bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mistuning and Damping of a Radial Turbine Wheel. Part 3: Validation of Intentional Mistuning During Machine Operation
Authors: Nakos Alex , Beirow Bernd , Wirsum Manfred , Schafferus Markus , Sasakaros Marios , Vogt Damian , Zobel Arthur 
Published: September 2023

Abstract
This contribution investigates the implementation and verification of intentional mistuning (IM) to a radial turbine wheel of an exhaust turbocharger. In principle, inaccuracies in manufacture or material inhomogeneities may lead to random blade mistuning and thus localized modes with severely magnified blade vibrations can occur. With regard to axial compressors and turbines, IM has proved to be an efficient measure to mitigate the forced response. For radial turbine wheels, on the other hand, a successful implementation of IM into a wheel hardware has not yet been presented. This work aims at the design, implementation, and verification of successful IM considering both measurements at standstill and test runs on a turbocharger test rig.
The fundamental analyses have been carried out in part one [1] of this three-part paper in order to find a suitable IM-pattern featuring only two different blade designs. The AABB sequence was identified to be the most promising one in terms of mitigating the maximum forced response of the fundamental bending mode at the considered operating point. In concrete terms, a 40% attenuation of the maximum forced response was predicted by employing reduced order models.
The second part [2] discussed the detailed geometric adaption of the turbine wheel hardware focussing on the implementation and validation of the IM pattern under laboratory conditions (standstill). Part three is about validating the efficacy of IM under operating conditions. In that sense, the successful implementation of IM and thus the machining of the wheel hardware are investigated within the framework of test runs on a turbocharger test rig. Test runs are conducted for both a wheel with and a wheel without IM. Non-intrusive blade-tip-timing (BTT) technology is employed to record forced response data. A well-known approach to evaluate the raw data namely times of arrival (TOA) without the availability of a once-per-revolution (OPR) signal is adapted, implemented, and applied for the evaluation. The results are compared to those received by using a commercial evaluation software for BTT measurement data. Finally, the actual gain achieved by means of IM is discussed in detail.
Impact of Effusion Hole Exit Geometry on the Cooling Performance of TBC Coated Surfaces in a High Temperature Combustion Environment
Authors: Snyder Kevin , Boguszewski Matthew , Cetegen Baki M. 
Published: September 2023

Abstract
This study examined the thermal characteristics and cooling performance of effusion cooling configurations by means of laser Rayleigh scattering (LRS) and infrared thermography. Combustor liners exposed to high temperature combustor flow in modern gas turbine engines are designed with advanced effusion cooling configurations to prevent damage and failure of the metal alloy. Thermal barrier coatings (TBCs) are applied to surfaces to reduce the thermal load on metal combustor liners. Effusion cooling hole geometries impact cooling performance and cooling film development. In this study, the impact of effusion jet hole blockage was investigated. An experimental test rig with a bulk vitiated crossflow of 1500K was used to study cooling performance of two effusion cooled plates: one with contracted effusion hole openings, and the other without. Carbon dioxide was used as the coolant over a range of blowing ratios (2.5–12) when the test rig reached quasi-steady operating conditions. Infrared imaging of the cooling array surface indicated higher temperatures for the contracted hole openings. LRS temperature imaging provided planar gas temperature measurements at three heights close the surface of the effusion plate. These gas temperature images were compared between the two plates and show differences in near-wall gas temperatures. The height of cooling film development and approximate near wall heat transfer characteristics were also obtained from these measurements. Average planar gas temperature images obtained in this study showed the plate without contraction allowed coolant to remain closer to the plate surface, improving convective cooling and reducing surface temperature and heat flux. Root-mean-square (RMS) deviation of instantaneous planar gas temperatures was also used to assess the stability of the cooling film at a given height above the surface.
Experimental Investigation of Broadband Noise Sources in a Swirl Stabilized RQL Combustor
Authors: Ha Sungyoung , Dhanasekaran Jananee , Bapat Archit , Acuna Amalique , Patel Shivam , Jo Seunghyun , Wu David , Emerson Benjamin , Steinberg Adam , Lieuwen Tim 
Published: September 2023

