Book Section records
https://feeds.library.caltech.edu/people/Acosta-A-J/book_section.rss
A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenFri, 12 Apr 2024 23:12:36 +0000An Experimental Study of Cavitating Inducers
https://resolver.caltech.edu/CaltechAUTHORS:20140722-160825878
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1958
The user of a turbo machine is mainly interested only in the overall hydrodynamic performance of the device. However, the designer is almost always confronted with
the problem of achieving the intended performance in the face of many conflicting hydrodynamic and system requirements. In certain areas it may happen that a
formerly deleterious effect (such as the occurrence of cavitation) can be turned to good advantage as in the case of the supercavitating hydrofoil or propeller. Unfortunately, this happy circumstance is not the lot of the designer of a liquid pumping system when the effects of cavitation are predominant. That this is so, follows from
the fact that the dissipation effects in production of lift by a hydrofoil are relatively unimportant whereas dissipation is important in the decrease of energy of a fluid stream as in the case of a pump.https://authors.library.caltech.edu/records/8bw81-cbn71Observations on the Performance of Centrifugal Pumps at Low Reynolds Numbers
https://resolver.caltech.edu/CaltechAUTHORS:20140722-162608189
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Hollander-A', 'name': {'family': 'Hollander', 'given': 'A.'}}]}
Year: 1966
From the results presented herein it is clear that
the viscous flow in the centrifugal pump impeller is
very complicated, but we see that the internal flow itself
is not necessarily too inefficient and further that
the hydraulic torque does not necessarily increase with
lower Reynolds numbers. These results mean that the
effect of external disc friction and its interaction in
the volute are as important as the impeller design itself
for such viscous flows. The present tests suggest that
a pump which works well at high Reynolds numbers, as for
water application, will not necessarily be the best pump
for the low Reynolds number application. These internal
flows are certainly very complicated and the authors hope
that some of the techniques and suggestions made herein
will be used for such work by others in the future.https://authors.library.caltech.edu/records/cqm60-9n284A Note on Turbopump Blade Cavitation Compliance for the POGO Instability
https://resolver.caltech.edu/CaltechAUTHORS:BREpff72
Authors: {'items': [{'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1972
During the first or booster stage of flight many liquid-propellant rockets have experienced severe longitudinal vibrations caused by a closed loop interaction between the first longitudinal structural mode and the dynamics of the propulsion system. This, "POGO" instability, reviewed in Reference 1, has been the subject of intensive research since it was first encountered. One of the most important transients in the dynamic modelling of the propulsion system is the "cavitation compliance" of the turbopumps [3] defined as the negative of the derivative of the cavity and bubble volume in the pump and its suction line with respect to the section pressure. Thus, it describes the oscillatory source/sink behavior of the pump due to changes in the cavity volume. Past analyses [1, 2] have suggested dividing this compliance into two components corresponding to the two major types of pump cavitation, namely blade cavitation and back-flow cavitation.
The purpose of this paper is to present some preliminary results of theoretical calculations of blade cavitation compliance. The most satisfactory starting point would be a theory for unsteady cavitating flow in a cascade. Whilst work on this is in progress at the present time, the low frequency or quasistatic approach based on existing steady flow theory is much simpler and in itself yields interesting results.https://authors.library.caltech.edu/records/bt893-vwf43The Dynamic Performance of Cavitating Turbopumps
https://resolver.caltech.edu/CaltechAUTHORS:CEBcfm75
Authors: {'items': [{'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'Christopher'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}]}
Year: 1975
Knowledge of the dynamic performance of turbopumps is essential for the prediction of instabilities in hydraulic systems; the necessary information is in the form of a transfer function relating the instantaneous pressures and mass flow rates at inlet and discharge. Cavitation has a significant effect on this transfer function since dynamical changes in the volume of cavitation contribute to the difference in the instantaneous flow rates. The present paper synthesizes the transfer matrix for cavitating inducers at moderately low frequencies and shows that the numerical results are consistent with observations on rocket engine turbopumps.https://authors.library.caltech.edu/records/vf0we-yrf16Some transition and cavitation inception observations on a 1.5 cal ogive
https://resolver.caltech.edu/CaltechAUTHORS:20150410-103711329
Authors: {'items': [{'id': 'Arakeri-V-H', 'name': {'family': 'Arakeri', 'given': 'V. H.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1975
