MXPA99007782A - Method and apparatus for remote measurement of exhaust gas - Google Patents

Abstract

A method and apparatus for sensing a composition of exhaust plume (13) includes a light source (11) that radiates an infrared light beam (12) having a plurality of predetermined wavelengths. A first of the predetermined wavelengths is associated with carbon dioxide and a second of the predetermined wavelengths is associated with a second gas, such as a hydrocarbon or carbon monoxide. The apparatus also includes a detector unit (20) that detects the beam passing through the plume. The apparatus computes a ratio of the second gas to carbon dioxide based upon the first and second detected wavelengths, and this ratio is then multiplied by a predetermined estimation of a concentration of carbon dioxide in the plume.

Description

METHOD AND APPARATUS FOR REMOTE GAS MEASUREMENT OF EXHAUST BACKGROUND OF THE INVENTION (a) Field of the Invention The present invention relates generally to the monitoring of environmental pollution, and more specifically to a system for the remote detection of gaseous exhaust compositions, such as those produced by motor vehicles. (b) Description of the Related Technique Environmental pollution, for example air pollution, is a serious problem that is particularly acute in urban areas. Most of this pollution is caused by * exhaust gas emissions from motor vehicles. Official standards have been established to regulate the permissible quantities of certain pollutants in automobile exhaust, and in many areas periodic inspections are required to ensure that vehicles comply with these standards. For example, many states have initiated periodic and mandatory inspection and maintenance (I / M) procedures during which contaminants in the vehicle's exhaust gas are P1507 / 99MX monitor and compare with predetermined standards. If the vehicle emissions do not comply with these standards, the vehicle in general must be repaired in order to comply with the emission regulations. However, there are still large amounts of vehicles traveling on public roads that do not comply with government regulations. Highly polluting vehicles can travel even in areas where periodic emissions inspections are required. For example, some older vehicles and special types of vehicles may be exempt from inspections. In addition, where a substantial period of time is allowed between the periodic inspections required, vehicle emission controls may malfunction. Moreover, although the anti-polluting devices that are required as equipment in more recent vehicles, in general fulfill their purpose of reducing pollution in the exhaust gas of the vehicle within the prescribed levels, it is perceived by some vehicle owners that the anti-pollution equipment reduces the performance of the engine. For this reason, it has been known that some vehicle owners make any arrangement that is necessary to put their vehicles in condition to pass the required inspections, and P1507 / 99MX subsequently, intentionally remove, adjust and / or deactivate anti-pollution devices for normal use. In addition, it is believed that a disproportionately large amount of pollution is generated by a relatively small number of vehicles. Therefore, it would be advantageous to provide a system for testing vehicles that do not require owner participation. Inspection programs typically use a neutral-point test procedure that monitors vehicle emissions at minimum speeds while the vehicle is stopped. Neutral emission standards are usually set at high enough limits to adjust equipment errors, operator errors and calibration errors. The result of this process is that many vehicles with emission equipment that is defective or below standards can escape test and maintenance requirements, and continue to operate with high emissions that pollute the environment. Neutral point test procedures do not test the engine when it is running in a loaded mode, and the largest percentage of contaminants occurs either during a vehicle's acceleration or when it maintains a constant speed under load, rather than when it is stationary. In this way, if the test procedure is run with a vehicle P1507 / 99 Stationary X, uncoupled transmission and no load exerted on the engine, often the check does not accurately measure engine pollutants during normal operation of the vehicle. A) Yes, a device is needed to measure pollutants in the exhaust gas, during a period of actual operation of the vehicle. An anti-pollution program that relies entirely on mandatory periodic inspections carried out in fixed installations may therefore be inadequate. It would be advantageous to identify vehicles that are operating, in fact, violating the prescribed emission standards, and are required either to be placed in accordance with the standards or to be withdrawn from circulation. A remote gas analyzer for testing the exhaust gases of motor vehicles is set forth in U.S. Patent No. 4,924,095 to Swanson, Jr. , the analysis of which is incorporated here, in its entirety, as a reference. One embodiment of the exposed system uses absorption spectroscopy to determine the amount of volume per unit of pollutants in a column of exhaust gases from a motor vehicle. A first plurality of optical beams is arranged to form a first array of beams that substantially encompasses a complete cross section of an exhaust gas column along the length of a P1507 / 99MX predetermined length of exhaust gas column. The spectral content of the first plurality of beams is analyzed to determine the concentration in the exhaust gas column of a first preselected pollutant, usually carbon monoxide or carbon dioxide. A computer determines the relative increase in the amount of volume per unit of the first pollutant caused by the motor vehicle. A second gas analyzer includes a second beam that intersects the exhaust gas column to allow the determination of the increase in concentration of a plurality of contaminants, one of which is the first aforementioned contaminant. The computer further determines the relative increase in the amount of volume per unit of a second polluting gas (i.e., a different pollutant measured by means of the beam array), using the ratio of the increased amount of the second pollutant to the increased amount of the first pollutant.

