bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two Phase CFD Modelling of a Spiral Bevel Gear Using Particle Injections and a Wall Film Model
Authors: Turner A. , Morvan H. P. , Simmons K. 
Published: November 2013

The capability to model an aeroengine internal gearbox in its entirety using CFD is currently hampered by the complexity of the two-phase, highly rotating system and the computational resource required. The University of Nottingham’s Technology Centre in Gas Turbine Transmission Systems has developed a representation of a shrouded gear based around a cone geometry with momentum sources driving the flow that works well for single phase flow. The next phase of the study is to investigate the capability and limitations of this momentum source model for two phase flow and a significant step towards this is reported here.
In this paper a geometrically representative shrouded gear model is generated and oil droplets are released at key inlet locations. The impact locations of these droplets are mapped to generate data for comparison with the momentum source model. A thin film model is applied such that film build up can be investigated. Droplets entering the shroud at inlet impact towards the lower part of the shroud whereas those introduced at a location representing an into-mesh jet impact more evenly along the shroud. The film model is computationally expensive: computations show film building up towards the top of the shroud but attaining steady state has not been possible.
Droplets are released and tracked within the momentum source CFD model. Droplets do not impact the shroud at comparable locations to the representative geometry cases showing that the momentum source representation cannot be used to examine in detail oil behaviour under the shroud. Overall bulk flows cannot yet be compared and further necessary work is identified.
Blade Tip Shape Optimization for Enhanced Turbine Aerothermal Performance
Authors: De Maesschalck C. , Lavagnoli S. , Paniagua G. 
Published: November 2013

In high-speed unshrouded turbines tip leakage flows generate large aerodynamic losses and intense unsteady thermal loads over the rotor blade tip and casing. The stage loading and rotational speeds are steadily increased to achieve higher turbine efficiency, and hence the overtip leakage flow may exceed the transonic regime. However, conventional blade tip geometries are not designed to cope with supersonic tip flow velocities. A great potential lays in the modification and optimization of the blade tip shape as a means to control the tip leakage flow aerodynamics, limit the entropy production in the overtip gap, manage the heat load distribution over the blade tip and improve the turbine efficiency at high stage loading coefficients.
The present paper develops an optimization strategy to produce a set of blade tip profiles with enhanced aerothermal performance for a number of tip gap flow conditions. The tip clearance flow was numerically simulated through two-dimensional compressible Reynolds-Averaged Navier-Stokes (RANS) calculations that reproduce an idealized overtip flow along streamlines. A multi-objective optimization tool, based on differential evolution combined with surrogate models (artificial neural networks), was used to obtain optimized 2D tip profiles with reduced aerodynamic losses and minimum heat transfer variations and mean levels over the blade tip and casing. Optimized tip shapes were obtained for relevant tip gap flow conditions in terms of blade thickness to tip gap height ratios (between 5 and 25), and blade pressure loads (from subsonic to supersonic tip leakage flow regimes) imposing fixed inlet conditions. We demonstrated that tip geometries which perform superior in subsonic conditions are not optimal for supersonic tip gap flows. Prime tip profiles exist depending on the tip flow conditions. The numerical study yielded a deeper insight on the physics of tip leakage flows of unshrouded rotors with arbitrary tip shapes, providing the necessary knowledge to guide the design and optimization strategy of a full blade tip surface in a real 3D turbine environment.
Inverse Design of 3D Multi-Stage Transonic Fans at Dual Operating Points
Authors: Page James H. , Hield Paul , Tucker Paul G. 
Published: November 2013

Semi-inverse design is the automatic re-cambering of an aerofoil, during a computational fluid dynamics (CFD) calculation, in order to achieve a target lift distribution while maintaining thickness, hence “semi-inverse”. In this design method, the streamwise distribution of curvature is replaced by a stream-wise distribution of lift. The authors have developed an inverse design code based on the method of Hield (2008) which can rapidly design three-dimensional fan blades in a multi-stage environment. The algorithm uses an inner loop to design to radially varying target lift distributions, an outer loop to achieve radial distributions of stage pressure ratio and exit flow angle, and a choked nozzle to set design mass flow. The code is easily wrapped around any CFD solver.
In this paper, we describe a novel algorithm for designing simultaneously for specified performance at full speed and peak efficiency at part speed, without trade-offs between the targets at each of the two operating points. We also introduce a novel adaptive target lift distribution which automatically develops discontinuous changes of calculated magnitude, based on the passage shock, eliminating erroneous lift demands in the shock vicinity and maintaining a smooth aerofoil.
Consideration of Complex Support Structure Dynamics in Rotordynamic Assessments
Authors: Krüger Thomas D. , Liberatore Sauro , Knopf Eric , Clark Alastair 
Published: November 2013

