Ross type stirling engine with a much looser one (lower fill factor, more
flow
area) made of knitted stainless wire (actually one of those kettle
lime-scale traps). With the inner sleeve and regenerator fitted into
the hot cap I performed a flow test (alright, I blew down it!) which
showed that the looser mesh did indeed give significantly
lower resistance to air flow.
Once started and thoroughly warmed through (this takes some time, I
think due to the substantial lump of iron on the top end of the inner
sleeve) the engine ran up to a higher speed than before, no doubt due
to lower pumping losses, it did not however feel significantly more
torquey.
After a good long run I took the hot end apart and was rewarded with
a nice range of oxide colours on the regenerator mesh indicating the
temperature gradient through the engine. If I could remember the
colour/temperature relationship from school metalwork (and wasn't
colour blind) I might even be able to estimate the temperatures
involved.
Next material I have to hand is pan scourer made of coiled up
stainless strip.
Photo of regenerator and sleeve after run at :-
formatting link
(last pic in 'all hot air' album)
Nick H.