bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inlet Flow Distortion in an Advanced Civil Transport Boundary Layer Ingesting Engine Installation
Authors: Hall D. K. , Greitzer E. M. , Uranga A. , Drela M. , Pandya S. A. 
Published: September 2021

Abstract
This paper presents first-of-a-kind measurements, and complementary computations, of the flow through the propulsion system of a boundary layer ingesting, twin-engine advanced civil transport aircraft configuration. The experiments were carried out in the NASA Langley 14- by 22-foot Subsonic Tunnel, using a 1:11 scale model of the D8 “double-bubble” aircraft with electric ducted fans providing propulsive power. Overall force and moment measurements and flow field surveys at the inlet and nozzle exit planes were obtained. The computations were carried out with the NASA OVERFLOW code. The measurements and computations were conducted for a range of aircraft angles of attack and propulsor powers representing operating points during the aircraft mission. Velocity and pressure distributions at the propulsor inlet and exit, and integral inlet distortion metrics, are presented to quantify the flow non-uniformity due to boundary layer ingestion. The distorted inflow exhibits qualitative and quantitative changes over the mission, from a unidirectional stratified stagnation pressure at cruise to a streamwise vortex structure at climb conditions. The computations capture these flow features and reveal the interactions between airframe and propulsor that create these three-dimensional flow variations.
Dynamic Mesh Adaption for Scale-Resolving Reacting Flow Simulations
Authors: Xia Yu , Stopford Phil , Sharkey Patrick , Verma Ishan 
Published: September 2021

Abstract
In this paper, a dynamic adaptive mesh refinement method is used in conjunction with a hybrid scale-resolving turbulence model to solve industrial combustion problems. The objective of the adaption method is to track and resolve characteristic turbulent structures arising from swirlers, pilot injectors and flame propagation in industrial burner configurations. By employing Polyhedral Unstructured Mesh Adaption (PUMA)® within Ansys Fluent® solver, local regions of mesh are refined to capture gradients in temperature, velocity and other key variables. For Scale-Resolving Simulations (SRS), highly refined meshes are required to resolve a sufficient range of turbulent scales. In this work, a strategy is proposed to evaluate the scale-resolving quality of the mesh and to refine it dynamically in a transient simulation. The condition used for adapting the mesh is based on the gradients of key variables such as temperature and velocity, whilst the large-scale eddies are resolved using an approach based on the LES mesh resolution index. This strategy is then applied to a series of test cases (a diffusion jet flame, a bluff-body premixed flame and a swirl stabilized flame), using the hybrid Stress-Blended Eddy Simulation (SBES) turbulence model and a Flamelet Generated Manifold (FGM) combustion model. The numerical results are compared with available experimental data, and the accuracy of the solutions is discussed.
Evaluating the Influence of Rotor-Casing Eccentricity on Turbine Efficiency Including Time-Resolved Flow Field Measurements
Authors: DeShong Eric T. , Siroka Shawn , Berdanier Reid A. , Thole Karen A. 
Published: September 2021

Abstract
The clearance that exists between the casing and turbine blade tips is one of the key drivers of efficiency in gas turbine engines. For this reason, engine manufacturers utilize precise manufacturing techniques and may employ clearance control systems to minimize tip clearances to reduce associated losses. Despite these efforts, turbines typically exhibit some nominal casing ovality or rotor-casing eccentricity, and changes to blade tip clearance during operation commonly occur due to thermal and mechanical stresses. The present study investigates non-axisymmetric tip clearance effects by creating a rotor-casing eccentricity in a one-stage axial test turbine operating in a continuous-duration mode at engine relevant conditions with engine representative hardware. A magnetic levitation bearing system was leveraged to move the turbine shaft to vary the rotor-casing eccentricity without test section disassembly. The results of this study indicate that rotor-casing eccentricity does not affect overall turbine efficiency over the range that was tested, but does locally influence efficiency and the rotor exit flow field. Comparisons of flow angle and secondary flow kinetic energy agreed with previous studies and existing analytical methods, respectively. Collectively, these results indicate that tip clearance can be studied locally on an eccentric rotor.
Selecting a Compressor Meridional Topology: Axial, Mixed, Radial
Authors: Smyth Jonathan M. , Miller Robert J. 
Published: September 2021

