bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conjugate Heat Transfer Characteristics of Double Wall Cooling With Gradient Diameter of Film and Impingement Holes
Authors: He Juan , Deng Qinghua , Feng Zhenping 
Published: September 2021

Abstract
Double wall cooling, consisting of internal impingement cooling and external film cooling, is believed to be the most advanced technique in modern turbine blades cooling. In this paper, to improve the uniformity of temperature distribution, a flat plate double wall cooling model with gradient diameter of film and impingement holes was proposed, and the heat transfer and flow characteristics were investigated by solving steady three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with SST k-ω turbulence model. The influence of gradient diameter on overall cooling effectiveness and total pressure loss was studied by comparing with the uniform pattern at the blowing ratios ranging from 0.5 to 2. For gradient diameter of film hole patterns, results show that −10% film pattern always has the lowest film flow non-uniformity coefficient. The laterally averaged overall cooling effectiveness of uniform pattern lies between that of +10% and −10% film patterns, but the intersection of three patterns moves upstream from the middle of flow direction with the increase of blowing ratio. Therefore, the −10% film pattern exerts the highest area averaged cooling effectiveness, which is improved by up to 1.6% and 1% at BR = 0.5 and 1 respectively compared with a uniform pattern. However, at higher blowing ratios, the +10% film pattern maintains higher cooling effectiveness and lower total pressure loss. For gradient diameter of impingement hole patterns, the intersection of laterally averaged overall cooling effectiveness in three patterns is located near the middle of flow direction under all blowing ratios. The uniform pattern has the highest area averaged cooling effectiveness and the smallest non-uniform coefficient, but the −10% jet pattern has advantages of reducing pressure loss, especially in the laminated loss.
Estimation of Design Parameters and Performance for a State-of-the-Art Turbofan
Authors: Sjögren Oliver , Xisto Carlos , Grönstedt Tomas 
Published: September 2021

Abstract
The aim of this study is to explore the possibility of matching a cycle performance model to public data on a state-of-the-art commercial aircraft engine (GEnx-1B). The study is focused on obtaining valuable information on figure of merits for the technology level of the low-pressure system and associated uncertainties. It is therefore directed more specifically towards the fan and low-pressure turbine efficiencies, the Mach number at the fan-face, the distribution of power between the core and the bypass stream as well as the fan pressure ratio. Available cycle performance data have been extracted from the engine emission databank provided by the International Civil Aviation Organization (ICAO), type certificate datasheets from the European Union Aviation Safety Agency (EASA) and the Federal Aviation Administration (FAA), as well as publicly available data from engine manufacturer. Uncertainties in the available source data are estimated and randomly sampled to generate inputs for a model matching procedure. The results show that fuel performance can be estimated with some degree of confidence. However, the study also indicates that a high degree of uncertainty is expected in the prediction of key low-pressure system performance metrics, when relying solely on publicly available data. This outcome highlights the importance of statistic-based methods as a support tool for the inverse design procedures. It also provides a better understanding on the limitations of conventional thermodynamic matching procedures, and the need to complement with methods that take into account conceptual design, cost and fuel burn.
Computational and Experimental Studies of Model Fans for Advanced Turbofan Engines
Authors: Pankov S. V. , Korzhnev V. N. , Mileshin V. I. , Fateev V. A. 
Published: September 2021

Abstract
The paper presents the results of aeromechanical design of a large-scale model stage for a high-efficient low-noise fan designed for an advanced civil geared turbofan engines with ultra-low rotational speeds of rotor blades (313.4 m/s), high flow specific capacity (up to 202 kg/m2/s) and high bypass ratio (13.5). Total pressure ratio in the bypass duct of the fan model stage is 1.38.
To ensure the experimental studies, characteristics are calculated from choking to a surge line within a wide range of rotational speeds.
For the studies of the experimental fan model (EFM), a design project is developed and used in manufacturing a fan stage with 0.7-m rotor diameter for tests at the C-3A acoustic test facility.
The manufacturing technology for blades made of polymer composite materials (PCM) is of particular importance. Rotor blades of the geared fan model are made of PCM.
The analysis of experimental data and their comparison with the computation results within the range of corrected rotational speeds from 0.325 to 1.0 are presented. At first, only gas-dynamic and strength characteristics of the stage are studied. The analysis shows a good agreement of calculated integral parameters with the experimental data. Acoustic performances of the EFM will be studied later on.
Fouling Effects on Wet Gas Compressor Performance: An Experimental Investigation
Authors: Mæland Dagfinn , Bakken Lars E. 
Published: September 2021

