bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Study on the Optimization of the Sensor Arrangement for Blade Tip Timing Measurement
Authors: Tian Jie , Zhang Zhiwei , Chai Pengfei , Wang Shang , Chen Yong , Ouyang Hua 
Published: October 2022

Abstract
As a means of non-contact measurement of blade vibrations, blade tip timing (BTT) has good application prospects for blade design verification and health monitoring. In BTT, the sensor arrangement directly determines the effectiveness of the extracted signal and ultimately affects the quality of the identified vibration parameters. In previous research on optimizing sensor arrangements, the position of each sensor is often selected from among multiple uniformly distributed virtual positions, which limits the optimization space. Moreover, to verify the performance of a sensor arrangement, a high-precision experimental calibration platform is required. However, it is often difficult for the precision to meet the requirements for a benchmark due to an inability to measure the actual blade vibrations. This paper optimized the sensor arrangement by simultaneously considering the mutual coherence and the approximate distance between sensing matrices for an equiangular tight frame in arbitrary-angle compressive sensing method. To avoid the uncertainty in blade displacement conversion in traditional calibration, such as with strain gauges, a laser displacement sensor connected to a slip ring was used to measure directly the displacement of the blade due to vibration. Besides, a macro-fiber composite was used to apply an excitation with a precise frequency to the blade at different speeds to make the blade vibrate synchronously or asynchronously. Then the performance of sensor arrangements optimized by the proposed method as well as other methods, such as mutual coherence, were verified on the self-developed BTT experimental calibration platform. The experimental results show that the signals identified with the optimized sensor arrangements are in good agreement with measurements made by the laser displacement sensor. The amplitude accuracy was more than 76.5% and 91.3% for synchronous and asynchronous vibrations, respectively. Moreover, the identification results were stable after data from 1 or 2 random sensors were removed. This shows the method has good reconstruction accuracy and sensor redundancy.
Predictive Modelling of Local Film-Cooling Flow on a Turbine Rotor Blade
Authors: DeShong Eric T. , Berdanier Reid A. , Thole Karen A. 
Published: October 2022

Abstract
In the turbine section of a modern gas turbine engine, components exposed to the main gas path flow rely on cooling air to maintain hardware durability targets. Therefore, monitoring turbine cooling flow is essential to the diagnostic and prognostic efficacy of a condition-based operation and maintenance (CBOM) approach. This study supports CBOM goals by leveraging supervised machine learning to estimate relative changes to local film-cooling flow rate using surface temperature measured on the pressure side of a rotating turbine blade operating at engine-relevant aerothermal conditions. Throughout the lifetime of a film-cooled turbine component, characteristics of the film-cooling flow — such as film trajectory and cooling effectiveness — vary as degradation-driven geometry distortions occur, which ultimately affects the relationship between the model input and the model output – film-cooling flow rate predictions. The present study addresses this complication by testing a data-driven model on multiple turbine blades of the same nominal design, but with each blade exhibiting different localized film-cooling flow characteristics. By testing the model in this manner, strategies for mitigating the detrimental effects of film-cooling flow characteristic variations on model performance were investigated, and the corresponding flow rate prediction accuracy was quantified.
Effects of Internal Coolant Crossflow on Film-Cooling Performance of Double-Jet and Cylindrical Holes
Authors: Zhu Huaitao , Xie Gongnan , Zhu Rui , Sunden Bengt 
Published: October 2022

Abstract
In this paper, the effects of internal coolant crossflow on double-jet holes were simulated and compared with two rows of cylindrical holes under three blowing ratios (M = 0.5, 1.0, and 1.5), with an established and validated turbulence model. The results show that double-jet holes can provide better film cooling performance for the three different blowing ratios compared with cylindrical holes. As the blowing ratio increases, the superiority of double-jet holes becomes more obvious. The introduction of crossflow can significantly enlarge the coolant coverage area of cylindrical holes, and increase the laterally-averaged film cooling effectiveness. For double-jet holes, the internal coolant crossflow also increases the laterally averaged film cooling effectiveness, but the improvement is limited. For the −45° compound angle film hole of double-jet holes, the internal coolant crossflow decreases the normal velocity (momentum), and makes the coolant to attach on the plate. However, for the other hole, the influence is opposite, the normal velocity (momentum) is increased and the coolant is detached from the plate.
Application of 3D Inverse Design Method on a Transonic Compressor Stage
Authors: Zhang Luying , Ray Saurya Ranjan , Zangeneh Mehrdad 
Published: October 2022

