bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Approach of Whole Engine Structural System Design
Authors: Andoh Masaharu , Honda Tatsuhito , Takamatsu Kikuo 
Published: September 2014

Fuel-efficient jet engines are developed by many companies. In the conventional design approach of a jet engine, many parameters are investigated independently. Consequently, a developed jet engine by this approach meets conventional design criteria but there is still room for improvement of engine performance. In this research, the new design approach of a jet engine that integrates these design objectives is developed and performance of a jet engine is evaluated. The goal is to develop the design approach of a fuel-efficient and robust jet engine.
In current design, a jet engine is developed with a focus on not only performance improvement but also robustness. Therefore, Taguchi method is adopted in order to assess robustness. By this method, a jet engine is optimized based on the analysis that minimizes deterioration and variation of SFC. As a result, more efficient engine design is realized with the new design approach that directly deals with SFC.
Accelerated 3D Aerodynamic Optimization of Gas Turbine Blades
Authors: Amtsfeld Philipp , Lockan Michael , Bestle Dieter , Meyer Marcus 
Published: September 2014

State-of-the-art aerodynamic blade design processes mainly consist of two phases: optimal design of 2D blade sections and then stacking them optimally along a three-dimensional stacking line. Such a quasi-3D approach, however, misses the potential of finding optimal blade designs especially in the presence of strong 3D flow effects. Therefore, in this paper a blade optimization process is demonstrated which uses an integral 3D blade model and 3D CFD analysis to account for three-dimensional flow features. Special emphasis is put on shortening design iterations and reducing design costs in order to obtain a rapid automatic optimization process for fully 3D aerodynamic turbine blade design which can be applied in an early design phase already.
The three-dimensional parametric blade model is determined by up to 80 design variables. At first, the most important design parameters are chosen based on a non-linear sensitivity analysis. The objective of the subsequent optimization process is to maximize isentropic efficiency while fulfilling a minimal set of constraints. The CFD model contains both important geometric features like tip gaps and fillets, and cooling and leakage flows to sufficiently represent real flow conditions.
Two acceleration strategies are used to cut down the turn-around time from weeks to days. Firstly, the aerodynamic multi-stage design evaluation is significantly accelerated with a GPU-based RANS solver running on a multi-GPU workstation. Secondly, a response surface method is used to reduce the number of expensive function evaluations during the optimization process. The feasibility is demonstrated by an application to a blade which is a part of a research rig similar to the high pressure turbine of a small civil jet engine. The proposed approach enables an automatic aerodynamic design of this 3D blade on a single workstation within few days.
Considerations About the Necessary Mesh Density of Bearings in Detailed Finite Element Models
Authors: Kober Markus , Kühhorn Arnold , Stelldinger Enrico , Keskin Akin 
Published: September 2014

In order to predict properly the behavior of very complex mechanical models, much focus needs to be done on the level of model details as well as the techniques used to predict component movements based on mechanical and thermal loads. In particular bearings and joints play a significant role in big model assemblies such as aero-engines where most of the structures are modeled by solid elements rather than using traditional shell or beam elements. This approach is very complex and expensive in terms of computational effort however can lead to increased simulation accuracy when done properly.
This publication will answer questions related to the modeling techniques required for detailed bearings (not only rotor bearings) and joints of an aero-engine application where these components are not idealized or simplified, i.e. the ball in a ball joint is meshed by solid elements. The investigation will discuss the question about the number of elements needed to mesh a ball joint in such a way that a correct rotation is possible. If the mesh is too coarse, a rotation would be impossible due to the faceting of the rotating parts. It will be shown that a proper rotation depends on a correct relation between the radius of the inner ball, the gap size of the bearing and the number of nodes in the circumferential direction. For this relation an analytical formula has been derived and successfully tested at some examples. Furthermore, some finite element codes offer the possibility of smoothed contact surfaces. These options improve the situation but they might cause issues too. For this reason these smoothed contact options are also considered under the aspects mentioned above.
Suppression of Secondary Flows in an Axial Flow Turbine Rotor With a Novel Blade Design Concept
Authors: Yamada Kazutoyo , Furukawa Masato , Shibata Takanori , Nakakido Satoshi , Oka Nobuhito 
Published: September 2014

