High pressure oxygen turbopump bearing cage stability analyses

The low service life of the high pressure oxygen turbopump (HPOTP) bearings used in the space shuttle main engine was examined by use of the Battelle "BASDAP' bearing computer stability model. The dynamic instability of the bearing cage resulted in excessive wear and eventual failure of the unit. By maintaining a cage/race clearance of no more than 0.25 millimeters (0.010 inches), ball/pocket clearance of no less than 0.54 millimeters (0.025 inches), dynamic balancing of the cages, and maintaining adequate lubricant films between the balls and races, cage instability and subsequent bearing degradation can be reduced

Cage stability analysis for SSME HPOTP bearings

A numerical model of cage motion (CAGEDYN) was used to analyze the stability of bearing cages in the Space Shuttle main engine (SSME) high pressure oxygen turbopump (HPOTP). The stability of existing bearing geometries, as well as perturbations of these geometries, was analyzed for various operating conditions. Results of the analyses show that some combinations of operating parameters, exacerbated by the sparse lubrication that exist in the HPOTP bearings, can cause unstable cage oscillations. Frequencies of cage oscillations were predicted by the CAGEDYN numerical model by Fourier analysis of predicted cage motions. Under conditions that cause unstable cage motion, high frequency oscillations were predicted that could cause premature cage failures

Adjunct Faculty Organizational Sense of Belonging and Affective Organizational Commitment

In recent years all public higher education institutions have increased their reliance on adjunct faculty. Adjuncts provide expertise in key areas, are available at times that meet the needs of the changing student demographic, and cover an increasing number of introductory courses. It has been suggested that adjunct faculty may be more weakly linked to their students, colleagues, and institution. This may, in turn, be detrimental to the organizational health of the institution. Prior research has indicated that adjunct faculty have different motivations and expectations from teaching that impact the connections they form in the higher education workplace. This study examined sense of belonging and organizational commitment among adjunct faculty at a public research university. The study also investigated the distribution of adjunct faculty types at the institution. The study was conducted using an online Survey of Workplace Relationships and included 292 adjunct and fulltime faculty participants. Self-report measures were used to gain demographic information and employment characteristics, and to place adjunct faculty in a pre-established typology. Individual subscales were used to obtain measures of Organizational Sense of Belonging (OSB) and Affective Organizational Commitment (AOC). A variety of methods were used to analyze the data, including descriptive analyses, ANCOVA, and Pearson Correlation. Results indicated that, at the institution being studied, adjunct faculty had a slightly weaker OSB than full-time faculty; and that development of OSB varies among the different types of adjunct faculty. Results indicated a statistically significant linear relationship between OSB and AOC. Further research is needed to clarify factors that contribute to the development of OSB in a higher education setting. Further research is also needed to determine causality in the OSB-AOC relationship

Evaluation of feasibility of measuring EHD film thickness associated with cryogenic fluids

The feasibility of measuring elastohydrodynamic (EHD) films as formed with a cryogenic (LN2) fluid is evaluated. Modifications were made to an existing twin disk EHD apparatus to allow for disk lubrication with liquid nitrogen. This disk apparatus is equipped with an X-ray system for measuring the thickness of any lubricant film that is formed between the disks. Several film thickness experiments were conducted with the apparatus which indicate that good lubrication films are filmed with LN2. In addition to the film thickness studies, failure analyses of three bearings were conducted. The HPOTP turbine end bearings had experienced axial loads of 36,000 to 44,000 N (8,000 to 10,000 lb). High continuous radial loads were also experienced, which were most likely caused by thermal growth of the inner race. The resulting high internal loads caused race spalling and ball wear to occur

The Importance Of Managing Psychosocial Health: A Case Study

Managing the physical aspects of lymphedema requires an individual to be committed to daily treatment of this chronic condition. Performing manual lymph drainage, using compression bandaging or compression garments, exercising, and caring for the skin all take time and a high level of dedication. This commitment to self-care can be emotionally and psychologically exhausting. When coupled with other emotional stressors in a patient’s life, successful treatment of lymphedema is challenging. We present a case demonstrating how the physical and psychological aspects of care interplay, and, when well-managed, can positively affect the outcome

Investigation of instability, dynamic forces, and effect of dynamic loading on strength of cages for the bearings in the high pressure oxygen turbopumps for the space shuttle main engine

