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In recent years gasoline compression ignition (GCI) has been shown to offer an attractive combination of low criteria pollutants and high efficiency. However, enabling GCI across the full engine load map poses several challenges. At high load, the promotion of partial premixing of air and fuel is challenging due to the diminished ignition-delay characteristics at high temperatures, while under low load operations, maintaining combustion robustness is problematic due to the low reactivity of gasoline. Variable valve actuation (VVA) offers a means of addressing these challenges by providing flexibility in effective compression ratio. In this paper, the effects of VVA were studied at high loads in a prototype heavy-duty GCI engine using a gasoline research octane number (RON) 93 at a geometric compression ratio (CR) of 15.7. Both late intake valve closing (LIVC) and early intake valve closing (EIVC) strategies were analyzed as a measure to reduce the effective compression ratio.

Hydrogen internal combustion engines (H2ICE) offer a cost-effective solution to decarbonize transport by combining a lower carbon intensity fuel with mature and established internal combustion engine technology. While vehicles running with hydrogen have been demonstrated over the years, this fuel's physical and chemical properties require modifications and upgrades on the vehicle from an engine and system-level perspective. In addition, market-specific regulatory and economic factors can also constrain the realization of optimal hydrogen powertrain architectures. Therefore, this paper reviews the impact of hydrogen use on combustion, injection, air management, and after-treatment systems, indicating the different strategies used to enable effective H2ICE strategies from an efficiency, cost, and safety standpoint.