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RESEARCH PAPERS

J. Eng. Power. 1975;97(2):145-152. doi:10.1115/1.3445931.

ASME Performance Test Code Committee No. 18 on Hydraulic Prime Movers is currently engaged in writing the first edition of a performance test code for the pumping cycle of reversible pump/turbines, after which it will undoubtedly update the 1949 performance test code for hydraulic turbines to be used also for the turbine cycle of pump/turbines. As members of the Canadian and United States national advisory groups, most of the ASME PTC-18 committee are also involved in the work of Technical Committee No. 4 on Hydraulic Turbines of the International Electrotechnical Commission for which the United States maintains the Secretariat with ASME as sponsor. The international codes for field acceptance tests of hydraulic turbines (IEC Publication 41-1963) and storage pumps (IEC Publication 198-1966) are currently in the process of being reworked and updated for combination into a single publication (or a coordinated set). Consequently, the subject material of this paper is now under world-wide discussion. The paper outlines the need for a universally-accepted method of determining field test inaccuracies or uncertainties. It suggests new testing procedures, suitable for statistical analysis, plus laboratory research on, and painstaking technical analysis of, each method of flow measurement. Until more accurate procedures are developed for the measurement of large water flow rates, the “best possible” test cannot justify the use of the best available instruments and techniques for measurement of hydraulic head and electrical power. Since the current state-of-the-art of field testing large hydraulic machines results in a sizable uncertainty in efficiency, this fact must be recognized by both parties to an equipment contract, and the commercial method of dealing with it should be carefully delineated in the purchase specifications.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1975;97(2):163-168. doi:10.1115/1.3445946.

Development of a more satisfactory method of estimating deviation angles was attempted using analytical procedures. Solutions for inviscid, irrotational flow in the blade-to-blade plane were obtained with a finite-difference calculation method. Deviation angles for three cascades with rounded trailing edges were estimated using the inviscid flow solutions and four existing trailing edge hypotheses. The estimated deviation angles were compared with experimental values for a range of incidence angle and inlet flow angle. None of the hypotheses were satisfactory at all incidence angles for all the cascades considered. An alternative hypothesis is presented which is suitable for one of the cascade profiles over a range of incidence and blade setting angle.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1975;97(2):173-177. doi:10.1115/1.3445951.

A series of tests has been carried out on a specially designed airblast atomizer in which the liquid is first spread into a thin sheet and then subjected on both sides to the atomizing action of high velocity air. The primary aim of the invesitgation was to examine the influence on mean drop size of liquid viscosity, surface tension and density. The liquids employed represented a range of values of surface tension from 26 to 73 dynes/cm, while viscosity and density were varied between 1.3 and 124 centipoise and 0.8 and 1.8 gm / cm3 , respectively. Atomizing air velocities covered the range of practical interest to the designers of continuous combustion systems and varied between 60 and 125 m/sec. Analysis of the experimental data showed that they could be described to a reasonable order of accuracy by the following empirical expression:

SMD = 521 Va−1 · σ0.5
  · ρ0.75 (1 + WlWa)
  + 0.037 η0.85(σρ)1.2
  (1 + WlWa)2

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1975;97(2):180-187. doi:10.1115/1.3445954.

This paper deals with the deformation and the stress of an axial flow compressor rotor blade under the loading of centrifugal forces. Coupled deformation of extension, bending, torsion and transverse shear of a pretwisted curved bar with arbitrary cross section is considered. Governing equations derived by means of the principle of virtual work are solved numerically by finite difference method. The warping functions used in the analysis were obtained by the use of finite element method. Measurement of the untwist angles and the stresses were carried out for the verification of the numerical analysis and they were found to be in good agreement.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1975;97(2):189-194. doi:10.1115/1.3445957.

