bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Flow Distortions as They Occur in S-Duct Inlets on the Performance and Stability of a Jet Engine
Authors: Rademakers Rudolf. P. M. , Bindl Stefan , Niehuis Reinhard 
Published: August 2015

One of the research areas at the Institute of Jet Propulsion focuses on the design and optimization of s-shaped engine inlet configurations. The distortion being evoked within such inlet ducts should be limited to ensure an optimal performance, stability, and durability of the engine’s compression system.
Computational Fluid Dynamics (CFD) play a major role in the design process of bent engine inlet ducts. The flow within such ducts can be computed, distortion patterns can be visualized, and related distortion coefficients are easily calculated. The impact of a distortion on flow phenomena within the compressor system can, however, only be computed with major computational efforts and thus the quality of an s-duct design in development is usually assessed by analyzing the evoked distortion with suitable distortion coefficients without a true knowledge of the duct’s influence on the downstream propulsion system.
The influence of inlet distortion on both the performance and stability of the Larzac 04 jet engine was parameterized during experimental investigations at the engine test bed of the Institute of Jet Propulsion. Both pressure and swirl distortion patterns as they typically occur in s-duct inlet configurations were reproduced with distortion generators. Pressure distortion patterns were generated using seven types of distortion screens. The intensity of the distortion varies with the mesh size of the screen whereas the extension of the distortion is defined by the dimensions of the screen in radial and circumferential direction. A typical counter rotating twin-swirl was generated with a deltawing installed upstream of the compressor system.
First, the development of flow distortion was analyzed for several engine operating points (EOPs). A linear relation between the total pressure loss in the engine inlet and the EOPs was found. Secondly, the flow within the compressor system with an inlet distortion was analyzed and unsteady flow phenomena were detected for severe inlet distortions. Finally, the effect of both pressure and swirl distortion on the performance and stability of the test vehicle was parameterized. A loss in engine performance with increasing inlet distortion is observable. The limiting inlet distortion with respect to engine stability was found and moreover it was shown that pressure distortion has a stronger influence on the stability of the compressor system compared to a counter rotating twin-swirl distortion. The presented parameterization is essential for the s-duct design, which is under development for an experimental set-up with the Larzac 04 jet engine.
Étude on Gas Turbine Combined Cycle Power Plant: Next 20 Years
Authors: Gülen S. Can 
Published: August 2015

In 1992, United States Department of Energy’s Advanced Turbine Systems program established a target of 60% efficiency for utility scale gas turbine power plants to be achieved by the year 2000. Although the program led to numerous technology breakthroughs, it took another decade for an actual combined cycle power plant with an H class gas turbine to reach (and surpass) the target efficiency.
Today, another target benchmark, 65% efficiency, circulates frequently in trade publications and engineering journals with scant support from existing technology, its development path as well as material limits, and almost no regard to theoretical (e.g., underlying physics) and practical (e.g., cost, complexity, reliability and constructability) concerns.
This paper attempts to put such claims to test and establish the room left for gas turbine combined cycle (GTCC) growth in the next two decades. The analysis and conclusions are firmly based on fundamental thermodynamic principles with carefully and precisely laid out assumptions and supported by rigorous calculations. The goal is to arm the practicing engineer with a consistent, coherent and self-standing reference to critically evaluate claims, predictions and other futuristic information pertaining to GTCC technology.
Free Vibration in a Mistuned Steam Turbine Last Stage Bladed Disk
Authors: Drewczynski Marcin , Rzadkowski Romuald , Maurin Artur , Marszalek Piotr 
Published: August 2015