Abstract
This paper presents data collected from a model rich-burn, quick-quench, lean-burn swirl-injected single sector combustor. This is part of a larger effort to study the dynamics behind direct and indirect sources of combustor noise. Simultaneous acoustic pressure and OH* chemiluminescence were obtained over a range of conditions, particularly focusing upon the effect of air splits and fuel flow rates upon the broadband acoustic response. Acoustic pressure and chemiluminescence spectra were analyzed and coherence and correlation areas were estimated. Results demonstrate that the equivalence ratio at the primary zone has a significant impact on the frequency response. Higher equivalence ratios led to lower, low frequency broadband noise below 300 Hz but excited a narrowband mode at approximately 650 Hz. Differing the primary and secondary air split ratio but keeping the primary zone equivalence ratio constant showed no significant effect on the broadband noise. The chemiluminescence and acoustic signals showed weak coherence at all frequencies.
A Radio Frequency Polarimetry Sensor for Monitoring Rotor Shaft Position
Authors: Inoue Yuko , Perez Luis E. , Pratt Thomas G. , Morris Scott C. 
Published: September 2023

Abstract
Radio Frequency (RF) sensors are a novel, non-contact measurement technology that offers potential for engine health monitoring. A dual-polarized, distributed RF sensor system was considered here in order to provide information on rotor whirl in an axial compressor test facility. The amplitude of whirl was controlled using a magnetic bearing system. The RF sensor system provided time series information for each transmit/receive antenna combination and RF frequency. A large diversity of responses was observed across the different transmit/receive combinations and RF frequencies. Regression analysis was conducted using a multi-layer neural network. The results demonstrated that rotor whirl radius can be predicted from RF polarimentry measurements using a simple, artificial neural network based regression algorithm.
Investigation of Combustion Oscillation Modes of Hydrogen Micromix Flames
Authors: Kroniger Daniel , Kamiya Hiromu , Horikawa Atsushi 
Published: September 2023

Abstract
The micromix combustion principle is a dry low NOx combustion concept for high hydrogen fuels in gas turbines. In the can-type combustor, where multiple micromix flames are arranged circumferentially, a rotational thermoacoustic oscillation mode has been found. The objective of this study is to investigate combustion instabilities of generic micromix flames with an experimental setup and applying phase-averaged OH chemiluminescence imaging and an acoustic mode analysis. The low-frequency regime longitudinal mode found in the experiment at moderate overload (130%) could be reproduced by large eddy simulations (LES). The mean Rayleigh index and local pressure distribution identifies the initiation of the thermoacoustic instabilities inside the flame zone. A vertical high-frequency oscillation mode, wherein flames of opposed injection direction are interacting and distorting each other, has been experimentally found at high overload conditions (170%). Interestingly, the method of phase averaged imaging reveals that the frequency of the oscillation cycle is actually half of the frequency of the measured dynamic pressure.
High-Fidelity Computational Assessment of Aero-Thermal Performance and the Reynolds’ Analogy for Additively Manufactured Anisotropic Surface Roughness
Authors: Jelly Thomas O. , Abu Rowin Wagih , Hutchins Nicholas , Chung Daniel , Tanimoto Koichi , Oda Takuo , Sandberg Richard D. 
Published: September 2023

