Analysis of dual fuel Hydrogen/Diesel combustion in ultra lean conditions via simultaneous UV and IR imaging

Due to their reliability, high-performance characteristics, and potential for technological innovation, combustion engines powered by alternative fuels such as hydrogen can still represent a useful solution for achieving mobility with net zero emissions. The use of hydrogen in a dual-fuel engine with diesel (or other renewable and sustainable fuels) can reduce greenhouse gas emissions as well as particulate matter emissions while ensuring excellent performance. In this scenario, tests have been carried out on a dual-fuel single-cylinder research engine to analyse the combustion evolution of H2 in ultra-lean conditions via optical diagnostics. Under ultra-lean conditions (λ = 3.8), hydrogen does not autoignite at the desired crank angle; thus, diesel has been used to ignite the hydrogen premixed charge. An operating point at 1500 rpm engine speed and at fixed load has been investigated. The in-cylinder pressure and related data have been analysed as indicators of combustion quality. 2D-digital cycle-resolved imaging has been performed in both ultraviolet (UV) and infrared (IR) wavelength ranges. Qualitative information about the development of diesel hydrogen dual fuel combustion has been gained. UV and IR cameras simultaneously acquired images of the diesel and hydrogen combustion and provided information on the flame onset and its development via the detection of OH* and low- and high-temperature reaction zones within the bowl, respectively. Results show that to efficiently control hydrogen combustion, it is necessary to properly phase the start of diesel combustion.