JP5590875B2 - Flow rate measuring device and flow velocity measuring device - Google Patents

Description

  The present invention relates to a flow rate measuring device that measures the flow rate of a fluid and a flow rate measuring device that measures the flow rate of a fluid.

  Various methods have been proposed for measuring the flow rate of the gas flowing in the flow path. For example, Patent Document 1 describes a differential pressure flow meter in which an orifice plate is disposed in a pipe and the flow rate of fluid flowing in the pipe is measured by the differential pressure in the pipe before and after the orifice plate.

  Further, in Patent Document 2, an ultrasonic transmitting element and a receiving element are installed to face each other at an angle in the fluid flow direction, and a different first method is used in an apparatus for measuring the fluid flow rate from the ultrasonic propagation time. Means for oscillating an ultrasonic wave of a sine wave signal having a frequency component composed of a frequency and a second frequency, means for obtaining a phase difference between the first and second frequency components of the ultrasonic wave propagated in the fluid, and There is described a flow rate measuring device that includes means for calculating the propagation time of an ultrasonic wave from a phase difference and obtains a flow rate by calculating the flow velocity of the fluid from the propagation time of the ultrasonic wave.

Japanese Patent Laid-Open No. 06-174510 JP 2009-222534 A

  In the apparatus for measuring the flow rate by the differential pressure described in Patent Document 1, since it is necessary to provide an orifice inside the pipe, there is a restriction on the object of use, such as the need to secure a certain straight pipe part before and after. Arise. Moreover, in the flow rate measuring apparatus using the ultrasonic wave described in Patent Document 2, the ultrasonic wave transmission source and the detector are directly attached to the pipe. Therefore, for example, when the gas flowing through the pipe is high temperature, it cannot be used. Alternatively, it is necessary to use a mechanism that can be used even at high temperatures. In addition, both methods of Patent Document 1 and Patent Document 2 require a certain amount of time for measurement, and there is a problem that there is a limit to improvement of responsiveness. Moreover, although the flow velocity can also be measured based on the relationship between the pipe diameter and the flow rate, there is a similar problem.

  The present invention has been made in view of the above, and it is an object of the present invention to provide a flow rate measuring device and a flow velocity measuring device capable of measuring with high responsiveness and capable of measuring a flow rate even in a severe environment. To do.

  In order to solve the above-described problems and achieve the object, the present invention includes a main pipe that is open at both ends and can be connected to a flow path for flowing a fluid, a side connected to the main pipe, and a side connected to the main pipe. An incident tube having a window portion through which light can pass at the opposite end, and a window portion through which light can pass at the end opposite to the side connected to the main tube. A measurement cell configured by a first purge fluid supply pipe connected to the incident pipe, a purge fluid supply unit for supplying a purge fluid to the first purge fluid supply pipe of the measurement cell, A light emitting unit that makes a laser beam incident on the incident tube, and a laser beam that is incident from the incident tube, passes through the measurement cell, and is emitted from the emission tube, and outputs the received light amount as a light reception signal. Based on the light receiving unit and the light receiving signal output from the light receiving unit. There are characterized by having a calculation unit for calculating the flow rate of the fluid flowing through the measuring cell, and a control unit for controlling the operation of each unit, the.

  Thereby, it is possible to measure with high responsiveness and to measure the flow rate even in a severe environment.

  Further, it is preferable that the calculation unit demodulates a light reception signal received by the light reception unit at one frequency, and calculates the flow rate of the fluid based on the magnitude of fluctuation of the demodulated signal. By using the fluctuation of the signal demodulated at one frequency, the flow rate can be measured with a simple configuration.

  The calculation unit may demodulate the light reception signal received by the light reception unit at two different frequencies, and calculate the flow rate of the fluid based on the magnitude of signal fluctuation at the two demodulated frequencies. preferable. Thereby, the flow rate can be measured with higher accuracy.

  The calculating unit may demodulate the received light signal received by the light receiving unit at a plurality of different frequencies, and calculate the flow rate of the fluid based on the magnitude of signal fluctuation at the demodulated frequencies. preferable. Thereby, the flow rate can be measured with higher accuracy.

  In addition, it is preferable that the calculation unit stores a relationship between a fluctuation and a flow rate calculated in advance, and calculates the flow rate of the fluid based on the relationship and the magnitude of the fluctuation. Thereby, the flow rate can be measured more easily.

  Further, the calculation unit stores a relationship between the fluctuation and the flow rate of the fluid for each flow rate of the purge fluid flowing through the incident pipe, and based on the flow rate of the purge fluid flowing through the incident pipe and the fluctuation. It is preferable to calculate the flow rate of the fluid. Thereby, the flow rate can be measured with higher accuracy.

  Further, the control unit calculates a flow rate of the purge fluid having a large variation amount in a region including the fluid flow rate calculated by the calculation unit, and based on a calculation result, the control unit calculates the purge fluid flow rate from the purge fluid supply unit. It is preferable to adjust the flow rate of the purge fluid supplied to the first purge fluid supply pipe. Thereby, the flow rate can be measured with higher accuracy.

  Further, the calculation unit further includes a concentration of a substance to be measured of a waste fluid flowing through the measurement cell based on the intensity of the laser beam output from the light emitting unit and the intensity of the laser beam received by the light receiving unit. Is also preferably calculated. Thereby, more information can be acquired about the flowing fluid.

  The light receiving unit includes a plurality of light receiving elements arranged adjacent to each other, and outputs the amount of light received by each light receiving element as a light receiving signal, and the calculating unit receives a light receiving signal transmitted from each light receiving element. It is preferable to calculate the flow rate of the fluid based on the comparison of strength. Even with this method, the flow rate can be measured with high accuracy.

  Further, the calculation unit calculates the arrival position of the laser beam based on a comparison of the intensity of the received light signal sent from each light receiving element, and based on the deviation between the arrival position and the reference position, It is preferable to calculate the flow rate. Thereby, the displacement of the laser beam can be detected, and the flow rate can be measured.

  Further, the calculation unit is configured to determine a substance to be measured of the exhaust fluid flowing through the measurement cell based on the total amount of the received light signal transmitted from each light receiving element and the intensity of the laser light received by the light receiving unit. It is preferable to calculate the concentration. Thereby, more information can be acquired about the flowing fluid.

  In addition, the measurement cell includes a turbulent flow generation unit that turbulently flows the air in the vicinity of the incident tube on the upstream side of the incident tube in the fluid flow direction and in the vicinity of the incident tube. It is preferable to have. Thereby, the change of the received light signal with respect to the change of the flow rate can be increased, and the flow rate can be measured with higher accuracy.

  Furthermore, it is preferable that a second purge fluid supply pipe connected to the emission pipe is provided, and the purge fluid supply section supplies the purge fluid also to the second purge fluid supply pipe. Thereby, possibility that the window part in an emission tube will become dirty can be reduced.

  It is preferable that the calculation unit further measures a flow velocity of the fluid flowing through the main pipe of the measurement cell based on a light reception signal output from the light reception unit. Thereby, more information on the fluid flowing through the measurement cell can be acquired.

  The fluid is preferably a gas.

  In order to solve the above-described problems and achieve the object, the present invention provides an incident tube in which one end portion is an opening facing a measurement region and a window portion through which light can pass is formed at the opposite end portion. An exit tube having one end facing the incident tube and facing the measurement region, and having a window portion through which light can pass at the opposite end, connected to the incident tube. A measurement cell constituted by a first purge fluid supply pipe, a purge fluid supply part for supplying a purge fluid to the first purge fluid supply pipe of the measurement cell, and a light emitting part for causing laser light to enter the incident pipe A light receiving unit that receives the laser light that is incident from the incident tube, passes through the measurement region, and is emitted from the emitting tube, and outputs the received light amount as a light reception signal; and a light reception that is output from the light receiving unit Based on the signal, the flow through the measurement area A calculation unit for calculating the flow rate, characterized by having a control unit for controlling the operation of each section.

