JP2006153716A - Exhaust gas analyzer and soot measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas analyzer which calculates a dilution ratio necessary when the concentration of soot is measured by a simple low cost constitution and can precisely measure the concentration of Soot. <P>SOLUTION: An SOF measuring system capable of continuously measuring the concentration of SOF and a Soot measuring system capable of continuously measuring Soot are connected to an exhaust gas line. The Soot measuring system is equipped with a dilution device for selectively diluting either one of an exhaust gas or a standard gas known in the concentration of hydrocarbon by a diluting gas to lead out the same, a dilution ratio adjusting means capable of adjusting the dilution ratio of the dilution device and a soot detector for continuously measuring soot in the gas diluted by the dilution device while the SOF measuring system is constituted so as to be capable of being connected to the dilution device to measure the concentration of hydrocarbon of the standard gas diluted by the dilution device. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust gas analyzer used for, for example, continuous measurement of particulate matter (PM) contained in exhaust gas of a diesel engine of a vehicle.

  The exhaust gas of an internal combustion engine such as a diesel engine contains minute particulate matter (PM) that may adversely affect the environment and the human body. PM includes soot, Soluble organic solvent (SOF: Soluble Organic Fraction) etc. are mixed.

  In order to improve the internal combustion engine in order to reduce this PM, it is first necessary to correctly measure the PM emission amount. In the exhaust gas measurement method currently officially defined, PM is collected by a filter and measured with a balance.

  However, with this measurement method, the generated PM cannot be dynamically captured. Therefore, in the development research stage of the internal combustion engine, a simple measurement device capable of continuous real-time measurement of PM is desired. Furthermore, recently, the improvement of the internal combustion engine has progressed and the amount of PM emission has been considerably reduced. Therefore, in addition to continuous measurement, there is an increasing demand for measuring a minute amount of PM accurately and accurately.

In contrast, recently, with regard to SOF, exhaust gas is detected at a reference temperature (47 ° C. ± 5 ° C.) by using a highly sensitive detector for hydrocarbons such as a flame ionization detector (FID). A method capable of continuously and accurately measuring the concentration of particulate hydrocarbon (SOF) liquefied or solidified in a gas has been developed.
As for Soot, the present inventors are developing a Soot detector capable of continuous measurement and utilizing a diffusion charge detection method and having high sensitivity.

  By the way, such a soot detector needs to dilute the exhaust gas appropriately to a concentration suitable for measurement because of its high sensitivity. Further, in order to calculate the soot concentration of the original exhaust gas from the soot concentration of the diluted exhaust gas thus measured, it is necessary to grasp the dilution ratio.

However, in order to obtain this dilution ratio, it is easy to measure the flow rate of the exhaust gas before dilution and the flow rate of the exhaust gas after dilution using a venturi flow meter or the like and calculate from the flow rate ratio. The conceivable configuration makes the apparatus large and disadvantageous in terms of cost.
JP-A-9-5299

  Therefore, the present invention has been made paying attention to measuring both the SOF concentration and the Soot concentration at the time of PM measurement. By using this SOF measurement system, a simple and low-cost configuration is achieved. Thus, it is intended to obtain a necessary dilution ratio when measuring the Soot concentration.

That is, the exhaust gas analyzer according to the present invention has the following requirements.
(1) An exhaust gas line through which a part or all of exhaust gas discharged from an internal combustion engine flows is connected to an SOF measurement system capable of continuously measuring SOF concentration and a soot measurement system capable of continuously measuring soot. It is.
(2) The Soot measurement system is
a) A diluter for selectively diluting one of the exhaust gas and the standard gas having a known hydrocarbon concentration with a diluting gas b) Dilution ratio adjusting means capable of adjusting the dilution ratio of the diluter c) A soot detector that continuously measures soot in the gas diluted by the diluter is provided. (3) The SOF measurement system is configured to be connectable to the diluter and diluted by the diluter. Make the hydrocarbon concentration of the standard gas measurable, and the dilution ratio of the diluter in that state can be calculated from the hydrocarbon concentration after dilution of the standard gas when the dilution ratio adjustment means is operated by a certain amount It is configured.

