bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Literature Review of NOx Emissions in Current and Future State-of-the-Art Gas Turbines
Authors: Dennis Richard , Long Henry A. , Jesionowski Gary 
Published: September 2023

Abstract
Current U.S. government policy seeks to achieve a completely carbon-free economy by 2050, with a carbon-free electricity sector by 2035 (per executive orders #14008 and #14057). To address these goals, the U.S. Department of Energy is evaluating strategies and technologies that support the production, utilization, transport, and storage of hydrogen (via initiatives such as DOE’s Energy Earthshot – Hydrogen and various DOE funding opportunity announcements). A carbon-free fuel such as hydrogen cannot be overvalued in a dynamic electric energy sector seeking to decarbonize. One of the most important technologies needed to achieve the goal of a carbon-free electricity sector is a 100% hydrogen-fueled gas turbine. Accommodating hydrogen-based fuels has been a key goal for various original engine manufacturers (OEMs) for many years, but much more research and development (R&D) is needed. The purpose of this paper is to highlight the current state-of-the-art of hydrogen turbine technology, especially regarding nitrogen oxide (NOx) emissions compared to natural gas-fueled turbines. NOx is the primary criteria pollutant from thermally-driven combustion turbines and should be controlled to levels that are equivalent to or below existing standards (as reported “existing standards” for hydrogen-fueled gas turbines may need to be re-baselined). This paper will provide an overview of hydrogen as a fuel and various NOx emissions control techniques that are relevant for hydrogen-based fuels. A conclusion from this overview is that, with some level of R&D, NOx emissions from hydrogen-fueled gas turbines can be controlled to levels similar to those produced by state-of-the-art natural gas-fueled combustion turbines while remaining competitive in terms of performance and efficiency.
Numerical Investigation of Flow Characteristics in a Supercritical Carbon Dioxide Turbine for 20 Megawatt Brayton Cycle
Authors: Yang Guoying , Yang Rui , Deng Qinghua , Xu Bozhou , Li Jun , Feng Zhenping 
Published: September 2023

Abstract
Efficient and clean utilization of energy has become one of the themes of sustainable development. The closed Brayton cycle with supercritical carbon dioxide (SCO2) as working fluid has the advantages of compact structure, high efficiency and environmental friendliness, so it is widely concerned by scholars around the world. As the carrier of thermal power conversion in cycle system, the aerodynamic performance of CO2 turbines affects the cycle efficiency crucially. However, the research work about this topic is still relatively rare in open literature. In this paper, the flow characteristics and aerodynamic performance of a SCO2 axial-flow turbine are investigated by numerical method, and the enthalpy drop for each stage is optimized. The differences of flow characteristics under design conditions before and after optimization are compared. Finally, the off-design flow characteristics of the turbine are analyzed. The results show that compared with that before optimization, the total-to-total efficiency is increased by 0.79%, and the flow rate is increased by 4.30%. The leakage of clapboard seal and blade tip seal in the first stage is also significantly reduced. The leakage rate of the clapboard seal in the first stage reaches 3.13% of the total flow rate. The total-to-total efficiency of the turbine also decreases by 4.04% compared with that without seal clearance. In this paper, the flow characteristics of the main passage and the seal clearance of a SCO2 turbine are deeply analyzed. The reasons for the large leakage are revealed, and the relevant factors that have a negative impact on its efficiency are summarized. The research results can provide reference for the design of SCO2 axial flow turbines.
Sequential Performance Adaptation for a Turboprop Engine Model at Flight Condition
Authors: Kim Sangjo , Kwon Young-Min , Chun Youngju , Lee Chung-Ryeol , Yang Wonseck , Kim Youil 
Published: September 2023

Abstract
A performance adaptation method is proposed for a turboprop engine, to improve the prediction accuracy of an engine model based on measurement data on flight conditions. The corrected mass flow rate and efficiency of a high-pressure compressor (HPC) and the efficiency of a power turbine (PT) are adjusted by using adaptation factors to match the engine model and the measurements. Moreover, the calculated HPC exit pressure and high-pressure turbine (HPT) exit temperature from the engine model are adjusted by using additional adaptation factors. Shaft power from low-pressure (LP) spool, HPC exit pressure, HPT exit temperature, PT exit temperature, fuel mass flow rate, high-pressure shaft rotating speed, and LP shaft rotating speed are all measured at ten operating points. The proposed performance adaptation method is divided into several steps and proceeded sequentially. In the first step, the adaptation factors for adjusting component performance maps are calculated and generated empirical correlations. Then, the additional adaptation factors are calculated for adjusting the calculated HPC exit pressure and HPT exit temperature based on the revised engine model from the previous stage and the measurement data. Finally, the empirical correlations are applied to the original engine model and the prediction accuracy is compared to the measurement data. As a result, it is confirmed that the revised engine model reduced the error with the measured data in flight conditions, compared to the original engine model.
Radial Interference Fit and Centrifugal Force Effects on Lateral Rotordynamic Response
Authors: Kim Baik Jin , Oh Joseph , Palazzolo Alan 
Published: September 2023

