bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Blade Damage on Low Pressure Ratio Fan Windmill Aerodynamics
Authors: Medina Cassillas Sofía I. , Castillo Pardo Alejandro , Hall Cesare A. , Mohankumar Benjamin 
Published: August 2024

Abstract
Fan windmill occurs when power to a turbofan is cut during flight and the airflow through the engine causes the fan to freewheel, often following fan damage. The fan rotational speed and drag during windmill determine the loads transmitted to the airframe, and these depend on the fan damage sustained. Idealised patterns of axisymmetric and non-axisymmetric damage have been studied using high-resolution measurements in a flow field representative of a low pressure ratio fan in combination with steady RANS simulations to understand the impact on the windmill flow field. Axisymmetric tip damage decreases the windmill rotational speed by 61% when 25% of the blade span is removed due to a shift in the zero-work radius. The reduced blade span creates an intense tip vortex and redistributes the flow, increasing the axial velocity above the damaged tip. For non-axisymmetric damage, there is still work output at the blade tip, such that removing 25% of half the blades with varying damage pitch-to-chord reduces the fan rotational speed by 9–13% compared to undamaged windmill. Phase-averaged hot-wire measurements show that this additional rotor work is due to radial flow redistribution combined with turning of the flow in the passages above the damaged blades.
Probabilistic Analysis of Leading Edge Erosion Behavior of a High-Pressure Compressor in a Turbofan Engine
Authors: Türke Andreas , Schlüter Lukas , Voigt Matthias , Schmidt Robin , Vogel Andreas , Mailach Ronald 
Published: August 2024

Abstract
The demands for competitiveness, performance, and sustainability in civil aviation become more and more challenging and therefore an increase in the efficiency of aero engines is required. A potential starting point for optimization to reach these goals is the compressor. The influence of the compressor blade leading edges on the overall aerodynamic behavior and performance deterioration due to erosion are well-known topics. However, the effect of erosion on leading edge geometry still needs to be studied. Therefore, a Monte Carlo simulation based analysis of leading edge erosion, caused by ingestion of naturally occurring dust during operation, is presented. The influence of blade geometry, operating point, and particle configuration on erosive wear is investigated by the example of a 10.5-stage high-pressure compressor of a modern civil turbofan engine. By incorporating a one-way coupled Euler-Lagrangian approach, trajectories of solid particles through the compressor have been calculated. To replicate naturally occurring mineral dust and volcanic ash, different particle configurations have been studied, varying particle size, density, and drag behavior. Geometric effects have been taken into account by varying blade geometry based on a comprehensive database of optically measured ex-service blades. The blade geometry is characterized utilizing a parametric model capable of describing leading edge variability. By applying an erosion model the resulting geometry of artificially eroded compressor blades is derived. The results indicate that the change of geometry caused by erosive wear shows a characteristic behavior. This erosion characteristic is mostly independent of the operating point and blade geometry considered. Abrasive effects mainly influence the area close to the blade tip, increase asymmetry, and change the curvature of the leading edge. These results are consistent with the analysis of optically measured ex-service blades.
Multi-Disciplinary Surrogate-Based Optimization of a Compressor Rotor Blade Considering Ice Impact
Authors: Nyssen Florence , de Cazenove Jean , Nigro Rémy , Cracco Cédric , Baert Lieven , Ruess Jean-Sébastien , Valentin Vincent 
Published: August 2024

Abstract
Ice ingestion can lead to a range of detrimental effects, from diminished engine performance to potentially catastrophic failure, especially for the first compressor stages. As the ice is traveling through the engine, whether due to direct hail particle ingestion or due to shedding of ice accretions, the impact with engine components that rotate at high speed can result in severe mechanical damage. The leading edge of the blades in the low-pressure compressor are particularly prone to local damage. Therefore, it is important to consider ice impact simulations as soon as possible in the design process. In this context, the authors propose in this work a multi-disciplinary surrogate-based optimization strategy for a compressor rotor that includes ice impact simulations. For this purpose, a dedicated 3D blade parametrization is first introduced. Then, based on this set of design parameters, the proposed optimization chain is presented and each chain block is detailed. In particular, (1) aerodynamical simulations are considered at three different flight conditions, (2) maximum static stresses and frequency margins with respect to specific engine orders are evaluated, (3) the blade robustness to blade/casing contact events is assessed using the clearance consumption simplified criteria, and (4) ice impact simulations are carried out using transient response computations with an explicit time integration scheme and the ice fragment modeled with the Smooth Particle Hydrodynamics (SPH) method. A dedicated lower-fidelity model has been developed for the specific purpose of optimization loops to maintain reasonable computations times. The proposed strategy is applied to design a rotor blade of a low-pressure compressor. The aim is to satisfy all mechanical constraints to ensure the blade robustness in operation, without deteriorating its aerodynamic performance. The optimization process is detailed in the paper, and an in-depth analysis of the optimization results is presented.
Operation of a Fully Integrated Rotating Detonation Combustor in a T63 Gas Turbine Engine
Authors: Fievisohn Robert T. , Battelle Ryan , Karimi Miad , Klingshirn Christopher 
Published: August 2024