Abstract
In this paper, a three-dimensional viscous inverse design method is presented. The blade geometry is parameterized by aerodynamic variables such as blade loading, which allows direct control of the aerodynamic flow field. With a specified stacking axis and thickness distribution, the algorithm solves the flow field and blade geometry iteratively until the prescribed blade loading is matched. Meanwhile, the fast turn-around time of the inverse design method enables a substantial reduction of time and computational resources, which is particularly advantageous when the product development period is limited. The method is demonstrated through the redesign of an axial transonic compressor (Darmstadt Transonic Compressor), which has been extensively studied by experimental research and numerical simulations. The interaction between the shock wave, the tip clearance flow, and the boundary layer flow in the tip region is crucial for the compressor performance and operational stability. The redesigned compressor reduces the shock strength and the induced flow loss in the tip region through blade loading control. The performance improvement is verified by computational fluid dynamics (CFD) simulations for a stage configuration. A detailed flow field is obtained and compared to the baseline design. The loss reduction mechanism is analyzed by using entropy production rate to better understand the design impact.
Numerical Simulation of Multi-Scale Oil Films on a Rotating Cup Using VOF and Coupled Eulerian Thin-Film-DPM Approaches
Authors: Nicoli A. , Singh K. , Jefferson-Loveday R. , Ambrose S. , Mouvanal S. 
Published: October 2022

Abstract
In this study, the newly developed Nottingham Gas Turbine and Transmission Research Centre (G2TRC) Bearing Chamber Test Module is presented and investigated computationally. The module houses a rotating cup and shaft configuration in order to simulate the droplet generation processes from an aeroengine bearing. The objective of this paper is to model the thin film that develops over the rotating cup surface, comparing a high-fidelity Volume of Fluid (VOF) approach against the Eulerian Thin-Film Model (ETFM). Whilst a VOF approach has previously demonstrated good accuracy for modelling of films over a rotating surface, the ETFM can provide a comparable solution at a much-reduced computational cost. Simulations are performed over a range of shaft speeds and oil flow rates to represent engine operating conditions. This study presents the very first simulation of an oil film over a rotating cup geometry, with a shaft running through the centre of the cup. Computationally, a VOF periodic sector is compared to ETFM simulations run on an equivalent 30° periodic domain. At planes before the rotating cup edge, both film thicknesses and axial velocities are compared. The high-fidelity VOF simulations demonstrate that with an increase in rotational speed, the film thickness over the rotating cup reduces; whilst an increase in oil flow rate produces a thicker film. Compared to the high-fidelity VOF simulations, the ETFM provides good agreement in terms of both film thickness and axial velocities. Overall, the ETFM is shown to be able to produce a similar film to the VOF approach at a much-reduced computational cost, offering a numerical speed-up of approximately 200 to 300 times.
Axial Ventilation and Blade Row Effects on Transient Natural Convective Shutdown Cooling in a Gas Turbine
Authors: Fahy Daniel D. , Ireland Peter 
Published: October 2022

