A question about aero diesel engine in WWII

[swampyankee]

For worries about gelling, using jet fuel would be the way to go for an aircraft diesel engine.

Except they didn't have jet fuel during WW2; Jet-A and Jet-B weren't developed until the 1950s. Jet-A (sensible people don't use Jet-B except in polar regions) also has different lubricating properties than diesel fuel, requiring different fuel handling pumps.

 

[Piper106]

Some thoughts.

Other than Junkers, and Bristol, most of the 1930s diesel aircraft engine developers seemed to be 'shoe string' outfits that would not have been able to produce more than a handful of engines even if they had been able to over come the design development problems.

Junkers had a 'leg up' in aircraft diesels since Hugo Junkers had a special interest in diesel engines. I did not seem that any of the other big engine manufacturers had a diesel 'advocate'.

By 1938 or 1939 even the most promising diesel projects had to take a side track to more certain to succeed gas engines needed for the coming war.

It is unfortunate that there were not any air cooled radial diesel aircraft engines in the 1600 to 2500 HP class available for WWII.. Ground attack / CAS aircraft would have seemed an obvious fit. Diesel fuel with its lower risk of fire would have saved many aircrew members and aircraft. NACA was working on a sleeve valve two cycle diesel cylinder test in the late 1930s. Imagine a diesel Hercules / Centaurus powered AD Skyraider.

 

[Shortround6]

Imagine a diesel Hercules / Centaurus powered AD Skyraider.

I can't get the image out of my brain with a spork

Part of what killed the Diesel was that every time it got close to the gasoline engine in power to weight ratio the fuel guys managed to come up with higher octane/performance gasoline which moved the bar. My opinion is that once gasoline went into the 90 octane range and higher there was little the diesel could do to compete.
For the Skyraider the diesel would have either offered hundreds of HP less or weighed hundreds of pounds more than the R-3350s that went into it. Neither situation would have been satasfacory.

 

[swampyankee]

One interesting datum is that many of the aero diesels of the era (I think the Jumo 205/206 were an exception) were pre-chamber engines, and had sfcs not much different than contemporary spark engines. Of course, diesel fuel is somewhat denser than gasoline, and is less susceptible to bursting into flame when bullets are shot through it.

 

[Shortround6]

The Man who edited "Aircraft Engines of the World" (Paul H. Wilkinson) though many editions was a diesel fan. He did do several books just on diesels, one in 1936 and one in 1940. I believe the last one is available on the internet.

Here http://www.enginehistory.org/Piston/Diesels/diesels.shtml