Abstract
Basic investigation aiming to develop a gasoline engine of high thermal efficiency is presented in this paper. The high efficiency is established by increasing the compression ratio while the engine is operated in SI mode. In order to suppress knocking, fuel is thermally processed to raise the octane number by partially cracking the hydrocarbon molecule prior to supply fuel to the engine. The primary reference fuel 90 (PRF90), which shows that 10% n-heptane is blended with 90% iso-octane, was applied to the test fuel. And the regular gasoline, which octane number was approximately 90, was also used as the test fuel in order to show the practical rise of thermal efficiency. The fuel reformer was constructed in this study and the fuel component was measured with gas chromatography and mass spectroscopy (GC - MS). It was found that the fuel was partially cracked into small size hydrocarbons including methane, ethylene, propene, and so on. Under the high temperature condition over 973 K, benzene and toluene were also formed in the reformed fuel, which would suppress knocking. Both gas and liquid components of the reformed fuel was supplied to a test engine. The test engine is a 4-cylinder, 2-litter, turbo gasoline engine and the compression ratio was modified to be 12. The thermal efficiency was investigated for operating conditions set as IMEP 236 kPa, 437 kPa and 623 kPa at 1600 rpm, and IMEP 700 kPa at 1200 rpm. The thermal efficiency increased by 4.2% using PRF90 and by 0.8% using regular gasoline. Knock was suppression by 1.5% using PRF90 and by 1.2% using regular gasoline.
