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At least 271 records · Page 15

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NASA NTRS1984

Study of stator-vane fluctuating pressures in a turbofan engine for static and flight tests

As part of a program to study the fan noise generated from turbofan engines, fluctuating surface pressures induced by fan-rotor wakes were measured on core- and bypass-stator outlet guide vanes of a modified JT15D-1 engine. Tests were conducted with the engine operating on an outdoor test stand and in flight. The amplitudes of pressures measured at fan-rotor blade-passage fundamental frequencies were generally higher and appeared less stable for the static tests than for the flight tests. Fluctuating pressures measured at the blade-passage frequency of the high-speed core compressor were interpreted to be acoustic; however, disturbance trace velocities for either the convected rotor wakes or acoustic pressures were difficult to interpret because of the complex environment.

Mueller, A. W.↗

NASA NTRS1984

Redesign and cascade tests of a supercritical controlled diffusion stator blade-section

A supercritical stator blade section, previously tested in cascade, and characterized by a flat-roof-top suction surface Mach number distribution, has been redesigned and retested. At near design conditions, the losses and air turning were improved over the original blade by 50 percent and 7 percent respectively. The key element in the improved performance was a small blade reshaping. This produced a continuous flow acceleration over the first one-third chord of the suction surface which successfully prevented a premature laminar separation bubble. Several recently available inviscid analysis and one fully viscous (Navier-Stokes) analysis code were used in the redesign process. The validity of these codes was enhanced by the test results.

Schmidt, J. F.↗

NASA NTRS1984

Nonlinear transient finite element analysis of rotor-bearing-stator systems

This paper extends the finite element scheme to handle the highly nonlinear interfacial fields generated in the fluid filled annulli of squeeze film and journal bearings so as to model the transient response of rotor-bearing-stator systems. Since such simulations are highly nonlinear, direct numerical integration schemes are employed to generate the overall response. In this context, the paper gives consideration to such items as (1) numerical efficiency/stability, (2) comparison of implicit and explicit schemes, (3) determines extent of response nonlinearity as well as (4) extensively benchmarks the overall concept/methodologies.

Padovan, J.↗

NASA NTRS1984

Redesign and cascade tests of a supercritical controlled diffusion stator blade-section

A supercritical stator blade section, previously tested in cascade, and characterized by a flat-roof-top suction surface Mach number distribution, has been redesigned and retested. At near design conditions, the losses and air turning were improved over the original blade by 50 percent and 7 percent, respectively. The key element in the improved performance was a small blade reshaping. This produced a continuous flow acceleration over the first one-third chord of the suction surface which successfully prevented a premature laminar separation bubble. Several recently available inviscid analysis codes and one fully viscous (Navier-Stokes) analysis code were used in the redesign process. The validity of these codes was enhanced by the test results. Previously announced in STAR as N84-22533

Schmidt, J. F.↗

NASA NTRS1985

Transient technique for measuring heat transfer coefficients on stator airfoils in a jet engine environment

A transient technique was used to measure heat transfer coefficients on stator airfoils in a high-temperature annular cascade at real engine conditions. The transient response of thin film thermocouples on the airfoil surface to step changes in the gas stream temperature was used to determine these coefficients. In addition, gardon gages and paired thermocouples were also utilized to measure heat flux on the airfoil pressure surface at steady state conditions. The tests were conducted at exit gas stream Reynolds numbers of one-half to 1.9 million based on true chord. The results from the transient technique show good comparison with the steady-state results in both trend and magnitude. In addition, comparison is made with the STAN5 boundary layer code and shows good comparison with the trends. However, the magnitude of the experimental data is consistently higher than the analysis.

Gladden, H. J.↗

NASA NTRS1985

Transient technique for measuring heat transfer coefficients on stator airfoils in a jet engine environment

Gladden, H. J.↗

NASA NTRS1986

Comparison of calculated and experimental cascade performance for controlled-diffusion compressor stator blading

The mid-span section of a previously reported controlled-diffusion compressor stator has been experimentally evaluated in cascade. Measurements are taken over a range of incidence angles for blade chord Reynolds numbers from 470,000 to 690,000. Blade chord length is 12.7 cm, aspect ratio is 2.0, and solidity is 1.67. Measurements include conventional cascade performance parameters as well as blade surface pressures. Computations are made for the inviscid flow field, surface boundary layers, and loss for several of the blade inlet angle conditions, are compared against corresponding data.

