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RESEARCH PAPERS

J. Eng. Power. 1967;89(4):453-462. doi:10.1115/1.3616712.

This paper describes in some detail the methods used for generation of a computer program for analyzing the off-design performance of axial compressors. The purpose of the study was to predict such axial-compressor characteristics as pressure rise and efficiency as a junction of mass flow and rotor speed when only the mechanical geometry of the annulus and blades are given. The aerodynamic analysis is divided into two basic parts. The first part of the analysis involves the numerical solution of the equations of motion in the compressor to find the flow field, temperature and pressure rise, and efficiency of the compressor. The second part concerns the analysis of the blade elements, in particular their performance at various angles of attack. Several effects are included that have a bearing on this performance. The relative Mach number and the axial-velocity ratio across the blade element, together with the shape of the blade and its configuration in the compressor, affect the flow discharging from the blade. Therefore, an elaborate study has been included to find the flow angle at the blade discharge and the pressure losses of the flow passing through the blade row. The calculation procedures have been tested by applying them to a number of compressors for which sufficient experimental data were available. A one-stage, a two-stage transonic, and a 13-stage axial compressor have been investigated and good agreement with experiments has been found provided the correct boundary layer displacement thickness along the annulus wall is used.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1967;89(4):463-476. doi:10.1115/1.3616713.

The experimental results of the relative velocity distributions together with the static pressure distributions within the impeller channels of radial-inflow turbines with and without splitter vanes are presented. The flow patterns within three stream surfaces (blade-to-blade surfaces) having different passage depths are shown using two performance parameters, i.e., nondimensional weight flow and nondimensional rotation speed. The impellers used were of purely radial type or of two-dimensional type. Further, theoretical predictions for the relative velocity distributions within the impeller channels having no splitter vanes were conducted, and comparisons of the theoretical results with experimental data were made.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1967;89(4):478-490. doi:10.1115/1.3616716.

An attempt is made in this paper to develop forms of the equation of motion, the continuity equation, and the equations which define the fluid which are amenable to a solution by what has come to be termed “the streamline curvature approach.” The techniques were developed in their present form specifically as a result of the comparatively recent interest in the axial compressor for jet engines. Fluid fields, in general, can be considered to have different energy levels on differing surfaces, to be subject to boundary conditions which impose significant curvature accelerations, and to be rotational. An intelligent exploitation of the possibilities inherent in these degrees of flexibility can very significantly modify and improve the turbomachine; the techniques thereby become adaptable to other situations. It is part of the purpose of this paper to suggest that the technique has become sufficiently mature so that a careful appraisal of its relevance to areas other than turbomachinery is in order.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1967;89(4):491-501. doi:10.1115/1.3616717.

The nature of some of the modes of vibration of blades having a free-pin attachment is discussed, with particular reference to expected positions of failure, bending-stress distribution, and calculation of natural frequencies. Some aspects of aerodynamic damping and prediction of amplitudes in distorted flow are also treated, and a critical direction of blade vibration is indicated and shown to exist in a particular mode of a compressor blade.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1967;89(4):502-512. doi:10.1115/1.3616718.

The forced vibration response of subsystems with different natural frequencies and damping, attached to a foundation with finite stiffness or mass, is calculated. Analytical models include simulations of turbomachine blading on a flexible disk or on a rotor with finite mass. Coupling through the disk or rotor explains variations in resonant frequencies and amplitudes that have been observed in blade-vibration tests. Effects on damping measurements are also determined.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1967;89(4):513-527. doi:10.1115/1.3616719.
Abstract
Commentary by Dr. Valentin Fuster
J. Eng. Power. 1967;89(4):529-538. doi:10.1115/1.3616724.

A compressed air system which initially failed to depress draft-tube water for synchronous condensing operation on a propeller turbine-driven hydroelectric generating unit was tested to determine cause of failure and formulate corrective measures. A hypothesis and certain assumptions concerning air and water action in the draft tube were essentially verified by further testing. Final testing of the modified evacuation air system demonstrated ample capability to attain a synchronous condensing condition. Several conclusions were drawn from the testing and modification work.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1967;89(4):540-545. doi:10.1115/1.3616727.

Transient load rejection data obtained from and applied to Kaplan turbines are presented. The dynamic response of the system was investigated and stabilized after blade servopressure analyses. The interrelationship between gate position, blade position, blade servopressure, draft-tube pressure, and speed is shown for Kaplan turbines and propeller turbines for different types of load rejections.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1967;89(4):547-556. doi:10.1115/1.3616731.

