bluuebunny/crossref_metadata_2025_split huggingface dataset:
Research on Effect of Endwall Contouring of Vane Diffuser on Stable Operating Range of Centrifugal Compressor
Authors: Cui Qin , Qin Guoliang , Lei Jian , Wang Yi , Jia Cheng 
Published: August 2024

Abstract
The present investigation seeks to comprehensively analyze the impact of diverse endwall contouring strategies on the operational stability of a singular high-pressure ratio centrifugal compressor stage. Employing numerical simulation techniques, this study systematically examines the implications of contoured wall positions, specifically convex profiles at the pressure side and/or concave profiles at the suction side, as well as asymmetric endwall contouring, on both performance metrics and internal flow dynamics within the centrifugal compressor stage. And the stability enhancement mechanism of endwall contouring is clarified. The results demonstrate that employing full circular contoured vaned diffusers on the hub-side wall can achieve a maximum improvement in stall margin of 15.10%. Additionally, the diffuser featuring solely convex profiles at the pressure side on the hub-side wall exhibits an augmented stall margin by 8.39%, coupled with a reduction in performance loss at low flow rate conditions. The application of an asymmetric endwall contouring scheme improves stall margin by 8.39%, and mitigates the performance loss across the entire operating range. At the near-stall point, the contoured endwalls redirect fluid towards the suction side, thereby mitigating the incidence at the vane leading edge and attenuating the interaction between the impeller trailing edge vortex and the diffuser leading edge vortex. Moreover, concave profiles at the suction side serve to accelerate the fluid on the suction side along the flow direction, thereby suppressing the corner separation to weaken the passage blockages. Simultaneously, contoured endwall increases the negative static pressure rise within the flow channel away from the volute tongue. The advantages of endwall contouring in vane diffusers extend to the improvement in the circumferential nonuniformity of flow fields and the enhancement in diffuser stability. Consequently, this research lays the foundation for optimizing the flow control method of endwall contouring on the centrifugal compressor.
On a New Cyclic Symmetry Formulation Accounting for Boundaries Undergoing Nonlinear Forces
Authors: Quaegebeur Samuel , Thouverez Fabrice 
Published: August 2024

Abstract
Although cyclic symmetry theory was initially developed for linear structures, the introduction of nonlinear forces on internal nodes of the fundamental sector does not affect the methodology. Nevertheless, the method is ill-suited when nonlinear forces are applied at the cyclic boundary. The purpose of this paper is to provide a complement to this theory and to propose a cyclic symmetry formulation for structures undergoing nonlinear forces at their cyclic boundary. A complete nonlinear cyclic formulation for such systems is derived in this work. The advantages of such an approach lies in the reduction of computational costs using the cyclic symmetry properties.
The methodology is employed to characterize the dynamics of several mechanical systems. First, it is validated on simplified models of a cyclic system. Two nonlinearities are considered: a one-dimensional friction contact interface and a cubic nonlinearity. Both cases exhibit very different dynamics behaviors, yet, the results obtained with the new strategy are shown to be very accurate. Once the approach is validated, it is employed on a industrial finite element model of turbine bladed disk featuring contact interfaces between the blades’ shrouds. The capability of the method to handle large systems is thus demonstrated. For all cases, periodic excitation are applied following either a traveling or standing wave shape for different engines orders.
Spectral Heat Transfer Coefficient for Thermal Design Analysis - Part 1: Augmenting Law of Cooling for Non-Isothermal Wall
Authors: He Li 
Published: August 2024