This proportion is multiplied by the relative increase in the concentration of the first polluting gas (measured by the arrangement) to determine the amount of volume per unit of the second gas. However, this system has the disadvantage that it requires an array of beams that monitor a space large enough to contain a section P1507 / 99 X total cross section of an exhaust gas column. It would be advantageous to provide a system that does not require, inter alia, a beam array to measure the concentration of pollutants in an exhaust gas column. Another apparatus for remote analysis of vehicle emissions is set forth in U.S. Patent No. 5,498,872 to Stedman et al., The analysis of which is hereby incorporated, in its entirety, by reference. The exposed apparatus uses stoichiometric proportions applicable to a general combustion reaction to approximate relative amounts of individual emission components, as opposed to the use of a complete array of beams (as in Swanson) to obtain a measure of the total amount of pollutants emitted in a column of exhaust gases. Stedman's exposed method, however, has the disadvantage, for example, of apparently resting on the erroneous assumption that the exhaust gases and fuel have the same hydrocarbon composition. In addition, the method disclosed contemplates the need for a source of ultraviolet radiation for the measurement of NOx pollutants. It would be advantageous to provide a method that does not require this assumption and does not require a source of ultraviolet radiation to measure NOx contaminants. Another device for remote analysis of P1507 / 99MX vehicle emissions is set forth in U.S. Patent No. 5,591,975 to Jack et al., Which is assigned to the assignee of the present application and is hereby also incorporated herein by reference in its entirety SUMMARY OF THE INVENTION This invention is directed to a method and apparatus for detecting the composition of an exhaust gas column, such as, for example, that produced by a motor vehicle in motion. A light source radiates an infrared beam of light having a plurality of predetermined wavelengths, through an exhaust gas column of a motor vehicle. The system also includes a detector that detects the beam that passes through the column at predetermined wavelengths. The first of the predetermined wavelengths is associated with carbon dioxide and the second of the predetermined wavelengths is associated with a second gas, such as, for example, hydrocarbon gases. The apparatus calculates a ratio of the second gas to carbon dioxide based on the first and second detected wavelengths. This ratio is multiplied by a predetermined estimate of a concentration of carbon dioxide in the column.

