Influence of the Injection Timing on the Mixture Formation Process in a Spark-Ignition Hydrogen Fuelled ICE Politecnico di Bari

Format:

Book

Conference/Event

Author/Creator:

Anaclerio, Giuseppe, author.

Contributor:

Camporeale, Sergio

Capurso, Tommaso

Torresi, Marco

Conference Name:

16th International Conference on Engines & Vehicles (2023-09-10 : Capri, Italy)

Language:

English

Physical Description:

1 online resource cm

Place of Publication:

Warrendale, PA SAE International 2023

Summary:

In the context of reducing carbon-dioxide (CO2) emissions, the increasing exploitation of renewable sources is expected to improve the availability of green hydrogen, which can be considered a valid alternative to gasoline and diesel fuels in the mobility sector (particularly for long-haul and heavy-duty missions).The air-hydrogen mixing plays a significant role, particularly in direct-injection spark-ignition engines. As a matter of fact, the onset of zones featuring an equivalence ratio greater than 0.5 should be avoided, since this would lead to an increased risk of self-ignition and NOx production. The presence of wide ultra-lean volumes (over the lean flammability limit) due to imperfect mixing is negative too, yielding to irregular combustion. Therefore, the calibration of the direct injection timing is a crucial task.In this work, the authors numerically explore the influence of the injection timing, for a fixed total amount of fuel (global equivalence ratio equal to 0.25), on the hydrogen-air mixing process. Using the SOpHy cylinder geometry as a test engine, different combinations of the Start of Injection (SOI) and Duration of the Injection (DOI) have been tested. In particular, two early SOI, 137° and 125.5° before Top Dead Center (bTDC), have been compared to a late injection strategy (50° bTDC). Two different DOI have been tested, equal to 6° and 17°. URANS simulations have been carried out to assess the influence of the different injection timings on the uniformity index, which, based on the local equivalence ratio, describes the level of homogenization of the charge. Insights of the equivalence ratio spatial distribution at the ignition timing are provided, along with the observed differences in terms of charge motion (swirl and tumble indices) and turbulence levels, described by the trends of the mean turbulent kinetic energy inside the cylinder. Early injections have been found to realize a nearly homogeneous mixture. This has been observed to be particularly true in the DOI 6° cases, due to the higher level of the charge motion and turbulent kinetic energy induced by the jet momentum. On the other side, the SOI 50° bTDC and DOI 17.5° has been observed not to produce a suitable mixing. For the same SOI, an improvement in the mixture quality has been observed when lowering the DOI to 6°, due to the same reasons found in the early injection cases

Notes:

Vendor supplied data

Publisher Number:

2023-24-0079

Access Restriction:

Restricted for use by site license