Diffusion and heat conduction in the vicinity of plasma plug igniters

It is shown that the blast wave from a pulsed linear arc inherently leaves flows in its wake which propagate as a cylindrical version of a conventional hyrdodynamic 'puff'. These flows are generated by the transition of the initially cylindrical shock wave to an ultimate spherical configuration. Schlieren cinematography of the expanding flows yields results which are in good agreement with a theory based on a single blast wave model of wake flow formation. The results both support a previous hypothesis of Chomiak (1979) on the subject of spark ignition and establish a mechanism which accounts for the observed increase in the rate of combustion when short duration sparks are used.

Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Electrically induced turbulence-the short duration spark

Haley

Smy

1989

“…It can also be expected to facilitate the transport of radicals from the jet plasma to the reactive region at the front. Thus it does seem most likely (Cetegen et a1 1980, Simeoni andSmy 1986) that jet-induced turbulence does play an important part in determining the ability of the igniter to enhance combustion.…”

Section: Introductionmentioning

confidence: 99%

Structure of the pulsed plasma jet

Smy

Clements

Oppenheim

et al. 1987

The flow characteristics of a pulsed plasma jet have been studied using streak and conventional (time-resolved) photography of the luminous plasma jet. The nature and placement of the shock structure observed in these photographs is that expected of under-expanded jet flow. Direct measurements of the gas pressures at the nozzle of the cavity (made using an optical technique) are in good agreement with those calculated from the observed shock structure. A second set of pressure measurements, of the stagnation pressure throughout the jet, shows good agreement with the calculated pressure behind the bow shock which is located at the front of the expanding jet. On the basis of these results, a simple model of jet penetration is proposed in which the jet 'tunnels' its way into the dense surrounding air. The implications of this model, in view of its similarities to other well studied phenomena such as astrophysical jets, are discussed in terms of the turbulence created by the jet, a factor which could be most significant when such jets are used as igniters.

“…The jet eventually dissipates as a moving cloud of turbulent gas which is generally known as a 'puff'. The turbulence within the puff appears to be responsible via one or more mechanisms (Simeoni and Smy 1986) for the major benefit of using plasma plug ignition. which is a noticeable increase in the initial rate of combustion (Cetegen et a1 1980).…”

mentioning

confidence: 99%

Use of a plasma jet igniter as a gas pump

Tokharski¹,

West²,

Smy³

1988

A coaxial plasma plug igniter is shown to function as a gas pump when operated repetitively at frequencies up to 30 Hz. Measurements of the rate of gas entrainment when the igniter is injected into various tubes are in excellent agreement with previous measurements of the momentum imparted to the surrounding gas by an igniter. Steady velocities of the order of 1 m s-1 are achieved in the vicinity of the igniter. It is believed that this ability to generate steady flows may be useful in furnaces and in some other combustion applications in that it should improve ignition performance with fuel rich or stratified fuel-air mixtures either by directly drawing in air via a tube or by stirring the mixture in the combustion chamber.