Abstract
It is reported that igniting rich fuel plume during or just after the completion of fuel injection period that is selected in close to TDC is effective way to reduce NOx formation by minimizing trade-offs of decrease in thermal efficiency under high load operating conditions in direct injection hydrogen engines. In this study, targeting to evaluate potentiality of improvement in thermal efficiency without considering an increase in NOx formation advanced injection timing from above mentioned was evaluated. As a result optimized elongation time from end of injection to ignition was found to improve thermal efficiency drastically. The effects were understood to be caused by increasing entrained air to the hydrogen jet plume and promote mixing of hydrogen and air. Geometry of injected plume jet which reasonably disperse fuel in combustion chamber was also found to be effective to improve thermal efficiency by reducing cooling loses to the combustion chamber wall.
