JP2010223702A - Exhaust gas analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas analyzer capable of measuring properly and simultaneously an exhaust gas component concentration and the air-fuel ratio. <P>SOLUTION: This exhaust gas analyzer is loaded on a vehicle, or the like, in addition to a measuring chamber, and analyzes exhaust gas discharged from an internal combustion engine. More specifically, the exhaust gas analyzer measures a moisture concentration in the exhaust gas by Fourier-transform infrared spectroscopy; calculates the moisture concentration in the exhaust gas by a theoretical combustion reaction formula; and calculates the amount of moisture condensed in an exhaust system and the amount of moisture generated by re-evaporation of condensed moisture, based on the moisture concentration and calculated moisture concentration measured. Then, the measured gas concentration of a carbon component is corrected, based on the calculated amount of moisture, and the air-fuel ratio of the exhaust gas is calculated by a carbon balance method. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exhaust gas analyzer that analyzes exhaust gas discharged from an internal combustion engine.

  Conventionally, techniques for analyzing exhaust gas by Fourier transform infrared spectroscopy, carbon balance method, and the like have been proposed. For example, Patent Document 1 proposes an infrared gas analysis method for correcting the influence of moisture contained in a sample gas and obtaining the concentration of a desired measurement target component. Specifically, in this technique, highly accurate concentration measurement is performed by removing moisture interference and moisture coexistence effects. In addition, Patent Document 2 proposes a technique related to the present invention.

Japanese Patent No. 3771849 Japanese Patent Laid-Open No. 10-38850

  However, Patent Documents 1 and 2 described above do not describe a method of appropriately measuring the exhaust behavior of the exhaust gas component concentration and the change in the air-fuel ratio at the same time.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an exhaust gas analyzer that can appropriately and simultaneously measure the exhaust gas component concentration and the air-fuel ratio. .

  In one aspect of the present invention, an exhaust gas analyzer that analyzes exhaust gas discharged from an internal combustion engine measures moisture concentration in the exhaust gas by analyzing the exhaust gas by Fourier transform infrared spectroscopy. A moisture concentration measuring means for calculating the moisture concentration in the exhaust gas based on a theoretical combustion reaction equation representing combustion in the internal combustion engine, and a moisture concentration measured by the moisture concentration measuring means Based on the moisture concentration calculated by the moisture concentration calculating means, the moisture amount calculation for calculating the amount of moisture condensed in the exhaust system in the internal combustion engine and the amount of moisture re-vaporized from the moisture condensed in the exhaust system. And the carbon composition in the exhaust gas measured by the Fourier transform infrared spectroscopy based on the water content calculated by the water content calculating device. An air-fuel ratio for calculating the air-fuel ratio of the exhaust gas by a carbon balance method using a carbon component gas concentration correcting means for correcting the gas concentration of the gas and a gas concentration of the carbon component corrected by the carbon component gas concentration correcting means Calculating means.

  The exhaust gas analyzer is installed in a vehicle or the like other than the measurement chamber, and analyzes exhaust gas discharged from the internal combustion engine. The moisture concentration measuring means measures the moisture concentration in the exhaust gas by Fourier transform infrared spectroscopy, and the moisture concentration calculating means calculates the moisture concentration in the exhaust gas by a theoretical combustion reaction equation. The moisture amount calculating means calculates the amount of moisture condensed in the exhaust system and the amount of moisture re-vaporized from the condensed water based on the measured moisture concentration and the calculated moisture concentration. The carbon component gas concentration correction means corrects the gas concentration of the carbon component in the exhaust gas measured by Fourier transform infrared spectroscopy based on the calculated water content. The air / fuel ratio calculating means calculates the air / fuel ratio of the exhaust gas by the carbon balance method using the corrected gas concentration of the carbon component. As a result, it is possible to accurately calculate the air-fuel ratio of the exhaust gas by appropriately taking into consideration the amount of moisture condensed and re-vaporized in the exhaust system.

