2.23. IGNITERS

Gas turbine igniters come in many sizes and shapes depending upon the duty they will be subjected to. The electrodes of the plugs used with high-energy ignition systems must be able to accommodate a current of much higher energy than the electrodes of conventional spark plugs are capable of handling. Although the high-energy current causes more rapid igniter-electrode erosion than that encountered in reciprocating-engine spark plugs, this is not a major disadvantage, because of the relatively short time that the ignition system is in operation. Most igniter plugs used in turbine engines are of the annular-gap type, shown in figure 2.16.

Figure 2.16. Annular Gap Igniter Plug.

The annular-gap igniter plug protrudes slightly into the combustion chamber liner to provide an effective spark. Another type of igniter is the constrained-gap plug which does not closely follow the face of the plug; instead it tends to jump in an arc which carries it beyond the face of the chamber liner. Because the constrained-gap plug does not have to protrude into the liner, the electrode operates at a cooler temperature than that of the annular-gap plug.

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