Abstract
Interference fits or shrink fits are widely utilized in highspeed rotating machinery to secure impellers, bladed disks and couplings with high torque and thrust loadings. Shaft-disc locking assemblies (SDLA) are utilized to secure wheels on a shaft, via radially directed interference fits, in contrast butt joint, Hirth, and Curvic couplings have interface contacts in the axial direction. A conventional practice is to treat interference fits as continuous connections in rotordynamic shaft models. However, this may introduce significant inaccuracies by neglect of the local interface flexibilities at interference fits. A novel modeling approach incorporating 3D solid finite elements with a GW interface model at radial contact surfaces is presented. The approach is validated by benchmarking it with measured free-free natural mode and critical speed measurements. The test rig shaft has wheels attached by SDLAs, an industrial tilt pad bearing and a radial/deep groove ball bearing. Critical speeds are obtained from synchronous vibration measurements using relative shaft, eddy current sensors, attached to the bearing housing. The critical speeds are shown to be influenced by stress stiffening of the shaft resulting from centrifugal forces that increase circumferential (hoop) stress.
Optimization of a Fan-Shaped Film-Cooling Jet and Its Implementation in a High-Pressure Turbine Vane With Large-Eddy Simulations
Authors: Vincze Balazs , Agarwal Shubham , Odier Nicolas , Gicquel Laurent , Duchaine Florent 
Published: September 2023

Abstract
Film cooling technique is extensively used in turbine engines to protect the turbine components from the hot gases exiting the combustion chamber. With this approach, cold fluid effusing from holes along the surface of the turbine creates a protective film to prevent the ruin of the solid material composing the blade. As of today it is now known that the hole geometry is a key element which determines the thermal efficiency of film cooling. Their designs for optimal holes operating at conditions of high-pressure turbines are however a challenge for which several research groups and industrial companies have devoted intensive numerical and experimental campaigns. In this study, a Large-Eddy Simulation based approach is adopted to optimize the shape of a fan-shaped hole on an academic flat plate configuration in engine representative conditions. To do so, four of the most important geometrical parameters defining such a cooling hole shape, namely the depth of the expanded section, the hole inclination angle and the forward as well as the lateral expansion angles are selected as design variables to obtain an optimal hole shape. The Bayesian based Efficient Global Optimization method along with the Expected Improvement as the acquisition function are used to find the maximum surface averaged film cooling effectiveness as the objective function. After several database enrichment steps to reduce the overall model error, an optimal shape with the highest cooling performance for a given operating condition is obtained. The resulting hole geometry is then installed on an experimental high-pressure film-cooled turbine vane investigated in the TATEF2 European project for validation and assessment. In that case, Large-Eddy Simulations on a reduced span of the vane are conducted to compare the efficiencies of the original and optimized hole geometries. It is first shown that the simulation of the original geometry reproduces accurately the flow field around the vane and thermal efficiency. Then, the results illustrate the difficulties of integrating an optimal geometry obtained on a flat plate without group effects on a real geometry.
A Numerical Design Space Investigation of Low-Speed Axial Compressor Stages Using Single-Row and Tandem Bladings
Authors: von Jeinsen Philipp , Eckel Jannik , Giannini Samuele , Gümmer Volker 
Published: September 2023

