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The exponential rise in greenhouse gas (GHG) emissions into the environment is one of the major concerns of international organisations and governments. As a result, lowering carbon dioxide (CO2) and methane (CH4) emissions has become a priority across a wide range of industries, including transportation sector, which is recognised as one of the major sources of these emissions. Therefore, renewable energy carriers and powertrain technologies, such as the use of alternative fuels and combustion modes in internal combustion engines, are required. Dual-fuel operation with high substitution ratios using low carbon and more sustainable fuels can be an effective short-term solution. Hythane, a blend of 20% hydrogen and 80% methane, could be a potential solution to this problem.

Low combustion efficiency and high hydrocarbon emissions at low loads are key issues of natural gas and diesel (NG-diesel) dual fuel engines. For better engine performance, two diesel-spray-orientated (DSO) bowls were developed based on the existing diesel injector of a heavy-duty diesel engine with the purpose of placing more combustible natural gas/air mixture around the diesel spray jets. A protrusion-ring was designed at the rim of the piston bowl to enhance the in-cylinder flame propagation. Numerical simulations were conducted for a whole engine cycle at engine speed of 1200 r/min and indicated mean effective pressure (IMEP) of 0.6 MPa. Extended coherent flame model 3 zones (ECFM-3Z) combustion model with built-in soot emissions model was employed. Simulation results of the original piston bowl agreed well with the experimental data, including in-cylinder pressure and heat released rate (HRR), as well as soot and methane emissions.