bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic Analysis Technique of Rotating Centrifugal Impeller
Authors: Zhang Jin , Chen X. J. , Wang W. L. 
Published: March 2015

A dynamic analysis technique which can be employed in rotating centrifugal impeller is presented in this paper. It shows that multi–component partition can be made in repetitive sector region of the centrifugal impeller. The basic repectivie sector region of the centrifugal impeller is divided into three substructures: the full blade, the short blade and the sectorial part of the disc. By using Benfield mode substitution combined with group transformation successfully, the Hermite generalized mass and stiffness matrices under the reduced coordinates are derived. From this, the natural frequencies and the corresponding modal shapes of the bladed disc coupled system can be solved.
The comparison of the analytical results obtained by using this method, other methods and the experimental data of models verifies the reliability, practicability and considerable economic benefits of the method presented in this paper.
Measurement and Prediction of Heat Transfer From Compressor Discs With a Radial Inflow of Cooling Air
Authors: Farthing P. R. , Long C. A. , Rogers R. H. 
Published: March 2015

An integral theory is used to model the flow, and predict heat transfer rates, for corotating compressor discs with a superposed radial inflow of air. Measurements of heat transfer are also made, both in an experimental rig and in an engine.
The flow structure comprises source and sink regions, Ekman-type layers and an inviscid central core. Entrainment occurs in the source region, the fluid being distributed into the two nonentraining Ekman-type layers. Fluid leaves the cavity via the sink region.
The integral model is validated against the experimental data, although there are some uncertainties in modelling the exact thermal conditions of the experiment. The magnitude of the Nusselt numbers is affected by the rotational Reynolds number and dimensionless flowrate; the maximum value of Nu is found to occur near the edge of the source region.
The heat transfer measurements using the engine data show acceptable agreement with theory and experiment. This is very encouraging considering the large levels of uncertainty in the engine data.
Effects of the Tip Clearance Flow Field on the Secondary Losses
Authors: Kaldellis J. K. , Katramatos D. T. , Ktenidis P. D. 
Published: March 2015

In this paper an extension of our secondary flow calculation method is presented in order to estimate the influence of the tip clearance on the secondary flow field.
The impact of the tip clearance vortex is embodied in the method so that the secondary vorticity field, based on the complete form of the meridional vorticity transport equation is properly modified. In this way the changes of the secondary flow field quantities are predicted along with the resulting additional losses imposed by the existence of the tip clearance.
The estimated tip clearance losses, based on the flow field structure, are compared to results obtained from various semi-empirical loss correlations found in the literature.
Several cases encountered in axial flow compressor configurations are investigated and the calculated results are favourably compared to experimental data and results of previous calculations.
Additionally, in order to clarify the influence of the tip clearance structure upon the secondary flow field, cases with and without tip clearance are also examined.
A Viscous Flow Study of Shock-Boundary Layer Interaction, Radial Transport, and Wake Development in a Transonic Compressor
Authors: Hah Chunill , Reid Lonnie 
Published: March 2015

A numerical study based on the three-dimensional Reynolds-averaged Navier-Stokes equation has been conducted to investigate the detailed flow physics inside a transonic compressor. Three-dimensional shock structure, shock-boundary layer interaction, flow separation, radial mixing, and wake development are all investigated at design and off-design conditions. Experimental data based on laser anemometer measurements are used to assess the overall quality of the numerical solution. An additional experimental study to investigate endwall flow with a hot-film was conducted, and these results are compared with the numerical results.
Detailed comparison with experimental data indicates that the overall features of the three-dimensional shock structure, the shock-boundary layer interaction and the wake development are all calculated very well in the numerical solution. The numerical results are further analyzed to examine the radial mixing phenomena in the transonic compressor. A thin sheet of particles is injected in the numerical solution upstream of the compressor. The movement of particles is traced with a three-dimensional plotting package. This numerical survey of tracer concentration reveals the fundamental mechanisms of radial transport in this transonic compressor. Strong radially outward flow is observed inside a separated flow region and this outward flow accounts for about 80 percent of the total radial transport. The radially inward flow is mainly due to the traditional secondary flow.
Computation of 3D Flow Phenomena in Axial Flow Compressor Blade Rows
Authors: Janssen M. , Dohmen H.-J. , Grahl K. G. 
Published: March 2015