  Thereby, it is possible to measure with high responsiveness and to measure the flow velocity even in a severe environment.

  The measurement cell includes a main tube that is connected to one end of the incident tube and one end of the output tube and through which a fluid to be measured flows, and the measurement region is a part of the main tube. It is preferable that Thereby, the flow of a measuring object can be restrained and it can measure with higher precision.

  The fluid is preferably a gas.

  The flow rate measuring apparatus according to the present invention can measure with high responsiveness, and has an effect that the flow rate can be measured even in a severe environment.

FIG. 1 is a schematic diagram showing a schematic configuration of an embodiment of a flow rate measuring device of the present invention. FIG. 2 is an enlarged schematic view showing a part of the measurement cell of the flow rate measuring device shown in FIG. 1 in an enlarged manner. FIG. 3 is an explanatory diagram for explaining the path of the laser beam. FIG. 4 is a graph showing the relationship between frequency and noise. FIG. 5 is a graph showing the relationship between the exhaust gas flow rate and noise. FIG. 6 is a graph showing the relationship between the exhaust gas flow rate and noise. FIG. 7 is a graph showing the relationship between frequency and noise. FIG. 8A is a schematic diagram illustrating a schematic configuration of a part of another embodiment of the flow rate measuring device. FIG. 8-2 is a partially enlarged view of FIG. FIG. 9A is a schematic diagram illustrating a schematic configuration of a light receiving unit according to another embodiment of the flow rate measuring device. FIG. 9B is an explanatory diagram for explaining the operation of the flow rate measuring device illustrated in FIG. FIG. 9C is an explanatory diagram for explaining the operation of the flow rate measuring device illustrated in FIG. FIG. 10 is a schematic diagram illustrating a schematic configuration of another example of the light receiving unit. FIG. 11 is a schematic diagram showing a schematic configuration of an embodiment of the flow velocity measuring device of the present invention. FIG. 12A is an enlarged schematic diagram illustrating a part of the measurement cell of the flow velocity measuring device illustrated in FIG. 11 in an enlarged manner. 12-2 is a schematic view of the measurement cell of the flow velocity measuring device shown in FIG. 11 as viewed from a direction parallel to the exhaust gas flow direction.

  Hereinafter, an embodiment of a flow rate measuring device and a flow rate measuring device according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. The flow rate measuring device can measure the flow rate and flow velocity of various gases (gas) and fluid such as liquid flowing in the flow path. For example, an exhaust gas purification device may be attached to a diesel engine, and the exhaust gas flow rate discharged from the diesel engine may be measured. The engine that discharges exhaust gas, that is, a device that discharges (supplies) the gas to be measured is not limited to this, and can be used for various internal combustion engines such as a gasoline engine and a gas turbine. Examples of the device having an internal combustion engine include various devices such as vehicles, ships, and generators. Furthermore, combustion equipment such as a garbage incinerator and boiler, and a high temperature and flow rate, a flow rate with fluctuations in flow velocity, a flow rate of exhaust gas discharged from a flow velocity measurement target, and a flow velocity can also be measured. In the following embodiments, a case where the flow rate of exhaust gas flowing through a pipe is measured will be described. Moreover, although demonstrated later, the flow velocity which flows through piping is also measurable with the apparatus structure of the flow volume measuring apparatus demonstrated by the following embodiment.

  FIG. 1 is a schematic diagram showing a schematic configuration of an embodiment of a flow rate measuring device of the present invention. FIG. 2 is an enlarged schematic view showing a part of the measurement cell of the flow rate measuring device shown in FIG. As shown in FIG. 1, the flow rate measuring device 10 includes a measurement cell 12, a measurement unit 14, and a purge gas supply unit 16. Here, the flow rate measuring device 10 is provided between the pipe 6 and the pipe 8 through which the exhaust gas A flows. Further, the exhaust gas A is supplied from the upstream side of the pipe 6, passes through the pipe 6, the flow rate measuring device 10, and the pipe 8, and is discharged downstream from the pipe 8. An exhaust gas generator (supply device) is disposed upstream of the pipe 6.

  The measurement cell 12 basically includes a main tube 20, an incident tube 22, and an exit tube 24. Further, the incident tube 22 is provided with a window 26 and a purge gas supply tube 30, and the emission tube 24 is provided with a window 28 and a purge gas supply tube 32. The main pipe 20 is a tubular tubular member, and has one end connected to the pipe 6 and the other end connected to the pipe 8. That is, the main pipe 20 is disposed at a position that becomes a part of the flow path through which the exhaust gas A flows. Thereby, the exhaust gas A flows in the order of the pipe 6, the main pipe 20, and the pipe 8. Further, the exhaust gas flowing through the pipe 6 basically flows through the main pipe 20.

  The incident tube 22 is a tubular member, and has one end connected to the main tube 20. Further, in the main tube 20, the connection portion with the incident tube 22 is an opening having substantially the same shape as the opening (end opening) of the incident tube 22. That is, the incident tube 22 is connected to the main tube 20 in a state where air can flow. A window 26 is provided at the other end of the incident tube 22 and is sealed by the window 26. The window 26 is made of a light transmitting member such as transparent glass or resin. Thereby, the incident tube 22 is in a state where the end portion where the window 26 is provided is in a state where air is not circulated and light can pass therethrough.

  As shown in FIGS. 1 and 2, the incident tube 22 has an area of an opening at the end of the window 26 (that is, an opening closed by the window 26) and an end of the main tube 20 (that is, the main tube). The area of the opening connected to 20 is substantially the same cylindrical shape. In addition, the shape of the incident tube 22 is not limited to a cylindrical shape, and may be a cylindrical shape that allows air and light to pass therethrough, and may be various shapes. For example, the cross section may be a square, a polygon, an ellipse, or an asymmetric curved surface. Moreover, the shape of the cross section of a cylindrical shape and the shape where a diameter changes with positions may be sufficient. In addition, it is preferable that the incident tube 22 has a shape in which a purge gas described later flows stably.

  Further, a purge gas supply pipe 30 is connected to the incident pipe 22. As shown in FIG. 2, the purge gas supply pipe 30 is disposed between an end portion where the window 26 is sealed and an end portion connected to the main pipe 20. The purge gas supply pipe 30 guides the purge gas supplied from the purge gas supply means 16 to the incident pipe 22. Further, the purge gas supply pipe 30 is inclined at a portion that becomes a purge gas ejection port toward the window 26 side.

  The exit tube 24 is a tubular member having substantially the same shape as the entrance tube 22. One end of the exit tube 24 is connected to the main tube 20, and a window 28 is provided at the other end of the exit tube 24. The exit tube 24 is also in a state where air can flow through the main tube 20, and an end portion provided with the window 28 is in a state where air does not flow and light can pass therethrough. Further, the emission tube 24 is disposed at a position where the central axis is substantially the same as the central axis of the incident tube 22. That is, the entrance tube 22 and the exit tube 24 are disposed at positions facing the main tube 20.

  The exit tube 24 also has an area of an opening at the end on the window 28 side (that is, an opening closed by the window 28) and an end portion on the main tube 20 side (that is, a portion connected to the main tube 20). The area of the opening) is substantially the same cylindrical shape. The shape of the emission tube 24 is not limited to a cylindrical shape, and may be any shape as long as it is a cylindrical shape that allows air and light to pass therethrough. For example, the cross section may be a square, a polygon, an ellipse, or an asymmetric curved surface. Moreover, the shape of the cross section of a cylindrical shape and the shape where a diameter changes with positions may be sufficient. In addition, it is preferable that the emission tube 24 also has a shape in which a purge gas described later flows stably.

  A purge gas supply pipe 32 is connected between the end of the emission pipe 24 where the window 28 is sealed and the end connected to the main pipe 20. The purge gas supply pipe 32 guides the purge gas supplied from the purge gas supply means 16 to the emission pipe 24. The purge gas supply pipe 32 also has a shape in which the outlet port faces the window 28 side.

  Next, the measuring unit 14 includes a light emitting unit 40, an optical fiber 42, a light receiving unit 44, a light source driver 46, a calculating unit 48, and a control unit 50.