In rotordynamic analyses, support structures are commonly represented by lumped mass systems (single-degree-of-freedom, SDOF). This representation is easy to implement using standard rotordynamic tools. However, in reality the dynamic behaviour of the support structure (e.g. pedestals, casings, foundations) are in general much more complex. Only a multi-degree-of-freedom (MDOF) representation provides modelling close to reality.
For many applications the dynamic behaviour of the support structure significantly influences the rotordynamic characteristics of the shaft train and therefore needs to be included in the assessment. Due to this impact, a good quality of the dynamic model used for the support structure is imperative. Regarding the rotor itself, the modelling is well understood and the prediction quality is excellent, not least due to the jointless welded rotor design.
Numerous theoretical approaches exist for considering the complex dynamic behaviour of the support structure, all coming along with both drawbacks and opportunities. By discussing the characteristics of established approaches for modelling the support structure, the paper particularly presents an advanced theoretical approach based on a state-space representation using modal parameters.
A case study of a real shaft train is shown, including a comparison of achieved results using the SDOF and the presented MDOF approach. By validating with experimental results, the excellent prediction quality of the MDOF approach is confirmed. The implementation of this approach enabled to further improve the reliability and the efficiency, which means high accuracy combined with low computation time, in performing rotordynamic assessments.
Aero-Mechanical Optimization Design of a Transonic Fan Blade
Authors: Deng Xiangyang , Guo Fushui , Liu Yesheng , Han Pinlian 
Published: November 2013

This paper presents the optimization design of a high bypass ratio civil fan blade with the consideration of aerodynamics, static and dynamic mechanics. The baseline fan blade was designed with a conventional approach without using automatic optimization techniques on both the aero side and the mechanical side. Therefore, the objective of this paper is to achieve a higher aero-mechanical performance under the multiple aerodynamic and mechanical constraints.
Before the optimization, the static stress and modal analysis are performed on the baseline fan blade with/without the introduction of the arc dovetail root and shank. The results are compared to investigate the necessity of including the arc root and shank in the aero-mechanical optimization.
With respect to the optimization process, the numerical design of experiment (DOE) by means of high fidelity CFD/FEA computations is firstly performed to construct the database for the initialization of Kriging surrogate mode. After that, the surrogate model is integrated with the optimization design process, and the non-dominated sorting genetic algorithm (NSGAII) is implemented to obtain the Pareto front, based on which the optimal design is selected. Utilizing this optimization process, both the aero-only and aero-mechanical optimizations are carried out.
The results show that the attenuation of the 3D shock wave strength between the middle and shroud span improves the overall aero performance of the fan blade in both the aero-only optimal design and the aero-mechanical optimal design. Compared with the aero-only optimal design, the aero-mechanical optimal design shows the efficiency penalty within all the operation range simulated, however, the mechanical performance is significantly enhanced by the mitigation of the static stress level on the entire arc dovetail root and shank as well as the increase of the resonance margin.
One-Piece Flow Blade Tuning Process
Authors: Han Pinlian , Chen Tiefeng , Liu Yesheng 
Published: November 2013

Blade tuning is one of the key tasks of the modern aircraft engine design. Generally, a couple of vibration modes of a blade need to be tuned by changing the distribution of its mass and/or stiffness to avoid the resonance at some specified rotating speed. The widely used traditional method for blade tuning is a loop-based process. It requires a number of design iterations between the aero engineer and the structure engineer. It usually takes a few weeks or up to a few months, depending on the experiences of the engineers, to reach an acceptable new design. The uncertainties caused by the non-convergence associated with the loop-based iteration process have led to serious issues for both project management and quality control. To avoid the problem, this paper presents a robust one-piece flow process based on the principle of the set-based concurrent engineering and applying the concept of Lean & DFSS.
Following the concept of Lean & DFSS process, the one-piece flow blade tuning starts with defining key parameters and objectives. These parameters consist of a set of design variables relevant to both structure and aero disciplines. The variation range of each parameter is predefined by the manufacture feasibility and the past design experiences.
Based on the principles of DOE, only a definite number of FEA models are developed and analyzed. From these analysis results, important parameters are selected and a family of response functions of those concerned objectives is formulated. The achievable ranges of the objectives are well determined accordingly.
Guided by these functions, the structure and aero engineers are then able to evaluate instantly any new design from the various combinations of the above-mentioned design parameters. A robust design can be obtained from the given sensitivity of the variance of those design parameters.
This methodology can be applied to blade and vane tuning for fans, compressors and turbines alike. In this paper an example of the application of this process is presented for a hollow fan blade tuning, which is accomplished within a week as planned. The methodology can be standardized and used in many other related engineering design processes as well.
Impact of Swirl on the Sensitivity of the Radial Mode Analysis in Turbomachinery
Authors: Laguna Juan D. , Bartelt Michael , Seume Joerg R. 
Published: November 2013

