bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Novel Technique for the Measurement of Blade Damping Using Piezoelectric Actuators
Authors: Jeffers T. R. , Kielb J. J. , Abhari R. S. 
Published: August 2014

Reducing damage to turbomachinery blades due to high cycle resonant excitation is an important engineering challenge facing the engine design community. To minimize peak resonant stresses, designers attempt to reduce the forcing function and increase structural and aerodynamic damping. For higher frequency modes in particular, understanding of blade damping has been a challenge, due in part to a lack of detailed experimental measurements. The focus of this paper is on the description and validation of a novel experimental technique for the measurement of damping in turbomachinery blades.
The technique utilizes a continuously powered piezoelectric actuator embedded within the structure of the blade to excite a range of structural modes, while monitoring the structural response by the use of strain gage transducers. A novel data reduction technique is developed in order to 1) minimize the contamination of the strain gage output from the piezoelectric high voltage electrical field and to 2) efficiently obtain an accurate measure of the critical damping ratio and resonant frequency. The range of applicability and practical limitations of the technique is explored through a detailed uncertainty analysis.
Three different case studies were investigated to show the application of the technique including: a cantilever plate, broach block mounted turbine blades, and rotating turbine blades mounted in a rotor disk. Two different blade geometries were analyzed using full-scale engine hardware in a high speed rotating blade-disk assembly. Future papers will present more detailed results obtained from numerous spin tests that have been completed to date using the technique presented here.
The Impact of Viscous Effects on the Aerodynamic Damping of Vibrating Transonic Compressor Blades — A Numerical Study
Authors: Grüber Björn , Carstens Volker 
Published: August 2014

A parametric study which investigates the influence of viscous effects on the damping behaviour of vibrating compressor cascades is presented here.
To demonstrate the dependence of unsteady aerodynamic forces on the flow viscosity, a computational study was performed for a transonic compressor cascade of which the blades underwent tuned pitching oscillations while the flow conditions extended from fully subsonic to highly transonic flow. Additionally, the reduced frequency and Reynolds number were varied. In order to check the linear behavior of the aerodynamic forces, all calculations were carried out for three different oscillation amplitudes. Comparisons with inviscid Euler results helped identify the influence of viscous effects.
The computations were performed with a Navier-Stokes code, the basic features of which are the use of an AUSM upwind scheme, an implicit time integration, and the implementation of the Baldwin-Lomax turbulence model. In order to demonstrate the possibility of this code to correctly predict the unsteady behavior of strong shock-boundary layer interactions, the experiment of Yamamoto and Tanida on a self-induced shock oscillation due to shock-boundary layer interaction was calculated. A significant improvement in the prediction of the shock amplitude was achieved by a slight modification of the Baldwin Lomax turbulence model.
An important result of the presented compressor cascade investigations is that viscous effects may cause a significant change in the aerodynamic damping. This behaviour is demonstrated by two cases in which an Euler calculation predicts a damped oscillation whereas a Navier-Stokes computation leads to an excited vibration. It was found that the reason for these contrary results are shock-boundary-layer interactions which dramatically change the aerodynamic damping.
Multilevel Optimization of Rotor Bearing System With Dynamic Behavior Constraints
Authors: Shiau T. N. , Lee H. J. , Tsai Y. J. 
Published: August 2014

The main purpose of this study is to investigate the multilevel optimization of rotor-bearing systems. The design variables include the shaft inner radius, the bearings stiffness, and the axial position of the bearings and disks. The design objectives are minimization of the shaft weight and transmitted force to the bearings. Constraints are placed on the critical speeds, the maximum shaft bending stress, and the maximum amplitude of the steady state response.
In the multilevel optimization, three levels are considered and each level includes a single objective and/or multiobjective with various design variables and constraints. For each level, the method of feasible direction (MFD) is used. In addition, the weighting method (WM) is used for multiobjective optimization. The dynamic analysis is carried out using the generalized polynomial expansion method.
The results show that the shaft weight and transmitted forces can be simultaneously reduced with the multilevel technique and are better than those obtained using the multiobjective optimization technique with only a single level.
Comparative Studies on Short and Long Length-Scale Stall Cell Propagating in an Axial Compressor Rotor
Authors: Inoue M. , Kuroumaru M. , Tanino T. , Yoshida S. , Furukawa M. 
Published: August 2014

