bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of a Test Article for Acoustic Streaming in High-Speed Flow
Authors: Rahbari Iman , Butzen Michael , Twaddle James , Paniagua Guillermo 
Published: October 2022

Abstract
Acoustic streaming can provide a viable, lightweight solution to improve the heat exchangers’ capacity with a reduced drag penalty. The present work aims to develop a test article to experimentally create large-amplitude acoustic pulsations at high frequencies required for generating acoustic streaming and characterize its impact on the unsteady heat flux and shear stress within a narrow channel. Our combined computational and experimental approach iteratively produced multiple test sections. Instead of experimental testing, the CFD calculations to assess each design iteration reduce the effective geometry cost. the flow topology was assessed via CFD calculations. The final test model consists of two long hollow plates placed parallel creating a narrow channel within a larger flow area. As a result, three flow paths are created within the wind tunnel’s test section and the area ratio between the main and the bypass flow controls the Mach number within the narrow channel. The acoustic waves drive acoustic streaming and are generated by a shallow open cavity, which produces pressure oscillations with the dominant frequency of ∼8 kHz in a Mach 0.8 flow. Pressure taps and K type thermocouples monitor the pressure and temperature distributions over the walls while the total pressure and temperature are measured upstream of the plates. Kulite miniature pressure transducers measure the pressure fluctuations at high frequencies near the open cavity. Optical shear stress sensors are selected to monitor the unsteady wall shear stress immediately downstream of the open cavity. A thin film sensor array is designed for high-frequency wall temperature measurements which serve as the boundary condition for inverse heat flux calculations. High-speed Schlieren imaging is taken to visualize the flow structures near the cavity region. The experiments performed at the Purdue Experimental Turbine Aerothermal Lab indicate that the designed test article successfully reaches Mach 0.8. The open cavity creates the high-amplitude pressure pulsations at the frequency of ∼8 kHz. The successful commissioning sets the stage for future experiments to determine the potential of acoustic streaming as a low weight modification to improve compact heat exchangers.
A Microscale-Based Methodology to Predict the Performance Degradation in Turbomachinery due to Particle Deposition
Authors: Friso Riccardo , Zanini Nicola , Suman Alessio , Casari Nicola , Pinelli Michele 
Published: October 2022

Abstract
Solid particle ingestion is one of the main causes of gas turbine compressors degradation for both heavy-duty and aero-propulsion applications. Particles that enter the engine can stick to the internal surfaces and then form deposits. These, in turn, involve a change in the surface roughness and then performance deterioration. In the literature, several strategies have been proposed in order to account for the deposits effects on compressor numerical simulations. Among the others, the most used is the mesh-morphing strategy, which consists of the modification of the computational grid according to the particle deposition. Even though it is well suited for turbine fouling, the large computational costs and complexity of this strategy are not acceptable for compressor simulations. In this work, an innovative microscale-based approach has been proposed. An axial compressor deposition experiment from the literature has been considered as the reference case to test the reliability of the presented strategy. The main advantage of this approach consists of reducing both computational costs and numerical instability since it does not need the modification of the mesh. The deposition has been modelled by means of the OSU model and the roughness influence on the fluid flow has been accounted for by using the well-known sand-grain-roughness height (ks). Efforts have been made to find the ks correlation that best represents a fouled surface. The presented strategy enables the prediction of the fouling effects on axial flow compressors, and the prediction of the performance losses during the operation.
An Innovative Measurement Technique for the Direct Evaluation of the Isentropic Efficiency of Turbocharger Turbines
Authors: Marelli Silvia , Usai Vittorio , Cordalonga Carla , Capobianco Massimo 
Published: October 2022

Abstract
Turbocharging plays a key role not only in improving automotive engine performance, but also in reducing fuel consumption and exhaust emissions for Spark Ignition and diesel engines. In depth experimental investigations on turbochargers are therefore necessary to better understand their performance. The availability of experimental information on realistic turbine steady flow performance is an essential requirement for optimizing engine-turbocharger matching calculations developed in simulation models. This is most evident with regards to the turbine efficiency, as its swallowing capacity can be accurately assessed by measuring the mass flow, inlet temperature and pressure ratio across the machine. In fact, in the case of a turbocharger radial flow turbine, the isentropic efficiency evaluated directly starting from the measurement of the thermodynamic parameters at the inlet and outlet sections can give significant errors. This inaccuracy is mainly related to the difficulty of a correct evaluation of the turbine outlet temperature due to the flow field and the temperature distribution at the machine outlet.
The purpose of this work is to obtain a reliable measurement of the turbine outlet temperature thanks to a specific device installed before the standard measurement section to dissipate the flow structures dominated by vorticity, thus obtaining a uniform distribution of the flow fields and of temperature to the measurement section. This measurement allows to optimize turbocharger experimental performance implemented in simulation models, obtaining a better control of the after-treatment device generally adopted downstream of the turbine. To this aim, a non-intrusive 3-hole probe was adopted to perform measurement of the flow field, pressure, and temperature downstream the turbine. The main results obtained through the non-standard measurements are compared with those achieved through a direct measurement of turbine outlet temperature by three probes inserted in pipe with a different protrusion. The experimental campaign concerns investigations also developed in almost adiabatic conditions and to be adopted to carry out a realistic measurement of the turbine outlet temperature in a simpler and less time-consuming way.
Gas Turbine Combined Cycle Range Enhancer - Part 2: Performance Demonstration
Authors: Reboli Tommaso , Ferrando Marco , Gini Lorenzo , Mantelli Luca , Sorce Alessandro , Traverso Alberto 
Published: October 2022

