JP4413160B2 - Exhaust gas component analyzer - Google Patents

Description

  The present invention relates to a multi-component gas analyzer for analyzing various components contained in vehicle exhaust gas and the like.

Conventionally, various gas analyzers are used for measuring components of exhaust gas discharged from vehicles such as automobiles. For example, as shown in Patent Document 1, an infrared gas analyzer is used to measure the concentration of CO and CO ₂ , and a chemiluminescent nitrogen oxide analyzer is used to measure the NO _X concentration. It has been. Also, a flame ionization analyzer that measures THC (Total Hydro Carbon) concentration is well known.

In these analyzers, due to the method, other components in the exhaust gas interfere with or quench the measurement target component, resulting in an error in the measurement result. Therefore, for example, in an infrared gas analyzer, an interference correction detector is separately provided inside. Further, in the chemiluminescent nitrogen oxide analyzer, in order to reduce quenching with CO ₂ and H _{2 O,} or less flow rate of the exhaust gas capturing, or to dilute the exhaust gas in advance, or the degree of vacuum The idea of raising it is made.

  However, in the chemiluminescent nitrogen oxide analyzer, when interference due to multiple components occurs, a large number of interference correction detectors must be provided for each component, and the configuration becomes complicated. In addition, when the exhaust gas flow rate is reduced or diluted in a chemiluminescent nitrogen oxide analyzer, the sensitivity and accuracy are lowered, and the measurement responsiveness is also affected. Increasing the vacuum requires a large vacuum pump.

And these troubles, that is, the complexity and enlargement of the configuration, or the reduction of measurement sensitivity, measurement accuracy, and responsiveness, are considered when developing an exhaust gas analyzer that can be mounted on a vehicle and can perform continuous real-time measurement. It becomes a big neck.
JP-A-11-230869

  Accordingly, the present invention is intended to solve these problems all at once, and to provide an exhaust gas analyzer that can achieve compactness and power saving, has high sensitivity, and can perform continuous real-time measurement.

  That is, the exhaust gas analyzer according to the present invention includes a main flow path into which exhaust gas discharged from an internal combustion engine is continuously introduced in time series, and one or more branched from the main flow path and provided in parallel to the main flow path. Sub-channels, analyzers provided on the main channel and the sub-channel, respectively, for measuring the concentrations of a plurality of components to be measured in the exhaust gas in time series, and the exhaust gas to each analyzer An actual measurement value acquisition unit that acquires the actual measurement value of the target component concentration in the exhaust gas exhausted at the same time based on the difference in time to reach, and the mutual influence of the measurement target component. And a correction unit that corrects a deviation from a true value occurring in a part or all based on a part or all of each actual measurement value.

If this is the case, it is necessary to provide a dedicated correction detector in order to mutually correct the influence of interference, quenching, etc. between target components measured by each analyzer using the measured values. Therefore, the device can be made more compact and power can be saved.
Specific examples of exhaust gas measurement target components include at least CO, CO ₂ , H ₂ O, and THC. In that case, the analyzer preferably includes an infrared gas analyzer that measures CO concentration, CO ₂ concentration, and H ₂ O concentration, and a hydrogen flame ionization analyzer that measures THC concentration. Then, the correction unit intermediately corrects the measured values of the CO concentration, the CO ₂ concentration, and the H ₂ O concentration based on the measured value of the THC concentration by the hydrogen flame ionization analyzer, and the CO and CO ₂ concentrations. It is desirable to further correct the intermediate correction value of the CO and CO ₂ concentration based on the intermediate correction value and the intermediate correction value of the H ₂ O concentration.

If it is such, since the dehumidifier and hot hose for reducing the influence of moisture interference can be eliminated or reduced in size, the apparatus can be made compact and power can be saved. Furthermore, since the deviation of the exhaust gas arrival time to each analyzer is corrected, the measurement accuracy can be ensured. Further, since the H ₂ O concentration is also measured by the infrared gas analyzer, a dedicated H ₂ O concentration meter is not required.

If the measurement target component further includes NO _{X and} further includes a chemiluminescent nitrogen oxide analyzer that measures the NO _X concentration, the correction unit can measure the measured value of the NO _X concentration in the CO 2. it is sufficient to configured to correct, based on the final correction value of ₂ concentration and H _{2 O} concentration.