Abstract
Direct numerical simulations of incompressible turbulent forced convection over irregular, anisotropic surface roughness in a pressure-driven plane channel flow have been performed. Heat transfer was simulated by solving the passive scalar transport equation with Prandtl number Pr = 0.7. The roughness topographies under investigation here are based on an X-ray computed tomography scan of an additively manufactured internal cooling passage, which had an irregular, multi-scale and mildly non-Gaussian height distribution. Three different roughness topographies and three different friction Reynolds numbers (Reτ = 395, 590, 720) were considered, along with reference smooth-wall simulations at matched Reτ. By systematically varying the roughness topography and flow conditions, a direct computational assessment of aero-thermal performance (pressure losses and heat transfer) and the Reynolds analogy factor, i.e. 2Ch/Cf, where Ch is the heat-transfer coefficient (Stanton number) and Cf is the skin-friction coefficient, was conducted. The results highlight the profound impact that the roughness orientation (relative to the flow direction) has upon the aero-thermal performance of additively manufactured internal passages, with transverse-aligned roughness augmenting heat transfer by as much as 33%, relative to its streamwise-aligned counterpart. An interrogation of velocity and temperature statistics in the near-wall region was also performed, which underlined the growing dissimilarity between heat transfer and drag as fully-rough conditions are approached.
Investigation of the Aerodynamic Losses Caused by the Impeller/Volute Interaction in a Transonic Centrifugal Compressor
Authors: Reymond Loïc Marc , Geilich Marius , Stemmermann Julian , Jeschke Peter 
Published: September 2023

Abstract
The aerodynamic losses caused by the impeller/volute interaction in a transonic centrifugal compressor stage with a vaneless diffuser for turbocharger applications are numerically analyzed. In the operating point investigated a high volute mismatching induces an inhomogeneous pressure profile in circumferential direction with a pressure difference of up to 1 bar at the diffuser outlet, which corresponds to about 20% of the average pressure in this plane. This inhomogeneity propagates upstream and causes unsteady losses in the highly loaded impeller, which are investigated in detail. URANS simulations are conducted to enable a detailed analysis of the highly unsteady flow, evidenced by a high acoustic Strouhal number Sr = 0.18. To model the influence of the volute, an experimentally measured inhomogeneous static pressure profile is used as a boundary condition at the diffuser outlet. At the operating point investigated, the inhomogeneity reduces the time-averaged total-to-static stage efficiency Δηis,ts,4 by up to −1.2%, about two-thirds of which are caused by the impeller, as measured by the entropy increase. The analysis points out a large positive pressure gradient in the direction of rotation at the impeller outlet as the origin of these losses. An interaction region at the impeller outlet is identified using a velocity decomposition in the absolute and the relative frame of reference. The analysis shows that the interaction region impacts the flow inside the impeller significantly causing additional losses and that the identified loss mechanisms are of unsteady origin. Therefore, time accurate unsteady simulations are shown to be necessary for accurately predicting the losses in a centrifugal compressor with a high volute mismatching.
PIV Measurements in a High-Speed Low-Reynolds Low-Pressure Turbine Cascade
Authors: Okada Mizuki , Simonassi Loris , Lopes Gustavo , Lavagnoli Sergio 
Published: September 2023

Abstract
Particle image velocimetry (PIV) measurements in the blade-to-blade (B2B) plane and cascade outlet plane (COP) of a high-speed low-pressure turbine (LPT) cascade were performed. The measurements were performed at engine-representative outlet Mach number (0.70–0.95), and Reynolds number (70k–120k) under steady flow conditions. The freestream turbulence characteristics were imposed by means of a passive turbulence grid.
The PIV results on the B2B plane were compared against five-hole probe (5HP) and Reynolds-averaged Navier-Stokes (RANS) computations to assess the validity of measurement and simulation techniques in the engine-relevant LPT cascade flows. The PIV captured the wake depth and width measured by the 5HP whereas the RANS displayed an overprediction of the wake Mach number deficit. The 5HP was found to impose sinewave fluctuations of the measured flow angle downstream. The variation of fluctuation captured by the PIV was around three times lower. In addition, PIV provided an estimation of the turbulence intensity (TI) in the cascade passage, displaying a decay along a streamline following the passage curvature. For the highest Mach number investigated, a peak in the TI was measured past a shock wave.
Measurements of the outlet flow field highlighted a high TI in the secondary flow region whereas high degree of anisotropy (DA) was registered in the boundary of the secondary flow and freestream regions. The contribution of the streamwise fluctuation component was found to be less than the crosswise and radial components in the freestream region. Increasing the cascade outlet Mach number, the contribution of streamwise fluctuation to the DA was observed to decrease.
Turbomachinery Transient Dynamics of Radial Rotor-Stator Contact Occurrences With Friction
Authors: Jacobs Coline , Legrand Mathias , Thouverez Fabrice , Almeida Patricio 
Published: September 2023