Abstract
The Air Force Research Laboratory (AFRL) has designed a rotating detonation combustor (RDC) as a replacement for the main burner in a T63 gas turbine engine. Unlike the stock combustor, this RDC operates on gaseous hydrogen. Previous AFRL efforts developed a similar RDC but in an open loop configuration. In that configuration, the air and cooling flows were fed from separate external sources and the compressor discharge was diverted and used to estimate compressor work. The focus of that project was to determine the impact of unsteadiness from an RDC on turbine efficiency. Results from the previous project showed that there was minimal impact to turbine efficiency when the detonation outflow was mixed with the cooling flows in a mixer/ejector configuration. The current work is a follow-on effort to design an RDC that operates in a closed loop configuration. Operation and cooling of the RDC is done with the compressor discharge with no external support. The main challenges associated with this effort are designing an RDC that has sufficient performance to close the engine cycle, the ability to work over the entire operating map, and thermal steady state operation. In this work, an RDC is developed that can operate continuously from startup to normal rated power. Results from a 6-minute test are presented where the combustor operates in a deflagrative mode at startup and transitions to detonative combustion as air and fuel flow rates are increased. The combustor was constructed of 304 stainless steel and suffered minor oxidative damage. Results from this work will be applied to a combustor made of Inconel 625 for a future test that is fully integrated in a T63 gas turbine engine.
Experimental Investigation of Rotor Passage Loss in S-CO2 Radial Turbine
Authors: Lee Seungkyu , Lee Jeong Ik , Kim Gihyeon , Baek Jeong Yeol 
Published: August 2024

Abstract
This paper presents an experimental investigation of rotor passage loss in an S-CO2 radial turbine. It addresses the need to adapt existing design methodologies for S-CO2 turbomachinery due to its distinct physical behavior compared to ideal gas turbomachinery. This study involves selecting and calibrating existing rotor passage loss models, crucial for determining the pressure ratio and efficiency of a radial turbine. An S-CO2 Turbine-Alternator-Compressor (TAC) in KAIST is utilized for empirical measurements, leading to the calibration of existing Balje’s rotor passage loss model. The paper highlights the uniqueness of S-CO2 turbomachinery and contributes to the understanding and improvement of their design and operation.
Centrifugal Compressor Surge in Closed Loop Systems: Initial Modelling and Comparison With Experiments
Authors: Purushothaman Sreenath , Reggio Federico , Traverso Alberto , Niccolini Marmont Du Haut Champ Carlo Alberto , Silvestri Paolo , Halbe Chaitanya 
Published: August 2024

Abstract
Heat pumps are expected to play a primary role in electrification of thermal users in the residential and industrial sectors. Dynamic compressors are widely used in large size heat pumps, thanks to their industrial replicability, compact size, affordable costs, and good performance in terms of efficiency and low acoustic emissions. The instability, which may occur in a compressor installed in closed loop cycle such as in a heat pump, is quite different from the classic open loop configuration involving dynamic compressors. This is mainly due to the complexity of the compressor instability mechanism coupled to a vapor compression system connected with two-phase heat exchangers, having different thermal and fluid dynamic capacitance properties, under a physical feedback loop.
The aim of this paper is to investigate the behavior of a dynamic compressor installed in an innovative heat pump prototype, of laboratory scale, under stable and unstable conditions. A preliminary simple dynamic model of the compression system consisting of a radial compressor, condenser and evaporator, is developed to represent the heat pump compression system, aiming at its time-dependent representation during compressor instable behavior. The evaporator and condenser are modelled using empirical correlations representing the heat exchange and phase change phenomena and including the thermal capacitances due to refrigerant mass and heat exchanger pipes. The preliminary validation of the dynamic model results is done through a dedicated experimental campaign, under different operating conditions. Results show the complexity of the interaction between the centrifugal compressor and the heat pump loop, discerning the different contributions to the time-dependent response of the system. Future steps will encompass a more detailed modelling of the heat pump loop and the use of updated field measurements, including liquid level meters in the heat exchangers.
Optimization of Smooth Straight-Through Labyrinth Seal Based on XGBoost and Improved GA
Authors: Hao Liu , Guoqing Li 
Published: August 2024

