Shock velocity in weakly ionized nitrogen, air, and argon

Abstract

The goal of this research was to determine the principal mechanism(s) for the shock velocity increase in weakly ionized gases. This paper reports experimental data on the propagation of spark-generated shock waves (1<Mach<3) into weakly ionized nitrogen, air, and argon glow discharges (1<p<20Torr). In order to distinguish between effects due solely to the presence of electrons and effects due to heating of the background gas via elastic collisions with electrons, the weakly ionized discharge was pulsed on/off. Laser deflection methods determined the shock velocity, and the electron number density was collected using a microwave hairpin resonator. In the afterglow of nitrogen, air, and argon discharges, the shock velocity first decreased, not at the characteristic time for electrons to diffuse to the walls, but rather at the characteristic time for the centerline gas temperature to equilibrate with the wall temperature. These data support the conclusion that the principal mechanism for the increase in shock velocity in weakly ionized gases is thermal heating of the neutral gas species via elastic collisions with electrons.

Shock wave interaction with pulsed glow discharge and afterglow plasmas

“…Therefore, it is nearly impossible to completely isolate the plasma-specific effects from the thermal mechanisms in a steady-state dc discharge. However, there have been some work on isolating the thermal mechanisms from the plasma-specific effects by using a pulsed discharge [19,20,23]. The results of these measurements clearly indicate that the shock wave dispersion and acceleration in plasma are associated with the increase in the discharge gas temperature.…”

“…jump connected with the shock wave can result in local neutral gas heating causing the shock dispersion and the shock-speed increase [14][15][16]. Others argued that the thermal non-uniformities and temperature effects are the dominant mechanisms for the observed shock wave broadening and velocity changes in plasmas [17][18][19][20][21][22][23][24]. In a glow discharge plasma column, the temperature gradients (longitudinal and radial) and thermal non-uniformities are always present.…”

Characterization of internal discharge shock waves of gas‐insulated switchgears using shadowgraphy

“…Zeldovich systematically described by the properties of high temperature, pressure, velocity, and energy density in discharge shock waves [16]. Numerous recent studies, involving different gases [17][18][19][20][21] and discharge types [22][23][24], have thoroughly investigated the structure, propagation speed, post-wave parameters, and other characteristics of gas discharge shock waves [25]. However, there is a dearth of studies on the characteristics of SF 6 gas discharge shock waves inside a GIS.…”

Experimental Study of Shock Wave Dynamics in Magnetized Plasmas

“…13 In this estimation the characteristic decay time for the electrons is given by ( ) , where kT e is the electron temperature in eV, μ i is the mobility of the ions, and the glow discharge tube radius a = 1.75 cm. 8 The definition of the reduced ion mobility μ oi is given in Ref. 14 is the discharge gas temperature in K (assuming T i ≈ T g ).…”

“…[1][2][3] Another group of researches showed by combined experiments and simulations that the thermal non-uniformity and temperature variation in the discharge tube have been the primary cause of the shock wave modification in plasmas. [4][5][6][7][8] They have isolated the thermal effects from all other mechanisms in the plasma by pulsing the discharge on a short time interval.…”