Abstract
This paper proposes a new duty-based Smith Chart as part of an improved method of selecting the geometric topology of compressors (axial, mixed or radial) in the earliest stage of design. The method has a number of advantages over previous methods: it is based on the non-dimensional flow and the non-dimensional work, which aligns with the aerodynamic function of the compressor and is therefore more intuitive than specific speed and specific diameter. It is based on a large number of consistently designed compressor rotors which have been computationally predicted using RANS CFD. Most importantly, it provides the designer not only with a choice of topology but also with the complete meridional geometry of the compressor, its blade design and the number of blades. This fidelity of geometry at the very early stage of design allows the designer to undertake a true systems design optimization (noise, manufacturing, packaging constraints and cost). This has the major advantage of significantly reducing early stage design times and costs and allows the designer to explore completely new products more quickly.
Investigation of Mistuned Oscillating Cascade Using Fully-Coupled Method
Authors: Phan H. M. , He L. 
Published: September 2021

Abstract
The uncoupled phase-shifted single-passage simulation is commonly used for turbomachinery aeroelastic problems. However, it has difficulties in dealing with unconventional phenomena such as strong fluid-structure interaction effects as well as blade mistuning effects. Regarding mistuning effects, structural mistuning has been studied extensively while aerodynamic mistuning has received far less attention. There seems to be a lack of clear and systematic understanding of physical behaviour and mechanisms of mistuned bladerows, particularly in the context of the aerodynamic mistuning versus structural one. In the present work, direct fully-coupled method is adopted to investigate the dynamics mechanism of a mistuned oscillating cascade. Both structurally and aerodynamically mistuned cascades show that the blades would couple and oscillate at a unique frequency and a constant inter-blade phase angle regardless of the individual blade’s eigen-frequency. The vibration amplitudes of blades of a mistuned row are different when excited. For structural mistuning, the mode localization effect is seen to be responsible for a monotonic increase of cascade aeroelastic stability with mistuning. On the other hand, the aerodynamically mistuned cascade shows a stabilizing effect at small amount of mistuning but exhibits a destabilizing effect at large mistuning. Such non-monotonic tendency could be explained using the aero-damping decomposition by the influence coefficient approach. At low reduced frequency, there is a striking difference between the tuned and aero-mistuned cascade. Although the tuned cascade is stable, the aero-mistuned cascade may experience flutter. A close inspection of the aero-mistuned cascade flutter reveals that there are two oscillating waves forming a beating signal.
Influence of Surface Roughness on the Flat-Plate Boundary Layer Transition Under a High-Lift Airfoil Pressure Gradient and Low Freestream Turbulence
Authors: Jeong Heechan , Song Seung Jin 
Published: September 2021

Abstract
Effects of surface roughness on the transition of flat-plate boundary layers under a high-lift airfoil pressure gradient with low incoming freestream turbulence level have been investigated. Time-resolved streamwise and wall-normal velocity fields with surface roughness values of Ra/C = 0.065·10−5, 4.417·10−5 and 7.428·10−5 have been measured at a fixed Reynolds number of 5.2·105 and freestream turbulence intensity of 0.2%. For the reference Smooth surface of Ra/C = 0.065·10−5, a laminar separation bubble forms from about 64% to 83% of the chord length. Displacement thickness increases downstream of separation and then decreases during the transition (reattachment), and momentum thickness increases due to the vortices shed from the separation bubble. Increasing surface roughness has little impact on the laminar boundary layer separation onset but reduces the height and length of the separation bubble and induces earlier transition. For Ra/C = 4.417·10−5, displacement thickness during transition is slightly thinner and the overall momentum deficit is slightly lower than those for Ra/C = 0.065·10−5. For Ra/C = 7.428·10−5, the separation bubble becomes hardly visible as the transition mode approaches the attached mode, and turbulent mixing by the wall-bounded turbulence becomes dominant. In addition, the portion of turbulent wetted area increases due to earlier transition, and momentum deficit increases more rapidly in the turbulent wetted area. Thus, the overall momentum deficit for Ra/C = 7.428·10−5 is larger than that for Ra/C = 0.065·10−5.
Thermodynamic Analysis of Waste Heat Recovery Systems in Large Waste Heat Generating Industries
Authors: Thada Shantanu , Rajan Yash T. , Pradeep A. M. , Sridharan Arunkumar 
Published: September 2021

