Waldemar Dmochowski

Performance of a Hydrodynamic Fixed Geometry Thrust Bearing: Comparison between Experimental Data and Numerical Results

The objective of this study is to analyze the performance of a hydrodynamic thrust bearing with eight fixed pads. A comparison between experimental data and numerical results obtained by a thermohydrodynamic model is presented. The influence of the oil supply temperature, the applied load, and the rotational speed on the thrust bearing performance characteristics such as temperature field, minimum film thickness, leakage flow, and power loss is analyzed and discussed. The agreement between the experimental and numerical results is generally satisfactory.

Numerical Study of the Sensitivity of Tilting Pad Journal Bearing Performance Characteristics to Manufacturing Tolerances: Steady-State Analysis

The bearing selection for rotating machinery is based on predictions obtained for nominal dimensions. Very often the experienced performance is different than that expected. In this paper the authors theoretically analyze the possible effects of deviations from the nominal parameters of tilting-pad journal bearings on their operating characteristics. Using an example of five-pad tilting-pad journal bearings, the effects of realistic variations of pad and bearing clearances, pivot angular position, and pad angular extent have been evaluated theoretically for bearings with different diameters and L/D ratios. The characteristics analyzed in this study include operating temperatures, friction loss, minimum film thickness, and pressure.

A Comparison Study Between Acoustic Sensors for Bearing Fault Detection Under Different Speed and Load Using a Variety of Signal Processing Techniques

The use of ultrasonic sensor technology to detect incipient and evolving defects in rotating components such as bearings and gears is more desirable due to their high resolution. In a previous study, the sensitivity of a variety of sensors including an air-coupled ultrasound transducer to bearing faults was analyzed and thoroughly discussed. This article investigates the effectiveness of two ultrasonic sensors, namely, air-coupled and piezoelectric ultrasound transducers for rolling element bearings damage diagnostics. The former is a noncontact sensor and the latter is a contact sensor. An accelerometer was also used as the baseline sensor for comparison purposes. A series of tests was carried out on a laboratory test rig running with defective and undamaged healthy bearings under variable shaft speeds and several radial loads. The data were analyzed using selected signal processing techniques covering time, frequency, and advanced joint time–frequency domains. The results showed that certain acoustic features were responsive to the variation of operational condition and the damage; the detection capability of the sensors varied depending on the defect size, its location, as well as the applied signal analysis technique.

Dynamic Testing of the Tilting Pad Journal Bearing

A method of selective vibration orbits has been used to dynamically test a 0.076 m (3 in) diameter, five shoe tilting pad journal bearing that has different values of preload and L/d ratio. The experimentally obtained stiffness and damping coefficients are discussed, with particular reference to the effect on these coefficients of increasing preload as a result of enlarging the pad clearance. The paper presents an uncertainty analysis of the experimental results, and compares these results with theoretical data obtained from a thermo-hydrodynamic model of the bearing. Presented at the 48th Annual Meeting in Calgary, Alberta, Canada May 17–20, 1993

Experimental Evaluation of Abradable Seal Performance at High Temperature

Abradable seals have been used in aero-engines and land-based gas turbines for more than three decades. They are applied to various sections of the engine in order to reduce gas leakage by optimizing the gap between rotating and stationary parts. This optimization represents a significant increase in efficiency and decrease in fuel consumption. Performance evaluation of any abradable seal includes measurement of its mechanical properties, abradability tests and (ultimately) tests in engines. The aim of this paper is to study the effect of temperature on the rub performance of abradable seals. A series of experiments has been carried out in order to evaluate a commercially available seal material at different operating conditions. The effect of operating temperature on contact force, abrasion scar appearance and blade wear is examined and analyzed. A microstructural analysis of the rub scar has also been performed.Copyright

Sensitivity of air-coupled ultrasound and eddy current sensors to bearing fault detection

For decades, vibration and oil analysis have usually been used to detect early bearing faults and track their progression over time. Progress has been seen in condition monitoring through vibration analysis of rolling element bearings using improved sensors and advanced signal processing techniques. In this paper, the authors investigate the use of air-coupled ultrasound and eddy current sensors as diagnostic tools for the detection of bearing faults. A series of experiments was carried out in a laboratory environment: localized defects with different sizes were created intentionally on the test bearing components simulating evolving cracks or other related faults. The resulting data for a constant bearing speed and load have shown that both sensors are capable of detecting different types of defects located on the bearing components. The data from the air-coupled ultrasound and eddy current sensors were also compared with those obtained from an accelerometer. The test method and the processing technique are described and the spectra of the different signals are analyzed and discussed.