Abstract
As a large civil gas turbine is cooling following operation, natural convective flows cause components to cool asymmetrically — the bottom sector cools faster than the top sector. This can lead to a number of issues that have the potential to damage engine components and affect operability. The ability to predict and understand this transient cooling cycle of a gas turbine has proven to be extremely difficult, owing to the complex nature of natural convective flow physics and its dependency on a considerable number of design parameters.
An experimental and numerical investigation into the impact of axial ventilation (interaction between the annulus and the external air) and blade rows on the natural convective flow field in a large civil gas turbine high-pressure compressor has led to some key discoveries. Axial ventilation caused a 70% increase in the peak top-to-bottom temperature difference in the cooling cycle, when compared to the baseline sealed case. The combinations of four blade rows and axial ventilation caused a 130% increase in peak temperature difference over the baseline case. Numerical simulations illuminated that the root cause of this was the cold air drawn into the lower section of the annulus led to a relatively high heat flux, coupled with a blockage effect on the natural draft in the upper section of the annulus inhibiting the convective heat transfer from this section. There appears to be a relationship between the porosity of the annulus and the peak top-to-bottom temperature difference that was observed.
This study on the impact of two parameters on the shutdown cooling of a simplified gas turbine annulus has highlighted their importance and inter-dependency in defining the level of rotor bow that is observed. Therefore, it is imperative that these effects are included and sufficiently captured in order for a shutdown cooling prediction method to be accurate.
Development of a Transient Test Facility for Evaluating the Aerothermodynamic Performance of Gas Turbine Cascades
Authors: Bai Bo , Li Yuanyuan , Li Zhigang , Li Jun 
Published: October 2022

Abstract
The paper presents the detailed design and benchmarking measurements for a transient linear cascade test facility with a bypass line. The test facility includes an experiment measurements line, a linear test section cascade, a bypass line and an exhaust line, and the quasi-steady-state aerodynamic and transient thermodynamic measurements can be conducted in this test facility. The linear cascade holds up 6 equally spaced cascade profiles, forming 5 completed cascade passages, and the center passage is used for aerodynamic and thermodynamic experiment measurements. Up to 2.4 kg/s of air is continuously supplied by four compressors, thus the quasi-steady-state aerodynamic test can be conducted. For a transient thermodynamic test, the mainstream is heated by a 150 kW heater and discharged to the atmosphere through a bypass line. After reaching the steady state, the bypass flow can be turned to enter the test line within 1.5 s by a control system. A significant step change of mainstream temperature is achieved in this way. A wide range of geometries and flow conditions investigations can be performed in this test facility, due to the special design of the pitch adjustment section and rotatable platform. An optical access window installed on the turntable can provide instrumentation access for Infrared (IR) measurements, laser-based measurements and visualization measurements. The benchmarking measurements at various exit Mach number (Ma) and incidence angles (β), are used to verify the aerodynamic and thermodynamic measurements performance of this transient test facility. Results show that the desired aerodynamic behaviors and a significantly transient step change (less than 1 s) of mainstream temperature are observed during the benchmark test duration. The long-time quasi-steady-state aerodynamic and transient thermodynamic measurements can be reliably conducted in this transient test facility.
Aeroelastic Analysis of Large-Scale Wind Turbines With Biplane Rotors
Authors: Pichitkul Auraluck , Sankar Lakshmi 
Published: October 2022

Abstract
As modern wind turbines continuously grow in scale and capacity, rotor blade mass and cost have become major design drivers. For offshore windfarms where construction, maintenance, and service are particularly challenging, blade mass and cost concerns are even more critical. A biplane rotor design concept, proposed by Wirz et al. at the University of California Los Angeles, is explored in this study as a means of reducing blade mass and cost. The biplane design replaces the thick airfoil shapes commonly found in the root region of conventional rotors with two thinner airfoils arranged in a biplane configuration. In the present study, this biplane design concept is applied to a redesign of the NREL 5 MW rotor, representative of modern large-scale offshore wind turbines. It is observed that the performance of the proposed biplane configuration is comparable to the baseline NREL 5 MW design at rated wind speeds, with potential mass-savings. However, the structural analyses also indicate significant stress concentration at the junctions where the biplane configuration is connected to the monoplane regions. A more detailed structural design would be necessary to alleviate stress concentrations in these areas and improve the overall structural characteristics of the rotor.
Predicting NOx Emissions In Gas Turbines Using Finite Rate Approach
Authors: Patwardhan Saurabh , Nakod Pravin , Orsino Stefano , Yadav Rakesh , Xu Fang , Brandt Dustin 
Published: October 2022

