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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

ALS liquid hydrogen turbopump: Advanced Development Program

The point of departure (POD) turbopump concept was reviewed and finalized. The basis for the POD was the configuration presented in the Aerojet proposal. After reviewing this proposal concept, several modifications were made. These modifications include the following: (1) the dual pump discharge arrangement was changed to a single discharge; (2) commonality of the turbine inlet manifold with the advanced launch system (ALS) liquid oxygen (LOX) TPA was dropped for this program; (3) the turbine housing flange arrangement was improved by relocating it away from the first stage nozzles; (4) a ten percent margin (five percent diameter increase) was built into the impeller design to ensure meeting the required discharge pressure without the need for increasing speed; (5) a ten percent turbine power margin was imposed which is to be obtained by increasing turbine inlet pressure if required; and (6) the backup concept, as an alternative to the use of cast impellers, now incorporates forged/machined shrouded impellers, rather than the unshrouded type originally planned.

Shimp, Nancy R.↗
NASA NTRS1990

Computation of Space Shuttle high-pressure cryogenic turbopump ball bearing two-phase coolant flow

A homogeneous two-phase fluid flow model, implemented in a three-dimensional Navier-Stokes solver using computational fluid dynamics methodology is described. The application of the model to the analysis of the pump-end bearing coolant flow of the high-pressure oxygen turbopump of the Space Shuttle main engine is studied. Results indicate large boiling zones and hot spots near the ball/race contact points. The extent of the phase change of the liquid oxygen coolant flow due to the frictional and viscous heat fluxes near the contact areas has been investigated for the given inlet conditions of the coolant.

Chen, Yen-Sen↗
NASA NTRS1989

Teflon lubrication of liquid oxygen turbopump bearings

Ball bearings with glass fiber reinforced Teflon ball retainers from hot-fired liquid oxygen turbopumps were analyzed by X-ray photoelectron spectroscopy to determine the extent of Teflon transfer and/or chemical reaction at the bearing surface. No Teflon, but metal fluorides could be found on the metal surface. This indicates that Teflon decomposes and reacts with the bearing steel to form fluorides. Hence, Teflon does not appear to function directly as a lubricant under these operating conditions.

Naerheim, Y.↗
NASA NTRS1990

A model for the Space Shuttle Main Engine High Pressure Oxidizer Turbopump shaft seal system

A model of the High Pressure Oxidizer Turbopump (HPOTP) shaft seal system on the Space Shuttle Main Engine (SSME) is described. The model predicts the fluid properties and flow rates throughout this system for a number of conditions simulating failed seals. The results agree well with qualitative expectations and redline values but cannot be verified with actual data due to the lack thereof. The results indicate that each failure mode results in a unique distribution of properties throughout the seal system and can therefore be individually identified given the proper instrumentation. Furthermore, the detection process can be built on the principle of qualitative reasoning without the use of exact fluid property values. A simplified implementation of the model which does not include the slinger/labyrinth seal combination has been developed and will be useful for inclusion in a real-time diagnostic system.

Paxson, Daniel E.↗
NASA NTRS1991

A feasibility study on the use of foil bearings in cryogenic turbopumps

The feasibility of using foil bearings in future earth-to-orbit rocket engines is studied. A design parameter of a LOX pump of the SSME was selected as a prototype for this study. It was found that three-pad journal bearings and eight-pad thrust bearings met the operating requirements of the LOX turbopump.

Heshmat, Hooshang↗
NASA NTRS1991

Developing acceptance limits for measured bearing wear of the Space Shuttle Main Engine high pressure oxidizer turbopump

The probabilistic design approach currently receiving attention for structural failure modes has been adapted for obtaining measured bearing wear limits in the Space Shuttle Main Engine high-pressure oxidizer turbopump. With the development of the shaft microtravel measurements to determine bearing health, an acceptance limit was neeed that protects against all known faiure modes yet is not overly conservative. This acceptance criteria limit has been successfully determined using probabilistic descriptions of preflight hardware geometry, empirical bearing wear data, mission requirements, and measurement tool precision as an input for a Monte Carlo simulation. The result of the simulation is a frequency distribution of failures as a function of preflight acceptance limits. When the distribution is converted into a reliability curve, a conscious risk management decision is made concerning the acceptance limit.

