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Exhaust emission reduction and improvements in energy consumption will continuously determine future developments of on-road and off-road engines. Fuel flexibility by substituting Diesel with Natural Gas is becoming increasingly important. To meet these future requirements engines will get more complex. Additional and more advanced accessory systems for waste heat recovery (WHR), gaseous fuel supply, exhaust after-treatment and controls will be added to the base engine. This additional complexity will increase package size, weight and cost of the complete powertrain. Another critical element in future engine development is the optimization of the base engine. Fundamental questions are how much the base engine can contribute to meet the future exhaust emission standards, including CO2 and how much of the incremental size, weight and cost of the additional accessories can be compensated by optimizing the base engine.

Several oxygenates have been proposed and tested for use with or as diesel fuel. This paper examines two such oxygenates, CETANER™ and dimethyl ether (DME), partially or wholly produced by Air Products and Chemicals, Inc's Liquid Phase Technology. In previous studies on a single cylinder compression ignition engine and a Volkswagen TDI four cylinder engine, significant reductions in particulate matter emissions were observed with blends of CETANER™ in diesel fuel. In this study, experiments were performed on a multi-cylinder Navistar 7.3L Turbodiesel engine confirmed and extended the observations from the earlier studies. This is an important step in not only showing that the fuel does perform on each type of engine in similar fashion, but also in showing that DME and its derivatives can give consistent, significant results in lowering emissions. The oxygenated fuels were blended to achieve a net addition of 2 wt.% oxygen in the blended fuel.