bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Key Flow Parameter to the Profile Loss of Low-Pressure Turbine Blades
Authors: Kodama Hidekazu , Funazaki Ken-ichi 
Published: September 2021

Abstract
For an optimum performance design of low-pressure turbine (LPT) blades, it is crucial to understand the generation mechanism of profile loss properly. As the profile loss is usually taken to be the loss generated inside the blade boundary layer due to viscous effects, most of the efforts for the performance optimization have concentrated on the reduction in the boundary layer loss using the flow parameters that represent the loss generation in the boundary layers. Kodama and Funazaki [1] investigated the generation mechanism of profile loss from a view point of blade drag forces, friction drag force and pressure drag force, and suggested that the loss due to pressure drag is dominant in the profile loss of a typical LPT blade. The loss due to pressure drag is not a boundary layer loss that is generated in the boundary layers, but a mixing loss that is generated downstream of the trailing edge. It is necessary to clarify a key flow parameter to the loss due to pressure drag for an effective performance optimization.
This paper aims at investigating the flow parameter that is a measure of the profile loss. In the investigation, the profile loss is broken down into the loss components which are expressed by the boundary layer integral parameters at the trailing edge. Then the loss components are categorized into the loss due to friction drag or the loss due to pressure drag. The loss level of each component is evaluated by using the results of steady Reynolds Averaged Navier-Stokes (RANS) simulations to assess the contribution to the total profile loss. The evaluations are conducted for two kinds of blade profiles at three different Reynolds numbers. It is found that the largest contributor to the loss due to pressure drag, consequently to the total profile loss, is the loss associated with a mixing of accelerated free stream flow by the flow blockage at the trailing edge plane. The loss level is simply determined by the flow blockage. This suggests that the flow blockage at the trailing edge plane is the most important flow parameter for an optimum performance design of LPT blades.
Delay Identification in Thermoacoustics
Authors: Gant F. , Ghirardo G. , Cuquel A. , Bothien M. R. 
Published: September 2021

Abstract
The stability of thermoacoustic systems is often regulated by the time delay between acoustic perturbations and corresponding heat release fluctuations. An accurate estimate of this value is of great importance in applications, since even small modifications can introduce significant changes in the system behavior Different studies show that the nonlinear delayed dynamics typical of these systems can be well captured with low-order models. In the present work, a method is introduced to estimate the most likely value of the time delay of a single thermoacoustic mode from a measured acoustic pressure signal. The mode of interest is modeled by an oscillator equation, with a nonlinear delayed forcing term modeling the deterministic flame contribution and an additive white Gaussian noise to embed the stochastic combustion noise. Additionally, other thermoacoustic relevant parameters are estimated. The model accounts for a flame gain, for a flame saturation coefficient, for a linear acoustic damping and for the background combustion noise intensity. The pressure data time series is statistically analyzed and the set of unknown parameters is identified. Validation is performed with respect to synthetically generated time series and low order model simulations, for which the underlying delay is known a priori. A discussion follows about the accuracy of the method, in particular a comparison with existing methods is drawn.
Flow and Heat Transfer Mechanisms in a Rotating Compressor Cavity Under Centrifugal Buoyancy-Driven Convection
Authors: Gao Feng , Chew John W. 
Published: September 2021

Abstract
This paper presents a systematic study of flow and heat transfer mechanisms in a compressor disc cavity with an axial throughflow under centrifugal buoyancy-driven convection, comparing with previously published experimental data. Wall-modelled large-eddy simulations are conducted for six operating conditions, covering a range of rotational Reynolds number (3.2 × 105 – 2.2 × 106), buoyancy parameter (0.11 – 0.26) and Rossby number (0.4 – 0.8). Numerical accuracy and computational efficiency of the simulations are considered. Wall heat transfer predictions are compared with measured data with a good level of agreement. A constant rothalpy core occurs at high Eckert number, appearing to reduce the driving buoyancy force. The flow in the cavity is turbulent with unsteady laminar Ekman layers observed on both discs except in the bore flow affected region on the downstream disc cob. The shroud heat transfer Nusselt number-Rayleigh number scaling agrees with that of natural convection under gravity for high Rayleigh numbers. Disc heat transfer is dominated by conduction across unsteady Ekman layers, except on the downstream disc cob. The disc bore heat transfer is close to a pipe flow forced convection correlation. The unsteady flow structure is investigated showing strong unsteadiness in the cavity that extends into the axial throughflow.
Experimental and Numerical Investigation on the Effect of Pressure On Micromix Hydrogen Combustion
Authors: Kroniger Daniel , Horikawa Atsushi , Funke Harald H.-W. , Pfaeffle Franziska , Kishimoto Tsuyoshi , Okada Koichi 
Published: September 2021

