bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analytical Leakage Model Development for Labyrinth Seals With Honeycomb Structure: Validation and Design of Experiments
Authors: Ertuğral Gürkan , Öksüz Özhan 
Published: August 2024

Abstract
Honeycomb structures are commonly used for many years in land and air turbomachinery applications to enhance the sealing effectiveness of labyrinth seals. Leakage control is the primary asset for honeycomb seals and directly impacts system-level efficiency; thus, estimating the correct leakage flow rate is crucial for the gas turbine engine performance. Leakage predictions are reliable for smooth land configurations using empirical correlations from available literature, however, accurate predictions are considerably challenging in the presence of honeycomb structures.
This paper aims to develop a robust analytical model to estimate accurate leakage mass flow rate by identifying the parameters influencing the flow discharge behavior of honeycomb seals. Reynolds-Averaged Navier-Stokes (RANS) based numerical simulations were performed to investigate flow phenomenon inside the labyrinth seals and honeycomb structures. Experimental test results of Stocker and Collins are the basis of numerical simulations for validation and design of experiments studies. Design of experiments studies were conducted to derive flow coefficients by changing operating conditions and geometric parameters of honeycomb and labyrinth seals. In the available literature, there are limited efforts taken to investigate the flow dynamic behavior of alternative and deteriorated honeycomb structures. For this reason, deteriorated honeycomb structures were investigated for radial displacement, rub groove events, and alternative liner geometries (slanted, square, triangle, circle) were examined and discussed in addition to the conventional honeycomb structures.
The proposed analytical model shows good agreement with the test results and has an extensive application range with reliable leakage prediction accuracy for straight-through labyrinth seals with honeycomb structures. The current model serves as a guideline for secondary air system design engineers and helps in the progress of honeycomb seal design in addition to analytical leakage models.
Review of the Impact of Hydrogen-Containing Fuels on Gas Turbine Hot-Section Materials
Authors: O’Connor Jacqueline , Noble David R. , Bridges Alexander , Shingledecker John , Scheibel John , Gagliano Michael 
Published: August 2024

Abstract
In an effort to achieve worldwide decarbonization goals, a range of low-carbon fuels is being proposed for use in power-generation gas turbines. Two promising fuels are hydrogen and ammonia, which do not produce any CO2 upon combustion. While the use cases of these fuels differ, each has the potential to reduce the carbon intensity of power generation as compared to the current use of natural gas and fuel oil. Many studies have considered the impact that these fuels will have on combustion stability and emissions, as well as other practical considerations like balance of plant. However, potential challenges for the material systems in these engines, particularly high-temperature metal alloys and coatings, have not been sufficiently considered in preparation for the introduction of these fuels. The goal of this paper is to provide a review of the potential material issues associated with implementation of these hydrogen-containing fuels, with a focus on materials in the hot section of existing power-generation gas turbines. To date, relatively little research has considered these material issues at realistic gas turbine conditions, resulting in a need for new research. This paper provides a review of the literature, first-order analyses of the magnitude of potential issues, and avenues for research to facilitate the safe and reliable introduction of these fuels in power-generation gas turbines.
Investigation of Hot Streak Migrations in a Triple Dual-Stage Swirler Combustor Coupled With Turbine Vanes Under Different Contraction Ratios
Authors: Lyu Jiacheng , Hu Keqi , Zhu Zhixin , Wang Gaofeng 
Published: August 2024

Abstract
With the rapid development of modern gas turbines and aeronautical engines, temperature at the combustor outlet is consistently increasing, leading to an intensified interaction between combustor and turbine. Meanwhile, the turbulence, residual swirl, and presence of hot streak at the combustor outlet exert a considerable influence on the downstream turbine, notably affecting blade aerodynamics and heat transfer dynamics.
Nowadays, significant research efforts have been focused on the coupled system of combustor and turbine, aiming to elucidate the flow dynamics and migration patterns of hot streak under complex interactions. This study presents a setup comprising a three-sector combustor and six turbine guide vanes (TGVs) equipped with advanced lean-burn dual-stage swirlers. Temperature distribution at the combustor outlet in the coupled system is measured through a high-temperature dual-axis displacement system. Numerical simulations are conducted to reveal the initiation and progression of hot streak within the combustor, operating within the coupled system. Moreover, the study investigates the impact of various contraction ratios on the mixing characteristics of gas and coolant within the combustor, as well as the migration process of hot streak in turbine guide vanes in the coupled system.
Overall, numerical results indicate that the influence zone of the TGVs on the pressure within the combustor can reach the position of the dilution holes, significantly affecting both the depth and mixing characteristics of the jet from the dilution holes. As the contraction ratio increases, there is an observed increase in the outlet temperature distribution factor (OTDF) within the combustor, which is attributed to reduced mixing effects. Conversely, at the TGVs’ outlet, an increased flow velocity and improved mixing effects in the TGVs’ flow channel contribute to a more uniform temperature field. Furthermore, the clocking position of TGVs in this study is found to impede the mixing of coolant in various flow channels. This highlights the significance of establishing a correlation between TGVs’ clocking position and the inlet hot streak.
Effect of Thermal Barrier Coating Simulation Method on Cooling Characteristics of Turbine Vanes
Authors: Du Zequn , You Ruquan , Li Haiwang , Huang Yi 
Published: August 2024

