ABSTRACT
Restrictive future CO2 emission regulations are incentivizing evaluation of carbon-free fuels. This is particularly true in the difficult to electrify heavy commercial vehicle segment. The reemergence of hydrogen internal combustion (H2 ICE) for large displacement engines can both expedite hydrogen adoption and reduce total cost of ownership. This paper will cover how the application of a Driven-Turbo can address challenges unique to H2 ICE. The research being presented is joint simulation conducted by AVL List GmbH and SuperTurbo Technologies on a 13L H2 ICE. The GT Power model is calibrated from dyno testing at AVL of an operational engine and then modified with known and tested data from a mechanically variable Driven-Turbo. The first H2 ICE challenge that will be addressed is the requirement for the engine to maintain a lean-burn combustion strategy. Maintaining H2 lean-burn is key to controlling NOx formation and minimizing aftertreatment requirements. The high lambda requirement can create challenges for turbocharges when available turbine power is insufficient for the desired compressor power. The on-demand air functionality of the Driven-Turbo negates this problem and can be used to optimize air-fuel ratio in steady-state and transient cycles. The simulation will show low NOx formation through combustion optimization and time to torque transients equivalent to diesel. The second H2 ICE challenge that will be addressed is how to maintain highest BMEP and BTE for hydrogen internal combustion engines with a Driven-Turbo in order to close the gap to diesel and FCEV respectively. The availability of Driven-Turbo enabled exhaust energy recovery through turbo-compounding, in combination with combustion optimization, will demonstrate an ability to improve H2 ICE BMEP/BTE/BSFC. SuperTurbo and AVL have completed full WHTC cycle comparisons for the mechanically Driven-Turbo versus both VGT and Two-Stage Turbo configurations, and those results will be highlighted. The WHTC cycle results will show the compromises between engine response (total cycle work) versus engine-out NOx (both peak transient NOx and accumulated cycle NOx). The Driven-Turbo is showing the potential to eliminate NOx peaks and reach Euro6 compliance levels without aftertreatment. The engine being evaluated through the WHTC is port injected with no EGR, and applicability to other engine configurations will be discussed. Physical engine testing to validate all of these findings is upcoming. Inclusion of the dyno test results will be made available via this paper and/or conference presentation, depending on test completion and material submission deadlines.
