JP2873914B2 - Method and apparatus for testing response characteristics of high-speed gas concentration meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for testing the response characteristics of a high-speed gas concentration meter such as a high-speed response type hydrocarbon analyzer, and more particularly, to a method for determining the time constant of the high-speed gas concentration meter. The present invention relates to a test method and an apparatus that can perform the test.

[0002]

2. Description of the Related Art It is often required to measure the concentration of hydrocarbons at the time of pollution surveys and the like. In such a case, a hydrocarbon analyzer is used. FIG. 4 is an explanatory diagram for explaining a conventional hydrocarbon analyzer. In the case of the conventional hydrocarbon analyzer 01, only the sampling port 03 for extracting the sample gas is disposed in the passage 02 through which the gas to be analyzed flows, and the FID cell 04 serving as the gas analyzer is It was arranged outside the passage 02 together with the main body portion 05. The sample gas is sucked by the pump from the sampling port 03 and guided to the FID cell 04 via the sampling tube 06. Cell 0
In 4, the sample gas is mixed with hydrogen and air and burned, and the state at that time is detected by a sensor. Then, the signal from the sensor is processed in the main unit 05 of the analyzer 01. The combustion exhaust gas generated in the cell 04 is directly discharged to the outside. However, such a hydrocarbon analyzer 01 has a problem that response is poor due to dead volume caused by a long pipe through which a sample gas flows, a suction pump, or the like.

[0003] Therefore, a high-speed response type hydrocarbon analyzer has recently been developed. In the analyzer, a conventional FID cell 04 is separated from a main body 05 of the analyzer, and is arranged close to a sampling port 03 for extracting a sample gas. Hydrogen gas and air are supplied to the cell from outside the passage 02 via a pipe, and the combustion exhaust gas generated in the cell is discharged to the outside via the pipe. Further, a signal output from a sensor in the cell is also guided to the main body of the analyzer provided outside the passage 02. According to such a high-speed response type hydrocarbon analyzer, there is almost no dead volume from the sampling position to the gas analyzer, so that the response is dramatically improved.

[0004]

When measuring the concentration of hydrocarbons, it is often necessary to determine the fluctuation in the concentration. As described above, conventional hydrocarbon analyzers could not measure concentration fluctuations due to poor responsiveness, but according to the recently developed high-speed response type hydrocarbon analyzers, such concentration fluctuations could not be measured. Can also be measured. In that case, it is necessary to know the response characteristics of the fast response type hydrocarbon analyzer in order to make the measurement value accurate. One of such response characteristics is a time constant. The time constant of the analyzer is defined by the time it takes for the detection output to reach 63% when a step-like variation is given. Therefore, in order to know the time constant of a fast-response hydrocarbon analyzer, for example, a gas containing a certain concentration of hydrocarbon is passed through a pipe, and the pipe is instantaneously opened and closed to rapidly change the concentration at that time. What is necessary is just to make it measure with a response-type hydrocarbon analyzer.

As a means for opening and closing the pipe at a high speed, use of an electromagnetic valve or the like can be considered. However, even the fuel injection valve of an engine which is currently considered to have the fastest response takes a time on the order of msec to open and close. Therefore, even if such a valve is used, the rise of the concentration change will be inclined, and it will not be possible to obtain a step-like variation sufficient to obtain the time constant of the fast response type hydrocarbon analyzer. Moreover, its rising characteristics are also unknown. Also, since gas remains in the valve,
The residual gas has an adverse effect on the measurement of the concentration change.

The present invention has been made in view of such circumstances, and has as its object to determine the response characteristics of a high-speed gas concentration meter such as a high-speed response type hydrocarbon analyzer, in particular, its time constant. It is an object of the present invention to provide a method and an apparatus for testing response characteristics of a high-speed gas concentration meter.

[0007]

In order to achieve this object, a method for testing the response characteristics of a high-speed gas concentration meter according to the present invention comprises a tracer gas discharge port for discharging a tracer gas, a sampling port for the high-speed gas concentration meter, Are arranged facing each other at intervals, and a tracer gas is always flowed from the tracer gas discharge port toward the sampling port, and while the air is flowing from the transverse direction to the flow of the tracer gas, the tracer gas discharge port is The flow of the tracer gas is cut off or conducted by moving the shielding plate in and out of the sampling port at a high speed, and a change in the concentration of the gas flowing from the sampling port is measured by a high-speed gas concentration meter.

