bluuebunny/crossref_metadata_2025_split huggingface dataset:
Uncertainty Quantification on the Cooling Performance of a Transonic Turbine Vane With Upstream Endwall Misalignment
Authors: Hao Mingyang , Li Yuanyuan , Li Zhigang , Li Jun 
Published: October 2022

Abstract
With increasing aerodynamic and thermal loads, film cooling has been a popular technology integrated into the design of the modern gas turbine vane endwall, especially for the first-stage vane endwall. A staggering amount of research has been completed to quantify the effect of operating conditions and cooling hole geometrical properties. However, most of these investigations did not address the influence of the manufacturing tolerances, assembly errors and operation degradations on the endwall misalignment. In this paper, therefore, uncertainty quantification (UQ) analysis was performed to quantify the impacts of upstream endwall misalignment uncertainties on the film cooling performance of endwalls as well as the phantom cooling performance of the vane pressure side surface.
The upstream endwall misalignment represents the step geometry between the combustor exit and the first-stage vane endwall. Based on the non-intrusive polynomial chaos expansion (NIPC) and the Uniform probability distribution assumption, the deviation (step height) uncertainties of the upstream endwall misalignment were quantified. To predict the endwall secondary flow and film cooling effectiveness in the transonic linear vane passage, the commercial CFD solver ANSYS FLUENT is used to numerically solve the three dimensional steady-state Reynolds-Averaged Navier-Stokes (RANS) equations. The robustness analysis of endwall film cooling performance and phantom cooling to the upstream endwall misalignment was conducted for three design upstream step heights (ΔH): a baseline configuration (ΔH = 0 mm), two misaligned configurations with forward step (ΔH = −5 mm) and backward step (ΔH = 5 mm) respectively.
Results show that the actual cooling performance has a high probability of deviating from the nominal value for the baseline configuration. The critical regions that are most sensitive to the upstream step misalignment are also identified by variances. The UQ results also show that the design geometry with a forward step has a more robust film cooling performance on endwall and phantom cooling performance on the vane pressure side surface which means a smaller variance and a better expectation than the no step configuration. In contrast, the design geometry with a backward step induces the reductions of the expectation of the film cooling effectiveness and coolant coverage and the amplification of performance fluctuations. This work provides a certain guiding direction for the optimization design for the upstream step geometry.
Calculating Windage Losses: A Review
Authors: Karg Bulnes Fernando , Kerr Thomas , Rimpel Aaron 
Published: October 2022

Abstract
Windage is the effect of aerodynamic drag on the surfaces of a rotating system due to fluid shear effects. The fluid-friction losses that occur on the rotor of rotating machines often constitute a non-negligible drag on the system that must be estimated for proper sizing of the driving or driven element. This is especially true in high-pressure environments, such as hermetic compressors and turbines. Fluid-friction loss modeling is based on the size and rotation speed of the shaft, the density of the fluid, and an empirically-determined drag coefficient. The drag coefficient is generally a function of the Reynolds number but may also be dependent on the Taylor number. Several papers have provided empirical predictions for drag coefficients based on the Reynolds and Taylor numbers of the fluid, but other factors such as rotor shapes, assemblies, and surrounding fluid conditions can also affect the drag coefficient. There are two main geometries for a rotor: a face parallel to the axis of rotation, and a face that is perpendicular. The gap between the rotating component and the stationary housing also plays an important role in the drag coefficient. This review summarizes and compares these findings in a way that makes it easy for the reader to predict the total windage losses on a system for any rotor shape, speed, or operating condition. A quick reference table is presented in the conclusions section.
CFD Based Investigation of Effects of Liquid Contamination on Dry Gas Seal Performance
Authors: Patil Abhay , Rimpel Aaron , Kurz Rainer 
Published: October 2022