The design of blades in the last stage of a steam turbine is one of the most demanding engineering tasks in the turbomachinery field. Increasing turbine efficiency has led to the designing of higher tip-to-hub ratios. Slender blading conforms to reliability requirements, such as high blade stiffness and a high first mode natural frequency.
Several high vibration amplitude problems were reported regarding a slender last stage blading of a commercial low-pressure steam turbine. During maintenance it was decided that the blades would be geometrically mistuned to prevent self-excitation.
This paper presents a numerical study of LP steam turbine last stage bladed disk mistuning. Two different approaches to mistuning were applied and numerically compared: geometrical and material. The mode shapes and natural frequencies of the steam turbine bladed disk were calculated on the basis of an FEM model. The smallest range of mistuning (0,5Hz) in a bladed disk contaminates nodal diameters up to the fourth series. This should be taken into account when tip-timing method is adapted for steam turbine operation monitoring.
Numerical Analysis of Honeycomb Labyrinth Seals: Cell Geometry and Fin Tip Thickness Impact on the Discharge Coefficient
Authors: Desando Alessio , Rapisarda Andrea , Campagnoli Elena , Taurino Roberto 
Published: August 2015

The design of the newest aircraft propulsion systems is focused on environmental impact reduction. Extensive research is being carried out with the purpose of improving engine efficiency, enhancing crucial features, in order to decrease both fuel consumption and pollutant emissions. A lot of improvements to fulfill these objectives must be made, focusing on the optimization of the main engine parts through the utilization of new technologies. The leakage flow reduction in the turbo machinery rotor-stator interaction is one of the main topics to which numerous efforts are being devoted.
Labyrinth seals, widely employed in the aerospace field thanks to their simple assembly process and maintenance, can be the means to achieve these objectives.
This paper mainly focuses on the optimization of the labyrinth seal stator part, characterized, in modern Low Pressure Turbines (LPT), by a honeycomb cell pattern.
The first phase of this study deals with the implementation and validation of a Computational Fluid Dynamics (CFD) numerical model, by using the experimental data available in the literature. Discharge coefficients obtained by numerical simulations, performed at different clearances and pressure ratios on both smooth and honeycomb non-rotating labyrinth seals, are presented and compared to the literature data.
Then, for both convergent and divergent flow conditions, the effects on the discharge coefficient due to variations in several cell pattern parameters (i.e. cell diameter, depth and wall thickness) and fin tip thickness are shown. For these analyses the values of clearance and pressure ratio are set at a constant value.
Investigation on Water Film Induced Profile Losses in a Compressor Cascade
Authors: Neupert Niklas , Joos Franz 
Published: August 2015

The share of renewable sources in the energy sector is increasing steadily leading to higher requirements towards plant flexibility for conventional plants to compensate for the highly fluctuating power supply. To enhance the flexibility of gas turbine power plants overspray fogging systems can be used. Opposed to this positive effect it was shown that a two-phase flow increases losses and minor turning of the blade row as shown by Ober [1]. The reason for this change in aerodynamic performance, however, is not yet fully understood. As shown by Wurz [2] the velocity profile of the airflow changes in the presence of a water film which is related to an increased roughness due to the waviness of the water film. However, the experimental data base for the effect of a water film on compressor airfoils and its effect on aerodynamics is small and the possibility to capture all relevant effects in numerical codes requires an enormous effort.
Therefore the objective of this study is to show the feasibility of modeling the influence of a water film as a region of increased surface roughness to estimate the aerodynamic effects on the compressor flow more easily. In the first part of the study the focus is directed to the water wall film pattern inspected experimentally at the transonic open loop wind tunnel at Helmut-Schmidt-University in Hamburg for two different airfoils. This study reveals the areas which are covered with a continuous water film. In the second part results of CFD calculations are presented. A reverse approach is used. Instead of simulating the water film in all details the focus is put on modeling the influence of a water film present. The regions previously being detected to be covered by water are defined as rough walls. The roughness height is varied to match experimentally measured losses published by Ober [1]. The results show the magnitude of influence of a wetted surface on the blade profile loss.
Thermoeconomic Analysis of CSP Air-Steam Mixed Cycles
Authors: Barberis Stefano , Traverso Alberto 
Published: August 2015

