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COB80 SIMULAÇÃO DE FLUTUAÇÃO DE VÁLVULA EM MOTORES DE COMBUSTÃO INTERNA / VALVE FLOTATION SIMULATION IN INTERNAL COMBUSTION ENGINES

Rafael Antônio Comparsi Laranja, Gustavo Müller Martins & Rogério José Marczak

Departamento de Engenharia Mecânica, Grupo de Mecânica Aplicada, Escola de Engenharia - UFRGS - Rua Sarmento Leite, 425, Porto Alegre, RS, Brasil, CEP 90050-170 - E-mail: comparsi@vortex.ufrgs.br, rato@vortex.ufrgs.br

This work presents some results obtained with a numerical simulation of the valves behavior in internal combustion’s engines. The mathematical model used is simple and consider all the subsystems which influence in valve works, how as: cam, push road, spring, lifter, etc. The governing equations are solved using the finite difference method for a wide range of operational parameters. By monitoring the contact forces between two components in the kinematics chain it is possible to detect the rotation bands which produce the valve flotation. Several graphs are presented to help the designer to avoid such phenomenon.

Keywords: Internal combustion engines, valve flotation, numerical simulation, cam, lifter. Motores de combustão interna, comando de válvulas, flutuação de válvulas.

COB181 ANÁLISE DINÂMICA DE MECANISMOS FLEXÍVEIS PLANOS / DYNAMIC ANALYSIS OF FLEXIBLE MECHANISMS

Armando Morado Ferreira & Clodio Alberto Pastro Sarzeto

Departamento de Engenharia Mecânica e de Materiais, Instituto Militar de Engenharia - IME - Praça Gen Tiburcio 80, Praia Vermelha, Rio de janeiro, CEP 22290-270. E-mail:d4sarzet@epq.ime.eb.br

This work describes a formulation for the dynamic analysis of planar mechanisms with rigid or flexible bodies. The flexible bodies are subjected to small deformations and large translational and/or rotational displacements, and to each one reference and elastic coordinates are associate. The reference coordinates are refered to a global inertial frame, and the elastic coordinates are refered to a proper local floating reference frame. The flexible bodies are discretized by the finite element method, and the joints are modelated by kinematic constraints equations, wich leads to a system of differential-algebraic equations of motion. Results for a slider-cranck mechanism with a flexible rod are shown and confronted to other similar experimental and numerical results.

Keywords: Flexible Mechanisms, Multibody Systems, Mecanismos Flexíveis, Sistemas Multicorpos.

COB1454 OTIMIZAÇÃO NO BALANCEAMENTO DE MECANISMOS ESPACIAIS DO TIPO "RSSR" / OPTIMUM BALANCING OF SPATIAL "RSSR" MECHANISMS

Tarcisio Antonio Hess Coelho & Valter Francisco Arruda Alves

Departamento de Engenharia Mecânica, Escola Politécnica-USP - CEP 05508-900 São Paulo,SP - Brasil - E-mail: TARCHESS@USP.BR

The Generalized Reduced Gradient method of numerical optimization was successfully applied in obtaining the reduction of moments and forces transmitted by a spatial RSSR mechanism to its base. Such a modification of dynamical behavior of the mechanism, or balancing, was achieved by the addition of counter-weights attached to the movable links in an off-line position. The evaluation of the obtained optimum configuration has been performed by comparing the measured vibration levels of the base of physical models of the balanced and unbalanced mechanism.

Keywords: Mecanismos, balanceamento, otimização / Mechanisms, balancing, optimization.