The main subject of the present publication is the comparison of results achieved with a 3D-partially parabolic calculation procedure and experimental data for the three dimensional flow in stationary and rotating blade rows of axial flow compressors.
To set up the numerical solution procedure, the Navier-Stokes Equations are written in finite difference form by applying the control-volume approach. The turbulent flow effects are taken into account by using the standard k—ε model for the calculation of the turbulent viscosity. For precisely introducing the boundary conditions for arbitrary geometries, the differential equations are transformed to a body-fitted coordinate system by a very simple method. To construct the physical mesh, the nonorthogonal curvilinear coordinates are taken as solutions of a suitable elliptic boundary value problem.
The abilities of the developed computer program are shown by comparing experimental and numerical results for three applications. The first, most simple case deals with the flow development in an isolated, stationary blade row of cylindrical blades and uniform boundary conditions upstream of the blade row. A more complex flow is regarded by calculating the flow field through highly turned, custom tailored airfoils working in a multistage environment. The flow conditions upstream of the flow domain under consideration show a well developed end wall boundary layer at the hub, leading to a strongly skewed inflow due to the superimposed tangential velocity component of the rotor upstream. The third application regards the flow development in a rotating axial compressor blade row in which the complexity of the flow field increases by flow effects that are due to centrifugal and Coriolis forces.
The comparisons between experimental and numerical results show good agreements for all applications.
A Finite Element Inverse Method for the Design of Turbomachinery Blades
Authors: Nicoud Didier , Bloa Catherine Le , Jacquotte Olivier-Pierre 
Published: March 2015

We present a quasi-3D inverse method for the design of turbomachinery blades corresponding to a velocity distribution given arbitrarily. The theoretical aspect of the problem is first investigated, then the equations governing the quasi three-dimensional potential model are reviewed. The inverse method consists of solving the potential equation with Dirichlet boundary conditions on the profile, then modifying the profile iteratively until there is no mass flux through its surface. The convergence of the process is guaranteed by the preliminary theoretical study. The method is implemented using a finite element discretization, which relies on a mixed variational formulation involving two fields of unknowns: the velocity potential and the normal displacement of the profile.
Several results are shown on subsonic and transonic compressor profiles. The modified profiles are then validated with direct calculations such as quasi three-dimensional Navier-Stokes computations. These results illustrate the behavior of the method, in particular its robustness and its effectiveness.
The method was adapted to calculations on turbine blade profiles. Preliminary results are shown that illustrate an industrial use of the method on a subsonic profile.
Life Time Prediction for Ceramic Gas Turbine Components
Authors: Stürmer G. , Schulz A. , Wittig S. 
Published: March 2015

At the Institute for Thermal Turbomachinery, University of Karlsruhe (ITS), theoretical and experimental investigations on ceramic gas turbine components are performed. For the reliability analysis by finite element calculations the computer code CERITS has been developed. This code is used to determine the fast fracture reliability of ceramic components subjected to polyaxial stress states with reference to volumetric flaws and was presented at the 1990 IGTI Gas Turbine Conference.
CERITS-L now includes subcritical crack growth. With the new code CERITS-L, failure probabilities of ceramic components can be calculated under given load situations versus time. In comparing these time dependent failure probabilities with a given permissible failure probability, the maximum operation time of a component can be determined. The considerable influence of the subcritical crack growth upon the life time of ceramic components is demonstrated at the flame tube segments of the ITS ceramic combustor.
Experimental Investigation of the Longitudinal-Vortex-Nature of Rotating Stall in Vaneless Diffusers of Centrifugal Compressors
Authors: Chen Y. N. , Haupt U. , Seidel U. , Rautenberg M. 
Published: March 2015