  The light emitting unit 40 is a light emitting element that emits laser light having a predetermined wavelength. The optical fiber 42 guides the laser light output from the light emitting unit 40 and causes the laser light to enter the measurement cell 12 through the window 26.

  The light receiving unit 44 is a light receiving unit that receives the laser light that passes through the inside of the main tube 20 of the measurement cell 12 and is output from the window 28 of the emission tube 24. The light receiving unit 44 includes, for example, a photodetector such as a photodiode (PD), receives the laser beam by the photodetector, and detects the intensity of the light. The light receiving unit 44 sends the intensity (light quantity) of the received laser light as a light reception signal to the calculation unit 48.

  The light source driver 46 has a function of controlling the driving of the light emitting unit 40, and adjusts the wavelength and intensity of the laser light output from the light emitting unit 40 by adjusting the current and voltage supplied to the light emitting unit 40. The light source driver 46 is controlled by the control unit 50.

  The calculation unit 48 calculates the flow rate of the exhaust gas flowing through the measurement cell 20 based on the intensity signal (light reception signal) of the laser beam received by the light receiving unit 44. The calculation method will be described later.

  The control unit 50 has a control function for controlling the operation of each unit, and controls the operation of each unit as necessary. Note that the control unit 50 controls not only the control of the measuring means 14 but also the overall operation of the flow rate measuring device 10. That is, the control unit 50 is a control unit that controls the operation of the flow measurement device 10.

  The purge gas supply means 16 includes a pipe 51, a pump 52, a dryer 54, and a flow meter 56, and supplies a predetermined flow rate of air to the purge gas supply pipes 30 and 32 of the measurement cell 12. In the present embodiment, air is supplied, but nitrogen or the like may be supplied as a purge gas using a cylinder or the like.

  The pipe 51 is connected to the purge gas supply pipes 30 and 32. Further, a pump 52, a dryer 54, and a flow meter 56 are disposed in the pipe 51 in order from the side farthest from the purge gas supply pipes 30 and 32 (upstream of the air flow). The pump 52 supplies air to the purge gas supply pipes 30 and 32 by supplying air to the pipe 51. The operation of the pump 52 is controlled by the control unit 50.

  The dryer 54 is a drying mechanism that dries the air flowing through the pipe 51. As the dryer 54, it is sufficient if moisture contained in the air can be reduced, and various moisture absorption mechanisms and moisture absorption materials can be used.

  The flow meter 56 measures the amount of air flowing through the pipe 51, that is, the flow rate. The flow meter 56 sends information on the measured flow rate to the control unit 50. In addition, since the air sent from the pump 52 basically passes through the pipe 51, the flow rate is stable. Therefore, various commonly used flow meters can be used.

  The purge gas supply means 16 can control the amount of air flowing through the pipe 51 by the control unit 50 controlling the flow rate of the purge gas based on the measurement result of the flow meter 56, and enters the purge gas supply pipe 30. The amount of air supplied to the tube 22, the flow rate, and the amount of air supplied from the purge gas supply tube 32 to the emission tube 24 can be set to a predetermined amount. Moreover, the possibility of moisture adhering to the flow meter 56 can be reduced by drying the air with the dryer 54. The flow rate measuring device 10 is configured as described above.

  Next, a method for measuring the flow rate by the flow rate measuring device 10 will be described. First, when the measuring means 14 of the flow rate measuring device 10 emits laser light from the light emitting unit 40, the emitted laser light L is emitted from the optical fiber 42, the window 26, the incident tube 22, the main tube 20, the output tube 24, and the window. Passes in the order of 28 and enters the light receiving unit 44. At this time, the flow rate measuring apparatus 10 supplies the purge gas G from the purge gas supply pipe 30 to the incident pipe 22 and the purge gas G from the purge gas supply pipe 32 to the emission pipe 24 by the purge gas supply means 16. Thereby, it is possible to suppress the exhaust gas from entering the entrance tube 22 and the exit tube 24, and to prevent the fine particles contained in the exhaust gas from adhering to the windows 26 and 28.

  Here, the purge gas G supplied by the purge gas supply means 16 and the exhaust gas A flowing through the main pipe 20 have different air properties, specifically, gas temperatures. Therefore, as shown in FIG. 2, a temperature boundary layer 80 is formed in a region where the purge gas G supplied from the purge gas supply means 16 and reaches the main pipe 20 through the incident pipe 22 and the exhaust gas A flowing through the main pipe 20 are mixed. The present inventors have found that this is done. Further, the temperature of the purge gas G and the exhaust gas A are different from each other with the temperature boundary layer 80 as a boundary, so that the refractive index becomes different.

  Therefore, as shown in FIG. 3, the laser light L is refracted by passing through the temperature boundary layer 80. Here, FIG. 3 is an explanatory diagram for explaining the path of the laser beam. For example, as shown in FIG. 3, when it can be assumed that the temperature boundary layer 80 is inclined by θ1 with respect to the traveling direction of the laser light L, the temperature boundary layer 80 is passed through the temperature boundary layer 80 to The angle formed is the laser light L with θ2. Thereby, the traveling direction of the light changes by the difference between θ1 and θ2, and the arrival position changes.

  Here, the temperature boundary layer 80 is unstable. Therefore, the angle of the layer that can be regarded as the temperature boundary layer 80 changes with time, and the arrival position of the laser light L also changes with time. When the arrival position changes in this way, the position at which the light receiving unit receives the laser light changes. In other words, the measurement condition changes. This change in the arrival position of the laser beam L appears as noise (signal fluctuation) in the result of demodulating the received signal of the light receiving unit 44. Note that the fluctuation of the signal becomes noise when other physical property values are measured, but in the present invention, the fluctuation of the signal becomes a value to be measured for obtaining the flow rate. In the description of the present embodiment, signal fluctuation is referred to as noise for convenience.

  Here, as a result of intensive studies on the noise, the present inventors have found that there is a correlation between the noise and the flow rate flowing through the main pipe 20. The flow rate measuring device 10 calculates the flow rate based on the relationship. Details will be described below.

First, the exhaust gas flow rate was changed to various values. For each exhaust gas flow rate, the received light signal was demodulated at various frequencies, and the relationship between the demodulated frequency and the demodulated noise was measured. Further, in this measurement, when the flow rate of the exhaust gas 0 (i.e. if no flow of exhaust gas), when a ^61m 3 / h, when the 116m ³ / h, when the 160m ³ / h, 199m ³ / In the case of h, the relationship between the demodulated frequency and noise in the case of 258 m ³ / h was measured. In addition, these measurements were performed on the same conditions except the point which changed the flow volume of waste gas. The measurement results are shown in FIG. FIG. 4 is a graph showing the relationship between frequency and noise. In FIG. 4, the vertical axis represents noise (dB) and the horizontal axis represents frequency (kHz). The frequency is a frequency obtained by demodulating the received light signal detected by the light receiving unit. As shown in FIG. 4, it can be seen that the magnitude of the generated noise varies with the flow rate of the exhaust gas. In addition, basically, it can be seen that the noise increases as the flow rate of the exhaust gas increases.

Next, based on this measurement result, the relationship between the noise and the exhaust gas flow rate when the demodulation frequency was 200 kHz was calculated. The calculation results are shown in FIG. Here, FIG. 5 is a graph showing the relationship between the exhaust gas flow rate and noise. In FIG. 5, the vertical axis represents noise (σ (A) / I (× 10 ⁻⁶ / m)), and the horizontal axis represents the exhaust gas flow rate (Nm ³ / h). As shown in FIG. 5, at the demodulation frequency of 200 kHz, the magnitude of noise changes according to the exhaust gas flow rate.