This paper investigates the integration of Concentrating Solar Power technology in air-steam Mixed Cycles for power production. Starting from a state of the art of CSP plants and the undergoing research in hybridization of Gas Turbine plants, the paper investigates alternative plant configurations particularly regarding the integration of CSP technology with mixed cycles, assessed and compared with a through-life thermo-economic analysis.
Solar heat collected by on the market CSP mirrors at moderate temperatures (300°C–500°C) can be employed to increase conventional steam-injection gas turbine power plants performances. Solar concentrating collectors for current steam solar power plants can be used for such an application can be simpler and less expensive than collectors supposed to be used for hybrid GT CSP Plants which need high temperature systems (collectors and receivers).
The solar hybridization of mixed cycles could be a good opportunity to combine gas turbine technology and CSP systems thus augmenting efficiency and achieving power dispatchability, but avoiding dedicated combustion chambers for hybrid CSP purposes (one of the big technologic problems to combine CSP and Gas Turbine technology). Moreover, the availability of commercial steam injected gas turbines at intermediate power range (10–100MW) allows the realization of such hybrid mixed CSP power plants in their typical size, avoiding the need for very large solar fields and reducing the technological risk as well as the time to market.
Focus is on the design of the plant that was made analyzing different factor like solar share factor, water consumption and reintegration and LCOE. A comparison of this innovative hybrid CSP-STIG plant with traditional STIG, Integrated Solar Combined Cycles (ISCC) and a traditional Combined Cycle was made. The mixed cycles CSP plants are analyzed using the original software WTEMP for the design point analysis, whose library was updated with dedicated modules.
The analysis shows that combining CSP technology with existing mixed cycles lets cost-competitive plant configurations with a relatively short time to market.
Progress in Open Rotor Research: A U.S. Perspective
Authors: Van Zante Dale E. 
Published: August 2015

In response to the 1970s oil crisis, NASA created the Advanced Turboprop Project (ATP) to mature technologies for high-speed propellers to enable large reductions in fuel burn relative to turbofan engines of that era. Both single rotation and contra-rotation concepts were designed and tested in ground based facilities as well as flight. Some novel concepts/configurations were proposed as part of the effort. The high-speed propeller concepts did provide fuel burn savings, albeit with some acoustics and structural challenges to overcome. When fuel prices fell, the business case for radical new engine configurations collapsed and the research emphasis returned to high bypass ducted configurations.
With rising oil prices and increased environmental concerns there is renewed interest in high-speed propeller based engine architectures. Contemporary analysis tools for aerodynamics and aeroacoustics have enabled a new era of blade designs that have both high efficiency and lower noise characteristics. A recent series of tests in the U.S. have characterized the aerodynamic performance and noise from these modern contra-rotating propeller designs. Additionally the installation and noise shielding aspects for conventional airframes and blended wing bodies have been studied. Historical estimates of ‘propfan’ performance have relied on legacy propeller performance and acoustics data. Current system studies make use of the modern propeller data and higher fidelity installation effects data to estimate the performance of a contemporary aircraft system. Contemporary designs have demonstrated high net efficiency, ∼86%, at 0.78 Mach, and low noise, >15 EPNdB cumulative margin to Chapter 4 when analyzed on a NASA derived aircraft/mission. This paper presents the current state of high-speed propeller/open rotor research within the U.S. from an overall viewpoint of the various efforts ongoing. The remaining technical challenges to a production engine include propulsion airframe integration, acoustic sensitivity to aircraft weight and certification issues.
Experimental Test Rig for Combustor-Turbine Interaction Research and Test Results Analysis
Authors: Yin Hong , Liu Shi , Feng Yongxin , Li Mingfei , Ren Jing , Jiang Hongde 
Published: August 2015

