JP3224640B2 - Apparatus and method for measuring concentration by LIF - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LIF (Laser Induced Fluo) used for measuring the concentration and temperature of chemical species in pulverized coal burners, diesel engines, boilers, and the like.
The present invention relates to an apparatus and a method for measuring concentration by rescense.

[0002]

2. Description of the Related Art A conventional general LIF concentration measuring apparatus is shown in FIG. In FIG. 1, reference numeral 1 denotes a pulse laser for excitation. A dye laser 2 is oscillated by the pulse laser 1 for excitation, and a laser beam having a wavelength corresponding to the electron energy of a molecule to be measured such as NO is output. The laser beam oscillated from the dye laser 2 is applied to the measurement field 4 after being formed into a sheet in the beam expander 3.

[0003] Fluorescence emitted from a molecule to be measured excited in the measurement field 4 is collected by a lens 5 and then condensed.
It is measured by the D camera 6. The CCD camera 6 is connected by a synchronization line 7 to synchronize with the oscillation of the dye laser 2.

In the concentration measurement by LIF, as shown in FIG. 5, the fluorescence absorbs incident light having a wavelength corresponding to the electron energy difference of the molecule to be measured, and the molecule absorbs the incident light. After being excited to the ground level, it is observed during transition to a stable ground level through the process of radiation and collision.

[0005] The concentration of the molecule to be measured is determined by the intensity of the fluorescence from the molecule to be measured. For example, as shown in FIG. 6, the fluorescence intensity is 200 ppm, 500 ppm, 10 ppm.
In the case where three types of 00 ppm are measured, the molecular concentration of the measurement field where 1000 ppm is measured is high. However, in a liquid combustion field, a solid combustion field, or the like, generally, not only the fluorescence from the measurement target molecule but also background light (background fluorescence) is emitted from the liquid fuel or the solid fuel as shown in FIG.

[0006]

In order to determine the concentration of the molecule to be measured, it is necessary to remove the background light.
Since this background light is emitted simultaneously with the fluorescence from the molecule to be measured, it is difficult to separate these two fluorescences. For this reason, conventionally, a liquid combustion field or a solid combustion field has
There was a problem that the IF could not be applied.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an apparatus and method for measuring concentration using LIF, which can measure concentration using LIF even in a liquid combustion field or a solid combustion field. I do.

[0008]

According to the present invention, there is provided an LIF-based concentration measuring apparatus which emits an excitation pulse laser beam.
An excitation pulse laser and an excitation pulse laser beam.
Wavelength at which fluorescence from the molecule to be measured peaks
Dye laser that excites a first laser beam
And the measurement object based on the excitation pulse laser beam.
Second laser having a wavelength that does not generate fluorescence from molecules
A second dye laser for exciting light, and the first laser light
And irradiating the measurement field with the second laser light at a predetermined time difference
Means for releasing the shutter according to the time difference,
The target molecule excited by the first laser beam
A first CCD camera for photographing the fluorescent light and the background light;
Photographing background light excited by the second laser light;
A second CCD camera, and an output of the first CCD camera.
Subtracting the output of the second CCD camera from the force
Means for extracting the fluorescence emitted by the molecule to be measured
It is characterized by the following.

Further, in the method for measuring the concentration by LIF according to the present invention, the fluorescence from the molecule to be measured peaks.
Irradiating a measurement field with a first laser beam having a wavelength,
From the target molecule excited by the laser light
Of the fluorescence and background light of the first camera,
A second laser having a wavelength that does not generate fluorescence from an elephant molecule
The measurement field is irradiated with laser light and the second laser light
The background light excited by the second camera is photographed by the second camera.
From the output of the fluorescence and background light taken by the camera
Measured by subtracting the output of the background light captured by camera 2
It is characterized in that only the fluorescence of the target molecule is extracted.

