bluuebunny/crossref_metadata_2025_split huggingface dataset:
Negative CO2 Emission Gas Power Plant As Technology for Utilization of Sewage Sludge, Production of Electrical Energy, and CO2 Capture - Case of Chamber Under Transpiration Cooling
Authors: Ziółkowski Paweł , Stasiak Kamil , Ditaranto Mario , Wiseman Samuel , Mikielewicz Dariusz 
Published: August 2024

Abstract
This work focuses on the concept developed in the nCO2PP project, which aims to demonstrate a technology that allows to achieve negative CO2 emissions through Carbon Capture and Storage (CCS) applied to sewage sludge. A feedstock is first gasified, then the resulting syngas is burned in a semi-closed oxy-fuel gas turbine with pure oxygen and water, using the advantages of oxy-combustion, to ease the capture of CO2 in the resulting exhaust gases. High-temperature combustion later takes place in a dedicated wet combustion chamber before expansion in a turbine which produces electricity. Given that in Polish law sewage sludge is treated as biomass, a negative CO2 emission factor is achieved. Works in the project are performed both in experimental and design terms. The concept of transpiration cooling will be considered in terms of different methods. Additionally, previously unpublished computational flow dynamics (CFD) simulations related to transpiration cooling were compared with measurement and design analyses. Experimental efforts include a demonstration of water transpiration through a porous structure.
A Real Time AI-Based Strategy for the Design of a Low-Pressure Turbine Profile
Authors: Bellucci Juri , Granata Angelo Alberto , Silei Mattia , Giovannini Matteo , Spano Ennio , Notaristefano Andrea , Lengani Davide 
Published: August 2024

Abstract
This paper focuses on the implementation of a data-driven, AI-powered design strategy for Low Pressure turbine (LPT) profiles.
The objective is to develop an effective LPT profile optimization environment, capable of rapidly generating a CFD calculation database to feed AI-based tools for subsequent phases of design space exploration. To achieve this purpose, an automatic workflow has been developed to create profile geometries, computational meshes, and perform URANS calculations. CFD results are then collected both in terms of overall performance (losses) and detailed flow field. AI-models are then trained over this large database, resulting in an accurate metamodel that can be effectively explored looking for specific design solutions. The paper will present and discuss the AI-based tool, showing how in addition to suggesting optimal geometries, it offers additional outputs to inform the designer. Indeed, the tool can provide optimal geometries that match mechanical and geometrical constraints providing performance at varying Reynolds number. Moreover, the blade-loading and the entire 2D flow field are predicted in real-time for the optimal geometry at a given operating condition.
Innovative Cavity Modeling for Centrifugal Compressors Aeromechanical Analysis
Authors: Batisti Marco , Pinelli Lorenzo , Toni Lorenzo , Guglielmo Alberto , Marconcini Michele , Arnone Andrea 
Published: August 2024

Abstract
Centrifugal compressor aeromechanics is playing an increasingly important role in the energy transition scenario, especially when operating with low molecular weight gases, such as hydrogen. For these machines, maximum impeller tip speeds are limited by structural requirements and so aeromechanical assessment must be included from the preliminary design stages. When performing forced response analysis of centrifugal impellers, it is mandatory to consider the contribution of the unsteady forces acting within front and rear cavities. The flow field inside the cavities has different time and length scales compared with the main flow field, and from a modeling standpoint seal regions have to be included in the computational domain: this means that a comprehensive Computational Fluid Dynamics (CFD) simulation may require substantial efforts for the setup and high computational time and resources. In this context, the paper presents an acoustic analytical model for predicting pressure perturbation within centrifugal compressor cavities without solving them with unsteady CFD approaches. The model is fed with appropriate boundary conditions to be applied at the entrance of the cavities and analytically solves the pressure perturbation distribution in an annular environment. To validate the presented analytical model, unsteady calculations were performed on impeller-vaned diffuser domains with cavities at different operating conditions, and the unsteady pressure field in the cavities was used as target solution. The comparison between the analytical model results and the CFD solution shows a very good agreement for all the different blade passing frequencies under investigation, paving the way for accurate aeromechanical evaluations in the preliminary design phase when complete unsteady CFD simulations are not compatible with design timing.
Aerothermal Optimization and Sensitivity Analysis of a Turbine Rotor Tip With a Circumferential Casing Groove Configuration
Authors: Li Weiqi , Tao Zhi , Song Liming , Li Jun , Feng Zhenping 
Published: August 2024

