bluuebunny/crossref_metadata_2025_split huggingface dataset:
Non-Axisymmetric Stator Design for Boundary Layer Ingesting Fans
Authors: Gunn E. J. , Hall C. A. 
Published: August 2017

In a Boundary Layer Ingesting (BLI) fan system the inlet flow field is highly non-uniform. In this environment, an axisymmetric stator design suffers from a non-uniform distribution of hub separations, increased wake thicknesses and casing losses. These additional loss sources can be reduced using a non-axisymmetric design that is tuned to the radial and circumferential flow variations at exit from the rotor.
In this paper a non-axisymmetric design approach is described for the stator of a low-speed BLI fan. Firstly sectional design changes are applied at each radial and circumferential location. Next, this approach is combined with the application of non-axisymmetric lean. The designs were tested computationally using full-annulus unsteady CFD of the complete fan stage with a representative inlet distortion. The final design has also been manufactured and tested experimentally.
The results show that a 2D sectional approach can be applied non-axisymmetrically to reduce incidence and diffusion factor at each location. This leads to reduced loss, particularly at the casing and midspan, but it does not eliminate the hub separations that are present within highly distorted regions of the annulus. These are relieved by non-axisymmetric lean where the pressure surface is inclined towards the hub. For the final design, the loss in the stator blades operating with BLI was measured to be 10% lower than for the original stator design operating with undistorted inflow. Overall, the results demonstrate that non-axisymmetric design has the potential to eliminate any additional loss in a BLI fan stator caused by the non-uniform ingested flow-field.
A Discussion on the Advancement of Blade Tip Timing Data Processing
Authors: Kharyton Vsevolod , Dimitriadis Grigorios , Defise Colin 
Published: August 2017

The Blade Tip Timing method (BTT) is a well-known approach permitting individual blade vibration behavior characterization. The technique is becoming increasingly popular among turbomachinery vibration specialists. Its advantages include its non-intrusive nature and its capability of being used for long-term monitoring, both in on-line and offline analysis. However, the main drawback of BTT is frequency aliasing.
Frequency aliasing effects in tip timing can be reduced by means of the application of different methods from digital signal analysis that can exploit the non-uniform nature of the data sampled by BTT. This non-uniformity is due to the fact that an optimization of the circumferential distribution of BTT probes is usually required in order to improve the data quality for targeted modes of blade vibration and/or orders of excitation.
The BTT data analysis methods considered in this study are the non-uniform Fourier transform, the minimum variance spectrum estimator approach, a multi-channel technique using in-between samples interpolation, the Lombe-Scargle periodogram and an iterative variable threshold procedure. These methods will be applied to measured data representing quite a large scope of events occurring during gas-turbine compressor operation, e.g. synchronous engine order resonance crossing, rotating stall, suspected limit-cycle oscillations.
Finally, the frequency estimates obtained from all these methods will be summarized.
Preliminary Design, Ignition, and Fuel Injection for a High Temperature Recuperated Microturbine Combustor
Authors: Tuttle Steven , Hinnant Katherine , Vick Michael 
Published: August 2017

Recuperation and high turbine inlet temperatures could enable miniature (<20 kW) gas turbines to match the fuel efficiency and installed weight of current internal combustion (IC) engines. However, these strategies create unusual challenges for combustor development. As the engine transitions from ignition to steady state, changes in the preheated air temperature, fuel/air mixture, evaporation, and chemical timescales make operability difficult with a fixed-geometry combustor at all operational states. The flame must also be exceptionally clean in all conditions because any soot will foul the recuperator. Furthermore, preheated air is less effective for cooling, potentially creating extreme thermal loads on the liner, especially during transients, and any ignition device that protrudes into the unusually hot primary zone could melt.
This paper describes the preliminary design of a combustor being developed to meet these challenges, and reviews the late progress on subsystem testing and experiments. The combustor is a single-can type with a radial swirler and single atomizer nozzle at one end. An optically accessible burner is being used to explore fundamental aspects of swirler aerodynamics, ignition strategies, liner cooling, and lean blow off behavior. Particle image velocimetry (PIV) is enabling quantitative velocity measurements of swirler jet decay and interaction with the liner wall. Two different methods for projecting an ignition source into the primary zone from outside the liner, a micro-torch and a conventional spark igniter, have been tested.
Evolution of Turbine Cooling
Authors: Bunker Ronald S. 
Published: August 2017