Abstract
The accelerating growth of electricity demand necessitates looking for potential waste heat recovery solutions in production industries. Significant potential for efficient waste heat recovery is observed in the cement manufacturing industry. Based on the waste heat source temperatures in a cement plant, two potential candidates, the supercritical CO2 Brayton (S-CO2) cycle or the Organic Rankine cycle (ORC), promises low capital cost and enhanced thermodynamic performance. The current study focuses on modelling and optimization of the S-CO2 and ORC cycles for a 1 MTPA cement plant, with the raw-clinker preheater as the waste-heat source. The primary objective is to maximize the net-power output using genetic algorithms. A comparative performance analysis of the two ORCs with working fluids: R134a and Propane, the simply recuperated S-CO2 cycle (RC) and recompressed-recuperated S-CO2 cycle (RRC) configurations is presented with varying number of preheaters. For all cases, ORC-R134a yields more power than the ORC-Propane, RC, and RRC configurations. In terms of the waste heat recovered, ORC-Propane marginally outperforms ORC-R134a. The ORC configurations recover 32%–38% of the available heat, while the S-CO2 configurations recover, at maximum, 25%–30% of the available heat.
Bayesian Inference of Experimental Data for Axial Compressor Performance Assessment
Authors: Cruz Gonçalo G. , Babin Cedric , Ottavy Xavier , Fontaneto Fabrizio 
Published: September 2021

Abstract
As the next generation of turbomachinery components becomes more sensitive to instrumentation intrusiveness, a reduction of the number of measurement devices required for the evaluation of performance is a possible and cost-effective way to mitigate the arising of non-mastered experimental errors. A first approach to a data assimilation methodology based on Bayesian inference is developed with the aim of reducing the instrumentation effort. A numerical model is employed to provide an initial belief of the flow, that is then updated based on experimental observations, using an ensemble Kalman filter algorithm for inverse problems. Validation of the algorithm is achieved with the usage of experimental measurements not used in the data assimilation process. The methodology is tested for a low aspect ratio axial compressor stage, showing a good prediction of the corrected compressor map, as well as a promising prediction of the inter-row radial pressure distribution and 2D flow field.
A Numerical Study on the Influence of Hydrogen Addition on Soot Formation in a Laminar Aviation Kerosene (Jet A1) Flame at Elevated Pressure
Authors: Sun Mingshan , Gan Zhiwen 
Published: September 2021

Abstract
The hydrogen addition is a potential way to reduce the soot emission of aviation kerosene. The current study analyzed the effect of hydrogen addition on aviation kerosene (Jet A1) soot formation in a laminar flame at elevated pressure to obtain a fundamental understanding of the reduced soot formation by hydrogen addition. The soot formation of flame was simulated by CoFlame code. The soot formation of kerosene-nitrogen-air, (kerosene + replaced hydrogen addition)-nitrogen-air, (kerosene + direct hydrogen addition)-nitrogen-air and (kerosene + direct nitrogen addition)-nitrogen-air laminar flames were simulated. The calculated pressure includes 1, 2 and 5 atm. The hydrogen addition increases the peak temperature of Jet A1 flame and extends the height of flame. The hydrogen addition suppresses the soot precursor formation of Jet A1 by physical dilution effect and chemical inhibition effect, which weaken the poly-aromatic hydrocarbon (PAH) condensation process and reduce the soot formation. The elevated pressure significantly accelerates the soot precursor formation and increases the soot formation in flame. Meanwhile, the ratio of reduced soot volume fraction to base soot volume fraction by hydrogen addition decreases with the increase of pressure, indicating that the elevated pressure weakens the suppression effect of hydrogen addition on soot formation in Jet A1 flame.
Improved CFD Predictions of Pyrolysis Oil Combustion Using Advanced Spray Measurements and Numerical Models
Authors: van Beurden Eva , Pozarlik Artur , Putra Bima , Brem Gerrit , Bouten Thijs , Withag Jan , Axelsson Lars-Uno 
Published: September 2021