Genge, Gary G.↗
NASA NTRS1991

High-frequency data observations from space shuttle main engine low pressure fuel turbopump discharge duct flex joint tripod failure investigation

Observations made by Marshall Space Flight Center (MSFC) engineers during their participation in the Space Shuttle Main Engine (SSME) low pressure fuel turbopump discharge duct flex joint tripod failure investigation are summarized. New signal processing techniques used by the Component Assessment Branch and the Induced Environments Branch during the failure investigation are described in detail. Moreover, nonlinear correlations between frequently encountered anomalous frequencies found in SSME dynamic data are discussed. A recommendation is made to continue low pressure fuel (LPF) duct testing through laboratory flow simulations and MSFC-managed technology test bed SSME testing.

Zoladz, T. F.↗
NASA NTRS1991

An SSME high pressure oxidizer turbopump diagnostic system using G2(TM) real-time expert system

An expert system which diagnoses various seal leakage faults in the High Pressure Oxidizer Turbopump of the SSME was developed using G2(TM) real-time expert system. Three major functions of the software were implemented: model-based data generation, real-time expert system reasoning, and real-time input/output communication. This system is proposed as one module of a complete diagnostic system for Space Shuttle Main Engine. Diagnosis of a fault is defined as the determination of its type, severity, and likelihood. Since fault diagnosis is often accomplished through the use of heuristic human knowledge, an expert system based approach was adopted as a paradigm to develop this diagnostic system. To implement this approach, a software shell which can be easily programmed to emulate the human decision process, the G2 Real-Time Expert System, was selected. Lessons learned from this implementation are discussed.

Guo, Ten-Huei↗
NASA NTRS1992

Wear mechanisms found in angular contact ball bearings of the SSME's LOX turbopump

Extensive experimental investigations were carried out on used flight bearings of the Phase 2 high-pressure oxygen turbopump (HPOTP) of the Space Shuttle Main Engine (SSME) in order to determine the wear mechanisms, dominant wear modes, and their extent and causes. The report shows methodology, surface analysis techniques used, result, and discussion. The mode largely responsible for heavy bearing wear in LOX was identified as adhesive/shear peeling of the upper layers of bearing balls and rings. The mode relies on the mechanisms of scale formation, breakdown, and removal, all of which are greatly enhanced by the heavy oxidation environment of the HPOTP. Major causes of the high wear in bearings appear to be lubrication and cooling, both inadequate for the imposed conditions of operation. Numerous illustrations and evidence are given.

Chase, T. J.↗
NASA NTRS1991

Material and tribological considerations for turbopump bearings

The frictional heat generation in the rolling/sliding contact areas of high pressure oxygen turbopump (HPOTP) bearings is a key factor in bearing life. Several bulk materials, surface treatments and coatings are examined for their attributes of rolling contact fatigue life, wear and friction. Emphasis is given to the frictional response of these materials under conditions of rolling with incipient sliding as predicted from HPOTP bearing analysis. Rolling contact fatigue life is shown to be significantly improved with silicon nitride. Fatigue life can also be improved by coating the chromium carbide-laden stainless steels (440C, BG42) with TiN and thin dense chrome. The traction (friction under rolling/sliding) of these materials is discussed in terms of microslip and the presence of interfacial films.

Wedeven, L. D.↗
NASA NTRS1991

Probabilistic simulation of fragment dynamics and their surface impacts in the SSME turbopump

Numerical simulations are used to model the dynamics of solid fragments in the high-pressure fuel turbopump of the Space Shuttle Main Engine (SSME HPFTP). The simulations are conducted in a probabilistic structure in order to simulate the variance in the geometrical configuration, material properties and initial conditions of the solid fragments. The results of the particle dynamics simulations are presented in the form of the probability of surface impacts, and probability distributions of the impacting velocity and impingement angle.

Hamed, A.↗
NASA NTRS1992

Material compatibility evaluation for liquid oxygen turbopump fluid foil bearings

Three series of tests were carried out on three polymer-coated Inconel substrate materials, Teflon S, polyimide bonded graphite fluoride (PBGF), and Teflon, which are considered for use in fluid foil bearings for a liquid oxygen turbopump. All the candidate materials passed the liquid oxygen frictional heating test. During the gaseous oxygen frictional heating test, all coatings wore off before ignition occured. Both Teflon S and PBGF coated foils passed 100 start/stop cycles against chrome-plated Inconel 718 shaft in the direct foil bearing lift-off simulation test in liquid oxygen.