Abstract
Previous studies identified liquid contamination as a major root cause of dry gas seal (DGS) failures and highlighted the need for model development to simulate the liquid-gas interaction and its effect on DGS operation. The current study presents Computational Fluid Dynamics (CFD) based performance prediction of a DGS under single-phase (gas) and two-phase (gas-liquid) flow conditions. The presented numerical model includes the conjugate heat transfer (CHT) analysis for the three pressure conditions at a constant rotational speed. Initial modeling involved the qualification of different turbulent models by analyzing and comparing leakage flow, torque, and temperature distribution. The two-phase CFD model employs the Eulerian approach to predict the oil distribution and modified pressure and temperature predictions. Two-phase flow simulations focused on improving the understanding of oil distribution as a function of droplet size at the imposed inlet volume fraction and the consequential effect on the seal performance parameters. The presence of liquid causes localized pressure and temperature change while flow transitions from the cavity to the seal area. Also, two-phase interaction due to oil presence increases heat generation and consequential temperature rise in the pressure dam region. Overall, the systematic variation in performance parameters with liquid fraction provides greater insight into DGS performance, also laying out a path for establishing an incipient failure mechanism that will be validated in future testing.
The Effects of Swirling Flows in Entropy Wave Convection Through High Pressure Turbine Stage
Authors: Pinelli Lorenzo , Marconcini Michele , Pacciani Roberto , Notaristefano Andrea , Gaetani Paolo 
Published: October 2022

Abstract
First stages of aeronautical high-pressure turbines are subjected to significant inlet distortions generated by the combustor system. These disturbances are characterized by velocity and temperature fluctuations convected downstream by the flow. Such perturbations are commonly defined as vorticity and entropy waves and interact with the turbine stages affecting the aerodynamic performance, the heat exchange and generating indirect noise. Moreover, the presence of a swirling flow highly influences the convection and migration of the entropy wave, thus its interaction with the stage. The paper presents an in-depth study of the impact of the swirling flows on the entropy wave evolution by means of experimental campaigns and numerical simulations. Experimental campaigns have been carried out at Politecnico di Milano where a high-pressure turbine rig was equipped with a novel combustor simulator able to generate entropy waves and swirl profiles. Numerical simulations have been performed at the University of Florence by applying time accurate simulation schemes, including incoming disturbances, implemented in the CFD TRAF code. Two different entropy waves (featuring frequencies of 10 and 110 Hz) injected in a counterclockwise swirling region at midspan have been analyzed at two clocking positions: passage aligned and vane aligned. An excellent agreement is found between experimental acquisitions and numerical results: both show an important reduction of the temperature fluctuations through the stage and highlight the effect of the swirling profile on secondary flows and blade wakes. The extensive comparison reported in the paper validates the numerical approach (based on URANS simulations post-processed by a dedicated filtering technique) which has been further applied to study the impact of swirling flows with an opposite rotation (clockwise). The broad numerical investigation combined with the extensive experimental campaign leads to a deeper understanding of the aerodynamic, thermal, and acoustic implications related to entropy wave evolution in a swirling flow highlighting the interaction phenomena and suggesting how to minimize the impact of entropy waves by comparing the results of the different injection positions and swirling flow directions.
Secure Embedded Distributed Control and Instrumentation Architecture for Aircraft Propulsion Systems: Framework, Process, Methods, Challenges, and Opportunities
Authors: Behbahani Alireza R. , Costello John J. , Pakmehr Mehrdad , Skertic Richard J. 
Published: October 2022

