bluuebunny/crossref_metadata_2025_split huggingface dataset:
Configuration of Organic Rankine Cycles for Geothermal Applications: An Industrial Perspective
Authors: Pettinari Matteo , Dago Gnandjuet Gaston Brice , Frate Guido Francesco , Baccioli Andrea , Ferrari Lorenzo , Desideri Umberto , Amidei Simone , Cosi Lorenzo 
Published: September 2023

Abstract
Geothermal resources represent a valuable option to reduce fossil fuel-based power production because they feature an unmatched capacity factor among other Renewable Energy Sources (RES). Geothermal resource availability reduces with the temperature. Therefore, developing cost-effective solutions to exploit low-temperature geothermal energy is mandatory to expand technology utilisation. The standard solution for converting low-temperature thermal sources into power is Organic Rankine Cycles (ORC). ORC basic layout (subcritical) is well-known, but the more advanced alternatives, such as transcritical and two-pressure level cycles, are much less widespread, and it is unclear whether the higher efficiency justifies the higher capital cost. The paper focuses on the exploitation with ORC of geothermal resources (hot water) with a temperature lower than 200°C and mass flow rates between 200 and 1400 m3/h for a target power production ranging from 3 to 30 MW. The paper compares three ORC layouts, subcritical, transcritical and two pressure-level, from thermodynamic and economic points of view to map the most cost-effective solutions in the investigated size ranges. The techno-economic comparison considers the impact of the operating conditions and fluid on the machine’s expected performance and the heat exchangers’ size. As expected, more complicated layouts yield higher conversion efficiencies, with the two pressure-level cycles achieving the highest power output for the same geothermal source conditions. However, the economic analysis showed that the most efficient solutions are not always preferable when considering the cost-efficiency trade-off.
Case Study of Compressor Blade Tip Clearance and Implications to Operational Flexibility of an Industrial Gas Turbine
Authors: Bullard Timothy , Paskin Marc , Vogel Greg , Smith Nathaniel 
Published: September 2023

Abstract
The flexibility of a gas turbine power plant is characterized by the ability to quickly start the machine (fast start) and respond to changes in grid demand (fast ramp). A quicker load response is more economically viable and highly desired by plant operators amid growing use of renewable energy sources.
For a gas turbine, a fast start or fast ramp procedure involves many concerns, not the least of which is compressor blade clearances. Blade rubs occur when compressor blade tips contact the engine casing and are a significant driver of wear and potential catastrophic damage to a rotor.
New units are being designed with fast start in mind, building in the necessary blade tip clearance from the factory. For installed fleets of commercially operating industrial gas turbines, blade tip clearance data is not widely available, making it difficult to fully understand feasibility of fast start/ramp. Additionally, only OEMs or those with detailed dimensional data, modelling capabilities and resources would have insight to blade clearance; however, without hard data there is still significant uncertainty.
The present effort is an attempt to measure blade tip clearances of a commercially operating gas turbine with the intention of facilitating fast start and fast ramp. An instrumented test was conducted involving installation of a sensor system to several stages of an industrial gas turbine compressor. The system was integrated to a controller with data link, and operator screen with alarm indications. A test cycle was carried out which varied the rate of starting and ramping. The results indicate a characteristic behaviour of the rotor and thus provide insight to operational flexibility. Finally, a model was developed which serves to provide further prediction for very high ramp rates. Limitations of the study and methodology are also discussed.
Stability of the Co- and Counter-Rotating Swirlers in a Liquid-Fueled Can Combustor
Authors: Kıyıcı Fırat , Topal Ahmet , Hepkaya Ender , Ozogul Hamdullah , Zayim Ahmet Kaan , Kaplan Mustafa , Percin Mustafa 
Published: September 2023