  The flow measurement device 10 calculates the flow rate from the magnitude of noise using the above relationship. Specifically, the relationship between the magnitude of noise and the exhaust gas flow rate as shown in FIG. 5 is calculated in advance by experiment and measurement, and stored in the calculation unit 48. The calculation unit 48 demodulates the light reception signal transmitted from the light reception unit 44 at a frequency of 200 kHz, and detects the noise level of the demodulated result (signal). Thereafter, the exhaust gas flow rate is calculated based on the detected noise magnitude and the relationship between the stored noise magnitude and the exhaust gas flow rate.

  As described above, the flow rate measuring device 10 can calculate the flow rate of the pipe from the noise generated when demodulating the light reception signal of the light receiving unit that has received the laser light emitted from the light emitting unit. In addition, since laser light is used for measurement, measurement can be performed in a short time. Specifically, by using light, the time from light emission to light reception can be made shorter than that of sound waves or the like. Also, the measurement time and calculation time necessary for calculating noise can be shortened. Thereby, responsiveness can be made high. Also, the flow rate can be calculated continuously.

  Furthermore, since light can be guided by an optical fiber or the like, it is not necessary to provide a light emitting part and a light receiving part directly in the pipe. For this reason, it is not necessary to place electronic components (circuits, etc.) under strict conditions, and the electronic components can be used in various environments. For example, it is possible to measure the flow rate of exhaust gas flowing through a high-temperature pipe.

  In the above embodiment, the received light signal is demodulated at 200 kHz as an example. However, the present invention is not limited to this, and an arbitrary frequency can be used as a frequency to be demodulated. In addition, various configurations can be used as a method for the calculation unit to demodulate the received light signal. For example, a received signal can be demodulated with a predetermined frequency component by extracting a target frequency component using a bandpass filter that passes only a specific frequency component. In addition, when a band pass filter is used, the apparatus configuration can be simplified and the apparatus can be made inexpensive. In addition, it is possible to reduce the calculation performed for the flow rate calculation. Decoding can also be performed by using an FFT (Fast Fourier Transform) computing device or a spectrum analyzer. In the case where an FFT arithmetic unit or a spectrum analyzer is used, the received signal can be demodulated over a certain frequency region.

Here, in the above embodiment, the flow rate is calculated based on the noise of the received light signal demodulated at one frequency (200 kHz) (that is, one frequency component as a result of demodulating the received light signal). It is not limited to. The flow rate calculation device may calculate the flow rate based on noise of a light reception signal demodulated at two different frequencies (that is, two frequency components resulting from demodulation of the light reception signal). Hereinafter, a description will be given with reference to FIG. In the example shown in FIG. 6, the relationship between the noise when demodulating the received light signal at 200 kHz and the exhaust gas flow rate and the relationship between the noise when demodulating the received light signal at 20 kHz and the exhaust gas flow rate are used. Here, FIG. 6 is a graph showing the relationship between the exhaust gas flow rate and noise. In FIG. 6, when the vertical axis is decoded at 200 kHz, the noise (σ (A) / I (× 10 ⁻⁶ / m)) when decoded at 20 kHz is shown, and the horizontal axis is the exhaust gas flow rate (Nm ³ / h). ). The relationship between the noise and the exhaust gas flow rate shown in FIG. 6 can also be calculated based on the measurement result shown in FIG.

  The flow rate measuring device 10 calculates the relationship between the magnitude of noise and the exhaust gas flow rate as shown in FIG. 6 through experiments and measurements in advance, and stores it in the calculation unit 48. The calculating unit 48 demodulates the received light signal transmitted from the light receiving unit 44 at a frequency of 200 kHz and a frequency of 20 kHz, and detects the magnitude of noise in the demodulated result (signal) for each frequency. Thereafter, the exhaust gas flow rate is calculated based on the detected two noise levels and the relationship between the stored noise level and the exhaust gas flow rate. In this way, the exhaust gas flow rate can be measured even using two frequency components.

Also, as shown in FIG. 6, the flow rate at which the magnitude of noise changes greatly depends on the frequency to be demodulated. Specifically, when demodulated at a frequency of 200 kHz, the magnitude of noise does not change when the exhaust gas flow rate is 40 Nm ³ / h or less, but in the range of 50 Nm ³ / h to 90 Nm ³ / h. The noise changes greatly. Also, if the demodulated at frequency 20 kHz, the exhaust gas flow, at a flow rate 60 Nm ³ / h or less, the size of the noise changes greatly in the range of 100 Nm ³ / h from the flow 60 Nm ³ / h, the noise magnitude Hardly changed. Thus, the range of the flow rate that is easy to detect differs depending on the frequency. Accordingly, the flow rate can be calculated with higher accuracy by demodulating at a plurality of frequencies and calculating the flow rate using the detection result. The flow measuring device 10 may switch the demodulation frequency for calculating the calculation result according to the exhaust gas flow rate.

For example, if the calculated flow rate differs between the exhaust gas flow rate calculated from noise at 200 kHz and the exhaust gas flow rate calculated from noise at 20 kHz, the priority is determined according to the magnitude of the flow rate, and the priority order The high measurement result is defined as the exhaust gas flow rate. Specifically, when the calculated flow rate is 60 Nm ³ / h or less, the flow rate calculated from the noise demodulated at 20 kHz is used, and when the calculated flow rate is greater than 60 Nm ³ / h, the calculated flow rate is 200 kHz. The flow rate calculated from the noise resulting from the demodulation is used. In addition, you may calculate using the correlation of two calculation results. The average value may be the calculated value.

  When demodulating the received light signal at two frequencies, for example, two band pass filters may be provided.

  Moreover, the frequency to demodulate is not limited to two, and the number is not limited. Further, when two or more results demodulated by frequency are used, the flow rate of the exhaust gas may be calculated based on the correlation of the measurement results. That is, in the case of demodulating at each frequency, the relationship between noise and flow rate is calculated in advance, and the exhaust gas flow rate is calculated by relatively comparing a plurality of calculation results. Thus, the exhaust gas flow rate can be calculated with higher accuracy by increasing the frequency to be demodulated. When decoding at a plurality of frequencies as described above, a bandpass filter may be provided for each frequency to be decoded. However, by analyzing the received light wavelength in a certain wavelength range using the above-described FFT converter or spectrum analyzer. You may demodulate. When the frequency to be demodulated can be switched (adjusted), it is preferable to increase the purge flow rate when the exhaust gas flow rate is low (low flow rate) and to decrease the purge flow rate when the exhaust gas flow rate is high (high flow rate). . Thereby, measurement sensitivity can be made high. In addition, the flow volume for determination may use the flow volume immediately before, and may use the flow volume calculated by rough calculation.

  Here, it is preferable that the flow rate measuring device 10 further calculates the exhaust gas flow rate based on the flow rate of the purge gas flowing through the incident tube 22. Specifically, the relationship between the magnitude of noise and the exhaust gas flow rate described above is measured for each purge gas flow rate, the measured relationship is stored, the flow rate of the purge gas flowing through the incident tube 22 is measured, and the measurement result is used. Therefore, it is preferable to select the relationship between the magnitude of noise to be used and the exhaust gas flow rate.

  Hereinafter, a description will be given with reference to FIG. Here, FIG. 7 is a graph showing the relationship between frequency and noise. In FIG. 7, the vertical axis represents noise (dB), and the horizontal axis represents frequency (kHz). The frequency is a frequency obtained by demodulating the received light signal detected by the light receiving unit. FIG. 7 shows the results of measuring the relationship between frequency and noise when the purge flow rate is 1 l / min, 5 l / min, and 10 l / min. The measurement was performed under the same conditions except for the purge flow rate. As shown in FIG. 7, when the purge flow rate changes, the relationship between frequency and noise also changes. That is, even when demodulated at the same frequency, the magnitude of noise changes as the purge flow rate changes.

  On the other hand, by calculating the exhaust gas flow rate based on the flow rate of the purge gas flowing through the incident tube 22, the exhaust gas flow rate can be measured with high accuracy. That is, it is possible to suppress an error in the measurement result of the exhaust gas flow rate due to the change in the purge flow rate. In the case where the purge flow rate does not change, measurement can be performed with high accuracy without switching the relationship between the amount of noise to be used and the exhaust gas flow rate in accordance with the purge gas flow rate.