Turbine cooling is a battle between the desire for greater hot section component life and the techno-economic demands of the marketplace. Surprisingly little separates the haves from the have nots. The evolution of turbine cooling is loosely analogous to that of the Darwinian theory of evolution for animals, starting from highly simplistic forms and progressing to increasingly more complex designs having greater capabilities. Yet even with the several generations of design advances, limitations are becoming apparent as complexity sometimes leads to less robust outcomes in operation. Furthermore, the changing environment for operation and servicing of cooled components, both the natural and the imposed environments, are resulting in new failure modes, higher sensitivities, and more variability in life. The present paper treats the evolution of turbine cooling in three broad aspects including the background development, the current state-of-the-art, and the prospects for the future. Unlike the Darwinian theory of evolution however, it is not feasible to implement thousands of small incremental design changes, random or not, to determine the fittest for survival and advancement. Instead, innovation and experience are utilized to direct the evolution.
Over the last approximately 50 years, advances have led to an overall increase in component cooling effectiveness from 0.1 to 0.7. Innovation and invention aside, the performance of the engine has always dictated which technologies advance and which do not. Cooling technologies have been aided by complimentary and substantial advancements in materials and manufacturing. The state-of-the-art now contains dozens of internal component cooling methods with their many variations, yet still relies mainly on only a handful of basic film cooling forms that have been known for 40 years. Even so, large decreases in coolant usage, up to 50%, have been realized over time in the face of increasing turbine firing temperatures. The primary areas of greatest impact for the future of turbine cooling are discussed, these being new engine operating environments, component and systems integration effects, revolutionary turbine cooling, revolutionary manufacturing, and the quantification of unknowns. One key will be the marriage of design and manufacturing to bring about the concurrent use of engineered micro cooling or transpiration, with the ability of additive manufacturing. If successful, this combination could see a further 50% reduction in coolant usage for turbines. The other key element concerns the quantification of unknowns, which directly impacts validation and verification of current state-of-the-art and future turbine cooling. Addressing the entire scope of the challenges will require future turbine cooling to be of robust simplicity and stability, with freeform design, much as observed in the “designs” of nature.
Cracking Analysis of Intermediate Pressure Inlet Diffuser in 1000MW Steam Turbine Units
Authors: Chen Gang , Zhang Junhui , Ye Xingzhu , Ma Chunlei 
Published: August 2017

In 2013, with the operation of 1000MW steam turbine unit in a power plant, the exhaust steam temperature of intermediate pressure (IP) steam turbine exceeded the normal value. After overhaul of the IP steam turbine, a long crack was found through the drain hole of the IP inlet diffuser. The reheat steam leaked out from inside the diffuser to the exhaust cavity. It caused the exhaust temperature to exceed the design value, and reduced the efficiency of the units. Also, if the high temperature steam, which is close to 600°C, came into contact with the outer casing, a significant reduction in life would be obtained. In order to find the root cause of the crack, many efforts have been done within each department of the shanghai turbine plant (STP). Such as material detection, design, manufacture, assembling, etc.
In this paper, a three-dimensional finite element diffuser model was built and the stress state during startup and operation was obtain. It was found that the drain hole at the inside and the groove at the outside of the diffuser are dangerous regions because of the stress concentration. That’s the primary reason for causing the diffuser crack. Then the fracture mechanics software ZenCrack was used to analyze the diffuser crack route. This crack route consistently matched the actual diffuser crack.
A Selective Fast Fourier Filtering Approach Applied to High Frequency Thermoacoustic Instability Analysis
Authors: Grimm Felix , Lourier Jean-Michel , Lammel Oliver , Noll Berthold , Aigner Manfred 
Published: August 2017

A method for selective, frequency-resolved analysis of spatially distributed, time-coherent data is introduced. It relies on filtering of Fourier-processed signals with periodic structures in frequency-domain. Therefrom extracted information can be analyzed in both, frequency- and time-domain using an inverse transformation ansatz.
In the presented paper, the approach is applied to a laboratory scale, twelve nozzle FLOX®-GT-burner for the investigation of high-frequency thermoacoustic pressure oscillations and limit-cycle mechanisms. The burner is operated at elevated pressure for partially premixed combustion of a hydrogen and natural gas mixture with air. At a certain amount of hydrogen addition to fuel injection, the burner exhibits self-sustained high-frequency thermoacoustic oscillation. This unstable operation is simulated with the fractional step approach SICS (Semi Implicit Characteristic Splitting), a pressure based solver extension of the Finite Volume based research code THETA (Turbulent Heat Release Extension for the TAU Code) for the treatment of weakly compressible flows with combustion. A hybrid LES/URANS simulation delivers time-resolved simulation data of the thermoacoustically unstable operation condition, which is analyzed with the presented SFFFA (Selective Fast Fourier Filtering Approach).
Acoustic pressure distribution in the combustion chamber is explicitly resolved and assigned to different characteristic modes by signal decomposition. Furthermore, the SFFFA is used for the analysis of acoustic feedback mechanism by investigating filtered transient heat release, acoustic pressure, velocity and mixture fraction. Coherent structures in flow field and combustion as well as periodic convective processes are resolved and linked to transient acoustic pressure, extensively describing the acoustic feedback of the examined burner configuration.
Efficient Lifetime Prediction of High Pressure Turbine Blades in Real Life Conditions
Authors: van Enkhuizen Marinus Johannus , Dresbach Christian , Reh Stefan , Kuntzagk Stefan 
Published: August 2017

