JP6536747B2 - Exhaust gas measuring device - Google Patents

Description

  The present invention relates to an exhaust gas measuring apparatus which takes in exhaust gas of a car or the like as a sample gas and measures the number of particles contained in the sample gas.

  In order to measure the number of particulate matter in the gas discharged from an automobile engine etc., the sample gas is mixed and diluted with a dilution gas such as air, and the mixed gas is introduced into the particle number measuring device. There are systems that are configured to measure the number of particles contained in the exhaust gas. As a particle number measuring device of such a system, for example, a particle measuring device which classifies and measures particles in a sample gas according to their size is used (see Patent Document 1).

WO2013-183652A1 Unexamined-Japanese-Patent No. 2012-127773

  The above system includes a flow meter that measures the flow rate of the mixed gas from the mixing unit that mixes the sample gas and the dilution gas, and a flow meter that measures the flow rate of the dilution gas that is supplied to the mixing unit. It is general to control the flow rate of the sample gas introduced into the particle number measuring apparatus and its dilution rate constant based on the measurement value of the meter.

  In the above gas flow rate control method, the flow rate of the sample gas introduced into the particle number measuring device is determined by subtracting the measured value of the dilution gas flow rate from the measured value of the mixed gas flow rate. Thus, the valve provided on the sample gas side is controlled. Therefore, it is necessary to use the measurement values of two flowmeters, one for the mixed gas and the other for the dilution gas, to control the sample gas flow rate.

  For example, when a full scale 10 l / min flow meter is used and the accuracy is ± 1% with respect to the full scale, the dilution rate is 10 times and the mixed gas flow rate is 9 l / min, and dilution is performed. Assuming that the flow rate of the for-use gas is set to 8.1 L / min, the actual mixed gas flow rate is 9 ± 0.1 L / min, the dilution gas flow rate is 8.1 ± 0.1 L / min, and the sample gas flow rate is It will be 0.9 ± 0.2 L / min. This means that an error of up to about 20% occurs from the setting value of the original sample gas flow rate. Since the error of the sample gas flow rate greatly affects the measurement accuracy, it is desirable to control the flow rate of the sample gas with higher accuracy.

  In addition, if a flow meter is installed on the flow path for introducing the exhaust gas into the mixing unit and the flow rate of the sample gas is controlled based on the measurement value of the flow meter, the sample gas flow rate is measured based on the measurement value of one flow meter. It can be controlled. However, if a high concentration exhaust gas containing oil and particulate matter is introduced into the flowmeter, the inside of the flowmeter will be contaminated and the measurement accuracy of the flowmeter will decrease, or particulate matter in the exhaust gas will be deposited in the flowmeter. There is a concern that particles to be introduced into the measuring section may be lost.

  Therefore, an object of the present invention is to provide an exhaust gas analyzer capable of controlling the flow rate of a sample gas with high accuracy while preventing the loss of particles in the sample gas.

  One embodiment of the exhaust gas measurement device according to the present invention includes a mixing unit, an inlet flow channel, a measurement unit, a measurement gas flow channel, a measured gas flow channel, a dilution gas flow channel, a discharge flow channel, a gas purification unit, a pump, A discharge flow rate measuring unit and a discharge flow rate control unit are provided. The mixing unit mixes the sample gas and the dilution gas to form a measurement gas. The inlet flow channel is for introducing a sample gas into the mixing unit, and the measurement gas flow channel is for introducing a measurement gas consisting of the sample gas and the dilution gas mixed in the mixing unit into the measurement unit. The measurement unit measures the measurement gas. In the measured gas flow path, the measured gas that has passed through the measurement unit flows, and the dilution flow path and the discharge flow path are connected to the downstream end of the measured gas flow path. The dilution gas flow path is a flow path for guiding a part of the measured gas to the mixing unit as the dilution gas, and the discharge flow path is a flow path for discharging the gas other than the dilution gas among the measured gas to the outside . The gas purification unit is for purifying at least the dilution gas among the measured gases. The pump includes a sample gas flow flowing through the inlet flow path, a measurement gas flow flowing through the measurement gas flow path, a measured gas flow flowing through the measured gas flow path, a dilution gas flow flowing through the dilution gas flow path, and the discharge flow path Form a flowing stream of measured gas. The discharge flow rate measurement unit measures the gas flow rate flowing through the discharge flow path, and the discharge flow rate control unit controls the gas flow rate flowing through the discharge flow path to a preset flow rate based on the measurement value of the discharge flow rate measurement unit.