Abstract
In the current energy scenario, gas turbine combined cycles (GTCCs) are considered key drivers for the transition towards fossil-free energy production. However, to meet this goal, they must be able to cope with rapid changes of power request, and to extend their operating range beyond the limits imposed by the environmental conditions in which they operate.
The European H2020 project PUMPHEAT [1] aims at achieving this goal thanks to the integration of the GTCC with a heat pump (HP) and a thermal energy storage (TES). Both HP and TES are used to condition the air flow at the gas turbine compressor inlet, thus modifying the whole GTCC power output and extending its operative range. To study this setup, a dedicated cyber-physical facility was built at the University of Genova laboratories, Italy.
The plant includes physical hardware, such as a 100kWel micro gas turbine, (mGT), a 10 kWel HP and a 180 kWh change phase material-based TES. These real devices are up-scaled thanks to performance maps and real-time dynamic models to emulate a full-scale heavy duty 400 MW GTCC with a cyber-physical approach. The three real key components (mGT, HP and TES) are run in the laboratory. Data collected by various sensors is monitored in real-time and used to feed both the simulated GTCC bottoming cycle model and the four-level control system. The control system determines the optimal configuration of the whole plant and the operative point of the real devices to minimize the mismatch with a real electric power demand curve.
With the aim of analyzing the performance of the facility and to assess the potential of the proposed GTCC range enhancer, different operative configurations are tested: one for reducing the power production of the plant below the minimum environmental load (MEL) and two for augmenting the plant maximum power at certain ambient conditions.
From the analysis of these tests it is possible to verify the effectiveness of the proposed concept and to characterize the transient behavior of the real components.
Evaluation of Surge Prediction Capabilities of Body-Force Model on a High-Speed Multi-Stage Axial-Radial Compressor
Authors: Zeng Hanxuan , Fan Tengbo , Sun Zhenzhong , Wang Baotong , Zheng Xinqian 
Published: October 2022

Abstract
Multi-stage axial-radial compressors are typical configurations of compression systems used in turboshaft engines. The aerodynamic instabilities encountered in this type of compressor are commonly identified as surge, which seriously threaten the operability and reliability of the compressor itself and even the entire engine. Therefore, correct prediction of surge characteristics and the aerodynamic loading are crucial during the design process. However, due to the complexity of compressor surge, high-fidelity numerical methods, like unsteady Reynolds-averaged Navier-Stokes (URANS) simulation, require enormous computational resources and time costs, which can barely be used in design iterations. Therefore, finding a more efficient way for surge prediction is essential.
This paper describes a general method of surge prediction based on an in-house code of body-force model. A high-speed multi-stage axial-radial compressor is used to evaluate the capabilities of this method to predict surge characteristics against URANS. The run-time is reduced by approximately 2 orders of magnitude. Key features of surge (i.e., flow reversal, flow resumption, and repressurization) and the aerodynamic loading during surge are compared. Overall, the results from the two method show a close matching. Additional analyses are also made on the fidelity limitations of this method in the prediction of finer surge features, and the corresponding modifications are proposed.
Exploiting GPU-Based HPC Architectures to Accelerate an Unsteady CFD Solver for Turbomachinery Applications
Authors: Poli Francesco , Marconcini Michele , Pacciani Roberto , Magarielli Donato , Spano Ennio , Arnone Andrea 
Published: October 2022