Rotating stall in a vaneless diffuser of a centrifugal compressor has been found to be guided by Rossby waves, which are composed of branches of high and low pressures (Chen, Haupt and Rautenberg, 1990a). The branch of the high pressure leads the unstalled region and that of the low pressure leads the stalled region. The phase velocity of the Rossby waves is then the pattern speed of the stall cell.
We report here an additional experimental result, according to which the flow of rotating stall is composed of a longitudinal spiral vortex pair. The vorticity and the axis of the longitudinal vortex were measured by means of two pressure transducers fixed at a distance of 2 mm to the opposite walls of the diffuser downstream of its inlet.
The analysis of the experimental result of Tsurusaki, Imaichi and Miyake (1987) about the fields of the total and fluctuating velocities of rotating stall in the vaneless diffuser reveals furthermore that the longitudinal spiral vortex is centred on the through flow. The two vortices of the pair stay side by side in touch but without mixing because of their opposite rotational sense. The longitudinal vortices make about 1 1/4 turns from the inlet to the outlet of the diffuser under the guidance of the Rossby waves. The vorticity of the longitudinal vortex is determined from the experimental result.
Furthermore, the experimental result reveals that the fronts along the high pressure ridges and the low pressure troughs of the Rossby wave pattern are themselves longitudinal vortices. Then these fronts possess a behaviour of the jet stream, which is associated with the Rossby waves of the atmosphere in the midlatitude.
Finally, the origin of the vorticity of the longitudinal vortices along the through flow and the Rossby-wave front is derived based on the experimental results obtained by Hergt and Jaberg (1988), and Hide (1958).
Impact Design Methods for Ceramic Components in Gas Turbine Engines
Authors: Song J. , Cuccio J. , Kington H. 
Published: March 2015

Garrett Auxiliary Power Division of Allied-Signal Aerospace Company is developing methods to design ceramic turbine components with improved impact resistance. In an ongoing research effort under the DOE/NASA-funded Advanced Turbine Technology Applications Project (ATTAP), two different modes of impact damage have been identified and characterized: Local damage and structural damage.
Local impact damage to Si3N4 impacted by spherical projectiles usually takes the form of ring and/or radial cracks in the vicinity of the impact point. Baseline data from Si3N4 test bars impacted by 1.588 mm (0.0625 inch) diameter NC-132 projectiles indicates the critical velocity at which the probability of detecting surface cracks is 50 percent equalled 130 m/sec (426 ft/sec). A microphysics-based model that assumes damage to be in the form of microcracks has been developed to predict local impact damage. Local stress and strain determine microcrack nucleation and propagation, which in turn alter local stress and strain through modulus degradation. Material damage is quantified by a “damage parameter” related to the volume fraction of microcracks. The entire computation has been incorporated into the EPIC computer code. Model capability is being demonstrated by simulating instrumented plate impact and particle impact tests.
Structural impact damage usually occurs in the form of fast fracture caused by bending stresses that exceed the material strength. The EPIC code has been successfully used to predict radial and axial blade failures from impacts by various size particles. This method is also being used in conjunction with Taguchi experimental methods to investigate the effects of design parameters on turbine blade impact resistance. It has been shown that significant improvement in impact resistance can be achieved by using the configuration recommended by the Taguchi methods.
Fracture Mechanics Approach to Creep Crack Growth in Welded IN738LC Gas Turbine Blades
Authors: Foo Wan-P’ng , Castillo Rafael 
Published: March 2015