Abstract
Emission standard agencies are coming up with more stringent regulations on Nitrogen Oxides (NOx), given their adverse effect on the environment. The aircraft engines operate at varying operating conditions and temperature-dependent emissions like NOx are significantly affected by varying conditions. Computational Fluid Dynamics (CFD) simulations are playing a key role in the design of gas turbine combustors and an accurate NOx model will be an important tool for the designers. The new stringent regulations will require new computational approaches over the traditional methods so that the NOx can be predicted accurately under a wide range of operating conditions.
Traditionally, the high temperature NOx is predicted using a three-step Zeldovich mechanism. However, it has been observed that the NO (Nitrogen oxide) mass fraction predicted by the Zeldovich mechanism is not accurate for low power conditions due to its predominantly high-temperature kinetics. A significant amount of NO2 (Nitrogen dioxide) is observed in the experimental data at lower temperatures. This requires the inclusion of NO2 chemistry in the NOx mechanism. With the increase in the available computational power, a detailed chemistry simulation is gaining attention, especially for pollutant prediction. In this work, we explore the finite rate (FR) chemistry approach for the prediction of total NOx (NO + NO2) in a gas turbine combustor designed for Aerospace applications. Two reduced mechanisms are investigated namely, the PERK mechanism with 31 species and the Hychem mechanism with 71 species. Simulations with both mechanisms show good comparison with the experimental data and predict the individual contribution of NO and NO2 reasonably well. Further, it is observed that the spray breakup model has a significant impact on the NOx prediction, and it is important to capture the fuel spray correctly to predict the right amount of NOx.
Impacts of Pin Fin Shape and Spacing on Heat Transfer and Pressure Losses
Authors: Corbett Thomas M. , Thole Karen A. , Bollapragada Sudhakar 
Published: October 2022

Abstract
Additive manufacturing (AM) provides designers with the freedom to implement many designs that previously would have been costly or difficult to traditionally manufacture. This experimental study leverages this freedom and evaluates several different pin shapes integrated into pin fin arrays of a variety of spacings. Test coupons were manufactured out of Hastelloy-X using direct metal laser sintering (DMLS) and manufacturer recommended process parameters. After manufacturing, internal surface roughness and as-built accuracy were quantified using Computed Tomography (CT) scans. Results indicated that pin fins were all moderately undersized, and that there was significant surface roughness on all interior surfaces. Experimental data indicated that diamond shaped pins were found to have the highest heat transfer of the tested shapes, but triangle shaped pins pointed into the flow incurred the smallest pressure drop. Modifications to the streamwise spacing of the pins had little impact on the friction factor, but did increase heat transfer with increasing pin density. Prior Nusselt number correlations found in literature underestimated heat transfer and pressure loss relative to what was measured resulting from the AM roughness. A new correlation was developed accounting for AM roughness on pin fin arrays.
Numerical Performance Study of Adsorption Based Hydrogen Storage System in Silica Aerogel
Authors: Riahi Adil , Algurab Sara , Otto Marcel , Fernandez Erik , Kapat Jayanta , Schmitt Joshua , Saxena Swati 
Published: October 2022

