The Railplug: A New Ignitor for Internal Combustion Engines

Abstract

A miniaturized railgun, termed the >railplug,> has been developed for use as an ignitor of combustible mixtures in engines. The device drives a plasma armature in a multishot mode with the aim of creating a line-source for ignition rather than the point source provided by traditional spark plugs. Railplugs have been fabricated in both parallel rail and co-axial rail geometries. The railplug differs from most plasma armature railguns in two striking ways: (1) no fuse or pellet is used to initially establish the plasma (the armature is simply the arc created by a high-voltage pulse), and (2) it operates over a range of elevated pressures (up to 500 psi). Consequently, the railplug power supply must provide a high voltage spike to breakdown the gap between the rails followed by a sustaining voltage that supplies current to drive the arc down the rails. Conceptually, this is the equivalent of combining the electrostatic problem of a sparkplug with the electrodynamic one of a railgun. Two power supply options that do this are outlined, as well as details of railplug geometries. Successes to date have demonstrated the firing of plugs for over 10{sup 4} shots at delivered arc energies of 1 J per shot. Rep rates have been demonstrated up to 50 Hz.