bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Three-Dimensional Analysis Code of Compressor Performance and Stability for Steady Inlet Distortion
Authors: Guo Jin , Hu Jun , Yin Chao 
Published: August 2015

Inlet distortion has a great impact on the compressor performance and stability. Developing a model which quickly and accurately can assess the performance and stability of a compressor with inlet distortion is one of the key technologies needed to improve the fidelity of a compressor design system. Thus, a new 3-D analysis code called CSAC based on the theory of body force model has been developed and used to predict compressor performance and stability with inlet distortion. The code solves the compressible 3-D Euler equations modified to include source terms which represent the effect of the blade rows. The source terms were calculated by the velocity circulation vectors and entropy production which were extracted from the 3-D Navier-Stokes (N-S) steady-state solutions at the stations between each blade row at many operating points with clean inflow. An analysis was carried out to determine the local flow conditions for parameterizing the magnitude of the velocity circulation vectors and entropy production of individual blade rows.
A NASA stage 35 flow field with clean inlet was simulated with the code. The calculation results agreed well with the N-S solutions and experimental data. The stage 35 performance and stability with inlet steady circumferential total pressure distortion was also simulated using the code. The predicted performance maps of the stage 35 with inlet distortion showed a reduced range and pressure rise. In addition, the results reflected the strong three-dimensional characteristics of the flow field with inlet distortion, and the interaction of the blade rows with the upstream flow field. This paper describes the modeling method of CSAC and presents a detailed examination of the computed results.
An Approach for Estimating the Effect of Transient Sweep Through a Resonance
Authors: Hackenberg Hans-Peter , Hartung Andreas 
Published: August 2015

The difference of a stationary forced response situation of a turbine or compressor blade relative to a transient resonance sweep is well known and documented in the literature. Different approaches have been used to understand the effect on transient amplitude in comparison with forced response. The dependencies on damping levels and resonance passage speed have been noted. Estimates for a critical or/and maximum sweep velocity have been given.
The understanding of transient response during resonance sweep is of practical importance for instance when running a certification stress test for an aircraft engine, where it needs to be decided upfront which acceleration rate (increase in rpm per second) to use to ensure that the maximum airfoil response that could be attained under stationary condition is being measured with sufficient precision. A second reason for understanding of transient response is the verification of correct, if relevant lower, component life usage during transient regimes in operation.
This paper gives a proposal for a simple 1D method based on one degree of freedom (1-dof) system considerations for estimating the transient response dependency on the sweep velocity, damping levels and resonance frequency. The method is verified with 3D analyses of more complex blade-disc structures, which have been validated with air jet excitation rig and aero engine tests. Using the results of the 1-dof analysis, an estimate of the expected stationary resonance response increase can be formulated even in cases where the measured data are based on a significant deviation from the desired sweep velocity, where transient effects would be significant.
Numerical Procedure for the Investigation of Combustion Dynamics in Industrial Gas Turbines: LES, RANS and Thermoacoustics
Authors: Rofi Luca , Campa Giovanni , Anisimov Vyacheslav , Daccá Federico , Bertolotto Edoardo , Gottardo Enrico , Bonzani Federico 
Published: August 2015

The necessity for a combustion system to work with premixed flames and its capability to cope with rapid load variations avoiding the occurrence of thermo-acoustic instabilities, has led to investigate the complex dynamic phenomena that occur during combustion. Thanks to numerical simulations it is possible to examine these complex mechanisms getting useful information to optimize the combustion system. The aim of this work is to describe a numerical procedure developed in Ansaldo Energia for the investigation of combustion dynamics occurring in Ansaldo Energia gas turbines.
In this paper, firstly the experimental apparatus of a full scale atmospheric test rig equipped with Ansaldo Energia burner is described. Secondly, the flame behavior is studied by means of a Large Eddy Simulation (LES). Once the LES has reached a statistically stationary state, a forcing is added to the system to compute the Flame Transfer Function (FTF), in terms of amplitude n and delay time τ, related to initial phases of humming. Thirdly, the forced flame simulations are used as the input of an Helmholtz solver to analyze the acoustic behavior of the system, which is then compared to experimental data. Finally, to evaluate the feasibility of a less computationally intensive approach, a RANS simulation of the same configuration is described and the results are transferred to FEM (Finite Element Method) Helmholtz solver: a comparison between the LES approach and the RANS approach is carried out with reference to the experimental data.
A Simple Low-Fidelity Model for Embedded Blade Row Flutter Prediction
Authors: Zhao Fanzhou , Nipkau Jens , Vahdati Mehdi 
Published: August 2015

