bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reconstructing Compressor Non-Uniform Circumferential Flow Field From Spatially Undersampled Data: Part 2 — Practical Application for Experiments
Authors: Lou Fangyuan , Matthews Douglas R. , Kormanik Nicholas J. , Key Nicole L. 
Published: January 2021

Abstract
In the previous part of the paper, a novel method to reconstruct the compressor non-uniform circumferential flow field using spatially under-sampled data points is developed. In this part of the paper, the method is applied to two compressor research articles to further demonstrate the potential of the novel method in resolving the important flow features associated with these circumferential non-uniformities. In the first experiment, the static pressure field at the leading edge of a vaned diffuser in a high-speed centrifugal compressor is reconstructed using pressure readings from nine static pressure taps placed on the hub of the diffuser. The magnitude and phase information for the first three dominant wavelets are characterized. Additionally, the method shows significant advantages over the traditional averaging methods for calculating repeatable mean values of the static pressure. While using the multi-wavelet approximation method, the errors in the mean static pressure with one dropout measurement are 70% less than the pitchwise-averaging method. In the second experiment, the full-annulus total pressure field downstream of Stator 2 in a three-stage axial compressor is reconstructed from a small segment of data representing 20% coverage of the annulus. Results show very good agreement between the reconstructed total pressure profile and the experiment at a variety of spanwise locations from near hub to near shroud. The features associated with blade-row interactions accounting for passage-to-passage variations are resolved in the reconstructed total pressure profile.
Optimization of Airfoil Blend Limits With As-Manufactured Geometry Finite Element Models
Authors: Brown Jeffrey M. , Kaszynski Alex A. , Gillaugh Daniel L. , Carper Emily B. , Beck Joeseph A. 
Published: January 2021

Abstract
Conventional airfoil blend repair limits are established using nominal, design intent geometry. This convention does not explicitly consider the inherent blade-to-blade structural response variation associated with geometric manufacturing deviations. In this work, we explore whether accounting for these variations leads to significant differences in blend depths and develop a novel approach to effectively predict blade-specific blend allowables. These blade-specific values maximize the part repairability according to their proximity to defined structural integrity constraints. The methodology is demonstrated on the as-manufactured geometry of an aerodynamic research rig compressor rotor. Geometric point cloud data of this rotor is used to construct as-built finite element models (FEMs) of each airfoil. The effect of two large blends on these airfoils demonstrates the opportunity of blade-specific blend limits. A new approach to determine each airfoil’s blend repair capacity is developed that uses sequential least squares quadratic programming and a parametric blended blade FEM that accounts for manufacturing geometry variations and variable blend geometry. A mesh morphing algorithm modifies a nominal geometry model to match the as-built airfoil surface and blend geometry. The numerical optimization maximizes blend depth values within frequency, mode shape, and high cycle fatigue (HCF) constraint boundaries. It is found that there are large variations in blend depth allowables between blades and competing structural integrity criteria are responsible for their limits. It is also found that, despite complex modal behavior caused by eigenvalue veering, the proposed optimization approach converges. The developed methodologies may be used in the future to extend blend limits, enable continued operations, and reduce sustainment costs.
Analysis of Measured and Predicted Turbine Maps From Start-Up to Design Point
Authors: Scotti del Greco Alberto , Biagiotti Sara , Michelassi Vittorio , Jurek Tomasz , Di Benedetto Daniele , Francini Stefano , Marconcini Michele 
Published: January 2021

Abstract
This paper describes a coupled experimental and CFD campaign conducted on a 1.5 intermediate turbine stage in the full range of operating conditions, from start-up to design point under variable expansion ratio and physical speed. The test maintains engine similitude conditions and allows direct comparison with CFD data to assess the predictions accuracy. The choice of variables to describe the speedlines is also addressed by using both measured and predicted data. A discussion on velocity ratio versus corrected speed illustrates the advantages of the former parameter the adoption of which produces constant shape curves in a very wide range of operating conditions. The comparison between measurements and predictions suggests that CFD, in conjunction with performance correlations, is a viable tool to predict speedlines in a fairly wide range of conditions, provided that geometrical and operational details are carefully matched.
Investigation of a Rotor Blade With Tip Cooling Subject to a Nonuniform Temperature Profile
Authors: Kahveci Harika S. 
Published: January 2021