  If this is the case, branch the pipe from the diluter and connect it to the existing SOF measurement system, connect the pipe for connecting the standard gas source to the diluter, or open / close valves on these pipes The dilution ratio of the diluter at the time of soot measurement can be obtained by using a standard gas before or after the soot measurement, by configuring a simple fluid path. The soot concentration in the exhaust gas before dilution can be calculated from the soot concentration of the diluted exhaust gas detected by the soot detector.

  Since the soot flows through the diluter, if the fluid path inside the diluter has a complicated shape, the soot may become clogged and cause a problem. Further, if there is a pulsation or the like in the flow rate during dilution, it may cause a measurement error in the Soot detector. Therefore, in order to make a diluter that has a simple structure and does not cause pulsation or the like during dilution, the diluter is provided with a narrow portion whose flow path diameter is narrowed from the middle, and this is achieved by passing dilution gas through the narrow portion. It is preferable that the gas is accelerated to a negative pressure, and the exhaust gas or the standard gas is sucked by the negative pressure and mixed with the dilution gas. It is better from the point of mixing if the narrow portion is provided with an expanded portion in series downstream of the narrow portion.

  As a specific embodiment of the dilution ratio adjusting means, there may be mentioned one using a pressure regulator for adjusting the pressure of the dilution gas introduced into the diluter.

  As a soot detector capable of continuous measurement with high sensitivity, a soot detector provided with a charge imparting section for applying a charge to the soot and a charge measuring section for measuring a charge amount of the soot can be cited.

  The SOF measuring system suitable for the Soot measurement according to the present invention includes a branched portion that divides the introduced gas into two branches, and one of the two branched gases is used as a reference temperature for SOF measurement. A particle component removal line for removing the particle component of the gas, a passage line for allowing the other branched gas to pass through as it is (the temperature may be changed), and hydrocarbons in the gas sent through each line And a hydrocarbon concentration detector that continuously detects the concentration, and the concentration of SOF in the exhaust gas can be calculated based on the difference in the hydrocarbon concentration detected by each detector. Here, the particle component refers to hydrocarbon particles that are mainly liquefied or solidified in a gas.

  Particularly preferably, the hydrocarbon concentration detector may be a flame ionization detector. When the SOF measurement system is configured using this flame ionization detector, if the output of the flame ionization detector on the passage line side is converted to a time series graph, soot is detected as a spike-like peak. The soot concentration measured by the soot measurement system can be verified.

  In order to measure the soot concentration in the exhaust gas using the exhaust gas analyzer according to the present invention, the hydrocarbon concentration of the diluted standard gas is measured by the SOF measurement system, and the concentration and the standard before dilution are measured. The dilution ratio in the diluter is calculated based on the ratio to the hydrocarbon concentration of the gas, and the correlation between the dilution ratio and the operation amount is obtained based on the operation amount of the dilution ratio adjusting means at that time. The dilution ratio adjusting means is operated by the operation amount obtained from the correlation so as to obtain a desired dilution ratio in step 1, or from the correlation between the operation amount of the dilution ratio adjusting means set at the time of the soot measurement and the correlation. The soot concentration in the exhaust gas may be calculated based on the dilution ratio and the measurement result of the soot detector.

  As described above, according to the present invention, by using the SOF measurement system used in combination with the soot measurement system in the PM measurement, it is possible to measure the soot concentration with high accuracy only by configuring a simple fluid path. The exhaust gas dilution ratio required for the above can be obtained accurately.

  Hereinafter, an exhaust gas analyzer according to an embodiment of the present invention will be described with reference to the drawings.