  In the above description, the relationship between the amount of noise to be used and the exhaust gas flow rate is selected according to the purge flow rate, but the present invention is not limited to this. For example, the purge flow rate may be adjusted so that the detected noise falls within a predetermined range. In other words, the purge flow rate may be positively adjusted so that the noise is in a range in which measurement is easy. For example, when the exhaust gas flow rate is low (low flow rate), the measurement sensitivity can be increased by increasing the purge flow rate. Further, when the exhaust gas flow rate is high (high flow rate), the measurement sensitivity can be increased by reducing the purge flow rate.

  Here, the flow rate measuring device is preferably provided with a turbulent flow generation mechanism that generates turbulent flow around the temperature boundary layer. Hereinafter, a description will be given with reference to FIGS. FIG. 8A is a schematic diagram illustrating a schematic configuration of a part of another embodiment of the flow rate measuring device, and FIG. 8B is a partially enlarged view of FIG.

  A measurement cell 90 shown in FIG. 8A has a protrusion 92 serving as a turbulent flow generation unit. The protrusion 92 is disposed upstream of the incident tube 22 in the exhaust gas flow direction of the main tube 20 and in the vicinity of the incident tube 22, that is, in the vicinity of the connection portion between the main tube 20 and the incident tube 22. The protrusion 92 is convex on the upstream side of the exhaust gas flow, and generates a turbulent flow downstream of the protrusion 92 as shown in FIG.

  Providing the protrusion 92 serving as a turbulent flow generation portion in this manner can generate turbulent flow (Kalman vortex, etc.) in the laser beam passage path, and is turbulent from the temperature boundary layer. Can do. Thus, it can be made easy to measure by increasing the noise. Thereby, measurement sensitivity can be made higher. As described above, since noise can be easily measured, the flow rate can also be easily calculated. Further, since the noise that becomes the detection value increases, measurement can be performed with higher sensitivity. In other words, by providing a turbulent flow generation section, it is possible to increase the change in the magnitude of noise (characteristics of the received light signal) with respect to the change in the flow rate of exhaust gas, thereby making it possible to measure the flow rate with higher accuracy. it can.

  Here, the flow measuring device 10 may measure the concentration of a specific substance contained in the exhaust gas in addition to the flow rate of the exhaust gas. In addition, the flow measuring device 10 can measure a density | concentration by calculating by a calculation part based on a detected value, without providing a new apparatus fundamentally.

  First, when measuring a density | concentration, let the light emission part 40 be a light emitting element which light-emits the laser beam of the near-infrared wavelength range which the substance of a measuring object absorbs. For example, when the measurement target is nitric oxide, the light emitting unit 40 includes a light emitting element that emits laser light in the near-infrared wavelength region that absorbs nitric oxide. When the measurement target is nitrogen dioxide, the light emitting unit 40 includes a light emitting element that emits laser light in the near-infrared wavelength region that absorbs nitrogen dioxide. When the measurement target is nitrous oxide, the light emitting unit 40 includes a light emitting element that emits laser light in the near-infrared wavelength region that absorbs nitrous oxide. When the measurement target is a plurality of substances, the light-emitting unit 40 may include a plurality of light-emitting elements that emit light in the wavelength ranges absorbed by the respective substances. Further, the light source driver 46 and the control unit 50 output information on the intensity of the laser beam output from the light emitting unit 40 to the calculation unit 48.

  The calculation unit 48 calculates the concentration of the substance to be measured based on the signal (light reception signal) sent from the light receiving unit 44 and the conditions under which the light source driver 46 is driven by the control unit 50. Specifically, the calculation unit 48 calculates the intensity of the laser beam output from the light emitting unit 40 based on the condition that the light source driver 46 is driven by the control unit 50, and receives the received signal sent from the light receiving unit. Based on the above, the intensity of the received laser beam is calculated. The calculation unit 48 compares the intensity of the emitted laser light with the intensity of the received laser light, and calculates the concentration of the substance to be measured contained in the exhaust gas A.

  Specifically, the near-infrared wavelength laser beam L output from the light emitting unit 40 is a predetermined path from the optical fiber 42 to the measurement cell 12, specifically, the window 26, the incident tube 22, the main tube 20, After passing through the emission tube 24 and the window 28, the light reaches the light receiving unit 44. At this time, if the substance to be measured is contained in the exhaust gas A in the measurement cell 12, the laser light passing through the measurement cell 12 is absorbed. Therefore, the output of the laser beam L reaching the light receiving unit 44 varies depending on the concentration of the substance to be measured in the exhaust gas A. The light receiving unit 44 converts the received laser light into a light reception signal and outputs it to the calculation unit 48. Further, the control unit 50 and the light source driver 46 output the intensity of the laser light L output from the light emitting unit 40 to the calculation unit 48. The calculation unit 48 compares the intensity of the light output from the light emitting unit 40 with the intensity calculated from the received light signal, and calculates the concentration of the measurement object of the exhaust gas A flowing through the measurement cell 12 from the decrease rate. As described above, the measuring unit 14 uses the so-called TDLAS method (Tunable Diode Laser Absorption Spectroscopy), and based on the intensity of the output laser beam and the received light signal detected by the light receiving unit 44. It is possible to calculate and / or measure the concentration of the measurement target substance in the exhaust gas A passing through the predetermined position in the main pipe 20, that is, the measurement position. Moreover, the measurement means 14 can calculate and / or measure the concentration of the measurement target substance continuously.

  In addition, when measuring the concentration of a specific substance contained in a gas, the flow rate measuring device adjusts the concentration of various substances by adjusting the device, specifically by adjusting the wavelength of the laser beam to be output. Can be measured. Examples of the measurement object include nitrogen oxides, sulfide oxides, carbon monoxide, carbon dioxide, ammonia and the like.

  Thus, the flow rate measuring device can measure the flow rate of the exhaust gas and the concentration of the specific substance in the exhaust gas basically without increasing the device configuration. In the above embodiment, since only a desired substance can be selected and measured with higher accuracy, the concentration is measured by the TDLAS method. However, the present invention is not limited to this, and the laser beam that has passed through the main tube Various methods for measuring the concentration by receiving the light can be used.

  Next, another embodiment of the flow measuring device will be described with reference to FIGS. 9-1 to 9-3. Here, FIG. 9A is a schematic diagram illustrating a schematic configuration of a light receiving unit of another embodiment of the flow rate measuring device. 9-2 and 9-3 are explanatory diagrams for explaining the operation of the flow rate measuring device shown in FIG. 9-1. The flow measuring device having the light receiving unit shown in FIG. 9A is the same as the flow measuring device 10 described above except for the shape of the light receiving unit.

  The light receiving unit 100 illustrated in FIG. 9A includes four light receiving elements 102, 104, 106, and 108. Here, each of the light receiving elements 102, 104, 106, and 108 is a photodetector such as a photodiode (PD), and sends the intensity (light quantity) of the received laser beam to the calculation unit 48 as a light reception signal. The four light receiving elements 102, 104, 106, and 108 have the same shape and are arranged adjacent to each other. Specifically, the light receiving element 102 has one side in contact with the light receiving element 104 and the other side in contact with the one side is in contact with the light receiving element 106. The light receiving element 104 has one side in contact with the light receiving element 102 and the other side in contact with the one side in contact with the light receiving element 108. The light receiving element 106 has one side in contact with the light receiving element 102 and the other side in contact with the one side in contact with the light receiving element 108. The light receiving element 108 has one side in contact with the light receiving element 106 and the other side in contact with the one side in contact with the light receiving element 104. That is, in the light receiving unit 100, assuming that the center is the origin and the boundary side of each element is the xy plane with the x axis and the y axis, the light receiving element 102 is arranged in the first quadrant and the light receiving element 106 is arranged in the second quadrant The light receiving element 108 is arranged in the third quadrant, and the light receiving element 104 is arranged in the fourth quadrant.

