Effect of hydrogen and methane in dual fuel mode in light diesel engine by VIS and IR imaging

Energy transition strongly leads researcher to find short-term alternative carbon-free fuels to be used in internal combustion engines. An interesting and transient solution can be the dual fuel (DF) technology. It can offer significant reduction of carbon dioxide and pollutant emissions. In this paper, DF operation was performed in an optically accessed research diesel engine running at a constant speed of 1500 rpm. Substitute fuels (methane or hydrogen) were injected in the intake manifold in front of the entrance of the tumble intake port. The objective was to compare the two DF modes using simultaneously Fast UV–Visible and Fast Infrared (IR) Imaging. We observed that IR camera was able to give deeper combustion information and allowed to grab the whole phenomenon for both DF hydrogen and methane, while identifying the combustion starting points. Also, IR acquisitions for premixed hydrogen evidenced an unpredictably behaviour of the mixture, demonstrating the necessity of a specific Diesel injection strategy to avoid hydrogen auto-ignition at higher engine load. Finally, a comparison of the measured emissions at the exhaust evidenced that in DF mode (both with CH4 and H2) a significant reduction of particulate matter is achieved with respect to conventional diesel operation. In addition, when hydrogen is used as primary fuel, a more efficient combustion is obtained drastically reducing HC and CO2.