Sound measurements in turbomachinery are a prerequisite for the study and consequent understanding of sound propagation mechanisms. For analyzing these measurements, the Radial Mode Analysis (RMA) is applied. This method decomposes the transmitted sound field in dominant acoustical modes at specific frequencies. Before an experimental campaign is carried out, measurement parameters are selected such that the uncertainty in the results from the application of the RMA is minimized.
In order to minimize uncertainties, a sensitivity analysis of the parameters which influence the overall error of the RMA is performed. This analysis focuses mainly on the output of a measurable quantity, namely on the propagating mode amplitudes. Using a numerical simulation, modal structures are generated based upon real turbine operating data with swirling flow and a characteristic operating temperature. The swirling flow is generated by adding an axial vortex to a constant flow-velocity profile. The results show that the sound field varies under consideration of swirling mean flow compared to uniform flow conditions. In the present case, higher-order modes dominate the propagating sound structure. The parameters studied for assessing the sensitivity are the signal-to-noise ratio of the measurement sensors, the number of triggered revolutions, the azimuthal spacing of the sensors, and a triggering delay. The sensitivity analysis gives a detailed insight into the measurement parameters influencing the output of the RMA, e.g. that small triggering delays cause appreciable measurement errors. This knowledge is used to define the requirements for high fidelity measurements.
Effects of Tip Clearance on the Stall Inception Process in an Axial Compressor Rotor
Authors: Yamada Kazutoyo , Kikuta Hiroaki , Furukawa Masato , Gunjishima Satoshi , Hara Yasunori 
Published: November 2013

The paper presents experimental and numerical studies on the effects of tip clearance on the stall inception process in a low-speed axial compressor rotor with a large tip clearance. It has been revealed that in the small tip clearance case, shortly after the spike disturbance which results from the leading-edge separation near the rotor tip appears, the tornado-like vortex is generated by the separation, and soon the compressor falls into stall. In the large tip clearance case, the experiment showed that the performance characteristic differs from that in the small tip clearance case at near-stall conditions. This implies that the stall inception process differs with the tip clearance size. The flow phenomenon in the stall inception leading to such difference has been investigated in this study.
Pressure and velocity fields which were ensemble-averaged and phase-locked by the periodic multi-sampling technique were measured on the casing wall and downstream of the rotor, respectively. In addition, to capture the unsteady flow phenomena inside the rotor, “Instantaneous Casing Pressure Field Measurement” was carried out: instantaneous casing pressure fields in one rotor passage region were measured by 30 high response pressure transducers mounted on the casing wall. In order to investigate further details of near-stall flow field for the large tip clearance, DES (Detached Eddy Simulation) has been conducted using a computational mesh with 120 million points. The results are compared with those from previous studies for the small tip clearance.
As expected, the measurement results show notable differences in the near-stall flow field between the two tip clearance cases. The results from the casing pressure measurement show that high pressure fluctuation appears on the pressure side near the rotor leading-edge in the large tip clearance case. In the result of the velocity field measurement downstream of the rotor, high turbulence intensity is found near the casing in the large tip clearance case. The numerical results reveal that the vortex breakdown occurs in the tip leakage vortex and induces the oscillation of the tip leakage vortex with its unsteady nature. The flow phenomena confirmed in the experimental results are clearly explained by considering the breakdown of the tip leakage vortex. The vortex breakdown gives rise to not only large blockage but also the rotating disturbance through the interaction of the fluctuating tip leakage vortex with the pressure surface of the adjacent blade, and governs the stall inception process.
Statistical Impact of Manufacturing Tolerances on Axial Gaps Between Vane Segments and the Rotor of Axial Flow Turbo-Compressors
Authors: Weihard Stefan , Hupfer Andreas , Kau Hans-Peter 
Published: November 2013

Geometrical deviations arising from the manufacturing process significantly influence the axial gaps between rotating and nonrotating parts. To optimize axial gaps and thus reduce the overall length and weight of the compressor, it is essential to take the statistical nature of these deviations into account.
The focus of this paper is to identify complex three-dimensional effects caused by geometrical uncertainties. The results can be then used to define an appropriate level of detail for the simulation model in order to accurately predict the probability distribution of axial gaps.
In the simulation model the parts are assembled according to defined mechanical constraints and the paper presents mathematical models regarding this. A simplified 2D model of a sectional view and a detailed 3D model are implemented and investigated. A 2D tolerance analysis shows that a statistical gap tolerance can be defined based on geometrical parameters. It must be assumed that a certain percentage of all gap values will fall below the lower specification limit for this tolerance interval. A detailed 3D analysis, however, results in a change in the probability distribution of the gap values compared to the simplified 2D analysis. In addition to the standard deviation, the mean value of the gap is reduced significantly. Therefore, a simplified 2D approach may yield invalid results. What this effect is will depend on the configuration. One influencing factor is the number of vane segments in the compressor stage. A sensitivity analysis is presented which identifies and quantifies the impact of such important design parameters.
GPU Speed-Up for the Implicit Navier-Stokes Solver
Authors: Huang Junfeng , Lin Zhirong , Ma Can , Yuan Xin 
Published: November 2013

