PERFORMANCE VARIATION AND FUEL SYSTEM BEHAVIOR OF A PORT INJECTION SPARK IGNITION ENGINE USING GASOLINE– ISOBUTANOL BLENDS WITH HIGH CONCENTRATION OF ALCOHOL

摘要

Using alcohols for fueling spark ignition (SI) engines can significantly contribute to thernreduction of green house gas emissions. However, this category of renewable fuels presentsrnseveral challenges when used in unmodified engines. Isobutanol, like shorter chain alcoholsrnsuch as methanol or ethanol, features a higher latent heat of vaporization compared torngasoline. This leads to difficult cold starts during cold weather. Also, as it contains anrnincreased quantity of oxygen, fuel flow needs to be increased in order to maintain the samernrelative air-fuel ratio as for gasoline operation. A significant advantage of isobutanolrncompared to shorter chain alcohols is that it is fully compatible with the materials used inrngasoline fuel systems.rnThe paper presents an experimental study of engine performance and fuel system behavior ofrna port injection engine. Measurements were conducted on a chassis dynamometer using arnpassenger car powered by a SI engine. As well as fueling the engine with gasoline, 50% andrn70% volumetric concentrations of isobutanol mixed with the conventional fuel were used.rnDuring the initial electronic control unit’s learning period, right after switching thernconventional fuel to gasoline–isobutanol blends, a significant power loss was observed at fullrnload and a slightly erratic engine behavior in transient conditions. While the fuel system fullyrnadapts to the 50% concentration and practically no loss of power was observed after a fewrnminutes of operation, 70% isobutanol mixed with gasoline was found to be right at the upperrnlimit of the electronic control unit’s learning range. As a result, the fuel system has to bernmodified in order to obtain the same full load performance with high concentrations ofrnisobutanol, compared to gasoline operation. Also, a slightly lower fuel conversion efficiencyrnwas observed during part load operation with gasoline-alcohol blends compared to using thernconventional fuel alone.