[0010]

The first and second dye lasers are oscillated by the laser light from the excitation pulse laser. At this time,
Fluorescence from the target molecule from the first dye laser peaks
A first laser beam having a wavelength such that
After that, at a short time interval, the second dye laser has a wavelength that does not generate fluorescence from the molecule to be measured.
The second laser light is output. The two laser beams having different wavelengths are combined via a mirror, a beam splitter, and the like, and then applied to a measurement field.

In the measurement field, the excited fluorescence from the molecule to be measured and the background of liquid fuel, solid fuel, etc.
The images, which operate in synchronization with the first and second dye lasers, are photographed by two CCD cameras. At this time, fluorescence and background light from the molecule to be measured are photographed by a CCD camera synchronized with the first dye laser, and the CCD camera synchronized with the second dye laser.
The CD camera captures only background light.

Accordingly, by subtracting the output of one of the two CCD cameras from the other, only the fluorescence emitted from the molecule to be measured can be extracted, and the two-dimensional concentration distribution of the molecule to be measured can be known.

[0013]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a configuration of a concentration measuring apparatus using LIF (Laser Induced Fluorescence) according to an embodiment of the present invention.

As shown in FIG.
Is split by a beam splitter 12, one of which is sent to a first dye laser 13a, and the other is reflected by a mirror 14 and reflected by a second dye laser 13a.
b. The dye lasers 13a and 13b oscillate with laser light from the excitation pulse laser 11, and output measurement laser lights La1 and La2. This dye laser 1
Laser light La1, La2 output from 3a, 13b
Are coaxially combined by a mirror 15 and a beam splitter 16 and are irradiated via a beam expander 17 to a measurement field 18 such as a liquid combustion field or a solid combustion field.

In this case, in the dye laser 13a, the fluorescence from the molecule to be measured in the measurement field 18 has a peak.
The laser beam La1 having such a wavelength is generated, and the dye laser 13b emits a wavelength that does not generate fluorescence from the molecule to be measured.
And is set to generate a laser beam La2 for obtaining background light from the background of the liquid fuel, the solid fuel, or the like in the measurement field 17. Further, the dye laser 13a and the dye laser 13b have a slight time difference, for example, 50 to 10 minutes.
The laser beams La1 and La2 are set to be generated with a time difference of 0 ns.

The fluorescence generated in the measurement field 18 by the irradiation of the laser beams La1 and La2 is transmitted to the lenses 19a and 1a.
The light is condensed by 9b and photographed by the CCD cameras 20a and 20b. In this case, the CCD cameras 20a and 20b perform a shutter operation in synchronization with a synchronization signal given from the dye lasers 13a and 13b via the synchronization lines 21a and 21b.

Image information captured by the CCD cameras 20a and 20b is sent to an image processing circuit (not shown). This image processing circuit obtains a two-dimensional density distribution by extracting the fluorescence intensity of only the measurement target molecule by subtracting the image captured by the CCD camera 20b from the image captured by the CCD camera 20a.

Next, the operation of the above embodiment will be described.
Generally, the range of the wavelength at which the measurement target molecule is excited (emits fluorescence) is very narrow, and has a strong excitation wavelength (laser wavelength) dependence. On the other hand, fluorescence from liquid fuel, solid fuel, and the like has little dependence on the excitation wavelength.

Therefore, as shown in FIG. 2, two laser beams having different wavelengths, that is, the fluorescence from the molecule to be measured has a peak.
Laser beam La1, and measurement pairs having a wavelength such that
Having a wavelength that does not generate fluorescence from elephant molecules, liquid fuel,
When a laser beam La2 for obtaining background light emitted from a background portion such as a solid fuel is used, as shown in FIG.
1 can measure the intensity of the fluorescence from the molecule to be measured and the background light (fluorescence from the molecule to be measured plus the fluorescence intensity from the liquid or solid fuel), and the laser beam 2 can be used to measure the background light (fluorescence intensity from the liquid or solid fuel). Only can be measured.