In a low-speed compressor test rig at Kyushu University, multiple short length-scale stall cells appeared under a mild stall condition and turned into a long length-scale cell under a deep stall condition. Then, for the both types of stall cell, the pressure distribution on the casing wall and the velocity distributions upstream and downstream of the rotor have been measured by high response pressure transducers and a slanted hot-wire, respectively. The time-dependent ensemble averages of these distributions have been obtained phase-locking to both of the rotor and the stall cell rotation by using a so-called ‘double phase-locked averaging technique’ developed by the authors.
Structure of the two stall cells are compared with each other: The short length-scale stall cell is characterized by a concentrated vortex spanning from the casing wall ahead of the rotor to the blade suction surface. In the long length-scale stall cell, the separation vortices go upstream irregularly when blade separation develops in the front half of the cell, and reenter the rotor on the hub side in the rear half of it.
The unsteady aerodynamic force and torsional moment acting on the blade tip section have been evaluated from the time-dependent ensemble averages of the casing wall pressure distribution. The force fluctuation due to the short length-scale cells is somewhat smaller than that for the long length-scale cell. The blade suffers two peaks of the force during a period of the short length-scale cells passing through it. The moment fluctuation for the short length-scale cells is considerably larger than that for the long length-scale cell.
Investigation of the Unsteady Rotor Flow Field in a Single HP Turbine Stage
Authors: Kost Friedrich , Hummel Frank , Tiedemann Maik 
Published: August 2014

Within a European project a high-pressure turbine stage was investigated at DLR, Göttingen. The investigations consisted primarily of experiments carried out in the windtunnel for Rotating Cascades (RGG), but some numerical work was also performed.
Detailed measurements were carried out at mid section of a turbine rotor using a Laser-2-Focus device which served as a velocimeter measuring 2D-velocity vectors and turbulence quantities and as a tool to determine the concentration of coolant ejected at the trailing edge of the stator blades. The measurement of coolant concentration downstream of the stator and inside the rotor provided a detailed picture of the stator wake development and its interaction with the moving rotor. Axial measurement locations reached from the stator exit through the rotor to a downstream measurement plane. Measurement results are presented as instantaneous flow values. Unsteady flow vectors and turbulence intensities could be related at 16 time instants representing one rotor blade passsing period to the wake development made visible by the coolant concentration. The measured unsteady flow vectors and unsteady pressures, measured with semi-conductor pressure transducers, are compared with results from a numerical calculation using the Navier-Stokes code “TRACE-U” which allows the computation of the unsteady flow field. The measured steady and unsteady flow quantities served to validate the Navier-Stokes code. A comparison of the wake entropy trajectories outside the blade boundary layers and at the wall gives an impression of the lag between the arrival time of the wake in the freestream near the blade surface and the time the boundary layer quantities at the blade surface itself are affected.
Numerical and Experimental Investigation of Trailing Edge Vortex Shedding Downstream of a Linear Turbine Cascade
Authors: Gehrer A. , Lang H. , Mayrhofer N. , Woisetschläger J. 
Published: August 2014

In this study, the evolution of the unsteady trailing edge vortex street downstream a linear turbine cascade is experimentally and computationally investigated. In a transonic cascade test stand, Laser Doppler velocimeter (LDV) measurements were acquired in several axial planes downstream of the blade trailing edge. In addition, direct detection of density changes near the trailing edge provide information about the frequency of a vortex shedding cycle.
A two-dimensional upwind-biased Navier-Stokes solver has then been used to perform a series of steady and unsteady cascade simulations, allowing an in-depth study into the mechanisms of the trailing edge vortex shedding.
The numerical results are compared with the experimental data to test the quality of the numerical simulations.
Investigation of the Unsteady Rotor Aerodynamics in a Transonic Turbine Stage
Authors: Dénos R. , Arts T. , Paniagua G. , Michelassi V. , Martelli F. 
Published: August 2014

The paper focuses on the unsteady pressure field measured around the rotor mid-span profile of the VKI Brite transonic turbine stage. The understanding of the complex unsteady flow field is supported by a quasi-3D unsteady Navier-Stokes computation using a k-? turbulence model and a modified version of the Abu-Ghannam and Shaw correlation for the onset of transition.
The agreement between computational and experimental results is satisfactory. They both reveal the dominance of the vane-shock in the interaction. For this reason, it is difficult to identify the influence of vane-wake ingestion in the rotor passage from the experimental data. However, the computations allow to draw some useful conclusions in this respect.
The effect of the variation of the rotational speed, the stator-rotor spacing and the stator trailing edge coolant flow ejection is investigated and the unsteady blade force pattern is analyzed.
Unsteady Transport Mechanisms in an Axial Turbine
Authors: Casciaro Claudia , Treiber Martin , Sell Michael 
Published: August 2014

