2-stroke diesel is the (near) future?

"Steve" wrote

In practical terms, no one really
wants or needs a 9000 RPM diesel, though.

Oh, I don't know. NASCAR might be interested in going diesel ! g
--
Jim in NC

Steve wrote:

In almost ALL real-world engines, the actual limit is set by the point
at which some mechanical component would fail. The engine's torque *may*
drop off well before the mechanical failure point if it can't ingest
enough fuel or air at high speed. In the case of a diesel, you can
pretty much increase the burn rate to as high as the mechanical parts
can tolerate by increasing turbocharger boost (and injection rate to
match). Since detonation isn't possible (no fuel exists in the cylinder
until combustion is supposed to begin anyway) the only limits to boost
pressure are mechanical in nature. In practical terms, no one really
wants or needs a 9000 RPM diesel, though.

Actually, detonation can and does occur in Diesels. With today's Diesel
fuels and injection methods the fuel does not burn INSTANTLY upon
injection. The droplets are too large. The droplets tend to evaporate
from their surface area. It IS possible for unburned gases evaporated
from the fuel to exist in the chamber and detonate in local regions. The
effect is nowhere as severe as the detonation that occurs in spark
engines at times. Interesting traces made with high frequency pressure
sensors indicate these local "peaks" in combustion pressure when this
occurs. It is the cause of the "tinkling" sound that Diesels
occasionally make.

Detonation is not a full or nothing situation. Local regions can
undergo detonation even while the majority of the charge undergoes
normal wavefront burning, in either Diesel or SI.

There's no fundamental limit thats any different than
a gasoline engine, really, but up until now there's not been a demand
for high-RPM diesels.

Thought I had responded to this before, but cannot find it.

There IS a fundamental reason diesels do not turn as many revolutions
as a gas engine. Injecting the fuel throught most of the expansion
cycle prevents speed, but does give a constant push. You could shorten
the injection so that the end of the injection is closer to TDC, but
then it would be more of an otto cycle. If you put too much fuel at or
near TDC then you would have the same problem as an otto engine with
high compression and low octane fuel. Diesel fuel is not high octane.