Letters
from our readers about Sleeve Valve Engines.
These
are letters from our readers about Sleeve Valve Engines in aircraft.
I've looked at some web sites about
sleeve valve engines, but after reading about them, I couldn't really understand
how they worked. Here's some letters that talk about sleeve valve
engines and their advantages. They sound like they work so well that
I can't understand why we don't see them in the aircraft today. If
you have any info, please send it to me and I will past it on this page.
6-15-02 Ralph Lindsay The straight in and out air-flow through
the s/v engine is responsible for a portion of the [apparent] improved
efficiency over the conventional poppet valve ohv engine. But not all the
difference. As s/v porting allows for a true hemispherical combustion
chamber with centrally located spark plug and a very efficient pumping
and combustion process. As you noted.
.
However, there are other very significant
reasons why the s/v engine does so well. .
.
All internal combustion engines have
"inertia loss". The energy used to put a weight in motion and an
equal amount to stop it, and reverse its direction. (Takes the same to
stop it as it does to start it). The valve train with its cam followers,
tappets, push-rods, rocker arms, valves, adjusting. & locking nuts
and especially the valve springs [that take considerable energy] to compress.
Together these items account for a considerable inertia power loss. All
power comes from the fuel tank...
.
The s/v engine eliminates this inertia
loss, as the motion of the sleeve does NOT go up and down. It is driven
by a geared crank driving the sleeve through a ball and socket and
the motion of the sleeve is of a circular path.
.
However there is another much more
significant reason for overall fuel savings that "appears" to be improved
engine efficiency. It is because the s/v valve engine with its intake and
exhaust ports on the sides of the cylinders instead of on top, as a poppet
valve engine is configured and it allows for a reduction in over-all engine
diameter. From 68 to 58 inches. from 3630 sq" to 2640 sq". Nearly a 30%
reduction in cross sectional area. The aerodynamic drag penalty for
boring such a big hole in the sky is enormous. Especially at high speed.
This accounts for the major difference.
.
When I get some time I will dig up
some more related info. and send it
on. I like your eMail handle.
I soloed Yellow Taylor Cub in 1938
.
Ralph-1
Another
Link for Sleeve Valve Engines used in the Hawker Hurricane
1-1-2004 Dear Webmaster,
Love your stuff. Herschell Smith published an aeroengine book
with the sleeve & cylinder drawn "developed", as if folded
out flat, to illustrate the motion of the sleeve. It's a great read;
so too is Graham White's book, but it's quite technical. My guess
as to why sleeve valves aren't more widespread is that because one
of the ports acts as both an intake and an exhaust, emissions are a factor.
Oil consumption may also be an issue, remembering that aircraft like
the Sea Fury had a 40 gallon oil tank. I wonder also whether sleeve
valves limit the compression ration of an engine, and hence are fine
for supercharged jobs, with typical static compression rations around 6
to 1, but not automotive applications.
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