Microcracks caused by hot cracking or strain age cracking mechanisms are very likely to be discovered in the weld repair zone of precision cast IN738LC gas turbine blades. The possibility of crack propagation under the operating conditions of the gas turbine thereby becomes a crucial issue for gas turbine designers. The creep crack growth rate in air of the hipped and fully heat treated IN738LC was measured at the service temperature experienced by the first stage turbine blade tip. The corresponding growth behaviour was also studied.
The creep crack growth rate, da/dt, versus crack tip stress intensity factor, K1, a relation which exhibits the typical primary, secondary and tertiary behaviour, supports the applicability of K1 as an appropriate correlating parameter for the creep crack growth of this Ni-based superalloy under the loading conditions used in this study. Microstructural examination illustrated that the creep crack growth of IN738LC principally takes place by the nucleation, growth, coalescence and link-up of grain boundary microvoids and microcracks.
An excellent approximation of the stress intensity factor under service loading conditions in the vicinity of the crack tip was obtained by using the Westinghouse WECAN finite element analysis. It is shown that the crack tip stress intensity factor under normal loading conditions will not be able to drive the transverse through-the-wall-thickness blade tip crack in this study.
Integrated Weld Automation for Gas Turbine Blades
Authors: Lowden P. , Pilcher C. , Liburdi J. 
Published: March 2015

The automation of turbine blade welding provides both metallurgical benefits and production advantages. Heat-affected zone cracking in sensitive superalloys, such as IN738 and IN100, can be eliminated or greatly reduced by optimizing process control, and higher production yields can be achieved when welding jet engine blades.
However, the successful implementation of automated processes requires careful consideration and engineering of the technology package. In particular, the equipment packager must be experienced in the technology associated with turbine blade welding and incorporate appropriate tooling, measurement system, power source and robotic controls. An example of a welding system for high pressure blade tips is presented which required the development and integration of a novel vision system to measure the thickness of the squealer wall, in order to select the appropriate welding parameters. Several practical applications of the technology are demonstrated on turbine blades exhibiting typical dimensional and metallurgical variations.
Design of a Small Axial Compressor for High Efficiency Over a Wide Operating Range
Authors: Reynolds B. , Etter S. , Torony J. , O’Connor J. 
Published: March 2015

Textron Lycoming’s advanced compressor design system has been used to design and develop a three-stage axial compressor in the small flow class (less than 10 pps). New and innovative aerodynamic and mechanical design features identified in recent technology programs were used to optimize efficiency and range in the present design. Specific areas of technology development in this research program are: customized rotor airfoil shapes for minimum shock loss, airfoil endwall loading selected to reduce losses, variable geometry design for large range and high efficiency compressor operating requirements, variable stator hub contours and attachment design for minimum clearance loss, flowpath sealing for low leakage flow, and reduced frictional pumping losses. Performance objectives were experimentally verified with extensive prototype rig testing where sufficient instrumentation was installed to identify overall and individual stage operating charactertistics.
A complete description of the axial compressor aerodynamic design is presented; executed using meanline, axisymmetric and three-dimensional flow analysis. Elements of the mechanical design that impact overall performance potential were controlled in the design and are described. Mechanical integrity for rig development and engine operation were verified for all components of the design and are reviewed.
3-D Axisymmetric Viscous Internal Flows on Rotating and Stationary Surfaces in Turbomachines
Authors: Ktenidis P. D. , Kaldellis J. K. 
Published: March 2015

A fast calculation method, able to predict three, dimensional axisymmetric viscous internal flows on rotating and stationary surfaces in turbomachinery components has been developed. Modern high bypass turbine engines are characterized by axisymmetric parts such as inlets, nacelles, the prediffuser whose primary function is the efficient transfer of flow from one component to another. The flow field in such ducts are characterized by streamline curvature and divergence resulting from sharp contour and rapid area rotations, with the appearance of high peripheral velocity components.
The detailed calculation of the flow field through the axisymmetric parts requires a solution of the three-dimensional Navier-Stokes equations. However, conventional design systems simplify the flow pattern to a two dimensional one. The proposed method is based on the two-zone model and uses the notions of the integral formulation for the meridional direction. The meridional vorticity transport differential formulation, in a modified form is used for the peripheral direction to include the dynamics of passing from stationary to rotating parts and vice-versa. The resulting algorithms are sufficiently versatile and reliable to be used as a part of a design system for industrial applications.
A series of test cases demonstrate the applicability of the proposed method to practical problems having moderate skew, sudden application of a transverse motion and moderate cross-sectional area variations with stationary or rotating boundaries.
Film Cooling Research on the Endwall of a Turbine Nozzle Guide Vane in a Short Duration Annular Cascade: Part 2 — Analysis and Correlation of Results
Authors: Harasgama S. P. , Burton C. D. 
Published: March 2015

