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Comparison Of A Molecularly-Controlled Combustion Engine To A DISI Engine

Tim Philippe Rommelaere, Michael Klaas, Wolfgang Schröder

Chair of Fluid Mechanics and Institute of Aerodynamics, Aachen, Germany

DOI:

In addition to the increased use of electromobility, significant improvements in the efficiency of internal combustion engines (ICE) to achieve a considerable reduction of emissions is crucial to advance the transition towards a sustainable transport sector. One approach to increase the efficiency of combustion engines is active pre-chamber ignited engines (Molecularly Controlled Combustion Engines, MCC). The traditional spark ignition is replaced by a chamber that ignites a secondary fuel. The burning fuel is emitted from the pre-chamber via multiple holes, igniting the fuel air mixture in the main combustion chamber. To eject the flame jets tangentially to the pent roof, the pre-chamber protrudes into the main chamber in the center of the main chamber’s pent roof. This particular geometry of an MCCengine, however, alters the flow field inside MCC-engines. To facilitate future developments around MCC-engines and to understand the interactions of the flow field with the pre-chamber, a Stereo Particle-Image Velocimetry (SPIV) study is conducted in an optically accessible MCC-engine model. Previous velocity field data, which were acquired using a Direct Injection Spark Ignition (DISI) engine configuration at the same operating point as the MCC-engine, are compared to those of the MCC-engine. Phase-averaged velocity field data of both engines acquired during the intake stroke are compared based on their in-plane velocity fields and the in-plane vorticity. The two engine configurations show significantly different magnitudes of velocity in their combustion chamber flow field. In the MCC-engine, a downwash flow component can be attributed to flow deflection caused by the pre-chamber protruding from the engine’s pent roof. One important flow feature of ICE, the tumble vortex, is analyzed for both engine configurations. An increased absolute vorticity and a different temporal development of the tumble vorticity is noted for the MCC-engine. The tumble flap, an engine component that influences the intake flow distribution, is considered a main contributor to the difference in flow velocity and tumble vorticity.

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