Squeeze film dampers (SFDs) are components used in many industrial applications, ranging from turbochargers to jet engines. SFDs are applied when the vibration levels or some instability threatens the safe operation of the machine. However, modeling these components is difficult and somewhat counterintuitive due to the multiple complex phenomena involved. After a thorough investigation of the state of the art, the most relevant phenomena for the characterization of the SFDs are highlighted. Among them, oil film cavitation, air ingestion, and inertia are investigated and modeled. The paper then introduces a numerical model based on the Reynolds equation, discretized with the finite difference method. Different boundary conditions for oil feeding and discharging are implemented and investigated. The model is validated by means of experimental results available in the literature, whereas different designs and configurations of the feeding and sealing system are considered. Eventually, an example of the application of a SFD to a compressor rotor for the reduction of vibration and correction of the instability is proposed. The paper provides an insight regarding the critical aspects of modeling SFDs, underscoring the limits of the numerical model, and suggesting where to further develop and improve the modeling.

Tilting-pad journal bearings are widely used in industry to support rotating shafts due to their high dynamic performance. The operating limits of these bearings are mainly represented by the maximum permissible temperature of the lined materials of the pads and by the minimum thickness of the oil-film under which mixed lubrication can occur. The current trend in bearing development sees the adoption of innovative materials in the production of the pads, that provide higher load capacity, higher temperature capability and greater fatigue resistance. In this paper, the static characteristics of bearings lined with different materials, will be investigated. The temperature distribution in the bearing will be evaluated by means of a full 3D thermal model whereas the deformation of the pads will be evaluated by means of a finite element model. At the end, the permissible operating range in terms of load and speed will be defined for each material by considering the limits on the maximum temperature, permissible mechanical stress and minimum oil-film thickness.

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The level of the vibrations and the presence of instability are the two most critical aspects regarding the operations of turbomachinery. To cope with this issues that may compromise the operation of the machines, squeeze film dampers (SFD) are often used in many industrial applications. Unfortunately, many complex phenomena characterize the dynamic behavior of these components and determine the high complexity of the modeling of these components. The most relevant phenomena involved in the characterization of SFDs are individuated after a comprehensive investigation of the state of the art. Among them, the oil film cavitation, the air ingestion, and the effect of the inertia are introduced. A modeling strategy based on the Reynolds equation is then presented. The boundary conditions to be adopted for the feeding and discharging of oil are investigated and implemented. Eventually, the finite difference model is applied to a practical example to evaluate the possibility to minimize the vibration level and to reduce the effect of the instability if a SFD is added to a rotodynamic system. Meaningful information about the modeling of SFDs is provided in this work. The critical aspects of these components and their modeling are highlighted and discussed.