The plasma plume generated by a new type of high energy igniter known
as the railplug is examined. The railplug is a miniaturized railgun th
at has the potential for improving ignition characteristics of combust
ible mixtures in engines. The objective of the study is to gain an und
erstanding of the characteristics of the plasma created by a transpare
nt railplug and to validate a multidimensional computer simulation of
the plasma and shock fronts. The nature of the plume emitted by the ra
ilplug was examined for three levels of electrical energy while firing
into air at a pressure of 1 atm. The computer model is to be used to
predict trends in railplug performance for various railplug designs, e
nergies, and ambient conditions. The velocity of the plasma movement i
nside a transparent railplug was measured, as well as the velocity of
the plume ejected from the cavity. A shock is produced at the initiati
on point of the arc and propagates down the cavity, eventually exiting
the plug. The velocity of the shock was both measured experimentally
and simulated by the model. The computer simulation produces a mushroo
m-shaped plasma plume at the railplug exit similar to that observed in
the shadowgraph photos. The simulation also reproduced the toroidal c
irculation observed at the plug exit in the shadow-graphs, the radial
expansion, and the penetration depth of the plume. The trend of linear
ly increasing plasma kinetic energy with stored electrical energy pred
icted by the simulation was verified by shadowgraph photos. The agreem
ent between the experiments and the simulations suggests that the mult
idimensional model holds promise as a predictive design tool.