Análisis y validación por volumen finito de los coeficientes rotodinámicos de rigidez de una chumacera corta con y sin presurización

Abstract

Understanding the behavior of fluids that interact with solid structures, like the design of hydrodynamic bearings involves the study of mathematical models and experimental complex, this fact is of fundamental importance in many designs of mechanical systems. In modern literature, has been analyzing the behavior of the fluid in this type of bearings for the different cases, either the infinitely short bearing (also called Fred Ocvirk solution), or in the case of the infinitely long bearing (given by Sommerfeld equation). Studies (theoretical and experimental) of the behavior of the lubricant film in the bearing are usually resolved by the Reynolds equation, this is the simplified solution of the Navier-Stokes equations and this approach ignores the complexity of the flow and makes assumptions like the bearing must meet the conditions \] ^ < ` abb and the modified Reynolds number is less than 1, which indicates a stable laminar flow. Computational Fluid Dynamics (CFD) like numerical modeling tool allows a better idea about the behavior of the fluid phenomena by it solving the Navier-Stokes equations, the mass equation and energy balance. This Work uses the Reynolds and Navier-Stokes equations, the hydrodynamic lubrication theory and finite volume methodology with the software ANSYS-CFX simulation. The work analysis of this research is seen as fluid-structure with a shaft-bearing model designed computationally to study the behavior of the oil film inside of a hydrodynamic bearing with/without pressurization using the finite volume method; the software used simulate and analyze the transient behavior in three dimensions, which shows the dynamic behavior of short bearings under different pressurizations to obtain the variables mean such as fluid velocity, pressure the position of the shaft, etc. The effects of pressurization and the Locus of the shaft are measured; this differences of pressurization changes and differences of the equilibrium point to change the point of cavitation, can be made the innovative aspect of this research, where the complexity the equations involved and the methodology of programming to simulate can be a better study of this engineering problem the locus of equilibrium pressurized analyzing the various cases of pressurization of the lubricant in the first ports located at 90 degrees. Chapter 1, refers to introduction of Rotodynamic, , the progress of this discipline in Mexico, also a short introduction to the theory of lubrication (better known as Tribology) and a brief meaning of the aspects or physical phenomena involved, as well as to provide an overview of common problems that exist in hydrodynamic bearings. In Chapter 2 introduces the reader to all nomenclature, the governing equations, the analytical procedures and mathematical models for hydrodynamic bearings, all the equations discussed in this chapter were used to later chapters for the CFD study. Chapter 3 presents a brief introduction to what is the Computational Fluid Dynamics, arises how to create the geometry and the meshing bearing model to research, set the boundary conditions to which the simulated system is affected, we define the model physics and pre simulation process, is reviewed the problems that this involves the development of designs simulated fluid-structure type for numerical analysis and effected the computer simulation of the behavior of the fluid film in a hydrodynamic bearing with a ratio of ` c and dS fe = 508.8 without pressurization, where gravity provides the pressure drop required to deposit the lubricant on the clear radial between journal and bearing. Chapter 4 reviews the locus of equilibrium behavior from physical modeling in Chapter 3 for the case of the bearing with superior power is validated model where all the fluid structure of the simulation results are compared and validated with analysis of world-class researchers (such as those obtained in the laboratory of Mechanical Vibrations and Rotodynamic in Insituto Politecnico Nacional by Dr. Julio Cesar Gomez Mancilla) and comparing the equilibrium point with the international literature based on the Reynolds equation to validate and prove the accuracy of the correct application of the equations, boundary conditions and model the correct behavior. Chapter 5 uses the results obtained in Chapter 4 for the case where the power is increased lubricant 2, 6 and 10 times, we obtain the locus of equilibrium for such cases is pressurized and is derived from these points Rotodynamic Stiffness coefficients for cases with and without pressurization by a 5-point modeling and the theory of finite differences, in Chapter 6 discusses the conclusions drawn throughout this thesis and the same for all future jobs that can be obtained from such research. For understanding the content of this thesis work is required prior knowledge of the theory of lubrication, a good understanding of fluid mechanics and Rotodynamic, as well as good programming in ANSYS-CFX and Excel.