Click pic to visit original site.
Here is a link to one Circular or rotary engine that actually ran with no muffler.
It is of Eccentric type with abutments used as separators between chambers.
You can visit their site kept by the sun of the inventor with and interview.
I hope to get some new pics .
I have no info about thermal efficiency or power rating or fuel consumption.
I emailed the sun of the inventor , he confirms he still has it in storage.