In-Cylinder Charge Motion Development for Gasoline Engine 2020-01-0501
In recent years, world-wide automotive manufacturers have been continuously working in the research of suitable technical solutions to meet upcoming stringent carbon dioxide (CO2) reduction and Real Driving Emission (RDE) targets, as set by international regulatory authorities. Many technologies have been already developed, or are currently under study by automotive manufacturer for gasoline engines, to meet legislated targets.
In-line with above objective, the enhancement of turbulence intensity inside the combustion chamber has a significant importance which contributes to accelerating the burning rate, to increase the thermal efficiency and to reduce the cyclic variability. Turbulence generation is mainly achieved during the intake stroke which is strictly affected by the intake port geometry, orientation and to certain extends by combustion chamber masking. Conservation of turbulence intensity in compression stroke till firing top dead Centre (fTDC) is achieved by optimized shape of combustion chamber geometry and piston bowl shape.
In this work, different geometries of combustion chamber and especially piston bowl have been designed and analyzed by means of transient three dimensional (3D) computational fluid dynamics (CFD) simulations, to foresee the in-cylinder tumble motion development and conservation of Turbulence Kinetic Energy (TKE) during intake and compression stroke respectively. Combustion set design intends was to maximize the TKE and keeping the center of TKE at/near bore center to reduce phasing loss. This minimizes the delay in the start of combustion (SOC), promotes high flame growth-rate and excellent combustion stability with reduced cycle to cycle variation. Final designs were manufactured and tested on actual engine in test bench. Lower phasing loss and fast combustion is attained with this work.