Abstract
Thermal barrier coating (TBC) is widely used in turbine vanes relying on the good thermal resistance, corrosion resistance. It is of great significance to accurately simulate the flow and heat transfer characteristics of coated vanes. However, there is no uniform standard for the simulation method of TBC. In this paper, the numerical study of vanes with a single-layer coating was conducted. The effect of the simulation methods (real model, called Method-1, and virtual thin-wall, called Method-2) on the flow and heat transfer characteristics was investigated under different TBC properties and turbulence intensity (Tu). The results showed the mass flow of film cooling on the suction surface of real TBC vanes was reduced by 25.5 %, when the TBC thickness was 0.3 mm. The TBC temperature differences between the two simulation methods on the overall and section surfaces were 5.4 K and 25.4 K. The TBC temperature was more sensitive to coating simulation methods. Modifying the property, the change of TBC temperature was the smallest at the leading edge, about 6.5 K. While the change of metal temperature was the largest there, about 37 K. The larger the thermal conductivity, the larger the metal temperature difference and the smaller the TBC temperature difference, which were caused by simulation methods. The sensitivity of temperature to Tu was relatively low for Method-1. As Tu increased, the absolute value of temperature difference on the section between simulation methods decreased first and then increased, and it decreased gradually on the overall surface. Finally, a simplified simulation method (Method-3) was proposed, in which the metal surface was thickened outwards with the virtual thermal conduction resistance added at the interfaces. And the accuracy of this method on the heat transfer characteristics of vanes with a double-layer coating was verified. For all turbulence intensity, the differences of coolant mass flow and temperature between Method-1 and Method-3 were less than 0.15 % and 2 K, respectively.
Assessment of Additive Manufactured Micro-Channel Characteristics: Impact of Hydraulic Diameter Evaluation
Authors: Bacci Tommaso , Picchi Alessio , Castelli Niccolò , Facchini Bruno , Morante Francesco , Innocenti Luca 
Published: August 2024

Abstract
Among internal cooling techniques for gas turbines components, skin cooling is recognized as one of the most promising, especially thanks to the spread of additive manufacturing techniques. In this regard, several studies have tried to characterize heat transfer and pressure loss performance of additive manufactured micro-channels, as well as the impact of AM characteristic parameters, mainly in the form of building angle, and resulting surface roughness and channel shape. The open literature offers several correlations in terms of friction and heat transfer coefficient using a representative hydraulic diameter. Despite that, little attention is given on the importance of such characteristic length definition which may lead to under/over estimation of the cooling rates when correlations are used in the design.
In this work, coupons featuring circular micro-channels with diameters of 0.5 and 1 mm and different building angles have been tested, to retrieve pressure losses and an average heat transfer coefficient through a lumped approach. The coupons were additive manufactured using the Laser Powder Bed Fusion (L-PBF) technique. Exploiting the experimental survey, the impact of the considered hydraulic diameter was investigated, by comparing different approaches based on a direct measurement. An additional and new approach, aimed at the identification of an “effective” diameter, based on fluid-dynamic considerations, was also considered.
The data correlation and the comparison with available correlations from different authors showed the newly proposed approach to provide superior scaling capabilities and, in turn, allowing for the development of more accurate prediction methods.
Investigation on the Interaction of Tip Leakage Flow/ Shock Wave/ Boundary Layer in a Transonic Compressor Stage
Authors: Ma Jianci , Li Jiabin , Ji Lucheng 
Published: August 2024

