I'm doing research in multifuel engines used extensively by the US Army in Vietnam. The engines are a Diesel (compression-ignition) concept that is designed to be very robust in order to burn a multitude of fuels including Diesel, jet fuel, kerosene, gasoline, burner oil, etc.
The engines were manufactured beginning in the 1950s through the 1970s by White, Hercules, and Continental (American farm tractor and aircraft engine builders). However, I've heard the U.S. did not originally develop the hypercycle combustion technology, but instead it was captured from the Nazis at the end of WWII. I've also heard the research was developed by what is today known as MAN Diesel in Germany.
This appears to be common knowledge among the military vehicle collector community, but I cannot find a source to back it. Is there any known source that can prove or disprove this myth?
The concept was not particularly new in WWII. Once Rudolf Diesel had worked out that a heat engine using internal combustion was going to be more efficient than a steam engine, in 1893, there were various fuels tried. Diesel himself seems to have used a vegetable oil. If whatever that's drawn into the cylinder can be burned, in theory it could run an internal combustion engine at least somewhat. The Japanese would use smouldering charcoal to create carbon monoxide, and use that to run cars -very slowly- during the War. Worn diesel engines can sometimes do a magic trick, where just the crankcase oil blowing past the rings can keep them running. More than one driver of an old VW or Mercedes has carried around a CO2 fire extinguisher, to get their car's engine to stop.
You might be interested in the Hot Bulb Engine which is an early multi-fuel engine, remarkably simple in that it needed no carburetor. One of these was already in use in Germany before WWII, having been developed in reaction to the fuel shortages of WWI.