Abstract
One of the challenges in the design of a high-pressure turbine blade is that a considerable amount of cooling is required so that the blade can survive high temperature levels during engine operation. Another challenge is that the addition of cooling should not adversely affect blade aerodynamic performance. Besides, the tip region of a blade is exposed to further complexities due to tip leakage flow that is known to affect flow features and to cause additional pressure losses. The typical flat tips used in designs have evolved into squealer form that implements rims on the tip, which has been reported in several studies to achieve better heat transfer characteristics as well as to decrease pressure losses at the tip. This paper demonstrates a numerical study focusing on a squealer turbine blade tip that is operating in a turbine environment matching the typical design ratios of pressure, temperature and coolant blowing. The blades rotate at a realistic rpm and are subjected to a turbine rotor inlet temperature profile that has a nonuniform shape. For comparison, a uniform profile is also considered as it is typically used in computational studies for simplicity. The model used in the simulations is the tip section of the GE-E3 first stage blade. Two different configurations with and without cooling are considered using the same tip geometry. The cooled blade tip has seven holes on the tip floor lined up near the blade pressure side. The paper demonstrates the impact of the temperature profile nonuniformity and the addition of cooling on the complex blade tip flow field and heat transfer. Results confirm that these boundary conditions are the drivers for loss generation, and they further increase losses when combined. Temperature profile migration is not pronounced with a uniform profile, but shows distinct features with a nonuniform profile for which hot gas migration toward the blade pressure side is clearly observed. The blade tip also receives higher coolant coverage when subject to the nonuniform profile.
CFD–Aided Design Methodology for PCHE-Type Recuperators in Supercritical CO2 Recompression Power Cycles
Authors: Stamatellos George , Stamatellou Antiopi-Malvina , Kalfas Anestis I. 
Published: January 2021

Abstract
The supercritical carbon dioxide (sCO2) cycle has emerged as a promising power cycle for various types of power conversion systems, based on its high thermal efficiency, (approaching 60%), small-size and compactness. The recompression Brayton cycle with sCO2 is based on high capacity regenerators processing a large amount of heat making their effectiveness critical for the overall cycle efficiency. Printed Circuit Heat Exchangers (PCHEs) are used in these cycles because of their high attainable effectiveness values. The design process for these regenerators is demanding, considering the peculiarities of variation of CO2 density and thermal properties near the critical temperature. On the other hand, a reduced computation time is necessary for the quick assessment of alternative design options.
A hybrid design methodology for the high-temperature and the low-temperature recuperator (HTR and LTR) is presented in this paper, which employs 3D CFD conjugate heat transfer computation of the performance of a small two-channel module of the PCHE type. The results of the module computation are deployed in a 1D segmental method for the performance computation of the full heat exchanger’s channel length. Thus, the thermal effectiveness and pressure drop characteristics for the full heat exchanger are computed fast and with high accuracy. Application of the proposed methodology is carried out for the HTR and LTR computation in a recompression sCO2 Brayton cycle of a 600 MWth size power plant.
Design and Optimization of a Boundary Layer Ingesting Propulsor
Authors: Mandal Pritesh , Holder Justin , Turner Mark G. , Celestina Mark L. 
Published: January 2021

Abstract
The boundary layer ingestion concept has the potential to improve propulsion efficiency that will lead to better fuel economy of commercial aircraft. This design concept has been explored by NASA as the Single-aisle Turboelectric Aircraft with Aft Boundary-Layer propulsor “STARC-ABL.” This paper discusses the 1D-3D aerodynamic design and optimization process as well as the structural analysis of the rotor of a propulsor with incoming distortion. The propulsor is at the tail of the fuselage, and consists of an Inlet Guide Vane (IGV), Rotor, and Outlet Guide Vane (OGV). The design process presented accounts for only the large radial distortion and not the circumferential distortion. The paper also describes a pragmatic way of choosing orthogonal design parameters to proceed with the optimization process using a genetic algorithm. The final optimized design is highly dependent on the objective function to be optimized. A Modified Adiabatic Efficiency (MAE) has been defined to account for the loss of kinetic energy downstream of the propulsor CFD exit plane. This lost kinetic energy is essentially an approximation of the mixing loss of the tangential, axial and radial components of velocity at the OGV exit. The three blade-row adiabatic efficiency and MAE for an intermediate design case was 88.91% and 86.10% respectively. Upon further optimization and a different incoming distortion, using MAE as the objective function improved the MAE by 2.14% and adiabatic efficiency by 0.25% for the final design case presented in this paper. The rotor-only adiabatic efficiency for this case is 94.49%, the IGV-Rotor two blade-row efficiency is 92.71% and the Rotor-OGV two blade-row efficiency is 90.94%. The IGV is necessary to support the nacelle in this configuration. It also allows for the rotor work distribution to be optimized. The resulting rotor blade satisfies the static structural limit of a 1.1 safety factor for titanium at 110% speed. It also includes the pressure loads from the design point. The process uses an open source parametric blade generator whose source and input files for this geometry are on GitHub.
Process Automation for Aero Engine Secondary Air System Seal Design
Authors: Nasti Adele 
Published: January 2021