In this study, an in-house higher-order, high resolution implicit CFD solver for Favre-averaged Navier-Stokes equation with two-equation turbulence model, which including fourth-order MUSCL TVD scheme for Right-Hand-Side and LU-SGS-GE scheme for Left-Hand-Side, is implemented to run on a single Graphic Process Unit (GPU) using the Compute Unified Device Architecture (CUDA).
The partly parallel model for implicit scheme is introduced and we have got a good acceleration using this partly parallel model. The case of VKI 59 is used to test the accelerations. Results obtained on a single GPU (NVDIA GeForce 560Ti, Memory: DDR5 1G 2004 Mhz) are compared with the results obtained on the single CPU (Intel i5 2.8–3.0 GHz, Memory: DDR3 8G 800 Mhz). The speed-up is about 25. The fourth-order MUSCL TVD used in the code is extended to the simulation of multi-species, and also speed-up by using GPU. The case of a single stage turbine with hot-spot inlet boundary is used to test the code with multi-species scheme using GPU. Furthermore, in the study, the shared memory is used to speed-up the code, which is introduced in details in the paper. In the end, the influence factors of the acceleration are discussed.
Radial Inflow Turbine: Synchronous Vibration Failure
Authors: Duong Loc Q. , Thayalakhandan Nagamany , Hu Charlene X. 
Published: November 2013

Radial inflow turbine is frequently used in small gas turbine application where ruggedness and simplicity are prime requisites. For compactness, the radial turbine is mounted back to back with a radial compressor resulting in an overhung rotor in both compressor and turbine wheel. In such configuration the structural integrity of the radial turbine is crucial since due to its large inertia its failure could result in an uncontained egress of the engine. This paper presents one class of radial inflow turbine wheel failure due to high cycle fatigue of synchronous nature caused by two different excitation sources, namely mechanics and aerodynamics. While the first source of excitation is associated with the dynamics of the rotor, the second one is related to the dynamic of fluid flow and the thermal characteristics of the combustor, expressed in terms of hot streak. These sources of excitation can act individually or in combination. Two distinct types of failures were illustrated — blade mode — and disc-blade coupling mode. The failure phenomenon is characterized by fatigue crack originated at location corresponding to maximum dynamic stress for each type of failures, followed by the released of one portion of the blade.
Analytical methods including finite element method, rotor dynamics analysis, and computational fluid dynamics are used to illustrate the root cause of such failure and also to its underlying solutions. Laser vibrometry and optical method were used to obtain the blade dynamic characteristics and to validate the solutions.
Experimental Investigation of the Noise Generation and Propagation for Different Turning Mid Turbine Frame Setups in a Two-Stage Two-Spool Test Turbine
Authors: Faustmann C. , Lengani D. , Spataro R. , Marn A. , Göttlich E. , Heitmeir F. 
Published: November 2013

The paper deals with the investigation of the noise generation in the two-stage two-spool test turbine located at the Institute for Thermal Turbomachinery and Machine Dynamics (ITTM) at Graz University of Technology. The rig went into operation within the EU-project DREAM, where the target was to investigate the aerodynamics of interturbine flow ducts. The facility is a continuously operating cold-flow open-circuit plant which is driven by pressurized air. The flow path contains a transonic turbine stage (HP) followed by a low pressure turbine stage consisting of a turning mid turbine frame and a counter-rotating LP-rotor.
Downstream of the low pressure turbine a measurement section is instrumented with acoustic sensors. The acquisition system consists of a fully circumferentially traversable microphone array located at the outer casing, while at the hub endwall a stationary flush mounted microphone is placed as a reference.
Additionally a new embedded concept for the turning mid turbine frame was tested. Here, two zero-lift splitters were located into the vane passage.
In order to evaluate the noise emission of the turbine the facility was instrumented with a new acoustic measurement setup which is presented in the paper. Therefore the emitted sound pressure level and the microphones signal spectra are compared for both configurations. The acoustic field was characterized by azimuthal modes by means of a microphone array traversed over 360 degrees.
In the multisplitter configuration, the propagating modes due to the HP turbine are found suppressed by 5 dB, while the increase in amplitude of the modes related to the LP turbine is negligible. The overall effect is a reduction of the acoustic emission for the turning mid turbine frame with embedded design.