Abstract
In search of an economical and environmentally friendly manner of power generation the industry is forced to find fuels which can replace conventional fossil fuels. During the last years this has led to significant developments in the production of alternative fuels, whereby these fuels became a more reliable and more efficient source of energy. Fast pyrolysis oil (FPO) is considered as a promising example of one of the alternative fuels.
This research focuses on the application of FPO in a gas turbine combustion chamber. For the OPRA OP16 gas turbine, a numerical approach using advanced CFD simulations has been applied to a real scale gas turbine combustor. The simulations are supported by full-scale combustor tests and atomizer spray experiments. Hereby it has been shown numerically and experimentally that the gas turbine combustion chamber can operate on FPO in the 30–100% load range.
The droplet Sauter Mean Diameter (SMD) has been investigated by means of a Particle Droplet Image Analysis to visualize the sprays in the near field of the atomizer. The effects of the spray pattern are of key importance to the flame structure in the gas turbine combustion chamber. Therefore the results from this dedicated test experiment have been used as input for dedicated CFD simulations.
A dedicated combustion model of fast pyrolysis oil has been developed for the OpenFOAM code, considering both the evaporation of the oil and the burnout of the char. In the simulations the gas turbine electrical load, the cone angle and the droplet SMD of the spray were varied. These simulations provide a detailed insight and description on the evaporation of the pyrolysis oil and the flame characteristics in the low calorific fuel combustor of OPRA’s OP16.
On Choosing the Optimal Impeller Exit Velocity Triangles in Preliminary Design
Authors: Lou Fangyuan , Key Nicole L. 
Published: September 2021

Abstract
Impeller discharge flow plays an important role in centrifugal compressor performance and operability for two reasons. First, it determines the work factor and relative diffusion for the impeller. Second, it sets the flow into the downstream stationary diffusion system. The choice made in the preliminary design phase for the impeller exit velocity triangle is crucial for a successful design. The state-of-the-art design approach for determining the impeller exit velocity triangle in the preliminary design phase relies on several empirical guidelines, i.e. maximum work factor and diffusion ratio for an impeller, the optimal range of absolute flow angle, etc. However, as modern compressors continue pushing toward higher efficiency and higher work factor, this design approach falls short in providing exact guidance for choosing an optimal impeller exit velocity triangles due to its empirical nature as well as the competing mechanism of the two trends. In light of this challenge, this paper introduces a reduced-dimension, deterministic approach for the design of the impeller exit velocity triangle. The method gauges the design of the impeller exit velocity triangle from a different design philosophy using a relative diffusion effectiveness parameter and is validated using 6 impeller designs, representative of applications in both turbochargers and aero engines. Furthermore, with the deterministic method in place, optimal impeller exit velocity triangles are explored over a broad design space, and a one-to-one mapping from a selection of impeller total-to-total pressure ratios and backsweep angles to a unique optimal impeller exit velocity triangle is provided. This new approach is demonstrated, and discussions regarding the influences of impeller total-to-total pressure ratio, isentropic efficiency, and backsweep angle on the optimal impeller exit velocity triangle are presented.
Influence of Flow Coefficient on Ingress Through Turbine Rim Seals
Authors: Graikos Dimitrios , Carnevale Mauro , Sangan Carl M. , Lock Gary D. , Scobie James A. 
Published: September 2021

