Engineering topics

Hochstein, J. I.

Publications and source records attributed to Hochstein, J. I..

13 records

NASA NTRS2006

Microgravity Geyser and Flow Field Prediction

Modeling and prediction of flow fields and geyser formation in microgravity cryogenic propellant tanks was investigated. A computational simulation was used to reproduce the test matrix of experimental results performed by other investigators, as well as to model the flows in a larger tank. An underprediction of geyser height by the model led to a sensitivity study to determine if variations in surface tension coefficient, contact angle, or jet pipe turbulence significantly influence the simulations. It was determined that computational geyser height is not sensitive to slight variations in any of these items. An existing empirical correlation based on dimensionless parameters was re-examined in an effort to improve the accuracy of geyser prediction. This resulted in the proposal for a re-formulation of two dimensionless parameters used in the correlation; the non-dimensional geyser height and the Bond number. It was concluded that the new non-dimensional geyser height shows little promise. Although further data will be required to make a definite judgement, the reformulation of the Bond number provided correlations that are more accurate and appear to be more general than the previously established correlation.

Hochstein, J. I.↗

NASA NTRS1993

Influence of heat transfer rates on pressurization of liquid/slush hydrogen propellant tanks

A multi-dimensional computational model of the pressurization process in liquid/slush hydrogen tank is developed and used to study the influence of heat flux rates at the ullage boundaries on the process. The new model computes these rates and performs an energy balance for the tank wall whereas previous multi-dimensional models required a priori specification of the boundary heat flux rates. Analyses of both liquid hydrogen and slush hydrogen pressurization were performed to expose differences between the two processes. Graphical displays are presented to establish the dependence of pressurization time, pressurant mass required, and other parameters of interest on ullage boundary heat flux rates and pressurant mass flow rate. Detailed velocity fields and temperature distributions are presented for selected cases to further illuminate the details of the pressurization process. It is demonstrated that ullage boundary heat flux rates do significantly effect the pressurization process and that minimizing heat loss from the ullage and maximizing pressurant flow rate minimizes the mass of pressurant gas required to pressurize the tank. It is further demonstrated that proper dimensionless scaling of pressure and time permit all the pressure histories examined during this study to be displayed as a single curve.

Sasmal, G. P.↗

NASA NTRS1992

Experimental verification of scaling parameters for thermal stratification

A study to determine important dimensionless parameters associated with thermal stratification of a heated container of liquid, and the pressure history of its vapor, was performed. Analysis of the governing equations identified the modified Grashoff number, the modified Fourier number, and the interface number as the dominant dimensionless parameters associated with this process. A test program designed to verify the validity of these scaling parameters was executed. The quality of scaling was checked by comparing the dimensionless pressures and temperatures for scaled pairs of tests. Results indicate that the bulk liquid temperature, the surface temperature of the liquid, and the tank pressure can be scaled with the three dimensionless parameters. Some deviations were found in the detailed temperature profiles between the scaled pairs of tests.

Ji, H.-C.↗

NASA NTRS1991

Computational modeling of the pressurization process in a NASP vehicle propellant tank experimental simulation

A multidimensional computational model of the pressurization process in a slush hydrogen propellant storage tank was developed and its accuracy evaluated by comparison to experimental data measured for a 5 ft diameter spherical tank. The fluid mechanic, thermodynamic, and heat transfer processes within the ullage are represented by a finite-volume model. The model was shown to be in reasonable agreement with the experiment data. A parameter study was undertaken to examine the dependence of the pressurization process on initial ullage temperature distribution and pressurant mass flow rate. It is shown that for a given heat flux rate at the ullage boundary, the pressurization process is nearly independent of initial temperature distribution. Significant differences were identified between the ullage temperature and velocity fields predicted for pressurization of slush and those predicted for pressurization of liquid hydrogen. A simplified model of the pressurization process was constructed in search of a dimensionless characterization of the pressurization process. It is shown that the relationship derived from this simplified model collapses all of the pressure history data generated during this study into a single curve.

