vance wrote:

Paul wrote:

Can anybody identify this aircraft  engine?

Paul Lamar

AIRCRAFT?? Virg

Could you be a little less verbose Virg? :-)

Paul Lamar

        That sure looks like one heck of a BOAT anchor.
                Virg

Since nobody has come close yet here is a hint. It is a piston engine.

Paul Lamar

vance wrote:

If it is a piston engine it would be a "free piston" engine - really a
gas generator since shaft hp is from a seperate turbine, I remember it
proposed for marine use, but never heard of any aircraft applications
planned - Vance

Jeff Spitzer won since he got his answer in before Vance. Looks like it
took that (perhaps too generous) hint.

In the case of a free piston engine all the HP is extracted from the
exhaust and fed to a turbine. Sort of like a 100% turbo compound engine.
The turbine part was not shown in that picture. This is 1940 vintage.
I mention all this as extracting HP from the exhaust is a very good
idea and yet very few companies are pursuing this.

This one is an opposed piston two cycle diesel just like the Junker Jumo
but without rods and crankshafts. Well, perhaps not exactly alike, because
of porting differences. Jeff should know as he designed and built an opposed
piston two cycle diesel aircraft engine.

The main drawback is it never fires exactly when you want it to fire. It fires
when it feels like firing. The other characteristic is it mainly runs well
at only its natural resonant frequency. It is also hard to start but maybe
easier when computer controlled is applied.

Paul Lamar

 This engine is not utilizing the opposed piston concept in the same mode 
as Junkers, where one piston slightly leads the other to open
and close the exhaust port before the inlet port to allow true
supercharging. These pistons are opposed and in synch to balance what
otherwise would shake the engine apart. The only "free piston" concept
that that does not use opposed pistons is a combustion pile driver. Near
as I can tell this engine uses a version of
"crankcase" scavanging plus "crankcase" pumping for increased mass flow
to the turbine. This probably suffers many of the turbine engine
failings in that off point performance would be very poor, As you say,
resonance is a strong driver - how would you idle that sucker? and
throttle response? forget it. - neat conundrum, but was it really touted
as an aircraft engine?  Vance

Yes I agree on the Jumo part. That is why I said the porting was different.
This one is loop scavenged and the Jumo was linear scavenged for my
wont of a better term. Jeff knows a lot about this.

Aircraft engine? Well Pratt & Whitney built it out of aluminum :-)
Probably pretty light for a diesel engine of the same displacement.
No steel needed except of course in the turbine. Taylor has a chapter
on free piston engines if anybody is interested. 

BTW The porting in the Taylor example is more like the Jumo.

Paul Lamar
 
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