Transition observation on a 1. 5 cal ogive were carried out by Schlieren technique of flow visualization up to Re_D of 1.26 x 10^6. Good agreement is found between computed position of transition by Smith method and those observed by Schlieren technique for tunnel velocities greater than 50 fps (Re_D> 7.85 x 10^5). Cavitation under desinent conditions at tunnel velocities of 30 fps and 40 fps was found to occur within the transition region of the boundary layer. At 50 fps good agreement is found between the present value of inception cavitation index, the value of desinent cavitation index measured by Parkin and the negative value of the pressure coefficient at both predicted and observed positions of transition. These observations strongly suggest that cavitation inception is closely related to transition on smooth bodies at supercritical Reynolds numbers.https://authors.library.caltech.edu/records/0kgy6-7de38Cavitation inception
https://resolver.caltech.edu/CaltechAUTHORS:20150413-101139951
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Parkin-B-R', 'name': {'family': 'Parkin', 'given': 'B. R.'}}]}
Year: 1975
We are sure that the delegates to the present conference do not need to be reminded that cavitation inception in the pervasive role it occupies in Naval Architectural hydrodynamics remains as a basic problem bedevilling the worker in the laboratory and field alike. One of the more perplexing aspects of this phenomenon has been its lack of repeatability between experiments carried out on similar test bodies in different test facilities or even on different types of bodies in the same test facility. In addition, in sea trials, the conditions under which it occurs are seldom well defined. There is the further problem of accounting properly for the effects of modifying the test fluid itself either by a change in state point or by the addition of an additional liquid solute such as a long chain polymeric molecule or finely divided particulate matter. Underlying all these considerations is the ultimate goal of extrapolating laboratory findings to representative field conditions; in the present context, these are the various conditions of the marine environment. This specific point was addressed briefly in the concluding discussion on cavitation inception of the 16th conference in which the onus of reporting progress towards this goal was laid upon the present authors. It would indeed be gratifying to report to the present conference that our experimental techniques are now sufficiently advanced to simulate properly all of the important prototype conditions even if we had precise knowledge of them. This is, regrettably, not yet the case, but there have been nevertheless solid advances in certain areas of cavitation inception research which make one hopeful for the future. We have selected three such areas to report on to the present conference; viz, surface inception, vortex cavitation and scaling, and the effects of polymer additive on inception. In addition, we refer briefly to current methods of observation/measurement of cavitation nuclei as this is a subject of paramount importance to the cavitation process itself and also because we suspect such measurement will become an important part of laboratory testing in the near future.
In the material to follow we have tried to emphasize the phenomena and techniques themselves leaving to a future occasion a full assessment of inception scaling theories. We have not attempted to be encyclopedic in coverage as there are recent excellent texts and survey articles, e.g. Arndt (1971), Eisenberg (1969), Eisenberg and Tulin (1961), Knapp et al (1970), Robertson and Wislicenus (1969) Grein (1973) which cover the field, and we should also state that in so doing any serious omissions we may have made are not intentional!https://authors.library.caltech.edu/records/whf8e-k4e29A Test Program to Measure Fluid Mechanical Whirl-Excitation Forces in Centrifugal Pumps
https://resolver.caltech.edu/CaltechAUTHORS:BREriphpt80
Authors: {'items': [{'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1980
Much speculation has surrounded the possible unsteady hydrodynamic forces which could be responsible for the excitation of whirl instabilities in turbomachines. However there exist very few measurements of these forces which would permit one to evaluate the merits of the existing fluid mechanical analyses. In keeping with the informal nature of this workshop we will present details of a proposed test program for the measurement of the unsteady forces on centrifugal impellers caused by either (i) azimuthal asymmetry in the volute geometry or (ii) an externally imposed whirl motion of the impeller. In the second case the forces resulting from the imposed whirl motions with frequencies ranging from zero to synchronous will be measured by means of a force balance upon which the impeller is mounted. This work is presently being carried out under contract with the NASA George Marshall Space Flight Center, Huntsville, Alabama (Contract NAS 8-33108).https://authors.library.caltech.edu/records/jjytr-3n908A Brief Note on the Interaction of an Actuator Cascade with a Singularity
https://resolver.caltech.edu/CaltechAUTHORS:CHAriphpt80
Authors: {'items': [{'id': 'Chamieh-D-S', 'name': {'family': 'Chamieh', 'given': 'D.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1980