Abstract
Cyberattacks on flight control systems could be disastrous. Unlike attacks against classical IT enterprise systems, attacks on flight control systems may influence physical processes and flight dynamics through digital manipulations. These digital manipulations can be catastrophic for safety critical systems such as propulsion and aircraft control systems. Many technical papers and presentations on improving aerospace turbine engine controllers over the last thirty years have explored the transition from a Federated Control System (FCS) to a Distributed Control System (DCS). These distributed architectures offer tremendous benefits for optimized control of gas turbine engines used for commercial and military aerospace platforms. DCS however, suffers from specific vulnerabilities which do not affect classical control systems. The networked architecture of DCS (i.e., communication between its distributed nodes) makes it vulnerable to multiple cybersecurity attack vectors. But this can be an advantage too, if the system is configured and designed properly. The vulnerabilities in the communication network of a safety critical system necessitates the need for the development of appropriate detection and identification techniques for cyber threats. Unfortunately, due to the immaturity of the various required technologies, and the risk mitigation that is typical in the aerospace industry. The transition to a distributed architecture has been slow. In this paper we explore one possible design approach and a framework to develop a more decentralized and distributed control system for gas turbine control. We discuss optimized system control methodologies and review the current state-of-the-art challenges and opportunities for the control system to consider new cybersecurity requirements for hardening the engine control system against vectored threats that could occur during system operation.
Dry Low NOx (DLN) Combustion System Operability Considerations
Authors: Angello Leonard , Noble Bobby , Steele Rob , Cohen Mitch , Emerson Benjamin 
Published: October 2022

Abstract
Modern gas turbines employ dry low NOx (DLN) combustion systems to reduce air pollution and meet stringent environmental regulations. Gas turbine DLN combustion systems operate in lean premix mode near the extinction limit. In this region, the quantity of fuel in the air/fuel mix at the burner is barely sufficient to sustain combustion at low flame temperatures. Safe and reliable operation of modern combustors near the flame extinction limit requires a number of vital elements: 1) an in-depth understanding of mechanisms that promote combustion stability at these extremely low fuel equivalence ratios, 2) precise manufacturing and repair of key combustion components with narrow design tolerances, 3) a reliable monitoring system to detect onset of instabilities in individual combustors, and, 4) protective measures that can implement corrective actions such as changes in fuel splits. Given these elements, operators often need to act proactively in preventing onset of excessive pressure oscillations and combustion-induced vibrations and flame instabilities.
The purpose of this paper is to educate plant engineers on gas turbine combustion systems for operational flexibility of modern gas turbine low-NOx combustion systems. The paper will describe technologies for monitoring, control, and methods for adjusting and optimizing system performance on natural gas fuels. This paper is directed at plant engineers. It presents several applications, with supporting data and photographs, to help this audience understand the core working principles of modern DLN combustion systems.
Reducing Fuel Burn Using SiC/SiC CMC HPT Vanes and Rotor Blades
Authors: Boyle Robert J. 
Published: October 2022

Abstract
Issues with using High Pressure Turbine SiC/SiC CMC vanes and rotor blades for future commercial aircraft engines to reduce fuel burn, and CO2 emissions are explored. The higher temperature capability of SiC/SiC CMC vanes and rotor blades enables higher values of T40 and OPR, which leads to smaller engine cores and lower SFC. Decreasing engine weight, especially for long range flights, can be as significant as decreasing cruise SFC in terms of reduced fuel burn. Specific work increases as T40 increases, and. engine core weight decreases. The work focuses on the first stage vane, and shows that film cooled SiC/SiC vanes are highly desirable. Otherwise, excessive vane thermal stresses are likely. Increases in T40 have accompanied increases in engine OPRs. This leads to small spans in the high pressure components. The effect of decreased spans on blade row efficiency is examined. Cycle analyses are presented which show the effects of changes in blade row efficiency on SFC and specific work.
Combined Cycle, Heat Pump, and Thermal Storage Integration: Techno-Economic Sensitivity to Market and Climatic Conditions Based on a European and United States Assessment
Authors: Vannoni Alberto , Garcia Jose Angel , Guedez Rafael , Sorce Alessandro , Massardo Aristide Fausto 
Published: October 2022