  In one embodiment of the exhaust gas measurement device according to the present invention, a part of the measured gas that has passed through the measurement unit is led as the dilution gas to the mixing unit, and the remaining gas of the measured gas is discharged to the outside through the discharge flow path. The sample gas of the same flow rate as the gas discharged to the outside flows from the inlet channel. The discharge flow rate measuring unit and the discharge flow rate control unit are provided on the discharge flow passage, and the gas flow rate flowing through the discharge flow passage is controlled based on the measurement value of the discharge flow rate measuring unit. The flow rate of the gas can be controlled by the discharge flow rate control unit based on the measurement value of the discharge flow rate measurement unit. Since the flow rate of the sample gas can be controlled by one flow meter (discharge flow rate measuring unit), the accuracy of flow control can be enhanced as compared to the method of calculating the difference between the measurement values of two flow meters.

It is a flow-path block diagram which shows one Example of an exhaust gas measuring apparatus. It is a block diagram showing an example of a control system of the example. It is a flow-path block diagram which shows the other Example of an exhaust gas measuring apparatus. It is a sectional view showing roughly an example of a measurement part.

In the conventional method of taking in the dilution gas from the outside, the measuring device is upsized because a pump for introducing the dilution gas into the mixing unit is necessary in addition to the pump for introducing the sample gas into the mixing unit. The
On the other hand, in one embodiment of the exhaust gas measuring apparatus according to the present invention, the sample gas flow flowing in the inlet flow channel, the measurement gas flow flowing in the measurement gas flow channel, the measured gas flow flowing in the measured gas flow channel, for dilution The dilution gas flow flowing in the gas flow path and the measured gas flow flowing in the discharge flow path can be formed by a single pump provided on the measurement gas flow path or on the measured gas flow path. Therefore, the apparatus can be miniaturized without the need for a plurality of pumps.

  Examples of the discharge flow rate control unit include a valve whose opening degree is adjusted based on the measurement value of the discharge flow rate measurement unit.

  In one embodiment of the exhaust gas measurement device according to the present invention, the gas purification unit is preferably provided on the measured gas flow channel. Then, the gas whose flow rate is measured by the discharge flow rate measurement unit can be made clean air purified by the gas purification unit, and the internal contamination of the discharge flow rate measurement unit can be prevented to reduce the measurement accuracy or the flow meter. Failure can be prevented.

  In addition, a measured gas flow rate switching unit is provided which is provided in the middle of the measured gas flow path and switches whether or not at least a part of the measured gas flowing in the measured gas flow path is discharged to the outside. preferable. Then, the flow rate of the measured gas flowing through the measured gas flow path can be made variable, and the flow rate of the dilution gas can be changed by switching the measured gas flow rate switching unit. The dilution rate of the sample gas can be changed by changing the flow rate of the dilution gas.

The measurement gas flow path further includes a charging device for charging particles in the measurement gas,
As the measurement unit, a measurement flow channel through which the measurement gas flows, a flat classification electrode provided along the inner side of the measurement flow channel, and a classification electrode, which are arranged along the measurement gas flow flowing through the measurement flow channel. The charged particles are classified according to their particle sizes by applying a voltage between the classification electrode and the measurement electrode to generate an electric field, and the plurality of measurement electrodes are electrically insulated from each other. There can be mentioned a particle classification measurement device which is captured on the measurement electrode and counts the number thereof. Such a particle classification measuring device is disclosed in Patent Document 1 and is portable since it has a simple and robust structure without a movable part other than the air blowing mechanism. Therefore, by using such a particle classification measurement device, the exhaust gas measurement device can be further miniaturized, and a portable exhaust gas measurement device can also be realized.

  One embodiment of the exhaust gas measuring device will be described with reference to the drawings.

  As shown in FIG. 1, in the exhaust gas measuring apparatus of this embodiment, a sample gas is introduced into the mixing section 16 through the inlet channel 2, and the sample gas is diluted by the dilution gas in the mixing section 16 to measure the measurement gas. Then, the measurement gas is introduced into the measurement unit 18 through the measurement gas channel 3. The measured gas measured by the measuring unit 18 flows through the measured gas flow channel 4, and in the branching unit 6, the exhaust gas discharged to the outside through the discharge flow channel 8 is mixed with the dilution gas flow channel 10 It is divided into dilution gases introduced into the part 16.