We have recently become concerned with making estimates of steady forces that may be exerted between moving blade rows and stationary blade rows or volutes. Our present interest is with time averaged forces for estimation of shaft loads and flow asymmetry forces rather than with transient processes. For this purpose we have adopted the well-known "actuator" model for the blade row in which the flow leaving the row or cascade is assumed to have a constant leaving angle. The disturbances external to this row such as a volute may be represented by distributions of vortex elements as was done for example by Domm and Hergt [1].https://authors.library.caltech.edu/records/r1tac-56m66Observations of nuclei in cavitating flows
https://resolver.caltech.edu/CaltechAUTHORS:20201120-120817537
Authors: {'items': [{'id': 'Katz-Joseph', 'name': {'family': 'Katz', 'given': 'Joseph'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan'}}]}
Year: 1982
DOI: 10.1007/978-94-009-7532-3_11
The present report focuses on the source of the large difference between the theoretical strength of pure liquid and the actual tension that is required to initiate cavitation in technical fluids such as test facilities and natural waters. This discrepancy is commonly explained by the existence of nuclei, either solid particles or vapor and gas bubbles that permit phase transition to take place near equilibrium. The existence of these nuclei, their source and lifetimes have occupied much space in the technical literature for decades. Yet, direct observations of tests in applications to naval hydrodynamics and hydraulic machinery flows has not provided much information about these nuclei. Their existence, however, and their effect on cavitation is in no doubt as is demonstrated by the series of photographs of a propeller that were taken in the 'Vacu-Tank' of NSMB shown in Figure 1. There, addition of 'nucleating' sources to the water by electrolysis clearly increases the number of visible cavitating bubbles on the blade surfaces.https://authors.library.caltech.edu/records/js1zv-4f915Experimental Measurements of Hydrodynamic Stiffness Matrices for a Centrifugal Pump Impeller
https://resolver.caltech.edu/CaltechAUTHORS:CHAriphpt82
Authors: {'items': [{'id': 'Chamieh-D-S', 'name': {'family': 'Chamieh', 'given': 'D. S.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}, {'id': 'Franz-R-J', 'name': {'family': 'Franz', 'given': 'R.'}}]}
Year: 1982
The objective of the Rotor Force Test Facility at the California Institute of Technology is to artificially orbit the center of rotation of an impeller enclosed within a volute over a range of frequencies from zero to synchronous and to measure the resulting forces on the impeller. This paper reports preliminary data from the first stage experiments in which the shaft is orbited at low frequency. Steady volute forces along with stiffness matrices due to the change in position of the rotor center are measured. Static pressure taps around the volute are used to obtain volute pressure distributions for various fixed positions of the impeller center and for various flow rates. Static pressure forces are calculated from these pressure distributions allowing a more complete analysis of the components of the impeller forces. Comparison is made with various existing theoretical and experimental results.https://authors.library.caltech.edu/records/x3tzr-6gw30On the linearized dynamics of two-dimensional bubbly flows over wave-shaped surfaces
https://resolver.caltech.edu/CaltechAUTHORS:20130725-163717360
Authors: {'items': [{'id': "d'Agostino-L", 'name': {'family': "d'Agostino", 'given': 'L.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1984
In the last decades the technological importance or bubbly
flows has generated considerable efforts to achieve a
better understanding of their properties, [1],[2]. However,
the presence or two interacting phases so much increases
the complexity or the problem that a satisfactory
mathematical model of these flows has been possible only in
special cases under fairly restrictive simplifying assumptions.
The main purpose of the present note is to investigate
the effects due to the inclusion or bubble dynamic response
in two-dimensional flows over wave-shaped surfaces.
The earlier studies of bubbly flows based on space averaged
equations for the mixture in the absence or relative
motion between the two phases, [5], [6], do not consider
bubble dynamic effects. This approach simply leads to an
equivalent compressible homogeneous medium and has
been used to analyze the behaviour or one-dimensional bubbly
flows through converging-diverging nozzles.
In order to account for bubble dynamic response, in a
classical paper by Foldy, [7], each individual bubble is
described as a randomly distributed point scatterer. Assuming
that the system is ergodic, the collective effect of bubble
dynamic response on the flow is then obtained by taking the
ensemble average over all possible configurations. An alternative
way to account for bubble dynamic effects would be
to include the Rayleigh-Plesset equation in the space averaged
equations. Both methods have been successfully
applied to describe the propagation or one-dimensional perturbances
through liquids containing small gas bubbles, [8],
[9], [10], [11].
