Long-spark discharge in mixing layer of two molecular co-flown gases

Summary form only given. A subject of consideration is the dynamic of filamentary longspark discharge generated along contact zone of two co-flown gases. The effects found are supposed to be applied for high-speed combustion enhancement due to the mixing acceleration of non-premixed multi-components flow.Experimental facility consists of blowdown wind tunnel PWT-50, system of the pulse-repetitive feeding, and rich set of diagnostics. Typical parameters of the discharge are: interelectrodes gap d=30-60mm; breakdown voltage U>100kV, pulse duration 1=5070ns, peak current I=l-3kA, pulse energy release E=1-3J. The power supply possesses an important feature: high speed of the voltage rise dU/dt>10sV/s. The experiments were made in ambient conditions and in high-speed flow V=100-600m/s. The discharge\´s filament location and dynamics in mixing layer depend on the discharge parameters and physical properties of gases involved. There was found experimentally that in two-phase flow the filamentary discharge strives for the location between two molecular gases, if the experimental arrangement allows it. The physical mechanism can be considered as the following. The first stage of the spark breakdown is the multiple streamers propagation from the "hot" electrode toward the grounded one. In case of highpower electrical source those streamers occupy a huge volume of the gas, covering all possible paths for the further development. The next phase consists of the real selection of the discharge path among the multiple channels with nonzero conductivity. It is the key point which channel appears to be the best in terms of the current increase, i.e. possessing higher conductivity and lower inductivity. In non-uniform media the favorite path may not be the shortest one. The second effect appears in fast turbulent expansion of the postdischarge. The mechanism of phenomena is in development of fast gas cumulative jets escaping from the disturbed zone after strong shock wave pa- sage. For the effect realization the shock wave must be curved due to initial multiple bends of the discharge channel. In the paper the experimental data are supported by theoretical and computational analyses.