  The heater 12 for heating the sample gas on the upstream side of the mixing unit 16 on the inlet channel 2 and the sample gas are drawn through the slit, and particles having a certain size or more are immediately after the slit An impactor 14 is provided which is adjusted to strike against and remove the plate placed there. The heater 12 is for removing volatile substances such as water and oil attached to particles in the sample gas. By providing the heater 12 for heating the sample gas introduced into the mixing unit 16, the particles in the sample gas condense to become large particles and the number of particles decreases, or the particles adhere to the inside of the mixing unit 16. Leading to an improvement in measurement accuracy. A charging device 17 for charging particles in the measurement gas introduced to the measurement unit 18 is provided on the measurement gas flow path 3 between the mixing unit 16 and the measurement unit 18.

  As described later, in the measurement unit 18 of this embodiment, a plurality of measurement electrodes are arrayed along the flow direction of the measurement gas, and the particle classification measurement device counts and classifies the particles according to their size. Charging device 17 is provided. However, the measuring unit 18 does not necessarily have to be such a measuring device, and a particle number measuring device as shown in Patent Document 2 can also be used. In such a case, the charging device 17 is unnecessary.

  An example of the measurement unit 18 is shown in FIG.

  The measurement unit 18 has a measurement flow channel 43 inside, and the measurement gas flowing from the gas inlet 38 flows through the measurement flow channel 43 and flows out from the gas outlet 40. A measurement gas flow path 3 (see FIG. 1) is connected to the gas inlet 38, and a measured gas flow path 4 (see FIG. 1) is connected to the gas outlet 40.

  A classification electrode 42, a trap electrode 44, and measurement electrodes 46, 48, 50, 52, 54 and 56 are provided inside the measurement flow channel 43. The classification electrode 42 is a flat plate electrode provided so as to extend from the upstream side to the downstream side along the measurement gas flow of the measurement flow path 43. The trap electrode 44 is disposed on the upstream end side of the measurement flow channel 43 so as to face the classification electrode 42. The respective measurement electrodes 46, 48, 50, 52, 54 and 56 face the classification electrode 42 and are arranged along the measurement flow path 43 at intervals. The trap electrode 44 and the measurement electrodes 46, 48, 50, 52, 54 and 56 are electrically isolated from one another.

  An electric field for classification is applied between the classification electrode 42 and the trap electrode 44, and each of the measurement electrodes 46, 48, 50, 52, 54 and 56, and charged particles in the measurement gas are classified according to particle size. Is captured by each of the measurement electrodes 46, 48, 50, 52, 54 and 56, and the number is counted.

  Returning to FIG. 1, the measured gas flow rate control unit 20, the pump 22, the three-way valve 24, the purification column 26, and the measured gas flow path 4 on the measured gas flow path 4 through which the measured gas passed through the measuring unit 18 flows. A filter 28 is provided. The measured gas flow rate control unit 20 is configured of a flow meter that measures the flow rate of the measured gas, and a flow control valve whose opening degree is controlled so that the measured value of the flow meter becomes a preset value. . The pump 22 is, for example, a diaphragm pump, and is constantly driven. The flow rate of the measurement gas (sample gas + dilution gas) introduced to the measurement unit 18 is controlled by the measured gas flow rate control unit 20.

  The flow of gas in this exhaust gas measuring apparatus, that is, the flow of sample gas introduced from the inlet channel 2 to the mixing unit, the flow of measurement gas introduced to the measuring unit 18, the dilution gas channel 10 to the mixing unit 16 The flow of the introduced dilution gas and the flow of the measured gas discharged from the discharge flow path 8 are all formed by a single pump 22. As a result, there is no need to provide a dilution gas introduction pump separately from the sample gas introduction pump, and the apparatus can be miniaturized. The pump 22 may be provided on the measurement gas flow path 3.

  The purification column 26 and the filter 28 constitute a gas purification unit that purifies the measured gas into clean air. The purification column 26 is packed with, for example, silica gel for removing water in the measured gas, and activated carbon for removing nitrogen oxides and hydrocarbons in the measured gas. The filter 28 removes solids including particles in the measured gas.

