JPS61265540A - Method for measuring temperature of gas - Google Patents

Abstract

PURPOSE:To make it possible to measure the temp. distribution of combustion gas without almost receiving the effect of attenuation and the noise in a furnace, by propagating an ultrasonic wave with frequency of 11-15kHz through gas to measure the propagation speed of said ultrasonic wave. CONSTITUTION:When a measuring start signal 44 is sent to a trigger generator 45 from a calculator 43, a trigger signal 46 is generated to be sent to an oscillator 47 and a counter 48. Now, when it is assumed that, for example, a transmitter 31 and a receiver 40 are indicated by scanning signals 51, 52, an oscillation signal 53 is converted to an ultrasonic wave by the transmitter 31 while the ultrasonic wave is propagated through a furnace to be received by a receiver 40 and the receiving signal 54 is sent to a counter 48 through a receiver scanner 50. The ultrasonic wave propagation time between the transmitter 31 and the receiver 40 is measured by the counter 48. Then, by selecting a specific frequency region of 11-15kHz, the temp. distribution of combustion gas can be measured hardly receiving the effect of the attenuation in combustion gas and the noise in the furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gas body temperature measuring method for measuring the combustion gas temperature distribution in a furnace such as a coal-fired boiler furnace or a heavy oil-fired boiler furnace.

[Conventional technology]

FIG. 5 is a diagram for explaining a conventional gas body temperature measurement method. In this Fig. 5, a cross section OZ of a three-dimensional object targeted for ultrasonic CT (computed tomography) is shown.
Let be the interior of the circle.

First, a pair of ultrasonic transmitter 02 (hereinafter referred to as transmitter 5) and ultrasonic receiver 03 (hereinafter referred to as receiver) are placed facing each other so that the ultrasonic waves propagate within the cross section. At this time, the ultrasonic propagation time between the transmitter 02 and the receiver 030 is measured as follows.

First, when a start signal 05 for starting measurement is sent from the computer 04 to the trigger generator 06, the trigger signal 07 is generated by the trigger generator 06 and sent to the oscillator 08 and the counter 09.

The oscillator 08 starts oscillating in response to the trigger signal 07, and the oscillation signal XO is input to the transmitter 02, where it is converted into an ultrasonic wave. The ultrasonic wave 11 oscillated from the transmitter 02 propagates within the cross section O1 and reaches the receiver 03.

At this time, an ultrasonic reception signal 12 is generated from the receiver 03 and input to the counter 09. The counter 09 calculates the ultrasonic reception signal 1 from the time when the trigger signal 07 is input.
2 is input, i.e. transmitter 0
The ultrasound propagation time between 2 and receiver 03 is measured.

The measured propagation time is sent to computer 04 and stored in memory.

When the propagation time is measured for one route, the computer 0
A signal is sent from 4 to the scan controller z3, and the control signal 14 from the scan controller 13
Translate the pair of transmitter 02 and receiver 03 by Δr in the r direction, measure the propagation time in the same manner as above, and repeat these operations to measure the propagation time distribution in the 00 direction of cross section 01. .

When the propagation time distribution in the θO direction is measured, a signal is sent from the computer 04 to the scan controller 13 again, and this time the pair of transmitter 02 and receiver 03 are rotated by Δθ in the θ direction, and the same procedure as above is performed. The propagation time distribution in the θ0+Δθ direction was measured, and these operations were converted into (θ0+1
800-Δθ) direction to measure the propagation time distribution in all directions.

All the propagation time data thus obtained are subjected to CT processing by the computer 04, thereby obtaining the sound velocity distribution within the cross section O1.

In C'r processing, first the target cross section is divided into micro regions (metsies), and the sound velocity C(i) in each mesh is calculated.
(x means the first mesh) is treated as a variable. At this time, each propagation time t, (J) (j means the fifth measured propagation time) is expressed by the following equation (1).

t(j)=；Measurement ・・・・・・・・・・・・・・・
・・・・・・・・・・・・ (1) Ic(1) Here, t(1) is the length of the first mesh. For example, if the n-th mesh is If it is not included, treat it as t(→=0.