Sasmal, G. P.↗

NASA NTRS1991

Modeling of jet-induced geyser formation in a reduced gravity environment

Flow patterns predicted by a computational model of jet-induced geyser formation in a reduced gravity environment are presented and comparison is made to patterns predicted by experimentally based correlations. The configuration studied is an idealization of a forthcoming flight experiment to examine cryogenic propellant management issues. A transitional version of the ECLIPSE code used as a computational tool for the analyses is described. It is shown that computationally predicted flow patterns are in qualitative agreement with the correlation-based predictions, and some details of the predicted flow fields are given.

Wendl, M. C.↗

NASA NTRS1989

Modeling of pulsed propellant reorientation

Optimization of the propellant reorientation process can provide increased payload capability and extend the service life of spacecraft. The use of pulsed propellant reorientation to optimize the reorientation process is proposed. The ECLIPSE code was validated for modeling the reorientation process and is used to study pulsed reorientation in small-scale and full-scale propellant tanks. A dimensional analysis of the process is performed and the resulting dimensionless groups are used to present and correlate the computational predictions for reorientation performance.

Patag, A. E.↗

NASA NTRS1989

Modeling of pulsed propellant reorientation

Patag, A. E.↗

NASA NTRS1987

Temperature fields due to jet induced mixing in a typical OTV tank

The Eclipse Code is being developed as a general tool for analysis of cryogenic propellant behavior in spacecraft tankage. The focus of the work being reported is on prediction of temperature fields due to introduction of a cold jet along the centerline of a typical Orbit Transfer Vehicle tank. A brief description of the formulations used for modeling heat transfer and turbulent flow is presented. Code performance is verified through comparison to experimental data for mixing in small scale tanks. An unexpected difficulty in computing long duration flows is reviewed. Preliminary results for a partially filled full scale tank are obtained by approximating the free surface by a spherical solid boundary.

Hochstein, J. I.↗

NASA NTRS1986

Effect of subcooling on the on-orbit pressurization rate of cryogenic propellant tankage

The SOLA-ECLIPSE code is being developed to enable prediction of the behavior of cryogenic propellants in spacecraft tankage. A brief description of the formulations used for modeling heat transfer and for determining thermodynamic state is presented. Code performance is verified through comparison to experimental data for the self-pressurization of scale model liquid hydrogen tanks. SOLA-ECLIPSE is used to examine the effect of initial subcooling of the liquid phase on the self-pressurization rate of an on-orbit full scale liquid hydrogen tank typical for a chemical propulsion Orbital Transfer Vehicle. The computational predictions show that even small amounts of subcooling will significantly decrease the self-pressurization rate. Further, if the cooling is provided by a Thermodynamic Vent System, it is concluded that small levels of subcooling will maximize propellant conservation.

Hochstein, J. I.↗

NASA NTRS1985

NASA Lewis Research Center low-gravity fluid management technology program

A history of the Lewis Research Center in space fluid management technology program is presented. Current programs which include numerical modeling of fluid systems, heat exchanger/radiator concept studies, and the design of the Cryogenic Fluid Management Facility are discussed. Recent analytical and experimental activities performed to support the Shuttle/Centaur development activity are highlighted.

Aydelott, J. C.↗

NASA NTRS1985

NASA Lewis Research Center low-gravity fluid management technology program

Aydelott, J. C.↗

NASA NTRS1984

Computational modeling of jet induced mixing of cryogenic propellants in low-G

The SOLA-ECLIPSE Code is being developed to enable computational prediction of jet induced mixing in cryogenic propellant tanks in a low-gravity environment. Velocity fields, predicted for scale model tanks, are presented which compare favorably with the available experimental data. A full scale liquid hydrogen tank for a typical Orbit Transfer Vehicle is analyzed with the conclusion that coupling an axial mixing jet with a thermodynamic vent system appears tobe a viable concept for the control of tank pressure. Previously announced in STAR as N84-25000

Hochstein, J. I.↗

NASA NTRS1984

Computational modeling of jet induced mixing of cryogenic propellants in low-G

The SOLA-ECLIPSE Code is being developed to enable computational prediction of jet induced mixing in cryogenic propellant tanks in a low-gravity environment. Velocity fields, predicted for scale model tanks, are presented which compare favorably with the available experimental data. A full scale liquid hydrogen tank for a typical Orbit Transfer Vehicle is analyzed with the conclusion that coupling an axial mixing jet with a thermodynamic vent system appears to be a viable concept for the control of tank pressure.

Hochstein, J. I.↗