Abstract
The present paper focuses on the numerical investigation of the transient response of a rotorshaft affected by unilateral contact occurrences with friction mechanisms. Rotor-stator contact is initiated radially at the shaft level. The components are modeled under the rigid bodies assumption and the rotor dynamical response is investigated in the time domain. The turbomachine is assumed to be driven by two torques: the first one is prescribed while the second one is induced by friction using Coulomb’s model. Particular attention is paid to the accurate prediction of the unknown rotational speed transient. The proposed methodologies are grounded on the Carpenter and Moreau-Jean time-marching algorithms, implying the use of Lagrange multipliers to solve the frictional and unilateral contact conditions. The simplest procedure considers only sliding friction while the most sophisticated one involves convex analysis in order to deal with normal and friction forces independently is case of stiction. The solutions predicted by the algorithms are compared and show good agreement. The sensitivity study on the stator properties and friction coefficient allows the identification of the conditions affecting the rotational speed limitation. Based on the response post-processing in the time and frequency domains, it is found that a higher friction coefficient, a stiffer stator support or a lighter stator leads to a decrease of the rotational speed maximum value.
On the Impact of Core Flow Inlet-Guide-Vanes on the Tonal Noise Signature of a Turbofan Engine
Authors: Blazquez-Navarro Ricardo , Node-Langlois Thomas , Thisse Johan , Nybelen Laurent , Cunha Guilherme , Yannic Baptiste , Chirico Giulia , Altuna Villanueva Gorka 
Published: September 2023

Abstract
Fan noise is one of the major aircraft noise sources at most operating conditions, featuring broadband and tonal contents. Tone noise is typically caused by the periodic interaction between the fan wakes and the outlet-guide-vanes (OGV). Additionally, a fraction of the wakes enter the primary flow. These impinge on the inlet-guide-vanes (IGV), leading as well to sound generation. Nevertheless, this noise mechanism is usually neglected due to the smaller size of the IGV compared to the OGV. This study numerically assesses the contribution of the IGV to the tone noise footprint on the ACAT1 test vehicle, a modern scaled-down fan, experimentally analysed in 2018 within the TurboNoiseBB project. The noise prediction methodology consists of the use of an extensively validated uRANS solver, chained to an acoustic post-processing to extract the acoustics. A vast number of simulations have been performed, at different operating points, and working lines, to provide a complete assessment of this phenomenon. For each operating condition, three configurations have been simulated: the complete assembly with the fan rotor, OGV and IGV, a configuration without IGV and a configuration without OGV. The noise footprints of those three computations have been compared to derive the contribution of the IGV. Surprisingly, the IGV lead to high noise levels and result in the dominant source of noise at most operating conditions, in the forward and rearward arcs. The strong hub secondary flows and an in-phase impact of the wakes on the IGV seem to be responsible for such an efficient noise radiation. These results cannot be compared with experimental data because the blade count of the OGV and the IGV of this test vehicle is the same, making it not possible to isolate the contribution of both components. Nonetheless, this work signals a potential risk of parasitic tone noise levels that could arise in current and future engines. There is a need for further research on this topic to confirm whether these conclusions are generalisable or not to real engines.
Scaling Overall Effectiveness in Low Temperature Experiments
Authors: Bryant Carol E. , Rutledge James L. 
Published: September 2023