Jet engines of airplanes are designed such that in some components damage occurs and grows in service without being critical up to a certain level. Since maintenance, repair and component exchange are cost-intensive and limit the operating life of the engine, it is necessary to predict the component lifetime using an acceptable computational effort.
To efficiently calculate the lifetime consumption of turbine components with sufficient accuracy under operational conditions, we developed a hybrid approach, which is based on the following three steps: First, the possible operation space is analyzed and reduced to define a manageable Design-of-Experiments (DoE) space. Subsequently, precise aerodynamic and structural mechanic simulations of the component are performed at each DoE support point and the results are stored in a database. Next, the lifetime consumption of the component for the operation profile of interest is calculated based on interpolated stress and temperature fields using suitable lifetime prediction models. The implemented lifetime models are based on accepted lifetime prediction models for creep, fatigue and combined loading, which were extended to incorporate the loading situation on a high pressure turbine (HPT) blade.
Due to efficient data management, the computational time for calculating the lifetime consumption of a whole HPT blade is approximately four seconds for one take-off. Consequently, a full three dimensional lifetime consumption analysis of the lifespan of a HPT blade is possible within a few hours. Using the developed approach, it is now possible to predict the lifetime of a HPT blade for different operators with the necessary precision in an acceptable time. To demonstrate the developed approach, a HPT blade of an exemplarily chosen jet engine with known flight history and documented borescope inspections will be used. Comparing the calculated lifetime of the HPT blade with the documented findings from shop visits reveals that the simulation is in good agreement for the investigated flight mission of the chosen engine.
Experimental Investigation Into Crater Morphology for Droplets Impinging on a Moving Film
Authors: Mitchell Antony J. , Hann David , Simmons Kathy 
Published: August 2017

The behaviour of impinging droplets is a field that has been studied for over 100 years mostly focused on impingements upon solid substrates or static films. Few studies report cases when the moving film might influence the impact outcomes. In many situations where droplet impact is industrially relevant there is film motion and relying on observations and correlations for impacts on static films might not be reliable.
The University of Nottingham’s Gas Turbine and Transmissions Research Centre is conducting a research program investigating impact outcomes and crater morphology for water droplets of around 2–3 mm falling under the influence of gravity and impacting on films created by water flow down an inclined plane. In the investigation reported here dimensionless film heights were in the range 0.77 to 1.8 and the plane was inclined at 10° to the horizontal. This paper details the investigation into the morphology of the crater formed during an impingement event. The properties of the impinging droplet are measured using a high-speed camera to provide a side-view of the impingement. Brightness-Based Laser-Induced Fluorescence (BB-LIF) is used to provide three-dimensional measurements of the crater during the self-similar inertial regime. This is accomplished by doping the fluid with Rhodamine 6G, and exciting the fluorescence with a 527 nm pulsed Nd-Yag laser. A second high-speed camera observes the impingement from below in order to provide information about the behaviour of the film.
The development of cavity depth is compared to published models from work on both deep and thin static films. Further, the development of cavity width with time is compared against existing models from static film research. A modification to these models is proposed that includes the effects of film velocity. The effect of film movement on the cavity footprint is examined; both the equivalent radius and the cavity width are investigated and the differences compared to static film experiments are quantified. Some modifications to an established width model are suggested, and an effect of droplet diameter upon this cavity width is noted. The work shows that static film models are not universally applicable for moving films.
Integrated Approach for Steam Turbine Thermo-Structural Analysis and Lifetime Prediction at Transient Operations
Authors: Moroz Leonid , Doerksen Glenn , Romero Fernando , Kochurov Roman , Frolov Boris 
Published: August 2017