Abstract
The design of rotor tips is facing increasing challenges due to higher turbine inlet temperatures and blade loads. To tackle these issues, this study proposes a novel solution that integrates a circumferential casing groove (CG) configuration with a squealer tip. The CG is parameterized and integrated with an efficient global optimization algorithm, establishing an aerothermal optimization framework for the turbine rotor tip. Taking the stage efficiency and tip heat transfer coefficient as the optimization objectives, multiple representative optimized solutions for the CG configuration are obtained. The results demonstrate that the optimal solution aimed at maximizing stage efficiency achieves a superior trade-off in aerothermal improvement. Quantitatively, it increases the stage efficiency by 0.41% and decreases the tip and casing heat transfer coefficients by 7.06% and 7.75% respectively, while only slightly increasing the blade heat transfer coefficient. This improvement in aerothermal performance can be attributed to the CG’s ability to control tip leakage flow and regulate the topology of the tip vortex system. Besides, a global sensitivity analysis is employed to identify the key geometric parameters of CG. The starting point of the CG is found to be the most crucial parameter and its influence laws are investigated through a variable-controlling methodology. In summary, the proposed CG configuration and optimization strategy offer a promising solution to diminish tip leakage losses and enhance the thermal performance of turbine rotor tips.
Advancements in Sustainable Aviation Fuels: Impact of Nano-Additives and Ammonia-Based Strategies on Emissions
Authors: Di Gloria Pasquale , De Giorgi Maria Grazia , Strafella Luciano , Ciccarella Giuseppe , Castelluzzo Gregorio Grazio , Baldassarre Francesca , Ficarella Antonio 
Published: August 2024

Abstract
The increasing commitment to sustainable practices has intensified research into innovative methods to diminish the release of harmful pollutants and greenhouse gases, such as CO2, CO, and NOx, into our environment. A promising avenue of exploration lies in the adoption of fuel emulsions enriched with nano-additives aimed at curtailing NOx emissions.
In this context, our study delves into the impact of nano-particulate additives — specifically those based on ammonia and water — on the combustion characteristics of Jet-A1 aviation fuel. Utilizing a 300-kW liquid swirl combustor, we conducted a series of experiments across two global equivalence ratios (Φ = 0.24 and Φ = 0.40). Our investigation encompassed the analysis of laminar flame speed (LFS) and an in-depth examination of flame properties through advanced chemiluminescence imaging and modal analysis techniques.
The primary objective was to unravel the complexities of how these nano-additives modulate flame dynamics and the intricate web of internal chemical reactions, alongside evaluating the broader environmental ramifications resulting from alterations in the combustion process.
The experimental outcomes revealed that the integration of urea and water additives into the fuel matrix distinctly affected LFS, with observed enhancements at the lower global equivalence ratio and detrimental impacts when the ratio was increased. Through modal analysis, we discerned a notable stabilizing influence on the flame’s behavior, which was particularly pronounced at leaner fuel conditions.
From the study of the spray, the addition of water and urea appears to influence combustion chemistry, and more uniform sprays facilitate more complete combustion.
Chemiluminescence imaging further illuminated these effects, demonstrating a higher emission intensity of NH2* radicals compared to NH* radicals, a variance contingent on the global equivalence ratio. Notably, the experimental data indicated a substantial abatement in NOx emissions, predominantly at the lower equivalence ratios. This reduction was accompanied by a marginal uptick in CO2 and CO emissions — a trade-off that warrants consideration.
The Hybrid Pathway to Flexible Power Turbines: Part C, Enabling Live Thermal Boundary Prediction Using Real-Time Plant Measurements and LSTM Neural Networks
Authors: Baker Mark , Rosic Budimir 
Published: August 2024

