Importance

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Abstract

A method and apparatus for hydrocarbon flame ignition and detection is disclosed utilizing a pair of flame-detecting electrodes positioned at the flame site in contact with the flame and in a spaced-apart relationship to accommodate, in the gap therebetween, essentially the flame's reaction zone. At least one of the electrodes may additionally serve as the ignition element and is, accordingly, sufficiently electrically resistive so as to undergo self-heating in response to current flow therethrough. A second aspect of the invention relates to the direct application of AC line voltage across the resistive electrode during the ignition phase and across the electrode gap during the detection phase. A third aspect of the invention concerns the thermal-heating of both electrodes by the flame to reduce both the ignition time and the 'wall quenching' effect of the otherwise cool electrode surface on the high-conductivity plasma in the reaction zone. In the detection phase of operation, substantially all of the voltage applied to the self-heating electrode during ignition is impressed across the electrode gap for maximum current flow by a novel switch arrangement. The contacting of the electrodes by flame permits a large current to flow through the gap owing to the high conductivity of the reaction zone and to the low capacitive reactance between the closely spaced electrodes.

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First Claim