Recent rig tests and CFD predictions have shown that acoustic reflections can play an important part on flutter stability of blades in multi-stage compressors. Moreover, as the use of blisks with very low mechanical damping becomes more common in modern aero-engine designs, accurate prediction of blade aerodynamic damping in a multi-row environment becomes vital. Accurate CFD predictions in such environment require unsteady computation of multi-row full annulus models which poses high demands on both computational time and resources and thus cannot be used routinely in early development stages.
The aim of this work is to develop a simple low-fidelity approach for evaluating flutter stability of embedded rotors in multi-stage compressors. The required phase and amplitude relation between the reflected waves and the outgoing waves at leading/trailing edge of the rotor is calculated based on established theories. In the approach taken here, the phase and amplitude of the reflected waves are prescribed as boundary conditions for the blade row of interest, and flutter analysis of the rotor blade is undertaken based on a single passage single-row approach using a validated 3D unsteady RANS solver. Comparison of predicted rotor aerodynamic damping shows good agreement with that obtained using a high-fidelity full annulus multi-row model and test data. An overall reduction of computational cost of roughly 360 times is achieved by the simplified model. The proposed simplified flutter prediction model provides a much faster way of evaluating the susceptibility to acoustic driven flutter, and allows one to study the effects of parameters such as axial gap, frequency and stator vane angles at early development stages on an engine. It should be emphasised that the aim of this paper is to present a low fidelity prediction model for flutter and not noise, and hence the main emphasis is modelling low nodal diameters as a compressor blade is most likely to flutter in such nodal diameters for 1F mode.
Modeling of Rain Drop Erosion in a Multi-MW Wind Turbine
Authors: Corsini Alessandro , Castorrini Alessio , Morei Enrico , Rispoli Franco , Sciulli Fabrizio , Venturini Paolo 
Published: August 2015

The actual strategy in offshore wind energy development is oriented to the progressive increase of the turbine diameter as well as the per unit power. Among many pioneering technological and aerodynamic issues linked to this design trend, the wind velocity at the blade tip region reaches very high values in normal operating conditions (typically between 90 to 110 m/s). In this range of velocity, the rain erosion phenomenon can have a relevant effect on the overall turbine performance in terms of power and energy production (up to 20% loss in case of deeply eroded leading edge). Therefore, as a customary approach erosion related issues are accounted for in the scheduling of the wind turbine maintenance. When offshore, on the other hand, the criticalities inherent to the cost of maintenance and operation monitoring suggest the rain erosion concerns to be tackled at the turbine design stage. In so doing, the use of computational tools to study the erosion phenomenon of wind turbines under severe meteorological conditions could define the base-line approach in the wind turbine blades design and verification.
In this work, the authors present a report on numerical prediction of erosion on a 6 MW HAWT (horizontal axis wind turbine). Two different blade geometries of different aerodynamic loading, have been studied in a view to explore their sensitivity to rain erosion.
The fully 3D simulations are carried out using an Euler-Lagrangian approach. Flow field simulations are carried out with the open-source code OpenFOAM, based on a finite volume approach, using Multiple Reference Frame methodology. Reynolds Averaged Navier-Stokes equations for incompressible steady flow were solved with a k-ε turbulence.
An in-house code (P-Track) is used to compute the rain drops transport and dispersion, adopting the Particle Cloud Tracking approach (PCT), already validated on large industrial turbomachinery.
At the impact on blade, erosion is modelled accounting for the main quantities affecting the phenomenon, which are impact velocity and material properties of the target surface.
Results provide the regions of the two blades more sensitive to erosion, and the effect of the blade geometry on erosion attitude.
Experimental and Numerical Benchmarking of an Improved Meanline Modelling Method for Automotive Turbocharger Centrifugal Compressors
Authors: Harley Peter , Spence Stephen , Filsinger Dietmar , Dietrich Michael , Early Juliana 
Published: August 2015

After the development of a new single-zone meanline modelling technique, benchmarking of the technique and the modelling methods used during its development are presented. The new meanline model had been developed using the results of three automotive turbocharger centrifugal compressors, and single passage CFD models based on their geometry.
The target of the current study was to test the new meanline modelling method on two new centrifugal compressor stages, again from the automotive turbocharger variety. Furthermore the single passage CFD modelling method used in the previous study would be again employed here and also benchmarked.
The benchmarking was twofold; firstly test the overall performance prediction accuracy of the single-zone meanline model. Secondly, test the detailed performance estimation of the CFD model using detailed interstage static pressure tappings.
The final component of this study exposed the weaknesses in the current modelling methods used (explicitly during this study). The non-axisymmetric flow field at the leading and trailing edges for the two compressors was measured and is presented here for the complete compressor map, highlighting the distortion relative to the tongue.
Numerical Investigation on the Vibration of Steam Turbine Inlet Valves and the Feedback to the Dynamic Flow Field
Authors: Domnick Clemens Bernhard , Benra Friedrich-Karl , Brillert Dieter , Dohmen Hans Josef , Musch Christian 
Published: August 2015