Results have been presented on the heat transfer characteristics of the film cooled endwall (platform) of a turbine nozzle guide vane in an annular cascade at engine representative conditions in a companion paper by Harasgama and Burton (1991). The present paper reports on the analysis of these measurements.
The experimental results are well represented by the superposition theory of film cooling. It is shown that high cooling effectiveness can be achieved when the data are corrected for axial pressure gradients. The data are correlated against both the slot-wall jet parameter and the discrete hole injection function for flat-plate, zero pressure gradient cases. The pressure gradient correction brings the present data to within ± 11% of the discrete hole correlation. Preliminary predictions of heat transfer reduction have been carried out using the STANCOOL program. These indicate that the code can predict the magnitude of heat transfer reduction correctly, although the absolute values are not in good agreement. This is attributed to the three-dimensional nature of the flow at the endwall.
Validation of a Numerical Method for Unsteady Flow Calculations
Authors: Giles Michael , Haimes Robert 
Published: March 2015

This paper describes and validates a numerical method for the calculation of unsteady inviscid and viscous flows. A companion paper compares experimental measurements of unsteady heat transfer on a transonic rotor with the corresponding computational results. The mathematical model is the Reynolds-averaged unsteady Navier-Stokes equations for a compressible ideal gas. Quasi-three-dimensionality is included through the use of a variable streamtube thickness. The numerical algorithm is unusual in two respects: a) for reasons of efficiency and flexibility it uses a hybrid Navier-Stokes/Euler method, and b) to allow for the computation of stator/rotor combinations with arbitrary pitch ratio a novel space-time coordinate transformation is used.
Several test cases are presented to validate the performance of the computer program, UNSFLO. These include: a) unsteady, inviscid flat plate cascade flows, b) steady and unsteady, viscous flat plate cascade flows, c) steady turbine heat transfer and loss prediction. In the first two sets of cases comparisons are made with theory, and in the third the comparison is with experimental data.
Development of a Natural Gas-Fired, Ultra-Low NOx Can Combustor for an 800 KW Gas Turbine
Authors: Smith K. O. , Holsapple A. C. , Mak H. K. , Watkins L. 
Published: March 2015

The experimental results from the rig testing of an ultra-low NOx, natural gas-fired combustor for an 800 to 1000 kw gas turbine are presented. The combustor employed lean-premixed combustion to reduce NOx emissions and variable geometry to extend the range over which low emissions were obtained.
Testing was conducted using natural gas and methanol. Testing at combustor pressures up to 6 atmospheres showed that ultra-low NOx emissions could be achieved from full load down to approximately 70% load through the combination of lean-premixed combustion and variable primary zone airflow.
Transonic Cascade Flow Prediction Using the Navier-Stokes Equations
Authors: Arnone A. , Stecco S. S. 
Published: March 2015

This paper presents results which summarize the work carried out during the last three years to improve the efficiency and accuracy of numerical predictions in turbomachinery flow calculations.
A new kind of non-periodic C-type grid is presented and a Runge-Kutta scheme with accelerating strategies is used as a flow solver.
The code capability is presented by testing four different blades at different exit Mach numbers in transonic regimes. Comparison with experiments shows the very good reliability of the numerical prediction. In particular the loss coefficient seems to be correctly predicted by using the well-known Baldwin-Lomax turbulence model.