Automotive spark-ignited direct-injection gasoline engines

The development of four-stroke, spark-ignition engines that an designed to inject gasoline directly into the combustion chamber is an important worldw ide initiative of the automotive industry. The thermodynamic potential of s uch engines for significantly enhanced fuel economy, transient response and cold-start hydrocarbon emission levels has led to a large number of resear ch and development projects that have the goal of understanding, developing and optimizing gasoline direct-injection (GDI) combustion systems. The pro cesses of fuel injection, spray atomization and vaporization, charge coolin g, mixture preparation and the control of in-cylinder air motion are all be ing actively researched, and this work is reviewed in detail and analyzed. The new technologies such as high-pressure, common-rail, gasoline injection systems and swirl-atomizing gasoline fuel injectors are discussed in detai l, as these technologies, along with computer control capabilities, have en abled the current new examination of an old objective; the direct-injection , stratified-charge (DISC), gasoline engine. The prior work on DISC engines that is relevant to current GDI engine development is also reviewed and di scussed. The fuel economy and emission data for actual engine configurations are of significant importance to engine researchers and developers. These data hav e been obtained and assembled for all of the available GDI literature, and are reviewed and discussed in detail. The types of GDI engines are arranged in four classifications of decreasing complexity, and the advantages and d isadvantages of each class are noted and explained. Emphasis is placed upon consensus trends and conclusions that are evident when taken as a whole. T hus the GDI researcher is informed regarding the degree to which engine vol umetric efficiency and compression ratio can be increased under optimized c onditions, and as to the extent to which unburned hydrocarbon (UBHC), NOx a nd particulate emissions can be minimized for specific combustion strategie s. The critical area of GDI fuel injector deposits and the associated effec t on spray geometry and engine performance degradation are reviewed, and im portant system guidelines for minimizing deposition rates and deposit effec ts are presented. The capabilities and limitations of emission control tech niques and aftertreatment hardware are reviewed in depth, and areas of cons ensus on attaining European, Japanese and North American emission standards are compiled and discussed. All known research, prototype and production GDI engines worldwide are revi ewed as to performance, emissions and fuel economy advantages, and for area s requiring further development. The engine schematics, control diagrams an d specifications are compiled, and the emission control strategies are illu strated and discussed. The influence of lean-NOx catalysts on the developme nt of late-injection, stratified-charge GDI engines is reviewed, and the re lative merits of lean-burn, homogeneous, direct-injection engines as an opt ion requiring less control complexity are analyzed. All current information in the literature is used as the basis for discussing the future developme nt of automotive GDI engines. (C) 1999 Elsevier Science Ltd. All rights res erved.