The Concept and Experimental Results of Low Compression Ratio DME Engines Operated at Stoichiometric Mixture
18ICES/016
Authors
Shuichi Kajitani - Ibaraki University
Masayuki Takeda - Ibaraki University
Atushi Hoshimiya - Ibaraki University
Masaaki Kato - DENSO Corporation
Shigeharu Kobori - Ibaraki National College of Technology
Abstract
Among a lot of benefit of Dimethyl Ether (DME) as an alternative fuel, the combustion characteristic for diesel engines, are high cetane number and no soot combustion. The high cetane number enables to operate the low compression ratio diesel engines. No soot combustion enables to operate engines at high rate of exhaust gas re-circulation (EGR). Therefore, the DME engines become light weight and high engine speed with low NOx emission in the case of high EGR ratio such as stoichiometoric mixture. The NOx concentration from low compression ratio stoichiometric mixture combustion (LCSM) DME engine is very low as the same level of homogeneous charge compression ignition (HCCI) engines. Naturally, the three-way-catalyst system for S.I. engines can apply to this LCSM DME engines. This concept can overcome the weak point of HCCI engines, namely how to extend the operating regions to the high load. The weak point of LCSM DME engine is an unstable combustion at very low load because of the increased high EGR rate such as 80% at Pme=0.2MPa. Therefore, the combination of HCCI combustion at low load and the LCSM combustion at middle and high load can solve the problems of HCCI and LCSM DME engines.Furthermore, the engine based on this concept can apply to the engines for not only the heavy duty but also light duty automobiles. Then, DME and this combustion concept can overcome the increasing the demand of crude oil and the tight exhaust gas regulation in the future.