Advanced Ignition System for Internal Combustion Engines Enabling Lean-Burn and Dilute Gasoline Ignition

The Department of Energy is interested in reducing Americas petroleum consumption to provide greater freedom of mobility, energy security, lower costs and reduced impact on the environment. Dilute-burn gasoline engines are considered one of the most attractive solutions to developing more energy efficient and environmentally friendly highway vehicles; however, ignition instability associated with dilute mixtures prevents wide-spread application1. For this grant, a novel low-energy and cost effective nanosecond pulsed ignition system based on technology that has been shown to reliably ignite dilute mixtures2 while reducing electrode wear will be developed from TRL5 to TRL6, enabling a significant leap in the performance of next generation of fuel efficient vehicles. In dilute-burn gasoline engines, dilution with air or with exhaust gas recirculation allows for improved fuel efficiency and reduced emissions by limiting thermal losses, but it also reduces the engines peak power. This lost power can be recovered through turbocharging, but the combination of dilution and intake pressure boost makes ignition increasingly difficult. Traditional ignition methods can ignite this mixture if the ignition energy is significantly increased, but this causes unacceptable electrode wear. Low-energy nanosecond pulses enable stable dilute-burn ignition without accelerated ignition system fatigue. Low-energy nanosecond pulses will be used to produce a non-thermal plasma, which uses less power and is much more effective compared with the thermal or quasi-thermal plasmas that are commonly generated by alternative advanced ignition techniques3. Traditional thermal ignition systems heat a zone of combustible mixture to a temperature where radicals are thermally generated and produce rapid chemical reactions that generate heat faster than heat transfer can cool the zone, resulting in ignition. This technique, used for over 100 years, has limitations in dilute mixtures because thermally generating radicals is inefficient and slow and excess air in lean mixtures cools the ignition zone more quickly. In non-thermal plasma radicals are produced directly, which is more than 50 times more efficient4, and therefore less energy is needed to generate heat more quickly and the mixture can be leaner.
During Phase I, a production intent design of a low-energy nanosecond pulsed ignition system for enabling stable dilute ignition will be developed and tested in a single-cylinder gasoline direct injected engine to measure the effectiveness under dilute and high-pressure conditions. For Phase II, existing relationships with engine testing facilities and original equipment manufacturers will allow quick access to expertise and experience with engine experts to optimize the system. Early versions of the technology have been demonstrated in engine applications in multiple labs, including Sandia National Labs Combustion Research facility2 and Argonne National Lab5. The technology can be applied to all spark-ignition engines and is fuel agnostic, enabling increased fuel efficiency and reduced emissions in gasoline, natural gas, ethanol, hydrogen, propane, and methanol cars, trucks, and generators.