Method for measuring temperature, molecular number density, and/or pressure of a gaseous compound from a thermal device, and a thermal system

Patent metadata

Field	Value
Publication number	US-9857345-B2
Application number	US-201414554902-A
Country	US
Kind code	B2
Filing date	Nov 26, 2014
Priority date	Nov 26, 2013
Publication date	Jan 2, 2018
Grant date	Jan 2, 2018

Abstract

A method for measuring, from a thermal device, temperature, molecular number density, and/or pressure of a gaseous compound as function of distance, the gaseous compound absorbing at least some light. The method comprises generating, for a first wavelength band and a second wavelength band, a pulse sequence comprising a light pulse or light pulses, guiding the pulse sequence into the thermal device, and measuring, as function of time, the intensity of the scattered light at the first wavelength band and at the second wavelength band. The method further comprises determining information indicative of the differential absorption between the two wavelengths bands using measured intensities and determining the temperature, the molecular number density, and/or the pressure of the gaseous compound using the information indicative of the differential absorption between the two wavelengths bands. A thermal system arranged to carry out the method.

First claim

The invention claimed is:

1. A method for measuring at least a temperature and molecular number density of a gaseous compound as a function of distance, the gaseous compound absorbing at least some light, the method comprising:
selecting a first wavelength band, a second wavelength band, and a third wavelength band using information on a spectrum of an absorption coefficient of the gaseous compound and/or the temperature dependence thereof;
generating, for the first wavelength band, the second wavelength band, and the third wavelength band, a pulse sequence comprising a light pulse or light pulses, wherein the pulse sequence comprises a supercontinuum light pulse comprising light having continuously multiple wavelengths in the first wavelength band and the second wavelength band;
guiding the pulse sequence into a thermal device, wherein the thermal device surrounds some gaseous mixture, the gaseous mixture comprising the gaseous compound and scattering particles, whereby
molecules of the gaseous compound absorb at least part of the light pulse or at least part of at least one of the light pulses, and
the scattering particles of the gaseous mixture scatter at least part of the light pulse or at least part of the light pulses of the pulse sequence at various moments of time at least to produce scattered light;

measuring, as a function of time, the intensity of the scattered light at the first wavelength band, the second wavelength band, and the third wavelength band;
determining information indicative of a differential absorption between at least two pairs of wavelengths bands selected from the three wavelength bands using the intensity of the scattered light at the first wavelength band, the intensity of the scattered light at the second wavelength band, and the intensity of the scattered light at the third wavelength band; and
determining, as a function of the distance using the information indicative of the differential absorption, at least the temperature and the molecular number density of the gaseous compound.

2. The method of claim 1 , further comprising:
selecting a wavelength band such that a molecular absorptance or an expected molecular absorptance for the wavelength band is at least 1%; and
selecting another wavelength band such that a molecular absorptance or an expected molecular absorptance for the other wavelength band is at most 99%.

3. The method of claim 1 , further comprising:
selecting the first wavelength band such that a total attenuation factor for the pulse sequence, the first wavelength band, and the gaseous compound has a first value; and
selecting the second wavelength band such that the total attenuation factor for the pulse sequence, the second wavelength band, and the gaseous compound has a second value, wherein
the first value is different from the second value, and
the molecular number density of the gaseous compound is determined as a function of the distance.

4. The method of claim 1 , further comprising:
selecting the first wavelength band such that a total attenuation factor for the pulse sequence, the first wavelength band, and the gaseous compound depends on the temperature in a first way; and
selecting the second wavelength band such that the total attenuation factor for the pulse sequence, the second wavelength band, and the gaseous compound depends on the temperature in a second way, wherein
the first way is different from the second way, and
the temperature of the gaseous compound is determined as a function of the distance.

5. The method of claim 1 , wherein
the gaseous compound comprises at least one of steam (H 2 O), oxygen (O 2 ), carbon dioxide (CO 2 ), carbon monoxide (CO), ammonia (NH 3 ), nitrogen oxide (NO X ), and sulfur oxide (SO X ).

6. The method of claim 1 , wherein
the first wavelength band or the second wavelength band comprises wavelengths from the range 750 nm to 2000 nm, and/or
a linear size of the space is at most 50 m, and/or
the duration of a light pulse of the pulse sequence is at most 10 ns, a sampling rate at which the intensities of the scattered light is detected is at least 100 MHZ, and the pulse response of a detector arrangement used for the measuring of the intensity of the scattered light is less than 5 ns, and/or
the energy of a light pulse of the pulse sequence is at least 0.01 μJ, and at most 1 J.

7. The method of claim 1 , further comprising:
selecting the first wavelength band such that a total attenuation factor for the pulse sequence, the first wavelength band, and the gaseous compound has a first value, and such that the total attenuation factor for the pulse sequence, the first wavelength band, and the gaseous compound depends on the temperature in a first way;
selecting the second wavelength band such that the total attenuation factor for the pulse sequence, the second wavelength band, and the gaseous compound has a second value, and such that the total attenuation factor for the pulse sequence, the second wavelength band, and the gaseous compound depends on the temperature in a second way;
selecting the third wavelength band such that the total attenuation factor for the pulse sequence, the third wavelength band, and the gaseous compound has a third value, and such that the total attenuation factor for the pulse sequence, the third wavelength band, and the gaseous compound depends on the temperature in a third way, wherein
the first way is different from the second way, and
the second value is different from the third value; and

determining the temperature and the molecular number density of the gaseous compound as a function of the distance.

8. The method of claim 1 , further comprising:
selecting a further wavelength band using information on the spectrum of the absorption coefficient of a further gaseous compound;
generating the pulse sequence also for the further wavelength band;
measuring, as a function of time, the intensity of the scattered light at the further wavelength band;
determining information indicative of the differential absorption between at least two pairs of wavelengths bands selected from the at least four wavelength bands using the measured intensities; and
determining the temperature, the molecular number density, and/or the pressure of the further gaseous compound as a function of the distance using the information indicative of the differential absorption between the further wavelength band and another wavelength band.

9. The method of claim 1 , wherein
the temperature of the gaseous compound is at least 400° C.

10. The method of claim 9 , wherein the temperature of the gaseous compound is at most 1200° C.

11. The method of claim 1 , further comprising:
guiding the pulse sequence in a first direction;
generating, for a first wavelength band and a second wavelength band, a further pulse sequence comprising a light pulse or light pulses;
guiding the further pulse sequence into the thermal device in a second direction, wherein the second direction forms an angle with the first direction, whereby
molecules of the gaseous compound absorb at least part of the light pulse or at least part of the light pulses of the further pulse sequence, and
particles of the gaseous mixture scatter at least part of the light pulse or at least part of the light pulses of the further pulse sequence at various moments of time at least to produce further scattered light;

measuring, as a function of time, the intensity of the further scattered light at the first wavelength band;
measuring, as a function of time, the intensity of the further scattered light at the second wavelength band;
determining information indicative of the differential absorption b

Assignees

• Valmet Power Oy
• Valmet Technologies Oy

Inventors

• Toivonen Juha
• Aalto Antti
• Sarén Matti
• Roppo Juha

Classifications

• F23N2225/08

  temperature · CPC title

• F23N2225/04

  pressure · CPC title

• F23N5/082

  using electronic means · CPC title

• G01N33/0036 Primary

  specially adapted to detect a particular component (physical analysis of gaseous biological material G01N33/497) · CPC title

• F23N5/022

  using electronic means (F23N5/04 - F23N5/14 take precedence) · CPC title