Method and apparatus for remote measurement of exhaust gas

• US 5,831,267 A
• Filed: 02/24/1997
• Issued: 11/03/1998
• Est. Priority Date: 02/24/1997
• Status: Expired due to Term

• Current Assignee: Envirotest Corp. (Opus Group AB)
• Original Assignee: Envirotest Systems Corporation (Stone Rivet, Inc.)
• Inventors: Gray, Michael N., Peterson, Jay C., Nelson, David R., Jack, Michael D.
• Primary Examiner(s): Porta, David P.
• Application Number:
  US08/806,870
• Time in Patent Office: 617 Days
• Field of Search: 250/338.5, 250/339.13, 250/372
• US Class Current: 250/338.5
• CPC Class Codes: G01N 2021/1793 Remote sensing
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis

Abstract

A method and apparatus for sensing a composition of an exhaust plume includes a light source that radiates an infrared light beam 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 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.

Claims

1. An apparatus for sensing a composition of an exhaust plume, comprising:

a light source that radiates an infrared light beam through said plume, said beam including a plurality of predetermined wavelengths;

a detector that detects said beam passing through said plume at said predetermined wavelengths, wherein a first of said predetermined wavelengths is associated with carbon dioxide and a second of said predetermined wavelengths is associated with a second gas;

means for computing a ratio of said second gas to carbon dioxide based upon said first and second detected wavelengths; and

a multiplier that multiplies said ratio by a predetermined estimation of a concentration of carbon dioxide in said plume, to provide a measurement of a concentration of said second gas.

2. The apparatus of claim 1, wherein:

said second gas is a hydrocarbon.

3. The apparatus of claim 1, wherein:

said second gas is carbon monoxide.

4. The apparatus of claim 1, wherein:

said second gas is an oxide of nitrogen.

5. The apparatus of claim 1, wherein:

said second gas is nitric oxide.

6. The apparatus of claim 1, wherein:

said predetermined estimation of carbon dioxide is in a range of about 13 percent to about 18 percent based upon the volume of the plume.

7. The apparatus of claim 1, wherein:

said predetermined estimation of carbon dioxide is in a range of about 14 percent to about 16 percent based upon the dry volume of the plume.

8. The apparatus of claim 1, wherein:

said predetermined estimation of carbon dioxide is in a range of about 12 percent to about 14 percent based upon the wet volume of the plume.

9. The apparatus of claim 1, wherein:

said detector comprises a plurality of photodetectors, each photodetector being sensitive to a band of wavelengths that includes only one of said predetermined wavelengths.

10. The apparatus of claim 1, wherein each detector comprises a photosensitive element and a filter disposed between said plume and the photosensitive element having a passband coinciding with a respective band of wavelengths.

11. The apparatus of claim 1, wherein said predetermined estimation of a concentration of carbon dioxide is experimentally obtained.

12. The apparatus of claim 1, wherein said second gas is a hydrocarbon, further comprising:

a multiplier that multiplies said measurement of concentration of hydrocarbon by an experimentally determined factor.

13. The apparatus of claim 1, wherein said second gas is a hydrocarbon and a third of said predetermined wavelengths is associated with nitrogen oxide, further comprising:

means for computing a ratio (R_NO/CO.sbsb.2) of said nitrogen oxide to carbon dioxide based upon said first and third detected wavelengths; and

a multiplier that multiplies said ratio (R_NO/CO.sbsb.2) by said predetermined estimation of a concentration of carbon dioxide in said plume, to provide a measurement of a concentration of said nitrogen oxide.

14. The apparatus of claim 1, wherein said exhaust plume is produced by burning a fuel and wherein said second gas is a hydrocarbon and a third of said predetermined wavelengths is associated with carbon monoxide, further comprising:

means for computing a second ratio (R_CO/CO.sbsb.2) of carbon monoxide to carbon dioxide based upon said first and third detected wavelengths; and

means for computing a concentration of said carbon monoxide in said plume from said first ratio and said second ratio (R_CO/CO.sbsb.2) based upon an assumption of a first C;

H ratio of fuel and a second C;

H ratio of the exhaust plume, said first and second C;

H ratios being different.

15. The apparatus of claim 14, wherein:

said first C;

H ratio is about 1.85 and said second C;

H ratio is about 2.33.

16. A method of sensing a composition of an exhaust plume from a moving vehicle, comprising the steps of:

radiating an infrared light beam through said plume, said beam including a plurality of predetermined wavelengths;

detecting said beam passing through said plume at said predetermined wavelengths, wherein a first of said predetermined wavelengths is associated with carbon dioxide and a second of said predetermined wavelengths is associated with a second gas;

computing a ratio of said second gas to carbon dioxide based upon said first and second detected wavelengths; and

multiplying said ratio by a predetermined estimation of a concentration of carbon dioxide in said plume, to provide a measurement of the concentration of said second gas.

17. The method of claim 16, wherein:

said second gas is carbon monoxide.

18. The method of claim 16, wherein:

said second gas is a hydrocarbon.

19. The method of claim 16, wherein said second gas is a hydrocarbon, further comprising:

multiplying said measurement of concentration of hydrocarbon by an experimentally determined factor.

20. The method of claim 16, wherein:

said second gas is an oxide of nitrogen.

21. The method of claim 16, wherein:

said second gas is water vapor.

22. The method of claim 16, wherein:

said predetermined estimation is in a range of about 13 percent to about 18 percent based upon the volume of the exhaust plume.

23. The method of claim 16, wherein:

said predetermined estimation is in a range of about 14 percent to about 16 percent based upon the dry volume of the exhaust plume.

24. The method of claim 16, wherein:

said predetermined estimation is in a range of about 12 percent to about 14 percent based upon the wet volume of the exhaust plume.