(1) Overall Configuration of Exhaust Gas Analyzer The exhaust gas analyzer 1 according to the present embodiment measures mass concentrations of SOF and Soot contained in exhaust gas of a diesel engine (not shown) that is an internal combustion engine. Yes, as shown in FIG. 1, an SOF measurement system 2 capable of continuously measuring SOF concentration and soot continuously for an exhaust gas line (not shown) through which part or all of exhaust gas discharged from a diesel engine flows. A soot measurement system 3 that can be measured is connected in parallel.

(2) SOF measurement system First, the SOF measurement system 2 will be described.
As shown in FIG. 1, the SOF measurement system 2 includes a branch portion 21 that divides exhaust gas introduced from an exhaust gas line into two branches, and a passage line 22 into which exhaust gas branched into two at the branch portion 21 is introduced. And a particle component removal line 23 and hydrogen flame ionization detectors 24a and 24b connected to the ends of the lines 22 and 23 via pumps Pa and Pb, respectively.

  The branch portion 21 is formed by using a manifold block 25 having a fluid path that branches into two inside, and the exhaust gas line is connected to a predetermined temperature (about 191) at a gas introduction port PT1 that is an inlet thereof. And a temperature control pipe L such as a hot hose, a particulate matter removal filter F, etc. A temperature controller H1 such as a temperature-adjustable heater is attached to the manifold block 25, and is kept at the predetermined temperature (about 191 ° C.), for example.

  The particulate component removal line 23 changes the exhaust gas flowing inside to 47 ° C. ± 5 ° C., which is a measurement reference temperature defined by the EPA regulations in 2007, and hydrocarbon (SOF) that is liquefied or solidified at that temperature. The exhaust gas after removal is sent to the flame ionization detector 24b.

  Specifically, this is connected to the gas introduction port PT1 via the manifold block 25, the first temperature control pipe L1 kept at the measurement reference temperature, and the filter F1 connected to the end of the first temperature control pipe L1. And the 2nd temperature control piping L2 which guides the gas which passed the filter F1 to one hydrogen flame ionization detector 24b. The second temperature control pipe L2 is kept at the predetermined temperature (about 191 ° C.), for example.

  The passage line 22 sends exhaust gas having a predetermined temperature higher than the measurement reference temperature, specifically 191 ° C., directly to the flame ionization detector 24a. The passage line 22 is connected to the gas introduction port PT1 via a manifold block 25. And a third temperature control pipe L3 connected thereto. The third temperature control pipe L3 is maintained at the predetermined temperature (about 191 ° C.) and is connected to the other hydrogen flame ionization detector 24a.

  The hydrogen flame ionization detectors 24a and 24b detect the concentration of hydrocarbons contained in the sample gas (exhaust gas in the above-described case) continuously and in real time. By flowing a sample gas (exhaust gas in this case), hydrocarbons in the sample gas are ionized, and the ion current is detected and output. The value of the output detection signal indicates the hydrocarbon concentration.

  According to such a configuration, the baseline value of the detection signal of the flame ionization detector 24a connected to the passage line 22 is the concentration of hydrocarbon in a gaseous state at the predetermined temperature (191 ° C.). The baseline value of the detection signal of the flame ionization detector 24b connected to the particle component removal line 23 indicates the concentration of hydrocarbon vaporized at the measurement reference temperature (47 ° C. ± 5 ° C.). By taking the difference in the value of the detection signal from each flame ionization detector 24a, 24b, the concentration of hydrocarbon condensed from gas to liquid or solid between 191 ° C. and 47 ° C. ± 5 ° C., that is, in the exhaust gas The SOF concentration can be measured.

  In this embodiment, the information processing device (not shown) receives the hydrocarbon detection signals from the respective flame ionization detectors 24a and 24b, and takes the difference between the values indicated by the hydrocarbon detection signals to obtain the SOF concentration. Is calculated and output to a display or the like.

(3) Soot Measurement System Next, the soot measurement system 3 will be described.

  As shown in FIG. 1, the soot measurement system 3 includes a diluter 4 that extracts exhaust gas by diluting it with air that is a dilution gas, and a soot detector 5 that detects the soot of the diluted gas. Is.

