It is a conceptual diagram of the multipoint output laser generator which concerns on 3rd Example of this invention. It is a conceptual diagram of the multipoint output laser generator which concerns on 4th Example of this invention. It is a conceptual diagram of the multipoint output laser generator which concerns on 5th Example of this invention.

DESCRIPTION OF SYMBOLS 1 Unstable resonator 2 Distributing means 5 Gas combustion engine 11 Rear mirror 12 Extraction mirror 13 Solid laser medium 14 Laser beam 15 Scraper mirror 16 Ring-shaped laser beam 17 Beam expander 18 Laser beam 19 Concave lens 20 Laser beam 21 Aperture 22 Laser beam 23 Laser beam 24 Focusing means 25 Laser beam 26 Image relay 31 Focusing means 32 Optical amplifier 34 Laser beam 35 High-intensity laser beam 41 Reflecting mirror 42 Condensing lens 51 Combustion chamber 110 Multi-point output laser generator 130 Laser amplifier 150 Gas combustion engine

Claims (4)

An unstable resonator formed by interposing a laser medium between a rear mirror and a take-out mirror, and a ring-shaped scraper mirror having a reflection surface at a peripheral portion and an opening at a central portion, the rear mirror and the A scraper mirror that is installed between the take-out mirrors and takes out the laser beam generated at the peripheral edge of the resonator to the outside, and a plurality of laser beams that pass through the position irradiated by the ring-shaped laser light emitted from the scraper mirror A multi-point output laser generator including a distribution unit provided with an aperture; a focusing unit that refracts a plurality of laser beams extracted from the multi-point output laser generator; and a position at which the plurality of laser beams are focused A laser amplifying apparatus provided with an optical amplifier for amplifying each laser beam, and the amplified laser beam for the multi-point ignition gas combustion energy And a gin combustion reflector for deflecting the chamber and the condenser lens for condensing the laser beam, the laser multi-point ignition device, characterized in that to efficiently ignite the lean mixture in the combustion chamber. Laser multipoint ignition device according to claim 1, characterized by comprising a beam expander between the distribution means and said scraper mirror. Diffusion means and the second focusing means downstream of the extraction mirror arranged, according to claim 1 or 2, wherein said plurality of laser beams to be supplied to the subsequent process is characterized in that so as to run parallel to each other Laser multi-point ignition device . Wherein the optical axis of the laser beam transmitted through the plurality of openings of the dispensing means to place the image relay having axes, the intensity profile of the laser beam in the opening of claim 1, wherein the transmitting to the downstream of the 3 The laser multipoint ignition device according to any one of the above.

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