When each propagation time is expressed by equation (1), what is determined by CT processing is the propagation time Z(t)/C(
1). At this time, since t(1) is determined when the mesh is divided, the sound velocity C(1) in each mesh tool, that is, the sound velocity distribution is obtained.

Since the speed of sound varies depending on the medium in which the ultrasonic wave propagates, the structure within the cross section 01 (for example, body tissue) can be determined from the sound speed distribution.

[Problem that the invention seeks to solve]

When using conventional ultrasound CT to target solids or liquids, the frequency of the ultrasound used is several VH2 or more, and there is no particular problem.

However, when targeting gas, ultrasonic waves with such high frequencies do not propagate, so the frequency is set to several tens of KHz.

However, when a gas containing carbon dioxide gas, such as gas in a combustion furnace, is targeted, the carbon dioxide gas absorbs the ultrasonic waves, which is not desirable.

[Means for solving problems]

This invention was made in order to eliminate the above-mentioned drawbacks of the conventional methods, and involves propagating ultrasonic waves into a gas body, measuring the propagation velocity of the ultrasonic waves, and determining the temperature of the gas body from the measured propagation velocity. In the method, the frequency is between 11 KHz and 15 KHz.
It uses KHz ultrasonic waves.

[Effect]

This invention reduces the frequency of ultrasonic waves from 11 KHz to 151C.
By selecting a specific frequency range of Hz, the temperature distribution of the combustion gas can be measured without being affected by attenuation in the combustion gas and noise in the furnace.

〔Example〕

Embodiments of the gas main temperature measuring method of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a temperature measuring device applied to one embodiment. In FIG. 1, a boiler furnace cross section 3o (hereinafter referred to as the furnace cross section) targeted for ultrasonic CT is assumed to be inside a rectangle. A plurality of ultrasonic transmitters 3x, 32° 33, 34, 3 are installed so that ultrasonic waves propagate in various directions within this furnace cross section 30.
5.36 (hereinafter referred to as a transmitter) and a plurality of ultrasonic receivers 37.3B.

sy, 4o, 4z, and 4z (hereinafter referred to as receivers) are installed around the furnace.

At this time, transmitters 31 to 36 and receivers 37 to 4
The ultrasonic propagation time between 2 and 3 is configured to be measured as follows.

A start signal 44 is sent from the computer 45 to a trigger generator 45, and a trigger signal 46 is sent from the trigger generator 45 to an oscillator 47 and a counter 48.

Further, a scan signal 51 is sent from the calculator 43 to a transmitter scanner 49, and a scanner signal 52 is output to a receiver scanner 50.

The transmitter scanner 49 specifies a predetermined transmitter among the plurality of transmitters 3I-36, and the receiver scanner 50 specifies a predetermined receiver among the plurality of receivers 37-42.

Furthermore, when the oscillator 47 receives a trigger signal 44t, it sends the oscillation signal 53 to a designated transmitter via the transmitter scanner 49, and the transmitter designated by the transmitter scanner 49 converts the oscillation signal 53 into ultrasonic waves. It is supposed to be converted.

The ultrasonic waves propagate within the furnace and are received by a receiver, transmitting a received signal 54 through a receiver scanner 50 to a counter 48.
It is supposed to be sent to

The counter 48 counts the time from the generation of the I/'i trigger signal 46 to the input of the received signal 54, and sends the count value to the computer 43.

Next, a gas body temperature measuring method of the present invention will be explained using this temperature measuring device. First, when a start signal 44 for starting measurement is sent from the computer 43 to the trigger generator 45, a trigger signal 46 is generated from the trigger generator 45 and sent to the oscillator 47 and the counter 48.

Further, in order to simultaneously select a pair of transmitters and receivers to be used for measurement from among the plurality of transmitters 3x to 36 and receivers 37 to 42 at the same time as the trigger signal 46, the computer 43 sends a transmitter scanner 49 and a receiver scanner 50. The scan signals 5x and 52 are sent to the terminals, respectively. For example, assume that the transmitter 31 and receiver 40 are now specified.