However, because of their complexity, there are not many
reported examples of the application to specific flow
geometries of the space averaged equations which include
the effects of bubble response, [12]. In an earlier note, [13],
we considered the one-dimensional time dependent linearized
dynamics or a spherical cloud of bubbles. The results
clearly show that the motion of the cloud is critically controlled
by bubble dynamic effects. Specifically, the dominating
phenomenon consists of the combined response of the
bubbles to the pressure in the surrounding liquid, which
results in volume changes leading to a global accelerating
velocity field. Associated with this velocity field is a pressure
gradient which in turn determines the pressure encountered
by each individual bubble in the mixture.
Furthermore, it can be shown that such global interactions
usually dominate any pressure perturbations experienced
by one bubble due to the growth or collapse or a neighbor
(see section 5).
In the present note the same approach is applied to the
two-dimensional case or steady flows over wave-shaped surfaces
(for which there exist well established solutions for
compressible and incompressible flow), With the aim, as previously
stated, of assessing the effects due to the introduction
or bubble dynamic response. Despite its intrinsic limitations,
the following linear analysis indicates some of the
fundamental phenomena involved in such flows and provides
a useful basis for the study of the same flows with
non-linear bubble dynamics, which we intend to discuss in a
later publication. The present extention to the case of bubbly
flows over arbitrarily shaped surfaces also constitutes
the starting point for the investigation or such flows, a problem
of considerable technical interest, for example in cavitating
flows past lifting surfaces.https://authors.library.caltech.edu/records/9ndb4-60d20Two-Dimensional Unsteady Analysis of Fluid Forces on a Whirling Centrifugal Impeller in a Volute
https://resolver.caltech.edu/CaltechAUTHORS:TSUriphpt84
Authors: {'items': [{'id': 'Tsujimoto-Y', 'name': {'family': 'Tsujimoto', 'given': 'Y.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}]}
Year: 1984
Destabilizing fluid forces on a whirling centrifugal impeller rotating in a volute have been observed (Ref. 1). A quasisteady analysis neglecting shed vorticity (Ref. 2) or an unsteady analysis without a volute (Ref. 3) does not predict the existence of such destabilizing fluid forces on a whirling impeller.
The present report is intended to take into account the effects of a volute and the shed vorticity. We treat cases when an impeller with an infinite number of vanes rotates with a constant velocity [omega] and its center whirls with a constant eccentric radius {epsilon] and a constant whirling velocity [omega].https://authors.library.caltech.edu/records/tgy38-7hz78Hydrodynamic Impeller Stiffness, Damping, and Inertia in the Rotordynamics of Centrifugal Flow Pumps
https://resolver.caltech.edu/CaltechAUTHORS:JERriphpt84
Authors: {'items': [{'id': 'Jery-B', 'name': {'family': 'Jery', 'given': 'B.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1984
Measurements were made of the lateral hydrodynamic forces experienced by a centrifugal pump impeller performing circular whirl motions within several volute geometries. Experiments were conducted for various flow coefficients, [phi], impeller rotating speeds or angular frequencies, w, and the angular frequency of the whirl motion, [omega], was varied from zero to nearly synchronous (equation) and to nearly antisynchronous (equation). The lateral forces were decomposed into (i) time averaged lateral forces and (ii) hydrodynamic force matrices representing the variation of the lateral forces with position of the impeller center. No assumptions concerning the form of these matrices need to be made. The latter can be further decomposed according to the variation with whirl frequency, the result being "stiffness", "damping", and "fluid inertial" rotordynamic force matrices. It was found that these force matrices essentially consist of equal diagonal terms and skew-symmetric off-diagonal terms. One consequence of this is that during its whirl motion the impeller experiences forces acting normal and tangential to the locus of whirl. Data on these normal and tangential forces are presented; in particular it is shown that there exists a region of positive reduced whirl frequencies, [omega/w], within which the hydrodynamic forces can be destabilizing with respect to whirl.https://authors.library.caltech.edu/records/98ds9-3jw38Impeller Fluid Forces
https://resolver.caltech.edu/CaltechAUTHORS:BREaeopt86
Authors: {'items': [{'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1986