Abstract
This study experimentally investigates the effects of swirler channel orientation on combustion instability. For this purpose, the performance of the co- and counter-rotating radial-radial swirlers is assessed in terms of pressure fluctuations in a liquid-fueled can combustor operated with kerosene fuel. High-frequency pressure transducers are used to obtain pressure fluctuations in the combustor in non-reacting and reacting flow conditions. First, non-reacting experiments are conducted to observe the performance of the swirlers at mass flow rates of 10.5, 12, 14, and 15 g/s. Non-reacting experiments show that Precessing Vortex Core occurs at a Strouhal number of 1.9 and dominates the flow field for both swirlers. In the reacting conditions, the effect of the mass flow rate (10.5, 12, 14, and 15 g/s) at a constant fuel flow rate (0.7 g/s) and the impact of the fuel flow rate (0.7, 0.8, 0.9, and 1.0 g/s) at a constant mass flow rate (15 g/s) are investigated. The peak frequency decreases in the reacting conditions compared to non-reacting cases. In the constant fuel flow rate case, the Precessing Vortex Core is observed in the co-rotating swirler for all air flow rates, but it disappears in the counter-rotating swirler at higher mass flow rates. At the constant mass flow rate cases, combustion instability occurs in the co-rotating swirler, while the counter-rotating swirler operates without any sign of instability. In all reacting cases, the peak frequency amplitude is remarkably higher in the co-rotating swirler.
Development and Validation Under Engine Operation Environment of Addtively Manufactured Hot Turbine Parts
Authors: Lindbäck Martin , Frankolin Karin , Tuneskog Erika , Karlsson Björn , Wang Lieke 
Published: September 2023

Abstract
Additive Manufacturing (AM) has emerged as an innovative manufacturing method in comparison to traditionally subtractive method. Its unparalleled design freedom opened up the applications in gas turbine business where the efficiency improvement is consistently needed. While the AM application in combustion section has gained a lot of experience, the AM application in turbine hot gas path is still limited, e.g., most of the applications like vane 1 and vane 2 are limited to the gas turbines with relatively low operation temperatures. This paper presents the project where vane 1, heat shield 1 (HS1) and vane 2 in SGT-800 were redesigned with only AM enabled in-wall cooling schemes and these parts were tested and validated under the real engine operation environment. Through Design for Additive Manufacturing (DfAM), these parts were redesigned with lower cooling air consumption, reduced average metal temperature and more even temperature distribution. After that, these parts were additively manufactured in EOS M400-4 and post print quality checks were conducted to ensure the part quality. The quality check includes cut-up metallurgical investigation, hot air thermography test and water test, etc. All three AM parts were instrumented with thermo-couples and thermo-crystals, and tested under the full load engine operation condition. The crystal measurement results confirmed the reliability of the design tool as well as the design targets. For AM vane 1, a cooling air saving of more than 20% was achieved and the average metal temperature was reduced by 56 °C from the baseline of the cast vane 1. For AM HS1 and AM vane 2, the cooling air saving is not significant, but the average temperature was reduced by approximately 80 °C. This will result in significant increase in part life time, either to increase the part service interval or use it as basis for cooling air saving. With this validation under the engine environment, the implementation of these three AM parts is planned in the customer engines.
Turbulence Model Influence on Turbopump Inducer Performance
Authors: de Oliveira Igor , Bringhenti Cleverson , Takachi Jesuino , Adalgiza Garcia Maia Ana , Kapat Jayanta , Fernandez Erik 
Published: September 2023

Abstract
The use of inducers in turbopumps for liquid propellant rocket engines allowed operation at high rotational speeds, contributing to global vehicle performance improvement. Methods for designing inducers have been explored using analytical methods, experimental data and numerical solutions. The use of CFD for simulating and designing rocket turbopump inducers is a relevant practice because it can rapidly explore scenarios untested in the experimental endeavors for determining empirical functions. This technique also captures more problem details than reduced order analytical solutions. Turbomachines have a different accuracy in terms of solution prediction for different turbulence models and application. The flow specificity of the turbomachinery changes the adequate turbulence model to obtain a more accurate solution. For this reason, it is of interest to investigate how different turbulence modeling predicts the fluid flow behavior and their accuracy to calculate the inducers’ performance. The present work aims to investigate the capability of different turbulence models on the performance and flowfield obtained via CFD simulations of an inducer pump. The CFD simulations were performed using a commercial software for k-ϵ, RNG k-ϵ and Shear Stress Transport turbulence models. The simulations were performed on a known inducer geometry for which published experimental performance data as a function of operational conditions is available in literature. The present paper discusses the differences in the performance prediction and the flow field calculated for the turbulence models simulated. For the cases studied, the k-ϵ standard model shows better predictions for the efficiency and head coefficient compared with the experimental data demonstrating their accuracy in solving rotational flows.
Innovative Lightweight Compression System Based on Axial-Centrifugal Contra-Rotating Concept: Pushing the Limits
Authors: Kumar Akchhay , Mistry Chetankumar , Kumar Sankar , Pratap Ajay 
Published: September 2023