Further, the response test apparatus for a high-speed gas concentration meter according to the present invention comprises: a disk having a notch formed in an outer peripheral portion thereof;
A motor for rotating the disk, and a portion where the notch crosses when the disk rotates, a tracer gas discharge port for discharging tracer gas and a sampling port for the high-speed gas concentration meter are arranged so as to face each other. It is characterized by having.

[0009]

According to the above-described method of the present invention, by moving the shielding plate between the tracer gas discharge port and the sampling port at a high speed, the tracer gas discharged from the tracer gas discharge port and flowing into the sampling port can be obtained. Is instantaneously interrupted or conducted. Then, by flowing air from the lateral direction to the flow of the tracer gas, the tracer gas staying near the shielding plate is blown off. As a result, the concentration of the gas flowing from the sampling port changes stepwise. Therefore, if the concentration change of the gas is measured by a high-speed gas concentration meter, the time constant of the concentration meter can be obtained.

By using a rotary disk having a notch formed in the outer peripheral portion as in the above-described apparatus according to the present invention, the flow of the tracer gas can be cut off or conducted at a high speed. In addition, when the disk is rotated, centrifugal force causes air to flow from the center to the outer periphery along the two surfaces, so that tracer gas that is blocked by the disk and remains near the two surfaces is blown off by the air flow. Will be able to Therefore, the above-described method of the present invention can be performed.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic perspective view showing an example of a test apparatus for performing a response characteristic test method for a high-speed gas concentration meter according to the present invention, and FIG. 2 is a plan view thereof. As is apparent from these figures, the disk 1 as a shielding plate is provided with a pair of notches 2 and 2 at an outer peripheral portion thereof at intervals of 90 °. The notch 2 has a fan shape with a central angle of 90 °. Therefore, the disk 1 has a shape having a pair of fan-shaped protrusions 3 on its outer peripheral portion. The center of the disk 1 is directly attached to a rotating shaft 5 of a motor 4 fixed to a chassis (not shown). Thus, the disk 1 is rotated at a high speed by the motor 4. At the position where the notch 2 and the projection 3 alternately cross each other when the disk 1 rotates, the tracer gas pipe 6
However, the sampling tubes 7 of the fast response type hydrocarbon analyzer to be tested are provided on the upper side vertically and with their openings facing each other. The tracer gas pipe 6 is configured to constantly eject a tracer gas containing a certain concentration of hydrocarbon from a tracer gas discharge port 8 at an upper end thereof. The sampling tube 7 is connected to a pump (not shown).
The surrounding gas is sucked from the sampling port 9 at the lower end. In this way, a flow of the tracer gas from the tracer gas discharge port 8 to the sampling port 9 is formed, and the flow is conducted or cut off by the rotation of the disk 1. That is, the flow of the tracer gas is conducted at the position where the notch 2 faces the tracer gas discharge port 8, and the flow of the tracer gas is cut off at the position where the protrusion 3 faces the tracer gas discharge port 8.

A photomicrosensor 10 is provided on the outer peripheral side of the disk 1 at a position where the outer peripheral portion of the protrusion 3 crosses. The photomicrosensor 10 has a light receiving element on the upper side and a light emitting element on the lower side, and outputs a high-level signal when facing the notch 2 of the disk 1 and faces the protruding portion 3. Sometimes, a low level signal is output. The photo microsensor 10 is shown in FIG.
As shown in the figure, the center of the disk 1 is disposed on the same radius as the tracer gas discharge port 8 and the sampling port 9. Therefore, when the tracer gas flows from the tracer gas discharge port 8 to the sampling port 9, a high-level signal is output from the photomicrosensor 10, and when the flow of the tracer gas is cut off, the output of the photomicrosensor 10 changes to a low level. Become. In this way, when the disk 1 rotates, a rectangular wave signal is output from the photomicrosensor 10.