1 is a schematic configuration diagram of a system to which an exhaust gas analyzer in the present embodiment is applied. It is a block diagram which shows schematic structure of an exhaust-gas analyzer. It is a flowchart which shows the air fuel ratio calculation process in this embodiment.

Preferred embodiments of the present invention will be described below with reference to the drawings.
[Device configuration]
FIG. 1 is a schematic configuration diagram illustrating an example of a system to which an exhaust gas analyzer according to this embodiment is applied. In FIG. 1, a solid line arrow shows an example of the flow of exhaust.

  As illustrated, the system mainly includes an engine (internal combustion engine) 1, an exhaust passage 2, an exhaust gas collection passage 3, an exhaust gas analyzer 4, and an exhaust gas discharge passage 5. The system is mounted on a vehicle or the like other than the measurement room.

  The engine 1 burns a mixture of air and fuel and outputs driving power for the vehicle. Exhaust gas generated by combustion in the engine 1 is discharged to the exhaust passage 2. An exhaust gas collection passage 3 for supplying exhaust gas to the exhaust gas analyzer 4 is connected on the exhaust passage 2.

  The exhaust gas analyzer 4 includes an FTIR (Fourier Transform Infrared Spectroscopy) multi-component meter (not shown), a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The exhaust gas collected through the Although details will be described later, the exhaust gas analyzer 4 is configured to be able to simultaneously measure the exhaust gas component concentration and the air-fuel ratio of the exhaust gas. The exhaust gas analyzed by the exhaust gas analyzer 4 is returned to the exhaust passage 2 via the exhaust gas discharge passage 5.

  FIG. 2 is a block diagram showing a schematic configuration of the exhaust gas analyzer 4. As shown in the figure, the exhaust gas analyzer 4 mainly includes an exhaust gas component concentration measurement unit 4a, an air-fuel ratio calculation processing unit 4b, a fuel data storage unit 4c, and a display unit 4d.

The exhaust gas component concentration measuring unit 4a measures the concentration of the exhaust gas component by Fourier transform infrared spectroscopy (hereinafter referred to as “FTIR method”). Specifically, the exhaust gas component concentration measuring unit 4a corresponds to an FTIR multi-component meter, and quantitatively analyzes the multi-components in the exhaust gas from an absorption spectrum obtained by irradiating the exhaust gas with infrared light. The exhaust gas component concentration measuring unit 4a is, for example, a gas concentration of H ₂ O in the exhaust gas (hereinafter referred to as “moisture concentration”) or a gas concentration of C-containing components such as CO ₂ , CO, and HC (hereinafter referred to as “water concentration”) , Called “carbon component gas concentration”). The exhaust gas component concentration measuring unit 4a corresponds to the moisture concentration measuring means in the present invention.

  The fuel data storage unit 4c stores fuel data. Specifically, data such as the type of fuel (test fuel) (for example, EtOH content) and the C / H / O composition ratio are stored as fuel data in the fuel data storage unit 4c. Such fuel data is registered in advance in the fuel data storage unit 4c.

The air-fuel ratio calculation processing unit 4b calculates the air-fuel ratio (A / F) of the exhaust gas based on the measurement result in the exhaust gas component concentration measurement unit 4a and the fuel data stored in the fuel data storage unit 4c. Perform the process. Basically, the air-fuel ratio calculation processing unit 4b calculates the air-fuel ratio based on the carbon component gas concentration and the like by the carbon balance method. In brief, the carbon balance method is a method of calculating the amount of fuel used in combustion based on the carbon component gas concentration in the exhaust gas. The air-fuel ratio calculation processing unit 4b outputs the calculated air-fuel ratio data to the display unit 4d and displays it on the display unit 4d.
[Air-fuel ratio calculation method]
Next, the air-fuel ratio calculation method performed by the air-fuel ratio calculation processing unit 4b in the present embodiment will be specifically described.