Abstract
An innovative lightweight compression system presented could push the limits and ramp up the capabilities of modern gas turbines. This system integrates the two established multi-stage compressor architectures. Firstly, the widely prevalent axial-centrifugal compressor is the configuration with several axial compressor stages with a back-end centrifugal impeller. Secondly, the contra-rotating compressor is a stator-less configuration with two sets of counter-rotating rotors. In the present study, this configuration is adopted for a small and compact compressor stage with three rotors. These are two counter-rotating front and rear axial-flow rotors and one back end centrifugal impeller rotating in the same direction as the rear axial-flow rotor. Moreover, two special annular duct arrangements, i.e. inter-stage connecting duct and centrifugal diffuser-duct were configured for aerodynamic matching of the stage and effective diffusion of flow respectively. The challenges of the present problem are manifold which comprises components such as axial-flow compressors, a centrifugal compressor, an inter-stage connecting annular duct, and a curved diffuser-duct along with the concept of contra-rotation. Multiple design innovations were performed to create an overall lightweight and compact compression system. In this work, the design approach to the proposed compressor stage and its components operating at low-speed and low-mass flow is presented. Subsequently, the numerical results performed with Computational fluid dynamics (CFD) analysis to improve the design performance iteratively are discussed. The baseline design of the contra-rotating axial compressor was configured with a higher aerodynamic loading of the front rotor and lower aerodynamic loading of the rear rotor, the rear rotor rotating at a higher design speed than the front rotor and low aspect-ratio blades. The baseline design of the backend centrifugal compressor was configured with diffusing passage shape of the diffuser-duct with a critical hub surface modification producing overall improved flow characteristics.
Rotating System Control Using Hybrid Active Bearings
Authors: Alves Diogo S. , Bailey Nicola , Keogh Patrick 
Published: September 2023

Abstract
Strategies to control rotor dynamic behavior are critical to achieve improved performance of rotating machinery. It is possible to control the dynamics of a rotating system through the bearing characteristics, i.e., changing their damping and stiffness coefficients. Bearings that can be commanded to change their characteristics over time are known as active bearings. Because active bearings have a complex design, their use in commercial machines is limited. In this scenario, journal bearings are still regularly used since they can provide damping and high load carrying capacity. Moreover, by modifying the fluid film thickness or clearance, one can control the dynamic behavior of the bearing, which is not a simple task when a traditional geometric format is used. However, since the fluid film thickness is proportional to the axial position of the shaft in conical bearings, their dynamic characteristics could be manipulated through compensation of the shaft’s axial position via a thrust magnetic bearing. Therefore, this paper proposes an alternative hybrid bearing design, which consists of a conical fluid-film bearing and a thrust magnetic bearing. The magnetic bearing is used to sustain the axial force created and actuate the system. For the system analyzed, the new concept was able to reduce the maximum lateral vibration of the rotor by 30%.
Teaching Optimization of Thermal and Fluid Machinery in the Post-Pandemic Era
Authors: Vouros Stavros , Diamantidou Dimitra-Eirini , Kyprianidis Konstantinos 
Published: September 2023