Abstract
The performance of transonic compressor blades is significantly influenced by the interaction among blade tip leakage flow, shockwaves, and boundary layers at their tips. In this study, a numerical investigation was conducted on a transonic compressor stage with and without shrouded rotor blades. Key factors affecting rotor tip performance were identified, including tip leakage flow/shock wave interaction and shock wave/boundary layer interaction. Observations also indicated that tip leakage flow played a mitigating role in reducing flow separation. Based on these findings, a design approach involving part-shrouded rotor blades was proposed. The optimal shrouded region of the rotor extends from the leading edge to slightly upstream the location of shock wave under near stall condition. Controlling the location of the tip leakage flow mitigates the interaction between tip leakage flow and shock waves, as well as the flow separation resulting from shock wave/boundary layer interactions, thus improving the stage performance. In NASA Stage 35, 20%–30% shrouded rotors can achieve both efficiency and stall margin improvements compared to the prototype. The 20% shrouded rotors exhibit an improvement in stall margin by 1.24% without any efficiency loss.
Calculation of the Overspeed at Emergency Shutdown of a Transonic Test Turbine Facility Using a Web-Based Thermodynamic Simulation Tool
Authors: Sanz Wolfgang , Perz Erhard , Göttlich Emil 
Published: August 2024

Abstract
The Institute of Thermal Turbomachinery and Machine Dynamics at Graz University of Technology operates a Transonic Test Turbine Facility of 3 MW power. The test turbine is a two-spool two-stage turbine. The high-pressure high-speed stage is connected to a brake compressor via a coupling, whereas the second low-pressure low-speed stage is connected to a water brake.
In the case of a coupling failure or a break-off of the water brake, an emergency shutdown is triggered in order to avoid excessive overspeed of the turbine stages, leading to blade dismantling or even disk bursting. For a previous one-stage setup, the shutdown procedure was developed and adjusted with the help of a dynamic thermodynamic simulation of the test rig which allowed to calculate the occurring maximum speeds. With this approach, the safe operation of the test rig shall be guaranteed.
This work presents a simulation model for the existing two-spool two-stage test rig. With a dynamic simulation, the overspeeds of the high-speed and low-speed shafts are calculated for the cases of coupling failure and water brake break-off as well as for the case of both shafts running freely. In this way, it is checked that the maximum speeds of the shafts in the case of an emergency stay within the allowable limits.
However, a break-off of the water brake in July 2022 led to higher overspeeds as predicted. The following investigations detected an error in the control system, which could have harmed the low-pressure turbine.
For the modeling and simulation, the newly developed web-based version of a thermodynamic simulation tool, IPSE GO, was used because it allows easy access to the simulation by all partners via a web browser.
Experimental and Numerical Investigation on Heat Transfer and Flow Characteristics of Array Jet Impingement Cooling With Film Extraction at the Turbine Shroud
Authors: Li Guodong , Guo Tao , Zeng Fei , Liu Cunliang , Li Jiayu , Li Changwei , Liu Shanjie 
Published: August 2024

Abstract
Jet impingement cooling is applied as an effective forced convection cooling method in regions with high thermal loads. This paper investigates the application of an array jet impingement with film holes extraction system on the turbine shroud. The cooling air is first accelerated through jet holes and impinging on the internal wall. Subsequently, the spent air is discharged in perpendicular directions through film holes. The distribution of wall Nusselt number is spatially resolved through liquid crystal thermography (LCT), and the flow structure of the impinging jets is obtained by 3D steady-state numerical simulation to further analyze the mechanism of jet-enhanced heat transfer. The effect of jet Reynolds number based on the jet hole diameter, jet-to-target spacing, and jet-to-jet spacing in the X and Y direction are investigated with a parameter range of 9100 ⩽ Re ⩽ 19800, 6.0 ⩽ H/D ⩽ 12.5, 4.0 ⩽ A/D ⩽ 7.5, 9.0 ⩽ C/D ⩽ 17.0. The results show that the wall heat transfer is mainly affected by the impinging jets, wall jets, the interaction between adjacent wall jets, and film hole extraction. The jet Reynolds number does not affect the flow structure and wall heat transfer distribution. The increased momentum decay of the jet flow due to the increase in jet-to-target spacing causes the wall heat transfer to decrease monotonically. The variation of jet-to-jet spacing in the Y direction has little effect on the area-averaged Nusselt number of the target wall, but it will shift the stagnation region. While the heat transfer at the sidewall is more sensitive to the jet-to-jet spacing in the Y direction. With the decreasing of the jet-to-jet spacing in the X direction, the area occupied by the stagnation gradually increases, thus, the area-averaged Nusselt number is significantly enhanced. In addition, other heat transfer regions are also significantly enhanced due to the increased amount of cooling air.
Efficient Energy Harvesting and Storage in Small-Scale Solar-Biomass-Micro Gas Turbine Systems
Authors: Simeoni Patrizia , Arnulfi Gianmario L. , Della Putta Andrea 
Published: August 2024

