An igniter of a gas turbine burner, which relates to the invention, is known from. EP 1 892 474 A1, for example. The burner which is described therein comprises a pilot burner which can be ignited with the aid of an igniter as soon as a combustible gas or combustible substance mixture flows through the pilot burner into the combustor of a gas turbine. The igniter which is known therefrom essentially comprises two ignition electrodes, extending parallel to each other, which in the region of the fuel outlet of the pilot burner are bent in relation to each other and have their smallest gap there in order to be able to generate an ignition spark in the region of the fuel outlet, by means of which the fuel or the mixture can be ignited. For generating the ignition spark, a sufficiently high alternating voltage, which is made available by an ignition transformer, is customarily applied to the two electrodes. The ignition voltage in this case may be several kilovolts (kV).
Damage or bending of one or both ignition electrodes, which are attached to the pilot burner, during transporting or installation can negatively affect the functional performance of the ignition electrodes. Furthermore, on account of thermally induced expansions, cracks may occur in the insulation of the ignition electrodes or in the worst case the ignition electrodes may break so that despite an applied ignition voltage the igniter provides no ignition spark at the fuel outlet of the pilot burner. Equally, it is possible that after a so-called off-line compressor wash the electrodes are still wetted by a compressor washing fluid which also prevents the generation of an ignition spark despite an applied ignition voltage on account of ensuing creep currents. These defects can lead to failed starts which are undesired and also possibly damaging for the gas turbine.
For monitoring the igniters and the ignition spark, a device is known from U.S. Pat. No. 4,760,341. The device monitors the duration and the amplitude of the ignition spark and also the negative portion of the waveform of the spark charge. The igniter state, or the ignition spark, is recognized as being in accordance with specification if the duration of the ignition spark does not exceed a maximum time, the amplitude of the ignition spark has a minimum value and at the same time the negative portion exceeds an acceptable minimum value. It is disadvantageous that this device is not suitable for monitoring the ignition process in the case of gas turbines.
USPTO Backgrounds
USPTO Backgrounds