JP2503164Y2 - Gas temperature measuring device - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a gas temperature measuring device applied to a gas temperature measurement of combustion gases such as various burners and engine cylinders.

[Conventional technology]

 A conventional device is shown in FIG.

In FIG. 6, a laser beam 2 oscillated from an excimer laser 1 is split into two by a half mirror 3 and a total reflection mirror 4 and excites dye lasers 5 and 6, respectively, which have different wave numbers w _p and w _s , respectively. Laser light is oscillated.

Here, the laser light of wave number w _p is called pumping light 7, and the laser light of wave number w _s is called Stokes light 8.

The wave number w _s of the Stokes light 8 is the wave number w _{p of the} pumping light 7.
And the wave number difference w _p −w _s is adjusted to be equal to the vibration energy level difference (the difference between the ground level and the first excited level) of the gas molecule (the nitrogen molecule in this case) to be measured. Has been done.

The pumping light 7 and the Stokes light 8 are combined into one by a dichroic mirror 9 and a total reflection mirror 10 that reflect only light of a specific wave number and pass light of other wave numbers, and are combined by a lens 11 at a measuring point 12 Is focused on.

A space including the measurement point 12 is called a test section 13.

From the measurement point 12, the difference between the wave numbers of the two laser beams 7 and 8 and the vibration energy level difference of the gas molecules are adjusted to be equal to each other.
Light, which is a coherent non-Stokes Raman diffusion (hereinafter referred to as CARS) light, is generated, and this CARS light is collimated by the lens 14 together with the other two laser light 7 and 8, and is changed by the dichroic mirror 15. It is separated into reflected light 16 and transmitted laser light 7 and 8.

In the light 16 reflected by the dichroic mirror 15, CARS light and a very small amount of laser light 7 and 8 remain,
Further, the dichroic filter 17 is used to separate the CARS light and the laser light.

The separated CARS light 19 is incident on one end 21a of the optical fiber 21 through the lens 20, and the CARS light 19 emitted from the other end of the optical fiber 21 located at a place apart from the entrance is passed through the lens 22 to the spectroscope 23. Be guided.

The CARS light dispersed by the spectroscope 23 is converted into a voltage by the photoelectric converter 24, and a spectrum waveform is obtained by the signal processor 25.

Since this spectral waveform includes the wavelength characteristics of the laser light and the sensitivity characteristics on the light receiving side, it is necessary to correct them, and therefore the non-resonant CARS light is used as the reference light for correction.

In order to obtain the reference light used for the correction of the CARS light, the dichroic filter 17 is removed from the optical path, and the Ar gas 13b is discharged into the space where the two laser lights are condensed to purge the gas molecules. It will be in the state where it was done.

In the above state, in the space where the two laser beams are incident,
Non-resonant CARS light is generated by Ar gas, and the dichroic mirror 15 reflects the non-resonant CARS light containing a slight amount of laser light and makes it enter the optical fiber 21.

Non-resonant CARS light with high intensity is obtained by entering the slight laser light into the end face 21a of the optical fiber 21,
The non-resonant CARS light enters the photoelectric converter 24 through the spectroscope 23 and is converted into an electric signal, and the signal processor 25 obtains the spectral waveform of the non-resonant CARS light as the reference light.

Fig. 3 shows the reference light obtained in this way, which shows the sensitivity curve of the entire device. By taking the intensity ratio of this reference light and CARS light, an accurate CARS spectrum can be obtained. To be

The spectrum waveform thus obtained is shown in FIG. 5, and it is sequentially compared with the spectrum waveform shown in FIG. 4 obtained by theoretical calculation in advance. The temperature at the measuring point is obtained. For example, a curve that is almost the same as the curve in FIG.
By searching from the figure, it is judged to be around 400K.

The dichroic mirror or filter is
A dielectric multilayer film mirror or filter, in which a substance having a low refractive index and a substance having a high refractive index are alternately deposited on the surface of a gas substrate in a thickness corresponding to a wavelength range in which the substance is used.

A dichroic mirror that is formed in this way and that reflects light in a specific wavelength range and transmits light in other wavelength ranges is a dichroic mirror that transmits light in a specific wavelength range and reflects light in other wavelength ranges. The thing to do is a dichroic filter, the former aims at utilization of reflected light, and the latter aims at utilization of transmitted light.

The term dichroic is usually not used alone.

[Problems to be solved by the device]

In the conventional device, the CARS light generated by the gas molecules in the test section where the two laser lights are in focus is superposed on the non-resonant CARS light used as the reference light, which is generated by the fiber end face having the same wavelength band. To get an accurate reference beam, purge the test section with Ar gas,
It was necessary to remove the gas molecules to be measured from the test section, a purge device was required, and it took a long time to measure.

 The present invention is intended to solve the above problems.