Sanger, N. L.↗

NASA NTRS1987

Measurements of the unsteady flow field within the stator row of a transonic axial-flow fan. 1: Measurement and analysis technique

This two-part paper presents laser anemometer measurements of the unsteady velocity field within the stator row of a transonic axial-flow fan. The objective is to provide additional insight into unsteady blade-row interactions within high speed compressors which affect stage efficiency, energy transfer, and other design considerations. Part 1 describes the measurement and analysis techniques used for resolving the unsteady flow field features. The ensemble-average and variance of the measured velocities are used to identify the rotor wake generated and unresolved unsteadiness, respectively. (Rotor wake generated unsteadiness refers to the unsteadiness generated by the rotor wake velocity deficit and the term unresolved unsteadiness refers to all remaining contributions to unsteadiness such as vortex shedding, turbulence, mass flow fluctuations, etc.). A procedure for calculating auto and cross correlations of the rotor wake generated and unresolved unsteady velocity fluctuations is described. These unsteady-velocity correlations have significance since they also result from a decomposition of the Navier-Stokes equations. This decomposition of the Navier-Stokes equations resulting in the velocity correlations used to describe the unsteady velocity field will also be outlined in this paper.

Suder, K. L.↗

NASA NTRS1986

Comparison of calculated and experimental cascade performance for controlled-diffusion compressor stator blading

Sanger, N. L.↗

NASA NTRS1987

Unsteady three-dimensional Navier-Stokes simulations of turbine rotor-stator interaction

Fluid flows within turbomachinery tend to be extremely complex. Understanding such flows is crucial to efforts to improve current turbomachinery designs, and the computational approach can be used to great advantage in this regard. This study presents a finite-difference, unsteady, thin-layer Navier-Stokes approach to calculating the flow within an axial turbine stage. The relative motion between the stator and rotor airfoils is made possible with the use of patched grids that move relative to each other. The calculation includes end-wall and tip-leakage effects. Results in the form of time-averaged surface pressures, pressure amplitudes (corresponding to the pressure fluctuation in time), near-surface velocity vectors, and pressure contours in the passage areas are presented. The numerical results are compared with experimental data wherever possible, and the agreement between the two is found to be good.

Rai, Man Mohan↗

NASA NTRS1985

Flow in a model turbine stator

In view of the complex nature of the flowfield in the hot section of gas turbine engines, the need to predict heat transfer and flow losses, the possible appearance of separation and strong secondary flows, etc., the present effort is focusing upon a Navier-Stokes approach to the three dimensional turbine stator problem. The advantages of a full Navier-Stokes approach are clear since when combined with a suitable turbulence model these equations represent the flow and heat transfer physics. In particular, the Navier-Stokes equations accurately represent possible separated regions and regions of significant secondary flow. In addition, the Navier-Stokes approach allows representation of the entire flow field by a single set of equations, thus avoiding problems associated with representing different regions of the flow by different equations and then matching flow regions.

Buggeln, R. C.↗

NASA NTRS1987

Measurements of the unsteady flow field within the stator row of a transonic axial-flow fan. I - Measurement and analysis technique

This two-part paper presents laser anemometer measurements of the unsteady velocity field within the stator row of a transonic axial-flow fan. The objective is to provide additional insight into unsteady blade-row interactions within highspeed compressors which affect stage efficiency, energy transfer, and other design considerations. Part 1 describes the measurement and analysis techniques used for resolving the unsteady flow field features. The ensemble-average and variance of the measured velocities are used to identify the rotor wake generated and unresolved unsteadiness, respectively. (Rotor wake generated unsteadiness refers to the unsteadiness generated by the rotor wake velocity deficit and the term unresolved unsteadiness refers to all remaining contributions to unsteadiness such as vortex shedding, turbulence, mass flow fluctutions, etc.). A procedure for calculating auto and cross correlations of the rotor wake generated and unresolved unsteady velocity fluctuations is described. These unsteady-velocity correlations have significance since they also result from a decomposition of the Navier-Stokes equations. This decomposition of the Navier-Stokes equations resulting in the velocity correlations used to describe the unsteady velocity field will also be outlined in this paper.