This paper addresses the issue of the steady and unsteady forces which may be imparted to a pump impeller by the through flow. The historical trend to increase the power density and speed of turbomachines has inevitably led to an increase in the number of fluid/structure interaction problems because the fluid forces scale like the square of the speed and thus become increasingly important relative to the structural strength. The present paper focuses on the radial forces acting on the impeller of a pump. Under the sponsorship of NASA, the authors have, over the past few years, conducted an extensive investigation of these forces and the associated hydrodynamically induced rotordynamic coefficients. A new facility, called the Rotor Force Test Facility was designed and constructed for the experimental component of this program. Measurements of the forces and rotordynamic coefficients have been made for a range of different impeller and volutes and include tests with the impeller of the high pressure oxygen turbopump (HPOTP) in the Space Shuttle Main Engine. Furthermore, tests have been conducted with different leakage flow geometries and, with different levels of pump cavitation. The paper will summarize these experimental measurements and the results of some theoretical analyses.https://authors.library.caltech.edu/records/q09wm-syv05On the Effect of Cavitation on the Radial Forces and Hydrodynamic Stiffness of a Centrifugal Pump
https://resolver.caltech.edu/CaltechAUTHORS:FRAriphpt86
Authors: {'items': [{'id': 'Franz-R-J', 'name': {'family': 'Franz', 'given': 'R. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1986
The asymmetric flow within a volute exerts a radial force on a centrifugal impeller. The present paper presents experimental measurements of the radial forces on the impeller in the presence of cavitation.https://authors.library.caltech.edu/records/2n8vk-2gq42Unsteady Diffuser Vane Pressure and Impeller Wake Measurements in a Centrifugal Pump
https://resolver.caltech.edu/CaltechAUTHORS:ARNcfm87
Authors: {'items': [{'id': 'Arndt-N', 'name': {'family': 'Arndt', 'given': 'N.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1987
Unsteady surface pressure measurements on a vaned diffuser of a centrifugal pump, and wake measurement of the flow exiting a centrifugal impeller into a vaneless diffuser are presented. Frequency spectra and ensemble averages are given for the unsteady measurements. Two different impellers were used, the pump impeller of the HPOTP (High Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Engine) and a two-dimensional impeller. The magnitude of the unsteady total pressure measured in the stationary frame at the impeller exit was found to be of the same order of magnitude as the total pressure rise across the pump. The magnitude of the unsteady diffuser vane pressures was observed to be significantly different on suction and pressure side of the vane, attaining its largest value on the suction side near the leading edge while decreasing along the vane.https://authors.library.caltech.edu/records/s5dc5-x4s59Rotordynamic Forces on Centrifugal Pump Impellers
https://resolver.caltech.edu/CaltechAUTHORS:FRAecfm87
Authors: {'items': [{'id': 'Franz-R-J', 'name': {'family': 'Franz', 'given': 'R.'}}, {'id': 'Arndt-N', 'name': {'family': 'Arndt', 'given': 'N.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1987
The asymmetric flow around an impeller in a volute exerts a force upon the impeller. To study the rotordynamic force on an impeller which is vibrating around its machine axis of rotation, the impeller, mounted on a dynamometer, is made to whirl in a circular orbit within the volute. The measured force is expressed as the sum of a steady radial force and an unsteady force due to the eccentric motion of the impeller. These forces were measured in separate tests on a centrifugal pump with radically increased shroud clearance, a two-dimensional impeller, and an impeller with an inducer, the impeller of the HPOTP (High Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Enginer). In each case, a destabilizing force was observed over a region of positive whirl.https://authors.library.caltech.edu/records/pxvhr-7j996Experimental Investigation of Rotor-Stator Interaction in a Centrifugal Pump with Several Vaned Diffusers
https://resolver.caltech.edu/CaltechAUTHORS:ARNjt90
Authors: {'items': [{'id': 'Arndt-N', 'name': {'family': 'Arndt', 'given': 'N.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1989
DOI: 10.1115/89-GT-62
