Investigation of novel ultraviolet detecting system used in aero magneto ignition energy monitoring

Ignition energy is one of the important measured parameter for aero magneto ignition system. Too large ignition energy will make ablation of spark plug electrode of ignition system, shorten the life of spark plug, and even bring pre-ignition and knock to decrease the performance of aero engine. Too small ignition energy will worsen the combustion state, reduce starting ability, and even decrease the economic and dynamic performance of aero engine. It is necessary to monitor ignition energy of the aero magneto. Two conventional ignition energy measured methods, the calorimeter method and the discharge voltage method, are introduced. And the large measured errors and the error reasons of the two conventional measured methods are discussed either. In this paper, a novel ultraviolet (UV) ignition energy detecting system is presented. The ignition energy detecting principle of UV phototube is investigated and the UV ignition energy detecting system is established. The discharge voltage and discharge current are measured, and the maximal ignition energy of 87.29 mJ is calculated by digital integration of the discharge voltage and current, compared to the measured maximal ignition energy of 79.46 mJ obtained by the novel UV detecting system. The reason that the measured ignition energy is less than that of the calculated one is given either.