Method of measuring in situ differential emissivity and temperature

• US 20070047615A1
• Filed: 09/01/2005
• Published: 03/01/2007
• Est. Priority Date: 09/01/2005
• Status: Active Grant

• Current Assignee: Siemens Energy Incorporated (Siemens AG)
• Original Assignee: Siemens Power Generation, Inc.
• Inventors: Twerdochlib, Michael
• Granted Patent: US 7,632,012 B2
• Time in Patent Office: Days
• US Class Current: 374/121
• CPC Class Codes: G01J 2005/0074 having separate detection of emissivity
• CPC Class Codes: G01J 5/0003 for sensing the radiant heat transfer of samples, e.g. emittance meter
• CPC Class Codes: G01J 5/532 using a reference heater of the emissive surface type, e.g. for selectively absorbing materials
• CPC Class Codes: G01J 5/602 using selective, monochromatic or bandpass filtering

Abstract

A method for measuring the differential emissivity between two sites on the surface of a body and the temperature of the two sites. The method includes a plurality of measurements of the infrared radiation arising from each of the two sites under a number of different conditions. Some of the measurements include irradiation by external infrared radiation at a known wavelength and intensity. The infrared radiation arising from each of the sites may include emitted radiation, reflected ambient radiation, and reflected external radiation. Additionally, the temperature determined using the method described can be used to calibrate infrared imaging devices used to inspect the entire body.

Claims

1. A method of measuring the in situ differential emissivity between two sites on a surface of an object, comprising:

detecting infrared radiation arising at a first wavelength from a first site on a surface of a body;

detecting infrared radiation arising at said first wavelength from said first site while said first site is irradiated by external infrared radiation at said first wavelength;

detecting infrared radiation arising at said first wavelength from a second site on the surface of said body;

detecting infrared radiation arising at said first wavelength from said second site while said second site is irradiated by external infrared radiation at said first wavelength; and

determining an in situ differential emissivity value based on the detection of infrared radiation arising from said first site and said second site.

2. The method of claim 1, wherein said first site and said second site are located in a highly reflected environment.

3. The method of claim 1, wherein said body is a turbine component.

4. The method of claim 3, wherein said turbine component is a turbine vane.

5. The method of claim 1, wherein said infrared radiation is detected using a device capable of narrow-band infrared radiation detection.

6. The method of claim 1, wherein said external infrared radiation is steady-state infrared radiation.

7. The method of claim 1, wherein said first site and said second site are in substantial proximity to one another.

8. A method of measuring temperature comprising:

detecting infrared radiation arising at a first wavelength from a first site on a surface of a body;

detecting infrared radiation arising at said first wavelength from said first site while said first site is irradiated by external infrared radiation at said first wavelength;

detecting infrared radiation arising at said first wavelength from a second site on the surface of said body;

detecting infrared radiation arising at said first wavelength from said second site while said second site is irradiated by external infrared radiation at said first wavelength;

detecting infrared radiation arising at a second wavelength from each of said first site and said second site; and

determining a temperature of said first or second site based on the detection of infrared radiation arising from said first site and said second site.

9. The method of claim 8, wherein said first site and said second site are located in a highly reflected environment.

10. The method of claim 8, wherein said body is a turbine component.

11. The method of claim 10, wherein said turbine component is a turbine vane.

12. The method of claim 8, wherein said infrared radiation is detected using a device capable of narrow-band infrared detection at said first wavelength, said second wavelength, or both.

13. The method of claim 8, wherein said external infrared radiation is irradiated at steady-state for irradiation of at least one of said first wavelength and said second wavelength.

14. The method of claim 8, wherein said first site and said second site are in substantial proximity to one another.

15. The method of claim 8, further comprising, detecting the infrared radiation arising at said second wavelength from each of said first site and said second site while each site is irradiated by external infrared radiation at said second wavelength.

17. The method of claim 8, wherein said determination of the temperature of said first site and said second site does not require knowledge of, or an estimate of, the emissivity of said first site or said second site.

18. The method of claim 8, wherein said determination of temperature of said first site and said second site does not require knowledge of, or an estimate of, the impinging radiation reflected by said first site or said second site.

16. The method of claim 16, wherein the external infrared radiation at said first wavelength and at said second wavelength are irradiated at the same intensity.

19. A method of calibrating an infrared imaging device, comprising:

determining the temperature for at least one location in the field-of-view of an infrared imaging device; and

using the temperature measurements from said at least one location to calibrate the infrared imaging device, wherein the temperature at each of said at least one locations is determined by a method comprising;

detecting infrared radiation arising at a first wavelength from a first site at each location;

detecting infrared radiation arising at said first wavelength from said first site at each location while said first site at each location is irradiated by external infrared radiation at said first wavelength;

detecting infrared radiation arising at said first wavelength from a second site at each location;

detecting infrared radiation arising at said first wavelength from said second site at each location while said second site at each location is irradiated by external infrared radiation at said first wavelength;

detecting infrared radiation arising at a second wavelength from said first site at each location and said second site at each location at a second wavelength; and

determining a temperature of said first or second site at each location based on the detection of infrared radiation arising from said first site and said second site at each location.

20. The method of claim 19, further comprising, using the temperature values at said at least one location to calibrate said infrared imaging device between said at least one location.