For operation of a gas turbine in single-cycle arrangement with a high-temperature reactor, rupture of a main circuit pipe has to be included in the safety considerations. In the event of such an accident there may be a back flow through the turbo machines or a forward flow up to the choking limit. This paper is a report on tests carried out in a two-dimensional cascade wind tunnel on turbine cascades under back flow conditions. By the example of three selected representative cascades the characteristic features in turbine cascades with back flow are discussed. These cascades are a rotor blade tip section with aerofoil-like profiles and a wide pitch, a stator blade or rotor blade mean section with an usual deflection and a rotor blade root section with a narrow pitch and a large deflection.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1975;97(2):195-204. doi:10.1115/1.3445958.

A dissipation integral boundary layer method is briefly presented which serves as the basis of the optimization. The principles of optimum deceleration are explained. Following these principles the optimum boundary layer development is specified and the velocity distribution follows from the boundary layer equation. The corresponding shape is obtained from a potential method. It is found that the straight channel and conical diffusers do have a boundary layer development close to the optimum one and it is not worth to improve their performances by wall shaping. Two conical diffusers at high inlet Mach number are anaylzed and the predictions agree satisfactorily with the experiment.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1975;97(2):207-212. doi:10.1115/1.3445963.

The velocity field was measured in a rotating passage of a radial impeller with backward curved blades. Two versions were tested, one with an attached rotating shroud and the other with clearance between the blades and a stationary shroud surface. The distribution of velocity in the passage direction was similar in the two versions, but the pattern of cross-passage velocity in the unshrouded impeller configuration was altered strongly by the tip leakage flow entering the passage.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1975;97(2):214-224. doi:10.1115/1.3445966.

A method is proposed for predicting the behavior of a turbulent boundary layer with heat transfer under the influence of transpiration with discrete jets. The boundary layer is treated as a laterally averaged flow and the effects of nonuniformity are introduced through additional momentum and energy source terms in the equations of motion. These nonuniformity interaction terms are obtained using solutions of a set of ordinary differential equations governing the trajectory of jets. The effects of interaction between the jet and boundary layer turbulence structure are also treated. The predictions of the theory are shown to compare well with available discrete jet-boundary layer data.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1975;97(2):225-230. doi:10.1115/1.3445969.

An introduction to the fundamentals of turbine engine multiple fault diagnosis and its relationship to engine parameter selection and measurement requirements is presented. The influence of the type (thermodynamic cycle) of the engine to be diagnosed, and the nature of its expected problems, on the required parameters and the attendant measurement repeatability requirements are discussed.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1975;97(2):231-242. doi:10.1115/1.3445970.

Experimental testing of a model free-rotating vaneless diffuser, for application to high pressure ratio single-stage centrifugal compressors, was conducted to determine diffuser performance under braked and free rotating conditions at entry Mach numbers up to unity. The experimental test rig comprised a swirl generating nozzle upstream of the model vaneless diffuser rotor with an outer-to-inner diameter ratio of 1.3. Additional downstream diffusion was completed with stationary vaneless and vaned diffuser inserts. A significant improvement in diffuser performance was achieved under free-rotating conditions even though large wakes generated by upstream stationary swirl nozzles were present. Overall static pressure recovery for the complete diffusion system increased approximately 20 percent at free-rotating conditions corresponding to a tangential velocity ratio (diffuser rotor/incident stream) of 0.43.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1975;97(2):245-253. doi:10.1115/1.3445973.

Results of an experimental research on the comparison of flow patterns in linear and annular, fixed and rotating supersonic blade cascades are presented. The fixed plane cascade and the fixed annular cascade give very similar results at low back pressure and the flow configuration (Schlieren pictures) and the pressure distributions are those given by theoretical calculations. In the rotating cascade the fully started supersonic regime was not obtained. At high back pressure, sidewall flow separation perturbates the flow pattern in the plane cascade. In the annular setups, the flow configuration with suction side flow separation is correctly predicted by the theory.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1975;97(2):254-260. doi:10.1115/1.3445976.