Abstract
The global drive towards renewable energy is imposing challenging operating requirements on power turbines. Flexible load-leveling applications must accept more frequent and demanding start-stop cycles. Full transient analyses are too computationally expensive for real-time simulation across all operating regimes so monitoring relies on sparse physical measurements. Alone, these sparse data lack the fidelity for real-time prediction of a complex thermal field. A new hybrid methodology is proposed, coupling data across a range of fidelities to bridge the limitations in the individual analyses. Combining several fidelity methods in parallel: low-order models, corrected by real-time physical measurements, are calibrated with high-fidelity simulations. The multi-faceted hybrid approach enables the real-time speed of low-order analysis at high resolution. This paper series develops the critical enabling features of the hybrid method. Real-time definition of the simulation thermal boundary condition is fundamental to the methodology. A novel Long-Short-Term-Memory (LSTM) neural network is presented, enabling time series prediction of the turbine thermal profile. The remote sensing method utilizes standard plant measurements to reconstruct the turbine temperature history, allowing reliable thermal prediction whilst removing the need for direct monitoring of the casing temperature. Calculations within the training region demonstrated high accuracy, achieving a mean square error of 3.1 K and maximum instantaneous peak error of 7.6 K. Combining a reduced feature space and efficient two-step predictor-corrector structure, the LSTM method offers high-speed temperature calculation, successfully predicting one month of operating data in under a minute.
Topology Optimization of Centrifugal Compressor Exhaust Volute With Discrete Adjoint Method
Authors: Zhang Huiying , Wan Siyuan , Jiang Mindi , Xi Xi , Xu Shengli 
Published: August 2024

Abstract
The exhaust volute, an important component of a centrifugal compressor, plays a crucial role in improving overall compressor efficiency. Traditional design methods rely heavily on designer’s experience and often result in low design efficiency. In this study, a topology optimization design method for the exhaust volute flow channel is proposed to address this issue. The optimization objective focuses on minimizing flow energy dissipation within the design domain while considering flow compressibility. The sensitivity of the objective function to design variables is calculated using the discrete adjoint method. In the open-source platform OpenFOAM, the finite volume method is utilized to solve governing equations with darcy source term and adjoint equations, and the Method of Moving Asymptotes (MMA) algorithm is applied to solve the optimization problem. Numerical examples of different volute types in two and three dimensionals are used to demonstrate the effectiveness of the proposed method. The results show that the topology optimization method proposed in the present work can quickly obtain the optimal volute configuration.
Pulsations and Vibrations in the Discharge Piping of a Throttled Supercritical CO2 Turbine
Authors: Wilkes Jason , Patil Abhay , Bygrave Jon 
Published: August 2024

Abstract
Choke nozzles present an economical option to control the expander downstream conditions in high-pressure, high-temperature supercritical CO2 loops; however, the expansion and high fluid momentum exiting the choke may induce instability, causing pulsating behavior and vibration of the loop due to fluid-structure interaction. The current study investigates the performance of a conventional choke design utilizing CFD simulations to provide detailed insight into jet behavior and interaction with the wall. The analysis uses constant boundary conditions and doesn’t account for any flow instability due to fluctuations and swirl velocities at the expander outlet. The CFD outcomes reveal the whirling motion of the jet after exiting the choke sticking to the pipe wall during the initial phase of jet formation. This whirling jet interacts with the downstream pipe and was shown during testing to create large pressure pulsations in the downstream piping. The study concludes with the design, analysis, and testing of a flow conditioner-type choke that redistributes and homogenizes flow downstream of the choke, which reduces the undesirable excitations and consequently eliminates the pipe vibrations.
Fluidic Thrust Vectoring on an Altitude-Adaptive Double-Divergent Nozzle Using a Bypass Passage
Authors: Das Arnab Kumar , Mankodi Tapan K. , Saha Ujjwal K. 
Published: August 2024

