Experimental Analysis of Breakdown With Nanosecond Pulses for Spark-Ignition Engines

Abstract

The influence of pulse rise rate and pulse duration for ignition purposes in engines is investigated. A constant volume cell is used to characterize the breakdown voltage under nanosecond pulsed voltages with automotive sparkplugs having electrode gaps ranging from 0.2 mm to 1 mm. Two pulse generators are used to compare pulses with durations of 10 ns and 50 ns. Different pulse amplitudes are used, and air gaps with breakdown voltages ranging from 4 kV to 15 kV are investigated. The cell is filled with synthetic air with densities gap distances products that are relevant for internal combustion engines. This study shows that the pulse shape and rise rate influence the breakdown voltage. Under pulsed discharge, the breakdown voltage is always above the static breakdown voltage. The probability of pulsed discharge breakdown increases as both the pulse amplitude and duration increases. Furthermore, the breakdown voltage value increases with increasing pulse rise rate. The delay time between reaching the static breakdown voltage and the actual breakdown voltage decreases with increasing overvoltage. The delay time is constituted by statistical and formative times. Both the statistical and formative times decrease with increasing overvoltage. For ignition purposes, the pulse rise rate should be as high as possible to deliver a larger energy input in the breakdown phase. Furthermore, for reduced electrode erosion, the pulse duration should be short (10-20 ns) to reduce the probability for a transition to an arc.

Breakdown of Synthetic Air Under Nanosecond Pulsed Voltages in Quasi-Uniform Electric Fields

“…Conversely, at high maximal impulse factors, the breakdown voltage scatters significantly, whereas the time falls in a relatively narrow interval. Similar breakdown regimes are reported in [11]; where, due to the complex geometry involved, the calculation of the active area was not possible. This behavior can be related to the employed voltage pulse shape.…”

“…For this reason, a shielded current monitor (Pearson current monitor model 6585 with a usable rise time of 1.5 ns) is placed in the middle of the coaxial cable, where the shield of the cable is removed and reconstructed around the current monitor. The details and validation of the measurement technique are reported in [11].…”

“…Positive polarity pulses are used in this investigation; therefore, the HV electrode is positive (anode), while the ground electrode is negative (cathode). A more detailed description of the system's setup, and electrical characterization can be found in [11].…”

“…Computational fluid dynamic modeling of ignition from a nanosecond pulsed discharge was reported in [9], and a description of the energy delivered during the discharge was reported in [10]; nevertheless, the characterization and modeling of breakdown thresholds (e.g., probability of breakdown occurring for a pulse of given amplitude, rise time, and duration) and the distribution of delay times are lacking. The influence of the nanosecond pulse rise rate on the breakdown voltage and breakdown time was investigated in [11]. Two pulse durations of 50 and 10 ns were used, and streamer theory was identified as the breakdown onset mechanism.…”

The Nanosecond Impulsive Breakdown Characteristics of Air, N2 and CO2 in a Sub-mm Gap

“…In [11], the breakdown properties of CO 2 and CO 2 -O 2 mixtures were investigated under different energization regimes, for prospective power industry applications (for example gas-filled circuit breakers); and in [12], the breakdown properties of air stressed with ns impulses have been studied to provide further quantitative information on the plasma kinetics of air. Other advanced applications that require detailed information on the breakdown of gases in short gaps include plasma-assisted ignition and combustion [13,14]; plasma thrusters for miniature flying robots [15]; environmental and medical applications [16,17]; and the fabrication of nanomaterials [18].…”