Abstract
High cetane number of DME enables to operate the low compression ratio engines produced for spark ignition engine driven with the direct gasoline injection system. And no soot formation combustion enables to operate with high exhaust gas recirculation rate. Therefore, the DME engine can operate with the stoichiometric working gas. The NOx concentration from DME engine at stoichiometric working gas is very low as the same level of HCCI engines. Naturally, the three-way-catalyst system for S.I. engines can apply to this low compression ratio stoichiometirc working gas combustion DME engines. This concept can overcome the weak point of HCCI engines, namely how to extend the operating regions for high load with HCCI combustion. The high rate EGR at low load shows a relatively unstable combustion, therefore the combination of HCCI combustion at low load and the stoichiometoric working gas combustion at middle and high load overcomes the problem of emissions from reciprocating engine system and increasing the demand of crude oil in the future.
