Plasma-enhanced electrostatic precipitation of diesel exhaust using high voltage nanosecond pulse discharge

Abstract

We have demonstrated nearly 80% remediation of diesel particulates from an 18 kW (i.e., 24.4 HP) diesel engine with just 1.6% of the engine power using a transient pulsed plasma in conjunction with an applied DC bias voltage. This result was achieved using a high voltage (~10 kV) DC bias together with nanosecond high voltage pulses (~20 kV) in what we refer to as a plasma-enhanced electrostatic precipitator (PE-ESP). Here, the remediation takes place in a two-step process in which the particles are first charged by the ions in the plasma and then they are swept out to the collecting electrode by the applied DC bias. The fast rise times (i.e., dV/dt≈ 1012V/sec) associated with these nanosecond pulses produce a streamer discharge with ion densities that are more than one order of magnitude higher than conventional DC coronas. These extremely high ion densities produce the enhanced electrostatic precipitation observed here. In fact, little or no remediation was observed with the DC bias only or with the nanosecond pulses only, and it is the combination of these two applied fields (pulsed and DC) that produces the robust enhancement observed here. This general approach of using nanosecond pulse discharge to produce plasma-enhanced electrostatic precipitation opens up new degrees of freedom in the design of new and more compact ESPs.