Abstract
Improving the sealing performance of labyrinth seal is beneficial in reducing the loss of downstream components as well as improving the aero-engines’ efficiency. Meanwhile, the optimization of labyrinth seal is more cost-effective than optimizing other components of aero-engines. Based on extreme gradient boosting (XGBoost) and improved genetic algorithm (GA), an automatic optimizer for smooth straight-through labyrinth seal is proposed. According to the ordering of feature importance, the 10 selected geometric parameters of smooth straight-through labyrinth seals with two gaps (0.1 mm, 0.25 mm) are optimized when the axial length of labyrinth seal is limited. The optimization results show that the leakage rate of the optimized labyrinth seal with two gaps is 19.67% and 23.80% lower than the reference labyrinth seal, respectively. It is found that the decrease of fin height, fin angle, fillet radius, and fin width, and the increase of fin pitch are beneficial to improve the sealing performance of smooth straight-through labyrinth seal. The analysis of flow field reveals the reasons for the improvement of sealing performance due to the change of geometric parameters. However, it must be noted that the optimization effect decreases as the pressure ratio increases, primarily as the result of the increase in carry-over coefficient. This work provides a new approach to optimize smooth straight-through labyrinth seal.
Influence of the Terminal Position of the Rotatable Ring of Controllable Speed Casing on the Flow Stability of a High-Load Compressor Stage
Authors: Zhong Jingjun , Hu Yi , Ao Zhao , Wu Wanyang 
Published: August 2024

Abstract
Controllable Speed Casing (CSC) is an innovative casing treatment technology designed to enhance the flow stability of compressors. This technology improves the compressor stage’s flow stability by exerting an additional circumferential force through a rotating ring on the rotor tip region flow. This paper investigates the effect of varying the terminal position of the rotating ring on the stability expansion capability of the CSC, with its initial position fixed at the rotor tip leading edge. The findings indicate that when the rotatable ring’s terminal position is set before the position where the tip leakage vortex begins to break down, the CSC primarily boosts compressor flow stability by suppressing the development of the tip leakage vortex and controlling the tip leakage flow. However, if the rotatable ring’s terminal position is set after the position where the tip leakage vortex begins to break down, the circumferential additional force range exerted by the CSC expands, further diminishing the original driving force of the tip leakage flow. This also causes the leakage vortex to undergo circumferential deflection, distancing it from the adjacent blade pressure surface, thereby enhancing the flow capacity of the compressor stage. As the terminal position of the rotatable ring moves continuously towards the rotor tip trailing edge, the stability expansion capability of the CSC is progressively improved. When the terminal position of the rotatable ring reaches the rotor trailing edge position, the CSC can increase the stable operating margin of the compressor stage by a maximum of 45.11%.
Enhancing Gas Turbine Component Life Predictions Using Fleet Data and Probabilistic Methods
Authors: Kapitzke Kristopher , Maxted Joshua , Meyer Christopher , Moffat Andrew 
Published: August 2024

Abstract
Flexible operation of Industrial Gas Turbines is becoming more commonplace as a solution to reduce life cycle cost and increase sustainability. OEMs are developing digital twin technology to understand the effect of this variable operation on component life. This technology can also be used to accurately forecast turbine operation to a potential future maintenance period or end of service interval. The consideration of available fleet machine data is required to manage the risk and enable these future predictions of damage in life-limiting components.
Probabilistic methods, utilizing Monte-Carlo approaches, can be leveraged to model physically realistic operation, material variation, and uncertainties in important parameters such as metal stress and temperature. A key technology in leveraging Probabilistic methods is the ability to translate engine operation parameters into component stress and temperature variables using Reduced Order Models (ROMs). This in conjunction with damage models, representing mechanisms such as creep, fatigue, oxidation, and corrosion, provides the mathematical structure necessary to produce many hundreds of thousands of potential damage results within a reasonable computation time.
This paper aims to outline techniques to characterize a subset of fleet data to provide fleet models of operation. The integration of these fleet models into Probabilistic frameworks and how they are used to manage data driven upper bound damage predictions where operational data is not available will also be discussed.
Impact-Enhanced Resonant Vibration Absorber for Turbomachinery Blisks
Authors: Cimpuieru Mihai , Kripfgans Alexander D. , Kelly Sean T. , Epureanu Bogdan I. 
Published: August 2024