This eliminates the need to reduce the flow rate of exhaust gas taken in to reduce quenching by CO ₂ or H ₂ O or dilute the exhaust gas in advance in the chemiluminescent nitrogen oxide analyzer. Therefore, the exhaust gas introduction flow rate into the chemiluminescent nitrogen oxide analyzer can be increased at a stretch, and the sensitivity and responsiveness can be improved. Further, since a high vacuum is not required, the size of the vacuum pump can be reduced.

  Furthermore, if this infrared gas analyzer is arranged on the main flow path (bypass path) by utilizing the fact that the exhaust gas flow rate to the infrared gas analyzer can be increased, a dedicated flow path for the infrared gas analyzer can be eliminated. This point can also contribute to the downsizing of the apparatus.

  If a sub-channel that branches from the main channel is provided, and a chemiluminescent nitrogen oxide analyzer and a flame ionization analyzer are provided on the sub-channel, exhaust gas is introduced into each analyzer as soon as possible and simultaneously as soon as possible. The concentration of the target component in the exhaust gas can be continuously measured with high responsiveness and accuracy.

  In order to reduce the number of vacuum pumps as much as possible, it is preferable that the downstream ends of the main flow path and the sub flow path are sucked by a common pump.

  As a result, it becomes possible for the first time to realize an exhaust gas analyzer that is capable of continuous real-time measurement on a vehicle and has excellent measurement accuracy.

  As described above, according to the present invention, a flow path system for continuous time series measurement without diluting a plurality of gas concentrations can be configured as easily as possible, and compactness and power saving can be achieved. In addition, it is possible to provide an exhaust gas analyzer that is excellent in accuracy, responsiveness, good sensitivity, and capable of continuous real-time measurement.

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

  The exhaust gas analyzer 100 according to the present embodiment is capable of measuring various component concentrations in exhaust gas while being loaded on a trunk of a vehicle and actually running the vehicle, as shown in FIG. Three different analyzers 4, 5, 6, a flow path system for continuously supplying exhaust gas to these analyzers 4, 5, 6, and measured data from each analyzer 4, 5, 6 An information processing device 7 that receives and analyzes and calculates a true measurement value and controls a valve and the like disposed in the flow path system is provided.

  Each part will be described in detail.

In this embodiment, the analyzers 4, 5, and 6 are an infrared gas analyzer 4 for measuring the concentration of CO, CO ₂ , and H ₂ O, a flame ionization analyzer 5 for measuring the concentration of THC, and NO. Three chemiluminescent nitrogen oxide analyzers 6 (hereinafter also referred to as CLD type NO _X meters 6) for measuring the concentration of _X are used.

Infrared gas analyzer 4 is of a _{non-distributed, CO, CO 2, H 2} O is passed by irradiating infrared characteristic wavelength absorbing each sample gas (the exhaust gas), of each wavelength at this time The light intensity is measured by a photodetector and output. Then, by comparing the output value with a reference value when there is no light absorption, it is possible to calculate the absorbance of light of each wavelength. Since the light absorbance corresponds to the concentration (amount) of each measurement target component, the concentration (amount) of CO, CO ₂ , H ₂ O can be specified from this, but CO, CO ₂ , H ₂ O Since the THC interferes with each other and CO and CO ₂ interfere with each other and H ₂ O also interferes with each other, the values of the respective light absorptions are simply CO, CO ₂ , H ₂ O. There is no one-to-one correspondence with the density of the.

  The flame ionization analyzer 5 mixes and burns a sample gas (exhaust gas) with a fuel gas (hydrogen gas) at a certain ratio, and THC contained in the sample gas is ionized at that time. This is a method of detecting and outputting a value, and the amount (concentration) of THC can be calculated from the current value. The hydrogen flame ionization analyzer 5 is configured such that an auxiliary combustion gas (air) is introduced in addition to the fuel gas.