Abstract
Aircraft engine designers are nowadays facing more and more challenges: they strive to reduce fuel consumption, obtain better engine performance, and create quieter, safer, and environmentally friendlier products. One of the key factors to achieve these goals is the availability of numerical simulation tools able to accurately predict engine behavior and of hardware/software platforms where the tools can successfully run.
However, accurate numerical simulations, particularly unsteady Computational Fluid Dynamics (CFD) ones based on sophisticated solvers, are time-consuming and demanding in terms of hardware resources. This may limit the industrial applicability of these methods.
A possible strategy to overcome this problem is the acceleration of numerical solvers on advanced High Performance Computing (HPC) architectures, in order to reduce the execution time down to values compatible with industrial needs.
Traf is a CFD solver for steady/unsteady three-dimensional Reynolds-averaged Navier-Stokes equations. It is developed at the University of Florence, with a special focus on turbomachinery applications. The current production release is a parallel code that runs on CPU-based platforms.
A new version of Traf has been ported to and optimized for GPU-based HPC architectures, in order to dramatically accelerate CFD analyses. The code has been tested on an industrial-grade use case concerning a low-pressure turbine module for aeronautical applications in the context of the EU H2020 funded project LEXIS (Large-Scale Execution for Industry & Society, GA 825532), comparing its performance with the CPU-based release and obtaining promising results. To this aim, the speedup weighted to account for the different hardware cost is selected as a meaningful Key Performance Indicator (KPI).
Impact of Epistemic Uncertainty on Performance Parameters of Compressor Blades
Authors: Prots Andriy , Schlüter Lukas , Voigt Matthias , Mailach Ronald , Meyer Marcus 
Published: October 2022

Abstract
An well-established tool for probabilistic analysis is the Monte Carlo simulation (MCS), which can be used to gain insight into an unknown system behavior. The variability of the input variables is usually defined by parametric probability density functions (PDFs) or parametric cumulative density functions (CDFs). An example is the Gaussian normal distribution, which is characterized by its mean and standard deviation. When analyzing compressor blades, e.g. in the context of robust design optimization, the variation of profile variables such as chord length or stagger angle may be of interest. The distribution parameters are oftentimes obtained from a limited set of optical measurements. When performing the MCS, the distribution parameters must be fixed. However, the use of fixed parameters neglects the uncertainty and the effects resulting from the uncertain distribution parameters.
In this paper, the influence of epistemic uncertainty is illustrated using the example of compressor blades, which are subject to both manufacturing variability as well as wear and tear. Only a limited set of optical measurements is available. The resulting effect of the epistemic uncertainty is quantified using parametric probability boxes. The results of this approach are compared with the result from classical confidence interval analysis. This allows an estimation of the required number of measurements to achieve the desired statistical confidence.
Design Procedure of a Rotating Cavity Rig for Hot Gas Ingestion Investigation
Authors: Orsini Lorenzo , Picchi Alessio , Bonini Alessio , Innocenti Luca , Di Benedetto Daniele , Da Soghe Riccardo , Mazzei Lorenzo 
Published: October 2022

Abstract
This paper presents the design procedure and the setup of a Rotating Cavity Rig to investigate the problem of the high-pressure turbine main annulus flow ingestion into wheel-spaces. The single-stage test rig has been developed to run at cold flow conditions and it consists of a stationary and a rotating disk housing interchangeable cover plates to mimic different seal geometries. Thanks to such interchangeable covers, the rim seal configuration can be easily modified to investigate different arrangements and to perform optimization studies. Although some geometry simplifications are inevitable in scaled down models, such covers have been modelled as to represent a real engine rim seal as close as possible. Beside the standard pressure and CO2 concentration measurements inside the cavity, the rig implements optical accesses to exploit measurement techniques based on Pressure Sensitive Paints (PSP). Optical approaches will then be used to explore the rim sealing effectiveness on both stator and rotor disk under real engine representative operating conditions. CFD and FEM analyses run to support the rig design choices and to define its operating limits are hence highlighted and properly explained.
Numerical Study of Methane Pyrolysis Inside a Single-Channel Shock Wave Reformer
Authors: Mahmoodi-Jezeh S. V. , Tüchler Stefan , Madiot Ghislain , Davidson Mark , Akbari Pejman , Copeland Colin D. 
Published: October 2022

Abstract
The paper describes a numerical investigation of the thermal decomposition of methane to hydrogen and carbon within a single-channel, four-port wave rotor using a three-dimensional (3-D), Reynolds-averaged Navier-Stokes (RANS) CFD model. This work is in support of the New Wave Hydrogen, Inc. (NWH2) proprietary technology development. A Menter’s k-ω SST turbulence is used for the closure of the mean momentum equations and is coupled to multispecies transport equations with a one-step finite-rate chemistry model. The kinetic model is validated based on a set of measurement data of a double-diaphragm shock tube case. To further examine the predictive accuracy of the numerical approach, the results of the 3-D single-channel wave rotor are compared with those of quasi-one-dimensional unsteady model that has been previously reported extensively in literature. It is observed that when the wave rotor channel is exposed to the high-pressure driven gas (HPDRV N) port, a secondary right-running shock wave is generated, which greatly energizes the flow around the HPDRV N port, resulting in large magnitudes of pressure and temperature; and consequently, the cracking of methane into hydrogen and carbon. The comparison between 1-D and 3-D simulation results indicate that the LPDRV N gas penetration is around 75% of the channel width in the case of 1-D, but is below 50% in the 3-D case. Furthermore, the conversion rate of methane in the 3-D case is one order of magnitude smaller than that in the 1-D case.
Local Heat/Mass Transfer Measurements in a Shrouded Rotor-Stator Cavity
Authors: Choi Seungyeong , Lee Hee Jae , Heo Jeonghun , Park Hee Seung , Moon Hee-Koo , Cho Hyung Hee 
Published: October 2022