  As shown in detail in FIGS. 2 and 3, the diluter 4 has a nozzle 42 that is a narrow portion in which the flow path diameter narrows along the gas flow direction on the internal main path 41 through which the dilution gas flows, and the gas A diffuser 43, which is an expanded portion in which the flow path diameter expands along the flow direction, is provided in series in this order to form a negative pressure region 4S in which the dilution gas is accelerated and becomes negative pressure, and in the negative pressure region 4S This is an ejector type that sucks a sample gas through the communicating passage 44 and communicates it with the dilution gas. In this embodiment, the nozzle and the diffuser are used for the narrow portion and the widened portion, but various types such as an orifice and a venturi can be substituted.

  More specifically, the diluter 4 includes a pipe block body 4a provided with a communication path 44 communicating with the main path 41 and the negative pressure region 4S, and a nozzle that is fitted into the main path 41 to form the nozzle 42 and the diffuser 43. The pipe connection joint C2 provided in the member 42a and the diffuser member 43a, the introduction port PT2 that is the inlet of the main path 41, the outlet port PT3 that is the outlet, and the sample gas introduction port PT4 that is the inlet of the communication path 44, respectively. , C3, and C4.

  As shown in FIG. 1, a dilution gas line 6 through which a dilution gas flows is connected to the introduction port PT2, so that air as a dilution gas is introduced, and a sample gas introduction port PT4 is provided. Is connected to the exhaust gas line. In addition, a soot detector 5 (to be described later) is connected to the outlet port PT3 via a pipe L4 so that the diluted gas can be sent to the soot detector 5.

  A dilution gas source (not shown) such as a compressor or a cylinder is connected to the dilution gas line 6 at its starting end, and a pressure regulator 7 as dilution ratio adjusting means is provided on the line 6. It is provided so that the air pressure flowing into the introduction port PT2 can be controlled to adjust the dilution ratio.

  Specifically, as shown in FIG. 4, the operation range of the pressure adjuster 7, that is, the pressure adjustment range is changed even if the flow rate of the dilution gas introduced into the diluter 4 is changed by the pressure adjustment. 4 is limited so that the suction flow rate of the sample gas is kept in a substantially constant range.

  Further, the diluter 4 is connected in a plurality of stages (two stages) in series, and the outlet port PT3 of the pre-stage diluter 4 is connected to the sample gas introduction port PT4 of the post-stage diluter 4 so that a multi-stage dilution can be performed. It is configured. This makes it possible to change the dilution rate at the order level depending on which diluter 4 outlet port PT3 is used.

  Further, as shown in FIG. 3 in particular, an orifice ring 44a as a flow restricting member is attached to at least the communication passage 44 of the first stage diluter 4 in a replaceable manner.

  Furthermore, a temperature controller H2 such as a heater capable of adjusting the temperature is attached to the piping block body 4a so that the diluter 4 is maintained at a predetermined temperature (about 191 ° C.). This is for volatilizing SOF and the like (especially SOF adhering to the soot) contained in the exhaust gas to prevent an adverse effect on the soot measurement by the soot detector 5 described later. In addition, since the soot detector 5 is of a type that cannot introduce high-temperature gas, the temperature of the diluted exhaust gas is lowered during passage through the pipe L4 from the outlet port PT3 of the diluter 4 to the soot detector 5. However, once volatilized SOF is diluted even if the temperature is lowered, it does not reprecipitate as particles that affect the measurement.

  Further, the portion directly connected to the introduction port PT2 in the dilution gas line 6 is maintained at the predetermined temperature (about 191 ° C.) using the fourth temperature control pipe L5, and the supplied air flow rate is stabilized. I am trying.

  As shown in the schematic diagram of FIG. 4, the soot detector 5 includes a charge imparting unit 51 that gives a charge to the soot contained in the sample gas, and a charge measuring unit 52 that measures the charge amount of the soot. The soot in the diluted exhaust gas introduced as the sample gas is measured continuously and in real time.

