Another form of lubrication is the 'elastohydrodynamic' lubrication. Note that the hydrodynamic pressure has no relationship at all to the engine oil pressure, except that if there is insufficient engine oil pressure to deliver the required copious volume of oil into the bearing, the hydrodynamic pressure mechanism will fail and the bearing(s) and journal(s) will be quickly destroyed.
Still further, the stiffness and damping coefficients of the dampers 71 can be selectively varied and controlled by changing the metal mesh material, geometry and mesh density depending upon the operating conditions encountered in the bearing chamber 56 tilting pad thrust bearing during rotation of the shaft 55. The metal mesh dampers 71 also provide maximum damping at lower frequency ranges, wherein rotordynamic instability frequencies are significantly lower than the rotor synchronous frequency or shaft rotational frequency.
Often, a spring or resilient backing member is disposed between the foil and a stationary member (otherwise referred to as a cartridge, retainer or base) to accommodate deflections of the foil due to pressurization thereof for maintenance of optimum film layer geometry, thus providing support for the rotating member and foils against bearing loading and imbalances such as whirl and the like.

In another alternate embodiment for the bearing unit 49, the bearing 52 may be provided with a plurality of compliant structural dampers 54 on each bearing flange 66. More particularly, the annular flanges 66 may each be formed with pairs of circumferential mounting pockets or channels 98 and 99 which each receive a respective one of the dampers 54. These pockets 98 and 99 open radially outwardly about the circumference of the bearing flanges 66 but are axially closed on their inboard and outboard ends by side faces like side faces 86 and 87 described above.
1. The fluid ports 56 of the ring assembly pass fluid directly to the squeeze film 61 through the annular stationary ring assembly 50. Just inside of the squeeze film cylinder are two annular fluid plenums 64 that receive fluid from fluid ports 62. Fluid in these plenums is contained by seals 66 and 68 that seat between the squeeze film cylinder and the spring support 20. These fluid plenums provide a reservoir of fluid that is supplied to a thin oil film 80 surrounding the journal bearing through fluid ports 70 in the spring support and the bearing sleeve.
The non-rotating journal bearing 2 has a pair of annular flanges 8 that support the journal bearing and attach to the bearing spring support 20. These flanges have a circular array of bolt holes 10 that align with a corresponding array of bolt holes 22 in the spring support.

A turbocharger 51 is provided with an improved bearing 52, which may be formed as a semi-floating as a semi-floating ring journal bearing which has hydrodynamic tilting pads 53 on the inner diameter thereof and compliant structural dampers 54 on the outer diameter thereof.
In view of this the bearing is designed so that when the two halves of the housing are correctly bolted together its parting line surfaces adjoin and the bearing correctly conforms to the housing, leaving the required running clearance between its working surface and the journal.

Such interface comprises a spheroidal joint (also called ball and socket joint) 42 between the respective bearing pad 15 and the bearing housing 11. More in particular the spheroidal joint 41 is provided between the respective bearing pad 15 and the parallelepiped block which comprises the first interface 21. To dampen radial movements caused by shaft rotation, a lubricating fluid such as oil is supplied to the bearing chamber 56 through appropriate supply ports, wherein the oil is able to flow into the radial spaces defined between the bearing 52 and chamber surface 58 on the outside and between the bearing 52 and shaft surface 59 on the inside.
The opposite ends of the bearing 52 include annular bearing flanges 66 which define outer bearing surfaces 67 and 68 which face toward the chamber surface 58. The outer bearing surfaces 67 and 68 are spaced inwardly from the chamber surface 58 a small radial extent to define radial spaces 69 and 70. As will be described further herein, each of the radial spaces 69 and 70 is provided with a compliant structural damper 54.
It was theoretically shown that it is possible to change the dynamic coefficients of multirecess journal bearings with a suitable choice of a PD controller, and in the plane rotor-bearing stability analysis, based on root locus method, it was shown that it is possible to increase the damping ratio of the under damped mode.

The bearing stiffness and damping coefficients are used in rotor dynamic calculations for unbalance and random vibration responses, for determining damped critical speeds, for rotor stability analysis, and for general design and optimization purposes.