  In the present embodiment, the air-fuel ratio calculation processing unit 4b is configured to determine the moisture concentration measured by the FTIR method (hereinafter referred to as “moisture concentration measured value”) and the moisture concentration obtained from the theoretical combustion reaction equation (hereinafter referred to as “ The amount of water condensed in the exhaust system and the amount of water re-vaporized from the condensed water are calculated based on the water concentration theoretical value, and the carbon component gas measured by the FTIR method based on the amount of water is calculated. The concentration is corrected, and the air-fuel ratio is calculated by the carbon balance method using the corrected carbon component gas concentration. As described above, the air-fuel ratio calculation processing unit 4b functions as the water concentration calculation means, the water content calculation means, the carbon component gas concentration correction means, and the air-fuel ratio calculation means in the present invention.

  The reason for calculating the air-fuel ratio in this way is as follows. It can be said that simultaneous measurement of exhaust gas component emission behavior and air-fuel ratio is effective for the evaluation and analysis of exhaust emission reduction technology. As a method for simultaneously measuring the exhaust behavior of the exhaust gas component concentration and the change in the air-fuel ratio, it is conceivable to use the FTIR method and the carbon balance method. Specifically, a method is conceivable in which the carbon component gas concentration in the exhaust gas is measured by the FTIR method, and the air-fuel ratio is calculated by the carbon balance method using the measured carbon component gas concentration. However, when such a method is used as it is, it can be said that the air-fuel ratio may not be calculated with high accuracy.

This is because the exhaust gas generated by combustion contains about 10% or more of moisture. This is because, by vaporizing, the exhaust gas component concentration may not be appropriately measured by the FTIR method under a certain condition (water coexistence). Specifically, in the cold start region, since the temperature of the engine 1 and the exhaust system is low, moisture is condensed in the exhaust system, so that the moisture concentration measured by the FTIR method is the moisture concentration of the original combustion product gas. May be: In this case, the gas concentration (for example, concentration of CO ₂ or the like) of other measurement objects is measured high, and the air-fuel ratio obtained by the carbon balance method tends to be richer than the actual state. On the contrary, in the warm-up process region, the moisture condensed in the exhaust system is vaporized, so that the required air-fuel ratio tends to be leaner than the actual condition.

  Thus, it is considered that the coexistence moisture concentration changes due to the change in the amount of moisture that has been condensed and re-vaporized, which affects the measured value of the exhaust gas component concentration. Therefore, if the carbon component gas concentration measured by the FTIR method is used as it is, it can be said that the air-fuel ratio may not be accurately calculated by the carbon balance method. In addition, since the amount of moisture in the exhaust gas varies depending on the test fuel composition, it is considered that the amount of moisture that is condensed and re-vaporized in the exhaust system changes.

  Therefore, in this embodiment, the amount of moisture condensed and re-vaporized in the exhaust system is calculated, the carbon component gas concentration measured by the FTIR method is corrected based on the moisture amount, and the corrected carbon component gas concentration is calculated. To calculate the air-fuel ratio. Specifically, the air-fuel ratio calculation processing unit 4b calculates the air-fuel ratio as follows.

  The air-fuel ratio calculation processing unit 4b first acquires the water concentration (measured water concentration value) measured by the exhaust gas component concentration measuring unit 4a, and determines whether or not the measured water concentration value is within a predetermined range. Do. This determination corresponds to determining whether or not moisture condensation or revaporization has occurred in the exhaust system. The predetermined range used for the determination is determined based on the moisture concentration in the original combustion product gas.

  When the measured value of the moisture concentration is within the predetermined range, it can be said that there is almost no condensation or re-vaporization of moisture in the exhaust system. In this case, since it is considered unnecessary to correct the carbon component gas concentration measured by the FTIR method, the air-fuel ratio calculation processing unit 4b uses the carbon component gas concentration as it is and performs the air-fuel ratio calculation by the carbon balance method. Is calculated.