P1507 / 99MX The invention also provides a method and apparatus for determining the content of nitrogen oxides in an exhaust gas stream through the use of an infrared radiation source. The method includes determining a ratio of nitrogen oxide to carbon dioxide and multiplying this ratio by a predetermined estimate of the concentration of carbon dioxide in the exhaust gas stream. The invention itself, together with the additional objects and the implicit advantages, will be better understood by reference to the following detailed description, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The only figure is a schematic diagram of one embodiment of a system for remote measurement of exhaust gases of the invention. DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The invention provides a method and a system for measuring the composition of an exhaust gas produced by one of the various sources analyzed. below, for example, the machine of a motor vehicle. In general terms, the system of the invention measures the gas concentrations P1507 / 99MX pollutants emitted in exhaust gas streams, for example in the exhaust gas column of a moving motor vehicle, by analyzing the infrared absorption at selected frequencies of a sample from the exhaust gas column. The specific frequencies selected in the infrared range correspond to various pollutants of interest, which normally include carbon monoxide, carbon dioxide, hydrocarbons and nitrogen oxides such as nitrogen oxide. The infrared absorption data can be analyzed as described below to provide the approximate concentrations of the contaminants in the exhaust gas. Analyzed in detail below, there is a system for measuring the composition of exhaust gas from a motor vehicle that emits an exhaust gas column while the vehicle is traveling on a roadway. However, the invention is not limited to the measurement of exhaust gases from motor vehicles but can also be used to measure emissions from many other sources, including those where the source of the exhaust gases It is not moving. Preferably, however, the invention is used to measure the composition of an exhaust gas stream or column produced by a motor vehicle having an engine of P1507 / 99MX internal combustion. Exhaust gas columns typically include carbon dioxide (C02), carbon monoxide (CO), hydrocarbons (HC or CH), water vapor (H20) and nitrogen oxide (NO), for example. Referring to the figure, the system (referred to generally as element 10) includes a source 11 for supplying infrared radiation ("IR"). The source 11 is preferably a broadband IR source, for example a source having a silicon carbide filament with an associated power supply, and has the ability to produce significant IR radiation in the range of about three microns to approximately six micrometers, for example. The source 11 of infrared radiation provides a beam 12 which can, optionally, be passed through a pushbutton (not shown), as set forth in U.S. Patent No. 5,591,975. The infrared radiation source 11 may be associated with an anterior beam 19, such as a parabolic reflector, for example. The beam 12 is aligned so as to pass through an exhaust gas column 13 of a vehicle 14 when the vehicle 14 is moving on a road 15 in the direction indicated in the figure. The passage of the IR beam 12 through the exhaust gas column 13 results in partial absorption P1507 / 99MX selective of several wavelengths within the broadband beam, the selective absorption that occurs due to the presence of N0X, water vapor, C02, CO, HC (hydrocarbons), and other species within the exhaust gas. As is known to those of skill in the art, each of the aforementioned species absorbs infrared radiation at or near a wavelength or wavelengths. After passing through column 13, beam 12 can pass through an optional IR transparent gas cell (not shown), used for calibration purposes, and then through an integrated or beam diffuser. The diffuse beam is applied to a plurality of narrow-band filters 16, each of the filters corresponds to a measuring channel. Each filter 16 is selected to pass a predetermined narrow band of wavelengths towards a focal plane 17a having a plurality of photodetectors 17 adjusted individually for a specific pollutant. Generally speaking, reference is made to a detector unit that includes the focal plane 17a, such as the element 20. Each photodetector 17 produces an electrical signal to an input of a corresponding measuring channel that includes suitable analog electronic devices (represented by the element 18), an analog-to-digital converter 21, and a data processor 25 having one or more P1507 / 99MX associated output devices, described later. The data processor 25 provides the required signal processing of the products from the analog-to-digital converter 21. The data processor 25 may be coupled to a look-up table, which is more easily implemented as a region of memory (semiconductor and / or disk) accessible by means of the data processor 25, as described in the United States Patent. No. 5,591,975 (previously mentioned) and in U.S. Patent No. 5,418,366, the disclosure of which is hereby incorporated by reference in its entirety. A suitable cooler, for example a thermoelectric device known to those of skill in the art, can be employed to cool the IR detectors 17 which normally require to be cooled to an operating temperature which is below the ambient temperature. There may be, for example, at least six spectral measurement channels, depending on the number of pollutants and reference channels that you want to monitor. For example, there may be a spectral channel NO (having a filter with a passband centered at approximately 5.26 microns), a spectral channel H20 (having a filter with a passband centered at approximately 5.02 microns), a first reference or channel Spectral P1507 / 99MX C02, (having a filter with passband centered at approximately 4.2 microns), a spectral channel CO (having a filter with a passband centered at approximately 4.6 microns), a spectral channel HC (having a filter with a pass band centered at approximately 3.3 microns), and a second reference spectral channel having a filter with a pass band centered at approximately 3.8 microns. Additional channels can also be added to measure other contaminants, if desired. Those of skill in the art will know how to select suitable reference measurement channels. The light source 11 sends a beam of radiation 12 into the detector unit 20 on a continuous basis. The data processor 25 continuously samples all received beam intensities by each of the detectors 17 of the detector unit 20. In addition, when the beam 12 is blocked by a vehicle 14 while passing along the road 15, the processor data 25 retains information concerning carbon monoxide, carbon dioxide, hydrocarbon, nitrogen oxides, and / or water levels in the ambient atmosphere versus vehicle 14 before blocking the beam. This will provide a measurement of "background contamination" to exclude environmental or background pollution levels from P1507 / 99MX measurement as vehicle exhaust gas contamination 14. Analysis of the data provided by system 10 will exclude this level of background contamination. Subsequently, the detector unit and the data processor 25 cooperate to sample carbon monoxide, carbon dioxide, hydrocarbon, nitrogen oxides and water levels (or others that depend on the desired monitoring) of the exhaust gas column 13 the vehicle 14 is left for a predetermined period after the resumption of beam reception by the detector unit 20. This predetermined sampling period is generally from about 0.1 seconds to about 1.0 seconds, for example about half a second. The system 10 can then be restarted for the next passing vehicle. A reference channel is preferably used to remove fluctuations in IR absorption due to the presence of particulate material. The primary signal obtained after the arrival of the vehicle 14 in the test area (the samples described above) is divided by the signal before the arrival of the vehicle. This mechanism is described in U.S. Patent No. 5,591,975. Preferably, the system includes the P1507 / 99MX apparatus for identifying vehicle 14 when desired, for example, when vehicle 14 exhibits unacceptable emission levels. A video camera 30 can record an extreme view of the vehicle 14 and the vehicle circulation plate, simultaneously with the unlocking of the beam by the vehicle 14 (or at some other time after the vehicle passes through the beam ). Alternatively, the front or other portions of the vehicle 14 may be recorded. After carrying out sampling and analysis, as described herein, the levels of various contaminants (e.g., CO, C02, HC, N0X) , and water) can be displayed and / or stored permanently by means of an associated output device, along with any other identification information, such as date and time of the test. Preferably, this information is permanently stored in magnetic or electronic form, although any type of storage can be used with the invention, including digital image storage. The information may be displayed on an output monitor 32 and / or stored in a video recorder 34. The information may also be stored in an electronic memory device 36. The system 10 may be designed to read by itself the registration number of the vehicle, using optical recognition software P1507 / 99MX characters, known to those skilled in the art. In this way, the need to ) Manual identification can be eliminated or reduced.