Abstract
Achieving profitability in mature areas such as the Norwegian continental shelf forces the oil and gas industry to apply innovative solutions to increase oil recovery and to reduce both operational and investment costs. Wet gas compressors are promising machines for increasing oil recovery from existing fields and to allow for production from small satellite fields in the proximity of existing infrastructure. A prerequisite for successful implementation of subsea wet gas compressors high reliability. Knowledge of possible failure modes is important.
The effect of performance degradation due to fouling has been observed during wet gas compressor testing at K-Lab and has initiated further work to better understand and quantify the effects of fouling in wet conditions compared to dry conditions. A test campaign was conducted at the Norwegian University of Science and Technology (NTNU) to investigate the effect of fouled centrifugal compressor performance in both wet and dry conditions. The results documenting these effects are presented together with a proposed model for correcting the effects of fouling between dry and wet conditions.
Design and Validation of a Novel Turbogenerator’s Robotized Inspection System
Authors: Pignone Enrico , Pistone Alessandro , Canali Carlo , D’Agostino Fabrizio , Martorana Gianfranco 
Published: September 2021

Abstract
The inspection of power generators is a critical activity that will grow in importance during the next decades as operators are seeking solutions to continuously reduce outage duration and improve availability and reliability of the equipment. Automatic and systematic data collection on the status of health of the generator enables the possibility to implement predictive diagnostic/maintenance strategies and reduce the downtime due to repair activities. In this context robotic inspections play a crucial role since they allow a quick and efficient method to acquire data on the status of the generator. This paper describes an innovative robotic system that, thanks to a novel multi-sensor analysis method, is able to inspect and evaluate the overall status of power generators. The detection system, which is located on board a crawler robot, consists of inspection cameras, a micro-hammering system that is able to detect the acoustic response of fixing components of the generator bars and an Electromagnetic Core Imperfection Detection (EL-CID) sensor, which aims to detect insulation failures. Additionally, there is a description of how the robot has been designed to be adaptable to a wide range of different generators, and how it was tested and validated in the field.
Reconstruction of Temperature Distribution for a Turbulent Free Jet Using Background Oriented Schlieren
Authors: Wahls Benjamin H. , Ramakrishnan Kishore Ranganath , Ekkad Srinath 
Published: September 2021

Abstract
Background Oriented Schlieren (BOS) has been shown to be an excellent tool for qualitative flow visualization, and more recently, literature has shown that the technique can be expanded to yield quantitative measurements as well. In this study, a BOS setup was built to construct the temperature distribution of a heated turbulent free 12mm diameter jet near the nozzle. A 1080p DSLR camera was used to view a black and white speckled background plane through the heated free jet in question. Comparing images of the background with and without flow present using a cross correlation algorithm gave the apparent displacement of all points on the background viewed through the flow. Once this displacement field was obtained, a ray-tracing algorithm was implemented to reconstruct the refractive index of the center plane of the jet. Then, the Gladstone-Dale and ideal gas relations were combined and used to calculate the temperature of the center plane. Reynolds number, based on the jet diameter, was held constant at 6,000 for all cases, and steady state nozzle temperature was varied from 57°C to 135°C. Reconstructed temperature distributions were validated using K-type thermocouple measurements by allowing the system to reach steady state before acquiring data. Average agreement of 4–6% was observed between thermocouple and BOS measurements for axial locations of at least 30 mm downstream. Due to experimental error, accuracy decreases as axial location moves towards the nozzle, and as nozzle temperature increases. Improvements to the setup are being considered to improve the agreement in low accuracy regions. Further, this technique has the potential to be used to determine the temperatures in open and optically accessible closed reactive flows. Having information about near wall temperature in closed reactive flows will give insight into wall convective heat transfer characterization and will also help benchmark combustion based numerical models in applications such as gas turbines.
The Effect of Inlet Conditions on Turbine Endwall Loss
Authors: Coull John D. , Clark Christopher J. 
Published: September 2021