  On the other hand, when the measured value of the moisture concentration is outside the predetermined range, it can be said that moisture condensation / re-vaporization occurs in the exhaust system. In this case, since it is considered that the air-fuel ratio should not be calculated using the carbon component gas concentration measured by the FTIR method as it is, the air-fuel ratio calculation processing unit 4b corrects the carbon component gas concentration.

  In order to correct the carbon component gas concentration, the air-fuel ratio calculation processing unit 4b first calculates the amount of moisture condensed and re-vaporized in the exhaust system. Specifically, the air-fuel ratio calculation processing unit 4b calculates the water concentration (the water concentration theoretical value) from the theoretical combustion reaction formula representing the combustion in the engine 1, and is measured by the water concentration theoretical value and the FTIR method. Based on the measured moisture concentration, the amount of moisture condensed and re-vaporized in the exhaust system is calculated. In this case, the air-fuel ratio calculation processing unit 4b calculates a theoretical water concentration value based on, for example, a theoretical combustion reaction equation represented by the following equation (1).

C _x H _y O _z + (x + y / 4-z / 2) O ₂ + 0.79 / 0.21 (x + y / 4-z / 2) N ₂
→ xCO ₂ + y / 2H ₂ O + 0.79 / 0.21 (x + y / 4-z / 2) N ₂ formula (1)
Specifically, the air-fuel ratio calculation processing unit 4b uses the fuel data (C / H / O composition ratio or EtOH content ratio) stored in the fuel data storage unit 4c to calculate the theory represented by the equation (1). Based on the combustion reaction equation, the theoretical value of water concentration is calculated.

  Then, the air-fuel ratio calculation processing unit 4b calculates the amount of moisture condensed and re-vaporized based on the theoretical value of moisture concentration and the measured value of moisture concentration, and then the carbon component gas measured by the FTIR method based on the amount of moisture. The concentration is corrected, and the air-fuel ratio is calculated by the carbon balance method using the corrected carbon component gas concentration.

According to the air-fuel ratio calculation method described above, the air-fuel ratio can be calculated with high accuracy. Therefore, according to the exhaust gas analyzer 4 in the present embodiment, it is possible to appropriately and simultaneously measure the exhaust behavior of the exhaust gas component concentration and the change in the air-fuel ratio using the FTIR method and the carbon balance method.
[Air-fuel ratio calculation processing]
Next, the air-fuel ratio calculation process in this embodiment will be described with reference to FIG. This process is repeatedly executed at a predetermined cycle by the air-fuel ratio calculation processing unit 4b.

First, in step S101, the air-fuel ratio calculation processing unit 4b acquires the exhaust gas component concentration measured by the FTIR method from the exhaust gas component concentration measurement unit 4a. Specifically, the air-fuel ratio calculation processing unit 4b acquires the gas concentration of the component necessary for calculating the air-fuel ratio. In detail, the air-fuel ratio calculation processing unit 4b is configured such that the gas concentration of H ₂ O (water concentration), the gas concentration of C-containing components such as CO ₂ , CO, and HC (carbon component gas concentration), the gas concentration of EtOH, etc. To get. Then, the process proceeds to step S102.

  In step S102, the air-fuel ratio calculation processing unit 4b determines whether or not the water concentration (water concentration actual measurement value) acquired in step S101 is within a predetermined range. Here, it is determined whether or not moisture condensation or re-vaporization has occurred in the exhaust system. The predetermined range used for the determination is determined based on the moisture concentration in the original combustion product gas.

  When the moisture concentration actual measurement value is within the predetermined range (step S102; Yes), the process proceeds to step S106. In this case, since it can be said that almost no condensation or re-vaporization of moisture occurs in the exhaust system, the air-fuel ratio calculation processing unit 4b does not correct the carbon component gas concentration measured by the FTIR method. That is, the air-fuel ratio calculation processing unit 4b calculates the air-fuel ratio by the carbon balance method using the carbon component gas concentration measured by the FTIR method as it is (step S106). Then, the process proceeds to step S107.