Abstract
The purpose of this paper is to investigate the thermodynamics of the adsorption/desorption processes of hydrogen on silica aerogel. Hydrogen is a promising alternative fuel for gas turbines as it is carbon free and an excellent energy storage medium. However, the storage of hydrogen itself presents some challenges when stored in liquid or gaseous states. Thus, storing hydrogen in its adsorbed state provides a potential pathway to large scale economic hydrogen storage. The adsorption process is based on weak Van Der Waals forces that make the adsorbate (hydrogen) stick to the adsorbent surface (Silica Aerogel). A 2D CFD model was elaborated to examine the temperature and pressure changes along the adsorption/desorption processes. A grid independence analysis was conducted on meshes ranging from 5000 to 100000 nodes resulted in a similarity of thermodynamic properties after 80000 nodes. The Dubinin-Astakhov (D-A) model was adopted to determine the change in the quantity adsorbed with changing Temperature and pressures. The D-A model declared promising results when implemented in various adsorption studies. The simulation revealed an exothermic and endothermic processes during the adsorption and desorption respectively. A change in temperature during the storage/ discharge of (ΔT = 95K) provides an estimate of the amount of heat to be removed or added during the adsorption and desorption processes. The choice of silica aerogel resides on its feature of being among the lightest materials existing on earth which makes our system suitable for hydrogen storage in transportation. Furthermore, it is largely available and affordable. The outcome of this research can be extrapolated to several gas/silica aerogel combinations’ comparisons. This will be the focus of the upcoming research studies. Additionally, small storage units could provide healthcare applications with breathing air or oxygen packs, diving, space, and aircraft life support would also benefit from this storage technology which endows the system with a portability trait.
Effect of Inlet Preswirl on the Film Cooling Characteristics of Turbine Vane Surface
Authors: Chen Xinnan , Li Zhigang , Li Jun , Xu Qingzong , Du Qiang 
Published: October 2022

Abstract
Conjugate heat transfer (CHT) analyses were conducted to validate the accuracy of numerical method in the prediction of aerodynamic and thermal performance of the film cooled C3X vane. The effect of inlet preswirl on the film cooling performance of the vane surface was investigated, while the Nu and the net heat flux reduction (NHFR) were also calculated to analyze the heat transfer characteristics. In particular, the effects of clocking positions and swirl orientations of the inlet preswirl with varied mass flow ratios of film coolant were studied individually. The results indicate that the inlet preswirl aligned to the vane leading edge (LE) would significantly enhance the heat transfer on the vane surface while the inlet preswirl aligned to the passage would weaken the heat transfer but lead to a nonuniform distribution of Nu. The inlet preswirl aligned to the LE would also seriously affect the flow structure of the showerhead film coolant and do deteriorate to the film cooling performance on the vane surface especially for the suction surface, in contrast, the inlet preswirl aligned to the passage would even improve the film cooling performance under some mass flow rates of film coolant. Moreover, the disadvantage of inlet preswirl to the downstream film cooling performance is almost negligible, while the inlet preswirl is even beneficial to the film coolant coverage under some mass flow rates of coolant in this paper, especially for the suction surface (SS) with a large mass flow rate and the pressure surface (PS) with a small mass flow rate.
Next Generation APS Porous TBC for Gas Turbine Combustors
Authors: Rudrapatna Nagaraja , Lutz Bradley , Kington Harry 
Published: October 2022

Abstract
Modern gas turbine combustors rely on thermal barrier coatings (TBC) in addition to sophisticated cooling strategies to survive high temperature environments. The need for lower emissions either driven by International Civil Aviation Organization (ICAO) regulations or by customers desire for green engines often necessitates increased air budget for improved mixing, thus resulting in less available cooling flow. Even with state-of-the-art cooling schemes to offset reduced cooling air allocation, combustors can benefit from better TBC performance to mitigate durability challenges. This paper showcases the next generation Air Plasma Spray (APS) porous TBC developed by Honeywell as well as discusses tests performed and results gathered to assess its suitability for combustor application. A configured test specimen was utilized to evaluate suitability of new coating system for combustor application. The configured specimen captures the material system, geometric features, manufacturing, and assembly process associated with combustor fabrication and thus provides a realistic environment for performance assessment. The configured specimen test results indicate the new APS porous TBC showed better performance than the standard 6–8% Yttria Stabilized Zirconia (YSZ) porous TBC. The new TBC with its lower conductivity at higher temperature, increased thickness capability, and superior stability at substantially higher temperature than 6–8% YSZ TBC enables hot section components to survive hotter engine cycles.