JP2000266673A - Measuring apparatus for two-dimensional distribution of concentration in flame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make measurable the two-dimensional distribution of the absolute concentration of a trace component in a flame. SOLUTION: In this measuring apparatus, a flame 4 is irradiated with a laser beam 1 which is made sheetlike. Then, generated induced fluorescence is photographed by a camera 9 from the side. Then, the two-dimensional distribution of the relative concentration of a trace component in the flame is measured. Then, a transmitted laser beam is measured by a power meter 19. Then, the absorbed energy amount of the laser beam 1 in the flame 4 is measured. Thereby, the two-dimensional distribution of the absolute concentration of the trace component in the flame 4 is calculated on the basis of its measured value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device for measuring a two-dimensional concentration distribution of trace components such as radicals, molecules, atoms and the like generated in a flame.

[0002]

2. Description of the Related Art It is indispensable to measure combustion physics and stoichiometry and analyze combustion phenomena in order to improve combustion technologies such as improving the efficiency of combustors, reducing pollution, and treating emissions. is there. Since the measurement using a laser is a non-contact measurement method, the measurement is performed without disturbing the field to be measured.
Visualization of dimensional distribution is possible. In addition, time-resolved measurement is possible, and unsteady phenomena can be measured.

[0003] Among the measurement methods using a laser, a laser induced fluorescence (LIF) method is used.
Is particularly excellent as a method for measuring the distribution and concentration of specific chemical species generated in the combustion process.

[0004] The LIF method irradiates molecules with laser light and observes the generated fluorescence. Electrons in a molecule have a quantized energy level, and when light having energy equal to the difference between the energy levels is incident on the molecule, the molecule absorbs the energy of the light and transitions to an excited state. When the excited electron returns to a lower energy level again, its energy 6
Is emitted as fluorescence. Since the energy gap differs depending on the type of molecule, the excitation light and the fluorescent light have a wavelength unique to the molecule. Therefore, by irradiating the flame with laser light of a specific wavelength and capturing the corresponding fluorescence of the specific wavelength with a camera, the relative two-dimensional concentration distribution of radicals and molecules such as OH, CH and NO in the flame can be measured. can do.

FIG. 2 is a conceptual diagram of a measuring device used in the LIF method. In the drawing, reference numeral 1 denotes a laser beam, and 2 denotes a beam expanding lens. Reference numeral 3 denotes a cylindrical lens for forming a laser beam into a sheet, and reference numeral 4 denotes a flame. 5
Denotes a light shielding plate, 6 denotes an image forming lens, and 7 denotes a band pass filter. 8 is an image intensifier,
9 is a CCD camera, 10 is an image storage device, and 11 is a computer. As shown in the figure, a laser beam 1 is expanded by a lens 2 and is made into a sheet shape by a cylindrical lens 3. By irradiating the flame 4 with a sheet-like laser beam to excite one section of the molecule group, and observing the intensity of fluorescence emitted from the cross section, the relative two-dimensional concentration distribution of this molecule is measured. can do.

[0006]

When an excited molecule returns to its original state after releasing energy, the following three types of energy relaxation processes are performed. That is, a radiative transition process observed as fluorescence (conversion to light energy: A), collision deactivation due to collision with another molecule (conversion to heat and translational energy: Q), dissociation of the molecule itself (chemical energy) To P :). The integrated intensity S _{F of the} fluorescence emitted after the target molecule existing at the vibration / rotation energy level E in the ground state absorbs the laser light of intensity I ₀ is expressed by the following equation. S _F = C (Ω / 4π) N ₀ f (T) I ₀ A / (A + Q +
P) C: constant Ω: solid angle of light collection N ₀ : molecular number density f (T): Boltzmann distribution constant in base state E,
Function of absolute temperature T A: Einstein coefficient of spontaneous emission (fluorescence) Q: Collision deactivation rate constant P: Predissociation rate constant A / (A + Q + P) is equivalent to the ratio of "molecule emitting fluorescence / excited molecule" However, if this value can be determined, the concentration can be quantified from the fluorescence intensity. However, Q depends on the density (pressure) and temperature of the measurement field, and it is difficult to determine the value accurately in a field having a strong reaction such as a flame. Predissociation does not occur unless the molecule is excited to a high excited level, so P = 0 is usually the case. If dissociation does not occur, P =
0, Q≫A, so A / (A + Q + P)）
A / Q can be approximated. Although it is difficult to quantify A / Q because Q is affected by a change in temperature or the like, it is easily used as a qualitative measurement.

As described above, the LIF method is convenient for measuring the relative two-dimensional concentration distribution of radicals and molecules,
An absolute (quantitative) two-dimensional concentration distribution cannot be measured, and the purpose may not always be achieved depending on the purpose of the measurement.

The present invention has been devised in view of the above-mentioned problems of the prior art, and has a two-dimensional concentration in a flame capable of measuring an absolute (quantitative) two-dimensional concentration distribution of trace components such as radicals in the flame. It is an object to provide a distribution measurement device.

[0009]

In order to achieve the above object, a two-dimensional concentration distribution measuring apparatus in a flame according to the present invention irradiates the flame with a laser beam in a sheet form, and generates induced fluorescence generated from a side by a camera. Photographs are used to measure the relative two-dimensional concentration distribution of trace components in the flame, and the transmitted laser light is measured with a power meter to measure the amount of energy absorbed by the laser in the flame. Is used to calculate the absolute two-dimensional concentration distribution of the trace components of the above.