Abstract
Secondary air system seals are crucial in aero engine design as they have a direct impact on specific fuel consumption. Their behavior is affected by several aspects of the physics of the system: the air system, the engine thermal physics, the effect of flight loads and several other effects. As a consequence, their design is a complex and iterative process, which is highly dependent on the location of the seal in the engine, on the system requirements and on the system behavior.
This paper describes a methodology for multi-disciplinary assessment of secondary air system seals within an engine environment and supports standard seal design, trade-off studies on novel concepts and system-level optimization.
Defining the seal design intent for a specific engine location in the form of objectives, it is possible to embed process automation into traditionally manual multi-disciplinary design processes. This allows transforming modelling and simulation tools, which typically provide predictions for a specific seal design over reference cycles, into design and optimization tools, which can provide the optimum seal design for a specific set of requirements.
This approach provides predictive models of both seal performance and performance degradation and is capable of taking into account all sources of variation, for instance manufacturing variations or engine operating conditions, delivering a robust design, specific to the engine location.
The methodology enables a holistic approach to system and sub-system design and provides a deeper understanding of the impact of the seal onto system and of the system onto the seal, allowing optimization of the overall solution and informing the business case for introduction of different sealing strategies. Examples of the application of this methodology are provided for both labyrinth seals and leaf seals.
Design of a Mixed-Flow Transonic Compressor for Active High-Lift System Using a 3D Inverse Design Methodology
Authors: Wang Peng , Vera-Morales Maria , La Patrick , Zangeneh Mehrdad , Maroldt Niklas , Willers Ole , Kauth Felix , Seume Jörg 
Published: January 2021

Abstract
This paper presents the redesign of an electrically driven mixed flow transonic compressor by using a 3D inverse design methodology. The compressor will be used for an active high-lift system application that aims to delay the onset of stall and thus contributing to the reduction of both the aircraft noise footprint and the impact of aviation emission on local air quality.
As part of a collaborative work between the Institute of Turbomachinery and Fluid Dynamics of the Leibniz University Hannover and Advanced Design Technology Ltd., an existing optimized compressor stage for this application is redesigned using a 3D inverse method. The new compressor design presents an increase in pressure ratio and total-to-total isentropic efficiency of more than 5.5% and 1% respectively at design point. The higher PR at design point allows the compressor to be run at lower rotational speeds, which decreases the load on the electric motor and the power electronic systems, and hence contributing further to the overall weight reduction of the entire system.
The advantage of using an inverse design methodology is shown in this paper as a method that allows a very simple parameterization, reducing significantly the design time and hence allowing the exploration of wider design spaces, with the potential of reaching more innovative and efficient designs. The fast and reliable design and analysis of components represents an important advantage for the enhancement of aircraft electrification, where long design times are often a barrier for the exploration of system configurations.
Cycle Considerations for the Conceptual Design of a Pumped Heat Energy Storage System
Authors: Tom Brittany , Smith Natalie , McClung Aaron 
Published: January 2021

Abstract
Grid-scale energy storage technologies that provide greater than ten hours of electricity at full power are a critical enabler for full penetration of renewables on electricity grids worldwide. These technologies minimize renewable curtailment, while maximizing grid security and reliability. Other energy storage solutions such as pumped hydro and compressed air energy have geological and geographical constraints that widespread adoption.
Pumped Heat Electricity Storage (PHES) systems can store energy thermally in any location at the low costs necessary for displacing fossil fuels, reducing foreign fuel imports, and reducing emissions to maintain the energy security of the world. PHES systems operate in two modes, a charge mode in which the system operates as a heat pump to convert electricity into a thermal potential which is stored in a suitable storage media, and a discharge mode which uses a heat engine to convert the stored thermal energy to electricity. These systems offer a potential Round-Trip Efficiency (RTE) greater than 60%. This is a key parameter of interest for energy storage application systems, defined as the ratio between energy into the system to the energy retrieved.
Efficient PHES system design represents a compromise between thermal storage temperatures, system configuration, machinery selection, and minimization of secondary losses. This paper examines design trades associated with turbomachinery, system pressure ratio, and storage temperatures and the impact on RTE for a recuperated full scale PHES system progressing through conceptual design, and wraps up with turbomachinery evaluation and selection and resulting cycle for a small-scale system demonstrator used for demonstrating PHES system startup and operational control.
Computational Investigation of a Multiphase Turbo Expander for Heat Pumps and Refrigeration Cycles
Authors: Giakoumis Zoitis , Engelbrecht E. Geoffrey , Chasoglou Alexandros , Chokani Ndaona 
Published: January 2021