An FID cell is mounted in the sampling tube 7 near the sampling port 9 so that the concentration of hydrocarbons in the gas flowing through the sampling tube 7 can be detected by the cell. Then, the detection signal is transmitted to the photomicrosensor 1
Along with the output signal from 0, it is input to a display (not shown).

Next, the operation of the response characteristic test apparatus thus configured will be described. As described above, the tracer gas having a constant concentration is always discharged from the discharge port 8 of the tracer gas pipe 6. The tracer gas flows toward the sampling port 9 of the sampling tube 7. When the disk 1 is rotated by the motor 4, the disk 1
Notches 2 and protrusions 3 alternately face the tracer gas discharge ports 8. Then, while the notch 2 faces the tracer gas discharge port 8, conduction between the discharge port 8 and the sampling port 9 is conducted, and the tracer gas discharged from the discharge port 8 flows in from the sampling port 9. While the protruding portion 3 faces the tracer gas discharge port 8, the discharge port 8
And the sampling port 9 is shut off, and ambient air is sucked from the sampling port 9. Therefore, the hydrocarbon concentration of the gas flowing through the sampling tube 7 fluctuates periodically. In this case, if the rotation speed of the disk 1 is sufficiently increased, the time required for switching between the conduction and the interruption of the flow of the tracer gas becomes extremely short. Further, as the disk 1 rotates, air near the surface of the disk 1 flows from the center toward the outer periphery due to centrifugal force. That is, an air flow is generated in a direction transverse to the flow of the tracer gas. And
The air flow blows off the tracer gas remaining on the lower surface side and the tracer gas remaining on the upper surface side when blocked by the protrusion 3 of the disk 1. Therefore, it is possible to prevent the residual tracer gas from affecting the concentration of the gas sucked from the sampling port 9 at the time of switching between conduction and cutoff of the tracer gas flow. As a result, the hydrocarbon concentration of the gas flowing through the sampling tube 7 changes in a rectangular wave shape. The rise of the rectangular wave is determined by the rotation speed (peripheral speed) of the disk 1 and the diameter of the tracer gas discharge port 8. Therefore, if the diameter of the discharge port 8 is reduced and the rotation speed of the disk 1 is sufficiently increased, the rise time of the density change can be extremely shortened. Thus, by measuring the change in the concentration of the gas flowing from the sampling port 9 using the high-speed response type hydrocarbon analyzer, the time constant of the analyzer can be obtained. The point in time at which the flow of the tracer gas is turned on or off is detected by the photomicrosensor 10, and is output to a display together with the value measured by the fast response type hydrocarbon analyzer. Therefore, if they are displayed simultaneously on the display,
It is possible to obtain not only the time constant of the analyzer but also the response characteristics such as its followability.

[0015] Such a response characteristic test apparatus was actually manufactured as a prototype, and a response characteristic test of a high-speed response type hydrocarbon analyzer was performed using the apparatus. In the test apparatus, a memory disk of a minicomputer was used as the disk 1. Then, fan-shaped fins having a central angle of 90 ° were attached to the outer periphery of the disk 1 at intervals of 90 °, thereby forming the cutouts 2 and 2 and the protruding portions 3 and 3. The disk 1 was rotated by the motor 4 at a high speed of 2,891 rpm. as a result,
The photomicrosensor 10 output a 96.4 Hz rectangular wave signal. At that time, the time required for the edge of the protruding portion 3 of the disk 1 to cross the tracer gas discharge port 8, that is, the rise time of the conduction / cutoff switching of the flow of the tracer gas was 74 nsec, which was almost negligible. . In this state, a tracer gas having a constant hydrocarbon concentration was supplied from the tracer gas discharge port 8, and the output signals of the photomicrosensor 10 and the high-speed response type hydrocarbon analyzer were displayed on a display. The output waveform is shown in FIG.
Shown in In FIG. 3, the horizontal axis represents time, and the vertical axis represents output. As is clear from this figure, at time A, the photomicrosensor 10 is turned on, that is, the notch 2 faces the tracer gas discharge port 8 and the flow of the tracer gas is conducted. At time C, the photomicrosensor 10 is turned off. That is, the flow of the tracer gas was shut off with the protrusion 3 facing the tracer gas discharge port 8.
During that time, tracer gas of a constant concentration discharged from the tracer gas discharge port 8 flows into the sampling tube 7 from the sampling port 9. Therefore, the concentration of the gas flowing from the sampling port 9 should have changed into a rectangular waveform similar to the output waveform of the photomicrosensor 10. As shown in the figure, the output waveform of the fast-response hydrocarbon analyzer that measured this concentration change rises from time B, which is slightly delayed from time A, and gradually saturates.
The waveform becomes the maximum at time D. The time from A to B is the time lag until the gas reaches the FID cell of the hydrocarbon analyzer. The time from C to D also has the same time lag. By reading the time from time B until the output reaches 63% of the maximum output from this output waveform, the time constant of the fast response hydrocarbon analyzer can be obtained. The time constant of the tested hydrocarbon concentration analyzer was about 10 msec.

