Cummins tried out the EPA favored technique of very heavy EGR to meet the extreme NOx regulations.
That did not work out very well.
I followed Caterpillar as they tried
(with partial USA gov funding)
in the 1980s to make a Cat diesel run on very finely ground up low ash coal.
That did not work out.
The British Navy tried in the 1920s to make torpedos with “no foamy wake bubbles of CO2 gas” using fuel with enriched oxygen.
At that time England considered Japan a friendly ally, and allowed them to see their technology,
https://en.wikipedia.org/wiki/61_cm_Type_90_torpedoJapan improved this type torpedo to what they called the Type 93, which had no visible wake, twice the range, and a very large warhead.
The English later called these “Long Lance” torpedos.
https://en.wikipedia.org/wiki/Type_93_torpedoUnfortunately, if an attacking airplane hit the Type 93 oxygen tank with as little as a single bullet,
a raging fire could result that would cause the large torpedo warhead to explode and sink the Japanese warship.
After a couple years of use Type 93 torpedos on ship explosions had sunk a few Japanese Destroyers and Cruisers.
Japanese ship captains began to defensively fire off their Type 93 torpedos at the first sighting of an attack by diving enemy aircraft.