This paper presents a novel blade design concept about control of the secondary flow in axial turbines to improve the internal efficiency. A rotor blade for the high and intermediate pressure stage of a steam turbine was designed by one-dimensional inverse method incorporated with throughflow calculation.
In the throughflow calculation, the axisymmetric Navier-Stokes equations are solved, assuming that the meridional flow is axisymmetric and viscous. To take into account the blade loading, a blade force is introduced as a body force to the governing equations. The blade force contains the inviscid blade effect only, namely, the pressure difference across a blade. The blade force acts in the direction perpendicular to a three-dimensional blade camber surface, which is constructed from camber lines stacked in blade height direction, so that the flow convects along the surface. The camber line is calculated by one-dimensional inverse method, based on a given blade loading distribution and the meridional velocity distribution from the throughflow calculation. The present throughflow calculation method was validated for a direct problem, using blade geometry of existing turbine rotor. The blade force with the camber surface in the present method was able to express the secondary flow inside the turbine by modifying the camber surface appropriately. As a result, the calculation result showed good agreement with the experimental result.
The turbine rotor blade was redesigned with the present method, modifying the chord-wise blade loading distribution so as to suppress the development of the secondary flow. The way of modifying the chord-wise blade loading distribution is based on a new idea, which can be actualized by the present design method. It was confirmed that the secondary flow was successfully suppressed as intended in the designed rotor.
Numerical Investigation of Impeller Tip Tailoring and its Impact on Aerodynamic Design of a Centrifugal Compressor’s Impeller
Authors: Mahajan Ashvin , Baert Lieven , Leborgne Michaël , Lonfils Timothée , Parwatha I. Gede , Timoshadchenko Denis 
Published: September 2014

The current research focuses on the aerodynamic design of a centrifugal compressor and the effect of tip tailoring on the aerodynamic impeller efficiency. To this extent a high-fidelity multi-point design optimization process has been developed and exploited on a high pressure ratio transonic impeller. By manipulating the shape of the impeller blades and endwalls and by including advanced geometrical features such as winglets on the impeller blades, the behavior of the impeller flow has been investigated. Here, the results of three-dimensional RANS simulations with the Spalart-Allmaras turbulence model on a structured multi-block mesh is used for the evaluation of the flow characteristics.
In the context of radial machines, the results of the aerodynamic design optimization show an important improvement of the impeller isentropic efficiency compared to the reference impeller, with a significant contribution from the presence of the impeller tip winglets. Furthermore, the integration of the impeller winglet has encouraged this study to provide a detailed analysis on the impeller flow structures in order to have a better understanding of the effects of tip tailoring on impeller performance.
Influential Parameters on Structural Damping Values of Turbine Blades
Authors: Hentschel Olaf P. , Panning-von Scheidt L. , Wallaschek J. , Denk M. , Masserey P.-A. 
Published: September 2014

In turbomachinery blading the avoidance of High Cycle Fatigue (HCF) failures is of great importance. The prediction and reduction of vibration amplitudes is of primary objective in context of HCF risk reduction. For this reason the quantification of the mechanical damping is of essential relevance.
During the last decades the research has been focused on the usage of nonlinear calculation tools to predict vibration amplitudes of blades. These calculations require the specification of contact parameters as well as of material damping values. Especially for weakly damped systems like turbine blades, it is necessary to specify adequate structural damping values which determine the accuracy of the calculated transfer function. However, many researchers use uncertain structural damping values to calculate transfer functions.
In this paper, an experimental setup for specimen specific damping determination in a vacuum chamber is presented. Three different clamping mechanisms, as well as the mechanism for specimen excitation, are introduced. A suspended-like specimen clamping, where the specimens are clamped in their nodes of vibration, is described first. To analyze potential influence of the clamping procedure, a comparison is given to specimens clamped on one side (cantilever beams), where the magnitude of the clamping force is chosen in a way that the friction loss is minimized. To allow an application of static stresses the specimens are clamped on both sides in the third approach. The excitation of the analyzed specimens is performed with the help of a voice-coil actuator. Damping values are determined by analyzing the decay curve, which is measured with a laser doppler vibrometer. Further experimental results show the influence of ambient pressure, frequency, amplitude, geometry, mode shape, static stress and clamping mechanism on the specimen specific damping value.
Two-Dimensional Modeling of Shaft Precessional Motions Induced by Blade/Casing Unilateral Contact in Aircraft Engines
Authors: Salvat Nicolas , Batailly Alain , Legrand Mathias 
Published: September 2014