Abstract
Local heat/mass transfer and flow characteristics data applicable to the cooling design of the wheel space with rim seal in the gas turbine engine are essential. Experimental facility was designed to obtain local heat/mass transfer coefficients on stator and rotor surface in rotor-stator cavity with hub injection flows using the naphthalene sublimation method. This study investigated three configurations of rotor-stator cavity; unshrouded, shroud on rotor, and shroud on stator. The experiments were conducted for various rotational Reynolds numbers (ReΦ = 0, 5.6 × 105, 1.12 × 106), gap ratios (G = 0.03, 0.0375, 0.05) and non-dimensional flow rates (Cw = 7.0 × 103, 14.0 × 103). The local Sherwood numbers appeared similar in the circumferential direction, so the radial Sherwood numbers were analyzed. At low radius (r/b &lt; 0.4), the heat/mass transfer is dominated by the hub injection flow, and the Sherwood number on rotor and stator surfaces are similar due to small gap ratio (G &lt; 0.05). At large radius (r/b &gt; 0.5), the Sherwood number on rotor increase as rotational Reynolds number increases, however the Sherwood number on stator is independent. At the low opening ratio (Go = 0.17), the shroud increases the pressure in the cavity and reduces the Sherwood number regardless of the shroud installation location. Especially, at large radius, the Sherwood number on stator is reduced significantly. At the large opening ratio (Go = 0.5), there is no effect of the shroud on heat/mass transfer. And the shroud on the rotor enhances the overall Sherwood number on the rotor and stator under high injection flow conditions. Thus, the shroud clearly changes the flow and heat/mass transfer in the rotor-stator cavity at low opening ratio conditions.
Optimal Blade Design of Stator Based on Adjoint Fluid Topology Optimization Method in a Torque Converter
Authors: Tao Tianlang , Ke Zhifang , Wei Wei , Liu Cheng , Yan Qingdong 
Published: October 2022

Abstract
Traditional forward design method for blade of hydrodynamic torque converter is limited by empirical design so that it is difficult to produce innovative blade design results. Based on the adjoint sensitivity, an unconventional optimization blade design method, Adjoint Fluid Topology Optimization method was proposed. Based on this method, a directional topological optimization of stator blade design was carried out as an example to achieve a better torque ratio performance for torque converter under stalling condition. Such optimization method can achieve irregular stator blade with better performance. Moreover, the flow energy distribution before and after such topology optimization are further studied, the results show that the optimized torque ratio is increased by 9.99% under stalling condition when comparing with the original design result, and the irregular blade result has a more reasonable distribution of flow energy, indicating that fluid topology optimization can not only get rid of the restriction of forward blade design method and provide an innovation way for irregular blade design, but also improve the potential performance of turbomachinery.
An Evaluation of Passive Wall Treatment With Circumferential Grooves in a High-Performance Multi-Stage Axial Compressor
Authors: Bruno Díaz Rubén , Takachi Tomita Jesuíno , Bringhenti Cleverson , Tonon da Silva Daniel , Ferraz Cavalca Diogo 
Published: October 2022

Abstract
Passive wall treatments with circumferential grooves in axial compressors proved to be effective in increasing the compressor stall margin in previous researches by creating a resistance to the flow that leaks in the tip clearance region of the compressor, from the rotor blade pressure side to the suction side. In the present work, a passive wall treatment with circumferential grooves was implemented in a multi-stage axial compressor. Different configurations of circumferential grooves were created at the casing of the first rotor row used in a four-stage axial flow compressor. 3D CFD flow simulations were performed in order to evaluate all the specified configurations aiming to find improvements on compressor stall margin. Investigations on the compressor flow characteristics were realized and the stall margin variations were determined. The numerical simulations were performed based on the Reynolds-Averaged Navier Stokes equations and the turbulence model was the k-ω SST. After the simulations, several rotational speeds of the compressor map characteristics, including the design-point rotational speed, were obtained for the case without casing treatment (smooth wall case) and for the case with circumferential grooves. In the results, passive wall treatment with circumferential grooves demonstrated an improvement in the compressor stall margin, especially for N = 0.60 and N = 0.90 rotational speeds.