Jet-guided combustion characteristics and local fuel concentration measurements in a hydrogen direct-injection spark-ignition engine

Spark-ignition (SI) hydrogen engines based on direct injection (DI) promise significant advantages in terms of thermal efficiency and power output, and present a means of overcoming problems related to knocking, backfiring, and preignition. A better understanding of the effects of hydrogen jets on the fuel concentration distribution and mixing process in a DISI engine should provide new and useful insights into combustion optimization. The objective of the present work was to gain a deeper comprehension of the characteristics of late-injection hydrogen combustion. An experimental combustion setup was applied to a fired, jet-guided DISI engine operated at 600 rpm in stratified mode. GDI injector with the jet directed toward the spark plug was used to develop the stratified combustion concept. A high-speed camera synchronized with the spark was focused on a 52 mm-diameter field of view through a window at the bottom of the piston crown. A series of single-shot images captured at different intervals was used to study the time evolution of the flame distribution. Variations in the fuel injection timing relative ignition timing were found to impact the development of the early flame, as well as the flame propagation. This research also employed spark-induced breakdown spectroscopy (SIBS) to measure the local fuel-air concentration in the spark gap at the time of ignition under stratified-charge conditions. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.