A synthesis of the research undertaken at the Institut Francais
du Pétrole to understand phenomena of combustion, of heat
transfers, and of knock and controlling to optimize
high-compression-ratio combustion chambers has led to the proposing
of two specific research topics: - calm chamber with dual ignition;
turbulent chamber with squish effect.
A calm chamber with a small surface-area/volume ratio enables
heat losses to be minimized because they penalize operating
efficiency all the more as the compression ratio is high. Dual
ignition combined with a geometry which maximizes the area of the
flame front creates high energy discharge release rates which are
favorable for efficiency and knock prevention. The main limitation
of dual ignition is the technico-economic constraint.
Optimizing squish chambers requires a geometric design which
makes a compromise on sufficiently high turbulence intensity to
speed up combustion without overly increasing heat transfers.
The geometry must also enhance the development of a maximum-area
flame front, and the squish effect must amplify this area even
further. Building such a chamber depends on knowing the internal
aerodynamics, the interactions between the geometry and the overall
movement of gases, and the turbulence.