Abstract
The present paper numerically investigates the design space of an axial, low-speed compressor stage using tandem- and single aerofoil configurations. The investigated rotor and stator designs follow a coupled throughflow and blade-to-blade design approach and will yield quasi-3D designed compressor stages with either single-rotor single-stator or tandem-rotor tandemstator configurations. In past studies, tandem aerofoil configurations have shown a potential for increasing stage working coefficients, while maintaining their efficiency compared to their single aerofoil reference configuration. However, it was also shown that tandem configurations are able to reduce efficiency due to an increase of secondary flow caused by the higher loading and introduction in the a second aerofoil. Currently, there is no clear design guideline on when tandem aerofoil configurations should be preferred over single ones, and under which circumstances they should be avoided. To answer this question, the present paper will attempt to create a “Smith-chart” for tandem aerofoil stages and compare them to their single aerofoil counterparts. Originally intended for use with turbine stages, the Smith-chart maps out the potential efficiencies of turbomachinery designs. It plots the working coefficient (Ψ) over the throughflow coefficient (φ), which gives a direct indication of the shape of velocity triangles in the stage. Whereas the Smith-chart has been well investigated for single aerofoil stages, both numerically and experimentally, as well as for low and high-speed applications, this is not the case so far for tandem configurations. The current work presents a fast Q3D design and analysis procedure, used on a low-speed axial compressor stage and will yield quasi-3D efficiencies for a large number of different design coefficients. The findings of this work will enable future research to identify preferred combinations of design coefficients for tandem aerofoil configurations, which can then be further analyzed in 3D investigations at a higher fidelity level.
Insights Into the Flow Field and Performance of a Boundary Layer Pump
Authors: Palaveev Kyril , Rajendran David John , Anselmi Eduardo , Santhanakrishnan Mani , Pachidis Vassilios 
Published: September 2023

Abstract
A flow field analysis of a realistic, integrated, multi-disc boundary layer pump as is necessary for investigating the reasons for typically quoted low efficiencies in such pumps is described. The study focuses on the 3D RANS solutions of a water boundary layer pump model created to replicate a design by Morris, 1973, which consists of 170 discs and a volute channel. A baseline study is performed to investigate the rotor-only performance after which a volute alone is separately simulated to identify the performance and losses in each as separate systems. Thereafter, an integrated model is characterized across mass flow rates and rotational speeds. The flow fields of all three models are discussed and the results of the integrated model are compared to the experimental data.
The results from the model with the rotor only confirm the typically made claim that the efficiency of the rotor in a boundary layer pump possesses relatively high values which in this case is 87% at the design point, reinforcing results from previous studies that the rotor assembly is not the cause of inefficiency. The volute on its own indicated a hydraulic efficiency of around 97%. However, the integrated model yielded a rotor efficiency of around 74% and an overall pump efficiency of 51% at the design point, clearly outlining the fact that the effect of the volute integrated with the rotor is the reason for both the rotor and pump efficiency degradataion. The reason for this drop in efficiency is discussed in detail by highlighting the change in the flow topologies. The insights into the flow field and the identification of the reason for inefficiencies using a separated component analysis approach provides directions for avenues in which design improvements would need to be attempted.
Acoustoelastic Modes in a Rotor-Cavity System With Superposed Through Flow
Authors: Unglaube Tina , Brillert Dieter 
Published: September 2023

Abstract
When increasing the pressure ratio in centrifugal compressors, understanding the fluid-structure interaction between the impeller and the surrounding fluid becomes increasingly important. It is crucial to know how critical frequencies shift when operating conditions vary. Therefore, this paper investigates acoustoelastic modes in a rotor-stator cavity, which serves as a simplified model of the side chambers of radial compressors for fundamental research purposes.
New experimental results gathered at the rotor-stator cavity test rig at the Chair of Turbomachinery at University Duisburg Essen (Germany) are presented. The measurements include such with a rotating disk and superimposed centrifugal and centripetal through flow. The mass flow of the superimposed through flow is varied, and results are compared to cases without added through flow. Results for structure dominant modes do not vary subject to a change in superposed mass flow, but acoustic dominant ones do. This agrees with the understanding that the flow structure in the cavity influences acoustic dominant modes but does not have a considerable effect on the structure dominant modes originating from the rotating disk. However, results for acoustic dominant modes do not show a consistent trend. While a centrifugal through flow appears to decrease the core rotation inside the cavity, results for centripetal through flow show a rather mixed picture. Also, measured acoustic dominant modes seem to be of mixed order, impeding the evaluation of possible coupling effects. Here, future research is expected to bring clarity. Ultimately, more evidence has been found that measured frequency shifts can be considered a summation of the frequency shifts due to a change in fluid properties and disk rotational speed, plus an additional frequency shift due to the superimposed through flow. This is an important contribution to a better understanding of acoustoelastic modes in rotor-stator cavities and efforts to avoid machine failure in highly loaded centrifugal compressors.
Investigation of the Applicability of Methods Approved for Steam to the Design of Labyrinth Seals in Turbines Operated With CO2 in Supercritical State
Authors: Tegethoff Katharina , Musch Christian , Glos Stefan , Schuster Sebastian , Brillert Dieter 
Published: September 2023

