Guarato, A., Ticona, E., and Braga, S., "Development of a flex-fuel rotary engine with variable compression ratio," SAE Technical Paper 2016-36-0218, 2016, doi:10.4271/2016-36-0218.
Energy independence and reduction in pollutant emissions are a center of interest for several researchers and car manufacturers. Renewable fuels have gained in popularity because of their sustainability and, in some cases, lower amounts of greenhouse gases. Moreover, energy diversification is also required by all countries. One possible solution is the use of biofuels such as ethanol, methanol, etc. These biofuels have been shown as good candidates as alternative fuels for vehicles because they are liquid and they have several physical and combustion properties similar to gasoline. Alcohols have also a higher octane number and oxygen content than gasoline. This allows the alcohol engines to have much higher compression ratios (CRs), and thus, better BTE (brake thermal efficiency). Brazilian car manufacturing industry has developed flexible-fuel vehicles, introduced in 2003, which became a commercial success. Flex fuel internal combustion engines (ICEs) can run on any proportion of Brazilian gasoline (E27 blend) and hydrous ethanol (E100), allowing the use of the cheaper fuel available. However, conventional flex fuel engines have a fixed CR, generally between the ideals CRs for gasoline and ethanol, which leads to lower BTE and higher fuel consumption. In order to reduce or eliminate these issues, this paper presents the Kopelrot engine, a flexible fuel rotary engine with dynamically variable compression ratio.