IR-based nitric oxide sensor having water vapor compensation
First Claim
1. A system for determining a concentration of NO in an exhaust plume, comprising:
- a source of electromagnetic radiation for directing radiation having a plurality of wavelengths along an optical path that passes through the plume;
first sensor means having an output for indicating an amount of absorption of the radiation, within a band of first wavelengths, that is due to the presence of NO in the plume;
second sensor means having an output for indicating an amount of absorption of the radiation, within a band of second wavelengths, that is due to the presence of water along the optical path; and
means, having inputs coupled to the outputs of said first sensor means and said second sensor means, for compensating the indicated absorption within the first band of wavelengths in accordance with the indicated absorption within the second band of wavelengths and in accordance with a predetermined NO absorption modifying factor.
14 Assignments
0 Petitions
Accused Products
Abstract
A system (10) for detecting nitric oxide (NO) within an exhaust plume (14) includes a source (18) for generating an optical beam (20) and for directing (22, 24) the optical beam through the exhaust plume, the optical beam having wavelengths within a predetermined band of wavelengths within the infrared (IR) radiation spectrum. The system includes a sensor (32)/filter (30) assembly having a first channel for determining a measured NO transmission value for a first predetermined band of wavelengths; a second channel for determining a measured water transmission value for a second predetermined band of wavelengths; a third channel for determining a measured reference transmission value for a third predetermined band of wavelengths selected so as not to be significantly absorbed by the exhaust plume; and a fourth channel for determining a measured combustion by-product transmission value for a fourth predetermined band of wavelengths. A data processor (38) is responsive to the outputs of the channels for determining an effective NO transmission value from the measured NO transmission value that is scaled by (a) the measured water transmission value, (b) a predetermined factor that compensates for absorption by water within the first predetermined band of wavelengths, and (c) the reference transmission value. The data processor is further operable for converting the effective NO transmission value to a relative NO concentration value using a predetermined calibration factor and for converting the relative NO concentration value to an actual NO concentration value utilizing the measured combustion by-product transmission value.
87 Citations
24 Claims
-
1. A system for determining a concentration of NO in an exhaust plume, comprising:
-
a source of electromagnetic radiation for directing radiation having a plurality of wavelengths along an optical path that passes through the plume; first sensor means having an output for indicating an amount of absorption of the radiation, within a band of first wavelengths, that is due to the presence of NO in the plume; second sensor means having an output for indicating an amount of absorption of the radiation, within a band of second wavelengths, that is due to the presence of water along the optical path; and means, having inputs coupled to the outputs of said first sensor means and said second sensor means, for compensating the indicated absorption within the first band of wavelengths in accordance with the indicated absorption within the second band of wavelengths and in accordance with a predetermined NO absorption modifying factor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. A method for determining a concentration of NO in an exhaust plume, comprising the steps of:
-
passing an optical beam through an exhaust plume, the optical beam having wavelengths within a predetermined band of wavelengths within the infrared radiation spectrum; determining a measured NO transmission value for a first predetermined band of wavelengths; determining a measured water transmission value for a second predetermined band of wavelengths; determining a measured reference transmission value for a third predetermined band of wavelengths selected so as not to be significantly absorbed by the exhaust plume; determining a measured combustion by-product transmission value for a fourth predetermined band of wavelengths; determining an effective NO transmission value from the measured NO transmission value that is scaled by (a) the measured water transmission value, (b) a predetermined factor that compensates for absorption by water within the first predetermined band of wavelengths, and (c) the reference transmission value; converting the effective NO transmission value to a relative NO concentration value using a predetermined calibration factor; and converting the relative NO concentration value to an actual NO concentration value utilizing the measured combustion by-product transmission value. - View Dependent Claims (11, 12, 13)
-
-
14. A system for detecting at least one predetermined pollutant within an exhaust plume, comprising:
-
means for generating an optical beam and for directing the optical beam through an exhaust plume, the optical beam having wavelengths within a predetermined band of wavelengths within the infrared radiation spectrum; first means for determining a measured NO transmission value for a first predetermined band of wavelengths; second means for determining a measured water transmission value for a second predetermined band of wavelengths; third means for determining a measured reference transmission value for a third predetermined band of wavelengths selected so as not to be significantly absorbed by the exhaust plume; fourth means for determining a measured combustion by-product transmission value for a fourth predetermined band of wavelengths; and a data processor having inputs coupled to an output of each of said first, second, third and fourth determining means, said data processor being responsive to said outputs for determining an effective NO transmission value from the measured NO transmission value that is scaled by (a) the measured water transmission value, (b) a predetermined factor that compensates for absorption by water within the first predetermined band of wavelengths, and (c) the reference transmission value; said data processor including means for converting the effecting NO transmission value to a relative NO concentration value using a predetermined calibration factor; and means for converting the relative NO concentration value to an actual NO concentration value utilizing the measured combustion by-product transmission value. - View Dependent Claims (15, 16, 17, 18, 19, 20)
-
-
21. A calibration cell for use in calibrating a pollution monitoring system, comprising:
-
a sealed housing having a plurality of compartments including a first compartment and a second compartment, said first and second compartments being separated by a movable partition; means for causing a movement of said partition, the movement causing a volume of said first compartment to increase while simultaneously causing a volume of said second compartment to decrease; a sealed reservoir coupled to said second compartment whereby a gas mixture is enabled to flow between said reservoir and said second compartment, said gas mixture including a plurality of by-products of combustion of a fuel;
whereinat least a portion of said housing and said partition are substantially transparent to a beam of electromagnetic radiation having wavelengths within a band of wavelengths employed by a pollution monitoring system such that the beam is enabled to pass through said first compartment, said second compartment, the gas mixture contained within said second compartment, and through said partition. - View Dependent Claims (22, 23, 24)
-
Specification