Active Squeeze Film Dampers Research Articles

Design and modeling of a novel active squeeze film damper

Rotating machinery support design with the aim of reducing the amplitude vibration and force transmitted to the foundation has significant importance regarding the various applications of these machineries. In this paper, a theoretical model for an active squeeze film damper (ASFD) is introduced as an option in the vibration control field. The design is based on the SFD with the controllability characteristics of magnetic bearing, which allows the development of a variable force, and a change in fluid film stiffness and damping. It is assumed that the SFD and the AMB are collocated, whether adjacent or integrated in a single unit. Expressions for the oil film forces and magnetic force are obtained. Then, the dynamic equations of the combine both bearings in a single bearing are presented. The vibration control of a rigid rotor is taken as an example of the application of the new design. The possibility of suppressing rotor vibrations and transmitted forces is demonstrated by means of numerical experiments. The simulation shows that in this type of application, good vibration control can be achieved by using new active squeeze-film damper. The potential benefits of varying the magnetic bearing parameters can thus be examined for any given rotor bearing configuration.

A Magnetorheological Fluid Damper for Rotor Applications

Even though we are still far from industrial applications, in the last decade there has been increasing attention directed toward the employment of electrorheological (ER) and magnetorheological (MR) fluids in active bearings and active squeeze film dampers in rotordynamics. MR fluids react to magnetic fields undergoing reversible changes in their mechanical characteristics, viscosity, and stiffness in particular. In previous literature, some applications of ER fluids in rotor squeeze film dampers can be found; however, on the contrary, little is reported on similar test rigs set up for MR dampers. In this work, the design of an MR squeeze film damper is presented and discussed. A numerical simulation has been carried out in order to evaluate the dynamic behavior of the damped rotor as a function of the magnetic field strength. The test rig is made of a slender shaft supported by two oilite bearings and an unbalanced disk. The damper is interfaced with the shaft through a rolling bearing. Electric coils generate the magnetic field whose field lines cross the MR film. Since the damping characteristics can be varied continuously by controlling the magnetic field, it is possible to have the optimum conditions for each regime of rotational speed. Preliminary tests are encouraging.

A Magnetorheological Fluid Damper for Rotor Applications

Even though we are still far from industrial applications, in the last decade there has been increasing attention directed toward the employment of electrorheological (ER) and magnetorheological (MR) fluids in active bearings and active squeeze film dampers in rotordynamics. MR fluids react to magnetic fields undergoing reversible changes in their mechanical characteristics, viscosity, and stiffness in particular. In previous literature, some applications of ER fluids in rotor squeeze film dampers can be found; however, on the contrary, little is reported on similar test rigs set up for MR dampers. In this work, the design of an MR squeeze film damper is presented and discussed. A numerical simulation has been carried out in order to evaluate the dynamic behavior of the damped rotor as a function of the magnetic field strength. The test rig is made of a slender shaft supported by two oilite bearings and an unbalanced disk. The damper is interfaced with the shaft through a rolling bearing. Electric coils generate the magnetic field whose field lines cross the MR film. Since the damping characteristics can be varied continuously by controlling the magnetic field, it is possible to have the optimum conditions for each regime of rotational speed. Preliminary tests are encouraging.

Study of a Novel Squeeze Film Damper and Vibration Generator

A novel squeeze film damper and vibration generator (SFD&VG) is proposed as an option in the vibration control field. The SFD&VG can be used as an active squeeze film damper (ASFD) or as a vibration generator (vibrator), for unidimensional vibration damping or generation. The SFD&VG concept is connected with current research to improve a common industrial process—drilling of deep holes. The SFD&VG is based on the variable area of the lubricant film, which allows the development of a variable force, and a change in fluid film stiffness and damping. The analysis is initiated for an elementary configuration of the SFD&VG—the infinite width Rayleigh step case—and then it is developed for an advanced elliptical SFD&VG. The Reynolds equation is solved for both pure squeeze film effect which provides vibration damping, and pure hydrodynamic wedge effect which provides vibration generation. The theoretical part is continued with the SFD&VG dynamic simulation. The SFD&VG experimental device and vibration measurements, performed for the two defined regimes, ASFD and vibration generator, are presented. Finally, the experimental and theoretical results are briefly compared. [S0742-4787(00)05201-2]

Comportement dynamique linéaire et non linéaire des paliers et des joints

High speed rotors set a lot of stability problems especially when the speed of rotation is going throuhg a critical speed. The dynamical behavior of the fluid bearings has, in that case, an important effect. This study presents several models of dynamical behavior og bearing taking into account the flexibility of the shaft. The squeeze film damper (SFD) behavior is also discribed. This element gives a lot of damping but its behavior is totally non linear. An approash of active squeeze film damper is presented: a variable clearance SFD or a variable viscosity SFD (fed with electro-rheological fluid) is used to control a flexible shaft.

Non-linear behavior of a flexible shaft partly supported by a squeeze film damper

High speed rotors pose stability problems, especially when the speed of rotation increases above a critical speed. In this case, the dynamic behavior of the fluid bearings has an important effect. This study presents several models of the dynamic behavior of bearings, taking into account the flexibility of the shaft. The behavior of the squeeze film damper is also described. This element provides damping but its behavior is totally non-linear. An approach for an active squeeze film damper is presented: a variable clearance squeeze film damper or a variable viscosity squeeze film damper (feed with electrorheological fluid) is used to control a flexible shaft. These technologies could be very promising in the future.

An Appraisal of a Proposed Active Squeeze Film Damper

A theoretical model for an active squeeze film damper (SFD) is introduced. The design makes it possible to change the radial clearance and land length of the SFD by adjusting the position of the damper ring. Expressions for the oil film forces are obtained. The vibration control of a flexible rotor is taken as an example of the application of the new design. The possibility of controlling rotor vibrations is demonstrated by means of numerical experiments.