Effect of Bioethanol Blended Diesel Fuel and Engine Load on Spray, Combustion, and Emissions Characteristics in a Compression Ignition Engine

Abstract

This study investigates the effect of engine load condition on the injection spray, combustion, and exhaust emissions characteristics of a diesel-bioethanol blended fuel diesel engine. In this study, the injection characteristics, such as the effective flow diameter and the effective flow velocity, were calculated from the nozzle flow model. The macroscopic spray characteristics of diesel-bioethanol fuels were measured and analyzed using a spray visualization system. Using a four-cylinder test engine with 1.5 L of displacement, the combustion pressure, heat release, and emission characteristics were measured and analyzed. In addition, properties of blended fuel were measured and analyzed. This study revealed that the physical properties (density, viscosity, and surface tension) and chemical properties (cetane number, heating value, and distillation) of diesel-bioethanol blended fuels generally decreased with increased bioethanol content. The increase in bioethanol fuel resulted in easy vaporization at the same temperature condition. After energizing, the increase of engine load caused an increase in spray tip penetration. The spray cone angle was mainly affected by the blending of bioethanol, not the engine load. The increase of engine load led to a decrease of ignition delay by the high gas temperature, and it also caused an increase in the combustion duration for the same fuel amount. In the exhaust emissions, the increase of engine load affected the increase in both the NOx and ISNOx emissions, the decrease of CO and HC emissions. At a high engine load, CO and HC emissions were quite similar in D100, DE10, and DE20 fuels due to the increased oxygen content.