  On the other hand, when the moisture concentration measured value is outside the predetermined range (step S102; No), the process proceeds to step S103. In this case, since it is considered that moisture condensation and re-vaporization occur in the exhaust system, the air-fuel ratio calculation processing unit 4b is measured by the FTIR method in the processing after Step S103 (Steps S103 to S105). Processing for correcting the carbon component gas concentration is performed.

  In step S103, the air-fuel ratio calculation processing unit 4b calculates a theoretical water concentration value from the theoretical combustion reaction equation. Specifically, the air-fuel ratio calculation processing unit 4b uses the fuel data (C / H / O composition ratio or EtOH content ratio) stored in the fuel data storage unit 4c, and is expressed by the above equation (1). Based on the theoretical combustion reaction equation, the theoretical value of water concentration is calculated. Then, the process proceeds to step S104.

  In step S104, the air-fuel ratio calculation processing unit 4b calculates the amount of moisture condensed / re-vaporized in the exhaust system based on the actual measured water concentration obtained in step S101 and the theoretical water concentration calculated in step S103. To do. Specifically, the air-fuel ratio calculation processing unit 4b obtains the difference between the actually measured water concentration value and the theoretical water concentration value, and obtains the moisture amount corresponding to the difference. Then, the process proceeds to step S105.

  In step S105, the air-fuel ratio calculation processing unit 4b corrects the carbon component gas concentration measured by the FTIR method based on the moisture amount calculated in step S104. Specifically, the air-fuel ratio calculation processing unit 4b performs correction to increase or decrease the carbon component gas concentration by a concentration corresponding to the amount of moisture condensed or re-vaporized in the exhaust system. Then, the process proceeds to step S106.

  In step S106, the air-fuel ratio calculation processing unit 4b calculates the air-fuel ratio by the carbon balance method using the carbon component gas concentration corrected in step S105. Then, the process proceeds to step S107.

  In step S107, the air-fuel ratio calculation processing unit 4b outputs the data of the air-fuel ratio calculated in step S106 to the display unit 4d and performs a process for displaying the data on the display unit 4d. Then, the process ends.

  According to the air-fuel ratio calculation process described above, it is possible to accurately calculate the air-fuel ratio of the exhaust gas by appropriately taking into consideration the amount of moisture condensed and re-vaporized in the exhaust system.

1 engine (internal combustion engine)
2 Exhaust passage 3 Exhaust gas collection passage 4 Exhaust gas analyzer 4a Exhaust gas component concentration measurement unit 4b Air-fuel ratio calculation processing unit 4c Fuel data storage unit 4d Display unit 5 Exhaust gas discharge passage

Claims (1)

An exhaust gas analyzer for analyzing exhaust gas discharged from an internal combustion engine,
A moisture concentration measuring means for measuring the moisture concentration in the exhaust gas by analyzing the exhaust gas by Fourier transform infrared spectroscopy;
A moisture concentration calculating means for calculating a moisture concentration in the exhaust gas based on a theoretical combustion reaction equation representing combustion in the internal combustion engine;
Based on the moisture concentration measured by the moisture concentration measuring means and the moisture concentration calculated by the moisture concentration calculating means, the amount of moisture condensed in the exhaust system in the internal combustion engine and the moisture condensed in the exhaust system are Water content calculating means for calculating the re-vaporized water content;
Carbon component gas concentration correcting means for correcting the gas concentration of the carbon component in the exhaust gas measured by the Fourier transform infrared spectroscopy based on the moisture amount calculated by the moisture amount calculating means;
An exhaust gas analysis comprising: an air-fuel ratio calculating means for calculating an air-fuel ratio of the exhaust gas by a carbon balance method using the gas concentration of the carbon component corrected by the carbon component gas concentration correcting means. apparatus.

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