A method of analyzing the transient behavior of a pump turbine with variable-pitch blades is presented. A series of equations that describe the behavior of the unit during the transient period is found by interpolation of the unit’s characteristic. These equations are combined with the method of characteristic solution to the waterhammer equations to describe the behavior of an entire system during a transient period. A complete performance characteristic of a variable-pitch pump turbine is presented. Example problems which utilize this characteristic illustrate the method of analysis. The examples prove that the variation in pitch of a unit’s blades is very important in predicting the head across the unit, the discharge through the unit, and the speed of the unit during a transient period.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1967;89(4):558-566. doi:10.1115/1.3616734.

This paper contains a general review of the various methods which have been proposed for the estimation of basic slip factors for centrifugal impellers. As a result of this study, it is concluded that the classical method proposed by Busemann in 1929 is still the most generally applicable prediction for the basic slip factor of centrifugal impellers. The paper then presents a very simple empirical expression, which fits the Busemann results extremely well over the whole range of practical blade angles and number of blades up to a limiting inlet-to-outlet radius ratio for the impeller. An empirical correction factor is also proposed for conditions which exceed this limiting radius ratio. Tabular comparisons of slip factors, with test data (where available), are given for over 60 pump and compressor impellers which have been cited previously in the literature, and the author has added data for several more compressor stages from his own experience.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1967;89(4):573-576. doi:10.1115/1.3616741.

Severe vibration of a hydraulic turbine was found to be self-excited. Vibration at the natural frequency when operating at synchronous speed produced self-sustaining whirl of the shaft. Gyroscopic action of the turbine runner caused the vibration to be self-excited. Admission of relatively small amounts of compressed air to the region between the headcover baffle plate and the crown of the runner stopped the vibration by preventing buildup of a rotating pressure field.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1967;89(4):577-586. doi:10.1115/1.3616742.

A model is developed for analytically determining pump inducer performance in both the single-phase and cavitating flow regimes. An equation of state for vaporizing flow is used in an approximate, three-dimensional analysis of the flow field. The method accounts for losses and yields internal distributions of fluid pressure, velocity, and density together with the resulting overall efficiency and pressure rise. The results of calculated performance of two sample inducers are presented. Comparison with recent theory for fluid thermal effects on suction head requirements is made with the aid of a resulting dimensionless vaporization parameter.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1967;89(4):589-599. doi:10.1115/1.3616748.

Three rotors were tested, to study flow and performance across loaded axial-flow blade rows. Principal design parameters varied were flow coefficient (0.29 < φ < 0.45), blade loading parameter at tip (0.25 < Dt < 0.66), and hub-tip radius ratio (0.4 < rh /rt < 0.8). Overall and blade element performances under noncavitating flow conditions are discussed in detail. Comparisons between the measured, three-dimensional design parameters and those computed from two-dimensional cascade correlations are made. A limited amount of performance obtained during operation of the rotors in unstable flow and cavitating flow conditions is presented.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1967;89(4):600-604. doi:10.1115/1.3616750.

A technique for numerically evaluating pumping system effectiveness on the basis of statistical analysis is presented. The technique is applied to a hypothetical substitution of stainless pump wear rings for bronze to find if the probable increase in quantity of water delivered annually compares favorably with the operational cost difference between the materials. Other applications for this decision-making device are briefly described.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1967;89(4):605-612. doi:10.1115/1.3616751.

An experimental investigation of the effect of groove geometry on the performance of the grooved-shaft viscoseal is being conducted. Using distilled water as the sealed fluid, the concentric and eccentric performance of ten seals has been determined under laminar and turbulent conditions. An approximate method is devised to predict the empirical factors in the turbulent sealing equation. The findings reveal that the optimum seal geometry for laminar operation is not optimum for turbulent conditions, the seal eccentricity has slight effect on performance, and the phenomenon of air ingestion may present a major problem in the application of the viscoseal.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1967;89(4):615-620. doi:10.1115/1.3616754.

Steady-oscillatory flow, such as that produced by reciprocating pumps, can be analyzed using impedance methods including friction. The actual pulsating flow produced by the pump is combined with the elastic and geometric characteristics of the piping system in the analysis. Fluid compressibility is included in both the pump and pipe system analysis. Experimental confirmation of the theory is given.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1967;89(4):621-627. doi:10.1115/1.3616755.

In some pumping plants several one-way surge tanks are installed to prevent water-column separation in the discharge line caused by failure of power to pumps. This paper describes a method of analysis of waterhammer in a pump system of this type. The analysis is carried out by solving the fundamental equations by a digital computer. An example is calculated and the results are compared with the measurements.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

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