  The downstream end of the measured gas flow path 4 is a branch portion 6 which branches into the discharge flow path 8 and the dilution gas flow path 10. A part of the measured gas that has reached the branch portion 6 is discharged to the outside through the discharge flow path 8, and the remaining measured gas is supplied to the mixing portion 16 through the dilution gas flow path 10 as a dilution gas. Since the dilution gas supplied to the mixing unit 16 is a purified gas, it is not always necessary to remove the water by introducing the dilution gas into the heater. In the case where a dilution gas is separately introduced from the outside, it is necessary to provide a heater for removing water in the dilution gas separately from the heater for the sample gas. The device can be further miniaturized by not providing the heater of the above. In addition, as shown by a broken line in the figure, a heater 29 may be provided on the dilution gas channel 10 in order to prevent the aggregation of water.

  A flowmeter 30 (discharge flow rate measuring unit) and a discharge flow rate control valve 32 (discharge flow rate control unit) are provided on the discharge flow passage 8, and the flow rate of the measured gas discharged through the discharge flow passage 8 is preset. The degree of opening of the discharge flow control valve 32 is adjusted based on the measurement value of the flow meter 30 so as to achieve the above flow rate.

  The flow rate of the measurement gas flowing through the measurement unit 18 is the total flow rate of the flow rate of the sample gas from the inlet channel 2 supplied to the mixing unit 16 and the flow rate of the dilution gas from the dilution gas channel 10. Since the flow rate of the dilution gas from the dilution gas flow path 10 is the flow rate of the measurement gas minus the flow rate of the measured gas discharged through the discharge flow path 8, the sample gas supplied to the mixing unit 16 Is equal to the flow rate of the measured gas discharged from the discharge passage 8. That is, in the system of this embodiment, the flow rate of the sample gas from the inlet channel 2 is controlled based on the measurement value of one flowmeter 30.

  Therefore, since the flow rate of the sample gas introduced to the measurement unit 18 can be controlled based on only the measurement value of one flowmeter 30, the flow rate of the sample gas is controlled based on the difference between the measurement values of the two flowmeters. Control with higher accuracy is possible compared to the case of

  For example, when the set value of the measured gas flow rate control unit 20 is set to 9 L / min and the dilution rate is set to 10 times, it is necessary to control the flow rate of the sample gas to 0.9 L / min. Assuming that the accuracy of the flow meter 30 is ± 1% with respect to the full scale 10 L / min, the flow rate of the sample gas is controlled based only on the measurement value of the flow meter 30, so the error of the sample gas flow is 0. It is about 1 L / min, which is about 10%. On the other hand, when the control is performed based on the difference between the measurement values of the two flow meters under the same conditions, an error of about 20% occurs as described above. Therefore, the configuration of this embodiment can improve the control accuracy of the sample gas flow rate.

  Furthermore, in the configuration of this embodiment, the clean air purified by the purification column 26 and the filter 28 flows through the flow meter 30 and the discharge flow control valve 32, so that the sample gas is contained in the flow meter 30 and the flow control valve 32. There is no problem such as deposition of contained oil and particulate matter.

  In this embodiment, a three-way valve 24 is provided to switch whether to dilute the sample gas. In the above description, it is assumed that the sample gas is diluted, but in this embodiment, the measured gas flowing in the measured gas flow path 4 is branched to the branch portion 6 by switching the three-way valve 24. It can be discharged outside without reaching it. When the measured gas is discharged in the middle of the measured gas flow path 4, the dilution gas is not supplied to the mixing unit 16 from the dilution gas flow path 10, so the sample of the flow rate set by the measured gas flow rate control unit 20 The gas is introduced into the measurement unit 18 without being diluted.

  As indicated by the broken line in the figure, a valve 25 for adjusting the flow rate of the measured gas to be discharged to the outside is provided on the flow path connected to the three-way valve 24 in order to discharge the measured gas to the outside. It may be provided so that part of the measured gas flowing in the measured gas flow path 4 can be discharged to the outside by switching the three-way valve 24. Then, the flow rate of the dilution gas introduced into the mixing section 16 through the dilution gas flow path 10 changes, and the flow rate of the sample gas introduced into the mixing section 16 from the inlet flow path 2 also changes accordingly. , It becomes possible to change the dilution rate of the sample gas.

  An example of the control system of this embodiment will be described with reference to FIG.