At this time, 53 oscillation signals from the oscillator 47 which received the trigger signal 46 are sent to the transmitter 31 via the transmitter scanner 49.

In the transmitter 3I, the oscillation signal 53 is converted into an ultrasonic wave, propagates in the furnace, is received by the receiver 40, and the received signal 54 is sent to the counter 48 via the receiver scanner 50.

The counter 48 measures the time from when the trigger signal 46 is input to when the received signal 54 is input, that is, the ultrasonic propagation time between the transmitter 31 and the receiver 40 . The measured propagation time is sent to computer 43 and stored in memory.

When the propagation time for one route is measured, a signal is sent from the computer 43 to the transmitter scanner 49 and receiver scanner 50, and the pair of transmitter and receiver used for measurement is switched.

In this case, the propagation direction of ultrasonic waves of about 11 to 15 KHz usually spreads out by about ±10° to 20° from the center, so the ultrasonic waves from one transmitter are received by 3 to 5 receivers. Ru.

@1 In figure 1, the ultrasonic waves from each transmitter are 3
The situation in which signals are received by ~5 receivers is shown by dotted lines.

When all scans are completed, 24 propagation times are measured in FIG. 1 and stored in the computer's memory. The reason for setting the frequency to 11 to 15 KHz will be described later.

All the obtained propagation time data is subjected to CT processing by a computer to obtain the sound velocity distribution c (i) in the furnace cross section 30 as in the conventional case.

Here, 1 means the first mesh when the inside of the furnace cross section 30 is divided into meshes, as in the conventional case.

The method of dividing the mesh is different from the conventional method, and the mesh is divided according to the number of obtained propagation times.

Furthermore, when the sensor is moved at equal intervals in both parallel and rotational directions, as in the past, and it is possible to obtain very fine data, a technique called a compo-region method is used in CT processing.

However, when applied to a boiler, the sensor cannot be moved in parallel or rotationally, and there is a limit to the number of sensors that can be attached, so the number of propagation times that can be obtained is extremely small.

In this case, the simultaneous equations shown in the following equation (2), which can be created by the number of propagation times, are solved by the method of least squares (the variables are determined by the Metsy number, and must be equal to or less than the number of propagation times).

t(j) = 5 islands ・・・・・・・・・ (2
) Here, equation (2) holds true when the gas flow velocity v(1) within the mesh is much smaller than C(1).

Further, the obtained sound velocity C(1) is a function of the gas temperature Tt(OK) at the first mesh and is given by the following equation.

C(i) = 20.05 F・・・・・・・・・
(3) Therefore, 1 can be found from equation (3), and the combustion gas temperature distribution within the furnace cross section 30 can be found.

Next, the reason for frequency selection will be explained.

(1) Curve A in FIG. 2 shows the noise level in the boiler furnace with respect to the frequency of sonic waves and ultrasonic waves. Furnace noise is 3
It decreases rapidly from around KHz and does not change much above 11 KHz.

(2) Curve B in FIG. 2 shows the absorption rate of ultrasonic waves by carbon dioxide gas with respect to the ultrasonic frequency. The absorption rate in this case is the value obtained by dividing the absorbed ultrasound intensity when the ultrasound is propagated by 1 rrL by the ultrasound intensity before propagation. As can be seen from curve B, absorption of ultrasonic waves by carbon dioxide gas becomes significant at frequencies above 15 KHz.

For the above two reasons, ultrasonic TFJ is used to measure combustion gas temperature.
For Lc'r, ultrasonic waves of 11 KHz to 15 KHz are practically optimal.

Conventionally, this could only be applied to liquids or solids, but in this example, by selecting a specific frequency range of 11 KHz to 15 KHz, the combustion gas can be controlled with almost no attenuation in the combustion gas or noise in the furnace. Temperature distribution can now be measured, which has a great effect on combustion analysis and boiler optimization design.