  For example, if the laser beam is not refracted when passing through the temperature boundary layer, the light receiving unit 100 reaches the above-described origin portion and the four light receiving elements 102 and 104 as shown in FIG. 9B. , 106 and 108 reach evenly. On the other hand, when the laser light is refracted when passing through the temperature boundary layer, for example, as shown in FIG. 9C, the arrival position of the laser light 110 moves to the light receiving element 104 side, and the light receiving element 106 includes a laser beam. The light is not received. As described above, in the light receiving unit 100, when the arrival position of the laser beam is shifted, the light received by each light receiving element is increased or decreased, and the light reception signal is changed. Although the amount of light received by each light receiving element varies, the total amount of laser light that has reached can be calculated by summing the intensities of light received by the four light receiving elements.

  Thereby, the flow measuring device having the light receiving unit 100 can calculate the exhaust gas flow rate from the noise of the light reception signal received by one light receiving element. Further, the exhaust gas concentration to be measured can be measured from the total amount of received light signals received by the four light receiving elements. As a result, even when the arrival position of the laser beam changes, all of the light that has arrived can be received and the concentration of the measurement object can be measured from the received intensity, so that the concentration of the measurement object can be measured with higher accuracy. .

  In the above embodiment, the flow rate is calculated by the above-described method using the noise of the received light signal detected by one light receiving element, but the present invention is not limited to this. For example, the flow rate may be calculated by comparing the amount of light received by each light receiving element. That is, relative changes of the four light receiving elements 102, 104, 106, and 108 may be calculated as noise. Specifically, the fluctuation, fluctuation, and movement amount of the laser light may be calculated from the increase / decrease in the received light amount, and the flow rate may be calculated from the result.

  For example, when the relative relationship between the purge flow rate and the exhaust gas flow rate changes, the shape of the temperature boundary layer also changes. Thereby, the fluctuation frequency of the fluctuation frequency of the laser beam and the maximum moving distance from the origin change. The calculation unit stores these relationships calculated in advance through experiments and the like, and based on the received light signal, the calculated results (ratio of received light amount of each light receiving element, change frequency, etc.) and the stored relationship From this, the flow rate is calculated.

  The calculation unit 48 calculates the arrival position of the laser light from the relative relationship between the four light receiving elements 102, 104, 106, and 108, and calculates the exhaust gas flow rate from the distance between the arrival position and the origin. Also good. That is, as described above, the maximum moving distance (displacement from the origin) of the laser light can be calculated from the relative relationship between the purge flow rate and the exhaust gas flow rate. Thereby, the flow rate of exhaust gas can also be calculated by calculating the moving distance of the laser beam.

  In the above embodiment, the arrival position of the laser light is calculated based on the balance of the received light amounts of the four light receiving elements, but the present invention is not limited to this. Another example of the light receiving unit will be described with reference to FIG. Here, FIG. 10 is a schematic diagram illustrating a schematic configuration of another example of the light receiving unit. In the light receiving unit 130 shown in FIG. 10, light receiving elements 132 are arranged in a matrix. Specifically, 64 light receiving elements 132 are arranged in a matrix of 8 vertically and 8 horizontally. Each of the 64 light receiving elements 132 of the light receiving unit 130 sends a light reception signal to the calculation unit 48.

  In this way, by arranging the light receiving elements in a matrix, the arrival position of the laser beam can be calculated based on the position of the received light receiving elements. For example, when the laser beam 140 reaches the center of 8 × 8, the four light receiving elements in the center detect the light. In this case, the center of the four light receiving elements may be the arrival position. In addition, when the laser beam moves and the arrival position of the laser beam reaches the position 142, the center of the four received light receiving elements may be set as the arrival position. Further, when the laser beam further moves and the arrival position of the laser beam reaches the position 144, the number of light receiving elements that receive the light is one. In this case, the position of the one light receiving element may be the arrival position.

  Thus, by arranging a large number of light receiving elements in a matrix, the arrival position of the laser light can be detected without detecting the balance of the amount of received light. Further, the flow rate measuring device can calculate the flow rate from the information on the arrival position. The arrangement order of the light receiving elements is not limited to this embodiment. For example, in the vicinity of the center portion, the light receiving element may be disposed in the light so as to become sparse as the distance from the center increases.

  The flow measuring device is not limited to the above embodiment. The flow measuring device uses various methods for calculating the exhaust gas flow rate based on the light reception signal of the light receiving unit, utilizing the fact that the characteristics of fluctuations in the arrival position of the laser beam change depending on the relative relationship between the exhaust gas flow rate and the purge gas flow rate. Can be used. That is, the flow measurement device of the present invention calculates various characteristics (noise, fluctuation position, movement distance) of the arrival position fluctuation of the laser beam based on the light reception signal sent from the light receiving section, and is also necessary. Accordingly, the flow rate of the exhaust gas is calculated by taking the flow rate of the purge gas into consideration.

  As described above, by arranging the outlets of the purge gas supply pipes 30 and 32 toward the windows 26 and 28, the purge gas can be efficiently supplied around the windows 26 and 28. Can be reliably prevented from becoming dirty. For this reason, it is preferable to arrange the outlets of the purge gas supply pipes 30 and 32 toward the windows 26 and 28, but the present invention is not limited to this. For example, the purge gas may be discharged in a direction perpendicular to the axes of the entrance tube and the exit tube.

  Moreover, in the said embodiment, although the incident tube and the output tube were provided coaxially, it is not limited to this. For example, an optical mirror may be provided in the measurement cell, and laser light incident from the window of the incident tube may be multiple-reflected by the optical mirror in the measurement cell before reaching the window of the emission tube. As described above, the multiple reflection of the laser light allows a larger area in the measurement cell 44 to pass. Thereby, the influence of the distribution of the concentration of the exhaust gas flowing in the measurement cell 44 (variation in the flow rate and density of the exhaust gas, variation in the concentration distribution in the exhaust gas) can be reduced, and the concentration can be detected accurately.

  Moreover, in the said embodiment, although the main pipe of the measurement cell and the piping which flows exhaust gas were made into the separate member in all, it is good also as integral. For example, the main pipe of the measurement cell may be directly connected to a device that discharges exhaust gas.

  Moreover, the tube shape of the main tube of the measurement cell is not limited as long as the laser beam can pass therethrough, and may be a tube having a circular cross section, a tube having a polygonal cross section, or a tube having an elliptical cross section. Moreover, the cross section of the inner periphery and the outer periphery of the tube may have different shapes. Further, the shapes of the incident tube and the emitting tube are not limited as described above.

  Moreover, in the said embodiment, although the flow volume of the gas which flows through piping was measured, this invention is not limited to this, The measurement of a flow velocity is also possible. For example, the flow velocity can be calculated by using the relationship between the light reception signal and the flow rate described above and the relationship between the flow rate and the flow velocity. That is, since the pipe diameter is constant, the flow velocity can be calculated by dividing the calculated flow rate by the pipe diameter. Further, by calculating the relationship in advance, such as the relationship between the light reception signal and the flow rate, the flow velocity can be calculated from the measured value of the light reception signal. That is, the flow measurement device can be used as a flow velocity measurement device by changing the calculation method and calculation formula by the calculation unit. Further, the flow rate measuring device can have a flow velocity measuring function. Thus, when measuring the flow velocity, as described above, measurement can be performed with high responsiveness, and measurement can be performed in a severe environment.

  Further, when measuring the flow velocity, it is not limited to measuring the flow velocity of the gas (fluid) flowing in the pipe (flow path), and the measurement region is between the incident tube and the emission tube (passage path of the laser beam). And the flow velocity of the fluid flowing through the measurement region can be measured. That is, it is not limited to the fluid flowing through the closed flow path, and the flow velocity of the fluid flowing through the open measurement region can also be measured.