Abstract
This paper presents an approach for testing and adapting numerical models for the design and design optimisation of turbines operating with CO2 in supercritical condition (sCO2). Particular emphasis is put on the influence of the medium and its specific thermodynamic properties on the design process of labyrinth seals. In contrast to the medium steam, no comprehensive empirical values of power plants are available for CO2 in a supercritical state in the field of turbomachinery design. Therefore, the question arises whether the design rules established for steam turbines can also be used for the design of a sCO2 turbine and how any necessary adaptations for the medium CO2 can be introduced. This paper aims to contribute to answering this question by first identifying the labyrinth seal as one component in whose vicinity relevant effects, such as leakage and windage heating, as well as influences on the rotor dynamics are to be expected. The investigations carried out are based on mathematical modelling and computational fluid dynamics (CFD) calculations. Established methods and models are used, which are validated in a next step for the special requirements of the application in a sCO2 turbine and adapted if necessary. It can be shown that the properties of the fluid have an influence on the design of the components. A consideration of the material-specific properties as well as the thermodynamic state variables is therefore required. This is exemplified by the fact that the density of CO2 is about twice as high as that of the medium steam in classic steam turbine applications. The results presented have the potential to enable a turbine manufacturer to assess the confidence interval of known methods when applied to the particular challenges of sCO2 turbine design.
Feasibility of the Use of Thermal History Paints for Long Term Exposure of Low Temperature Life Critical Components
Authors: Araguas Rodriguez Silvia , Peral Jiménez David , Pilgrim Christopher C. , Scheibel John , Feist Jörg P. 
Published: September 2023

Abstract
Thermal History Paint (THP) is a new technique used to measure temperature in the harsh operating conditions inside gas turbines or other machinery. It is applied to the surface of a test component and upon heating, changes permanently according to the maximum temperature of exposure. After operation, the THP is read-out at many locations across the surface. Through calibration, the measurements are translated to temperature to deliver high-resolution thermal maps.
The technique has been recently demonstrated in short-term development tests for the validation of thermal models in the design phase. It has been shown that the THP has several advantages compared to traditional temperature measurement techniques. In comparison to thermocouples and thermal crystals the paint can acquire measurements at many locations without the challenging installation limitations. THP has been shown to have greater durability than thermochromic paints and can be applied to measure the temperature non-destructively.
The increased durability opens the possibility that the THP could be applied to an operational component and operated through its lifetime and measured at maintenance intervals to monitor the maximum temperature of the component. This would improve run, repair and replace decisions, reducing life cycle costs. For example, rotor discs in industrial gas turbines are critical components that are expensive and time-consuming to replace and experience creep when exposed to excessive temperatures.
This paper provides the first investigation into the behaviour of the THP for extended operational exposures, with rotor discs as an example application. The objective was to understand whether the THP could be used for temperature measurements after such long exposures and, if so, how it would be calibrated. The results show that the THP exhibits good durability, enabling measurements up to 450°C after 7200 hours of exposure, covering the useful range for rotor disc applications. In addition, the behaviour of the THP allows the effect of time to be neglected for such long exposures, simplifying the calibration procedure and enabling practical use in this application. The results indicate the viability of this new technique to capture temperature information that is not currently possible to acquire.
Experimental Investigation of Transient Flow Phenomena in Rotating Compressor Cavities
Authors: Pernak Mikolaj J. , Nicholas Tom E. W. , Williams Jake T. , Jackson Richard W. , Tang Hui , Lock Gary D. , Scobie James A. 
Published: September 2023

Abstract
The clearance of compressor blade tips during aero-engine accelerations is an important design issue for next-generation engine architectures. The transient clearance depends on the radial expansion of the compressor discs, which is directly coupled to conjugate heat transfer in co-rotating discs governed by unsteady and unstable buoyancy-induced flow. This paper discusses an experimental and modelling study using the Bath Compressor Cavity Rig, which simulates a generic axial compressor at fluid-dynamically scaled conditions. The rig was specifically designed to generate heat transfer of practical interest to the engine designer and validate computational codes. This work presents the first study of the fundamental fluid dynamic and heat transfer phenomena under transient conditions. The rotating flow structure was seen to be characterised by coherent pairs of cyclonic/anti-cyclonic vortex pairs; the strength, rotational frequency, stability and number of these unsteady structures changed with changing rotational Reynolds and Grashof numbers during the transients. These structures, measured by unsteady pressure transducers in the rotating frame of reference, were only present when the flow in the rotating cavity was dominated by buoyancy. Experimental correlations of both Nusselt number and radial mass flow rate in the rotating core were correlated against Grashof number. Remarkably, the experiments revealed a consistent correlation for both steady-state and transient conditions over a wide range of Gr. The results have a practical application to thermo-mechanical models for engine design.