Lean premixed combustion technology has been adopted widely for heavy duty gas turbine application. At the combustor inlet section, the basic burner arrangement is multiple-swirl configuration. The multiple-swirl structure creates complicated swirling flow field downstream, which is characterized as non-uniform flow-field and has impacts on the turbine vane. The issue of combustor-turbine interaction effect has become quite prominent.
This paper introduces a new test rig for the combustor-turbine interaction research, which is designed to investigate the influence of multiple-swirl on the turbine vane system. The test rig consists of a combustor simulator and a first stage turbine vane with cooling system. Measurement techniques including the Pressure Sensitive Paint and five-hole probe are applied.
Preliminary test results show that the multiple-swirl combustor flow field has significant impact on the vane cooling system due to the residual swirl intensity at the combustor outlet. The stagnation line at the vane leading edge is obviously altered compared to uniform inflow. Film cooling effectiveness distribution has distinct characteristics under different conditions. The leading edge is most significantly influenced, while the pressure side film cooling system is affected slightly. Under certain condition, the suction side film cooling is influenced locally.
Differential Expansion Sensitivity Studies During Steam Turbine Start-Up
Authors: Topel Monika , Jöcker Markus , Paul Sayantan , Laumert Björn 
Published: August 2015

In order to improve the startup flexibility of steam turbines it becomes relevant to analyze their dynamic thermal behavior. In this work, the relative expansion between rotor and casing was studied during cold start conditions. This is an important property to monitor during start-up given that clearances between rotating and stationary components must be controlled in order to avoid rubbing. The investigation was performed using a turbine thermal simplified model from previous work by the authors. The first step during the investigation was to extend and refine the modeling tool in order to include thermo mechanical properties. Then, the range of applicability of the model was validated by a two-fold comparison with a higher order finite element numerical model and measured data of a cold start from an installed turbine.
Finally, sensitivity studies were conducted with the aim of identifying the modeling assumptions that have the largest influence in capturing the correct thermal behavior of the turbine. It was found that the assumptions for the bearing oil and inter-casing cavity temperatures have a large influence ranging between ± 25% from the measured values. In addition, the sensitivity studies also involved increasing the initial temperature of the casing in order to reduce the peak of differential expansion. Improvements of up to 30% were accounted to this measure. The studies performed serve as a base towards further understanding the differential expansion during start and establishing future clearance control strategies during turbine transient operation.
Flowfield and Temperature Profiles Measurements on a Combustor Simulator Dedicated to Hot Streaks Generation
Authors: Bacci Tommaso , Caciolli Gianluca , Facchini Bruno , Tarchi Lorenzo , Koupper Charlie , Champion Jean-Louis 
Published: August 2015

In order to deepen the knowledge of the interaction between modern lean burn combustors and high pressure turbines, a real scale annular three sector combustor simulator has been assembled at University of Florence, with the goal of investigating and characterizing the generated aerothermal field and the hot streaks transport between combustor exit and the high pressure vanes location. To generate hot streaks and simulate lean burn combustors behavior, the rig is equipped with axial swirlers, fed by main air flow that is heated up to 531 K, and liners with effusion cooling holes that are fed by air at ambient temperature. The three sector configuration is used to reproduce the periodicity on the central sector and to allow to perform measurements inside the chamber, through the lateral walls.
Ducts of different length have been mounted on the swirlers, preserving the hot mainflow from the interaction with coolant. Such configurations, together with the one without ducts, have been tested, using different measurement techniques, in order to highlight the differences in the resulting flow fields.
First of all, isothermal PIV measurements have been performed on the combustion chamber symmetry plane, to highlight the mixing phenomena between the mainflow and cooling flows. Then a detailed investigation of the mean aerothermal field at combustor exit has been carried out, for nominal operating conditions, by means of a five hole pressure probe provided with a thermocouple, installed on an automatic traverse system. With the aim of analyzing the hot streaks transport and the flow field modification towards the vanes location, such measurements have been performed on two different planes: one located in correspondence of the combustor exit and the further one placed downstream, in the virtual location of the vanes leading edges.
Therefore, an experimental database, describing the evolution of the flow field in a combustor simulator with typical traits of modern lean burn chambers, for different injector geometries, has been set up.
Numerical Investigation of Two-Phase Wet Steam Flow With Spontaneous Condensation Based on Euler S2 Calculation Method
Authors: Li Deying , Chen Huanlong , Song Yanping , Cui Ke , Ooyama Hiroharu 
Published: August 2015