This paper describes an experimental investigation of rotor-stator interaction in a centrifugal pump with several vaned diffusers. Steady and unsteady diffuser vane pressure measurements were made for a two-dimensional test impeller. Unsteady impeller blade pressure measurements were made for a second two-dimensional impeller with blade number and blade geometry identical to the two-dimensional impeller used for the diffuser vane pressure measurements. The experiments were conducted for different flow coefficients and differeent radial gaps between the impeller blade trailing edge and the diffuser vane leading edge (5 and 8 percent of the impeller discharge radius). The largest pressure fluctuations on the diffuser vanes and the impeller blades were found to be of the same order of magnitude as the total pressure rise across the pump. The largest pressure fluctuations on the diffuser vanes were observed to occur on the suction side of the vane near the vane leading edge, whereas on the impeller blades the largest fluctuations were observed to occur at the blade trailing edge. However, the dependence of the fluctuations on the flow coefficient was found to be different for te diffuser vanes and the impeller blades; on the vane suction side, the fluctuations were largest for the maximum flow coefficient and decreased with decreasing flow coefficient, whereas at the blade trailing edge, the fluctuations were smallest for the maximum flow coefficient and increased with decreasing flow coefficient. Increasing the number of the diffuser vanes resulted in a significant decrease of the impeller blade pressure fluctuations. The resulting lift on the diffuser vanes was computed from the vane pressure measurements; the magnitude of the fluctuating lift was found to be larger than the steady lift.https://authors.library.caltech.edu/records/vgx0t-j5982The Rotordynamic Forces on a Centrifugal Pump Impeller in the Presence of Cavitation
https://resolver.caltech.edu/CaltechAUTHORS:FRAasmespm89
Authors: {'items': [{'id': 'Franz-R-J', 'name': {'family': 'Franz', 'given': 'R.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1989
An experiment in forced vibration was conducted to study the fluid-induced rotordynamic force on an impeller whirling along a trajectory eccentric to its undeflected position. The prescribed whirl trajectory of the rotor is a circular orbit of a fixed radius. The force measured is a combination of a steady radial force due to volute asymmetries and an unsteady force due to the eccentric motion of the rotor. These measurements have been conducted over a full range of whirl/impeller speed ratios at different flow coefficients for various turbomachines. A destabilizing force was observed over a region of positive whirl ratio. The range of flow conditions examined for a centrifugal impeller in a spiral volute has been enlarged to include cavitation. Compared to the non-cavitating condition, cavitation corresponding to a head loss of three percent did not have a significant effect upon the unsteady force.https://authors.library.caltech.edu/records/pgt78-e7933Impeller-Induced Rotor-Dynamic Forces
https://resolver.caltech.edu/CaltechAUTHORS:BREkfe89
Authors: {'items': [{'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'Christopher E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'Thomas K.'}}]}
Year: 1989
The flow through and around the rotor of a turbomachine exerts a force on the rotor and, hence, rotor shaft and bearing system. In some circumstances this force may lead to excitation of shaft whirl in the direction of impeller rotation. Recent international research of this phenomenon is briefly reviewed; these findings suggest that turbomachines intended to operate well above the first critical speed should take the effect into account.https://authors.library.caltech.edu/records/whec1-45a43Measurements for the rotordynamic shroud forces for centrifugal pumps
https://resolver.caltech.edu/CaltechAUTHORS:GUI108
Authors: {'items': [{'id': 'Guinzburg-A', 'name': {'family': 'Guinzburg', 'given': 'A.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1990
An experiment was designed to measure the rotordynamic shroud forces on a centrigual pump impeller. The measurements were doen for various whirl/impeller ratios and for different flow rates. A destabilising tangential force was measured for small positive whirl ratios and this force decreased with increasing flow rate.https://authors.library.caltech.edu/records/vffkf-r3c21Observations of Cavitation on a Three-Dimensional Oscillating Hydrofoil
https://resolver.caltech.edu/CaltechAUTHORS:HARasmecmff90
Authors: {'items': [{'id': 'Hart-D-P', 'name': {'family': 'Hart', 'given': 'D. P.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}]}
Year: 1990
A test apparatus was designed and constructed to observe the effect of sinusoidal pitching oscillations on the cavitation of three-dimensional hydrofoils. The apparatus is capable of oscillating hydrofoils at a rate up to 50 Hz and provides for adjustments in oscillation amplitude and mean angle of attack. Observations of the effect of pitching oscillation on cavitation have been made for a NACA 64-309 (modified) hydrofoil operating at its designed mean angle of attack of 7 degrees with an oscillation amplitude of 2 degrees. Photographs illustrating the interaction between natural cavity shedding frequencies and the foil reduced frequency are included.https://authors.library.caltech.edu/records/9snm4-y9p66The Influence of Swirl Brakes on the Rotordynamic Forces Generated by Discharge-to-Suction Leakage Flows in Centrifugal Pumps