Abstract
The micromix (MMX) combustion concept is a DLN gas turbine combustion technology designed for high hydrogen content fuels. Multiple non-premixed miniaturized flames based on jet in cross-flow (JICF) are inherently safe against flashback and ensure a stable operation in various operative conditions.
The objective of this paper is to investigate the influence of pressure on the micromix flame with focus on the flame initiation point and the NOx emissions. A numerical model based on a steady RANS approach and the Complex Chemistry model with relevant reactions of the GRI 3.0 mechanism is used to predict the reactive flow and NOx emissions at various pressure conditions. Regarding the turbulence-chemical interaction, the Laminar Flame Concept (LFC) and the Eddy Dissipation Concept (EDC) are compared. The numerical results are validated against experimental results that have been acquired at a high pressure test facility for industrial can-type gas turbine combustors with regard to flame initiation and NOx emissions.
The numerical approach is adequate to predict the flame initiation point and NOx emission trends. Interestingly, the flame shifts its initiation point during the pressure increase in upstream direction, whereby the flame attachment shifts from anchoring behind a downstream located bluff body towards anchoring directly at the hydrogen jet. The LFC predicts this change and the NOx emissions more accurately than the EDC. The resulting NOx correlation regarding the pressure is similar to a non-premixed type combustion configuration.
Design and Testing of an Internally-Cooled Radial Turbine With High Tip Speed
Authors: Musgrove Grant O. , Smith January , Smith Ellen , White Steve 
Published: September 2021

Abstract
Radial impellers are not internally-cooled because of the manufacturing challenge. The conventional manufacturing method for internally-cooled components is an investment cast process using a ceramic core to create internal passages. This approach has been developed for axial gas turbines for the past few decades and is a low-risk manufacturing approach for single blade castings. However, conventional manufacturing methods are difficult to apply to a radial impeller in a cost-effective manner. For example, the entire impeller (blades and the hub) are typically manufactured from a single piece of material. Therefore, if one blade is poorly cast, the entire impeller must be thrown away.
To overcome the complexity and reduce production risk, additive manufacturing can be used to build internally-cooled radial impellers. Additive manufacturing is a growing area and gaining operational experience is required to confidently build complex parts, such as a radial impeller with small, internal passages. In this paper, additive manufacturing is used to avoid the challenges of conventionally manufacturing. Multiple iterations of the internal cooling design are examined to illustrate lessons learned. Flow and heat transfer tests are used to verify the impeller cooling design. Material properties are discussed to verify that the impeller can withstand high rotational stresses.
Accurate Interpolation of the Dependency of Modal Properties on the Rotation Speed for the Transient Response Analysis of Bladed Disks
Authors: Tong Jing , Zang Chaoping , Petrov E. P. 
Published: September 2021