A numerical analysis using a commercial unsteady Navier-Stokes solver has been performed on a pin/blade configuration, in order to assess the efficacy of a commercial code in calculating time-periodic interactions and to gain a better understanding of the unsteady flow physics in axial turbines.
Two cases have been investigated, with the pin positioned at 25% and 50% of true chord ahead of the leading edge. Both configurations have been computed both 2D and 3D.
The 2D case was used to examine the influence of numerical parameters, such as mesh, time and space discretisation. The 3D case allowed insight into the complete flow field including the wake influence on the secondary flow and mixing processes of the blade row.
The basic mechanisms of the wake-blade interaction proved, as expected, to be the same for both pin positions. Yet, as the closest pin wake interaction with the blade field was much stronger, its features have helped to identify the respective roles of wake fluid transport and blade potential field for both cases. The latter effect, noticeably strong with the thick leading edge blade form presented in this study, has been often neglected, and this study helps shed new light on this phenomenon.
The code used had been validated in previous work for pin-free steady flow within the same blade row and the new time dependent case has served to confirm the code range and limitations.
The Control of Non-Axisymmetric Flow in Axial Turbomachinery Using Circumferentially Varying Stator Exit Angles
Authors: Taylor Jonathan , Hynes Tom 
Published: August 2014

Turbomachinery operating in distorted flowfields is often very close to the sources of the distortion, and can influence the flowfield distortions at its inlet and outlet. Several techniques are available to reduce the impact of an upstream-running outlet distortion on the turbomachinery by introducing circumferential variation in the most downstream stator row. However, these techniques assume that the upstream-running distortion is not changed by the modifications to the turbomachinery, and none of them addresses the issue of inlet distortion, either on its own or in combination with outlet distortion.
A methodology to design circumferentially varying stator angles has been developed. This is based on a two-dimensional linearisation of the distorted flow through the turbomachinery, combined with information from three-dimensional flowfield calculations. The resulting new design method has been applied to an installed lift fan operating with considerable inlet and outlet distortion.
The distorted flow through the lift fan is computed by a three-dimensional numerical method incorporating an actuator disc blade row model. The new design method is then used to produce several redesigned builds with circumferentially varying stator exit angles. The three-dimensional flow through the new builds is computed, and compared with flow through the axisymmetric fan.
The calculations show that existing non-axisymmetric design strategies may not be applicable to installations having large flowfield distortions. An alternative approach based on unsteady rotor loading is presented, and relatively small stator exit angle variations are shown to produce significant reductions in this quantity.
A Three-Dimensional Viscous Transonic Inverse Design Method
Authors: Tiow W. T. , Zangeneh M. 
Published: August 2014

The development and application of a three-dimensional inverse methodology is presented for the design of turbomachinery blades. The method is based on the mass-averaged swirl, rV~θ distribution and computes the necessary blade changes directly from the discrepancies between the target and initial distributions. The flow solution and blade modification converge simultaneously giving the final blade geometry and the corresponding steady state flow solution.
The flow analysis is performed using a cell-vertex finite volume time-marching algorithm employing the multistage Runge-Kutta integrator in conjunction with accelerating techniques (local time stepping and grid sequencing). To account for viscous effects, dissipative forces are included in the Euler solver using the log-law and mixing length models. The design method can be used with any existing solver solving the same flow equations without any modifications to the blade surface wall boundary condition.
Validation of the method has been carried out using a transonic annular turbine nozzle and NASA rotor 67. Finally, the method is demonstrated on the re-design of the blades.
Status of the Multi-Annular Swirl Burner at the Power Systems Development Facility
Authors: Brushwood John , Foote John , Morton Frank , Wallace Larry 
Published: August 2014

The Power Systems Development Facility (PSDF) is an engineering scale demonstration of two advanced coal-fired power systems and several high-temperature, high-pressure gas filtration systems. The PSDF was designed at sufficient scale so that advanced power systems and components could be tested in an integrated fashion to provide data for commercial scale-up. The PSDF is funded by the U.S. Department of Energy, Electric Power Research Institute, Southern Company Services, Foster Wheeler, Kellogg Brown & Root, Siemens Westinghouse Power Corporation (SWPC), Combustion Power Company and Peabody Holding Company.
The PSDF is configured into two separate test trains: the Kellogg Brown & Root (KBR) transport reactor train and the Foster Wheeler Advanced Pressurized Fluidized Bed Combustor (APFBC) train. The APFBC train also includes a topping combustor and gas turbine generator to produce electrical power. The APFBC train is designed for long term testing of the filtration systems and the assessment of control and integration issues associated with the APFBC system.
The Siemens Westinghouse Multi-Annular Swirl Burner (MASB) has been developed as the topping combustor for the APFBC application. In this application, the combustion air is vitiated air, a depleted oxygen (10 to 16 vol %), high temperature (1200 to 1400°F) (650 to 760°C) gas stream, which is the exhaust gas from the fluidized bed combustion of solid fuel. The topping combustor fuel is a synthetic low-Btu fuel gas at high temperature (1200 to 1400°F) (650 to 760°C) generated by gasifying coal in the APFBC. The hot MASB combusted gas is expanded through a gas turbine for power generation.
Commissioning of the MASB began in January, 1998. Over 400 hours of operation have been accumulated through November 1999. Several improvements have been designed and installed during commissioning. This paper explains the design basis of the MASB, describes design changes implemented at the PSDF and reviews the operational experience of the MASB at the PSDF.
Disc Design and Air System Comparison Between a Single and a Two Stage High Pressure Turbine Aero Engine
Authors: Ahmad Fathi , Mirzamoghadam Alexander V. 
Published: August 2014