In the present work, the focus is made on the occurrence of precessional motions of the shaft — whirling motions — in bladed-disk assemblies, initiated by direct blade/casing contacts in one stage of an aircraft engine. These contact events are favored by increasingly reduced blade-tip clearances and are expected to occur during standard operating conditions. However, it has been shown that potentially harmful interactions may arise and threaten the engine structural integrity.
A 2D in-plane model of an aircraft engine fan stage is built with a set of curved beams for the casing and an assembly straight beams for the bladed-disk. The flexibility of the shaft is reflected by two linear springs attached to the center node of the disk. Contact is initiated through a prescribed casing distortion and the two structures are then left free to interact. Equations of motion are solved via explicit time-marching and contact forces are computed with Lagrange multipliers method allowing to fully satisfy non-penetration conditions. Friction is accounted for through a Coulomb law and permanent sliding is assumed.
Three types of regimes are identified, namely: (1) damped, (2) sustained, (3) divergent, and both forward and backward shaft precessional motions are witnessed. It is shown that the vibratory response of the bladed-disk mainly lies on the first nodal diameter of the first family of modes regardless of the rotational velocity or the type of regime detected. The risk of failure arising from these contact events is highlighted, in particular in the presence of forward whirl, and the need for accurate predictive tools in early design phases of the engine is emphasized.
Effect of Variable Properties and Radiation on Convective Heat Transfer Measurements at Engine Conditions
Authors: Greiner Nathan J. , Polanka Marc D. , Rutledge James L. , Shewhart Andrew T. 
Published: September 2014

Experiments measuring film cooling performance are often performed near room temperature over small ranges of driving temperature. For such experiments, fluid properties are nearly constant within the boundary layer and radiative heat transfer is negligible. Consequently, the heat flux to the wall is a linear function of driving temperature. Therefore, the convective heat transfer coefficient and adiabatic wall temperature can be extracted from heat flux measurements at two or more driving temperatures.
For large driving temperatures, like those seen in gas turbine engines, significant property variations exist within the boundary layer. In addition, radiative heat transfer becomes sufficiently large such that it can no longer be neglected. As a result, heat flux becomes a non-linear function of driving temperature. Thus, for these high temperature cases, ambient temperature methods utilizing a linear heat flux assumption cannot be employed to characterize the convective heat transfer.
The present study experimentally examines the non-linearity of heat flux for large driving temperatures flowing over a flat plate. The results are first used to validate the temperature ratio method presented in a previous study to account for variable properties within a boundary layer. This validation highlighted the need to account for the radiative component of the overall heat transfer. A method is subsequently proposed to account for the effects of both variable properties and radiation simultaneously. Finally, the method is validated with the experimental data.
While this methodology was developed in a flat plate rig, it is applicable to any relevant configuration in a hot environment. The method is general and independent of the overall radiative component magnitude and direction. Overall, the technique provides a means of quantifying the impact of both variable properties and the radiative flux on the conductive heat transfer to or from a surface in a single experiment.
Minimization of Heat Load due to Secondary Reactions in Fuel Rich Environments
Authors: Shewhart Andrew T. , Polanka Marc D. , Robertson Jacob J. , Greiner Nathan J. , Rutledge James L. 
Published: September 2014

The demand for increased thrust, higher engine efficiency, and reduced fuel consumption has increased the turbine inlet temperature and pressure in modern gas turbine engines. The outcome of these higher temperatures and pressures is the potential for unconsumed radical species to enter the turbine. Because modern cooling schemes for turbine blades involve injecting cool, oxygen rich air adjacent to the surface, the potential for reaction with radicals in the mainstream flow and augmented heat transfer to the blade arises. This result is contrary to the purpose of film cooling. In this environment there is a competing desire to consume any free radicals prior to the flow entering the rotor stage while still maintaining surface temperatures below the metal melting temperature.
This study evaluated various configurations of multiple cylindrical rows of cooling holes in terms of both heat release and effective downstream cooling. Results were evaluated based on a new Wall Absorption parameter which combined the additional heat available from these secondary reactions with the length of the resulting flame to determine which schemes protected the wall more efficiently. Two particular schemes showed promise. The two row upstream configuration reduced the overall augmentation of heat by creating a short, concentrated reaction area. Conversely, the roll forward configuration minimized the local heat flux enhancement by spreading the reaction area over the surface being cooled.
Study on the Regression Method of Compressor Map Based on Partial Least Squares Regression Modeling
Authors: Ying Yulong , Sun Bo , Peng Shuhong , Wu Keliang , He Lei , Xu Qiang 
Published: September 2014