Abstract
The study of blisks is essential to the development of safe and efficient turbomachines. Blisks are geometrically complex structures exposed to high temperatures and pressures that operate at high rotational speeds, and thus are susceptible to fatigue. Therefore, reducing vibration amplitudes in blisks is paramount to avoid failure of these systems. This paper extends previous studies of blisk dampers based on tuned vibration absorbers by analyzing the effects of including energy dissipation through impacts. In this work, the absorber has a ring architecture that also allows impacts. A finite element model of an as-manufactured blisk with 22 blades is used throughout the analysis, and the damper is tuned for experimental operating conditions. Impacts are modeled microscopically, using a novel impact-contact characterization. Results show that impacts significantly enhance the blade response reduction through energy dissipation. Furthermore, impacts slightly increase shift resonant frequencies and are effective for specific combinations of contact surface geometry and material properties.
Experimental Study of Natural Gas and Hydrogen Co-Firing Characteristics Using Different Types of Single Nozzles of F-Class Practical Gas Turbine Combustors
Authors: Lee Sanghyup , Park Jungkeuk , Park Seik , Choi Nakjeong , Shin Jugon 
Published: August 2024

Abstract
Recently, research through the co-firing of natural gas and hydrogen, a carbon-free clean fuel, is attracting attention because to reduce greenhouse gas emissions from aging gas turbine power generation is one of the key energy issues. This can enhance the capability of old gas turbines and contribute stably to an increase in the proportion of combined cycle power plant utilization following the gradual shutdown of coal-fired power plants in Korea. The purpose of this study is to find the optimal operating conditions of mixed fuels without hardware modification of the F-class gas turbine combustor. The experiment was performed according to the load and the co-firing rate using four different types of fuel nozzles (F-Class DLN combustors), and the flame characteristics according to the change in conditions could be analyzed. Under this study, co-firing test was performed with natural gas and hydrogen. The test conditions were selected based on actual machine operating conditions from 30% to 100% thermal load and the hydrogen co-fired with natural gas up to 70% at each load. OH high-speed imaging and an OH-PLIF technique were used to analyze the flame structure, and flame characteristics of co-fired flame in detail. In addition, dynamic pressure was measured to check the combustion instability and exhaust gas emissions were measured to evaluate combustion characteristics of co-fired flame. Major findings are critical co-firing rates of each nozzle based on NOx emission level and combustion dynamics. As the hydrogen co-firing rate increased, the flame length decreased compared to natural gas combustion, and it was confirmed that NOx increased rapidly with the co-firing rate over about 30%vol. In addition, the measured dynamic pressure oscillation results for each nozzle did not show significant variations compared to natural gas combustion. Through this study, it was possible to derive the characteristic operation map of a single nozzle according to the hydrogen co-firing rate.
Feasibility Study of Decentralized Lubrication System Design Through Branch and Bound and Genetic Algorithm for Turbomachinery Trains
Authors: Chen Yuzheng , Maier Bill , Buckenberger Andy , Zhao Yaoyao Fiona 
Published: August 2024

Abstract
The lubrication system functions are crucial in a mechanical system, where friction needs to be controlled and managed. These functions include preventing excessive wear and tear, minimizing heat generation, and prolonging the machinery components’ lifespan. Improper lubrication can incur substantial costs in repairing damaged or replacing worn-out parts and unscheduled downtime. Although turbomachinery trains centralized circulating lubrication systems developed over half a century ago are reliable, they now require an updated design philosophy. These systems are challenged by issues such as low efficiency, complex piping networks, additional footprint space, and high costs.
To address these issues, this study explores improvement methods employed in similar centralized industrial systems, like those in the energy and wastewater sectors. A common design trait of these systems is decentralization, transforming a large-scale centralized infrastructure into decentralized, smaller, localized units. These units can leverage local resources and distribute them according to specific requirements. Decentralization has demonstrated improvements in resilience, reliability, efficiency, cost-effectiveness, and environmental impact. Given the comparable challenges faced by centralized circulating lubrication systems, the feasibility of applying decentralization to lubrication systems was investigated.
This paper introduces the concept of the decentralized lubrication system comprising multiple compact lubrication units that collectively satisfy the turbomachinery train lubrication demand. To identify the optimal decentralized combination of lubrication units, two optimization models using Branch-and-Bound and Genetic Algorithm techniques were developed. The objective of these models was to minimize three key parameters, namely footprint space, tank volume, and investment cost, while adequately meeting the overall lubrication demand (in terms of flow rate). The comparison between the optimized decentralized lubrication system and the existing centralized lubrication system revealed that the former offers significant improvements in the three key parameters. Furthermore, these optimization models demonstrated their adaptability by effectively identifying the optimal combinations of lubrication units for various lubrication demands.