This is a copy scaled from the patent file of a valvular conduit for a Tesla turbine. It is basically a one way valve with no moving parts and works based on the pressure drop from turbulence from air traveling the wrong direction. The STL file was 2 bodies with tapped holes to machine from billet so with printed item you cannot see the internal workings unless you print with transparent filament or stop print before cover is finished.
Just updated model to have tube ends and is 1st print. Hope to be able to demonstrate resistance in one direction when air is blown through the conduit. Have fun.
Comment: just printed, should be scaled up a bit, 25% to 50% to make it a bit better as it is fairly small. Should still work to demonstrate for air restriction. STL object size is 95.2mm x 14.3mm x 7.9mm so this should give you idea of size.
Supports only to build plate to support the inlet and outlet connections.
I traced over the patent file image to create the internal workings scaled to patent image.
shown as a section, print wide side flat to build plate (Opposite of open section side shown)