Suder, K. L.↗

NASA NTRS1988

Rotor-stator interaction in a diffuser pump

Steady and unsteady pressure measurements were obtained on the diffuser vanes and the shroud wall of vaned and vaneless diffuser pumps in order to investigate the rotor-stator interaction. It is shown that the magnitude of the fluctuating lift is greater than the steady lift, and that the pressure fluctuations are larger on the suction side than on the pressure side. Pressure fluctuations near the shroud were much smaller than those near the hub across the span of the vane. Pressure fluctuations on the shroud wall itself were found to be larger for the vaned diffuser than for the vaneless diffuser.

Acosta, A. J.↗

NASA NTRS1986

Turbine stator flow field simulations

The increased capability and accessibility of modern computers, coupled with increasingly sophisticated and accurate numerical and physical modeling, has led to a marked impact of numerical simulations upon current turbine design and research problems. The turbine section represents a considerable challenge as it contains significant regions of complex three-dimensional flow, including both aerodynamic and heat transfer phenomena. The focus of the present effort is the development of an efficient and accurate three-dimensional Navier-Stokes calculation procedure for application to the turbine stator and rotor problems. In particular, an effective procedure is sought which: (1) adequately represents the flow physics, (2) allows for sufficient resolution in regions of small length scale, and (3) has sufficiently good convergence properties so as to allow use on a regular basis.

Buggeln, R. C.↗

NASA NTRS1989

Multi-blade Navier-Stokes simulations of rotor-stator interaction in a turbine stage

Turbulent flow fields of multiblade rotor/stator configurations in a turbine stage for the high pressure fuel side turbopump of the space shuttle main engine are obtained using a computer program that can simulate flows in a stage with an unequal number of rotor and stator blades. The calculations are performed on a system of multiple patched and overlaid grids using the unsteady, thin-layer Navier-Stokes equations in two-dimension. Aerodynamic performance of two rotor/stator configurations are studied and compared in the form of pressure contours, Mach number contours, time averaged surface pressure, and unsteady pressure amplitude. Spatial and temporal accuracy of flow calculations along with computation cost are evaluated for the purpose of engineering design applications.

Lin, S. J.↗

NASA NTRS1990

Rubbing Between Rotors And Stators

Report describes experimental and numerical-simulation studies of dynamical effects of rubbing between rotors and stators in turbomachinery. Purpose of study to gain improved understanding of such rubbing phenomena, with view toward: contributing to techniques for diagnosis of rubbing (e.g., via analysis of vibrations); predicting more accurately limiting operating conditions; and improving design criteria to prevent rubbing damage in high-performance rotating machinery.

Muszynska, Agnes↗

NASA NTRS1990

A kinematical/numerical analysis of rotor-stator interaction noise

In this study, the unsteady, thin-layer Navier-Stokes equations are solved using a system of patched grids for a rotor-stator configuration of an axial turbine. The study examines the plurality of spinning modes that are present in such an interaction. The propagation of these modes is analyzed and appropriate grid spacing chosen in the far upstream and downstream regions to attenuate reflections from the computational boundaries. In addition, radiating boundary conditions are implemented based on the farfield acoustical behavior of the flow field. Results in the form of pressure amplitudes and the spectra of turbine tones are presented. Numerical results and experimental data are compared wherever possible. The numerical results are also shown to conform with the predictions of a kinematical analysis of the flowfield.

Rangwalla, Akil A.↗

NASA NTRS1990

Experimental investigation of rotor-stator interaction in a centrifugal pump with several vaned diffusers

Steady and unsteady diffuser vane pressure measurements have been conducted with a two-dimensional test impeller, in an experimental investigation of rotor-stator interaction within a centrifugal pump having several vaned diffusers, under conditions of different flow coefficients and different radial gaps between the impeller blade trailing edge and the diffuser vane leading edge. 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. Increasing the number of diffuser vanes was found to result in a significant decrease of impeller blade pressure fluctuations.

Arndt, N.↗