Abstract
During fast gas-turbine engine acceleration and deceleration the transient vibration effects in bladed disk vibration become significant and the transient response has to be calculated.
In this paper an effective method is developed for efficient calculations of the transient vibration response for mistuned bladed disks under varying rotation speeds. The method uses the large-scale finite element modelling of the bladed disks allowing the accurate description of the dynamic properties of the mistuned bladed disks.
The effects of the varying rotation speed on the natural frequencies and mode shapes of a mistuned bladed disk and its effects on the amplitude and the spectral composition of the loading are considered. The dependency of the modal characteristics on the rotation speed are based on the evaluation of these characteristics at reference points followed by the interpolation to obtain values at any rotation speed from the operating range.
A new method has been developed for the interpolation of mode shapes while preserving the orthogonality and mass-normalization of the mode shapes. The method of mode shape interpolation is elaborated for tuned and mistuned bladed disks. The accuracy and efficiency of the method is demonstrated on test examples and on analysis of transient forced response of realistic bladed discs.
A Design of Experiments Based Investigation of the Influence of Hot Cross-Flow Gas on a FLOX®-Based Single-Nozzle Liquid Burner
Authors: Izadi Saeed , Zanger Jan , Kislat Oliver , Enderle Benedict , Grimm Felix , Kutne Peter , Aigner Manfred , Kraus Cedric 
Published: September 2021

Abstract
Increased global demand for cleaner energy production and growing concern about using fossil fuels have urged many researchers to focus their work on developing more efficient and flexible combustion processes. In this regard, a FLOX®-based liquid fuel single-nozzle burner is investigated for use in a Capstone C30 micro gas turbine (MGT). The main advantages of FLOX®-based combustor systems are their decreased NOx emissions and increased fuel flexibility. An atmospheric test rig is set up to investigate the behavior of the FLOX®-based liquid fuel burner under the influence of the hot gas. The circulating gas in the C30 annular combustion chamber is emulated by hot cross-flow gas generated by a 20-nozzle FLOX®-based natural gas burner operated on a separate horizontal test rig. The variation and combination of the process parameters of both burners are done systematically according to Design of Experiments (DOE) as a statistical design methodology. DOE methodology is adopted rather than the conventional one-factor-at-a-time (OFAT) strategy, as DOE considers any possible interaction between the factors and reduces the number of experiments. Employing statistical design of experiments allows determining which input variables are responsible for the observed changes in the response, developing a model relating the response to the important input variables, and using this model for improving the combustor system. The results are subsequently run through the Analysis of Variance (ANOVA) in order to allow for an objective conclusion about the effect of the factors on the selected responses, which include mass flow rate (·fuel) and global air equivalence ratio (λ) of both of the liquid and natural gas burners. The hot gas cross-flow interaction with the liquid fuel burner is assessed through analyzing exhaust gas emissions and averaged flame OH*-chemiluminescence images. The models developed by the DOE method can be used to estimate the emissions and the flame geometrical properties of any other operating points that are not explicitly tested.
GT26 2006 Turbine Stage 1 Blade Reconditioning Development and Qualification at Ansaldo Repair Centre
Authors: Mela Elisa , Fignino Federico , Gabrielli Alessio , Guarnone Paola , Porro Emanuele , Kellerer Rudolf , Staempfli Matthias 
Published: September 2021

Abstract
The evolution of industrial gas turbines towards increased efficiency and performance requires even higher operating temperatures for the engines. In order to remain competitive in the market, OEM companies continuously need to develop maintenance programs and repair technologies able to extend the life of these components as much as possible.
The repair technology improvement is fundamental to reduce scrap rates and maintenance costs to be competitive on the market.
The Ansaldo Repair Centre answers to this market demand by providing advanced and competitive repair techniques and an increasing broad repair portfolio to its customers.
This paper describes the steps and approach to determine the repair process of GT26 LPT Blade 1 in order to allow the component to run another service interval. The base material status and the indication found after service was used as the foundation for a development of a dedicated repair sequence from stripping, to suitable heat treatments, to enhanced repair technique to recoating of the blade.
Particular attention was paid to the most damaged area, for which a particular welding procedure including an optimized filler material has been applied for the rebuilding of the tip and platform zones as well as for the restoration of the unique tip closing features.
Jet Impingement Heat Transfer Enhancement With Different Crossflow Diverter Shapes
Authors: He Juan , Deng Qinghua , Feng Zhenping 
Published: September 2021

