This paper focuses on review of the current patent landscape of toroidal rotary internal combustion engines.
Toroidal engines are rotary-type internal combustion engines that use circular-sectioned pistons contained within a torus
(or toroidal) shaped chamber. Recent engine designs are discussed and, depending on the fundamental design principals,
are categorized using a classification system. It is found that the engine designs can be classified by the rotor configuration,
the method of power transmission between the rotors and drive shaft, and the method of timing spark ignition and
air-flow through the engine. From review of the patents presented, it is found that there are many all-encompassing patents
covering the overall operation of toroidal engines. However, there is limited performance data, peer-reviewed articles,
and commercial products to indicate the advantages of one design over the other. Therefore, it is recommended that
development be focused on the design and configuration of the subset components of these engines. This will lead to an
understanding of the physical limitations, trade-offs, and advantages of toroidal engine designs and components for comparison
against one-another. This understanding will increase chances of commercial success of improvements made by
developers, and strengthen the overall intellectual property archive and knowledge-base for toroidal rotary engines.