  The measured gas flow rate control unit 20, the pump 22, the three-way valve 24, and the discharge flow rate control valve 32 perform operations based on the information given from the control unit 34. The user sets measurement conditions such as the sample gas flow rate and dilution rate to be introduced to the measurement unit 18 to the control unit 34, and the set values thereof are measured gas flow rate control unit 20, pump 22, three-way valve 24 and discharge flow rate Control valve 32 is provided. The discharge flow control valve 32 adjusts the opening degree so that the measured value of the flow meter 30 becomes the set value given from the control unit 34. The measurement data 18 obtained by the measurement unit 18 is taken into the control unit 34.

  The control unit 34 is realized by, for example, a dedicated computer such as a system controller or a general-purpose personal computer.

  As another embodiment, as shown in FIG. 3, the purification column 26 and the filter 28 may be provided on the dilution gas channel 10. In this case, a gas containing a substance such as water or nitrogen oxide is introduced to the flow meter 30 and the discharge flow control valve 32, but since the gas flowing through the discharge flow path is diluted, the inlet flow The concentration is lower than that of the exhaust gas flowing through the passage 2, and the influence of these substances is small as compared with the case where a flow meter or a valve is provided on the inlet passage 2.

DESCRIPTION OF SYMBOLS 2 inlet flow path 3 measurement gas flow path 4 measured gas flow path 6 branch part 8 discharge flow path 10 gas flow path for dilution 12, 29 heater 14 impactor 16 mixing part 17 charging device 18 measurement part 20 measured gas flow rate control part 22 pump 24 three-way valve 25 valve 26 purification column 28 filter 30 flow meter (discharge flow rate measuring unit)
32 Discharge flow control valve (discharge flow control unit)
34 control unit 38 gas inlet 40 gas outlet 42 classification electrode 43 measurement flow path 44 trap electrode 46, 48, 50, 52, 54, 56 measurement electrode

Claims (6)

A mixing unit for mixing the sample gas and the dilution gas into a measurement gas;
An inlet channel for introducing a sample gas into the mixing section;
A measurement unit that measures the measurement gas from the mixing unit;
A measurement gas flow path for introducing a measurement gas composed of the sample gas and the dilution gas mixed in the mixing unit into the measurement unit;
A measured gas flow path through which the measured gas that has passed through the measurement unit flows;
A dilution gas flow path connected to the downstream end of the measured gas flow path for guiding a portion of the measured gas to the mixing unit as a dilution gas;
A discharge flow path connected to the downstream end of the measured gas flow path, for discharging the gas other than the dilution gas among the measured gas to the outside;
A gas purification unit for purifying at least the dilution gas among the measured gases;
A sample gas flow flowing through the inlet flow path, a measurement gas flow flowing through the measurement gas flow path, a measured gas flow flowing through the measured gas flow path, a dilution gas flow flowing through the dilution gas flow path, and the discharge flow A pump for forming a measured gas flow through the passage;
A discharge flow rate measuring unit that measures a gas flow rate flowing through the discharge flow path;
An exhaust gas flow control unit configured to control a gas flow rate flowing through the discharge flow path to a preset flow rate based on a measurement value of the discharge flow rate measurement unit.   The exhaust gas measurement device according to claim 1, wherein the pump is a single pump provided on the measurement gas flow channel or on the measured gas flow channel.   The exhaust gas measurement device according to claim 1, wherein the discharge flow rate control unit is a valve whose opening degree is adjusted based on the measurement value of the discharge flow rate measurement unit.   The exhaust gas measurement device according to any one of claims 1 to 3, wherein the gas purification unit is provided on the measured gas flow channel.   The present invention further includes a measured gas flow rate switching unit which is provided in the middle of the measured gas flow path and switches whether or not at least a part of the measured gas flowing in the measured gas flow path is discharged to the outside. The exhaust gas measuring device according to any one of 1 to 4. The measurement gas flow path further includes a charging device for charging particles in the measurement gas,
The measurement unit faces the measurement flow path through which the measurement gas flows, the flat classification electrode provided along the inside of the measurement flow path, and the classification electrode, and flows along the measurement gas flow flowing through the measurement flow path. The charged particles are arranged for each particle diameter by providing a plurality of measurement electrodes which are arranged in series and electrically isolated from each other, and a voltage is applied between the classification electrode and the measurement electrodes to generate an electric field. The exhaust gas measurement device according to any one of claims 1 to 5, wherein the exhaust gas measurement device is a particle classification measurement device that classifies and captures on each measurement electrode and counts the number thereof.

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