Abstract
Impingement cooling is an effective cooling structure in gas turbine blades, but the downstream heat transfer will be reduced seriously by crossflow. It has been proven that equipping a crossflow diverter in impingement channel can make jet free from crossflow and enhance the downstream heat transfer. In this paper, in order to obtain a kind of crossflow diverter with advantageous heat transfer performance, the flow and heat transfer characteristics of four crossflow diverters (Semi-Circular (SC), Semi-Rectangular (SR), Semi-Diamond (SD) and Semi-Four-pointed Star (SFS)) are compared in detail. To this end, a Baseline impingement cooling configuration is considered, in which the pitches on the streamwise and spanwise directions of impingement jets are all 6D and the distance from jet to target surface is 2D. Through detailed numerical verification, SST k-ω turbulence model is finally selected, and all simulations are performed under Reynolds number ranging from 3,500 to 14,000. It is found that the crossflow diverter can change the local jet Reynolds number distribution and effectively reduce the local mass velocity ratio of crossflow to jet. Results reveal that the crossflow diverter increases the heat transfer and inevitably increases the friction loss, but all of them can improve the comprehensive heat transfer performance over the simulated flow range. When the Reynolds number is 14,000, the best heat transfer performance can be achieved, and the comprehensive heat transfer performance parameters of SC, SR, SD and SFS cases can increase by up to 11.0%, 14.3%, 12.2% and 14.7% respectively. After determining SFS-shaped crossflow diverter with the best comprehensive heat transfer performance, the influence of its streamwise position on heat transfer and friction loss is also studied. The SFS-shaped diverter is placed at 2D, 2.5D, 3D, 3.5D and 4D from the center of adjacent upstream jet, respectively. Results show that the heat transfer and friction loss change a little when the distance increases from 2D to 3D, but the heat transfer decreases sharply and friction loss increases seriously when the distance increases from 3D to 4D.
Considerations for the Evaluation of Fouling Resistant Coatings for Centrifugal Compressors
Authors: Laney Scot 
Published: September 2021

Abstract
For over forty years, coatings have been used as a means to prevent the build-up of foulants on the flow passages of centrifugal compressors. In general, this has been a “One Size Fits All” solution, with most OEMs and applicators offering nearly identical coating systems, despite the fact that there are distinct differences in the types of foulant that occurs in different services. To develop new coatings, there are two options, test “on the job” or test in a laboratory setting. This paper looks at various test methods to evaluate coatings by isolating the important aspects that a good fouling resistant coating should possess, namely fouling, erosion, and corrosion resistance. Each of these will be investigated separately in a battery of easy to perform tests. To the extent possible, the tests for each aspect attempt to replicate the complex conditions that occur in a centrifugal compressor that impact that specific aspect. The fouling and corrosion tests were performed with considerations for two different types of service. To illustrate the ability of the test to evaluate various coatings, the results from three different coatings will be discussed. These test methods will also be compared to other test methods used in literature.
Preliminary Evaluation of the 24 Ft. Diameter Fan Performance In the MinWaterCSP Large Cooling Systems Test Facility
Authors: van der Spuy S. J. , Els D. N. J. , Tieghi L. , Delibra G. , Corsini A. , Louw F. G. , Zapke A. , Meyer C. J. 
Published: September 2021

Abstract
The MinWaterCSP project was defined with the aim of reducing the cooling system water consumption and auxiliary power consumption of concentrating solar power (CSP) plants. A full-scale, 24 ft (7.315 m) diameter model of the M-fan was subsequently installed in the Min WaterCSP cooling system test facility, located at Stellenbosch University. The test facility was equipped with an in-line torque arm and speed transducer to measure the power transferred to the fan rotor, as well as a set of rotating vane anemometers upstream of the fan rotor to measure the air volume flow rate passing through the fan. The measured results were compared to those obtained on the 1.542 m diameter ISO 5801 test facility using the fan scaling laws. The comparison showed that the fan power values correlated within +/− 7% to those of the small-scale fan, but at a 1° higher blade setting angle for the full-scale fan. To correlate the expected fan static pressure rise, a CFD analysis of the 24 ft (7.315 m) diameter fan installation was performed. The predicted fan static pressure rise values from the CFD analysis were compared to those measured on the 1.542 m ISO test facility, for the same fan. The simulation made use of an actuator disc model to represent the effect of the fan. The results showed that the predicted results for fan static pressure rise of the installed 24 ft (7.315 m) diameter fan correlated closely (smaller than 1% difference) to those of the 1.542 m diameter fan at its design flowrate but, once again, at approximately 1° higher blade setting angle.
Experimental and Numerical Study for Improved Understanding of Mixed-Convection Type of Flows in Turbine Casing Cavities During Shut-Down Regimes
Authors: Murat Oguzhan , Rosic Budimir , Tanimoto Koichi , Egami Ryo 
Published: September 2021

