Historically there have been many engines that compress their combustion air outside of the combustion and expansion area. Perhaps the best known is the Brayton engine, after George Brayton, Boston who patented the cycle in 1875. The Brayton engine used a separate cylinder to compress the fuel and air charge which was then transferred to the combustion cylinder for the burn and expansion. The Brayton engine enjoyed considerable service in steel and well industries. They would run on almost any fuel including various refinery gases and well head gas. They did not require any octane rating. They usually used hot finger ignition which was better understood by operators. I remember them as a child in the 50's in northern Michigan where they were used on drilling platforms. The Brayton engine is two cycle and does not breath well on its own. Operators soon learned that you could increase power considerable by putting a long straight pipe on them. They could be heard miles away.
In the early 1900s many patents were granted to inventors who realized that the work required for compression would be less if the compression were done outside of the hot working chamber. I do not know of any of them other than the Brayton that were successful.
The wankel rotary compresses its combustion gas then transfers it to another area for combustion. The Louis Kramer engine is a composite that uses some outside compression and finishes compression in the working cylinder. And then there are gas turbines and jet engines that use different areas for compression, combustion and expansion.
