Experimental measurement of dynamometer homologation cycles in a dual-fuel medium-duty engine

Dual-fuel engines employing alternative combustion concepts have shown promising results in meeting significant emission reductions while maintaining engine performance. In the medium and heavy-duty transport sectors, where electrification remains challenging, developing low-temperature combustion is still a technological solution for reducing carbon impact. However, most of the results in this research field have been presented under stationary conditions, which still positions the transient operation as a challenge. One of the main reasons has been the lack of a dedicated control system to manage the load transitions and the inoperability of stock turbochargers to satisfy the EGR dilution ratios and boost pressure to sustain dual-fuel combustion. This study employs a modified 7.7 L dual-fuel engine for its operation in transient conditions by incorporating a prototype turbocharger system. The study addresses the recalibration of the engine to introduce modifications to the injection and air management strategies, allowing for a smoother transition between fully premixed and diffusive combustion modes while maintaining low emissions and similar performance. The study identified the transition from 50% to 75% as the most challenging transition from moving from a fully premixed zone with pressure gradients near the physical limits to a more diffusive combustion region in the engine map. After refining the calibration to allow smooth transitions between loads, transient cycle performance under the World Harmonized Stationary Cycle (WHSC) is experimentally measured, progressively increasing load from 50% to 100%. The results under transient tests confirmed that the recalibration successfully enables full-load operation while mitigating combustion instability and excessive emissions. This research advances the understanding of dual-fuel combustion strategies and highlights the potential of dual-fuel engines as a technological solution for its implementation under real-world vehicle applications in the freight transport sector.