Numerical Study of Turbulence and Fuel-Air Mixing within a Scavenged Pre-Chamber Using RANS and LES

Abstract

20XX-01-XXXX Numerical study of turbulence and fuel-air mixing within a scavenged pre-chamber using RANS and LES Author, co-author (Do NOT enter this information. It will be pulled from participant tab in MyTechZone)

Numerical Simulations of Pre-Chamber Combustion in an Optically Accessible RCEM

“…The typical swirling flow of the leaner incoming mixture is visible at 2 and 3 ms, where the colder region is penetrating onto the prechamber in the near-wall region. This swirling flow pattern has been described in detail in [30]. RANS simulation results are qualitatively similar to LES, apart from the smoothness of the flame front.…”

“…LES simulations have been performed on a mesh with a homogeneous cell size within the pre-chamber and the initial 10 mm of the jets in the main chamber of 0.125 mm, and a cell size in the rest of the main chamber of 0.25 mm, leading to approximately 8 million cells at top dead center. The mesh in the pre-chamber is the same as in our previous non-reactive study reported in [30].…”

“…For RANS simulations the computational mesh size was chosen based on a grid sensitivity study and comparison with LES simulations for the mixture formation analysis in pre-chamber [30] resulting in uniform grid of Δx=0.18mm in the pre-chamber with a gradual expansion to 0.94mm in the main cylinder. No special clustering was employed in the flame jet region.…”

“…At -2.7 ms the chemical reaction becomes sufficiently strong to sustain a flame development in the centre of the pre-chamber in a downward direction, where a more reactive mixture is present as seen from Figure 7 (top row), depicting the fuel mass fraction at spark-time. For a more detailed discussion of the flow conditions and fuel concentration at spark-time for this pre-and main chamber assembly the reader is referred to [30]. At -2.4 ms (i.e.…”

“…Figure 7 illustrates exemplarily the differences between 4 independent LES realizations in terms of fuel distribution at spark time (upper row), the respective impact on the early flame development within the pre-chamber 0.5 ms after spark (centre row) and the subsequent morphology of the hot jets (drawn as temperature iso-surface) exiting the pre-chamber (lower row). Results have been obtained by perturbing the fuel injection profile into the pre-chamber while keeping the rest unvaried as explained in our previous work [30]. A certain correlation between the spatial extents of fuel distribution at spark time and the flame front location at a later stage is observable, but this is not the only influencing variable, since also the velocity vortical structure plays an important role on the flame surface displacement through convection rather than chemical reactions.…”