The power output of steam turbines is controlled by steam turbine inlet valves. These valves have a large flow capacity and dissipate in throttled operation a huge amount of energy. Due to that, high dynamic forces occur in the valve which can cause undesired valve vibrations.
In this paper, the structural dynamics of a valve are analysed. The dynamic steam forces obtained by previous computational fluid dynamic (CFD) calculations at different operating points are impressed on the structural dynamic finite element model (FEM) of the valve. Due to frictional forces at the piston rings and contact effects at the bushings of the valve plug and the valve stem the structural dynamic FEM is highly nonlinear and has to be solved in the time domain.
Prior to the actual investigation grid and time step studies are carried out. Also the effect of the temperature distribution within the valve stem is discussed and the influence of the valve actuator on the vibrations is analysed.
In the first step, the vibrations generated by the fluid forces are investigated. The effects of the piston rings on the structural dynamics are discussed. It is found, that the piston rings are able to reduce the vibration significantly by frictional damping. In the second step, the effect of the moving valve plug on the dynamic flow in the valve is analysed. The time dependent displacement of the valve is transferred to CFD calculations using deformable meshes. With this one way coupling method the response of the flow to the vibrations is analysed.
Ultra Lean Combustion Characterization in a Pilot-Scale Gas Turbine Burner Using Image Processing Techniques
Authors: De Giorgi Maria Grazia , Sciolti Aldebara , Campilongo Stefano , Ficarella Antonio 
Published: August 2015

The aim of the present investigation is the characterization of the behavior of a lean partially-premixed liquid fuel gas turbine near lean blowout limit.
At this combustion regime the onset of instability will occur with negative impacts on combustion efficiency.
The identification of the instability occurrence permits an efficient flame control adjusting the combustion parameters (as fuel or air mass flow, temperature, pressure, etc.) to stabilize the flame or designing opportunely flame control system.
High-speed images of the flame under stable and near blowout condition were captured in conjunction with simultaneous optical data in order to better understand the phenomenology of the flame blowout process and the onset of instability.
In particular the experimental characterization was performed through a High Speed Digital Camera, an Infrared camera and a Photomultiplier Tube (PMT) in association with the use of optical filter (OH*). The data collected with these instrumentations produce useful features for the development of an efficient tool for the flame control in industrial and aeronautical burners. The images acquired by the different cameras were processed considering the luminosity signal of each pixel and evaluating the frequency behavior, the variations of amplitude of the signals and some other descriptive parameters able to define the regime of the flame. Spectral analysis and Wavelet transform of pixel intensities of flame images were used and entropy and energy contents were evaluated. The spatial maps of the different spectral and statistical parameters were shown at different fuel/air equivalence ratio. The OH* emissions data measured by the PMT were processed and compared with the data obtained from the images processing.
CAD-Based Adjoint Shape Optimisation of a One-Stage Turbine With Geometric Constraints
Authors: Xu Shenren , Radford David , Meyer Marcus , Müller Jens-Dominik 
Published: August 2015

An extension of the CAD-based parametrisation termed ‘NURBS-based parametrisation with complex constraints’, or NsPCC, is developed and applied to the aerodynamic shape optimisition of a one-stage high pressure turbine. NsPCC uses a test-point approach to impose various geometric constraints such as continuity, thickness and trailing edge radius constraint.
To perform the shape optimisation using NsPCC, The surface sensitivity is first computed efficiently using a discrete adjoint solver. The displacements of the control points of the NURBS patches are used as the design variables and linked to the surface sensitivity through consistent application of Automatic Differentiation. A robust mesh deformation based on linear elasticity and further enhanced with sliding mesh capability is used to deform the mesh at each design step. Finally, the optimised rotor shape is exported as a STEP file. The method is demonstrated on a turbine stage where isentropic efficiency is improved by over 0.4% with both the inlet capacity and rotor reaction ratio deviation below the prescribed thresholds. Satisfaction of the G1 continuity, thickness and trailing radius constraints is verified.
Numerical Investigation of the Non-Axisymmetric End Wall Application to the White Cascade
Authors: Li Deying , Chen Huanlong , Song Yanping , Cui Ke 
Published: August 2015

