Search Results

Liquid atomisation is an important technical field for a wide range of engineering and industrial applications, particularly in the field of internal combustion engines. In these engines, in fact, the amount of pollutants at the engine-out interface is directly related to the quality of the combustion process, which is in turn determined by the quality of the air-fuel mixture preparation in Direct Injection (DI) engines. As a consequence numerical-experimental research is crucial to their development. Despite the significant amount of research that has been carried out on DI engines simulation, breakup modelling is still a challenge. In this paper we present a new numerical model for multiphase flows that could be particularly suited for liquid jet and droplet breakup simulation. The model is based on a Lattice Boltzmann (LB) solver coupled to a higher order finite difference treatment of the kinetic forces arising from non-ideal interactions (potential energy).

Multidimensional numerical simulation of the combustion processes in spark ignition engines were performed using the Coherent Flame Model (CFM) which is based on the flamelet assumption. The CFM technique uses a transport equation to model the evolution of the flame surface, taking into account its advection, diffusion, production and destruction in a turbulent reacting flow. There are two model constants in a CFM approach, one associated with the flame production term and another with the destruction one. The goal of this work is to find a value for the above-mentioned constants able to obtain a good predictive capability of the combustion model varying the functional parameter of a S.I. multipoint injection engine. A comparison between experimental and numerical is carried out to test the combustion model. In order to start with appropriate initial fluid dynamic conditions the engine simulation take into account also the intake phase.

Computational Fluid Dynamics is nowadays largely employed as an effective optimization tool in the automotive industry, especially for what concerns aerodynamic design driven by critical factors such as the engine cooling system optimization and the reduction of drag forces, both limited by continuously changing stylistic constraints. The Ahmed reference model is a generic car-type bluff body with a slant back, which is frequently used as a benchmark test case by industrial as well as academic researchers, in order to investigate the performances of different turbulence modeling approaches. In spite of its relatively simple geometry, the Ahmed model possesses many of the typical aerodynamic features of a modern passenger car - a bluff body with separated boundary layers, recirculating flows and complex three-dimensional wake structures.

Though CFD methods have become very popular and widespread tools in the early as well as more advanced automotive design stages, they are still not so common in the motorcycle industry branch. The present work aims at the development of a comprehensive simulation environment, based on the open-source finite volume toolbox OpenFOAM®, for the aerodynamic and thermal fluxes optimization of a full motorcycle-and-rider geometry. The paper is divided in two parts: in the first one, the OpenFOAM® code is evaluated for a cold flow aerodynamic analysis, using a slightly simplified version of the Aprilia RSV4 motorbike geometry; in the second one, a mixed reduced scale-full scale methodology is proposed for the simultaneous assessment of aerodynamic forces and heat transfer performances of the engine cooling system. Results have been compared against other well established commercial CFD packages and, where available, with experimental measurements.