Abstract
There can be significant variation and uncertainty in the flow conditions entering a blade row. This paper explores how this variability can affect endwall loss in axial turbines.
A computational study of three cascades with collinear inlet boundary layers is conducted. Endwall loss varies by more than a factor of 3 depending on the inlet conditions. This variation is caused by dissipation of Secondary Kinetic Energy (SKE).
The results can be understood by observing that the inlet conditions predominantly control how secondary vorticity is distributed within the blade passage. Modestly-thick inlet boundary layers with high shape factor tend to displace vorticity towards the center of the passage. This displacement reduces vorticity cancellation, increasing secondary velocities and SKE.
A general method is formulated to estimate SKE in preliminary design. Optimum aspect ratio is shown to depend on the inlet boundary condition. Strategies to reduce endwall loss and minimize sensitivity to inlet conditions are then highlighted.
Erosion Evaluation of Gas-Turbine Grade CMC’s at Room and Elevated Temperatures
Authors: Eftekharian Amirhossein , Panakarajupally Ragav P. , Morscher Gregory N. , Huang Dade , Abdi Frank , Choi Sung 
Published: September 2021

Abstract
The objective of this study is to predict ceramic matrix composites (CMCs) erosion behavior and Retained Strength (RS) under environmental conditions using an Integrated Computational Material Engineering (ICME) physics-based approach.
The state-of-the-art erosion analysis using phenomenological algorithms and Finite Element Models (FEM) models follows a test duplication methodology and is not able to capture the physics of erosion.
In this effort, two CMC systems are chosen for Erosion evaluation: (a) Oxide/Oxide N720/alumina; and (b) MI SiC/SiC. Experiments are conducted at room and elevated temperatures (RT/ ET). Erosion testing considers: (i) a high velocity oxygen fuel (HVOF) burner rig for ET, and (ii) a pressurized helium impact gun for RT. Erodent particles are chosen as alumina and garnet. Experimental observations show that the type of erodent materials affects CMC erosion degradation at ET. Alumina exhibits to be an effective erodent for maintaining a solid phase particle erosion, while Garnet, experiences some degree of melting. Erosion of the oxide/oxide composite is more severe for the same erodent, temperature, mass, and velocity conditions than the MI SiC/SiC composite for all conditions tested. In general, increasing erosion temperature results in increasing erosion rate for the same erodent mass/velocity condition.
In conjunction with experiments, a computational Multi-Scale Progressive Failure Analysis (MS-PFA) is also used to predict erosion of the above-mentioned material systems at RT/ET. The MS-PFA augments FEM by a de-homogenized material modeling that includes micro-crack density, fiber/matrix, interphase, and degrades both fiber and matrix simultaneously during the erosion process. Erodent particles are modeled by Smooth Particle Hydrodynamic (SPH) elements. Erosion evolution in CMCs considering strain rate effect predicts a) spallation, b) mass-loss, and c) damages in fiber, matrix, and their interphase. ICME modeling is capable of predicting the erosion process and reproducing the test observation for the MI SiC/SiC at RT, where: a) erodent particles break up the layer of matrix covering fiber due to interlaminar shear (delamination); b) fiber is fractured because of brittle behavior; c) the process (erosion tunneling) continues till it gets to the next thick matrix layer that slows down the tunneling; and d) Erosion tunnel widens as exposed fiber layers are removed (eroded). Simulations are also performed for erosion of the oxide/oxide due to glass beads at RT and ET. Predictions show that erosion rate is lower at ET because voids in the CMC vanish and the glass beads are less effective at ET. Finally, prediction of retained strength of eroded CMC test specimens is predicted by MS-PFA.
A Semi-Analytical Model for Prediction of Wall Quenching Distances of Premixed Flames
Authors: Xia Huang , Weijie Liu 
Published: September 2021

