Analysis of Tilting Pad Journal Bearings With Heat Transfer Effects

Abstract

An approximate solution technique for tilting pad journal bearings is presented. The method makes use of approximations to the axial pressure profile and the temperature profiles and includes heat transfer between the film and its boundaries. A second order profile is assumed to represent the temperature distribution across the film. The classical Reynolds equation is applied, using the viscosity based on the cross-film average of temperature. The transfer of heat in the pads is modeled as purely radial conduction, and the journal surface temperature is given by a circumferential average of the film temperatures. Results of calculations are presented for a sample case representative of an industrial compressor or turbine bearing and are compared to isothermal results. The dynamic characteristics in this case are found to vary by 10 to 35 percent for a change in lubricant inlet temperature of 28°C. Temperature distributions in the lubricant and on the surfaces of the pads are given.

A Review of Tilting Pad Bearing Theory

“…Then by back substitution of (34) into (32), the bearing coefficients are expressed in terms of the shaft degrees of freedom U s as…”

“…Knight and Barrett [32] presented a THD analysis of four pad tilting pad bearings with central pivots in a load on pad configuration. No turbulence model was considered in calculating the results.…”

Active tilting-pad journal bearings supporting flexible rotors: Part I – The hybrid lubrication

“…Lund [43], Lund and Thomsen [44], Springer [45] and Allaire et al [46], among others, have provided a way of calculating the frequency dependence synchronously reduced as well as the full bearing force coefficients; the latter by including the pad dofs in the perturbation analysis thus eliminating the frequency dependence. Alongside the computational development these first isothermal models incorporated thermal and compliance effects in a more accurate model for conventional TPJB, the elasto-thermohydrodynamic (ETHD) model [43,46,47,48,49,50]. Regarding the active TPJBs, the initial isothermal modelling proposed by Santos and Russo [15] has been extended by the subsequent contributions of Santos and Nicoletti [16] (THD) and Santos and Haugaard [17] (EHD) to finally bridge the gap between both approaches in the ETHD formulation with the works of Varela et al [18,19].…”

Active tilting-pad journal bearings supporting flexible rotors: Part II–The model-based feedback-controlled lubrication

“…before the whole rotating machine is manufactured, then a model-based approach becomes an attractive control design tool, allowing for an optimization of the whole electro-mechanical system dynamics. The accuracy in describing the dy-namic behavior of passive TPJBs [24,25,26,27,28,29] and active TPJBs connected to hydraulic servosystems [14,30,31,32,33] makes feasible today's model-based control design approaches. Regarding the active control of flexible rotors supported by fluid-film bearings, a theoretical study on full and reduced modal state controllers was presented in [34].…”