  The charge imparting unit 51 is provided on the flow path 53 of the introduced diluted exhaust gas. For example, a positive electrode 511 and a negative electrode 512 that generate a potential difference of about several thousand volts (5000 to 7000 volts) It consists of Corona discharge is generated between the electrodes 511 and 512 due to the potential difference, and when the diluted exhaust gas passes through the corona discharge, the Soot particles in the diluted exhaust gas are given a charge proportional to the surface area. As shown in the figure, the positive electrode 511 is a pin-shaped, thin shape located at the center of the flow path 53, and the negative electrode 512 is a cylindrical mesh member disposed so as to surround the positive electrode 511. . In addition, you may make this charge provision part another structure, such as providing a charge by ultraviolet irradiation.

  The charge measuring unit 52 measures a capture member 521 such as a metal plate disposed downstream of the charge imparting unit 51 in the flow channel 53 and the amount of current that flows when the soot is captured by the capture member 521 and the value is measured. And a current detector 522 that outputs a soot detection signal. The value of the soot detection signal represents the surface area of the soot particle because the soot charge amount is proportional to the surface area of the soot particle. Further, since there is a predetermined relational expression between the soot surface area and the soot mass, the soot mass and thus the soot concentration in the diluted exhaust gas can be calculated from the value of this detection signal.

  By the way, what is ultimately required is the soot concentration of the exhaust gas before dilution, and in order to measure this, in addition to the measurement data of the soot concentration in the diluted exhaust gas, the dilution ratio in the diluter 4 must be grasped. I must.

Therefore, in this embodiment, as shown in FIG. 1, the standard gas line 8 in which a standard gas having a known hydrocarbon concentration (for example, C ₃ H ₈ containing air) flows into the sample gas introduction port PT4 of the diluter 4 is exhausted. In addition to being able to be switched and connected to the gas line, the outlet port PT3 of the diluter 4 is configured to be switched and connected to the gas introduction port PT1 of the SOF measurement system 2 and the exhaust gas line.

  More specifically, by providing an on-off valve V2 on the pipe L6 of the standard gas line 8 for the sample gas introduction port PT4 of the diluter 4, the sample gas introduction port PT4 between the standard gas line 8 and the exhaust gas line. The connection to can be switched. The standard gas line 8 is connected to a standard gas source (cylinder or the like) at the inlet, and a pressure regulator 81 is provided on the line 8 to keep the downstream line pressure constant, A flow meter 82 is provided so that the flow rate of the standard gas introduced into the sample gas introduction port PT4 can be monitored.

  Further, an open / close valve V3 is provided on the connection pipe L7 from the outlet port of the diluter 4 to the gas introduction port PT1 of the SOF measurement system 2, and the open / close valve V4 is provided on the connection pipe of the exhaust gas line to the gas introduction port PT1. By selectively opening these on-off valves V3 and V4, either the outlet port PT3 of the diluter 4 or the exhaust gas line can be switched and connected to the gas introduction port PT1.

  According to such a configuration, the hydrocarbon concentration of the diluted standard gas is measured by SOF measurement by flowing the standard gas diluted by the diluter 4 to the SOF measurement system 2 by operating the on-off valves V3 and V4. It can be measured by any of the flame ionization detectors 24a, 24b of the system 2. Then, from the measured hydrocarbon concentration and the originally known hydrocarbon concentration of the standard gas, the dilution ratio at that time of the diluter 4 can be obtained. The dilution ratio and the soot of the diluted exhaust gas described above can be obtained. The soot concentration of the exhaust gas can be calculated from the concentration.

  In this embodiment, an information processing device (not shown) receives the soot detection signal and the hydrocarbon detection signal output from the flame ionization detector 24a (24b) when the diluted standard gas is flowed, Based on this value and the value of the known concentration data of the standard gas stored in advance in the memory, the Soot concentration is automatically calculated and output to a display or the like. The on-off valves V2 to V4 are electromagnetically driven, and are opened / closed by a valve drive signal from the information processing apparatus.