[Means for solving the problem]

The gas temperature measuring device of the present invention generates two kinds of laser beams having different wave numbers and measures the difference in wave number between the two laser beams in the space where the gas exists in accordance with the difference in vibration energy level of gas molecules. It condenses and generates CARS light, and the light containing the CARS light is incident on the dichroic mirror to separate the CARS light, and the CARS light is incident on the photoelectric converter through the optical fiber and the spectroscope and is photoelectrically converted. In the gas temperature measuring device that analyzes the gas molecule CARS light by inputting the electric signal into the signal processor and measures the gas temperature from the difference in the spectral waveform, the light reflected by the dichroic mirror and incident on the optical fiber is detected. A dichroic filter for gas molecules, which is provided so that it can be put in and taken out from the optical path, transmits CARS light generated by the gas molecules, and reflects two laser lights, and the two laser lights. It is characterized in that permeated gas molecules and a dichroic filter for reference light for reflecting CARS light generated.

[Action]

In the above, when measuring CARS light generated from gas molecules, with a dichroic filter for gas molecules inserted in the optical path, two lasers are focused in the space where gas molecules are present to generate CARS light. , The dichroic mirror reflects and separates the CARS light, and the CARS light is converted into an electric signal through the optical fiber, the spectroscope, and the photoelectric converter after the remaining laser light is removed by the dichroic filter for gas molecules. Then, a spectrum waveform is obtained by the signal processor.

Next, when obtaining the reference light, the dichroic filter for gas molecules is removed from the optical path, and the dichroic filter for reference light is inserted. The dichroic filter for reference light has a different wavelength band from the dichroic filter for gas molecules, and is designed to reflect only CARS light from gas molecules and transmit two laser lights. In the above state, the CARS light generated from the space where the gas molecules are present is reflected and removed by the reference light dichroic filter, and the remaining slight laser light passes through the reference light dichroic filter to the optical fiber. Incident. Non-resonant CARS light is obtained by entering the above-mentioned slight laser light into the end face of the optical fiber. The spectral waveform of the non-resonant CARS light which is the reference light can be obtained.

The CARS light is corrected by the reference light, the temperature of the gas molecule is measured, the reference light does not include the CARS light because the CARS light from the gas molecule is reflected and removed by the dichroic filter for the reference light, Further, since the non-resonant CARS light with high intensity is obtained from the end face of the optical fiber on which the laser light is incident, the CARS spectrum corrected by the reference light becomes accurate, and the gas temperature with high accuracy can be obtained.

Due to the above, the Ar gas purging device used in the conventional device is unnecessary, and it is not necessary to purge the gas molecules with Ar gas, so it is possible to easily measure the non-resonant CARS light in a short time. Moreover, since the reference light having high intensity and less noise can be obtained, the accuracy of gas temperature measurement can be improved.

〔Example〕

 FIG. 1 shows an embodiment of the present invention.

In the present embodiment shown in FIG. 1, a laser beam 2 output from an excimer laser 1 enters a half mirror 3, and the half mirror 3 reflects a part of the laser beam 2 and transmits the rest and reflects it. The reflected laser light enters and is reflected by the dichroic mirror 9 through the dye laser 5, and the transmitted laser light is reflected by the total reflection mirror 4 and enters the dye laser 6.
The dye laser 6 outputs the Stokes light 8 and enters the total reflection mirror 10 and is reflected. The Stokes light 8 reflected by the total reflection mirror 10 passes through the dichroic mirror 9 and is reflected by the dichroic mirror 9. The nitrogen gas that is combined with the pumping light 7 that has been collected, is condensed at the measurement point 12 of the test section 13 via the lens 11, and is measured.
CARS light is generated, and the CARS light enters the dichroic mirror 15 through the lens 14 together with the laser light. The dichroic mirror 15 transmits most of the laser light and is composed of a part of the laser light and the CARS light. Light 16 is reflected and the same reflected light 16
In the CARS reference light measuring device, which is input to the spectroscope 23 via the lens 20, the optical fiber 21, and the lens 22, is converted into an electric signal by the photoelectric converter 24 and is input to the signal processor 25,
The CARS light reflected by the dichroic mirror 15 and the light 16 composed of a part of the laser light are respectively put in and out of the optical path, the CARS light generated by the nitrogen gas is transmitted, and the pumping light 7 and the Stokes light 8 which are laser lights are reflected. There is provided a dichroic filter 17 for gas molecules, and a dichroic filter 18 for reference light that transmits the pumping light 7 and the Stokes light 8 that are the laser light and reflects the CARS light.

In this example, CARS generated from nitrogen gas molecules
When measuring light, since the CARS light and the two laser lights are the same as the conventional one until they are reflected or transmitted by the dichroic mirror 15, the description of the operation is omitted.

In the above, when measuring CARS light, a dichroic filter 17 for gas molecules is inserted in the optical path, the CARS light reflected from the dichroic mirror 15 and the light 16 consisting of a very small amount of laser light are perpendicular to the optical path. The CARS light entering the dichroic filter 17 provided is transmitted through the filter, and the laser light is reflected and removed.