Next, a second embodiment of the invention will be described. Third
The figure is a block diagram of a temperature measuring device applied to this @2 embodiment.

Although the first embodiment showed the case where the ultrasonic CT method was applied to the combustion gas by using ultrasonic waves in the 11 KHz to 15 KHz band, the second embodiment By equipping one ultrasonic transducer with the functions of an ultrasonic transmitter and a receiver, and measuring the ultrasonic propagation time in both directions along the same path, we can eliminate the influence of the gas flow rate in the furnace on the propagation time. It is designed to be eliminated.

Next, a second embodiment of the present invention will be specifically described based on FIG. The configuration in FIG. 3 includes a plurality of transmitting and receiving ultrasonic transducers that propagate ultrasonic waves in various directions within the furnace cross section 30 in the transmitters 31 to 36 and receivers 37 to 420 in FIG. The difference is that 31a to 42a (for example, dynamic speakers) are arranged around the furnace, and the other configuration is the same as in Fig. 1, and the same parts as in Fig. 1 are given the same reference numerals and explanation of the structure is omitted. do.

Next, a method for measuring the temperature of a gas body according to the second embodiment will be described.

The ultrasonic propagation time between the ultrasonic transducers 31a to 42a used as transmitters and the ultrasonic transducers 31a to 42a used as receivers is measured as follows.

First, when a measurement start signal 44 is sent from the computer 43 to the trigger generator 451C, a trigger signal 46 is generated and sent to the oscillator 45 and the counter 48.

Simultaneously with the trigger signal, a scan signal 51. 52 is sent.

For example, when the transmitting side transducer 31 and the receiving side converter 40 are specified, the oscillation signal 53 from the oscillator 47 that receives the trigger signal 46 passes through the transmitting side scanner 49 and transmits the ultrasonic wave 1 on the transmitting side.
/if is sent to the converter 31a.

The oscillation signal 53 is converted into an ultrasonic wave by the transmitting side ultrasonic converter 31a-, which propagates in the furnace and is received by the receiving side ultrasonic transducer 40a, and the received signal 54 is sent to the counter 48 via the receiving side scanner 5Q. It will be done.

The counter 48 measures the time from when the trigger signal 46 is input until when the reception signal 54 is input, that is, the ultrasonic propagation time between the transmitting ultrasonic transducer 31a and the receiving ultrasonic transducer 4L)a. measured propagation time 55
is sent to the computer 43 and stored in memory.

When the propagation time for one route is measured, the computer 4
A signal is sent from 3 to the transmitting side scanner 49 and the receiving side scanner 50, and the transmitting side ultrasonic transducer 31a is switched to the receiving side ultrasonic transducer, and the receiving side ultrasonic transducer 40rx is switched to the transmitting side ultrasonic IF switch. , the propagation time of the same route in the opposite direction is measured.

When the two-way propagation time of one route is measured, the computer 43 transmits information to the transmitter side scanner 49 and the receiver side scanner 50.
A signal is sent to the transducer, and the pair of transmitting and receiving transducers of the transmitting and receiving ultrasonic transducer used for measurement is switched for another route. In this case, 11-15 KH
For ultrasonic waves of about z, the propagation direction is ±10~ from the center.
Since the beams are spread out by about 20 degrees, one transmitting ultrasonic wave from the converter is received by eight to nine receiving ultrasonic f converters.

In Figure 3, there are 8 ultrasonic waves from the exchanger on each transmitting side.
The situation in which signals are received by ~9 receivers is shown by dotted lines.

When all the scans are completed, 100 different propagation times are measured in Figure 3 and stored in the computer's memory.
Gas temperature is calculated by ultrasonic CT method.

Now, the minute section L of the first mesh AB cabinet in Figure 4
In (1), the ultrasonic propagation time from point A to point B is ΔtF(i), and the propagation time from point B to point A is Δt
B(1), each propagation time is the gas temperature Ti('K)
From the sound speed C(1) in

Now, by adding the formulas +41 and +51, we get the following (6)
However, the formula (41, +51 holds true if V (
i) < C(i).

