In situ fuel-to-air ratio (FAR) sensor for combustion using a Fourier based flame ionization probe
AssigneeIntellihot, Inc.
InventorsSridhar Deivasigamani, Sivaprasad Akasam, Quang-Viet Nguyen
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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.
Claims18
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 disposed at a voltage level and feeding said more than one excitation frequency component via a device 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.
A device configured 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 device comprises a controller configured for:
- (a) generating more than one excitation frequency component disposed at 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.
Dependencies are inferred from the claim text.