Abstract
The design and development of an innovative Tesla style turbo expander for two-phase fluids is proposed, as a substitute for the lamination valve of a traditional Heat Pump cycle. Thereby enhancing the overall performance of the Heat Pump, by recovering mechanical work to offset the compressor requirements. The major challenge in such configurations is the reliable operation of the expander, when phase change occurs across it, from a purely liquid flow to a mainly vapour flow by volume with a dense cloud of liquid droplets.
To investigate the phase change, a modelling approach is adopted which is routinely applied to modelling fuel-flashing in direct injection diesel engines, where the phase change deviates strongly from equilibrium. The Homogeneous Relaxation Model (HRM) is employed, which utilizes an Eulerian approach.
The proposed computational model is firstly validated against experimental results available in the literature. A sensitivity analysis of the phase change model relaxation parameter is performed. It was found that a value 10 times lower than the published value gave closer agreement to the measured results. It is believed that this result is due to the roughened walls of the experiment, which would produce more nucleation sites for vapour bubble formation. This suggests that this model maybe is sensitive to the geometry of the turbine.
Following this validation, the detailed flow profile in the proposed Tesla turbo-expander is investigated. Two different expander designs are considered in this project, one working with water [4,20] and the other with butane (R600). This study focuses particularly on the butane expander design. The expander performance is evaluated for rotational speeds up to 32’000 RPM.
Results on the turbo-expander under investigation, showed that the presence of a dense cloud of liquid droplets produces a significant pressure drop across the turbine rotor, which increases with RPM, postponing the phase change. High volume-fraction of liquid was predicted to penetrate deeper inside the rotor above 16’000 RPM for the butane expander. The resulting lower liquid flow velocity relative to the rotor disk speed at the inlet of the rotor is predicted to significantly degrade the performance of the turbine at high rotational speeds. Decreasing the nozzle throat area improves the situation, by initiating the phase change further upstream and increasing the RPM operational range by 50%. Angling the nozzle radially inward by 10° was found to not have a great impact on the performance of the turbine. It was determined from this study that it is critical to predict correctly where the phase change starts, in order to accurately predict the performance of the turbine. Important is to remove as much liquid as possible from the flow, before it enters the rotor, to minimize the impact of the phase change on the turbine performance.
Atomization of High Viscosity Liquids Using a Two-Fluid Counterflow Nozzle: Experiments and Modeling
Authors: Rangarajan Roshan , Zhang Hongyuan , Strykowski Paul J. , Hoxie Alison , Yang Suo , Srinivasan Vinod 
Published: January 2021

Abstract
We study the enhanced atomization of viscous liquids by employing a novel two-fluid atomizer. The nozzle establishes a countercurrent flow configuration in which the gas and liquid are directed in opposite directions, establishing a two-phase mixing layer. Detailed measurements of droplet size distributions were carried out using laser shadowgraphy, along with high speed flow visualization. The measurements suggest that the liquid emerges as a spray with little further secondary atomization. The performance of this nozzle is compared to the ‘flow-blurring’ nozzle studied by other investigators for four test liquids of viscosity ranging from 1 to 133.5 mPa.s. The counterflow nozzle produces a spray whose characteristics are relatively insensitive to fluid viscosity over the range studied, for gas-liquid mass flow ratios between 0.25 and 1. To gain insight into the mixing process inside the nozzle, simulations are carried out using an Eulerian-Eulerian Volume of Fluid (VoF) approach for representative experimental conditions. The simulation reveals the detailed process of self-sustained flow oscillations and the physical mechanism that generate liquid filaments and final droplets.
Identification of the Essential Features of the Transient Amplification of Mistuned Systems
Authors: Carassale Luigi , Denoël Vincent , Martel Carlos , Panning-von Scheidt Lars 
Published: January 2021

Abstract
The dynamic behavior of bladed disks in resonance crossing has been intensively investigated in the community of turbomachinery, addressing the attention to (1) the transienttype response that appear when the resonance is crossed with a finite sweep rate and (2) the localization of the vibration in the disk due to the blade mistuning. In real conditions, the two mentioned effects coexist and can interact in a complex manner. This paper investigates the problem by means of analytic solutions obtained through asymptotic expansions, as well as numerical simulations. The mechanical system is assumed as simple as possible: a 2-dof linear system defined through the three parameters: damping ratio ξ, frequency mistuning Δ, rotor acceleration Ω˙. The analytic solutions are calculated through the multiple-scale method.