From this, the average ultrasonic propagation time in the minute section L(1) is expressed by the following equation (7).

Δt(i) = T(Δty(i)+Δt B(i)
) - Between songs (7) Therefore, the average ultrasonic propagation time in the AB section is expressed by the following equation (8).

This eliminates the influence of the gas flow rate on the ultrasound propagation time.

All the obtained propagation time data is subjected to CT processing by the computer 43, thereby obtaining the sound velocity distribution C(1) in the furnace cross section 30 as in the conventional case. Here, 1 means the first mesh when the inside of the furnace cross section 30 is divided into meshes, as in the conventional case. The mesh division method is different from the conventional method, and is divided according to the number of propagation times that can be obtained.

However, in cases where it is possible to move the sensor at equal intervals in both parallel and rotational movements, as in the past, and to obtain very fine data, a technique called convolution method is used in CT processing.

However, when applied to a boiler, the sensor cannot be moved in parallel or rotationally, and there is a limit to the number of sensors that can be attached, so the number of propagation times that can be obtained is extremely small.

In this case, as many simultaneous equations as there are propagation times (variables are determined by the Mekshu number and must be equal to or less than the number of propagation times) are solved using the method of least squares.

The obtained sound velocity C(1) is a function of the gas temperature Ti('K) at the first mesh and is given by the following equation (9).

C(i) := 20.05β 〒 ・・・ Song・
・・・・・・・・・・・・ (9) Therefore, (9)
T1 is determined from the equation, and the combustion gas temperature distribution within the furnace cross section 30 is determined.

Note that in this second embodiment as well, the frequency range is 11 KHz to 15 KHz.
The reason for selecting a frequency on the order of KHz is the same as in the first embodiment.

In addition to the effects of the first embodiment, the effects of the second embodiment are that by measuring the propagation time in both directions along the same path, the influence of the gas flow rate in the furnace on the ultrasonic propagation time is eliminated; It becomes possible to measure the temperature distribution of combustion gas with high accuracy.

〔Effect of the invention〕

As described above, according to the gas body temperature measurement method of the present invention, the temperature of the gas body is determined by propagating ultrasonic waves with a frequency of 11 KHz to 15 KHz into the gas body and measuring the propagation speed. Therefore, there is almost no attenuation in the combustion gas and noise in the furnace, and the temperature distribution of the combustion gas can be measured, which is highly effective for combustion analysis and boiler optimization design.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a temperature measuring device applied to an embodiment of the gas body temperature measuring method of the present invention, and FIG. 2 is a block diagram of an ultrasonic wave of 11 KHz to 1 applied to the same gas body temperature measuring method.
A diagram showing the ultrasonic absorption rate due to noise in the furnace and carbon dioxide gas versus frequency to explain the reason for selecting the 5 KHz frequency band, Figure 3 is a diagram showing the second embodiment of the gas body temperature measuring method of the present invention. FIG. 4 is a block diagram of the applied temperature measuring device and explains the data processing of the propagation time of ultrasonic waves when the furnace cross section is divided by a mesh, which is applied to the gas temperature measuring method of the second embodiment of the above. FIG. 5 is a block diagram of a temperature measuring device applied to a conventional gas body temperature measuring method. 30...Furnace cross section, 31-36...Ultrasonic transmitter, 31a-42a...Ultrasonic transducer, 43...
- Calculator, 45... Trigger generator, 47... Oscillator, 48... Kakunta, 49... Transmitter scanner, 50... Receiver scanner. Applicant's sub-agent Patent attorney Takehiko Suzue Figure 1 Figure 2 Layer liquid * < Hz) Figure 3 Figure 4 Figure 5 hS

Claims (1)

[Claims] A method for propagating ultrasonic waves in a gas body, measuring the propagation speed of the ultrasonic waves, and determining the temperature of the gas body from the measured propagation speed, which uses ultrasonic waves with a frequency of 11 KHz to 15 KHz. How to measure body temperature.