  Hereinafter, an example of the flow velocity measuring device will be described with reference to FIGS. 11, 12-1, and 12-2. Here, FIG. 11 is a schematic diagram showing a schematic configuration of an embodiment of the flow velocity measuring apparatus of the present invention. FIG. 12-1 is an enlarged schematic diagram showing a part of the measurement cell of the flow velocity measuring device shown in FIG. 11 in an enlarged manner, and FIG. 12-2 shows the measurement cell of the flow velocity measuring device shown in FIG. It is the schematic diagram seen from the direction parallel to a flow direction. The flow velocity measuring device 200 is the same as the flow measuring device 10 except for the relationship between the exhaust supply device that discharges exhaust gas and its piping, and the calculation method of the calculation unit 210. Therefore, portions of the flow velocity measuring apparatus 200 that have the same configuration as that of the flow measurement device 10 are denoted by the same reference numerals, description thereof will be omitted, and the configuration unique to the flow velocity measuring apparatus 200 will be described below. .

  As shown in FIG. 11, the flow velocity measuring apparatus 200 includes a measurement cell 202, a measurement unit 204, and a purge gas supply unit 16, and the exhaust gas A discharged from the pipe 9 passes through a predetermined measurement region. Measure the flow rate. In the exhaust gas discharged from the pipe 9, a part of the exhaust gas A passes through the measurement region, and a part of the exhaust gas A ′ does not pass through the measurement region.

  The measurement cell 202 basically includes an entrance tube 22 and an exit tube 24. Further, the incident tube 22 is provided with a window 26 and a purge gas supply tube 30, and the emission tube 24 is provided with a window 28 and a purge gas supply tube 32. That is, the measurement cell 202 has the same configuration as the measurement cell 12 except that it does not include a main pipe. Next, the arrangement positions of the entrance tube 22 and the exit tube 24 will be described.

  As shown in FIGS. 11, 12-1, and 12-2, the incident tube 22 is arranged at a position spaced apart from the pipe 9 by a certain distance on the downstream side of the end of the pipe 9 in the exhaust gas A discharge direction. Yes. In addition, as shown in FIG. 12B, the incident tube 22 has one end (the end from which the purge gas is discharged) disposed inside the region surrounded by the extension line of the opening surface of the pipe 9. ing.

  Further, the emission pipe 24 is also arranged at a position spaced apart from the pipe 9 by a certain distance on the downstream side of the end of the pipe 9 in the exhaust gas A discharge direction. In addition, as shown in FIG. 12B, the incident tube 22 has one end (the end from which the purge gas is discharged) disposed inside the region surrounded by the extension line of the opening surface of the pipe 9. ing. Further, the emission tube 24 is disposed to face the incidence tube 22. Specifically, one end is disposed at a position facing one end of the incident tube 22 and at a position where the exhaust gas A flows between the incident tube 22 and the emission tube 24. In addition, the arrangement position of the incident tube 22 and the emission tube 24 can be fixed by an arbitrary support portion.

  The measurement cell 202 has such a configuration, and the laser light incident on the incident tube 22 from the window 26 passes through a space (measurement region) between the incident tube 22 and the emission tube 24. The laser beam that has passed through the measurement region passes through the emission tube 22 and the window 28 and is received by the light receiving unit 44.

  Next, the measuring unit 204 includes a light emitting unit 40, an optical fiber 42, a light receiving unit 44, a light source driver 46, a calculating unit 210, and a control unit 50. In addition, since the light emission part 40, the optical fiber 42, the light-receiving part 44, the light source driver 46, and the control part 50 are the same as each part of the measurement means 14 mentioned above, description is abbreviate | omitted.

  As described above, the calculation unit 210 stores the relationship between the light reception signal and the flow rate in advance, and calculates the flow rate of the exhaust gas flowing through the measurement region based on the light reception signal sent from the light reception unit 44. The calculation will be described later.

  The flow velocity measuring device 200 supplies the purge gas to the incident tube 22 and the emission tube 24 by the purge gas supply means 16. Further, the exhaust gas A discharged from the pipe 9 flows in the measurement region (that is, between the incident tube 22 and the emission tube 24). Accordingly, as shown in FIGS. 12A and 12B, a temperature boundary layer 220 formed by mixing the purge gas G and the exhaust gas A is formed at the outlet (one end portion) of the purge gas of the incident tube 22. Is done. Thus, the formation of the temperature boundary layer 220 causes (noise) fluctuations in the light reception signal. Further, this variation varies depending on the relationship between the flow rate of the purge gas G and the flow rate of the exhaust gas A.

  The calculation unit 210 stores in advance the relationship between the flow velocity and the fluctuation of the received light signal by experiments or the like, and calculates the flow velocity based on the received light signal at the time of measurement. That is, the calculation result is the flow rate from the flow rate, but the flow rate is calculated basically in the same manner as described above.

  As described above, the flow velocity measuring apparatus can calculate the flow velocity by supplying the purge gas to the incident tube while allowing the laser beam to pass through the measurement region and measuring the received light signal. Moreover, the flow velocity measuring apparatus can perform measurement without providing a main pipe through which exhaust gas to be measured flows, as in this embodiment. For this reason, a measurement region can be set freely and the degree of freedom of measurement can be further increased. For example, the flow velocity at each position can be measured by changing the distance between the entrance tube and the exit tube to various distances. Also. The distance from the exhaust gas discharge opening can also be various distances. Furthermore, for example, the flow velocity at an arbitrary position in the pipe can be measured.

  In the case of a flow velocity measuring device, it is also possible to store more than one relationship between the received light signal and the flow velocity based on various other conditions, and to calculate more accurately by switching the relationship to be used based on the various conditions. it can.

  Moreover, although the said embodiment made gaseous gas measurement object in all, when it is a liquid, it can measure a flow volume and a flow velocity similarly. That is, it can be measured regardless of gas or liquid as long as it is a fluid. When measuring the liquid flow rate and flow velocity, it is preferable to use a liquid as the purge fluid.

  As described above, the flow rate measuring device and the flow velocity measuring device according to the present invention are useful for measuring the flow rate or flow velocity of a fluid.

6, 8 Piping 10 Flow measuring device 12 Measuring cell 14 Measuring means 16 Purge gas supply means 20 Main pipe 22 Incident pipe 24 Emission pipe 26, 28 Window 30, 32 Purge gas supply pipe 40 Light emitting part 42 Optical fiber 44 Light receiving part 46 Light source driver 48 Calculation 50 Control unit 52 Pump 54 Dryer 56 Flow meter 200 Flow velocity measuring device

Claims (26)

