Burner including an electrical permittivity or electrical capacitance flame sensor

A burner, comprising:

• a fuel source;
• an oxidant source;
• a wall defining an mixing volume, the mixing volume configured to receive fuel and oxidant respectively from the fuel source and the oxidant source, the mixing volume further configured to convey the fuel and oxidant to facilitate mixture of the fuel and oxidant into a fuel-oxidant mixture;
• an ignition source oriented to ignite the fuel-oxidant mixture to produce a flame in a flame region defined by a flame holder;
• at least a first electrode and a second electrode arranged adjacent to the flame region, the first electrode configured to broadcast an excitation signal to produce a time-varying electromagnetic field across the flame region, the second electrode being configured to receive a detection signal, the detection signal including the broadcast excitation signal as affected by a change in electrical permittivity or electrical capacitance in the flame region;
• and
• a control circuit configured to generate the excitation signal and provide the excitation signal to the first electrode, to compare the detection signal to a threshold detection signal, and to produce a binary result signal indicating a presence or an absence of the flame.

A burner system, comprising:

• a main fuel source configured to output a fuel stream;
• an oxidant source configured to output an oxidant to mix with the fuel stream;
• a flame sensor including:
• a first sensor electrode positioned adjacent to a flame region defined by a flame holder;
• a second sensor electrode positioned adjacent to the flame region;
• and
• a sensor controller respectively coupled to the first and the second sensor electrodes via first and second electrical leads, the sensor controller including:
• a first electrical filter configured to protect circuitry in the sensor controller from electrostatic discharge;
• wherein the first and the second sensor electrodes and the sensor controller are configured to cooperate to measure the presence or absence of a flame supported by a mixture of the fuel stream and the oxidant.

A method for flame sensing, comprising:

• supporting first and second sensor electrodes adjacent to a flame region;
• applying a time varying voltage to the first sensor electrode to produce a broadcast signal that propagates through the flame region;
• receiving the broadcast signal, modified according to the presence or absence of a flame in the flame region, with the second sensor electrode;
• converting the received signal into a digital received signal;
• analyzing the digital received signal to determine a state of a flame in the flame region;
• and
• outputting digital data corresponding to the state.