Plasma-Assisted Pre-Chamber Ignition System for Highly Dilute Stoichiometric Heavy-Duty Natural Gas Engines

Project summary:

The project team plans to develop and demonstrate an advanced plasma-assisted pre-chamber ignition system for heavy-duty stoichiometric natural gas engines operating at ultra-high dilution conditions. This technology is capable of a step reduction in greenhouse gas emissions and could transform the natural gas engine market by overcoming several key barriers to wider adoption of natural gas: 1) superior engine efficiency compared to contemporary diesel engines, and 2) prolonged service intervals due to the long igniter lifetime and reduced demands for exhaust aftertreatment associated with stoichiometric operation.

This transformative ignition system combines two existing technologies--plasma-assisted igniters and pre-chamber combustion--to overcome the barriers of each single technology alone. Barriers include cyclic variability, pre-chamber spark plug lifetime, and combustion speed to extend the dilution limits for superior efficiency and extended igniter lifetime. The igniter system will be iteratively improved by successive testing relying on visualization in an optically accessible pre-chamber and optical engine to develop the science-based understanding of governing mechanisms, followed by optimization using computational fluid dynamics of plasma and combustion and optical single-cylinder engine experiments, and concluding with full-scale testing in a 6-cylinder heavy-duty engine at relevant operating points. The final project goal is to demonstrate the proposed technology in a full 6-cylinder heavy-duty engine with the goals of reaching peak brake thermal efficiency of 48 percent at more than 40 percent exhaust gas recirculation and <0.027g/kWh nitric oxide emission using three-way catalysts.