(4) Usage Method of Exhaust Gas Analyzer Next, an example of the soot concentration measuring method using the exhaust gas analyzer 1 will be described more specifically. Here, the case where the information processing apparatus measures the Soot concentration automatically in accordance with a program will be described with reference to FIGS.

(Create a calibration curve)
First, valve drive signals are output to the on-off valves V2 to V4 to open and close them, and the standard gas is introduced into the SOF measurement system 2 through the diluter 4 (step S1 in FIG. 6).
On the other hand, a drive signal is given to the pressure regulator 7 so that the air introduced into the diluter 4 is kept at a predetermined pressure (step S2).
In such a state, the hydrocarbon ion concentration of the diluted standard gas is measured by the flame ionization detector 24a (24b) (step S3).
Then, the dilution ratio in the diluter 4 is calculated by the ratio between the concentration and the hydrocarbon concentration of the standard gas before dilution (step S4), and the dilution ratio and the air pressure are recorded as a pair (step S4). S5).
Next, the drive signal value for the pressure regulator 7 is changed to change the pressure set value, and steps S3 to S5 are repeated a plurality of times (n times) (step S7).
A calibration curve (relative relationship) between pressure and dilution ratio is created from the relationship between pressure values and dilution ratios measured at a plurality of points in this way, and stored in a predetermined area of the memory (step S8).

(Soot concentration measurement)
First, the on-off valves V2 to V4 are opened and closed to introduce exhaust gas into the soot measurement system 3 (step S10 in FIG. 7).
Since the soot concentration of the exhaust gas is unknown, the drive signal value to the pressure regulator 7 is changed while referring to the value of the soot detection signal from the soot detector 5, and the dilution gas line 6 is suitable for soot measurement. The pressure is set so as to be the same pressure (steps S11 and S12).
The dilution ratio at that time is calculated from the set pressure value and the calibration curve (step S13).
A predetermined relational expression stored in the memory is applied to the value of the soot detection signal to determine the soot concentration in the diluted exhaust gas (step S14).
Finally, the Soot concentration in the exhaust gas is calculated based on the Soot concentration and the dilution ratio (Step S15).

  The above is the Soot concentration measurement method. In addition, for example, without creating a calibration curve, the dilution ratio at the pressure setting value of the dilution gas at that time is calculated using the standard gas each time the Soot measurement is performed. The Soot concentration may be calculated based on the dilution ratio.

  Further, all of the above operations may be performed manually by an operator, or a part of the operations may be performed automatically and a part of the operations may be performed manually.

  Therefore, according to such an exhaust gas analyzer 1, a pipe is branched from the diluter 4 and connected to the existing SOF measurement system 2, or a pipe for connecting a standard gas source is connected to the diluter 4. Or by providing a simple fluid path such as providing on-off valves V2 to V4 on the pipes, the dilution ratio of the diluter 4 at the time of soot measurement can be changed to the standard gas before the soot measurement or after the soot measurement. The soot concentration of the exhaust gas before dilution can be calculated from the dilution ratio and the soot concentration of the diluted exhaust gas detected by the soot detector.

The present invention is not limited to the above embodiment. For example, the hydrocarbon detector and the soot detector may use other principles, and exhaust gas diluted by a full tunnel may be introduced to the exhaust gas line.
Further, the diluter may have a one-stage dilution structure or a three-stage or more dilution structure. In other words, not only the ejector type but also other types such as a rotary pump type may be used.
Further, the dilution ratio adjusting means may use not only a pressure regulator but also a flow rate adjusting valve such as a valve.
In addition, it goes without saying that the present invention can be variously modified without departing from the gist of the present invention, such as a three-way valve.

  According to the present invention, the concentration of soot in exhaust gas can be measured continuously with high accuracy with a simple and compact configuration, and the research and development of an internal combustion engine such as an automobile can be facilitated.