Abstract
There are two major issues of interest in relation to Newton’s law of cooling. The first is its applicability for flow bounded by a non-isothermal wall where the surface temperature is non-uniform. The second is the restriction by the basic linear assumption. In terms of the first question, a general Green’s function-based framework exists but its implementation as a working method for practical applications has been lacking, attributable to the inherent locality of Green’s function. Instead of setting up and solving the local-local influence and response, a new Spectral Heat Transfer Coefficients (SHTC) method takes a different avenue. It sets up and solves global-to-local temperature-heat flux influences for a small number of low order spectral modes of wall temperature disturbances in a range of physically relevant and numerically resolvable length scales. The present work is aimed at applying the SHTC methodology to turbine blade aerothermal analysis. Two aerothermal regimes are considered respectively. In the first part (Part 1 of the two-part article), the SHTC approach is described and case-studied for a linear regime where the flow energy equation behaves linearly and the corresponding temperature field is passively dictated by the velocity field. In the companion paper (Part 2), the methodology will be extended to a nonlinear aerothermal regime, where the temperature field will be actively interacting with (rather than passively influenced by) the velocity field.
Flame Characteristics of a Piloted Single-Nozzle Hydrogen Lean Direct Injection (LDI) Burner
Authors: Dere Rojhat , Ezenwajiaku Chinonso , Balachandran Ramanarayanan , Talibi Midhat 
Published: August 2024

Abstract
In line with the global drive to decarbonise energy systems, there is an urgent need to develop new dry low-NOx (DLN type) combustion concepts to enable efficient utilisation of alternative fuels, such as hydrogen. New combustor configurations require a detailed study of flame behaviour, including stabilisation, structure and dynamics, as well as other performance parameters such as combustor emissions.
In this work, a piloted single-nozzle lean direct injection (LDI) burner was investigated where hydrogen was injected into the main air stream in a jet-in-crossflow configuration. Hydrogen was injected relatively close to the combustor inlet to create a partially premixed mixture in order to avoid flashback. The main flame was surrounded by 12 circumferential premixed hydrogen-air pilot flames. The flame stabilisation and the dynamics of the main flame were studied in the presence of the pilot flames, taking into account the complex interactions between them. The bulk air velocity of the main flame was varied from 30 m/s to 90 m/s, while the equivalence ratio was varied from 0.2 to 0.6. Two pilot schemes were employed; P1 - the pilot flow rate was kept proportional to the air flow rate of the main flame, and P2 - the pilot flow rate was kept constant irrespective of main air flow rate conditions. The equivalence ratio of the pilot was kept stoichiometric for both schemes. Flame structure and dynamics were evaluated from OH* chemiluminescence measurements utilising both, a photomultiplier tube and a high-speed intensified imaging system.
The lean blow off limit was observed to increase from 0.1 to 0.13 as the bulk air velocity was increased from 30 m/s to 90 m/s. At all bulk air velocities tested, the amplitude of the acoustic pressure oscillations was the highest at ϕg = 0.4 and decreased on either side (for richer or leaner mixtures). The results also showed that for a fixed main bulk air velocity, the flame stabilisation was characterised by extinction and auto-ignition events at low equivalence ratios (around 0.2 to 0.3), while for higher equivalence ratios, lifted flames were observed. The flame root and flame tip positions, estimated from OH* chemiluminescence images, increased as the global equivalence ratio was changed from 0.15 to 0.4, beyond which the flame root position decreased slightly while the flame tip position remained more or less at the same value. The results from this work will help develop a detailed understanding of the flame behaviour in lean hydrogen flames and hence inform design efforts towards the development of new architectures for stable, low-emission 100% hydrogen combustors.
Aerodynamic Optimization of an Axial Turbine Blade and Diffuser
Authors: Dasadhikari Kingshuk , Kimura Yasunori , Kuwamura Yoshihiro , Isoda Hokuto , Hiratani Fumito 
Published: August 2024