A profiling method, in terms of the trigonometric function and considering about the different axial location of the non-axisymmetric end wall warping, is developed firstly. The axial and the circumferential location of the end wall warping are defined by the cosine function and the sine function respectively.
To investigate the effects of the non-axisymmetric end wall on the flow property and the steam condensation, the profiling method is applied to the aft-loaded White cascade with the revised nucleation model of the two-phase wet steam flow. The results show that it has very little influence on the performance while the non-axisymmetric end wall warping is closing to the leading edge. If the non-axisymmetric end wall warping locates nearby the trailing edge, the aerodynamic loss increases significantly with a sharp flow separation on the corner of the suction side. While the crest is in the middle of the axial chord, the aerodynamic loss nearby the end wall decreases about 2.0%, implying a well improvement in the aerodynamic performance. Besides, the steam condensation nearby the end wall is restrained significantly while the non-axisymmetric end wall warping is in the middle axial chord or closing the trailing edge.
The proper designed non-axisymmetric end wall, which is able to increase the pressure of the zone with the wet steam nucleation, is beneficial to improve the aerodynamic performance and control the steam condensation in the passage of the low pressure steam turbine.
Experimental Investigation on the Vibration Tuning of a Beam With Shape Memory Alloy
Authors: Ma Yanhong , Wang Mingzhang , Yang Xin , Zhang Dayi , Hong Jie 
Published: August 2015

The paper describes the experimental investigation on a smart beam with variable stiffness made of shape memory alloy (SMA). Quasi static experiments were performed on Ti50Ni41Cu9 SMA samples in order to obtain the mechanical characteristics including the Young’s modulus and the loss factor. The test results showed, Ti50Ni41Cu9 SMA exhibited excellent damping performance in Martensite, and the storage modulus varied significantly while SMA transferred from Martensite to Austenitic. The dynamic parameters of SMA were affected by temperature and strain amplitude.
Based on the mechanical characteristics of SMA tested, SMA was applied in the vibration tuning of a beam through experiments. The steady and transient response was suppressed using an effective control strategy according to the variable stiffness control theory. The steady experiments revealed that the first three order natural frequencies could be adjusted significantly by heating/cooling the SMA parts, for example the first order natural frequency varied from 60Hz to 100Hz. The temperature changing rate affected the response amplitude a lot and showed some interesting phenomenon in frequency domain. The transient experiments exhibited that the resonant response was controlled efficiently by changing the temperature of SMA, and the influence laws of the stiffness varying rate on the nonlinear dynamic characteristics was obtained.
Low-Pressure Turbine Cascade Performance Calculations With Incidence Variation and Periodic Unsteady Inflow Conditions
Authors: Marconcini Michele , Pacciani Roberto , Arnone Andrea , Bertini Francesco 
Published: August 2015

The performance of a Low-Pressure Turbine (LPT) cascade were investigated under both steady and periodic unsteady inflow boundary conditions with different Reynolds numbers and a reduced frequency representative of real LPT working conditions. A sensitivity analysis to the variation of the inlet flow angle was performed to assess the performance during off-design operation.
The numerical framework is based on a steady/unsteady Reynolds Averaged Navier-Stokes (RANS/URANS) flow solver which includes some state-of-the-art transition-sensitive turbulence closures. Boundary conditions for the time-accurate computations upstream of the cascade were derived from the experimental characterization of a moving bar system used to generate the wake periodic perturbations.
The computed performance of the cascade, as a function of Reynolds number and incidence angle variation, is discussed in comparison with experimental data. Steady and unsteady boundary layer quantities are also compared with measurements in order to gain more insights into the loss generation process and to better support the numerical results. Such an assessment proves that the proposed procedure is adequate for the analysis of the off-design behavior of cascades operating in low pressure turbine conditions.
An Experimental and Numerical Assessment of Airfoil Polars for Use in Darrieus Wind Turbines: Part 2 — Post-Stall Data Extrapolation Methods
Authors: Bianchini Alessandro , Balduzzi Francesco , Rainbird John M. , Peiro Joaquim , Graham J. Michael R. , Ferrara Giovanni , Ferrari Lorenzo 
Published: August 2015

Accurate post-stall airfoil data extending to a full range of incidences between −180° to +180° is important to the analysis of Darrieus vertical-axis wind turbines (VAWTs) since the blades experience a wide range of angles of attack, particularly at the low tip-speed ratios encountered during startup.
Due to the scarcity of existing data extending much past stall, and the difficulties associated with obtaining post-stall data by experimental or numerical means, wide use is made of simple models of post-stall lift and drag coefficients in wind turbine modeling (through, for example, BEM codes). Most of these models assume post-stall performance to be virtually independent of profile shape.
In this study, wind tunnel tests were carried out on a standard NACA0018 airfoil and a NACA 0018 conformally transformed to mimic the “virtual camber” effect imparted on a blade in a VAWT with a chord-to-radius ratio c/R of 0.25.
Unsteady CFD results were taken for the same airfoils both at stationary angles of attack and at angles of attack resulting from a slow VAWT-like motion in an oncoming flow, the latter to better replicate the transient conditions experienced by VAWT blades.
Excellent agreement was obtained between the wind tunnel tests and the CFD computations for both the symmetrical and cambered airfoils. Results for both airfoils also compare favorably to earlier studies of similar profiles. Finally, the suitability of different models for post-stall airfoil performance extrapolation, including those of Viterna-Corrigan, Montgomerie and Kirke, was analyzed and discussed.