Abstract
In order to predict the variation of the wall quenching distance of a premixed flame under different equivalence ratios and incoming flow velocities, a semi-analytical model applied to both lean single-layer flame and rich double-layer flame has been derived based on the conservation of energy in the quenching zone. In this model the flame surface radiation plays an important role. Factors influencing the radiation have been analyzed, respectively. The model indicates that the factors affecting the quenching distance in premixed flame are more complicated than that in single-wall flames or flames in tube. To fit the empirical coefficient in this model, a methane-air premixed flame quenching distance experiment under both lean and rich conditions has been performed. The comparison between the theoretical prediction and the experiment result shows that this semi-analytical model gives a suitable description of the quenching distance. The relative error of the quenching distance under different equivalence ratios and incoming flow velocities is less than ±15%.
Analysis of the Loss Production Mechanism due to Cavity-Main Flow Interaction in a LPT Stage
Authors: Barsi D. , Lengani D. , Simoni D. , Venturino G. , Bertini F. , Giovannini M. , Rubechini F. 
Published: September 2021

Abstract
In the present work URANS simulations are presented to describe the unsteady interaction process between the flow ingested/ejected from a cavity system and the main flow evolving into a Low Pressure Turbine stage. Particular care is posed on the analysis of the loss generation mechanisms acting outside the stator row and in the rear part of the axial gap separating the cavity flow ejection section and the leading edge plane of the downstream rotor row. The simulated geometry reproduces a typical engine cavity configuration, with upstream and downstream rotor rows reproduced by means of moving bars. Experimental results have been used to validate the simulations. This experimental data cannot explain and quantify alone the overall interaction process between the cavity flows and the main flow. The results of a simulation made by removing the domain of the cavity have been employed in order to better highlight and quantify the effects due to main flow and cavity flows interaction on total pressure loss. A deep inspection of the loss amount along the axial direction makes evident that losses generated in the vane row are basically increased prior to enter into the downstream rotor bars, due to cavity main flow interaction.
Investigation of Adjacent Lifted Flames Interaction in an Inline and Inclined Multi-Burner Arrangement
Authors: Shamma Mohamed , Hoffmann Sven , Harth Stefan Raphael , Zarzalis Nikolaos , Trimis Dimosthenis , Koch Rainer , Bauer Hans-Jörg , Langone Leonardo , Galeotti Sofia , Andreini Antonio 
Published: September 2021

Abstract
The main objective of this research is to assess an innovative, low nitrogen oxides emission combustor concept, which has the potential to achieve the long term European emissions goals for aircraft engines. Lean lifted spray flames and their very low nitrogen oxides emissions are combined with an inclination of burners in annular combustor leading to a more compact combustor with superior stability range. The presented combustor concept was developed in the frame of the European research project CHAIRLIFT (Compact Helical Arranged combustoRs with lean LIFTed flames). CHAIRLIFT combustor concept is based on “low swirl” lean lifted spray flames, which features a high degree of premixing and consequently significantly reduced nitrogen oxides emissions and flashback risk compared to conventional swirl stabilized flames. In the CHAIRLIFT combustor concept, the lifted flames are combined with Short Helical Combustors arrangement to attain stable combustion by tilting the axis of the flames relative to the axis of the turbine to enhance the interaction of adjacent flames in a circumferential direction. A series of experimental tests were conducted at a multi-burner array test rig consisting of up to five modular burners at different burner inclination angles (0° and 45°), equivalence ratios, and relative air pressure drop at ambient conditions. For all investigated configurations, a remarkable high lean blow out for non-piloted burners (ϕLBO = 0.29–0.37), was measured. The multi-burner configurations were observed having a superior stability range in contrast to the typical decrease in stability from single to high swirl multi-burner. The unwanted flow deflection of highly swirled flames in Short Helical Combustors arrangement, could be avoided with the investigated low swirl lifted flames. Moreover, the flame chemiluminescence (OH*) measurements were used to provide a qualitative characterization of the flame topology. Complementary numerical investigations were carried out using different numbers of burners to evaluate the effect of boundary conditions.
Film Cooling and Aerodynamic Performance on Multi-Cavity Squealer Tip of a Turbine Blade
Authors: Li Feng , Liu Zhao , Feng Zhenping 
Published: September 2021

