Conceptual model description of the double injection strategy applied to the gasoline partially premixed compression ignition combustion concept with spark assistance

New combustion concepts applied to compression ignition engines are focused on achieve low temperature combustion together with a lean mixture distribution by allowing extra time from the end of injection to the start of combustion. Recently, the use of gasoline in a compression ignition engine under PPC conditions has been demonstrated as a suitable technique to achieve this extra mixing time, however the concept has also demonstrated difficulties under low load conditions using gasoline with octane number up to 95. The use of spark assistance with single injection operation has been found to be an appropriate way to improve the combustion control, providing both temporal and spatial control over the combustion process. The current paper details the influence of the double injection strategy on the spark assisted partially premixed combustion concept compared with the single injection strategy. For this purpose, a reference combustion cycle for both injection strategies is compared in terms of the main parameters derived from the in-cylinder pressure signal as well as OH* and natural luminosity images acquired from the single-cylinder transparent engine. The cylinder head used along the research has been modified including a spark plug. In addition, a detailed analysis of the air/fuel mixing process has been developed by means of a 1-D in-house spray model. (C) 2014 Elsevier Ltd. All rights reserved.