Stoltzfus, J. M.↗
NASA NTRS1992

Simulation of cryogenic turbopump annular seals

The goal of the current work is to develop software that can accurately predict the dynamic coefficients, forces, leakage and horsepower loss for annular seals which have a potential for affecting the rotordynamic behavior of the pumps. The fruit of last year's research was the computer code SEALPAL which included capabilities for linear tapered geometry, Moody friction factor and inlet pre-swirl. This code produced results which in most cases compared very well with check cases presented in the literature. TAMUSEAL Icode, which was written to improve SEALPAL by correcting a bug and by adding more accurate integration algorithms and additional capabilities, was then used to predict dynamic coefficients and leakage for the NASA/Pratt and Whitney Alternate Turbopump Development (ATD) LOX Pump's seal.

Palazzolo, Alan B.↗
NASA NTRS1993

Computation of incompressible viscous flows through turbopump components

Flow through pump components, such as an inducer and an impeller, is efficiently simulated by solving the incompressible Navier-Stokes equations. The solution method is based on the pseudocompressibility approach and uses an implicit-upwind differencing scheme together with the Gauss-Seidel line relaxation method. the equations are solved in steadily rotating reference frames and the centrifugal force and the Coriolis force are added to the equation of motion. Current computations use a one-equation Baldwin-Barth turbulence model which is derived from a simplified form of the standard k-epsilon model equations. The resulting computer code is applied to the flow analysis inside a generic rocket engine pump inducer, a fuel pump impeller, and SSME high pressure fuel turbopump impeller. Numerical results of inducer flow are compared with experimental measurements. In the fuel pump impeller, the effect of downstream boundary conditions is investigated. Flow analyses at 80 percent, 100 percent, and 120 percent of design conditions are presented.

Kiris, Cetin↗
NASA NTRS1991

An SSME High Pressure Oxidizer Turbopump diagnostic system using G2 real-time expert system

An expert system which diagnoses various seal leakage faults in the High Pressure Oxidizer Turbopump of the SSME was developed using G2 real-time expert system. Three major functions of the software were implemented: model-based data generation, real-time expert system reasoning, and real-time input/output communication. This system is proposed as one module of a complete diagnostic system for the SSME. Diagnosis of a fault is defined as the determination of its type, severity, and likelihood. Since fault diagnosis is often accomplished through the use of heuristic human knowledge, an expert system based approach has been adopted as a paradigm to develop this diagnostic system. To implement this approach, a software shell which can be easily programmed to emulate the human decision process, the G2 Real-Time Expert System, was selected. Lessons learned from this implementation are discussed.

Guo, Ten-Huei↗
NASA NTRS1993

Wear modes active in angular contact ball bearings operating in liquid oxygen environment of the Space Shuttle turbopumps

Extensive experimental investigation has been carried out on used flight bearings of the high pressure oxidizer turbopumps (HPOTP) of the space shuttle main engine (SSME) in order to determine the dominant wear modes, their extent, and causes. The paper presents the methodology, various surface analysis techniques used, results, and discussion. The mode largely responsible for premature bearing wear has been identified as adhesive/shear peeling of the upper layers of bearing balls and rings. This mode relies upon the mechanisms of scale formation, breakdown, and removal, all of which are greatly enhanced by the heavy oxidation environment of the HPOTP. Major causes of the high wear rates appear to be lubrication and cooling, both inadequate for the imposed conditions of operation. Numerous illustrations and evidence are provided.

Chase, Thaddeus J.↗
NASA NTRS1993

Probabilistic simulation of fragment dynamics and their surface impacts in the SSME turbopump

Numerical simulations are used to model the dynamics of solid fragments in the high pressure fuel turbopump of the space shuttle main engine (SSME HPFTP). The simulations are conducted in a probabilistic structure in order to simulate the variance in the geometrical configuration, material properties and initial conditions of the solid fragments. The results of the particle dynamics simulations are presented in the form of the probability of surface impacts, and probability distributions of the impacting velocity and impingement angle.

Hamed, A.↗
NASA NTRS1993

Anomaly detection of turbopump vibration in Space Shuttle Main Engine using statistics and neural networks

The statistical and neural networks methods have been applied to investigate the feasibility in detecting anomalies in turbopump vibration of SSME. The anomalies are detected based on the amplitude of peaks of fundamental and harmonic frequencies in the power spectral density. These data are reduced to the proper format from sensor data measured by strain gauges and accelerometers. Both methods are feasible to detect the vibration anomalies. The statistical method requires sufficient data points to establish a reasonable statistical distribution data bank. This method is applicable for on-line operation. The neural networks method also needs to have enough data basis to train the neural networks. The testing procedure can be utilized at any time so long as the characteristics of components remain unchanged.

Lo, C. F.↗