Abstract
The blade tip region of the shroud-less high-pressure gas turbine is exposed to an extremely operating condition with combined high temperature and high heat transfer coefficient. It is critical to design new tip structures and apply effective cooling method to protect the blade tip. Multi-cavity squealer tip has the potential to reduce the huge thermal loads and improve the aerodynamic performance of the blade tip region. In this paper, numerical simulations were performed to predict the aerothermal performance of the multi-cavity squealer tip in a heavy-duty gas turbine cascade. Different turbulence models were validated by comparing to the experimental data. It was found that results predicted by the shear-stress transport with the γ-Reθ transition model have the best precision. Then, the film cooling performance, the flow field in the tip gap and the leakage losses were presented with several different multi-cavity squealer tip structures, under various coolant to mainstream mass flow ratios (MFR) from 0.05% to 0.15%. The results show that the ribs in the multi-cavity squealer tip could change the flow structure in the tip gap for that they would block the coolant and the leakage flow. In this study, the case with one-cavity (1C) achieves the best film cooling performance under a lower MFR. However, the cases with multi-cavity (2C, 3C, 4C) show higher film cooling effectiveness under a higher MFR of 0.15%, which are 32.6%%, 34.2%% and 41.0% higher than that of the 1C case. For the aerodynamic performance, the case with single-cavity has the largest total pressure loss coefficient in all MFR studied, whereas the case with two-cavity obtains the smallest total pressure loss coefficient, which is 7.6% lower than that of the 1C case.
Novel End-End System for Combustor Design and Analysis
Authors: Kannan Ashwin , Thewlis Jonathan , Keskin Akin 
Published: September 2021

Abstract
High quality geometry creation is a key step in the design process for complex modern turbomachinery subsystems such as an annular combustor assembly. In particular, parametric generation of 3D CAD geometry is an enabler for design studies and multi-disciplinary analysis. In a traditional approach, 3D CAD models are either created in a bespoke manner with respect to the engine of interest or if a parametric approach is used, the geometry is for one particular combustor configuration, which typically leads to insufficient flexibility for topological variations. In either of these cases for every combustor design, substantial manual efforts are involved in geometry creation as well as in geometry manipulation towards creation of a truncated sector model suitable for meshing and analysis. A more flexible and fully parametric approach in highly integrated and automated design processes during all product design phases is therefore necessary.
The present paper focuses on the exploitation and integration of a novel geometry modelling approach into an existing and well-established combustor design and analysis system called Prometheus in order to achieve a massive step toward a fully End-to-End (E2E) system. The new system is enabling rapid combustor design and analysis by combining feature-based geometry modelling approach that enables automatic creation of an analysis compatible combustor assembly with a geometry-centric optimization system. The automated design system can manipulate 3D geometry, to create necessary script files for meshing, simulation and post-processing for a typical CFD analysis, and execute the process to analyze different designs with respect to defined design objectives and constraints. The improved system enables engineers to assess different design concepts quickly early in the design process by providing best trade-offs between design objectives but also allows the use of detailed simulation models and boundary conditions in later more mature designs stages.
The paper will discuss the robustness and flexibility of the underlying parametric CAD approach, how it augments the downstream processes, which is able to handle and translate significant topological changes throughout the E2E system. It will also clearly demonstrate the efficiency gain of the automated combustor design process, which enables design engineers to make better decision faster.