The CLD type NO _X meter 6 converts all NO _X contained in the exhaust gas into NO by the NO converter 61 and mixes the NO with the ozone output from the ozone generator 62 in the reaction tank 63 to cause a chemical reaction. The intensity of luminescence generated by the reaction at that time is detected by a photodetector (not shown) and output. Since the emission intensity corresponds to the concentration (amount) of NO, the concentration (amount) of NO can be specified from this. However, since CO ₂ and H ₂ O inhibit the luminescence phenomenon during the reaction (quenching), the concentration of NO cannot be calculated immediately from the value of the luminescence intensity.

In this embodiment, in addition to the path 6a that leads the exhaust gas directly to the reaction tank 63 and in parallel to the path 6a that leads to the reaction tank 63 via the NO converter 61, the path that leads the exhaust gas directly to the reaction tank 63. 6b are provided in parallel. Then, the gas is selectively guided to the reaction vessel 63 only from one of the paths 6a and 6b by the valve 65, and NO is obtained by taking the concentration of NO alone or the difference in the exhaust gas. and to be able to measure also the concentration of the NO _X except. The ozone generator 62 takes in the air as it is without dehumidifying it. Reference numeral 64 denotes an ozone remover.

The flow path system includes a main flow path 1 that serves as a bypass path through which most of exhaust gas passes, and a plurality (two) of sub flow paths 2 and 3 that are branched from the main flow path 1 and provided in parallel. The infrared gas analyzer 4 on the main flow path 1, the hydrogen ionization analyzer 5 on the one sub flow path 2 (first sub flow path 2), and the other sub flow path 3 (second flow path 2). A CLD type NO _X meter 6 is provided on each sub-flow path 3).

  The main channel 1 has an upstream end opened as a main port 11, and a suction pump 19 is disposed on the most downstream side. Then, an exhaust pipe of a vehicle is connected to the main port 11 and sucked by the suction pump 19 so that an amount necessary for measurement of the exhaust gas is introduced into the main flow path 1. .

  More specifically, a drain separator 13 for removing liquid water contained in the exhaust gas, a filter 14, a flow control pipe (capillary) 15a, and a branching section 16 are provided on the main flow path 1 following the main port 11. The infrared gas analyzer 4, the flow rate control tube (capillary) 15b, the merging portion 18, and the suction pump 19 are arranged in this order in series. From the exhaust pipe of the vehicle to the drain separator 13, at least the heating pipe is not used and only the non-heated pipe is connected, so that each analyzer 4, 5, 6 has only liquid water in the drain separator 13. Exhaust gas in a removed state (hereinafter also referred to as semi-Dry state) is introduced. The pressure control valve 17a connected downstream of the infrared gas analyzer 4 is for controlling the pressure of the flow path system between the capillaries 15a and 15b. It plays a role of keeping the flow rate and pressure of the exhaust gas flowing through the gas analyzer 4 constant.

  On the other hand, the sub-channels 2 and 3 are configured to be branched from the main channel 1 at the branching portion 16 and reconnected to the main channel 1 at the junction 18.

  On the first subchannel 2, a flow rate control tube (capillary) 21 and a hydrogen flame ionization analyzer 5 are provided in this order. The flow rate control pipe 21 limits the amount of gas flowing through the sub-flow channel 2 to a flow rate necessary for measuring the concentration of THC (which is very small compared to the exhaust gas flow rate flowing through the main flow channel 1).

On the second sub-channel 3, the flow control tube (capillary) 31, CLD type NO _X analyzer 6 are arranged in this order from the upstream. The flow rate control pipe (capillary) 31 restricts the amount of gas flowing through the sub-flow channel 3 to a flow rate necessary for measuring the concentration of NO _X (which is small compared to the exhaust gas flow rate flowing through the main flow channel 1). It is.

The pressure control valve 17b connected to the merging portion 18 is for controlling the pressure of each of the sub-channels 2 and 3, and the capillary 21 provided in the upstream portion of each of the sub-channels 2 and 3. responsible for maintaining the flow rate and pressure of the exhaust gas flowing through the 22 cooperating with flame ionization analyzer 5 and CLD type NO _X meter 6 constant.

  As shown in FIG. 2, the information processing apparatus 7 is a general-purpose or dedicated device including a memory 702, an input / output channel 703, an input means 704 such as a keyboard, a display 705, etc. in addition to the CPU 701. An analog-digital conversion circuit such as an A / D converter 706, a D / A converter 707, and an amplifier (not shown) is connected to 703.