The design of the high pressure turbine (HPT) module of an aero engine and the method used to predict disc life and burst margin are different among the manufactures. In this paper, two different disc design methods are presented and compared, namely, the strain instability and the Chambers methods. The results of the disc study show that the strain instability method introduces low disc weight compared to the Chambers method. Both methods satisfy the burst speed requirement of 125% of the red line limit speed.
The strain instability method was applied to design the disc of a single stage (SS) and of a two stage (TS) HPT configuration. The design philosophy of the SS is to run the HPT with a high rpm and a low SOT, whereas the TS design is based on low rpm and high SOT. The disc preliminary design considered the mechanical boundary conditions only without a temperature gradient. The total boundary conditions (thermal and mechanical) were then applied to the detailed disc design.
A comparison between the two applied air systems of the SS and the TS design configuration was also performed. In comparing the two, the SS presents a design with low cooling air consumption, and it is also found that a cover plate is necessary for the front side of the SS configuration. The results of this study could be useful for the design engineer to know how and what is needed to accomplish a safe and effective design. Complementary thermal and structural tests should be performed to identify the limits and benefits of each approach.
Effect of Swirl on the Performance of a Gas Turbine Reversing Exhaust Duct
Authors: Cunningham M. H. , Birk A. M. , Gauthier J. E. D. , Di Bartolomeo W. 
Published: August 2014

Poor pressure recovery and flow control in gas turbine exhaust ducts can significantly reduce overall engine performance. For aircraft installations, a configuration that presents a challenging design is the single port tractor exhaust that is used where the turbine is facing the direction of travel. This duct consists of an annular to rectangular transition and a turn of approximately 160°. The combination of a diffusing duct with strong curvature produces a flow that has a non-uniform velocity profile throughout the duct, large areas of separation and strong vortices. These flow conditions lead to insufficient diffusion and large pressure losses, making the design of a low loss duct difficult. The problem of design is further complicated by the need for the duct to operate over a range of flow Mach number and swirl angles.
An experimental study has been undertaken to identify the main flow structures that lead to poor performance in tractor exhausts and how the key geometric and flow parameters affect the flow. A half scale model of the exhaust duct has been tested using cold flow over a range of swirl conditions. Flow measurements include static wall pressures, and inlet and outlet velocity profiles.
This paper presents experimental results showing the effects of swirl on a gas turbine single port tractor exhaust duct.
Compressor Stability Enhancement Using Discrete Tip Injection
Authors: Suder Kenneth L. , Hathaway Michael D. , Thorp Scott A. , Strazisar Anthony J. , Bright Michelle B. 
Published: August 2014

Mass injection upstream of the tip of a high-speed axial compressor rotor is a stability enhancement approach known to be effective in suppressing stall in tip-critical rotors. This process is examined in a transonic axial compressor rotor through experiments and time-average Navier-Stokes CFD simulations. Measurements and simulations for discrete injection are presented for a range of injection rates and distributions of injectors around the annulus.
The simulations indicate that tip injection increases stability by unloading the rotor tip and that increasing injection velocity improves the effectiveness of tip injection. For the tested rotor, experimental results demonstrate that at 70% speed the stalling flow coefficient can be reduced by 30% using an injected massflow equivalent to 1% of the annulus flow. At design speed, the stalling flow coefficient was reduced by 6% using an injected massflow equivalent to 2% of the annulus flow. The experiments show that stability enhancement is related to the mass-averaged axial velocity at the tip. For a given injected massflow, the mass averaged axial velocity at the tip is increased by injecting flow over discrete portions of the circumference as opposed to full-annular injection. The implications of these results on the design of recirculating casing treatments and other methods to enhance stability will be discussed.