3D CFD simulation of a gaseous fuel injection in a hydrogen-fueled internal combustion engine

Abstract

Nowadays, one of the hottest topic in the automotive engineering community is the reduction of fossil fuels. Hydrogen is an alternative energy source that is already providing clean, renewable, and efficient power being used in fuel cells. Despite being developed since a few decades, fuel cells are affected by several hurdles, the most impacting one being their cost per unit power. While waiting for their cost reduction and mass-market penetration, hydrogen-fueled internal combustion engines (H2ICEs) can be a rapidly applicable solution to reduce pollution caused by the combustion of fossil fuels. Such engines benefit from the advanced technology of modern internal combustion engines (ICEs) and the advantages related to hydrogen combustion, although some modifications are needed for conventional liquid-fueled engines to run on hydrogen. The gaseous injection of hydrogen directly into the combustion chamber is a challenge both for the designers and for the injection system suppliers. To reduce uncertainties, time, and development cost, computational fluid dynamics (CFD) tools appear extremely useful, since they can accurately predict mixture formation and combustion before the expensive production/testing phase. The high-pressure gaseous injection which takes place in Direct-Injected H2ICEs promotes a super-sonic flow with very high gradients in the zone between the bulk of the injected hydrogen and the flow already inside the combustion chamber. To develop a methodology for an accurate simulation of these phenomena, the SoPHy Engine of the Engine Combustion Network group (ECN) is used and presented. This engine is fed through a single nozzle H2-injector; planar laser-induced fluorescence (PLIF) data are available for comparison with the CFD outcomes.

3D CFD analysis of Mixture Formation in Direct-Injection Hydrogen-fueled Internal Combustion Engines

“…Schlieren measurements confirmed that improvements in the agreement between numerical and experimental results can be achieved with an extended duration of the injection ramp during the earlier transient stage of the injection. The lower fuel concentrations observed in the simulations might be therefore, due to the anticipated reduction of the injected mass, as portrayed by Barbato in [14]. On the other hand, these authors suggest that, for early injection, the transient duration only marginally affects the mixture formation process occurring during the rest of the compression stroke.…”

“…Given the H2 mass flow rate profile experimentally determined (see Figure 3) and the injection surface area, the hydrogen mass-flow rate through the stable injection has been calculated and set equal to 2.381 g/s in order to achieve the target of 4.365 mg of hydrogen injected per-cycle. Previous numerical activities performed on the Sandia engine case studies have executed timestepsensitivity analysis resulting in a negligible impact over the overall computational solution on mixture formation [14]. Therefore, for the current activity a time discretization of 0.5°CA and 0.1°CA had been employed respectively for the gas exchange and for the injection simulations.…”