https://resolver.caltech.edu/CaltechAUTHORS:SIVfed93
Authors: {'items': [{'id': 'Sivo-J-M', 'name': {'family': 'Sivo', 'given': 'Joseph M.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'Christopher E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'Thomas K.'}}]}
Year: 1993
Increasing interest has been give to swirl brakes as a means of reducing destabilizing rotordynamic forces due to leakage flows in new high speed rocket turbopumps. Although swirl brakes have been used successfully in practice (such as with the Space Shuttle HPOTP), no experimental test until now have been performed to demonstrate their beneficial effect over a range of leakage flow rates. The present study investigates the effect of swirl brakes on rotordynamic forces generated by discharge-to-suction leakage flows in the annulus of shrouded centrifugal pumps over a range of subsynchronous whirl ratios and various leakage flow rates. In addition, the effectiveness of swirl brakes in the presence of leakage inlet (pump discharge) swirl is also demonstrated. The experimental data demonstrates that with the addition of swirl brakes a significant reduction in the destabilizing tangential force for lower flow rates is achieved. At higher flow rates, the brakes are detrimental. In the presence of leakage inlet swirl, brakes were effective over all leakage flow rates tested in reducing the range of whirl frequency ratio for which the tangential force is destabilizing.https://authors.library.caltech.edu/records/9a2zk-4np65Observations on Off-Design Flows in Non-Cavitating Axial Flow Inducers
https://resolver.caltech.edu/CaltechAUTHORS:BHAfed93
Authors: {'items': [{'id': 'Bhattacharyya-A', 'name': {'family': 'Bhattacharyya', 'given': 'Abhijit'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'Christopher E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'Thomas K.'}}]}
Year: 1993
This paper describes an investigation of the flows in unshrouded and shrouded inducers which are known to be highly complex, three dimensional flows with real fluid effects. A flow visualization technique using tufts and paint dots was used to study the flows on the blade, hub and housing at off-design flows. It was found that the blade boundary layer flows were attached to the blade surface and that leakage flows were the cause of the upstream swirling backflow in unshrouded inducers. It was also found that shrouded inducers showed flow reversal near the leading edge in addition to the discharge-to-suction leakage flow. The observations provide a better understanding of the internal flows and the occurrence of upstream backflows.https://authors.library.caltech.edu/records/zev64-8qz94The Influence of Swirl Brakes and a Tip Discharge Orifice on the Rotordynamic Forces Generated by Discharge-to-Suction Leakage Flows in Shrouded Centrifugal Pumps
https://resolver.caltech.edu/CaltechAUTHORS:SIVcfdarp93
Authors: {'items': [{'id': 'Sivo-J-M', 'name': {'family': 'Sivo', 'given': 'J. M.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}]}
Year: 1993
Recent experiments conducted in the Rotor Force Test Facility at the California Institute of Technology have examined the effects of a tip leakage restriction and swirl brakes on the rotordynamic forces due to leakage flows on an impeller undergoing a prescribed circular whirl. The experiments simulate the leakage flow conditions and geometry of the Alternate Turbopump Design (ATD) of the Space Shuttle High Pressure Oxygen Turbopump and are critical to evaluating the pump's rotordynamic instability problems. Previous experimental and analytical results have shown that discharge-to-suction leakage flows in the annulus of a shrouded centrifugal pump contribute substantially to the fluid induced rotordynamic forces. Also, previous experiments have shown that leakage inlet (pump discharge) swirl can increase the cross-coupled stiffness coefficient and hence increase the range of positive whirl for which the tangential force is destabilizing. In recent experimental work, the present authors demonstrated that when the swirl velocity within the leakage path is reduced by the introduction of ribs or swirl brakes, then a substantial decrease in both the destabilizing normal and tangential forces could be achieved. Motivation for the present research is that previous experiments have shown that restrictions such as wear rings or orifices at pump inlets affect the leakage forces. Recent pump designs such as the Space Shuttle Alternate Turbopump Design (ATD) utilize tip orifices at discharge for the purpose of establishing axial thrust balance. The ATD has experienced rotordynamic instability problems and one may surmise that these tip discharge orifices may also have an important effect on the normal and