In situ fuel-to-air ratio (FAR) sensor for combustion using a fourier based flame ionization probe

Patent metadata

Field	Value
Publication number	US-10732147-B2
Application number	US-201815888047-A
Country	US
Kind code	B2
Filing date	Feb 4, 2018
Priority date	Feb 4, 2018
Publication date	Aug 4, 2020
Grant date	Aug 4, 2020

Abstract

A means of detecting the in-situ fuel-to-air-ratio (FAR) in a combustor or flame zone using a Fourier-based flame ionization probe is presented. The use of multiple excitation frequencies and its detection at certain frequencies or combinations of harmonics of those excitation frequencies, namely, the inter-modulation distortion, provides a novel means of extracting a high signal-to-noise ratio (SNR) FAR measurement in a combustor.

First claim

What is claimed herein is:

1. A method for establishing a relationship between inter-modulation distortion amplitude and fuel-to-air ratio (FAR) of a fuel and air combustion system having a combustion chamber, said method comprising:
(a) generating more than one excitation frequency component via a device into the combustion chamber, amplifying said more than one excitation frequency component to achieve a voltage level and feeding said more than one excitation frequency component into the combustion chamber to produce frequency responses for FAR conditions comprising a first set of conditions ranging from fuel-to-air ratios above stoichiometric with flame to fuel-to-air ratios below stoichiometric with flame and a second set of conditions ranging from fuel-to-air ratios above stoichiometric without flame to fuel-to-air ratios below stoichiometric without flame;
(b) from said frequency responses, calculating Fourier frequency components of said frequency responses;
(c) subtracting a signal corresponding to a FAR condition without flame from each of said Fourier frequency components of said frequency responses; and
(d) taking a combined sum of the amplitudes of the Fourier frequencies of the difference-frequency component and sum-frequency component of said more than one excitation frequency component to produce a relationship between inter-modulation distortion amplitude and FAR that is monotonic.

2. The method of claim 1 , further comprising normalizing the amplitude of each of said Fourier frequency components of said frequency responses by the corresponding excitation frequency component.

3. The method of claim 1 , wherein said more than one excitation frequency component is a signal of a frequency selected from a frequency of about 1 kHz, 5 kHz, 3 kHz and 5 kHz.

4. The method of claim 1 , wherein said voltage level is a level ranging from about +/−20 v to about +/−50 v signal.

5. The method of claim 1 , wherein said more than one excitation frequency component are two excitation frequency components.

6. The method of claim 1 , said feeding step comprises feeding said more than one excitation frequency component through a flame ionization detector.

7. The method of claim 1 , wherein said device is a flame ionization probe.

8. A method for establishing a relationship between inter-modulation distortion amplitude and fuel-to-air ratio (FAR) of a fuel and air combustion system having a combustion chamber, said method comprising:
(a) generating more than one excitation frequency component via a device into the combustion chamber, amplifying said more than one excitation frequency component to achieve a voltage level and feeding said more than one excitation frequency component into the combustion chamber to produce frequency responses for FAR conditions comprising a first set of conditions ranging from fuel-to-air ratios above stoichiometric with flame to fuel-to-air ratios below stoichiometric with flame and a second set of conditions ranging from fuel-to-air ratios above stoichiometric without flame to fuel-to-air ratios below stoichiometric without flame;
(b) from said frequency responses, calculating Fourier frequency components of said frequency responses;
(c) subtracting a signal corresponding to a FAR condition without flame from each of said Fourier frequency components of said frequency responses;
(d) normalizing the amplitude of each of said Fourier frequency components of said frequency responses by the corresponding excitation frequency component; and
(e) taking a combined sum of the amplitudes of the Fourier frequencies of the difference-frequency and sum-frequency component of said more than one excitation frequency component to produce a relationship between inter-modulation distortion amplitude and FAR that is monotonic.

9. The method of claim 8 , wherein said more than one excitation frequency component is a signal of a frequency selected from a frequency of about 1 kHz, 5 kHz, 3 kHz and 5 kHz.

10. The method of claim 8 , wherein said voltage level is a level ranging from about +/−20 v to about +/−50 v signal.

11. The method of claim 8 , wherein said more than one excitation frequency component are two excitation frequency components.

12. The method of claim 8 , said feeding step comprises feeding said more than one excitation frequency component through a flame ionization detector.

13. The method of claim 8 , wherein said device is a flame ionization probe.

Assignees

• Deivasigamani Sridhar
• Akasam Sivaprasad
• Nguyen Quang Viet
• Intellihot Inc

Inventors

• Deivasigamani Sridhar
• Akasam Sivaprasad
• Nguyen Quang-Viet

Classifications

• G01N27/626 Primary

  using heat to ionise a gas · CPC title