Abstract
This paper presents a multi-component optimization approach for improving overall performance of the axial turbine blade and axial-radial diffuser of a marine turbocharger. Blade throat-to-pitch distribution and diffuser passage shape are concurrently optimized, exploiting coupling between blade exit flow and diffuser pressure recovery to boost overall efficiency.
Algorithmic approaches are used for shape generation of both blade and diffuser. For the blade, a spanwise twisting and re-staggering approach fixing turbine mass-flow is adopted. For the diffuser, a NURBS-based process allowing for non-axisymmetric passages is developed by visual programming. Steady RANS CFD is used for aerodynamic evaluation and optimization is performed by a parallelized hill climbing method for both axisymmetric and non-axisymmetric passages.
The best design from concurrent optimization with axisymmetric passage achieves overall efficiency improvement of +0.49% (abs) compared to the base case. This performance is 40% higher than the combination of best blade and diffuser optimized individually. The best concurrently optimized design consists of a blade with triple-peak, W-profile throat-to-pitch distribution with more uniform mid-span flow and accelerated tip-side flow and swirl combined with a diffuser with 14% higher passage area ratio and 9% higher pressure recovery without sacrificing separation margin. Over 70% of efficiency gain is due to the blade, far exceeding the effect of passage shape. This design also retains its performance improvement under overloaded operation, showing viability for actual use. Best design with non-axisymmetric passage achieves +0.04% (abs) further improvement but shows little difference in terms of flow mechanisms.
This result shows the utility of this approach in exploiting coupled mechanisms between turbomachinery components. In future, this approach could support existing part-by-part design methods with greater understanding of the influence of interdependencies between components on overall performance.
Research on Performance Degradation Prediction Method of Heavy-Duty Gas Turbine Based on Data-Physics Fusion Under Uncertainty
Authors: Liu Yiyang , Jiang Xiaomo , Wei Manman , Ge Xin 
Published: August 2024

Abstract
Heavy-duty gas turbines (HDGT) have been widely used for power generation, because of their unique characteristics of high efficiency, low-emission, and flexible in rapid startup and shutdown. However, their main components such as compressor, combustion chamber, and turbine are usually operating under harsh environments such as high temperature, high pressure and high corrosion for a long time. The resulting fatigue, leakage, corrosion, or fouling in various components often lead to their performance degradation over the operating time, lowering the productivity of the gas turbine. Performance prediction becomes a powerful approach to monitor the degradation degree so that maintenance recommendation is provided to effectively ensure the efficiency and productivity of the machine.
This paper presents a new data-physics intelligent fusion approach for performance degradation prediction of HDGT under uncertainty. A thermodynamic heat balance model is first established to simulate component characteristics. The actual operating data of a real-world gas turbine are then employed for physics-based model assessment and parameters correction. Next, The deviation between expected performance data and actual heat balance value under the current operating point is utilized to assess the performance degradation. Finally, in order to consider the uncertainties in both the sensor signals and the prediction model, an improved Bayesian-LSTM (long short-term memory) model is proposed to predict multiple performance indicators by seamlessly integrating Bayesian variational inference with LSTM model. This method models each of the weight and bias parameters as a continuous distribution, rather than a constant. About half a year of sensor data collected from a 180 MW real-world gas turbine is utilized in a comparison study with the traditional LSTM models to demonstrate the superiority of the proposed method in predicting the performance trend of gas turbines. The proposed methodology can not only produce the predicted curve, but also obtain the fluctuation range of the prediction output to effectively consider the uncertainty in both the data and model, thus improving the robustness of the proposed model.
Investigations on Effects of Inflow Turbulence on Vortex-Induced Vibrations of a Wind Turbine Airfoil With the Wake Oscillator Model
Authors: Lian Bo , Tong Xin , Zhu Xiaocheng , Du Zhaohui 
Published: August 2024

Abstract
Design load and vibration for parked conditions are of utmost importance for large-scale modern wind turbines with increasing flexibility, especially edgewise vibration when the blade is at a high angle of attack. In this study, effects of inflow turbulence on vortex-induced vibration (VIV) of a wind turbine airfoil at 90 degrees of attack angle is examined. The study is carried out using the wake oscillator model, which is identified from the fluid-structure interaction (FSI) simulations. The turbulence induced dynamics is observed to be significantly distinct from that under uniform inflow and is heavily dependent on the turbulence intensity and mean velocity. The vibration response under inflow turbulence represents intermittency and broadband frequency characteristics near natural frequency and vortex shedding frequency since the inflow fluctuation drives the system to alternately enter and exit the frequency lock-in regime. In addition, Gaussian process regression is used to obtain a surrogate from input inflow conditions to output VIV loads. The results show that the incoming turbulence increases the risk of high amplitude vibration in the original low amplitude velocity regime, especially for high turbulence intensities. The conclusions may provide a new perspective for VIV response evaluation of the wind turbine under inflow turbulence.
A Fitting Process for the Optimal Modelling of an Anion Exchange Membrane (AEM) Electrolyser
Authors: Mennilli Francesca , Jin Lingkang , Rossi Mosè , Comodi Gabriele 
Published: August 2024