Experiments were performed to determine the effect of cyclic loading on bearing cage strength. A long term working tensile load of approximately 1300 N (300 lbs) was found to be the likely maximum. Higher loads caused a decrease in cage tensile strength after the 125,000 cycle testing period. Poisson's ratio in compression was found to be highly dependent upon the direction of the fiberglass plies. At room temperature the value was 0.15 with the plies and 0.68 across the plies. At -196 C (-321 F), the value with the plies was 0.20. The results of the analyses conducted have again demonstrated the critical need for improved lubrication in the high pressure oxygen turbopump bearings. Lubricant films with low shear strength and low friction coefficients promote cage stability and decrease ball/cage forces during marginal operating conditions. The analysis of the effect of combined bearing loads on ball/cage loads has identified a radial load of 3600 N (800 lbs) as the maximum for the current clearance of the balls and cage pockets. Liquid oxygen impinging on the cage in the direction of rotation was found to enhance cage stability

Effect of forward motion on engine noise

Methods used to determine a procedure for correcting static engine data for the effects of forward motion are described. Data were analyzed from airplane flyover and static-engine tests with a JT8D-109 low-bypass-ratio turbofan engine installed on a DC-9-30, with a CF6-6D high-bypass-ratio turbofan engine installed on a DC-10-10, and with a JT9D-59A high-bypass-ratio turbofan engine installed on a DC-10-40. The observed differences between the static and the flyover data bases are discussed in terms of noise generation, convective amplification, atmospheric propagation, and engine installation. The results indicate that each noise source must be adjusted separately for forward-motion and installation effects and then projected to flight conditions as a function of source-path angle, directivity angle, and acoustic range relative to the microphones on the ground

Systematically Controlling for the Influence of Age, Sex, Hertz and Time Post-Whole-Body Vibration Exposure on Four Measures of Physical Performance in Community-Dwelling Older Adults: A Randomized Cross-Over Study

Though popular, there is little agreement on what whole-body vibration (WBV) parameters will optimize performance. This study aimed to clarify the effects of age, sex, hertz and time on four physical function indicators in community-dwelling older adults (N = 32). Participants were exposed to 2 min WBV per session at either 2 Hz or 26 Hz and outcome measures were recorded at 2, 20 and 40 min post-WBV. Timed get up-and-go and chair sit-and-reach performances improved post-WBV for both sexes, were significantly different between 2 Hz and 26 Hz treatments (P ≤ 0.05) and showed statistically significant interactions between age and gender (P ≤ 0.01). Counter movement jump and timed one-legged stance performances showed a similar but non-significant response to 2 Hz and 26 Hz treatments, though male subjects showed a distinct trended response. Age and gender should be statistically controlled and both 2 Hz and 26 Hz exert a treatment effect

Whole-Body Vibration Improves Functional Mobility, Flexibility, and Relative Risk for Falling in the Assisted Living Elderly: A Case Series

Study design: A randomized double blind repeated measures, case series study of whole body vibration (WBV) in the assisted living elderly. Background: A single exposure to WBV has been shown to have benefit with respect to muscle activity, strength, balance, and power in some studies while other studies have found no benefit. Its overall effectiveness is unknown due to the conflicting findings reported in the literature. Case description: Six subjects (5 female, 1 male; mean age = 85.4) in an assisted living community volunteered to participate. Subjects were exposed to a single bout of WBV at 0, 2, 20, and 26 Hz. Dependent variables including timed get up and go, chair sit and reach, one-legged stance time, and counter-movement jump were collected ten minutes prior, and two, twenty, forty, and sixty minutes after exposure. Published times for predicting falls using the timed up and go test and one-legged stance time were used to determine the number of outcome measures predicting falls prior to WBV. This was then compared to the number of outcome measures that predicted falls after exposure to determine any change. Outcomes: WBV had no statistically significant effect on mobility in the elderly. However, trends suggest mean timed get up and go may improve after 20 Hz and 26Hz. Mean chair sit and reach showed minimal improvement with time bilaterally following all frequencies of WBV. No trends were found for one-legged stance time and counter-movement jump. The fall risk assessment suggested improvements following 2 Hz of WBV, but findings were not significant. Conclusion: WBV had no significant effect on mobility in the assisted living elderly. Further research with larger sample size would be beneficial

Measurements of elastohydrodynamic film thickness, wear and tempering behavior of high pressure oxygen turbopump bearings

The reusable design of the Space Shuttle requires a target life of 7.5 hours for the turbopumps of the Space Shuttle main engine (SSME). This large increase from the few hundred seconds required in single-use rockets has caused various problems with the bearings of the turbopumps. The berings of the high pressure oxygen turbopump (HPOTP) were of particular concern because of wear, spalling, and cage failures at service time well below the required 7.5 hours. Lubrication and wear data were developed for the bearings. Since the HPOTP bearings operate in liquid oxygen, conventional liquid lubricants cannot be applied. Therefore, solid lubricant coatings and lubricant transfer from the polytetrafluorethylene (FTFE) cage were the primary lubrication approaches for the bearings. Measurements were made using liquid nitrogen in a rolling disk machine to determine whether usable elastohydrodynamic films could be generated to assist in the bearing lubrication