The data can be retrieved one hour later for its mandatory application, for example, by sending a violation notification (or a notification requiring manual inspection of the vehicle), to the owner of the vehicle 14. Alternatively, a system operator can read information recorded from the monitor 32 and, subsequently, enter the information and the registration number of the circulation in a computer database. The system can also store combined data and video information for each vehicle that is tested, more than just for excessively polluting vehicles, for applications such as the generation of an exhaust gas composition database for different types and models of vehicles. Being in operation, the detector unit 20 is preferably installed along a one-way roadway 15 with the beam located approximately 8 inches to 12 inches, for example 10 inches, above the road 15. The above-described data processor 25 monitors the roadway 25. intensity of the signal channels described above. When the vehicle 14 enters the optical path of the beam 12, a voltage drop signals the presence of the vehicle 14. The voltages coming from each P1507 / 99MX one of the signal channels (for example, the detector for NO, CO, C02, HC and H20) that were acquired before the interruption of the beam 12 by the vehicle 14, are stored in the data processor 25. After the vehicle 14 leaves the path of the beam so that the beam 12 is received again by the detector unit 20, the data processor 25 once again begins to acquire a stream of voltage samples from each of the detectors in time. The detector unit 20 and the data processor 25 continue to sample the voltages from each of the detectors 17 for the aforementioned sampling period from about 0. seconds to about 1.0 second after the vehicle 14 leaves the path of the detector. make. Preferably, the signals from the detectors are averaged by the data processor 25 in a period from about 1 millisecond to about 20 milliseconds for each sample. In this way, a more accurate signal-to-noise ratio can be obtained. The analysis performed by the data processor 25 will now be described in more detail. As mentioned in the foregoing, the data processor 25 is capable of calculating the amounts of contaminants present in the exhaust gas column 13 based in part (but only in part) on relative amounts of pollutants observed in the exhaust by the P1507 / 99MX infrared sampling mechanism. Initially, as mentioned above, the voltage data as a function of time, are accumulated from a hydrocarbon detector, a carbon monoxide detector, a carbon dioxide detector, a nitrogen oxide detector and a reference detector, for example . After the apparatus measures the difference between (a) the transmission value of a contaminant present before vehicle 14 passes through the test area, and (b) the contaminant transmission value in column 13, these primary data are preferably standardized. For example, the proportions of the voltages CO with respect to the reference voltages are calculated, and these arbitrary units are recalibrated in calibrated CO values. As described in U.S. Patent Nos. 5,591,975 and 5,418,366, a polynomial equation is preferably used to convert the primary data to an effective concentration (in percent or parts per million) of the detected contaminants.

Measurement of Carbon Monoxide The measurement of the carbon monoxide content of a vehicle can initially include a determination of a correlation between the concentration of hydrocarbons (HC) and dioxide P1507 / 99MX carbon (C02). This correlation can be obtained, for example, by plotting a graph of ) correlation, the values HC and C02 obtained by the data processor 25 through the detectors 17.

The data processor 25 calculates the inclination of an optimal line corresponding to these values by means of a least squares regression analysis.