Abstract
Higher education has been crucially impacted by the pandemic during the past years. Despite the associated challenges, a wide portfolio of digital literacies has been developed for the delegates. This work evaluates the introduction of digital tools into in-person education. The “Process Optimization” course at Mälardalen University is reformed to operate in a digitally enhanced classroom mode. The course covers a variety of optimization methods applied on thermal and fluid machinery such as systems of compressors, pumps and heat exchangers, heat and power plants, aircraft trajectories and propulsion systems. The constructive alignment is presented to illustrate links between learning objectives, learning activities, and assessment tasks. A series of digital tools is introduced to elevate learning experience prior, during, and after class time. Those comprise digital quizzes, a video channel, polls, a digital whiteboard, and a digital forum. The course is systematically instrumented, yielding a vast set of statistics for evaluating the effectiveness of digital tools as well as engagement levels for learners. The contribution of digitalization into standardizing the formative and summative assessment is discussed. It is observed that digital tools complement the participation into pre- and post-classroom activities. An interactive and digitalized course evaluation activity is also designed. This allowed learners and educators to productively exchange feedback in an inclusive manner. The accrued data provides insight into the impact of digitalization on the delivery of an applied engineering course. Lessons learnt comprise quantitative and qualitative outcomes arising from the perspectives of both learners and teachers. Guidelines and recommended practices are provided for the penetration of digital tools into synchronous and asynchronous learning activities. This paper identifies opportunities as well as space for improvement arising from the penetration of digital tools into the new era for education.
Ignition of a Safran’s Helicopter Engine With a Compact Nanosecond Laser System
Authors: Maillard Martin , Amiard Hudebine Gabriel , Orain Mikaël , Doublet Pierre , Beaure D'augères Patrick , Berat Claude , Viguier Christophe , Douillard Stéphane , Freysz Eric 
Published: September 2023

Abstract
We report on the ignition of a Safran’s helicopter engine using a compact laser system. The laser system delivers nanosecond infrared pulses at a high repetition rate which energy can be up to 40 mJ. The first tests were run on a Safran Helicopter Engines experimental bench operating at room temperature and ambient pressure with jet A-1 fuel. We studied in detail the impact of the laser pulse energy and the spark position on the engine ignition domain. An optical focusing system fixed on the engine casing enables to focus the laser pulse at different positions in the combustion chamber. The focused laser beam generates a plasma in the combustion chamber, which ignites the engine. Our experimental data show that the laser spark position impacts the pulse energy required to ignite the engine. At the optimal position, we very reliably ignite the engine with a pulse energy of only 3 mJ. To understand this behavior, similar experiments were run on the MERCATO experimental bench at ONERA (the French aerospace lab). This bench faithfully reproduces the geometry and the flow field of the Safran engine’s combustion chamber. Using a Mie scattering imaging technique, we studied the kerosene spray generated by the start injector. Our data indicates that depending on the laser spark position in the combustion chamber, the kerosene droplets scatter more or less the laser light. This impacts the pulse energy and its spot size at the focal point and influences the laser ignition probability. In addition, ignition success requires a minimum density of kerosene droplets. Hence, the optimal laser spark position is a compromise between the droplet density at the focal point and the laser beam scattering induced by droplets before reaching that position.
Optimum Coupling of Thermal Energy Storage and Power Cycles
Authors: Guccione Salvatore , Trevisan Silvia , Guedez Rafael 
Published: September 2023

Abstract
The present work proposes a methodology that enables decision-making in selecting the adequate power cycle and Thermal Energy Storage (TES) type for a wide range of operating temperatures between 380 and 1200 °C. A broad spectrum of power block configurations has been explored including steam Rankine, gas turbine, supercritical CO2, (sCO2) combined gas turbine with Rankine, and combined gas turbine with sCO2. The study also evaluated molten salt, particle, and air packed bed TES to identify the most cost-effective power cycle and TES combination. A techno-economic optimization has been conducted aimed at minimizing the Levelized Cost of Storage (LCOS) for different plant capacities and charging costs. Results show that coupling of a sCO2 power block with recompression and intercooling with a particle TES is the most cost-effective solution for a 100 MWe plant with 12 hours of storage and a charging cost of 50 EUR/MWh. This achieved an LCOS value of 154.7 EUR/MWh at 750 °C with a 200 °C temperature difference. Particle-based energy storage is the most cost-effective option for a wide range of temperature combinations, while an intercooled sCO2 power block with an air-packed bed TES should be preferred when electricity is free, and storage represents a significant portion of the capital cost. Molten salt TES is the optimal choice provided that the design temperatures align with the limitations of the salts.
Trailing Edge Erosion Prevention in Steam Turbine Last Stage Rotating Blades
Authors: Sürken Norbert , Hofbauer Alexander , Pfaller Dirk 
Published: September 2023

