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The increasing use of downsized turbocharged gasoline engines for passengers cars and the new European homologation cycles (WLTC and RDE) both impose an optimization of the whole engine map. More weight is given to mid and high loads, thus enhancing knock and overfueling limitations. At low and moderate engine speeds, knock mitigation is one of the main issues, generally addressed by retarding spark advance thereby penalizing the combustion efficiency. At high engine speeds, knock still occurs but is less problematic. However, in order to comply with thermo-mechanical properties of the turbine, excess fuel is injected to limit the exhaust gas temperature while maximizing engine power, even with cooled exhaust manifolds. This also implies a decrease of the combustion efficiency and an increase in pollutant emissions. Water injection is one way to overcome both limitations.

An automatic mesh generation process for a body fitted 3D CFD code is presented in this paper along with the methodology to guarantee the mesh quality. This tool named OMEGA (Optimized MEsh Generation Automation) uses a direct coupling procedure between the IFP-C3D solver and a hybrid mesher Centaur. Thanks to this automatic procedure, the engineering time needed for body fitted 3D CFD simulation in internal combustion engines is drastically reduced from a few weeks to a few hours. Valve and piston motion laws are just given as input files and geometries and meshes are automatically moved and generated. Unlike other procedures, this automatic mesh generation does not use an intermediate geometry discretization (STL file, tetrahedral surface mesh) but directly the original CAD that has been modified thanks to the geometry motion functionalities integrated into the mesher.

CNG is one of the most promising alternate fuels for passenger car applications. CNG is affordable, is available worldwide and has good intrinsic properties including high knock resistance and low carbon content. Usually, CNG engines are developed by integrating CNG injectors in the intake manifold of a baseline gasoline engine, thereby remaining gasoline compliant. However, this does not lead to a bi-fuel engine but instead to a compromised solution for both Gasoline and CNG operation. The aim of the study was to evaluate the potential of a direct injection spark ignition engine derived from a diesel engine core and dedicated to CNG combustion. The main modification was the new design of the cylinder head and the piston crown to optimize the combustion velocity thanks to a high tumble level and good mixing. This work was done through computations. First, a 3D model was developed for the CFD simulation of CNG direct injection.

A full 3D Large Eddy Simulation (LES) of a four-stroke, four-cylinder engine, performed with the AVBP-LES code, is presented in this paper. The drive for substantial CO₂ reductions in gasoline engines in the light of the global energy crisis and environmental awareness has increased research into gasoline engines and increased fuel efficiencies. Precise prediction of aerodynamics, mixing, combustion and pollutant formation are required so that CFD may actively contribute to the improvement/optimization of combustion chamber, intake/exhaust ducts and manifold shapes and volumes which all contribute to the global performance and efficiency of an engine. One way to improve engine efficiency is to reduce the cycle-to-cycle variability, through an improved understanding of their sources and effects. The conventional RANS approach does not allow addressing non-cyclic phenomena as it aims to compute the average cycle.

Future Diesel engines must comply with conflicting demands: more stringent emission standards and customer desire for “fun-to-drive” vehicles, i.e. higher torque and power output. Given such objectives, engine development investigates new clean combustion processes, such as low temperature combustion (LTC), highly premixed combustion (HPC) or homogeneous charge compression ignition (HCCI) combustion and the possibility to combine them with current solutions. Lately, IFP has developed a near zero NOx and particulate combustion process, the NADI™ concept, a dual mode engine application switching from a novel lean combustion process at part load to conventional Diesel combustion at full load. Given the complex nature of these new combustion processes, the concept development relies increasingly on three-dimensional Computational Fluid Dynamics (CFD) tools as they help grasp the basic phenomena at stake and reduce development time and costs.

The drive for substantial CO2 reductions in gasoline engines in the light of the Kyoto Protocol and higher fuel efficiencies has increased research on downsized, turbocharged engines. Via a higher intake air pressure, an increase in specific power output can be reached on a comparatively smaller sized engine, in order to ensure high torque capabilities, while allowing a fuel saving of about 20%. This fuel efficiency benefit includes the advantages of direct injection (DI) technology which avoids crossflow of fuel. This paper presents the capabilities of Computational Fluid Dynamics to aid in the development of such engines. Particularly, the IFP-C3D code offers several recently developed models which permit to estimate, with good accuracy, the evolution of the combustion under given working conditions. Moreover, the capability of the model to predict knock occurrence is very helpful for engine designers within the framework of development of new downsized turbocharged engines.