The slope of this line is the molar ratio HC: C02 (also referred to herein as RHc / co2 ° , 10 HC / C02), and represents the measurement of the relative molar amounts of hydrocarbons and carbon dioxide in the exhaust gas column. This analysis is also described in the Patent of the United States No. 5,418,366. 15 Similarly, a correlation between the concentration of carbon monoxide (CO) and carbon dioxide (C02) is also determined. Similar to the calculation for RHc / co2 above, a correlation between CO and C02 can also be obtained, for example, representing in a correlation graph the CO and C02 values obtained by the data processor 25 through the detectors 17. The data processor 25 calculates the inclination of an optimal line corresponding to these values by means of a least squares regression analysis. The slope of this line is the molar ratio CO: C02 (also referred to as Ro / co2 ° C0 / C02), and represents the measurement of the molar quantities P1507 / 99MX relative to carbon monoxide and carbon dioxide in the exhaust gas column. The values for RCo / co2 and RHC / CO2 are used in a calculation of an estimated concentration of carbon monoxide in the exhaust gas column. More specifically, to provide the carbon monoxide concentration, the values for RCo / co2 Y ^ -HCCO2 are preferably used in a calculation incorporating relative amounts of components of the fuel combustion reaction. The calculation, like the one represented in equations 27, 23 and 30 below, incorporates assumptions that differ from the hydrocarbon content of the fuel and the exhaust gas. A derivation of equations 23 and 27 will now be illustrated. An internal combustion engine burns a fuel containing carbon and hydrogen (formula CHX) with air, where the approximate formula for air can be considered as 0.21 [02] + 0.79 [ IATM], where "IATM" is the concentration of inert atmospheric gas. Nitrogen is the main component of IATM. In this way, n moles of 02 require 3.76n moles of inert constituents of atmosphere by volume. The combustion process can be described by means of the following equation, where "RHCF" is the ratio H: C for fuel, and "RHc" is Ia P1507 / 99 X H: C ratio for the exhaust gas. + n [? 2] + 3 .76n [jArM] =? [C02] + l [c?] + m [CHsnc] + k '[H2 °] + 3 • 762-fjA? M] In the analysis below, the proportion H: C for fuel (RHCF) will be assumed later to be approximately 1.85, since, as a generalization to simplify, it is assumed that in the fuel there are equal concentrations of alkanes, alkenes and aromatics in the forms C8H18, dHi6 and C6H6 . Adding C and H and taking the ratio of H over C gives a value of about 1.82. It is assumed that RHC (exhaust gas) is approximately 2.33, while it is assumed that the hydrocarbons in the exhaust gas will be approximately 100 percent hexane, C6H14. Thus, it is evident that, using the appropriate assumptions, there will be a substantial difference between RHCF and RHC. The use of assumptions that vary from the assumptions RHCF = 1.82 and RHC = 2.33 described above is within the scope of the invention. For example, the assumed value for RHCF may be in a range of about 1.7 to about 2.0, while the assumed value for RHC may be in a range of about 2.1 to about 2.5. (Note that for natural gas (CH4) fuel, both RHCF and RHC would be approximately 4.) A person with normal expertise P1507 / 99MX in the art would be able to determine other suitable proportions based on the fuel composition, in view of the present analysis. In view of the conservation of carbon, hydrogen and oxygen in the above combustion reaction, 3 equations and 3 unknown ones may have been developed. These equations are shown for oxygen conservation (2), carbon conservation (3), and hydrogen conservation (4), respectively: (2) 2n = 2 k + l + k ' (3) 1 = k + l + m (4) RHCF = mRHC + 2k ' The following equations illustrate the proportions C0 / C02 (eo / ce ^) and HC / C02 (HC / CO2) of the exhaust gas, in view of equation 1 above: (5) [CO] I [CO? = R co I co2 = 1 / k (6) [CHWC] I [CO = R? C I CO2 m i k By means of a second arrangement of the above equations, they can be solved by substitution, as shown below. Initially, replacing equations 5 and 6 in equation 3: (7) 1 = k + k x ^ / co2 + kxR -HC / C02 = k (l + R -co I co 'HC I Co P1507 / 99MX (8) = k = (1 + R, co I co2"" "HC / C02 i Substituting equation 6 in equation 4 provides: or: R = mR "" + 2k '= kR -HC I CQ x i? "" + 2k < Re-arranging the above equation provides: 1 (10) Je '= - (R "2 • ^^ H 8j X ^ HC' Substituting equation 10 and equation 5 in equation 2: (11) 2n = 2k + kR -, CO I C02 + K ' 1 (12) 2n = 2k + KRC0 / 8? + - (RH KRHC / C02 X - ^ Hc) 2 R -HC / COj X J H (13) TX = n = 2 + R -, co i co2 + R " R? C / co. x Ra (13) n = n 2 + R, co i co2 + R " From equations 8 and 6 R? C / co2 (14) (1 + i2C0 / C0a + RHC i co) From equations 8 and 5 - "as / co (15) Ico = 1 = (1 + R? Q i co ^ + RHC / ^) P1507 / 99MX A first calculation gives the percentage concentration of C02 in the vehicle exhaust for a wet exhaust gas (ie, which includes steam): (16)% co2 = Ir -4- 7 ^ -co2 ^ -'- co + it + k? +3 76? X Re-arranging the above equation (16) provides: (17)% co2 = 8CH 3. 762 ^ 1 + + + + K "K,? K " From equation 5 and equation 6 From equations 8, 10 and 13, the following equations are derived: / co2 (20) 3. 76 By combining terms, the following equation is provided. (twenty-one) P1507 / 99MX 5.76i? "% Co x = 1 + R -c, o / co2" * "^ -HI CO" "" (1 + R -, co I co2 3.76 5.76 + R-EC I C02 > + 4 + 2-? O / co21? HC I CO ^ HC Combining similar terms, the following equation is provided: -i., "- 5.7 'SR" "" 5.76R "r"% c? 21 = 4.76 + - ^ EL +? 8 / c? 2 (l + _ ^ L + (22) As described above, based on an assumption of RHCF = 1.85 and RHC = 2.33, the following equation is solved by the concentration of carbon dioxide. This equation is used for the determination of carbon monoxide content based on wet exhaust gas: 1 (23) l8? = 7.42 + 5.54R, with co2 + 0.308J? ? C I C? According to a second calculation, in order to solve for the dry exhaust gas (ie, excluding water vapor), the term k1 (the number of moles of water in the exhaust gas) is omitted from equation 17 above : P1507 / 99MX 3.76 £ "% co; 1 =? + R8 / 82 - "- HC / co2 ~ * ~ (1? D / co2 (25) 3.76 R?, C l CO. ) + (4 + 2J2 -c, or I co2 R? C I CO2 x RHr) Combining terms + As described in the above, based on an assumption of RHCF = 1.85 and RHC = 2.33, for dry exhaust gas: (27)% co: = 6.53 + 4.62.R, co i co + 0.549J? ? C / co3 To summarize, considering the molar amounts of the components in the combustion reaction (equation 1 above), the concentration of carbon dioxide based on the dry exhaust gas is shown in the following equation: (28) [CO ^ CO, + ICO - 8CH, ^ + 3 - 76OJA ™ + 0H2O Similar to equations 16 and 28, the following equation describes the concentration of carbon dioxide based on the wet exhaust gas (ie, which includes water vapor in the exhaust gas). , (29) [COJ = k02 + 1-CO - mCH¡ulc + 3 • 6niA M + k? 2 P1507 / 99MX In view of the above derivation, the following equation can be used to calculate the concentration of carbon dioxide based on the dry exhaust gas: (27) [COJ = 6.53 + 4.62R -, co / ca¡ + 0.549i? ? C 1 co2 Similar to equation 27 above, in view of the previous derivation, the following equation can be used to calculate the carbon dioxide concentration based on wet exhaust gas: 1 (23) [82] 7.42 + 5.54R, co1 co2 0.308? HC I CO, Since the factors that include RHC / CO2 make an insignificant contribution to the accuracy of the calculation of carbon dioxide in equations 27 and 23, the concentration of C02 is calculated in practice, in accordance with the following equations. Equation 30 is used to calculate the concentration of C02 based on the dry exhaust gas, while equation 31 is used to calculate the concentration of C02 based on the wet exhaust gas. 1 (30) [COJ = 6.53 + 4.62R, co / co2 (31) [COJ - 7.42 + 5.54J ?, co i co2 P1507 / 99MX Since RCo / co2 is defined as the concentration of carbon monoxide divided by the concentration of carbon dioxide: (3 2) [CO] = R V, O I co2 x [COJ The values for Rco / co2 and RHC / CO2 are replaced in equation 30 above, to provide an estimated concentration of carbon monoxide in the exhaust gas column. This value is multiplied by the calculation of carbon dioxide content provided by equation 30 (dry exhaust gas) or by equation 31 (wet exhaust gas) to provide the carbon monoxide content of the exhaust gas. In this way, the invention provides the option of calculating the carbon monoxide content based on the dry or wet exhaust gas, depending on the standard values with which the content is compared in determining whether the tested vehicle is excessively polluting. In this way, the percentages of carbon monoxide and carbon dioxide in the exhaust gas can be determined by the slope of (a) a line that can be represented as a calibrated CO value against a calibrated C02 value, and (b) a line that can be represented as a calibrated HC value against a calibrated C02 value.

