One of the problems with internal combustion engines is that it’s hard to get the fuel/air mixture in a cylinder to burn evenly.
In spark ignition systems, the ignition is finely timed but very localised. In a compression ignition (eg diesel) system, it’s harder to control the spatial/temporal distribution of the burn, although it does tend to be a more gradual process (which avoids ‘knock).
Today’s invention is to add a tiny amount of extra friction to the relative motion of piston and cylinder.
Using strips of eg carbon steel on the piston as shown (green), and a cup-shaped piston crown, will generate a gradually increasing shower of tiny sparks as the piston rises on the compression stroke.
This allows a more gradual and spatially-spread burn, but also makes that repeatable from cycle to cycle.
The friction strips could be made easily changeable every few thousand miles or they could continuously be fed along the interior cylinder wall (red).