Control of Diesel Engine Pollutants by Split Injection Method using Muitizone Model

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Abstract
The reduction of NOx without the degradation of soot emission and/or fuel economy necessitates the grasp of the in-cylinder temperature behavior, since NOx is mainly generated within localized high temperature regions in the cylinder of diesel engines. Therefore, a split injection method to reduce NOx has been proposed. In this method, injection is divided into two steps, the main injection of larger quantity and the sub-injection of smaller quantity. The sub-injection is practiced late into the flame of the main injection fuel. The moment of flame tip approaches the nozzle hole, the sub-injection is practiced, and the sub-injection spray folded in the flame. This attempted to control the localized high temperature regions by promoting the mixing of in-cylinder gases owing to supplementary fuel injection energy. Thus split injection suppresses the formation of nitrogen oxide. In this study, a four-zone model is used in predicting the emissions particularly of NO with the application of split injections. The combinations of single injection and split injections of 40-60, 35-65, 30-70, 25-75 and 20-80 proportions were tried. The combinations with different crank angle intervals of 3°, 4°, 5°, 6° and 7° between the main and sub-injection were also investigated. The combinations of single injection, split injection proportions and crank angle intervals were selected based on Nehmer et al [4]. Also the effect of design and operating conditions of engines on the emission of NO, CO and Soot with optimized spilt injection proportion of 30-70 and a gap of 5 degrees crank angle were studied.

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