Abstract
Due to increase in the power generation from renewable sources, steam and gas turbines will be required to adapt for more flexible operations with frequent start-ups and shut-downs to provide load levelling capacity. During shut-down regimes, mixed convection takes place with natural convection dominance depending on the operating conditions in turbine cavities. Buoyant flows inside the turbine that are responsible for non-uniform cooling leading to thermal stresses and compromise clearances directly limits the operational flexibility. Computational fluid dynamics (CFD) tools are required to predict the flow field during these regimes since direct measurements are extremely difficult to conduct due to the harsh operating conditions. Natural convection with the presence of cross-flow -mixed convection has not been extensively studied to provide detailed measurements. Since the literature lacks of research on such flows with real engine representative operating conditions for CFD validation, the confidence in numerical predictions is rather inadequate.
This paper presents a novel experimental facility that has been designed and commissioned to perform very accurate unsteady temperature and flow field measurements in a simplified turbine casing geometry. The facility is capable of reproducing a wide range of Richardson, Grashof and Reynolds numbers which are representative of engine realistic operating conditions. In addition, high fidelity, wall resolved LES with dynamic Smagorinsky subgrid scale model has been performed. The flow field as well as heat transfer characteristics have been accurately captured with LES. Lastly, inadequacy of RANS for mixed type of flows has been highlighted.
DDES Numerical Investigations on Coherent Structures in Trailing-Edge Film Cooling Combined With Pressure-Side Film Hole
Authors: Xiao Xiangtao , Wang Pei , Du Qiang , Xu Qingzong , Liu Jun 
Published: September 2021

Abstract
The pressure-side cutback is used to design the trailing-edge film cooling. Previous studies have demonstrated the strong unsteady film mixing between the mainstream gas and the slot coolant, resulting in rapid deterioration of the film cooling effectiveness on cutback surface. The shedding vortexes formed by the clockwise and counter-clockwise structures induced by the mainstream and slot coolant shear-layer account for the strong blending. The RANS/LES hybrid turbulence model (DDES) has been proved to capture the locally unstable flows well. The flowfields and temperature of the cutback under eight blowing ratios Mslot = 0.3 ∼ 1.2 are simulated. With the increasing of blowing ratios, the counter-clockwise structures induced by the slot coolant shear-layer are strengthened to dominate the shedding vortexes gradually, which is corresponding to three kinds of coherent structures. Under low Mslot = 0.3 ∼ 0.5 dominated by clockwise structures of the mainstream, the effectiveness increases. Under middle Mslot = 0.5∼0.75 dominated by both clockwise structures of the mainstream and counter-clockwise structures of the slot coolant, the effectiveness decreases. Under high Mslot = 0.75∼1.2 dominated by counter-clockwise structures of the slot coolant, the effectiveness increases again. To weaken the blending at cutback, the pressure-side film hole with Mhole = 0.4 is arranged close to the cutback to rebuild the mainstream shear-layer. The weakened mainstream shear-layer and the assistant hitting of the hairpin vortexes from the hole injection can weaken the strength of the shedding vortexes at cutback, contributing to the improvement of the effectiveness on cutback surface under low Mslot = 0.5 and middle Mslot = 0.75. Under high Mslot = 1.0, the less influence of the hole injection on the shedding vortexes dominated by the slot coolant counter-clockwise structures accounts for slight improvement. Finally, FFT analysis is obtained for two configurations.