Rapid Compression Machine Tests for Brazilian Otto Cycle Fuels

Rapid Compression Machine (RCM) is an experimental tool developed to study engine combustion parameters. The RCM used is a pneumatically and hydraulically driven device which reproduces a single combustion shot, considering a compression and a partial expansion stroke. This paper describes RCM adaptations made in order to run Otto cycle tests using Brazilian regular gasoline (E25) [1]. These adaptations enable pre-vaporized air-fuel mixture combustion tests, representative of port fuel injection engines, by using a gasoline direct injection (GDI) injector. It is also presented RCM piston displacement and cylinder pressure comparisons to a real engine and RCM comparative results for different spark timings and compression ratios. These results show that RCM reproduced satisfactorily piston displacement and pressure curves during the combustion shots, when compared to real engine curves. It also shows that RCM changes in spark timing and compression ratios followed the same trends that were expected by engines’ theory. It was possible to confirm that RCM is able to reproduce engine combustion, using very small fuel volume and changing parameters that are not easily and quickly adjusted in a conventional engine test bench. These aspects may reduce research and development time and cost.