A main pipe that can be connected to a flow path through which fluid flows, and a window that allows light to pass through at the end opposite to the side connected to the main pipe. A pipe, an exit pipe connected to the main pipe, and an exit pipe formed with a window through which light can pass at an end opposite to the side connected to the main pipe, and a first purge fluid supply pipe connected to the incident pipe A measuring cell composed of
A purge fluid supply section for supplying a purge fluid to the first purge fluid supply pipe of the measurement cell;
A light emitting unit for making a laser beam incident on the incident tube;
A light receiving unit that is incident from the incident tube, passes through the measurement cell, receives the laser light emitted from the emission tube, and outputs the received light amount as a received light signal;
A calculation unit that calculates a flow rate of fluid flowing through the measurement cell based on a light reception signal output from the light reception unit;
Possess a control unit which controls operation of each section, and
The calculation unit detects fluctuations that occur in the laser light as the laser light passes through a temperature boundary layer generated by mixing the purge fluid flowing in the incident tube with the fluid flowing in the flow path. And a flow rate measuring device that calculates the flow rate of the fluid based on the detected fluctuation .   A main pipe that can be connected to a flow path through which fluid flows, and a window that allows light to pass through at the end opposite to the side connected to the main pipe. A pipe, an exit pipe connected to the main pipe, and an exit pipe formed with a window through which light can pass at an end opposite to the side connected to the main pipe, and a first purge fluid supply pipe connected to the incident pipe A measuring cell composed of
  A purge fluid supply section for supplying a purge fluid to the first purge fluid supply pipe of the measurement cell;
  A light emitting unit for making a laser beam incident on the incident tube;
  A light receiving unit that is incident from the incident tube, passes through the measurement cell, receives the laser light emitted from the emission tube, and outputs the received light amount as a received light signal;
  A calculation unit that calculates a flow rate of the fluid flowing through the measurement cell based on a light reception signal output from the light reception unit;
  A control unit for controlling the operation of each unit,
  The calculation unit demodulates the received light signal received by the light receiving unit at at least one frequency, and calculates the flow rate of the fluid based on the magnitude of fluctuation of the demodulated signal and the flow rate of the purge fluid flowing in the incident tube. A flow rate measuring device characterized by: The calculating unit demodulates the received signal received by the light receiving portion at one frequency, based on the size of the variation of the demodulated signal, according to claim 1 or 2, characterized in that to calculate the flow rate of the fluid The flow measurement device described in 1. The calculating unit demodulates the received light signal received by the light receiving unit at two different frequencies, and calculates the flow rate of the fluid based on the magnitude of signal fluctuation at the two demodulated frequencies. The flow rate measuring device according to claim 1 or 2 . The calculating unit demodulates the received light signal received by the light receiving unit at a plurality of different frequencies, and calculates the flow rate of the fluid based on the magnitude of signal fluctuations at the demodulated plurality of frequencies. The flow rate measuring device according to claim 1 or 2 . The calculation unit stores a relationship between the previously calculated change and flow rate, one of claims 2 to 5, characterized in that to calculate the flow rate of the fluid based on the size of the said relationship varies The flow rate measuring device according to claim 1. The calculation unit stores the relationship between the fluctuation and the flow rate of the fluid for each flow rate of the purge fluid flowing through the incident tube,
Flow measuring device according to any one of claims 2 to 5, characterized in that to calculate the flow rate of the fluid based on the flow rate and the fluctuation of the purge fluid flowing through the incident tube. The control unit calculates a flow rate of the purge fluid having a large change amount in a region including the flow rate of the fluid calculated by the calculation unit, and based on a calculation result, the control unit calculates the first flow rate from the purge fluid supply unit. The flow rate measuring device according to claim 7 , wherein the flow rate of the purge fluid supplied to the purge fluid supply pipe is adjusted. The calculating unit further includes a strength of the laser light output from the light emitting unit, on the basis of the intensity of the laser light received by the light receiving unit, also the concentration of the substance to be measured of the fluid flowing in the measuring cell is calculated The flow rate measuring device according to any one of claims 1 to 8 , wherein: The light receiving unit has a plurality of light receiving elements arranged adjacent to each other, and outputs the amount of light received by each light receiving element as a light receiving signal,
The flow rate measuring device according to any one of claims 1 to 9 , wherein the calculation unit calculates the flow rate of the fluid based on a comparison of the intensity of a light reception signal sent from each light receiving element. . The calculation unit calculates the arrival position of the laser beam based on a comparison of the intensity of the received light signal sent from each light receiving element, and calculates the flow rate of the fluid based on a deviation between the arrival position and a reference position. The flow rate measuring device according to claim 10 , wherein the flow rate measuring device is calculated. The calculating unit comprises: a total intensity of the received signal sent from the light receiving element, on the basis of the intensity of the output to the laser light from the light emitting portion, also the concentration of the substance to be measured of the fluid flowing in the measuring cell The flow rate measuring device according to claim 10 or 11 , wherein the flow rate measuring device is calculated. The measurement cell has a turbulent flow generating section that turbulently flows the air in the vicinity of the incident tube on the upstream side of the incident tube in the fluid flow direction of the main tube and in the vicinity of the incident tube. The flow rate measuring device according to any one of claims 1 to 12 , wherein And a second purge fluid supply pipe connected to the emission pipe,
The flow rate measuring device according to any one of claims 1 to 13 , wherein the purge fluid supply unit also supplies a purge fluid to a second purge fluid supply pipe. The calculating unit is further based on the light reception signal output from the light receiving unit, to any one of claims 1 to 14, characterized in that for measuring the flow velocity of the fluid flowing through the main pipe of the measuring cell The flow rate measuring device described. The fluid flow rate measurement apparatus according to any one of claims 1 to 15, characterized in that a gas. One end is an opening facing the measurement region, an incident tube having a window portion through which light can pass at the opposite end, one end facing the incident tube, and the measurement region A measurement cell composed of an exit tube formed with a window portion through which light can pass at the opposite end, a first purge fluid supply tube connected to the incident tube,
A purge fluid supply section for supplying a purge fluid to the first purge fluid supply pipe of the measurement cell;
A light emitting unit for making a laser beam incident on the incident tube;
A light receiving unit that is incident from the incident tube, passes through the measurement region, receives laser light emitted from the emission tube, and outputs the received light amount as a light reception signal;
Based on the light reception signal output from the light receiving unit, a calculation unit that calculates the flow velocity of the fluid flowing through the measurement region;
Possess a control unit which controls operation of each section, and
The calculation unit detects fluctuations that occur in the laser light as the laser light passes through a temperature boundary layer generated by mixing the purge fluid flowing in the incident tube with the fluid flowing in the flow path. And calculating the flow velocity of the fluid based on the detected fluctuation .   One end is an opening facing the measurement region, an incident tube having a window portion through which light can pass at the opposite end, one end facing the incident tube, and the measurement region A measurement cell composed of an exit tube formed with a window portion through which light can pass at the opposite end, a first purge fluid supply tube connected to the incident tube,
  A purge fluid supply section for supplying a purge fluid to the first purge fluid supply pipe of the measurement cell;
  A light emitting unit for making a laser beam incident on the incident tube;
  A light receiving unit that is incident from the incident tube, passes through the measurement region, receives laser light emitted from the emission tube, and outputs the received light amount as a light reception signal;
  Based on the light reception signal output from the light receiving unit, a calculation unit that calculates the flow velocity of the fluid flowing through the measurement region;
  A control unit for controlling the operation of each unit,
  The calculation unit demodulates the received light signal received by the light receiving unit at at least one frequency, and calculates the flow velocity of the fluid based on the magnitude of fluctuation of the demodulated signal and the flow rate of the purge fluid flowing in the incident tube. A flow rate measuring device characterized by:   19. The calculation unit according to claim 17, wherein the calculation unit demodulates the light reception signal received by the light reception unit at one frequency, and calculates the flow velocity of the fluid based on the magnitude of fluctuation of the demodulated signal. The flow velocity measuring device according to 1.   The calculating unit demodulates the received light signal received by the light receiving unit at two different frequencies, and calculates the flow velocity of the fluid based on the magnitude of signal fluctuation at the two demodulated frequencies. The flow velocity measuring device according to claim 17 or 18.   The calculating unit demodulates the received light signal received by the light receiving unit at a plurality of different frequencies, and calculates the flow velocity of the fluid based on the magnitude of signal fluctuation at the demodulated frequencies. The flow velocity measuring device according to claim 17 or 18.   The calculation unit stores a relationship between a fluctuation and a flow velocity calculated in advance, and calculates the flow velocity of the fluid based on the relationship and the magnitude of the fluctuation. The flow velocity measuring device according to claim 1.   The calculation unit stores the relationship between the fluctuation and the flow velocity of the fluid for each flow rate of the purge fluid flowing through the incident tube,
  The flow velocity measuring device according to any one of claims 18 to 21, wherein the flow velocity of the fluid is calculated based on a flow rate of the purge fluid flowing in the incident tube and the fluctuation.   The control unit calculates a flow rate of the purge fluid that has a large change amount in a region including the fluid flow velocity calculated by the calculation unit, and based on the calculation result, the control unit calculates the first flow rate from the purge fluid supply unit. The flow rate measuring device according to claim 23, wherein the flow rate of the purge fluid supplied to the purge fluid supply pipe is adjusted. The measurement cell is connected to one end of the incident tube and one end of the exit tube, respectively, and has a main tube through which a fluid to be measured flows.
The flow velocity measuring device according to any one of claims 17 to 24, wherein the measurement region is a part of the main pipe. The flow velocity measuring device according to any one of claims 17 to 25 , wherein the fluid is a gas.

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