The separated CARS light 19 is the same as the conventional lens 20,22.
And the optical fiber 21 to the spectroscope 23, and the photoelectric converter 24
Then, the signal is converted into a photoelectric signal and the signal processor 25 obtains a spectral waveform.

Next, when obtaining the reference light, the dichroic filter 17 is removed from the optical path, and instead the dichroic filter 17 is used.
18 is inserted. CARS light generated from the above measurement point 12 and 2
Two laser beams are passed through lens 14 to dichroic mirror
The incident light 15 is split into the reflected light 16 and the transmitted laser light 7 and 8. The light 16 reflected by the dichroic mirror 15 has CARS light and a small amount of laser light 7 and 8, the CARS light is reflected and removed by the dichroic filter 18, and the laser light transmitted through the filter passes through the lens 20. The light is focused on the end face 21a via the light and enters the optical fiber 21.

When the laser light 7, 8 is incident on the optical fiber 21, the non-resonant CARS light generated is proportional to the square of the density of molecules, so the laser light has a high density end face 21 of the optical fiber 21.
The non-resonant CARS light is generated by a, guided to the spectroscope 23, photoelectrically converted by the photoelectric converter 24, and the spectral waveform of the reference light is obtained by the signal processor 25.

The above reference light is CARS generated from the gas molecule to be measured.
Since it does not contain light and has a high intensity, the CARS spectrum with corrected wavelength characteristics and sensitivity characteristics obtained by taking the intensity ratio with CARS light becomes more accurate, and by comparing it with the theoretical spectrum waveform, measurement point 12 The temperature can be obtained with high accuracy.

Due to the above, since the Ar gas purging device used in the conventional device is not required, the reference light can be easily measured in a short time, and the reference light with high intensity and less noise can be obtained. It has become possible to improve the accuracy of measurement.

2 shows the wavelength bands of the dichroic filters 17 and 18 and their effects. The dichroic filter 17 cuts the pumping light (wavelength 480 nm) and the Stokes light (wavelength 540 nm),
Cuts the CARS light (430 nm).

[Effect of device]

The CARS reference light measuring device of the present invention, when obtaining a reference light,
The dichroic filter that transmits the CARS light from the space where the two laser beams are condensed and the CARS light that is provided in the optical path of the reflected light of the dichroic mirror that has entered the laser beam are exchanged with the dichroic filter that transmits the laser beam. Non-resonant CARS with a small amount of laser light incident on the end face of the optical fiber
By generating the light, the Ar gas purging device used in the conventional device is unnecessary, and the reference light can be easily measured in a short time, and the reference light with high intensity and less noise can be obtained. It has become possible to improve the accuracy of gas temperature measurement.

[Brief description of drawings]

FIG. 1 is an explanatory view of an embodiment of the present invention, FIG. 2 is a wavelength band diagram of two types of dichroic filters according to the above embodiment, FIG. 3 is a spectrum diagram of reference light, and FIG. 4 is a theoretical calculation. FIG. 5 is a spectrum diagram of CARS light obtained by the above, FIG. 5 is a spectrum diagram of CARS light of N ₂ gas obtained by an experiment, and FIG. 6 is an explanatory view of a conventional device. 1 ... Excimer laser, 2 ... Excimer laser light, 3 ...
... Half mirror, 4 ... Total reflection mirror, 5 ... Dye laser, 6 ... Dye laser, 7 ... Pumping light, 8 ... Stokes light, 9 ... Dichroic mirror, 10 ... Total reflection mirror, 11 ... … Lens, 12 …… Measurement point, 13 …… Test section, 13a …… A _r Gas injection nozzle, 13b …… A _r Gas, 14 …… Lens, 15 …… Dichroic mirror, 16…
… Reflected light, 17 …… Dichroic filter, 18 …… Dichroic filter, 19 …… CARS light, 20 …… Lens, 21
…… Optical fiber, 21a …… End face, 22 …… Lens, 23 ……
Spectrometer, 24 ... Photoelectric converter, 25 ... Signal processor.

Claims (1)

(57) [Scope of utility model registration request] 1. A curse for generating two kinds of laser beams having different wave numbers and converging in a space where the gas exists in accordance with a vibration energy level difference of gas molecules for measuring a wave number difference between the two laser beams. Light is generated, the light containing the curse light is incident on the dichroic mirror to separate the curse light, the curse light is incident on the photoelectric converter through the optical fiber and the spectroscope, and the photoelectrically converted electrical signal is generated. In the gas temperature measuring device, which inputs the signal to the signal processor, analyzes the spectrum of the gas molecule curs light, and measures the gas temperature from the difference in the spectral waveform, puts it in and out of the optical path of the light reflected by the dichroic mirror and incident on the optical fiber. A dichroic filter for gas molecules, which is provided so as to transmit the curse light generated by the gas molecules and reflects two laser beams; and the two lasers. The gas temperature measuring device being characterized in that a dichroic filter for reference light for reflecting curse light gas molecules through the light is generated.