Combustion engine piston and engine using same

A reciprocating internal combustion engine, comprising:

• a piston disposed within an engine cylinder, the piston including
• a crown including at least one cylindrical surface, the at least one cylindrical surface being centered on a longitudinal axis of the piston, a diameter of the at least one cylindrical surface defining an outer diameter of the piston;
• and
• an upper surface configured to at least partly face a cylinder head of the reciprocating internal combustion engine, the upper surface including
• a combustion bowl surface, and
• a squish face having an internal edge disposed a first distance from the longitudinal axis along a radial direction, the radial direction being normal to the longitudinal axis,
• the combustion bowl surface including
• a planar surface extending radially outward from the longitudinal axis of the piston,
• a first concave surface disposed outside the planar surface in the radial direction, the first concave surface having a first radius of curvature,
• a second concave surface disposed outside the first concave surface in the radial direction, the second concave surface having a second radius of curvature, the second radius of curvature being smaller than the first radius of curvature, wherein a compression ratio of the reciprocating internal combustion engine ranges from about 9.5:1 to about 10.5:1, wherein a radially innermost edge of the second concave surface abuts a radially outermost edge of the first concave surface, such that a radial slope of the second concave surface at the radially innermost edge of the second concave surface is equal to a radial slope of the first concave surface at the radially outermost edge of the first concave surface, and
• a frustoconical surface disposed between the second concave surface and the squish face, the frustoconical surface facing the longitudinal axis, a diameter of the frustoconical surface decreasing along a direction of the longitudinal axis extending away from the planar surface toward the squish face, and the frustoconical surface is a surface of revolution centered substantially on the longitudinal axis, and the frustoconical surface defines an angle with respect to the longitudinal axis between about 5 degrees and about 15 degrees, the frustoconical surface being free from convex curvature.