Abstract
In recent years, the operational requirements for steam turbines used for heat and/or power applications have changed significantly. Especially, highly flexible operation regimes and extended operating ranges are required including frequently requested start-stop cycles and “parking” of units at low load conditions. Here, low load operation potentially comes with a set of availability relevant aspects for the low-pressure steam turbine’s last stage rotating blade row such as pronounced blade vibrations at windage or trailing edge erosion.
Unlike the well-understood leading-edge erosion of last stage rotating blades in steam turbines, trailing edge erosion is a phenomenon which in the past was nearly exclusively known from steam turbines for district heating power plants and some industrial applications. With the intensified flexible operation of power plants, however, trailing edge erosion is more likely to be observed also for non-extraction units.
It is assumed that trailing edge erosion occurs during windage operation, when the flow through the last stage is low enough such that the recirculation vortex in the exhaust area transports moisture back towards the trailing edge of the last stage rotating blade. The subsequent water impingement eventually may cause material degradation [1] at a mechanically loaded area of the blade’s foil above the root plate. Sources of moisture can be, e.g., inherent steam wetness or water injection systems.
To enable an estimation of trailing edge erosion susceptibility for certain applications and load conditions, an evaluation scheme is proposed in the present paper. Its objective is to indicate and detect the built-up of trailing edge erosion early enough to enable a timely and pre-emptive condition-based service intervention and/or to advise a change in operation mode, as applicable.
The developed evaluation scheme is subsequently implemented into a Combined Heat and Power Plant featuring an extraction machine. The resulting inspection results substantiate the potential trailing edge erosion prevention capability of the developed scheme.
Effect of Coolant Flowrate on High-Pressure Turbine Tip Flow Structures and Thermal Loading
Authors: Christensen Louis , Celestina Richard , Sperling Spencer , Mathison Randall , Aksoy Hakan , Liu Jong , Nickol Jeremy 
Published: September 2023

Abstract
Film cooling is essential to operation of modern gas turbine blades, which can operate at temperatures exceeding the working limits of the materials they are made of. The tips of turbine blades are an area of keen interest where there can be high thermal loading from tip leakage flows, and, in the case of squealer tips, it can be difficult to effectively cool these areas. The naïve approach to reducing thermal loading is to increase the amount of coolant supplied to the blade. This approach is intuitive however the increased level of coolant issued from the blade affects flow structures around the blade altering how the heat transfer is occurring and ultimately affecting the thermal loading. This work studies a contemporary cooled high-pressure gas turbine tip with a squealer rim at various coolant flowrates. Conjugate heat transfer simulations informed from short duration turbine tests operating at scaled engine conditions are used to investigate the effect of coolant flowrate on the turbine blade tip flow field and thermal loading.
Variation of the coolant flowrate does not cause macroscale changes to the flow structures, as the introduction of film cooling does, but rather these variations make small yet significant changes to the interactions between the vortex structures and coolant jets that can be beneficial or detrimental to the thermal loading on the blade tips. Additionally, not all regions of the blade tip are impacted by changes to the coolant flowrate; different areas of the blade can reach a coolant saturation level where further addition of coolant is ineffective. Results from this work present a more complete picture of the complex effects film cooling has on turbine blade tip flows. Knowledge of the unintuitive and sometimes paradoxical effects of cooling can be used to further optimize film cooling schemes.