Optical setups have been designed and built at ONERA to visualize aerodynamic flows within a fixed annular cascade, a supersonic axial compressor, and a supersonic centrifugal compressor. As these setups work by reflection on the metallic surfaces carrying the blades, special devices had to be devised for each installation. In rotating machines, the rapid evolution of the phenomena necessitates, for image recording, the use of strotoscopic synchronization devices, of fast, flash-synchronized cameras, of electronic shutters and of flash lamps. The schlieren visualization of the flow, made possible by these devices, is a precious tool to define more compact machines with high compression rates and minimum losses.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1975;97(2):261-273. doi:10.1115/1.3445978.

Testing over a range of Reynolds numbers was done for three NACA 65 Profiles in cascade. The testing was carried out in the VKI C-1 Low Speed Cascade Wind Tunnel; blade chord Reynolds number was varied from 250,000 to 40,000. A semiempirical theory is developed which will predict the behavior of the shear layer across a laminar separation bubble. The method is proposed for two-dimensional incompressible flow and is applicable down to short bubble bursting. The method can be used to predict the length of the laminar bubble, the bursting Reynolds number, and the development of the shear layer through the separated region. As such it is a practical method for calculating the profile losses of axial compressor and turbine cascades in the presence of laminar separation bubbles. It can also be used to predict the abrupt leading edge stall associated with thin airfoil sections. The predictions made by the method are compared with the available experimental data. The agreement could be considered good. The method was also used to predict regions of laminar separation in converging flows through axial compressor cascades (exterior to the corner vortices) with good results. For Reynolds numbers below bursting the semiempirical theory no longer applies. For this situation the performance of an axial compressor cascade can be computed using an empirical correlation proposed by the author. Comparison of performance prediction with experiment shows satisfactory agreement. Finally, a tentative correlation, based on the NACA Diffusion Factor, is presented that allows a rapid estimation of the bursting Reynolds number of an axial compressor cascade.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1975;97(2):275-281. doi:10.1115/1.3445982.

This paper presents a detailed analytical study of the dynamic stability of wing-mounted engine installations. Wing, nacelle, and mount system stiffness, inertia, and damping are considered in the dynamic modeling, and aerodynamic characteristics of the wing and propeller are included. Variations of these parameters and their interplay are investigated. Significant effects that are beyond the range of simplified methods have been identified. An estimate of the accuracy of predicted critical velocity is included. Also provided are recommendations for ground testing to support an analysis of this type.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1975;97(2):283-294. doi:10.1115/1.3445985.

The flow is calculated within the entire region from far upstream to far downstream of the blade rows and this not only between the blade rows but especially within the blade passages. It is assumed that the flow is steady, adiabatic, and inviscid. However, compressibility, blade forces in all directions, blade thickness, and total enthalpy gradients are taken into account. The shape of the meridional cross section can be arbitrary. The blades can be either cylindrical or twisted. The numerical solution is based on the finite-difference method. The discretization error, the stability error, and the iteration error of the numerical solution are determined.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1975;97(2):295-300. doi:10.1115/1.3445986.

Correlations are used by the engineer for design purposes and/or when a theoretical calculation is missing. The purpose of this paper is to show that, applying the momentum integral equation, it is possible to derive correlations for flow situations associated with a deceleration. Four different cases are presented in the paper: (a) The case of the profile losses in a cascade of blades; (b) the case of the secondary losses in a cascade of blades; (c) the case of the turbulent shear layer before reattachment in a laminar separation bubble; (d) the case of the interaction of a shock with a turbulent boundary layer. At the same time the important factors governing these flow situations are put into evidence.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

J. Eng. Power. 1975;97(2):188. doi:10.1115/1.3445955.
FREE TO VIEW
Abstract
Topics: Rotating blades
Commentary by Dr. Valentin Fuster
J. Eng. Power. 1975;97(2):188. doi:10.1115/1.3445956.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster

ERRATA

TECHNICAL BRIEFS

J. Eng. Power. 1975;97(2):301-303. doi:10.1115/1.3445987.
Abstract
Topics: Metals , Stress
Commentary by Dr. Valentin Fuster
J. Eng. Power. 1975;97(2):303-304. doi:10.1115/1.3445988.
Abstract
Commentary by Dr. Valentin Fuster

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