tangential forces in the plane of impeller rotation. The present study determines if such tip leakage restrictions contribute to undesirable rotordynamic forces. Additional motivation for the present study is that the widening of the leakage path annular clearance and the installation of swirl brakes in the ATD has been proposed to solve its instability problems. The present study assesses the effect of such a design modification on the rotordynamic forces. The experimental apparatus consists of a solid or dummy impeller, a housing instrumented for pressure measurements, a rotating dynamometer and an eccentric whirl mechanism. The solid impeller is used so that leakage flow contributions to the forces are measured, but the main throughflow contributions are not experienced. The inner surface of the housing has been modified to accommodate meridional ribs or swirl brakes within the leakage annulus. In addition, the housing has been modified to accommodate a discharge orifice that qualitatively simulates one side of the balance piston orifice of the Space Shuttle ATD. Results indicate the detrimental effects of a discharge orifice and the beneficial effects of brakes. Plots of the tangential and normal forces versus whirl ratio show a substantial increase in these forces along with destabilizing resonances at some positive whirl ratios when a discharge orifice is added. When brakes are added, some of the detrimental effects of the orifice are reduced. For the tangential force, a plot versus whirl ratio shows a significant reduction and a destabilizing resonance appears to be eliminated. For the normal force, although the overall force is not reduced, again a destabilizing resonance appears to be eliminated.https://authors.library.caltech.edu/records/rhnxr-mcz84Rotordynamic Forces in Cavitating Inducers
https://resolver.caltech.edu/CaltechAUTHORS:BHAfed94
Authors: {'items': [{'id': 'Bhattacharyya-A', 'name': {'family': 'Bhattacharyya', 'given': 'Abhijit'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'Allan J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'Christopher E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'Thomas K.'}}]}
Year: 1994
This paper reports an experimental investigation of the rotordynamic forces that occur in a whirling three bladed inducer under the influence of cavitation. The effect of lowering the flow coefficient (and thus causing reverse flows) on these forces were also investigated. The results show the occurrence of large destabilizing peaks in the force tangential to the whirl orbit for positive whirl frequency ratios. Cavitation caused these forces to become destabilizing at both negative and positive whirl frequency ratios. The magnitude of the destabilizing forces increased with decreasing vacitation numbers and flow coefficient. The rotordynamic data obtained do not exhibit the kind of quadratic functional behavior which is normally ussumed in many rotordynamic models. Consequently the conventional generalized stiffness, damping and interia matrices cannot be determined for the inducer. The results demonstrate the complexity of rotordynamic forces and their consequences on stability of axial flow inducers.https://authors.library.caltech.edu/records/a9j98-a1r67Laser Velocimeter Measurements in the Leakage Annulus of a Whirling Shrouded Centrifugal Pump
https://resolver.caltech.edu/CaltechAUTHORS:SIVasla94
Authors: {'items': [{'id': 'Sivo-J-M', 'name': {'family': 'Sivo', 'given': 'J. M.'}}, {'id': 'Acosta-A-J', 'name': {'family': 'Acosta', 'given': 'A. J.'}}, {'id': 'Brennen-C-E', 'name': {'family': 'Brennen', 'given': 'C. E.'}}, {'id': 'Caughey-T-K', 'name': {'family': 'Caughey', 'given': 'T. K.'}}, {'id': 'Ferguson-T-V', 'name': {'family': 'Ferguson', 'given': 'T. V.'}}, {'id': 'Lee-G-A', 'name': {'family': 'Lee', 'given': 'G. A.'}}]}
Year: 1994
Previous experiments conducted in the Rotor Force Test Facility at the California Institute of Technology have thoroughly examined the effect of leakage flows on the rotordynamic forces on a centrifugal pump impeller undergoing a prescribed circular whirl. These leakage flows have been shown to contribute substantially to the total fluid induced forces acting on a pump. However, to date nothing is known of the flow field in the leakage annulus of shrouded centrifugal pumps. No attempt has been made to qualitatively or quantitatively examine the velocity field in the leakage annulus. Hence the test objective of this experiment is to acquire fluid velocity data for a geometry representative of the leakage annulus of a shrouded centrifugal pump while the rotor is whirling using laser velocimetry. Tests are performed over a range of whirl ratios and a flowrate typical of Space Shuttle Turbopump designs. In addition to a qualitive study of the flow field, the velocity data can be used to anchor flow models.https://authors.library.caltech.edu/records/fe7w3-44e64