Abstract
Rim seals are critical in terms of limiting the temperature of highly-stressed engine components but function with a penalty to the power output and contribute to entropy gain stemming from mixing losses in the turbine. Ingress through rim seals is influenced by the presence of rotor blades and stator vanes, and the mainstream flow coefficient in the annulus that determines the corresponding swirl.
This paper presents an experimental study of ingress upstream and downstream of the rotor disc in a 1.5-stage rig with double radial clearance rim seals. Two rotor discs were used, one with blades and one without, and two platforms were used downstream of the rotor, one with vanes and one without. Tests were conducted at two rotational speeds and a range of flow conditions was achieved by varying the annulus and sealing mass flow rates. Concentration effectiveness, swirl and steady pressure measurements separated, for the first time, the influence of the blades and vanes on ingress over a wide range of flow conditions. Measurements on the downstream stator platform provide added insight into the complex interaction between the egress and the mainstream. Measurements of unsteady pressure revealed the presence of large-scale structures, even in the absence of blades. The number and speed of the structures was shown to depend on the flow coefficient and the purge flow rate.
Thermal Characterization of a Steam Turbine Casing Including Measuring of Adiabatic Wall Temperatures Using Proprietary Sensors
Authors: Weigel Bernhard Valerian , Odenbach Stefan , Uffrecht Wieland , Polklas Thomas 
Published: September 2021

Abstract
Modern steam turbines must increasingly be designed for flexible operation. However an increasing amount of cold starts and load changes have a massive impact on fatigue resistance of the material. So the monitoring of thermal parameters of the casing is significant for checking thermally induced stresses and furthermore lifetime calculation. Additionally the measurement data is helpful for CFD validation reasons.
This paper presents a new proprietary developed sensor setup and measurement results. The sensors are flush mounted into a steam turbine at different axial and circumferential locations in the recirculation area between the intermediate and the lower pressure turbine. Hence it is possible to detect temperatures, temperature gradients and heat flux in the part of the wall near the fluid. Moreover the field of temperature within the sensor can be modulated by powering an installed heater. So the adiabatic wall temperature can be identified. For measuring the temperature gradient, seven equidistant spaced thermocouples were used in difference circuit. Therefore two different types of thermocouples were applied. Both types have better transfer characteristics compared to a thermocouple of type K. High amplification enables monitoring of small differences in temperature. The temperature measures an integrated resistor thermometer.
The sensors are applied on a real 12 MW industrial steam turbine with maximal live steam parameters of 400 °C and 30 bar. The measurements show various operation points and load changes.
Development of a Multi-Shaker-Control to Investigate the Influence of the Interblade Phase Angle on Frictionally Damped Turbine Blades
Authors: Jäger Florian , Kaptan Ferhat , Panning-Von Scheidt Lars , Wallaschek Jörg 
Published: September 2021

Abstract
Constructive damper concepts are developed and integrated in turbomachinery to reduce vibration amplitudes generated by dynamic loads. The potential damping effectiveness of friction-based damper concepts is strongly dependent on the relative motion between adjacent blades, besides other factors such as normal force. In cyclic symmetric structures the phase difference is determined by the excited nodal diameter, which leads to different damper movements and efficiencies for given mode shapes. Several studies on the investigation of the damper performance of different underplatform damper geometries have been carried out on non-rotating test stands consisting usually of two blades in order to reduce the experimental effort before setting up rotational tests. Based on the existing modes of the two blades and the application of commonly just one shaker, the investigations are limited to the in-phase and out-of-phase modes. In this paper an experimental approach is developed to reduce the gap of transferability between non-rotating and rotational tests to analyze the effects of a variable interblade phase angle on the damping effect of underplatform dampers. For this purpose, a cascaded control system using two shakers is being developed to control the force amplitudes and the phase difference between the response of the two blades. The control algorithm is designed in a model-based way by using a two degrees of freedom oscillator with friction contact and is subsequently integrated in the non-rotating test stand.