This document presents the computer analytical program developed as part of the gas-lubricated foil bearing design and development study conducted by AiResearch Manufacturing Co., under Contract F33615-73-C-2058. The report contains a detailed discussion of the computer program and includes sample problems and program listings. (Author).

This document presents the computer analytical program developed as part of the gas-lubricated foil bearing design and development study conducted by AiResearch Manufacturing Co., under Contract F33615-73-C-2058. The report contains a detailed discussion of the computer program and includes sample problems and program listings. (Author).

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.

An investigation of air-lubricated foil bearing technology for application in advanced propulsion and power systems was performed. The work conducted under the program comprised: (a) establishment and documentation of the state-of-the-art of foil bearings, (b) development of analytical tools and design guides to permit calculation of the performance of bending-dominated foil bearings, (c) investigation of potential substrate and coating materials, as well as conduct of start-stop and high speed rub tests with two air-lubricated foil bearings at 1000 deg F, (d) preparation of a layout drawing of a dynamic simulator test vehicle based upon an advanced engine (1980 or later time frame) in the 1000 to 3000 pounds thrust class, as well as a description of the test facility requirements, (e) description of the technology segments of air-lubricated foil bearings that need to be advanced to meet the requirements of the advanced engine application, and definition of the parameters for a long range test effort. (Modified author abstract).

Oil lubricated bearings have been widely used in variety of turbo machinery, though it has its own limitations such as thermal degradation of oil over temperature, complicated oil lubrication system and their maintenance. Commercial application of the air foil bearing (AFB) in Microturbomachinery have been acknowledged. Microturbomachinery term is used in applications with shaft power less than 1000KW and shaft diameter less than 100mm. Microturbomachinery has demanded light weighted, compact, extreme temperature and high speed operation. DN number for oil lubricated bearings and rolling element bearings is very less when compared to foil bearings. Absence of external pressurizing and lubricating system makes the system light and compact. Simple construction, low friction drag and reliability at high speed operations are few more advantages of the foil bearings. With all these advantages, foil bearings appears to be the one of the most effective techniques for Microturbomachinery. With the relentless demand for machines capable of operating at greatest speeds, high power densities and temperatures, foil gas bearings represent an enabling technology for advanced oil free system. While air foil journal bearings have been advanced significantly in past decades, very few literature data are available and not much experimental work has been conducted on foil thrust bearings. There is comparatively less information on air foil thrust bearings due to challenges in design, manufacturing and assembly. This research focuses on development of foil gas thrust bearing test rig which will operate at high temperature and speed. The test rig developed is equipped with thermocouple, optical probe, load cell which provides temperature, axial load, torque and high speed data by using NI labview. Design, manufacturing and assembly of air foil thrust bearing are detailed. The test rig has a push/pull mechanism which makes the stiffness measurement much easier. By evaluating parameters such as load capacity, steady state temperature, structural stiffness, and start stop friction torque will help to enhance the performance of the air foil thrust bearing.