The Effect of Lubricant Viscosity-Temperature Characteristics on the Performance of Plain Journal Bearings

Experimental and analytical results of bearing friction loss, operating temperature, and oil gap thickness are presented comparing performance characteristics of bearings operating with the different lubricants. The lubricants were blended using a variety of mineral and synthetic base stocks to achieve a range of viscosity-temperature characteristics. The results show that the test bearings running with higher viscosity index (VI) lubricants generated slightly lower bearing surface temperatures than those generated using a low VI lubricant. The high VI lubricant also reduced the total power losses by up to 10%. These gains are achieved with little or no change in the minimum oil film thickness.Copyright

An Investigation of the Steady-State Performance of a Pivoted Shoe Journal Bearing with ISO VG 32 and VG 68 Oils

This article presents a report on an investigation into the performance characteristics of a steadily loaded pivoted shoe journal (PSJ) bearing that is lubricated with ISO VG 32 and VG 68 oils. The article describes a testing machine on which the experimental investigation was performed. Measurements of shaft torque, pad temperature distributions, oil inlet and outlet temperatures, oil flow rate, and eccentricity have all been recorded as functions of load and speed. The experimental results from both test oils are presented in graphical form and are compared with theoretical predictions obtained from the authors computer model of the PSJ bearing. These results showed that the thicker ISO VG 68 oil provided thicker oil films. However, it also had higher bearing temperatures and power losses. A good correlation between the theoretical and experimental results has been found. Theoretical analysis of the bearing friction losses indicate that shear losses predominate and churning losses account for approximately 20% of the total losses.

Measured Temperature Characteristics of 152 mm Diameter Pivoted Shoe Journal Bearings with Flooded Lubrication

The steady-state performance characteristics of journal bearings sometimes impose limitations on the operation of high-speed rotating machinery. Such limitations in bearing performance might be the result of one or more of the following: inadequate load carrying capacity, unacceptably high operating temperatures, and inefficient component performance. Lowering operating temperatures helps to boost the bearings load and/or speed capability, and reducing bearing power loss and/or oil flow requirements improves machine efficiency. In response to the need to improve bearing performance, the authors have conducted extensive testing of the pivoted shoe journal (PSJ) bearing. This paper describes work from the first phase of the study, in which the effects of independent design and operating variables on the metal temperatures of flooded lubricated, PSJ bearings are examined experimentally. These variables include pivot location, load orientation, shaft speed, and bearing load. In conclusion, it is shown that some of the independent variables have a significant influence on bearing performance, after comparing pad temperature profiles, isotherms, and maximum temperatures. The study was performed on a rig that measures steady-state performance under light to moderately heavy unit loads, and comparatively high operating speeds. These conditions are representative of modern-day rotating machinery, particularly new turbine and compressor designs. Presented at the 56th Annual Meeting Orlando, Florida May 20–24, 2001

Experimental Evaluation of Foil Bearing Performance: Steady-State and Dynamic Results

An experimental facility dedicated to measuring both the steady-state and dynamic properties of foil bearings, under a variety of operating conditions, has been designed and commissioned. The bearing under test is placed at the midspan of a horizontal, simply-supported, stepped shaft which rotates at up to 60 krpm. Static and dynamic loads of up to 3500 N and 450 N (respectively) can be applied by means of a pneumatic cylinder and two electrodynamic shakers. This paper outlines the test procedures and data analysis methods pertaining to the operation of the high-speed, oil-free bearing test rig, and presents steady-state and dynamic results for a first-generation foil bearing. The test bearing, which was fabricated in-house, is 0.07 m diameter and has an aspect ratio of 1; bearing manufacturing details are provided.© 2009 ASME