  Then, the CPU 71 and its peripheral devices cooperate with each other in accordance with a program stored in a predetermined area of the memory 72, so that the information processing apparatus 7 is provided in the flow path system as shown in FIG. A control unit 71 that controls the opening and closing of the valves and the temperature control of the heater, an actual measurement value acquisition unit 72 that acquires actual measurement values of the analyzers 4, 5, and 6 with respect to the exhaust gas discharged at the same time At least the function as the correction unit 73 that corrects the deviation from the true value occurring in part or all of the actual measurement values is exhibited. Note that the information processing apparatus 7 does not need to be physically integrated, and may be divided into a plurality of devices by wire or wireless.

  Each function part 71-73 is demonstrated.

  The actual measurement value acquisition unit 72 samples and accepts output data from the analyzers 4, 5, and 6 at predetermined time intervals, and performs averaging processing, gain in the amplifier and detector, offset processing, etc. as necessary. These are stored as actual measurement data in the actual measurement data storage unit D1 set in a predetermined area of the memory in time series. The actual measurement value acquisition unit 72 stores in advance the time lag when the exhaust gas reaches the analyzers 4, 5, and 6, and the exhaust gas discharged at the same time based on the time lag. Each measured data relating to the gas is extracted from the measured data storage unit D1 and output. For example, when the measured data from the analyzers 4, 5, and 6 where the exhaust gas reaches the slowest is acquired, the measured data and the measured data related to the other analyzers 4, 5, and 6 are reached. The actual measurement data acquired earlier by the time difference is output.

  The correction unit 73 receives each actual measurement data output from the actual measurement value acquisition unit 72, and the values indicated by the actual measurement data, that is, the actual measurement values related to the respective measurement target components are based on a part or all of the actual measurement values. The correction data indicating the correction value is output. More specifically, it will be described below.

  First, the THC concentration will be described. The correction unit 73 performs zero / span calibration and linearization on the actual measurement value of the flame ionization analyzer 5, further performs pressure compensation and temperature compensation, and performs a semi-DRY state. The THC concentration at is calculated.

Next, the CO concentration, the CO ₂ concentration, and the H ₂ O concentration will be described.

The correction unit 73 performs first correction on the actual measurement value of the infrared gas analyzer 4 based on the THC concentration in the semi-DRY state calculated from the actual measurement value of the THC concentration as described above. The correction formula is as follows.
_{P CO = O CO -K HC (} CO) · [THCconc. (Vol%)]
P _CO2 = O _CO2 -K _{HC (CO2)} · [THC conc. (Vol%)]
P _H2O = O _H2O -K _{HC (H2O)} . [THC conc. (Vol%)]
O: Actual measurement value P: First correction value (correction value excluding THC interference)
K _HC : HC interference correction coefficient [THC conc. (Vol%)]: THC concentration (semi-DRY state)
* The subscript indicates a value related to CO, CO ₂ , and H ₂ O.

Next, in order to further correct the mutual interference effect between CO and CO ₂ , the first-corrected values of the CO concentration and the CO ₂ concentration are secondarily corrected based on the mutual values. The correction formula is as follows.
_{Q CO = (P CO -K CO2} (CO) · P CO2) / (1-K CO2 (CO) · K CO (CO2))
_QCO2 = ( _PCO2 - _{KCO (CO2) .PCO} ) / (1- _{KCO (CO2) .KCO2 (CO)} )
Q: secondary correction value (correction value excluding mutual interference between CO and CO ₂ )
K _{CO (} CO _{2 )} : interference correction coefficient by CO with respect to the actual measured value of CO K _{CO 2 (CO)} : interference correction coefficient with CO ₂ with respect to the actual measured value of CO

Thereafter, zero / span calibration and linearization are performed on Q _CO , Q _CO2 , and P _H2O thus obtained. The values (intermediate correction values) are S _CO , S _CO2 and S _H2O , respectively.