Abstract
The integration of a Heat Pump (HP) with a Combined Cycle Gas Turbine (CCGT) to control the inlet air temperature has been previously investigated turning out to be a promising technology to meet the requirements imposed by the current electricity generation systems in terms of efficiency and flexibility. If the HP is coupled with a Thermal Energy Storage (TES) in an Inlet Conditioning Unit (ICU), it can be exploited in different modes to enhance the off-design CCGT’s efficiency or to boost the power output at full load. Furthermore, fuel-saving would be reflected in avoided emissions. The optimal sizing of the ICU, as well as an accurate estimation of the benefits, is a complex problem influenced by several factors such as the local climate and electricity market prices. The paper aims to systematically investigate, by means of a Mixed Integer Linear Programming model for optimal dispatch, the feasibility of an ICU integration in different scenarios (EU and US), providing general rules for assessing the concept application in new sites all around the globe. Different electricity markets have been analyzed and classified according to the parameters describing the average and variability of prices, the interdependency with the gas market, the ambient temperature, or the local carbon pricing policy. The most favorable conditions are identified and the dependency of the optimal ICU sizing on the climate and the electricity market is highlighted. The concept appears to be highly profitable in the hot regions with high price variability with an NPV of around 60 M€. Additionally, even in less profitable conditions (i.e., stable low prices in a cold climate), the system is able to increase the operating hours and reduce the economic losses. The performances enhancement described does not imply any environmental cost in terms of CO2 emissions.
Evaluation of Adjoint Optimized Hole - Part II: Parameter Effects on Performance
Authors: Yoon Christopher , Gutierrez Daniel , Furgeson Michael T. , Bogard David G. 
Published: October 2022

Abstract
In a previous study from our laboratory, a computational adjoint based optimization method was used to design shaped film cooling holes fed by internal co-flow and cross-flow channels. The associated RANS computations predicted that the holes optimized for use with cross-flow (X-AOpt) and co-flow (Co-AOpt) would increase adiabatic effectiveness significantly compared to a baseline 7-7-7 shaped hole. Experimental validations of these performance predictions are presented in companion paper (Gutierrez et al., 2022). Although the experimental values were significantly lower than the computational predictions, the adiabatic effectiveness for the adjoint optimized holes was measured to be noticeably higher than that for the baseline 7-7-7 shaped hole. Specifically, the X-AOpt hole was 75% higher and the Co-AOpt hole was 30% higher in terms of peak performance when P/D effects were accounted for. In this study, the effects of various key parameters on the performance of the adjoint optimized holes were determined. For these experiments the internal channel velocity ratios ranged from VRc = 0.2 to 0.4, both co-flow and counter-flow conditions were used, and the density ratio ranged from DR = 1.2 to 1.8. These provided a quantification of the performance of the adjoint optimized holes over a wide range of operating conditions encompassing engine relevant conditions. Adiabatic film effectiveness measurements and thermal field measurements are made to understand the performance variations and to compare with 7-7-7 SI (sharp inlet).
A Study of Stall Process in an Axial Flow Compressor With Foam Metal Casing Treatment
Authors: Li Jia , Sun Dakun , Xu Ruize , Dong Xu , Sun Xiaofeng 
Published: October 2022

Abstract
Recently, a kind of foam metal casing treatment (FMCT) was proposed and tested in a low-speed axial compressor. It was found that the FMCT performed well in both stall margin improvement and noise emission reduction of the compressor. The result is beneficial to the future advanced turbofan design. As a companion research, the goal of this paper is to give insight into the inner working mechanism of the FMCT in terms of unsteady pressure signal analysis across a range of operating points. The investigation is focus on pre-stall behavior of the compressor with/without the FMCT. Pressure measurements using high frequency response sensors have been carried out on the compressor to capture pre-stall process and interpret the flow structure in the blade tip region. A particular emphasis is given on the flow patterns present in the tip region and how they evolve in different casing wall conditions. The results show two different stall inception behavior throughout the throttling process. The compressor with the foam metal placed at the rotor mid-chord experiences a long-length-scale stall precursor. With smooth casing and the foam metal placed near the rotor leading edge, the compressor shows a short-length-scale stall precursor. The relevance of results obtained and possible mechanism involved are also analyzed and discussed at last.
Numerical Investigation of Loss Mechanisms in a Partially Loaded Supersonic ORC Axial Turbine Stage
Authors: Ziaja Karl , Post Pascal , Schramm Andreas , Willers Ole , Seume Joerg R. , di Mare Francesca 
Published: October 2022

