Optical Diagnostics to Study Hydrogen/Diesel Combustion with EGR in a Single Cylinder Research Engine

In order to reduce fuel consumption and polluting emissions from engines, alternative fuels such as hydrogen could play an important role towards carbon neutrality. Moreover, dual-fuel (DF) technology has the potential to offer significant improvements in carbon dioxide emissions for transportation and energy sectors. The dual fuel concept (natural gas/diesel or hydrogen/diesel) represents a possible solution to reduce emissions from diesel engines by using low-carbon or carbonfree gaseous fuels as an alternative fuel. Moreover, DF combustion is a possible retrofit solution to current diesel engines by installing a PFI injector in the intake manifold while diesel is injected directly into the cylinder to ignite the premixed mixture. In the present study, dual fuel operation has been investigated in a single cylinder research engine. The engine run at two engine speeds (1500 and 2000 rpm), and hydrogen has been injected in the intake manifold in front of the entrance of the tumble intake port. The aim of the study is to compare the DF hydrogen combustion with the DF methane combustion with the use of exhaust gas recirculation gases. Premixed ratio up to 92% and 83% has been realized with methane and hydrogen, respectively. In-cylinder combustion pressures and pollutant emissions have been analyzed. Finally, cycle resolved optical diagnostics have been applied to detect visible and infrared images from the combustion chamber. IR intensities have been recorded and compared with the rate of heat release curves showing a good agreement. This information is of interest for CFD analysis of ultra-lean hydrogen combustion.