MAP | CALMAIL |
Combustion Modeling Lab at UC Berkeley

Current Research

Ignition by non-thermal plasma: Corona discharge


Daniel Pineda (CML)

In conjuction with Ricardo North America


Introduction

Spark plugs have been used to ignite combustible mixtures like those found in automotive engines for over a century, and the principles of the ignition by sparks (thermal plasma) have remained relatively unchanged during that time. By utilizing a Radio-Frequency (RF) controlled corona discharge generated in the combustion chamber, a larger ignition volume can be obtained, facilitating combustion in high Exhaust Gas Recirculation (EGR) engine environments and substantially reducing NOx emissions.


Application of Corona Discharge Ignition in a Boosted Direct-Injection Single Cylinder Gasoline Engine: Effects on Combustion Phasing, Fuel Consumption, and Emissions

Abstract: The downsizing of internal combustion engines to increase fuel economy leads to challenges in both obtaining ignition and stabilizing combustion at boosted intake pressures and high exhaust gas recirculation dilution conditions. The use of non-thermal plasma ignition technologies has shown promise as a means to more reliably ignite dilute charge mixtures at high pressures. Despite progress in fundamental research on this topic, both the capabilities and operation implications of emerging non-thermal plasma ignition technologies in internal combustion engine applications are not yet fully explored. In this work, we document the effects of using a corona discharge ignition system in a single cylinder gasoline direct injection research engine relative to using a traditional inductive spark ignition system under conditions associated with both naturally aspirated (8 bar BMEP) and boosted (20 bar BMEP) loads at moderate (2000 rpm) and high (4000 rpm) engine speeds. Analysis of experimental results shows that relative to optimum load-speed equivalent baseline operation, using the corona discharge ignition system improves fuel economy by (1) reducing cycle-to-cycle variability, (2) promoting more complete combustion, and (3) enabling combustion phasing advancement at high loads by extending the knock limit. Additionally, the system reduces emissions by extending the practical exhaust gas recirculation limits of stable operation.

Pmax vs CAD of PmaxScatterplot and projected histograms comparing maximum pressure with maximum pressure crank angle location for the baseline spark ignition (black) operation and corona discharge ignition (red) operation, both with an EGR rate of 16% for 2000 rpm 8 bar BMEP.

Pmax vs CAD of PmaxScatterplot and projected histograms comparing maximum pressure with maximum pressure crank angle location for the baseline spark ignition (black) operation and corona discharge ignition (red) operation, both with an EGR rate of 10% for 2000 rpm 20 bar BMEP.