Next, with respect to the intermediate correction values S _CO and S _CO2 , the zero point moisture interference is corrected by using the intermediate correction value _SH2O . The correction formula is as follows.
_{T CO = S CO -K H2O0 (} CO) · S H2O
_{T CO2 = S CO2 -K H2O0 (} CO2) · S H2O
T: Value corrected for moisture interference at zero point K _{H2O0 (CO)} : Coefficient of water interference correction for CO K _{H2O0 (CO2)} : Coefficient of water interference correction for CO ₂

Furthermore, the moisture coexistence effect at the SPAN point is corrected. The correction formula is as follows.
_{U CO = T CO / (1} -K H2O1 (CO) · S H2O)
U _CO2 = T _CO2 / (1-K _{H2O1 (CO2)} · S _H2O )
U: Value corrected for moisture coexistence effect at span point K _{H2O1 (CO)} : CO moisture coexistence effect correction coefficient K _{H2O1 (CO2)} : CO ₂ moisture coexistence effect correction coefficient

Then, pressure compensation and temperature compensation are performed on the U _CO , U _CO2 , and S _H2O to calculate the concentrations of CO, CO _2, and H ₂ O in the semi-DRY state.

Next, the NO _X concentration will be described.

Correcting unit 73, the measured value of the CLD type NO _X meter 6, the measured value _{O NOX} of THC concentration obtained in flame ionization analyzer 5, the zero / span calibration, linearization applied.

Next, the value is subjected to quenching (quenching effect) correction by CO ₂ . The correction formula is as follows.
_{R NOX = Q NOX / (1} + K CO2 · [CO 2 conc. (Vol%)])
Q _NOX : A value obtained by _performing the zero / span calibration or the like on the actual measurement value _ONOX .
K _CO2 : CO ₂ interference (quenching) correction coefficient [CO ₂ conc. (Vol%)]: CO ₂ concentration (semi-DRY state)

Next, quenching (quenching effect) correction by H ₂ O is performed. The correction formula is as follows.
U _NOX = R _NOX / (1 + K H _{2 O.} [H ₂ Oconc. (Vol%)])
K _H2O : H ₂ O interference (quenching) correction coefficient [H ₂ Oconc. (Vol%)]: H ₂ O concentration (semi-DRY state)

Thereafter, the pressure compensation to the _{U NOX,} by performing temperature compensation, calculating the concentration of NO _X in the Semi-DRY state.

In this way, the correction unit 73 outputs the THC concentration, CO concentration, CO ₂ concentration, and NO _X concentration (final correction value) in the semi-DRY state obtained as described above.

  The information processing apparatus 7 further includes a WET conversion unit (not shown).

  The WET conversion unit calculates the concentration of each component in the DRY state in which moisture has been completely removed from the final correction value by request input from the operator, and further, the vehicle from the concentration of each component in the DRY state. The concentration of each component in the exhaust gas containing moisture immediately after exiting the exhaust pipe (exhaust gas in the WET state) is output.

The conversion formula for converting to the concentration in the DRY state is as follows.
X = W · 100 / (100− [H ₂ Oconc. (Vol%)])
W: Measurement target component concentration in the semi-DRY state X: Measurement target component concentration in the DRY state [H ₂ Oconc. (Vol%)]: H ₂ O concentration (semi-DRY state)

  In order to convert the concentration X in the DRY state into the concentration in the WET state, a DRY to WET conversion formula (details are omitted) described in CFR-1065 is applied.

  Thus, according to this embodiment, in order to mutually correct the interference and quenching of the target components measured by the analyzers 4, 5, and 6, using the measured values, a dedicated correction detector It is no longer necessary to provide a device, and the device can be made compact and power can be saved.

Further, the CLD type NO _X meter 6, or less flow rate of the exhaust gas taking for quenching reduction by CO ₂ and H _{2 O,} for or to dilute the exhaust gas in advance is not necessary, CLD The exhaust gas flow rate to the type NO _X meter 6 can be increased at once, and the sensitivity can be improved. Further, by utilizing the fact that the exhaust gas flow rate to the CLD type NO _X meter 6 can be increased, this CLD type NO _X meter 6 is arranged on the main flow path 1 (bypass path), and a dedicated flow path for the CLD type NO _X meter 6 In this respect, it is possible to contribute to the downsizing of the apparatus.

