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The spray development of ethanol, gasoline and iso-octane has been studied in an optically accessible, spark-ignition direct-injection (SIDI) engine. The focus is on how fuel properties impact temporal and spatial evolution of sprays at realistic ambient conditions. Two optical facilities were used: (1) a constant-flow spray chamber simulating cold-start conditions and (2) a single-cylinder SIDI engine running at normal, warmed-up operating conditions. In these optical facilities, high-speed Mie-scattering imaging is performed to measure penetrations of spray plumes at various injection pressures of 4, 7, 11 and 15 MPa. The results show that the effect of fuel type on the tip penetration length of the sprays depends on the injection conditions and the level of fuel jet atomisation and droplet breakup.

A hydrogen-diesel dual direct injection (H2DDI) combustion strategy in a compression-ignition engine is investigated numerically, reproducing the configuration of previous experimental investigations. These experiments demonstrated the potential of up to 50% diesel substitution by hydrogen while maintaining high engine efficiency; nevertheless, the emission of NOx increased compared with diesel operation and was strongly dependent on the hydrogen injection timing. This implies the efficiency and NOx emission are closely associated with hydrogen charge stratification; however, the underlying mechanisms are not fully understood. Aiming to highlight the hydrogen injection-timing influence on hydrogen/air mixture stratification and engine performance, the present study numerically investigates the mixture formation and combustion process in the H2DDI engine concept using Converge, a three-dimensional fluid dynamics simulation code.

The combustion process of a homogeneous hydrogen charge in a small-bore compression ignition engine with diesel-pilot ignition was simulated using the CONVERGE computational fluid dynamics code. Analysis of the simulation results aimed to understand the processes leading to NOx production and heat loss in this combustion strategy, and their dependence on the hydrogen fuel energy fraction. Previous experimental results demonstrated promising performance, but this comes with a penalty in increased NOx emissions and potentially higher heat losses. The present study aims to enhance understanding of the mechanisms governing these phenomena. The simulated engine was initialised with a lean homogeneous hydrogen-air mixture at BDC and n-dodecane was injected as a diesel surrogate fuel near TDC. The simulations were validated based on experimental results for up to 50% hydrogen energy fraction, followed by an exploratory study with variation of the energy fraction from 0% to 90%.

This study aims to clarify the spray development of ethanol, gasoline and iso-octane fuel, delivered by a multi-hole injector and spark-ignition direct-injection (SIDI) fuelling system. The focus is on how fuel properties impact temporal and spatial evolution of sprays at realistic ambient conditions. Two optical facilities were used: (1) a constant-flow spray chamber simulating cold-start conditions and (2) a single-cylinder SIDI engine running at normal, warmed-up operating conditions. In these optical facilities, high-speed Mie-scattering imaging is performed to measure penetrations of spray plumes at various injection pressures of 4, 7, 11 and 15 MPa. The results show that the effect of fuel type on the tip penetration length of the sprays depends on the injection conditions and the level of fuel jet atomisation and droplet breakup.