P1507 / 99MX Hydrocarbon Measurement The hydrocarbon content of the exhaust gas column is preferably measured in accordance with the method described above. An initial stage of the analysis includes the determination of a correlation between the concentration of hydrocarbons (HC) and carbon dioxide (C02) to provide the relative molar amounts of hydrocarbons and carbon dioxide in the exhaust gas column. As described above, this correlation can be obtained by plotting on a correlation graph the HC and C02 values obtained by the data processor 25 via the detectors 17, as described above, to provide a molar ratio HC: C02 ( also represented by RHc / co2 ° HC / C02). The analysis for the calculation of hydrocarbon content of the exhaust gas should also include the use of an average measurement of typical carbon dioxide concentrations obtained from exhaust gas measurements of hundreds or thousands of motor vehicles operated on or near of locations where remote testing takes place. Preferably, the assumed concentration of carbon dioxide is obtained from the data compiled from the inspection and local maintenance (1 / M) programs sponsored by a P1507 / 99MX government agency. Alternatively, this assumed concentration could be determined experimentally by the operator of the invention prior to the development of the remote test. The carbon dioxide content of the exhaust gases produced by an internal combustion engine of a moving motor vehicle is generally in a range of about 12 volume percent or mole percent, to about 18 volume percent or one hundred molar. The estimation of the predetermined carbon dioxide content, as indicated in the foregoing, is based in general on the experience obtained in I / M programs. More specifically, the concentration of carbon dioxide in the exhaust gas column of a motor vehicle will generally be in a range of about 14 volume percent to about 16 volume percent, and more particularly about 15 volume percent. percent by volume (eg, approximately 15.3 percent), based on the dry volume of the total exhaust gas (ie, excluding water vapor). The concentration of carbon dioxide will normally be in the range of about 12 volume percent to about 14 volume percent, and more particularly, about 13 volume percent (eg, about P1507 / 99MX 13.4 percent by volume) based on the wet volume of the exhaust gas (ie, including water vapor). This carbon dioxide default will vary depending on the location where the remote test is conducted. The general values described above can be influenced, for example, by the ambient temperature, the ambient pressure (based on altitude, for example), and by other factors. Using the aforementioned ratio of hydrocarbon to carbon dioxide described above, the concentration of the hydrocarbons can then be calculated from the general measurement of C02. An analog or digital multiplier, preferably a part of, or associated with, the data processor 25, multiplies the HC: C02 ratio by the predetermined typical concentration of carbon dioxide in the exhaust gas column. For example, assuming that the criterion for the concentration of carbon dioxide taken is 15%, then the concentration of hydrocarbons (percent molar or by volume) in the exhaust gas column would be calculated according to the following equation: (33)% HC = 15% x HC / CO.

