Various embodiments include a control system comprising: an ionization electrode; a flame sensor; a first signal conditioning circuit for the ionization electrode; a second signal conditioning circuit for the flame sensor; an output unit; and a processor. The processor: receives a first and a second ionization signal indicative of ionization currents from the first signal conditioning circuit; receives a first and a second flame signal indicative of radiations originating from a flame via the second signal conditioning circuit; produces a derived ionization signal as a function of the first and the second ionization signals; produces a derived flame signal as a function of the first and the second flame signals; determines if a flame lift-off condition exists based on the derived ionization signal and the derived flame signal; and if a flame lift-off condition exists, produces a safety signal and transmits the safety signal to the output unit.

A burner includes a flame sensor configured to detect at least one of permittivity, capacitance, or resistance across a flame region. The permittivity, capacitance, or resistance is used to determine the presence or absence of the flame in a combustion system. A combustion system supports a combustion reaction. The combustion system utilizes a combustion sensor, and optionally a plasma generator to stabilize the combustion reaction. A controller receives sensor signals from the combustion sensor and controls the plasma generator to stabilize the combustion reaction responsive to the sensor signals. The plasma generator stabilizes the combustion reaction by generating a plasma.

A system for measuring a fuel-oxidant equivalence ratio includes at least one wall defining a gas volume including fuel and air. A gas ionization source is configured to cause a formation of ions in the gas. A power supply is configured to output a time-varying voltage. A first electrode is disposed in the gas volume, operatively coupled to the power supply, and configured to carry the time-varying voltage. A second electrode is arranged to operatively couple to a signal output by the first electrode after the signal passes through the gas volume. Characteristics of the received signal indicate the fuel-oxidant equivalence ratio.

An optical flame-sensor includes an optical circulator, an optical-fiber cavity, and a first optical sensor. The optical circulator includes a first port, a second port, and a third port. The first port is configured to receive an optical signal. The second port is configured to output the optical signal received at the first port. The third port is configured to output the input to the second port. The optical-fiber cavity includes a cavity proximal-end optically coupled to the second port, and a mirror at a cavity distal-end, such that a cavity optical signal output by the optical-fiber cavity is the input to the second port. The first optical sensor is optically coupled to the third port to quantify the cavity optical signal.

Various embodiments include a control system comprising: an ionization electrode; a flame sensor; a first signal conditioning circuit for the ionization electrode; a second signal conditioning circuit for the flame sensor; an output unit; and a processor. The processor: receives a first and a second ionization signal indicative of ionization currents from the first signal conditioning circuit; receives a first and a second flame signal indicative of radiations originating from a flame via the second signal conditioning circuit; produces a derived ionization signal as a function of the first and the second ionization signals; produces a derived flame signal as a function of the first and the second flame signals; determines if a flame lift-off condition exists based on the derived ionization signal and the derived flame signal; and if a flame lift-off condition exists, produces a safety signal and transmits the safety signal to the output unit.

A system for measuring a fuel-oxidant equivalence ratio includes at least one wall defining a gas volume including fuel and air. A gas ionization source is configured to cause a formation of ions in the gas. A power supply is configured to output a time-varying voltage. A first electrode is disposed in the gas volume, operatively coupled to the power supply, and configured to carry the time-varying voltage. A second electrode is arranged to operatively couple to a signal output by the first electrode after the signal passes through the gas volume. Characteristics of the received signal indicate the fuel-oxidant equivalence ratio.

A flame sensor detects the presence of a flame in a combustion system in which the flame emits light. The flame sensor includes a body connectable with the combustion system. A photodetector is supported in the body. The photodetector responds to light emitted by the flame and generates an electrical signal proportional to an intensity of the light. A window is supported in the body and located between the combustion system and photodetector. The window is susceptible to contamination from the combustion system and the contamination may decrease sensitivity of the photodetector. A light source is supported in the body. The light source emits light so that a predetermined amount of the light emitted by the light source reflects into the photodetector when contamination is present on the window and the photodetector generates a signal indicative of contamination on the window.

A burner includes a flame sensor configured to detect at least one of permittivity, capacitance, or resistance across a flame region. The permittivity, capacitance, or resistance is used to determine the presence or absence of the flame in a combustion system. A combustion system supports a combustion reaction. The combustion system utilizes a combustion sensor, and optionally a plasma generator to stabilize the combustion reaction. A controller receives sensor signals from the combustion sensor and controls the plasma generator to stabilize the combustion reaction responsive to the sensor signals. The plasma generator stabilizes the combustion reaction by generating a plasma.

A flame sensor detects the presence of a flame in a combustion system in which the flame emits light. The flame sensor includes a body connectable with the combustion system. A photodetector is supported in the body. The photodetector responds to light emitted by the flame and generates an electrical signal proportional to an intensity of the light. A window is supported in the body and located between the combustion system and photodetector. The window is susceptible to contamination from the combustion system and the contamination may decrease sensitivity of the photodetector. A light source is supported in the body. The light source emits light so that a predetermined amount of the light emitted by the light source reflects into the photodetector when contamination is present on the window and the photodetector generates a signal indicative of contamination on the window.