US 4,245,977 A · Method and apparatus for hydrocarbon flame ignition and detection

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.

Claims19

Dependent claims

For use in a hydrocarbon fuel burner assembly of the type including a burner for developing a flame in an adjacent flame zone and means conducting combustible hydrocarbon fuel to the burner, a flame ignition and detection system comprising:

a pair of electrically conductive opposing face members positioned in the flame zone in a spaced-apart, gap-defining relationship to contact a flame occupying the flame zone, one of the face members being sufficiently electrically resistive to self-heat in response to current flow therethrough;
means adapted to coupling a power source across the electrically resistive face member and including switch means for selectively decoupling one end of the electrically resistive face member from one side of the power source;
impedance means for coupling the second face member to said one side of the power source;
the switch means being operable to initially couple said one end of the resistive face member to the power supply to thermally ignite the combustible gas;
the switch means being subsequently operable to decouple said one end of the resistive face member from the power source to impress a substantial portion of the power source voltage across the gap and the impedance means, an electrical circuit path being completed by the presence of the flame, a signal in said circuit path indicative of the presence of the flame being thereby produced;
and
switch operating means responsive to the absence of the flame indicative signal to operate the switch means and couple said one end of the face member to the power supply to thermally ignite the combustible fuel.

4 more elements

Dependencies are inferred from the claim text.

Method and apparatus for hydrocarbon flame ignition and detection

Life of this patent

Method and apparatus for hydrocarbon flame ignition and detection

Life of this patent

Abstract

Claims19