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This work details the heat generation analysis of a turbine aero-engine main-shaft bearing using the computer program Advanced Dynamics Of Rolling Elements (ADORE). The empirical models used for traction and churning heat generation are detailed. The predictions of ADORE are shown to demonstrate the differing contributions of traction and churning to total heat generation at different load/speed regimes. These results are then compared with experimental results. In addition, the results of ADORE are also compared with results from the well-known bearing analysis program SHABERTH (Shaft Bearing Thermal Analysis). The comparisons showed good agreement between ADORE and the experimental results for loads between 13.35 and 53.40 kN and speeds between 1.8 and 2.2 MDN. The results also showed under prediction of heat generation by SHABERTH in this regime. Limitations of both programs were identified and speculated to include limitations in the empirical models due to the lack of available experimental traction data at high speeds/loads. Finally, recommendations for future research are provided which will likely provide significant improvements in the ability to predict bearing heat generation in turbine aero-engine applications.

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Wright Patterson AFB OH 45433133 mm bore ball bearings with metal rolling elements were tested at the following conditions: speeds from 1.5 × 10 6 to 2.6 × 10 6 DN; thrust loads from 13,350 to 53,400 N; oil delivery temperatures from 66 to 121 • C; and oil flow rates from 7.3 to 11.4 L/min. The resulting bearing outer race temperature, oil exit temperature, and power loss determined from the shaft torque and power loss determined from the oil temperature rise are reported. Experimental power loss values are compared to the analytical results obtained with the computer code SHABERTH.The experimental data are also fitted to an empirical equation to predict the total bearing power loss. The results indicate that bearing operating temperature is a challenge for next-generation engines, primarily driven by limits of polyolester lubricants used in gas turbine engines. The results also indicate that the computer code SHABERTH underpredicts the bearing lower loss at high load conditions. A new empirical model was able to reasonably predict the bearing power loss over the conditions studied.

In this paper, the authors present the results of recent developments demonstrating that ultra-high temperature compliant foil bearings are suitable for application in a wide range of high temperature turbomachinery including gas turbine engines, supercritical CO2 power turbines and automotive turbochargers as supported by test data showing operation of foil bearings at temperatures to 870°C (1600°F). This work represents the culmination of efforts begun in 1987, when the U.S. Air Force established and led the government and industry collaborative Integrated High Performance Turbine Engine Technology (IHPTET) program. The stated goal of IHPTET was to deliver twice the propulsion capability of turbine engines in existence at that time. Following IHPTET, the Versatile Affordable Advanced Turbine Engines (VAATE) program further expanded on the original goals by including both versatility and affordability as key elements in advancing turbine engine technology. Achieving the stated performance goals would require significantly more extreme operating conditions including higher temperatures, pressures and speeds, which in turn would require bearings capable of sustaining temperatures in excess of 815°C (1500°F). Similarly, demands for more efficient automotive engines and power plants are subjecting the bearings in turbochargers and turbogenerators to more severe environments. Through the IHPTET and VAATE programs, the U.S. has made considerable research investments to advancing bearing technology, including active magnetic bearings, solid and vapor phase lubricated rolling element bearings, ceramic/hybrid ceramic bearings, powder lubricated bearings and compliant foil gas bearings. Thirty years after the IHPTET component goal of developing a bearing capable of sustained operation at temperatures above 540°C and potentially as high as 815°C (1500°F) recent testing has demonstrated achievement of this goal with an advanced, ultra-high temperature compliant foilgas bearing. Achieving this goal required a combination of high temperature foil material, a unique elastic-tribo-thermal barrier coating (KOROLON 2250) and a self-adapting compliant configuration. The authors describe the experimental hardware designs and design considerations of the two differently sized test rigs used to demonstrate foil bearings operating above 815°C (1500°F). Finally, the authors present and discuss the results of testing at temperatures to 870°C (1600°F).