Next, the operation of the present invention will be described. A sheet of laser light having a wavelength suitable for exciting a trace component to be measured is applied to the flame. When the excited trace component returns to a lower energy level again, it emits fluorescence inherent in the trace component. Since the emitted laser light is in the form of a sheet, the emitted fluorescent light is also in the form of a plane. By photographing the emitted fluorescent light with a camera, the relative two-dimensional concentration distribution of the trace component can be measured.

On the other hand, the light energy of the laser light passing through the flame is measured by a power meter. The light energy of the emitted laser is the light energy received by the power meter without passing through the flame, so if you take the ratio with the measured value of the power meter when passing through the flame, the light energy absorbed in the flame Can be grasped quantitatively. On the other hand, a trace component of a known concentration is present in the optical path of the laser light,
If the relationship between the concentration and the absorbed energy is obtained in advance and graphed, the concentration of the sum of the trace components existing in the optical path when the laser light actually passes through the flame can be determined. Therefore, if the relative two-dimensional concentration distribution measured by the LIF and the output of the power meter are input to a computer and calculated, the absolute (quantitative) 2 of the trace components in the flame can be obtained.
A dimensional density distribution can be calculated.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram of a device for measuring a two-dimensional concentration distribution in a flame according to the present invention. In FIG. 1, the same reference numerals are given to the same parts as those described in FIG. 2 as the related art, and the overlapping description will be omitted. In FIG. 1, reference numeral 18 denotes a LIF device, 19 denotes a power meter device for measuring the energy of laser light, and 20 denotes a computer which receives information from both to perform calculations. L
The IF device 18 is, as described above, the laser generator 1
2 and a CCD camera 9. Laser generator 12
When measuring radicals such as NO, OH, and CH, a laser beam in the ultraviolet region and a wavelength variable dye laser, titanium sapphire laser, or the like is suitable. The laser beam 1 from the laser generator 12 is formed into a sheet shape via the beam expanding lens 2 and the cylindrical lens 3, and is applied to the flame 4. Due to this irradiation, fluorescent light is emitted from the flame 4 in a planar manner. In addition, 16 is a control device, and 17 is a display.

The power meter device 19 has a condenser lens 13, a light receiving element 14, and a display device 15, as shown in FIG. If the ratio of the measured value of the power meter 19 when passing through the flame 4 to the measured value of the power meter 19 when there is no flame 4 is determined, the absorption energy of the laser beam absorbed in the flame is determined. By inputting information from the CCD camera 9 and information from the power meter 15 to the computer 20 and performing calculations, an absolute (quantitative) two-dimensional concentration distribution of a trace component can be calculated.

Next, the operation of the present embodiment will be described. The flame 4 is irradiated with a laser beam 1 having a wavelength suitable for exciting a trace component to be measured in a sheet shape. When the trace component excited by the irradiation returns to a low energy level again, it emits fluorescence unique to the trace component. Table 1 shows the relationship between the type of radical, the excitation wavelength and the detection wavelength (the wavelength of emitted fluorescence) when the trace component is a radical.

[0015]

[Table 1]

Since the laser beam 1 to be irradiated is sheet-shaped,
The emitted fluorescent light is also planar, and by capturing the fluorescent light with the CCD camera 9, the relative two-dimensional concentration distribution of the trace component can be measured.

On the other hand, the light energy of the laser beam 1 passing through the flame 4 is measured by a power meter 19. The light energy of the emitted laser is the light energy when received by the power meter 19 without passing through the flame 4, and is absorbed in the flame 4 by taking the ratio with the measured value of the power meter 19 when passing through the flame 4. Light energy can be grasped quantitatively. On the other hand, if a trace component having a known concentration is present in the optical path of the laser beam 1 and the relationship between the concentration and the absorption energy is plotted in advance, the laser beam 1 actually
When passing through the inside, the concentration of the sum of the trace components existing in the middle of the optical path is determined. Therefore, if the relative two-dimensional concentration distribution measured by the LIF 18 and the output of the power meter 19 are input to the computer 20 for calculation, the absolute (quantitative) two-dimensional concentration distribution of the trace components in the flame can be calculated. Can be.

The present invention is not limited to the embodiments described above, and various changes can be made without departing from the gist of the invention. For example, the camera 9 may be a MOS type instead of a CCD type.

[0019]

As described above, the apparatus for measuring the two-dimensional concentration distribution in a flame according to the present invention measures the energy of a transmitted laser beam with a power meter in addition to a normal LIF apparatus and is absorbed in the flame. The total amount of light energy is measured and LIF
Since the information from the power meter and the information from the power meter are input to the computer for calculation, there is an excellent effect that an absolute (quantitative) two-dimensional concentration distribution in the flame can be calculated.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a device for measuring a two-dimensional concentration distribution in a flame according to the present invention.

FIG. 2 is a conceptual diagram of a LIF device.

[Explanation of symbols]

 Reference Signs List 1 laser beam 4 flame 9 CCD camera 19 power meter device 20 computer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G043 AA01 BA12 BA17 CA01 DA01 DA08 EA01 EA10 EA13 FA01 FA07 GA07 GA11 GB07 HA01 JA08 KA05 KA09 LA03 LA07 2G059 AA01 BB20 CC20 EE01 FF01 GG01 HH03 JJ11 KK01 KK04 PP

Claims (1)

[Claims] 1. A flame is irradiated with a laser beam in a sheet form, and the induced fluorescence generated is photographed by a camera from the side to measure a relative two-dimensional concentration distribution of a trace component in the flame and transmit a laser beam. Is measured with a power meter to measure the amount of energy absorbed by the laser in the flame, and the absolute two-dimensional concentration distribution of the trace components in the flame is calculated from these measured values. Measurement device for concentration distribution.