  Further, since a high vacuum is not required, the size of the vacuum pump 19 can be reduced, and capillaries 15a, 15b, 21, 31 and pressure control valves 17a, 17b are arranged in the main channel 1 and the sub channels 2, 3. Since the exhaust gas flow rate and pressure control to the analyzers 4, 5, and 6 can be controlled by a common vacuum pump 19, the apparatus can be reduced in size and power can be saved. Can be achieved.

  Furthermore, in the infrared gas analyzer 4, the dehumidifier for reducing the influence of moisture interference can be unnecessary or reduced in size, so that the apparatus can also be made compact and save power.

  In addition, in this embodiment, the auxiliary flow passages 2 and 3 are provided from the branch portion 16 of the main flow passage 1 so that exhaust gas is introduced into the analyzers 4, 5 and 6 as soon as possible and simultaneously as possible. Furthermore, since the information processing device 7 corrects the deviation of the exhaust gas arrival time to the analyzers 4, 5 and 6, it continuously measures the concentration of the target component in the exhaust gas with good responsiveness. can do.

  As a result of such contrivance, it becomes possible for the first time to realize the exhaust gas analyzer 100 that is capable of continuous real-time measurement on a vehicle and that has excellent measurement accuracy as in this embodiment.

  The present invention is not limited to the above embodiment. Other methods and configurations for interference and quenching correction are conceivable, and components to be measured are not limited to those shown in the above embodiment. Other analyzers may be used. The present invention can be applied not only to a vehicle-mounted type but also to a stand-alone type used in a laboratory, and the same effects as the above-described embodiment can be obtained.

  In addition, the present invention can be variously modified without departing from the spirit of the present invention.

  According to the present invention, it is possible to provide an exhaust gas analyzer 100 that can be made compact and power-saving, has good sensitivity, and can perform real-time continuous measurement.

1 is an overall fluid circuit diagram of an exhaust gas analyzer according to an embodiment of the present invention. The circuit block diagram of the information processing apparatus in the embodiment. The functional block diagram of the information processing apparatus in the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Exhaust gas analyzer 1 ... Main flow path 2, 3 ... Sub flow path 4 ... Infrared gas analyzer 5 ... Hydrogen flame ionization analyzer 6 ... Chemiluminescent nitrogen oxide Analyzer 19 ... Pump 73 ... Correction unit

Claims (5)

A main flow path through which exhaust gas discharged from the internal combustion engine is continuously introduced in time series and passes most of the exhaust gas ;
One or a plurality of secondary flow channel provided in parallel to the main flow path branched from the main channel,
Different analyzers that are provided on the main flow path and the sub flow path, respectively, and measure the concentrations of a plurality of measurement target components in the exhaust gas in time series,
Based on the difference in time until the exhaust gas reaches each analyzer, an actual value acquisition unit that acquires the actual value of the target component concentration in the exhaust gas exhausted at the same time, and
A correction unit that corrects a deviation from a true value that occurs in a part or all of each actual measurement value due to the mutual influence of the measurement target component, based on a part or all of each actual measurement value ,
As the analyzer, an exhaust gas comprising an infrared gas analyzer provided on the main flow path, and a flame ionization analyzer and / or a chemiluminescent nitrogen oxide analyzer provided on the sub flow path. Gas analyzer. The analyzer is equipped with a flame ionization analyzer,
The correction unit performs intermediate correction on the measured values of the CO concentration, the CO ₂ concentration, and the H ₂ O concentration by the infrared gas analyzer based on the measured values of the THC concentration by the hydrogen flame ionization analyzer, and the CO and CO ₂ concentrations intermediate correction value and on the basis of the intermediate correction value of H _{2 O} concentration, the CO and CO ₂ concentration exhaust gas analyzer of the intermediate correction is to further correct the value according to claim 1 of. A chemiluminescent nitrogen oxide analyzer is provided as the analyzer,
3. The exhaust according to claim 2, wherein the correction unit corrects an actual measured value of NO _X concentration by the chemiluminescent nitrogen oxide analyzer based on final correction values of the CO ₂ concentration and H ₂ O concentration. Gas analyzer. The exhaust gas analyzer according to any one of claims 1 to 3, wherein the downstream end of the main channel and the sub channel is sucked by a common pump. The exhaust gas analyzer according to any one of claims 1 to 4, which is a vehicle-mounted type.