Abstract
Empirical and semi-empirical numerical models of electrolysers and fuel cells are used to predict their behaviour and study rapidly how the performance of a technology changes. Both the polarisation and efficiency curves are mainly dependent on both pressure and temperature and, with a few experimental data, it is possible to forecast the cell behaviour at different operating conditions without performing any additional tests. However, numerical models do not always resemble the system’s performance properly due to the lack of information on crucial parameters like the kinetics ones; indeed, these parameters are difficult to retrieve from the scientific literature and the manufacturers of such technologies. Starting from a semi-empirical model of an Anion Exchange Membrane (AEM) electrolyser from the scientific literature, this paper aims to provide a methodology to assess these parameters with a fitting process. Results showed that the use of fitted coefficients led to a better prediction of the AEM electrolysers behaviour. The model showed a better fitting of the activation and Ohmic regions lowering the Root Mean Square Error (RMSE) by 3.5%, moving from 0.065 V in the original model to 0.03 V in the fitted one.
CFD Meshing and Simulation Best Practices for a Turbine Stage With Squealer Tips, Trailing-Edge Cooling and End-Wall Cooling Injection
Authors: Hansen Thorsten , Munktell Erik , Scheuerer Georg , Zhuang Qingyuan , Zwiener Kim 
Published: August 2024

Abstract
The present study discusses and verifies workflows for simulating the flow through turbine stages featuring complex geometry like cooling holes at the hub and shroud surfaces, cavities upstream and downstream of the rotor, and rotor blades with squealer tips. Linne et al. [3] investigated such a configuration experimentally. Their experiments served as the test case for the present simulations. The geometric complexities forbid using mapped hexahedral meshes, the mesh elements of choice for standard geometries. Therefore, the first part of the paper investigates the use and accuracy of unstructured polyhedral meshes by comparing their accuracy and computational efficiency to hexahedral meshes on a reduced geometry model. The second part applied unstructured polyhedral meshes to the complete geometry model. The simulations showed that adding trailing edge cooling and rotor cavities prevents convergent steady-state solutions on the finer meshes. Rotor cavities and trailing edge cooling had a perceptible influence on the calculated isentropic efficiencies.
Investigation on the Effect of Resolving Waves Motion in the Simulation of Offshore Wind Farms
Authors: De Girolamo Filippo , Castorrini Alessio , Morici Vincenzo , Tieghi Lorenzo , Rispoli Franco 
Published: August 2024

Abstract
Offshore Wind Turbines (WTs) are characterized by heights that fall within the Atmospheric Boundary Layer (ABL). In ABL the flow is characterized by specific turbulence scales and velocity profile. The motion of the sea surface can influence turbulence in the surface layer, thereby impacting wake dynamics and recovery. In this study, we explore the role of wave modeling in the wake interaction between two wind-oriented IEA 15 MW reference WTs, modeled using the Actuator Line Method (ALM). Two hybrid LES-RANS simulations are carried out, one with a flat sea and the other with swell wave motion, imposed by a dynamic computational grid. Turbulence modelling relies on k-ω SST IDDES model, enabling the resolution of the large-scale turbulence associated with wind fluctuations and turbine wakes. The Kaimal velocity spectrum is here applied to generate stochastic velocity fluctuations superimposed as a time-dependent boundary condition to a neutrally stratified ABL velocity profile. Results showed that wind-aligned waves can induce an alternating up- and down-wash effect up to 50 meters from the sea surfaces, behaving as a modification (reduction) of the aerodynamic roughness. This effect is more evident in the wake flow. Analysing the performance of the downwind rotor, a 0.5% difference in power production is observed for the case with resolved waves motion.
Simulation of Full Featured Compressor Using Massive Parallel Unsteady CFD
Authors: Suhrmann Jan , Adami Paolo , Ganine Vladislav , Falcao Do Couto Alves Rigel , Reutter Oliver 
Published: August 2024

