The performance and durability of advanced, high temperature foil air bearings are evaluated under a wide range (10-50 kPa) of loads at temperatures from 25 to 650 deg C. The bearings are made from uncoated nickel based superalloy foils. The foil surface experiences sliding contact with the shaft during initial start/stop operation. To reduce friction and wear, the solid lubricant coating, PS 304, is applied to the shaft by plasma spraying. PS304 is a NiCr based Cr2O3 coating with silver and barium fluoride/calcium fluoride solid lubricant additions. The results show that the bearings provide lives well in excess of 30,000 cycles under all of the conditions tested. Several bearings exhibited lives in excess of 100,000 cycles. Wear is a linear function of the bearing load. The excellent performance measured in this study suggests that these bearings and the PS 304 coating are well suited for advanced high temperature, oil-free turbomachinery applications.

The performance and durability of advanced, high temperature foil air bearings are evaluated under a wide range (10-50 kPa) of loads at temperatures from 25 to 650 C. The bearings are made from uncoated nickel based superalloy foils. The foil surface experiences sliding contact with the shaft during initial start/stop operation. To reduce friction and wear, the solid lubricant coating, PS304, is applied to the shaft by plasma spraying. PS304, is a NiCr based Cr2O3 coating with silver and barium fluoride/calcium fluoride solid lubricant additions. The results show that the bearings provide lives well in excess of 30,000 cycles under all of the conditions tested. Several bearings exhibited lives in excess of 100,000 cycles. Wear is a linear function of the bearing load. The excellent performance measured in this study suggests that these bearings and the PS304 coating are well suited for advanced high temperature, oil-free turbomachinery applications. DellaCorte, C. and Valco, M. J. and Radil, K. C. and Heshmat, H. Glenn Research Center NASA/TM-1999-209187, NAS 1.15:209187, E-11697

The future market forces and environmental considerations in the passenger car and commercial vehicle sector mean more stringent engine downsizing is far more prevalent. Therefore, novel systems are required to provide boosting solutions including hybrid, electric-motor and exhaust waste energy recovery systems for high efficiency, response, reliability, durability and compactness. The current emission legislations and environmental trends for reducing CO2 and fuel consumption are the major market forces in the land and marine transport industries. The internal combustion engine is the key product and downsizing, efficiency and economy are the driving forces for development for both spark ignition (SI) and compression ignition (CI) engines in both markets. Future market forces and environmental considerations for transportation, specifically in the passenger car, commercial vehicle and the marine sectors mean more stringent engine downsizing. This international conference is the latest in the highly successful and prestigious series held regularly since 1978. These proceedings from the Institution's highly successful and prestigious series address current and novel aspects of turbocharging systems design, boosting solutions for engine downsizing and improvements in efficiency, and present the latest research and development in this growing and innovative area. - Focuses on boosting solutions including hybrid, electric-motor and exhaust waste energy recovery systems - Explores the current need for high efficiency, reliability, durability and compactness in recovery systems - Examines what new systems developments are underway

Foil air bearing load capacity tests were conducted to investigate if a solid lubricant coating applied to the surface of the bearing's top foil can function as a break-in coating. Two foil coating materials, a conventional soft polymer film (polyimide) and a hard ceramic (alumina), were independently evaluated against as-ground and worn (run-in) journals coated with NASA PS304, a high-temperature solid lubricant composite coating. The foil coatings were evaluated at journal rotational speeds of 30000 rpm and at 25 deg C. Tests were also performed on a foil bearing with a bare (uncoated) nickel-based superalloy top foil to establish a baseline for comparison. The test results indicate that the presence of a top foil solid lubricant coating is effective at increasing the load capacity performance of the foil bearing. Compared to the uncoated baseline, the addition of the soft polymer coating on the top foil increased the bearing load coefficient by 120 percent when operating against an as-ground journal surface and 85 percent against a run-in journal surface. The alumina coating increased the load coefficient by 40 percent against the as-ground journal but did not have any affect when the bearing was operated with the run-in journal. The results suggest that the addition of solid lubricant films provide added lubrication when the air film is marginal indicating that as the load capacity is approached foil air bearings transition from hydrodynamic to mixed and boundary lubrication.