In the above embodiment, only the case where a response characteristic test of a high-speed response type hydrocarbon analyzer is performed has been described. However, the present invention is not limited to this, and is applicable to other high-speed gas concentration meters. It is possible. In that case,
It goes without saying that a gas corresponding to the concentration meter is used as the tracer gas. Further, the embodiment in which the flow of the tracer gas is interrupted / conducted by the disk 1 has been described. However, in place of the disk 1, for example, a shutter mechanism of a high-speed photographic camera can be used. In that case, in order to prevent the blocked tracer gas from stagnating, a blower or the like that generates an air flow in a direction transverse to the flow of the tracer gas may be used. The photomicrosensor 10 only needs to be able to detect when the flow of the tracer gas is conducted or cut off. Therefore, the installation position can be arbitrarily selected. When only the time constant needs to be obtained, such a sensor can be omitted.

[0017]

As is apparent from the above description, according to the present invention, the flow of the tracer gas is interrupted or conducted at a high speed while the air flows from the lateral direction to the flow of the tracer gas. Therefore, the concentration change of the gas flowing into the sampling port of the gas concentration meter can be changed stepwise. Therefore, the time constant of the gas concentration meter can be obtained. Further, by using a rotating disk having a notch formed in the outer peripheral portion, the flow of the tracer gas can be cut off or conducted at high speed. Moreover, if the disk is rotated, the centrifugal force
A flow of air from the center to the outer periphery is generated along the two surfaces, and the tracer gas remaining near the two surfaces blocked by the disk is blown off by the air flow. There is no need to use it.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing one example of a test apparatus for performing a response characteristic test method of a high-speed gas concentration meter according to the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is a graph showing the results of a response characteristic test performed on a high-speed response type hydrocarbon analyzer by the test apparatus.

FIG. 4 is an explanatory diagram for explaining a conventional hydrocarbon analyzer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotating disk (shielding plate) 2 Notch 3 Projection part 4 Motor 8 Tracer gas discharge port 9 Sampling port 10 Photomicrosensor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 1/00 G01N 27/62

Claims (3)

(57) [Claims] 1. A tracer gas discharge port for discharging a tracer gas and a sampling port of a high-speed gas concentration meter whose response characteristic is to be tested are arranged to face each other with a space therebetween, and are directed from the tracer gas discharge port to the sampling port. The tracer gas is always flowed through, and while the air is flowing from the lateral direction to the flow of the tracer gas, the shield plate is moved in and out of the space between the tracer gas discharge port and the sampling port at a high speed. A method for testing the response characteristics of a high-speed gas concentration meter, comprising shutting off or conducting a flow, and measuring a change in concentration of gas flowing from the sampling port with the high-speed gas concentration meter. 2. A disk having a notch formed in an outer peripheral portion thereof, and a motor for rotating the disk at a high speed, wherein a tracer gas discharger for discharging a tracer gas to a portion crossed by the notch when the disk rotates. An apparatus for testing response characteristics of a high-speed gas densitometer, wherein an outlet and a sampling port of a high-speed gas densitometer for testing a response characteristic are arranged to face each other. 3. The response characteristic testing device for a high-speed gas concentration meter according to claim 2, further comprising a sensor for detecting a position of a notch of said disk.