Mechanism of Luminescence and Electrification of Liquids Flowing Through Narrow Channels

The blue-violet luminescence is revealed in the mineral oil while it is pumped through a narrow channel at the inlet pressure more than 2 MPa, and also the appearance of electric pulses is detected in the dielectric liquid flowing through a narrow passage orifice well in advance of the luminescence occurrence. A device is developed which allows the electric potential to be scanned continuously along an axis of the flow without disturbing it. It is revealed that the electric signal is a high-frequency one, it can not be synchronized, and individual pulses may have amplitudes of 1000 mV and more. As the liquid temperature rises up to 30... 35 °C or as the head pressure increases, the luminous radiation flow decreases. The hysteresis in the luminous radiation process is detected with the hydrodynamic luminescence. A mechanism of the observed phenomena is suggested on the basis of the significant role of electrokinetic processes; equations for charging and conduction currents are obtained; the stationary electric charge; potential, and field strength on the internal surface of a passage orifice are calculated. It is shown that Electric charge arises not only under the hydrodynamic cavitation but also during an operation of a laminar throttle in the absence of cavitation in the liquid; this case may be referred to the electrokinetic mechanism too. It is shown that electric charges appear not only in plastic throttles but in metallic ones as well.