The previous methods to use the P1507 / 99MX infrared absorption data to determine the hydrocarbon content of the exhaust gas, have usually caused a report below the hydrocarbon content. Normally there are many species of hydrocarbons in the exhaust column, and in order to simplify the apparatus, it is assumed that all these species absorb infrared light at relatively short wavelengths, thus causing a report below the hydrocarbon content. The present invention handles this problem using preferably a correction factor determined experimentally, to compensate for any sub-measurement. Preferably, the% HC measured in equation 33 above is multiplied by this correction factor to provide a final hydrocarbon concentration measurement. For cars, this correction factor is preferably in the range of about 1.5 to about 4, more preferably in the range of about 1.7 to about 2.7, and most preferably, of about 2.2. For light trucks, the correction factor is preferably in a range of about 1.5 to about 4, more preferably in a range of about 1.8 to about 3.4, and most preferably, of about 2.6. By way of P1507 / 99MX preferred, the apparatus described in the above can be programmed based on local conditions. In this way, the apparatus of the invention can provide data that is directly compared to data obtained through typical I / M programs that use flame ionization techniques for the measurement of hydrocarbons. A relevant article for these correction factors, from Singer et al., "A Fuel-Based Motor Vehicle Emission Inventory", Journal of the Air & Waste Management Association, Vol. 46, No. 6 (June 1996), is hereby incorporated by reference, in its entirety. According to another embodiment of the invention, the CO concentration can be calculated in a manner similar to that used for the calculation of hydrocarbons. In this modality, the correlation between CO and C02 is calculated in the manner described in the foregoing. The typical level of carbon dioxide content is then multiplied by the ratio of carbon monoxide to carbon dioxide. For example, assuming that the carbon dioxide concentration is 15%, the carbon monoxide content (in mole percent or volume) could be estimated according to the following equation: (34)% CO = 15% x CO / CO- P1507 / 99MX Measurement of Nitrogen Oxides According to another embodiment of the invention, the concentration of nitrogen oxides (NOx, for example NO) in the exhaust gas column can be measured. The first factor used in the calculation of NO concentration is a ratio of N0 / C02 (RN0 / C02), which is obtained from the data provided by the detectors 17 and by the data processor 25. The data representing the measurement of the relative molar amounts of nitrogen oxide and carbon dioxide are used for derive the molar ratio of nitrogen oxide to carbon dioxide (N0 / C02), as described above for the proportions of HC / C02 and CO / C02. The second factor used in the calculation of the concentration is NOT the C02 content in the exhaust gas column. To calculate the concentration of NO, the concentration of C02 is obtained using the C02 estimate, described above, obtained preferably by measuring the CO2 content of the exhaust gases of a large number of vehicles. Alternatively, the method described above for obtaining the C02 content in the carbon monoxide measurement could be used. The concentration of NO is determined by multiplying the concentration of carbon dioxide P1507 / 99 X for the proportion of NO / C02 (RNC / CO2) in the exhaust gas column, as shown in the following equation: (35)% N0 [C02] x NO / CO, The solid particulate matter emitted from the exhaust gas systems may also be a matter of concern, and the system and method of the present invention may also be adapted to measure the opacity of the exhaust gas of a vehicle.

In this way, an indication of the non-gaseous particulate matter that is being generated by the vehicle machine can be provided. The method and apparatus of the invention could also be adapted to measure the mass emissions of a motor vehicle (e.g., grams per mile), incorporating a general assessment of the fuel economy of the vehicle. The method of the invention is simplified from previous methods in which there is no requirement to measure an absolute amount of carbon dioxide in the exhaust gas column through the use of a complete array of infrared beams. This simplifies the infrared absorption calculations and the required apparatus. In addition, unlike some previous approaches, the method and apparatus of the invention do not require the use of an erroneous assumption that the P1507 / 99MX fuel and exhaust gas have the same empirical composition, to measure the carbon monoxide content of the exhaust gas. The invention provides an exact and even simple way, to measure the carbon monoxide content. Furthermore, the invention does not require the assumption that the hydrocarbon content of the exhaust gas is negligible, as in other previous methods. Moreover, when measuring the hydrocarbon content of the exhaust gas, the chemical composition of the fuel and the stoichiometry of its composition do not rely on being part of the calculation. Unlike previous approaches, the calculation of the hydrocarbon concentration will not be based on assumptions related to the chemical composition of the fuel or the stoichiometric proportions associated with fuel combustion. The inventive method is also advantageous in that for the measurement of hydrocarbon content it does not require an erroneous assumption that the fuel and the exhaust gas have the same empirical composition, as required in at least one other prior method, and still have the advantage of improved simplicity. Previous assumptions about the hydrocarbon content of the exhaust gas are particularly inappropriate because more than one hundred hydrocarbon species can be included in P1507 / 99MX automobile exhaust gases, many of which may have different infrared absorption spectra. As a consequence, the prior art inevitably underestimates the hydrocarbon content of the exhaust gas. The present invention addresses this problem by preferably using a correction factor to compensate for any unavoidable sub-measurement, as described above. The method of the invention is even more advantageous because it does not require the use of ultraviolet radiation to measure NOx pollutants. In addition, the NOx content can be measured in the relatively simple manner described in the above.