Abstract
A major benefit of using CFD in compressor design is reduction of test runs, which speeds up the design process and minimizes costs. This work presents the next step in achieving such a goal. Unsteady simulations of a high-fidelity full annulus compressor rig model with more than 5 billion mesh nodes were performed at part-speed conditions on tens of thousands of cores. Simulated geometric features included among others full cavity geometries, blade clearances and VSV penny gaps. For these comprehensive simulations, a modernized CFD solver was used demonstrating a speedup of more than 3X compared to its original version. This was achieved mainly through several optimizations that improved inter- and intra-node performance as well as through reduction of I/O. For post processing, the in-situ technique has been used to output 1D, 2D and 3D flow data at affordable time and disk usage. The results of these simulations were compared to state-of-the-art steady-state simulations of the same model as well as to the actual rig test data.
This example of one of the largest industrial-grade unsteady simulations to date demonstrates significantly improved capability of a modernized CFD solver as well as the opportunities and potential of using high-fidelity CFD models to improve and accelerate the compressor design process.
Centrifugal Compressor Design and Surge Simulation for Active Inference Based Control
Authors: Sathish Sharath , Khader Mahmoud , Sayma Abdulnaser , Shah Sunil 
Published: August 2024

Abstract
Among myriad industrial applications, the centrifugal compressor is a critical equipment in both upstream and downstream oil and gas production and processing facilities. In upstream applications, the varying properties (temperature, pressure, mass flow) of crude oil during the life of a reservoir coupled with different modes of operation (crude composition) emphasize compressor surge as a crucial factor in its design and operation. The surge constrains design leading to oversizing and higher capital costs. It also narrows the safe operating range during service, resulting in suboptimal performance and higher operating costs.
With its origins in neuroscience, active inference (AIF) is gaining traction in industrial applications involving sequential decision making under uncertain and noisy conditions. This paper proposes a novel AIF based advanced process control methodology for robust surge control under uncertain and noisy conditions. AIF based control offers several advantages over traditional methods like Proportional-Integral-Derivative (PID) and Model Predictive Control (MPC). It inherently integrates perception and action, allowing for more adaptive and context-aware decision-making in uncertain environments.
As a prelude to building an AIF surge controller, a natural gas centrifugal compressor is designed for a set of input specifications using a through flow model to generate characteristic or performance maps. The maps are then embedded in an ASPEN HYSYS® dynamic model to simulate operational conditions that result in surge. The key contributions of this paper are designing a natural centrifugal compressor prone to surge conditions due to highly uncertain suction conditions, integrating the compressor maps into a dynamic system model and simulating surge scenarios, and developing a methodology for AIF based surge control.
Aerothermal Performance of Slashface Leakage With Double Surface Angle Under Realistic Swirling Inflow
Authors: Li Zhiyu , Zhang Kaiyuan , Li Zhigang , Li Jun 
Published: August 2024

Abstract
The turbine vanes being manufactured and assembled piece by piece leads to an unavoidable gap on the vane endwall called slashface. Usually, the coolant leakage introduced from the slashface with a single surface angle aims to prevent hot gas ingression and protect the vane endwall. However, the cooling effectiveness is greatly reduced when considering the swirling flow from the combustor. In the current work, against strong swirling inflow, a new solution to improve endwall film cooling performance through applying the slashface leakage with the double surface angle is carried out. Through numerical method, the effects of the location of the angle transition region (D/L = 0%, 25%, 50%, 75%, 100%) and mass flow ratio (MFR = 0.5%, 1.0%, 1.5%) of the leakage on the turbine vane endwall aerothermal and film cooling performance are investigated. The results indicated that the coverage area of the coolant on the endwall was obviously enlarged when the slashface leakage with the double surface angle was employed. The film cooling level on both the endwall and suction side surface of the vane increased with increasing MFR. Moreover, the endwall thermal load was reduced. The designs of D/L = 25% and 50% are recommended for their high endwall film cooling level and low endwall thermal load. This paper provides turbine designers with a new idea to increase endwall film cooling performance by the slashface leakage with the double surface angle when considering aggressive swirling inflow.