Abstract
Industrial processes, small-scale power plants or internal combustion engines produce a high amount of waste heat as a by-product. The Organic Rankine Cycle (ORC) technology allows to recover that heat more efficiently compared to steam/water in conventional Clausius-Rankine cycles. For a comparably efficient and economical operation over a wide range of operating conditions, partial admission control appears to be a well-suited design option for ORC turbines. However, accurate numerical performance prediction of a partial admitted turbine stage is challenging and requires full annulus CFD computations of the partial admitted turbine stage.
In the present study, a comprehensive analysis of the internal flow and aerodynamic loss mechanisms in a supersonic, axial single stage impulse 18.3 kW ORC turbine operating with an ethanol/water gas-mixture as working fluid at a partial admission ratio of 40 % based on steady-state CFD computations is presented. A comparison of numerical and experimental results for a partial admission ratio of 20 % and 40 % shows, that for a partial admission ratio of 40 % efficiency predictions based on steady-state simulations are within the measurement uncertainty. To extract and quantify the magnitude of the occurring loss mechanisms, the entropy generation rate is analysed. The results show an entropy generation between the rotor blades and the closed stator passages, which has a significant influence on the turbine performance and leads to a reduction of efficiency of about 2 to 4.5 ppt. This was found to be related to a strong jet induced in the narrow gaps between the rotor leading edges and the trailing edges of the closed stator passages, which mixes with the stagnant flow in the following nozzle sections.
Highly Time Resolved, Combined Temperature and Heat Flux Measurement Technique Based on ALTP Sensors
Authors: Huber Konstantin , Rödiger Tim 
Published: October 2022

Abstract
This study demonstrates a new methodology for the simultaneous direct measurement of temperature and heat flux within the same sensing element of heat-flux sensors. The methodology is demonstrated for fast response ALTP-sensors and makes use of a temperature-resistance correlation. The new methodology enables an inherent comparison and validation of the heat flux density signal of ALTPs. Good agreement is found based on experiments in the stagnation point of a subsonic hot air jet. The results of the mainly convective heat flux densities are compared against a standard coaxial thermocouple indicating good agreement of mean values and signal characteristics. The simultaneous direct measurement of the temperature and heat flux allows the time resolved calculation of local heat transfer coefficients and Nusselt numbers. The spectral analysis of the Nusselt number exhibits an excellent signal-to-noise ratio.
Deformation and Damage Behavior of a 1 Cr-Cast Steel Under Multiaxial Loading at Elevated Temperatures
Authors: Kontermann Christian , Erbe Alexander , Conrad Fabian , Kraemer Karl Michael , Oechsner Matthias 
Published: October 2022

Abstract
Rising demands on material performance at high temperature in components under complex loading such as steam- and gas turbine housings require an increase in versatility and precision of component life modelling approaches. However, the database to calibrate those models is commonly derived from uniaxial testing. The impact of multiaxial loading, both proportional and non-proportional, is usually addressed theoretically by the use of equivalent stress/strain formulations or reduction ratios derived from few specific validation tests.
Therefore, a research program which systematically investigates the fatigue life of a 1Cr-cast steel both experimentally and theoretically has been initiated recently. For the experimental part, cruciform specimens are tested in a servo-hydraulic biaxial test rig equipped with an induction heating device. Each experiment is accompanied with finite element simulations before and after the test to parametrize the loading condition and derive equivalent loading parameters at hot-spot locations.
When assessing cycles until crack initiation in the experiments using the von Mises equivalent strain range, a reoccurring sequence in the impact of the axis ratio can be observed. Beside the fatigue life in terms of cycles to crack initiation, the multiaxial loading conditions may also affect the deformation behaviour, in detail cyclic softening. Such effects are discussed by comparing the produced experimental evidence with results gained from a unified constitutive material model. Furthermore, different lifetime parameters are applied in order to judge their accuracy and suitability for design applications.