Abstract
Shock vector control (SVC) is one of the most researched topics in the field of fluidic thrust vectoring (FTV). In SVC, a secondary fluid flows through an injector to deflect the primary flow through the nozzle. However, the losses associated with the secondary injection is significantly high due to engine bleed. Modern research on SVC focuses on the use of bypass passage in order to mitigate this loss. The present study deals with this so-called bypass-SVC on altitude-adaptive double-divergent nozzles (DDNs), which have two diverging sections separated by an inflection point. The inflection Mach number is set to be 1.5. Three different DDN configurations have been studied in this work by varying the lengths of the diverging sections. The steady-state flow-field has been numerically solved using ANSYS Fluent software over a range of nozzle pressure ratios (NPRs), and results have been compared to a single-divergent nozzle (SDN) of the same nozzle area expansion ratio (ε). The results indicate higher pitch thrust vector angle (δp) for the DDNs as compared to the SDN at certain NPRs. Also, the thrust losses (ω) have been observed to be less for the DDNs as compared to the SDN at higher NPRs. In the non-vectored state, the coefficient of thrust (CF) of the DDNs is comparable with that of the SDN.
On the Relationship Between Swirl and Unsteadiness Within Turbine Rim Seals
Authors: Vella Simon , Tang Hui , Carnevale Mauro , Scobie James A. , Lock Gary D. , Salvatori Francesco , Sangan Carl M. 
Published: August 2024

Abstract
Unravelling the flow physics pertaining to hot gas ingress in turbines is crucial in enabling designers to realise global decarbonisation targets in aerospace. A turbine rim seal is fitted at the periphery of the rotor-stator cavity to minimise the ingress of annulus gas, which detrimentally affects cycle efficiency. The inherent unsteadiness in rim seal flows, arising from shear gradients between contiguous flow paths, introduces a consequential, yet presently unestablished, influence on sealing characteristics.
A single-stage axial turbine facility in conjunction with an aeroengine architecture is employed to assess the steady and unsteady sealing characteristics of a range of industrially-relevant rim seals. Time-averaged measurements of gas concentration and swirl, acquired over a range of flow coefficients (CF), exhibited an inverse relationship between sealing performance and the purge-mainstream swirl difference (Δβ). Spectral analysis of unsteady pressure signals revealed an associated unsteadiness, induced by the strength of the annulus-cavity interaction. Across all CF, a low-frequency harmonic range consistently displayed proportionality between spectral activity and Δβ. Thus, a relationship between steady and unsteady characteristics was established.
Examining a series of rim seal configurations with varying radial clearances signified that sealing performance was predominantly influenced by the radially outermost clearance. The configurations exhibiting superior performance presented heightened spectral activity, ascribed to an increased radial purge mass flux and establishing a definite relationship with concurrent steady measurements.
A Novel Design Concept for Highly Loaded Compressor Airfoils
Authors: Hergt Alexander , Reutter Oliver , Grund Sebastian 
Published: August 2024

