Numerical Investigation on Mixture Formation and Combustion Process of Innovative Piston Bowl Geometries in a Swirl-Supported Light-Duty Diesel Engine
Journal Article
03-14-02-0015
ISSN: 1946-3936, e-ISSN: 1946-3944
Sector:
Topic:
Citation:
Millo, F., Piano, A., Roggio, S., Bianco, A. et al., "Numerical Investigation on Mixture Formation and Combustion Process of Innovative Piston Bowl Geometries in a Swirl-Supported Light-Duty Diesel Engine," SAE Int. J. Engines 14(2):247-262, 2021, https://doi.org/10.4271/03-14-02-0015.
Language:
English
Abstract:
In recent years, several innovative diesel combustion systems were developed and
optimized in order to enhance the air and injected fuel mixing for engine
efficiency improvements and to mitigate the formation of fuel-rich regions for
soot emissions reduction. With these aims, a three-dimensional computational
fluid dynamics (3D-CFD) numerical study was carried out in order to evaluate the
impact of three different piston bowl geometries on a passenger car
four-cylinder diesel engine, 1.6 liters. Once the numerical model was validated
considering the baseline re-entrant bowl, two innovative bowl geometries were
defined: one based on the stepped-lip bowl; the other including a number of
radial bumps equal to the nozzle holes number. Firstly, the rated power engine
operating condition was investigated under nonreacting conditions to evaluate
the piston bowl effects on the in-cylinder mixing. Results highlight for both
the innovative piston bowls better air utilization with respect to the
re-entrant bowl: the stepped-lip bowl creates a dual toroidal vortex leading to
a higher air/fuel mixing, while the radial-bumps bowl significantly affects the
jet-to-jet interaction and promotes the recirculation of the fuel jet downstream
to the bump, where the available oxygen enhances the mixing rate. After that,
the combustion analysis was carried out for both rated power and partial-load
engine operating conditions. Results confirmed that thanks to the better
air-fuel mixing, the combustion process can be improved thanks to the innovative
bowl designs, both increasing the engine efficiency at full-load condition and
minimizing the engine-out soot emissions at partial-load operating point.