In order to achieve the highest power plant efficiency, original equipment manufacturers (OEMs) continuously increase turbine working parameters (steam temperatures and pressures), improve components design and modify start-up cycles to reduce time while providing more frequent start-up events. All these actions result in much higher levels of thermo-stresses, a lifetime consumption of primary components and an increased demand for accurate thermo-structural and LCF simulations.
In this study, some aspects of methodological improvement are analyzed and proposed in the frame of an integrated approach for steam turbine components thermo-structural analysis, reliability and lifetime prediction. The full scope of the engineering tasks includes aero/thermodynamic flow path and secondary flows analysis to determine thermal boundary conditions, detailed thermal/structural 2D and 3D FE models preparation, components thermal and stress-strain simulation, rotor-casing differential expansion and clearances analysis, and finally, turbine unit lifetime estimation. Special attention is paid to some of the key factors influencing the accuracy of thermal stresses prediction, specifically, the effect of ‘steam condensation’ on thermal BC, the level of detailing for thermal zones definition, thermal contacts and mesh quality in mechanical models. These aspects have been studied and validated against test data, obtained via a 30 MW steam turbine for combined cycle application based on actual start-up data measured from the power plant. The casing temperatures and rotor-stator differential expansion, measured during the commissioning phase of the turbine, were used for methodology validation. Finally, the evaluation of the steam turbine HPIP rotor lifetime by means of a low cycle fatigue approach is performed.
Numerical Investigation of the Heat Transfer and Flow Phenomena in an IP Steam Turbine in Warm-Keeping Operation With Hot Air
Authors: Toebben Dennis , Łuczyński Piotr , Diefenthal Mathias , Wirsum Manfred , Reitschmidt Stefan , Mohr Wolfgang F. D. , Helbig Klaus 
Published: August 2017

Nowadays, steam turbines in conventional power plants deal with an increasing number of startups due to the high share of fluctuating power input of renewable generation. Thus, the development of new methods for flexibility improvements, such as reduction of the start-up time and its costs, have become more and more important. At the same time, fast start-up and flexible steam turbine operation increase the lifetime consumption and reduce the inspection intervals. One possible option to prevent these negative impacts of a flexible operation is to keep the steam turbine warm during a shut down and a startup. In order to do so, General Electric has developed a concept for warm-keeping respectively pre-warming of a high-pressure (HP) / intermediate-pressure (IP) steam turbine with hot air: After a certain cool-down phase, air is passed through the turbine while the turbine is rotated by the turning engine. The flow and the rotational direction can be inverted to optimize the warming operation. In order to fulfill the requirements of high flexibility in combination with reduced costs and thermal stresses during the start-up, a detailed investigation of the dominant heat transfer effects and the corresponding flow structure is necessary: Complex numerical approaches, such as Conjugate Heat Transfer (CHT), can provide this corresponding information and help to understand the physical impact of the flow phenomena.
The aim of the present work is thus to understand the predominant heat transport phenomena in warm-keeping operation and to gain detailed heat transfer coefficients within the flow channel for blade, vane and shrouds. A multitude of steady-state simulations were performed to investigate the different warm-keeping operation points. Data from literature was recomputed in good agreement to qualitatively validate the numerical model in windage operation. Furthermore, the steady-state simulations were compared with transient Computational Fluid Dynamics (CFD) simulations to verify that the flow in warming operation can be simulated with a steady-state case. The transient calculations confirm the steady-state results. A variation of the mass flow rate and the rotational speed was conducted to calculate a characteristic map of heat transfer coefficients. The Conjugate Heat Transfer simulations provide an insight into the flow structure and offer a comparison with the flow phenomena in conventional operation. In addition, the impact of the flow phenomena on the local heat transfer was investigated.
A Review of Inlet-Fan Coupling Methodologies
Authors: Godard Benjamin , De Jaeghere Edouard , Ben Nasr Nabil , Marty Julien , Barrier Raphael , Gourdain Nicolas 
Published: August 2017

With the rise of ultra high bypass ratio turbofan and shorter and slimmer inlet geometries compared to classical architectures, designers face new challenges as nacelle and fan design cannot anymore be addressed independently. This paper reviews CFD methods developed to simulate inlet-fan interactions and suitable for industrial design cycles. In addition to the reference isolated fan and nacelle models, the methodologies evaluated in this study consist of two fan modeling approaches, an actuator disc and body-force source terms.
The configuration is a modern turbofan with a high bypass ratio under cross-wind. Results are compared to experimental data. As to be predicted, the body-force modeling approach enables early inlet reattachment. In addition, it provides a representative flow deviation across the fan zone which enables performance and stability assessments.