Degradation of Silicon Nitride Glow Plugs in Various Environments Part 3: NGDI Engine

Providing a reliable hot surface ignition system (glow plug, GP ) for natural gas‐direct injection engines is challenging. This paper presents experimental results of aging all‐ceramic Si ₃ N ₄ ‐based GP s in an engine, continuing previously published results on electric and gas burner rigs. The microstructural modifications of the ceramic heater, leading to degradation and ultimately to failure, are effected by four synergistic mechanisms: electrical, chemical, mechanical, and thermal. GP lifetime in engine follows the general Arrhenius law, with activation energy of 5.2 eV, (vs 9.1 V on burner rig and 13.8 eV on electric rig, as reported previously), suggesting additional factors contributing to GP failure in the engine.