P1507 / 99MX

Claims (24)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property; An apparatus for detecting a composition of an exhaust gas column, comprising: a light source that radiates an infrared beam of light through the column, the beam includes a plurality of predetermined wavelengths; a detector that detects the beam passing through the column at predetermined wavelengths, wherein a first of the predetermined wavelengths is associated with carbon dioxide and a second of the predetermined wavelengths is associated with a second gas; means for calculating a proportion of the second gas with respect to carbon dioxide, based on the first and second detected wavelengths; and a multiplier that multiplies the ratio by a predetermined estimate of a concentration of carbon dioxide in the column, to provide a measurement of a concentration of the second gas.
2. 2. The apparatus according to claim 1, wherein the second gas is a hydrocarbon. P1507 / 99MX
3. 3. The apparatus according to claim 1, wherein the second gas is a carbon monoxide.
4. 4. The apparatus according to claim 1, wherein the second gas is a nitrogen oxide.
5. 5. The apparatus according to claim 1, wherein the second gas is a nitric oxide.
6. The apparatus according to claim 1, wherein the predetermined carbon dioxide estimate is in a range of about 13 , 10 percent to approximately 18 percent based on the volume of the column.
7. The apparatus according to claim 1, wherein the predetermined estimate of carbon dioxide is in a range of about 14 15 percent to approximately 16 percent based on the dry volume of the column.
8. The apparatus according to claim 1, wherein the predetermined estimate of carbon dioxide is in a range of about 12 20 percent to about 14 percent based on the wet volume of the column.
9. The apparatus according to claim 1, wherein: the detector comprises a plurality of photodetectors, each photodetector is sensitive to a band of wavelengths that includes only one of the predetermined wavelengths.
10. 10. The apparatus according to claim 1, in P1507 / 99MX wherein each detector comprises a photosensitive element and a filter arranged between the column and the photosensitive element having a passage band coincident with a respective band of wavelengths.
11. The apparatus according to claim 1, wherein the predetermined estimate of a carbon dioxide concentration is obtained experimentally.
12. The apparatus according to claim 1, wherein the second gas is a hydrocarbon, further comprising: a multiplier that multiplies the hydrocarbon concentration measurement by a factor determined experimentally.
13. The apparatus according to claim 1, wherein the second gas is a hydrocarbon and a third of the predetermined wavelengths is associated with nitrogen oxide, further comprising: means for calculating a ratio (RNO / co2) of the nitrogen with respect to carbon dioxide, based on the first and third detected wavelengths; and a multiplier that multiplies the proportion (RNO / CO2) by the predetermined estimate of a concentration of carbon dioxide in the column, to provide a measurement of a P1507 / 99MX concentration of nitrogen oxide.
14. The apparatus according to claim 1, wherein the exhaust gas column is produced by burning a fuel and wherein the second gas is a hydrocarbon and a third of the predetermined wavelengths is associated with carbon monoxide, which also comprises: means for calculating a second ratio (RC0 / C02) of carbon monoxide to carbon dioxide, based on the first and third detected wavelengths; and means for calculating a concentration of carbon monoxide in the column from the first ratio and the second ratio (Rco / co2) based on an assumption of a first C: H fuel ratio and a second C ratio: H of the exhaust gas column, the first and second proportions C: H are different.
15. 15. The apparatus according to claim 14, wherein: the first C: H ratio is about 1.85 and the second C.-H ratio is about 2.33.
16. 16. A method for detecting a composition of an exhaust gas column from a moving vehicle, comprising the steps of: irradiating an infrared beam of light through the column, the beam including a plurality of P1507 / 99MX predetermined wavelengths; detecting the beam passing through the column at the predetermined wavelengths, wherein a first of the predetermined wavelengths is associated with carbon dioxide and a second of the predetermined wavelengths is associated with a second gas; calculating a ratio of the second gas to carbon dioxide based on the first and second detected wavelengths; and multiplying the ratio by a predetermined estimate of a concentration of carbon dioxide in the column, to provide a measurement of the concentration of the second gas.
17. 17. The method according to claim 16, wherein the second gas is carbon monoxide.
18. 18. The method according to claim 16, wherein: the second gas is a hydrocarbon. The method according to claim 16, wherein the second gas is a hydrocarbon, further comprising: multiplying the hydrocarbon concentration measurement by a factor determined experimentally. The method according to claim 16, wherein: P1507 / 99MX the second gas is a nitrogen oxide. The method according to claim 16, wherein: the second gas is water vapor. The method according to claim 16, wherein the predetermined estimate is in the range of about 13 percent to about 18 percent based on the volume of the exhaust gas column. The method according to claim 16, wherein: the predetermined estimate is in a range of about 14 percent to about 16 percent based on the dry volume of the exhaust gas column. The method according to claim 16, wherein: the predetermined estimate is in a range of about 12 percent to about 14 percent based on the wet volume of the exhaust gas column. P1507 / 99 X