Combustion system development for hydrogen fueled heavy duty internal combustion engines

Increasingly stringent CO2 emission regulations demand a reorientation of powertrain concepts in the transport sector. CO2 emissions from new vehicles put on the road must be reduced by 15 % by 2025 and by 30 % by 2030 compared to 2019 baseline. Besides increasing the efficiency of existing diesel engines, possible alternatives include the use of low-carbon (e.g. methane) or even zero-carbon fuels (e.g. hydrogen) and the partial or complete electrification of the powertrain. Hydrogen offers the possibility to be used either as a fuel for internal combustion engines or for fuel cells. Fuel cells in combination with a battery electric drive offer the greatest benefit for applications with highly transient driving cycles, e.g. city buses or urban transport of goods. If high constant power and less transient vehicle operation is required, an internal combustion engine fueled with hydrogen represents a cost-effective approach to realize zero CO2 emission long haul transport. To convert a conventional diesel heavy duty engine to hydrogen operation, key components such as thecombustion system, the turbocharging system, the injection and ignition systems, and the exhaust gas aftertreatment system must be redesigned. New software structures for powertrain control are also required. To this end, this paper considers the design of the combustion system regarding piston shape(compression ratio), intake valve timing, charge motion intensity and engine raw emissions. For this purpose, a detailed kinetic reaction based combustion simulation is used to determine the most beneficial layout to achieve high specific power in combination with best engine efficiency and lowest nitrogen oxide raw emissions.