Radical Controlled Autoignition at Reduced Compression Ratios in a Hydrogen D.I. Diesel Engine With Piston Micro-Chambers

This four-stroke engine study examines how micro-chamber generated “radicals” can facilitate the robust control of autoignition in direct-injection (D.I.) diesel engines. These internally produced radicals enable combustion under much lower than normal diesel compression ratios (CR's) and temperatures and make the chemical-kinetics control of autoignition timing a reality. In an attempt to better understand the mechanisms enabling radical based chemical control, the altered chemistry of radical ignition is studied numerically for the case of H₂ combustion. Numerical simulation is based on a detailed mechanism involving as many as 19 species and 58 reactions. This H₂ chemical-kinetics mechanism is simultaneously solved within two separate but connected open systems representing the distinctive main-chamber and micro-chamber processes (Figure 1). During the combustion cycle these two open systems continuously interact, passing energy and chemical species between one another and the atmosphere while attempting to equalize pressure differences.