Abstract
The design of film cooled engine components requires an understanding of the expected temperature distributions while in service, thus requiring accurate predictions through low-temperature testing. Overall effectiveness, ϕ, is the integrated indicator of overall cooling performance. An experiment to measure ϕ at low temperature requires appropriate scaling through careful selection of not only the coolant and freestream gases but also the model material itself. Matching ϕ requires that the experiment has matched values of the adiabatic effectiveness, Biot number, coolant warming factor, and ratio of external to internal heat transfer coefficient. Previous research has shown the requirements to match each of those four parameters individually. However, matching all those parameters simultaneously presents an over-constrained problem and no comprehensive recommendations exist for the practical experimentalist who wishes to conduct an appropriately scaled, low-temperature experiment truly suitable for determining ϕ. Four fluidic parameters are identified which in an experiment must be as close as possible to their values at engine conditions. A normalized root mean square difference (NRMSD) of the residuals of those parameters is proposed to quantify how well a proposed wind tunnel experiment is likely to yield engine relevant ϕ values. We show that this process may be used by any experimentalist to identify the appropriate fluids, conditions, and materials for a matched ϕ experiment. Several case studies were performed using computational fluid dynamics (CFD) to show the utility of this process. Of the common experimental techniques examined here, a matched Biot number experiment with 500 K freestream air and 250 K coolant appears to be particularly adept at simulating engine conditions, even better than experiments that make use of CO2 coolant.
GLDAN: Global and Local Domain Adaptation Network for Cross-Wind Turbine Fault Diagnosis
Authors: Peng Dandan , Desmet Wim , Gryllias Konstantinos 
Published: September 2023

Abstract
Operating under harsh conditions and exposed to fluctuating loads for extended periods, wind turbines experience a heightened vulnerability in their key components. Early fault detection is crucial to enhance the reliability of wind turbines, minimize downtime, and optimize power generation efficiency. Although deep learning techniques have been widely applied to fault diagnosis tasks, yielding remarkable performance, practical implementations frequently confront the obstacle of acquiring a substantial quantity of labeled data to train an effective deep learning model. Consequently, this paper introduces an unsupervised Global and Local Domain Adaptation Network (GLDAN) for fault diagnosis across wind turbines, enabling the model to efficiently transfer acquired knowledge to the target domain in the absence of labeled data. This feature makes GLDAN an appropriate solution for situations with limited labeled data availability. Employing adversarial training, GLDAN aligns global domain distributions, diminishing the overall discrepancy between source and target domains, and local domain distributions within a single fault category for both domains, capturing more intricate and specific fault features. The proposed approach is corroborated using actual wind farm data, and comprehensive experimental results demonstrate that GLDAN surpasses deep global domain adaptation methods in cross-wind turbine fault diagnosis, underlining its practical value in the field.
Computational Fluid Dynamics Analysis and Experimental Results for the Dynamic Performance of Two Long Smooth Surface Annular Seals Operating With a Liquid in Air Mixture
Authors: Yang Jing , Tran Dung L. , San Andrés Luis 
Published: September 2023

Abstract
Compressors in subsea oil and gas production must handle wet gases to reliably operate for extended periods of time. Annular clearance seals contribute to compressor performance and do affect system rotordynamic stability. Prior experimental work with two smooth surface, uniform clearance seals supplied with a light oil in air mixture and undergoing similar operating conditions produced direct stiffnesses (K) with distinct trends as the liquid content increased to 8% in volume. Both seals differ in length and diameter albeit having similar radial clearance. Other force coefficients for both seals, namely cross-coupled stiffness (k) and direct damping (C) increase as the inlet liquid volume fraction (LVF) grows. Rationale for the peculiar differences in centering stiffness (K) is missing. Hence, a computational fluid dynamics (CFD) model and its predictions, the thrust of this paper, unveil flow field details (pressure, velocity fields, and liquid content evolution) for the oil in air mixture. Besides the CFD model, an enhanced bulk-flow model (BFM) also predicts the seals’ leakage and dynamic force coefficients. Both models predict through flows agreeing well with the measured ones, the maximum difference is less than 16%. The BFM direct stiffness (K) does reproduce closely the experimental K whereas the direct damping coefficient (C) is up to ∼ 41% lower than the test result. The CFD model captures the variation trend of K vs. inlet LVF for the first seal, albeit its magnitude is thrice the experimental stiffness. The CFD C agrees well with the test data for both seals, the largest difference is less than 10%. In spite of the complexity of the CFD model, significant differences with the experimental results persist, in particular for K. When considering the seal inlet corner as round, the CFD model produces a significant reduction in K to better approach the test result for a seal supplied with air. Attention to the seal geometry is paramount to produce accurate predictions.