One of the most troublesome problems in the development of a component-based engine model is the compressor modeling because of the strong dependence of its performance on rotational speed and the treatment of compressor characteristic curves plays a significant role in modeling and simulation of gas turbine for the analysis of its off-design performance and thus it is crucial to describe compressor map exactly.
Usually part of rotational speed characteristic curves of compressor including on-design operating point are known during actual modeling and simulation, and reasonable interpolation and extrapolation have to be done in order to make good use of flow characteristics and efficiency characteristics under more constant rotational speed lines during off-design performance simulation.
Due to that the accuracy of traditional approaches for component characteristic treatment is not satisfactory, and the performance of interpolation and extrapolation of artificial neural network is poor, a linear multiple regression method, i.e., partial least-squares regression method was proposed in this paper.
Partial least-squares regression modeling method was used to reproduce the compressor maps. Different polynomial functions of various powers were used to obtain respectively expressions of compressor maps. Fitting accuracy and performance of interpolation and extrapolation of this method were analyzed, and the simulating experimental results show that partial least-squares regression method can ensure good fitting accuracy and good performance of interpolation and extrapolation for compressor thermodynamic modeling with both maximum RMS errors less than 0.5%.
It can be expected that the application of partial least-squares regression modeling has a certain reference value to improve the solution accuracy for thermodynamic model of industrial gas turbine.
Analysis of Effect of Advanced Technique Configurations on Overall Performance of High Bypass Turbofan Engine
Authors: Jun Liu Jian 
Published: September 2014

An analytical study was undertaken using the performance model of a two spool direct drive high BPR 300kN thrust turbofan engine, to investigate the effects of advanced configurations on overall engine performance. These include variable bypass nozzle, variable cooling air flow and more electric technique.
For variable bypass nozzle, analysis on performance of outer fan at different conditions indicates that different operating points cannot meet optimal performance at the same time if the bypass nozzle area kept a constant. By changing bypass nozzle throat area at different states, outer fan operating point moves to the location where airflow and efficiency are more appropriate, and have enough margin away from surge line. As a result, the range of variable area of bypass nozzle throat is determined which ensures engine having a low SFC and adequate stability.
For variable cooling airflow, configuration of turbine cooling air flow extraction and methodology for obtaining change of cooling airflow are investigated. Then, base on temperature analysis of turbine vane and blade and resistance of cooling airflow, reduction of cooling airflow is determined. Finally, using performance model which considering effect of cooling air flow on work and efficiency of turbine, variable cooling airflow effect on overall performance is analyzed.
For more electric technique, the main characteristic is to use power off-take instead of overboard air extraction. Power off-take and air extraction effect on overall performance of high bypass turbofan engine is compared. Investigation demonstrates that power offtake will have less SFC.
An Efficient Component Map Generation Method for Prediction of Gas Turbine Performance
Authors: Tsoutsanis Elias , Meskin Nader , Benammar Mohieddine , Khorasani Khashayar 
Published: September 2014

Improving efficiency, reliability and availability of gas turbines have become more than ever one of the main areas of interest in gas turbine research. This is mainly due to the stringent environmental regulations that have to be met in such a mature technology sector; and consequently new research challenges have been identified. One of these involves the establishment of high fidelity, accurate, and computationally efficient engine performance simulation, diagnosis and prognosis technology.
Performance prediction of gas turbines is strongly dependent on detailed understanding of the engine component behaviour. Compressors are of special interest because they can generate all sorts of operability problems like surge, stall and flutter; and their operating line is determined by the turbine characteristic. Compressor performance maps, which are obtained in costly rig tests and remain manufacturers proprietary information, impose a stringent limitation that has been commonly resolved by scaling default generic maps in order to match the targeted off-design or engine degraded measurements. This approach is efficient in small range of operating conditions but becomes less accurate for a wider range of operations.
In this paper, a novel compressor map generation method, with the primary objective of improving the accuracy and fidelity of the engine model performance prediction is developed and presented. A new compressor map fitting and modelling method is introduced to simultaneously determine the best elliptical curves to a set of compressor map data. The coefficients that determine the shape of compressor maps’ curves have been analyzed and tuned through a multi-objective optimization algorithm in order to meet the targeted set of measurements. The proposed component map generation method is developed in the object oriented Matlab/Simulink environment and is integrated in a dynamic gas turbine engine model. The accuracy of this method is evaluated for off-design steady state and transient engine conditions. The proposed compressor map generation method has the capability to refine current gas turbine performance prediction approaches and to improve model-based diagnostic techniques.