Dissertação
Análise numérica 3D de spray de etanol em câmara com contrapressão
Fecha
2018-02-21Autor
Roberto Ribeiro Schor
Institución
Resumen
Due to the new regulations in environment laws the new emission standards are increasingly
more restrictive. Therefore, new engine technologies has been researched to make the
engines more fuel efficient and to decrease the emissions. The direct injection is one of those
new technologies, to substitute the old port fuel injection, allowing to improve the control of
the cylinder combustion. For this, specially in the cases of stratified strategy or compression
ignition engines, the control of the spray injection is very important to control of the
air/fuel ratio through the cylinder. The formation of the air fuel mixture, and consequently
the evolution of the spray and its atomization combined with the diffusion and evaporation
of the fuel in the air together with the charge motion in the combustion chamber are very
important for controlling and optimizing the combustion. Since the optical access to the
combustion chamber is difficult to access or prohibitive due to costs, the most coherent
technique for analyzing the effects of spray in the air mixture in the combustion chamber is
the numerical simulation approach. The aim of this dissertation is to develop and validate
a Computer Fluid Dynamics (CFD) methodology for modeling and analyzing the ethanol
Spray generated by a pressure-swirl automotive injector in a chamber with back pressure
utilizing the software OpenFOAM an open source code. The methodology employed to
evaluate the ethanol spray pattern with OpenFOAM was validated with experimental data
up to 5 bar of vessel pressure. The initial fuel drop size distribution was described by two
models, Rosin Rammler and LISA, and the subsequent droplet break up was described
by three models, Diwakar, KHRT and TAB for vessel pressures of 1 bar and 5 bar. The
droplet mean diameter value was validated with experimental data at 1 bar. For pressures
up to 5 bar, among the evaluated models, the optimum models which were able to capture
the flow pattern of the ethanol spray are the atomization model LISA with the secondary
break up model TAB and the PDF function Rosin Rammler with either KHRT or TAB
break-up models. Concluding, for the usual cases of injection in spark ignition engines the
models implemented in this dissertation were validated against experimental data and can
be utilized in more complex models, e.g. dynamic spray simulation with a moving mesh.