The Euler equation suitable for the S2 stream surface calculation is derived in the arbitrary orthogonal coordinate system firstly. The numerical method for the two-phase wet steam flow with the spontaneous condensation is then developed on basis of the Euler S2 calculation code, the Eulerian/Eulerian multiphase model and the classic nucleation theory.
To adapt the complex geometry of the turbine blades, the Euler equations for the S2 stream surface calculation method are derived in the body-fitted coordinate system. The mathematical model for the third order TVD scheme with the non-conservative variables is also developed for the gas phase governing equation. The 2nd order NND and the VanLeer scheme are applied to the variable reconstruction and the numerical flux calculation respectively in the liquid equations solving process. The pressure and the droplet radii distribution fit well with the experimental data for both the high pressure nozzle and the low pressure nozzle. The S2 calculation method is also employed to predict the performance of a 3-stage low pressure steam turbine with spontaneous steam condensation, and the reasonable results are obtained.
The numerical method developed in the present work is able to predict the real wet steam flow with the spontaneous condensation and its impact on the flow field and the aerodynamic parameters distribution reasonably, supplying a fast and accurate technic and method to the steam turbine design.
An Implicit Harmonic Balance Method in Graphics Processing Units for Vibrating Blades
Authors: Crespo Javier , Corral Roque , Pueblas Jesus 
Published: August 2015

An implicit harmonic balance method for modeling the unsteady non-linear periodic flow about vibrating airfoils in turbomachinery is presented. As departing point, an implicit edge-based three-dimensional Reynolds Averaged Navier-Stokes equations solver for unstructured grids that runs both on central processing units (CPUs) and graphics processing units (GPUs) is used. The harmonic balance method performs a spectral discretization of the time derivatives and marches in pseudo-time a new system of equations where the unknowns are the variables at different time samples.
The application of the method to vibrating airfoils is discussed. It is shown that a time spectral scheme may achieve the same temporal accuracy at a much lower computational cost than a Backward Finite Difference method at the expense of using more memory.
The performance of the implicit solver has been assessed with several application examples. A speed-up factor of 10 is obtained between the spectral and finite difference version of the code whereas and an additional speed-up factor of 10 is obtained when the code is ported to GPUs, totalizing a speed factor of 100. The performance of the solver in GPUs has been assessed using the 10th standard aeroelastic configuration and a transonic compressor.
Numerical Modeling of an Aero-Engine Bearing Chamber Using the Meshless Smoothed Particle Hydrodynamics Method
Authors: Wieth Lars , Lieber Christian , Kurz Wolfram , Braun Samuel , Koch Rainer , Bauer Hans-Jörg 
Published: August 2015

The prediction of the two-phase flow in an aero-engine bearing chamber using the meshless Lagrangian Smoothed Particle Hydrodynamics (SPH) method is presented in this paper. The prediction of the prevailing flow types, like shear-driven wallfilms, droplet-wall- and droplet-film-interactions require an accurate numerical method, which is robust and efficient. Therefore, a code based on the SPH method was developed and validated to numerically predict such technical relevant multi-phase flows in gas turbines.
The simulations to be presented in this paper are focused on an aero-engine bearing chamber configuration, which was experimentally investigated previously. For time saving reasons, the bearing chamber is modeled as two-dimensional problem. This requires special boundary conditions for the oil- and sealing-air flow inlet and outlet, which must physically reflect those of the experiments. In the experiments different operating regimes at different boundary conditions could be identified.
The major objective of the simulations is to investigate if those different flow regimes can be captured by the numerical method. The simulations do reproduce the different flow regimes highly accurate and demonstrate the ability of this new approach.