That is, the excitation light from the excitation pulse laser 11 first causes the dye laser 13a to emit the laser light La1 from the dye laser 13a.
, And after a very short time, for example, 50 to 100 ns
Thereafter, a laser beam La2 is generated from the dye laser 13b and irradiated to the measurement field 18. Then, the CCD cameras 20a and 20b are operated in synchronization with the irradiation of the laser light, and the fluorescence in the measurement field 18 is photographed. As a result, the CCD camera 20a captures fluorescence and background light from the measurement target molecule based on the laser beam La1, and the CCD camera 20b captures only background light based on the laser beam La2.

Then, the photographed images of the CCD cameras 20a and 20b are output to an image processing circuit, and as shown in FIG.
From the fluorescence A (fluorescence due to the molecule to be measured + background light) obtained from the image captured by the D camera 20a, the CCD camera 20b
By subtracting the fluorescence B (background light) obtained from the photographed image, the fluorescence intensity of only the measurement target molecule can be extracted, and the two-dimensional concentration distribution of the measurement target molecule can be known.

[0022]

As described above in detail, according to the present invention, L
In the concentration measurement by IF, the background light from the background part such as liquid fuel and solid fuel can be removed, and the two-dimensional gas component concentration measurement in pulverized coal burners, engines, etc., which was difficult to measure conventionally, using LIF Can be.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a concentration measuring device using LIF according to one embodiment of the present invention.

FIG. 2 is a diagram showing fluorescence characteristics from molecules to be measured and liquid / solid fuel in the same example.

FIG. 3 is a view related to removal of background light according to the embodiment.

FIG. 4 is a block diagram showing a configuration of a conventional concentration measurement by LIF.

FIG. 5 is a diagram for explaining fluorescence in a conventional concentration measurement by LIF.

FIG. 6 is a diagram showing a relationship between a concentration and a fluorescence intensity in a conventional concentration measurement by LIF.

FIG. 7 is a view for explaining background light in a conventional concentration measurement by LIF.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Excitation pulse laser 12 Beam splitter 13a, 13b Dye laser 14, 15 Mirror 16 Beam splitter 17 Beam expander 18 Measurement field 19a, 19b Condensing lens 20a, 20b CCD camera 21a, 21b Synchronization line

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-58444 (JP, A) JP-A-61-213974 (JP, A) JP-A-2-71135 (JP, A) JP-A-3- 150448 (JP, A) JP-A-64-9345 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/62-21/74 JICST file (JOIS)

Claims (2)

(57) [Claims] 1. An excitation pulse laser beam for excitation is emitted.
A pulse laser and, based on the excitation pulse laser light,
Laser having a wavelength such that the fluorescence of the light becomes a peak
A first dye laser that excites light, and the measurement target molecule based on the excitation pulse laser light.
A second laser beam having a wavelength that does not generate fluorescence from
A second dye laser to be excited, and the first laser light and the second laser light
A means for irradiating the measurement field with a time difference, and a shutter released in accordance with the time difference;
Fluorescence from the measurement target molecule excited by light and
A first CCD camera for photographing background light and the second CCD camera;
Second CC for capturing background light excited by laser light
D camera and the second CCD camera from the output of the first CCD camera.
Fluorescence emitted by the molecule to be measured by subtracting the output of the camera
And a means for extracting
Concentration measuring device. 2. The fluorescence from the molecule to be measured reaches a peak.
The measurement field is irradiated with a first laser light having such a wavelength, and the measurement object is excited by the first laser light.
The fluorescence from the child and the background light are photographed by the first camera, and have a wavelength that does not generate fluorescence from the molecule to be measured.
Irradiating the measurement field with a second laser beam, and applying background light excited by the second laser beam to a second laser beam;
The fluorescence and background light output from the first camera
Subtract the output of the background light captured by the second camera
And extracts the fluorescence of only the molecules to be measured.
Concentration measurement method using LIF.