Measurement and Prediction of the Static Operating Conditions of a Large Turbine Tilting-Pad Bearing Under High Circumferential Speeds and Heavy Loads

Abstract

The identification results for the static performance characteristics of a large tilting-pad bearing in load between pad configuration are presented for specific bearing loads between 1.0 and 2.5 MPa and for circumferential speeds up to 79 m/s. The bearing is lubricated by spray-bars and can be described by the following specifications: Five pads, 0.23 nominal preload, 60% offset, 56° pad arc angle, 500 mm inner diameter, 350 mm pad length and 1.28 per mille relative bearing clearance. The axial oil flow is reduced by a fixed seal on both bearing edges which has a nominal radial clearance of 1 mm. The film pressure and the gap width are determined in the whole area of the sliding surface by an axial shift of the shaft. The bearing temperatures are measured by means of 100 thermocouples located 5 mm behind the sliding surface. The experimental results indicate that significant pad deformation occurs in circumferential and in axial direction. Also the effective supply temperatures are much higher than the nominal ones. According to the lubricant flow the sensor temperatures close to the spray-bars at the sliding surface rise about 20 K for 7 l/s and 40 K for 3.5 l/s at 3000 rpm. The temperatures are nearly constant between all pads and depend only on speed and not on load. The theoretical analyses of the bearing performance was accomplished with the bearing calculation software COMBROS. This code models the transition between laminar and turbulent flow and solves an extended Reynolds equation, the three dimensional energy equation of the film and the heat conduction equations of the shaft and the pads considering various boundary conditions due to the judgment of the user. Concerning the minimum film thickness, the maximum temperature on the sliding surface and the maximum film pressure only poor agreement was reached if the influence of the axial pad deformation was neglected. In advanced analyses a co-simulation between COMBROS and a structural mechanics software shows that an improvement of the prediction was achieved. The comparison of the measurement data and the advanced simulation shows very good agreement for the characteristic bearing parameters as well as for the local distributions of film pressure, temperature and film thickness in the whole operating range of the bearing. Further, the applied inlet mixing model for the lubricant supply process proves to be very suitable.

Predictions for run-up procedures of automotive turbochargers with full-floating ring bearings including thermal effects and different bearing setups

“…The numerical procedure used to determine the content of the look-up tables is more comprehensively described in [18] and [19]. Optionally the friction forces can be added to this table and used to predict the ring speed in the rotordynamic analysis.…”

The Impact of Convective Fluid Inertia Forces on Operation of Tilting-Pad Journal Bearings

“…Experimental evidence for the presence of the pressure rise at the leading edge exists within measurement results for both bearings introduced in Table 1. The test rig introduced in [5,6,16] is able to measure a pressure and film thickness distribution within the whole film by a lateral movement of the shaft. Two capacitive proximity probes and two piezoelectric pressure sensors are mounted in the shaft rotated 90 ∘ to each other.…”

“…Due to the high rotor speed, the temperature distributions in the journal are assumed to be 2D as the temperature does not vary in circumferential direction. The foundation of the entire bearing model used for the upcoming analyses is comprehensively described in [4][5][6]. Therefore, the consecutive explanations are reduced due to their relevance for the particular investigations performed here.…”

“…References [11][12][13] provide a description of the test rig that the bearing is investigated with. The second bearing is a flooded lubricated five-pad bearing for large turbine applications already investigated in [4][5][6] and shown in Figure 3. The bearing features an elliptical contact between pads and liner with a pivot offset of 0.6.…”

A Theoretical Study on Frequency Effects on Tilting-Pad Journal Bearing Dynamic Coefficients

“…The theoretical analysis is based on the code COMBROS R presented earlier in [10][11][12]. The code is based on the solution of a generalized Reynolds Equation and a three dimensional thermal bearing model including shaft, film and pads.…”