Abstract
Compressor blade design has always faced the challenge of meeting the performance requirements of the compressor while keeping losses to a minimum. Over the past decades, a number of different airfoil types have been developed and grouped into methodologies. The best known example of such a methodology is the NACA airfoil systematic, which is still the basis for many pre-design procedures. With the introduction of modern optimization methods and AI approaches, the airfoil design changed to the development of customized blading. In the present study, a novel concept for highly loaded compressor airfoils is developed using the DLR optimization method AutoOpti and the flow solver TRACE. The aim here is to combine customized airfoil design with a new design methodology. The new approach leads to a Load Splitting Airfoil (LSA) methodology. The concept behind this airfoil method is fundamentally presented in this study on the basis of the DLR-LSA cascade. The conventional NACA 65 K48 cascade was used to define the boundary conditions and requirements for the new cascade, since it is highly loaded and provides a wide basis of comparison for the evaluation of the new airfoil concept. The inflow Mach number is 0.67 and a working range of 10 degrees is to be achieved, resulting in an extremely high aerodynamic load. Based on detailed numerical simulations, the concept of load redistribution by passive boundary layer energization is presented and described. This is followed by an experimental validation of the cascade in DLR’s Transonic Cascade Wind Tunnel (TGK). In addition to the details of the boundary layer development, the analysis also includes the evaluation of the classical performance parameters of a compressor cascade. The loss distribution, deflection, and deceleration behavior are determined over the entire operating range. The results of the experimental validation confirm the design and also the function of the load shifting approach. Finally, the performance of the novel compressor airfoil design is evaluated in comparison to the baseline NACA 65.
A Fuzzy-Adaptive ECMS Based Energy Management Strategy for Series Hybrid Electric Aircraft
Authors: Zhai Yaowei , Wang Xiangyang , Zhang Houwu 
Published: August 2024

Abstract
It is critical to develop an energy management strategy (EMS) for hybrid aircraft that can strike a balance between flight safety and fuel economy. This paper proposes an EMS that combines the fuzzy logic control and adaptive-equivalent consumption minimization strategy (A-ECMS), thereby being named Fuzzy-A-ECMS. This strategy is essentially an improvement of A-ECMS. While inheriting the advantages of A-ECMS, it also solves the issue that conventional A-ECMS is not ideal for aviation applications due to its constant battery state of charge (SOC) target value. SOC sustainability is an important criteria for flight safety, and the balanced energy content of the battery is considered to evaluate fuel consumption. The combination of the feedforward control of the required power with the feedback control of the SOC in the Fuzzy-A-ECMS enables it to sustain the SOC effectively. In order to assess the performance improvement of Fuzzy-A-ECMS compared to A-ECMS, two kinds of flight missions — the complete flight mission and the short-term flight missions with stochastic power requirements — are simulated in the MATLAB/Simulink environment. The results demonstrate that the Fuzzy-A-ECMS can accomplish a balance between sustaining SOC and improving fuel economy.
The Effect of Thermal Cycling on Deposition in an Impingement/Effusion Cooling Geometry
Authors: Gogidze George J. , Bons Jeffrey P. , Lundgreen Ryan 
Published: August 2024

Abstract
Experiments were conducted in a high-pressure deposition facility to study the effect of engine cycling on the successive buildup of deposits as aircraft shut down and power up at different intervals. The test facility simulates the pressure and temperature environment of a combustor liner or turbine vane cooling circuit. The coolant flow temperature reaches 894K (1150 °F) and discharges into a 17atm (250 psi) cavity pressure at a nominal pressure ratio of 1.027. AFRL05 test dust with a 0–10μm size distribution is added to the coolant gas stream at a loading that ranged from 80–120mg/m3. The cooling circuit consists of a double-walled impingement cooling plate and effusion cooling plate with nominal hole sizes on the order of 0.5mm in diameter. To simulate the effects of cycling, the facility is brought up to the desired operating conditions where the first batch of dust is delivered (2–8g). The facility is then ramped down to ambient conditions. Following a “dwell” period of approximately 24 hours, another batch of dust is delivered once the facility is brought back up to the desired operating condition again. Test data were acquired for one, two, and four cycles with different dust mass delivered. Values such as discharge coefficient, pressure ratio, Reynolds Number, and temperature are used to evaluate the effects of dust deposition on the impingement/effusion plate setup. Dust capture efficiency and flow blockage time histories are reported. Capture efficiency is shown to be insensitive to cycling whereas flow blockage is negatively impacted by increased number of cycles for the same total mass delivered. The sloughing of deposit structures during the cool down of the cooling circuit is postulated to be responsible for the observed behavior. Implications for engine operation in dust-laden environments are summarized.