1 is an overall fluid circuit diagram of an exhaust gas analyzer according to an embodiment of the present invention. Sectional drawing which shows the internal structure of the diluter in the embodiment. The expanded partial sectional view which mainly shows the nozzle of the diluter, the diffuser, and the orifice in the same embodiment. Sectional drawing which shows the internal structure of the diluter in the embodiment. The graph which shows the characteristic of the diluter in the embodiment. The flowchart which shows the Soot measuring method using the exhaust-gas analyzer in the same embodiment. The flowchart which shows the Soot measuring method using the exhaust-gas analyzer in the same embodiment.

Explanation of symbols

2 ... SOF measurement system 21 ... branching part 22 ... passage line 23 ... particle component removal lines 24a, 24b ... SOF concentration detector 3 ... Soot measurement system 4 ... diluter 42 ... Nozzle 43 ... Diffuser 5 ... Soot detector 51 ... Charge application unit 52 ... Charge measurement unit 7 ... Dilution ratio adjusting means (pressure regulator)

Claims (6)

An exhaust gas line through which part or all of the exhaust gas discharged from the internal combustion engine flows is connected to an SOF measurement system capable of measuring the SOF concentration and a soot measurement system capable of measuring the soot,
The Soot measurement system can adjust the dilution ratio of the diluter and the diluter for selectively diluting either the exhaust gas or the standard gas having a known hydrocarbon concentration with a diluting gas. A dilution ratio adjusting means and a soot detector for measuring soot in the gas diluted by the diluter are provided.
The SOF measurement system is configured to be connectable to the diluter so that the hydrocarbon concentration of the standard gas diluted by the diluter can be measured.
Exhaust gas analysis characterized in that the dilution ratio of the diluter in that state can be calculated from the hydrocarbon concentration after dilution of the standard gas when the dilution ratio adjusting means is operated by a certain amount apparatus.   The diluter includes a narrow portion where the flow path diameter is narrowed and a widened portion which is provided in series with the narrow portion and the flow path diameter is widened, and by passing dilution gas through the narrow portion and the widened portion. The exhaust gas analyzer according to claim 1, wherein the exhaust gas analyzer is accelerated to a negative pressure, and the negative pressure sucks exhaust gas or standard gas and mixes it with the dilution gas.   3. The exhaust gas analyzer according to claim 2, wherein the dilution ratio adjusting means is a pressure adjuster that adjusts the pressure of the dilution gas introduced into the diluter.   The exhaust gas analyzer according to any one of claims 1 to 3, wherein the soot detector includes a charge imparting unit that applies a charge to the soot and a charge measuring unit that measures a charge amount of the soot. . The SOF measurement system is
A branching portion for branching the introduced gas into two branches;
A particle component removal line for setting one of the two branched gases to a measurement reference temperature for SOF measurement and removing the particle component in the gas at the measurement reference temperature;
A passage line through which the other branched gas passes,
A hydrocarbon concentration detector for continuously detecting the hydrocarbon concentration in the gas sent through each line,
The exhaust gas analyzer according to any one of claims 1 to 4, wherein the exhaust gas analyzer is configured to be able to calculate the concentration of SOF in the exhaust gas based on a difference in hydrocarbon concentration detected by each detector. A soot measurement method using the exhaust gas analyzer according to any one of claims 1 to 5,
Measure the hydrocarbon concentration of the diluted standard gas with the SOF measurement system,
Based on the ratio between the concentration and the hydrocarbon concentration of the standard gas before dilution, calculate the dilution ratio in the diluter.
Based on the operation amount of the dilution ratio adjusting means at that time, while obtaining the correlation between the dilution ratio and the operation amount,
Operate the dilution ratio adjusting means by an operation amount obtained from the correlation so as to obtain a desired dilution ratio at the time of soot measurement, or the operation amount of the dilution ratio adjusting means set at the time of soot measurement and the correlation. To obtain the dilution ratio at that time,
A soot measurement method, wherein a soot concentration of exhaust gas is calculated based on the dilution ratio and a measurement result by a soot detector.