Abstract
In this paper, a small-scale plant operating in stand-alone mode, powered by a micro gas turbine and a solar system, is proposed and analyzed. The main consideration in this perspective is environmental sustainability, which drives the use of renewable energy sources such as solar energy and biomass. In this research, the proposed system comprises solar panels, a micro gas turbine and a battery. The gas turbine is fed by syngas generated by a gasifier, on its turn supplied by biomass. The biomass used consists of waste from food production, such as olive pits. The gas turbine, battery, gasifier and gas tank, together with their auxiliary devices, were modelled following the methodologies described in the technical literature and an in-house simulation code is suitably written. It includes a control system to manage the allocation of demand among solar energy, the gas turbine, and the battery. The aim is to keep the gas turbine away from low-efficiency conditions, while also taking into account the state of charge of the battery to avoid values that are either too low or too high. Initial results suggest a promising potential, with a preliminary analysis indicating a possible fuel (biomass) saving up to 15%. Potential improvements are currently under investigation.
Unique High-Resolution Temperature Mapping of Stage 1 Turbine Vane in a Long-Term Engine Test
Authors: Hickey Jim , Lee Jaebin , Counte Joseph , Rai Kieron , Lee Kidon , Mun Younggi , Araguas Rodriguez Silvia , Karagiannopoulos Solon , Hong Giwon , Feist Jörg P. 
Published: August 2024

Abstract
In this study, surface temperature maps, resulting from a long-term engine test, were evaluated on a stage 1 turbine vane using Thermal History Coatings (THCs). THCs are ceramic-type sensor coatings doped with a lanthanide ion, giving the coating photoluminescent properties. The THC’s structure permanently changes when exposed to high temperatures, which in turn alters its photoluminescent properties. Therefore, historic maximum temperature maps are evaluated by optically probing the THC point-by-point across the vane’s surface.
The vane was exposed to a non-dedicated (multi-cycle, multi temperature-level) engine test lasting over 8 months. Two passes of THC measurements were taken, termed Low Resolution (LR) and High Resolution (HR), each respectively with point pitches of 5 mm and 1 mm. The latter provided a unique insight into the historic maximum temperature profile of the vane, particularly around high temperature gradient regions, such as those close to effusion cooling holes. The THC temperatures were compared to the engine manufacturer’s (Doosan Enerbility) heat-transfer code (DiTACS) for validation.
The THC temperature mapping was successful with good coverage across the vane. The leading edge and pressure side trailing edge regions were typically the hottest. The HR measurements clearly show sharp thermal gradients around the effusion cooling holes on the vane’s aerofoil and platforms. Critically, the THC measurements compared very well to the DiTACS measurements, validating THCs as a credible temperature measurement technique for long-term, non-dedicated engine-tests for components operating in some of the most extreme environments of an engine.
Noise Reduction by Lowering the Jet Mach Number and Using Inverted Velocity Profile at Fixed Thrust and Mass Flow
Authors: Liu Junhui 
Published: August 2024

Abstract
Noise reduction concepts of lowering the jet Mach number and using the inverted velocity profile at fixed thrust and mass flow have been assessed by large-eddy simulations. This assessment involves a baseline jet that has a relatively high jet Mach number near 1.5, and Low-Mj jets that have jet Mach numbers barely above 1.0. The Low-Mj jets have either a uniform or inverted inlet velocity profile. Both noise reduction concepts can reduce the noise in the downstream direction. The combination of these two methods can achieve a noise reduction up to 3.5dB near the peak radiation direction. In addition, because the Low-Mj jets generate very low shock-associated noise, they produce a substantial noise reduction in the upstream forward) direction. However, the inverted velocity profile elevates the noise level at both the upstream and small aft angles. This noise elevation gets worse as the velocity ratio increases. Lowering the jet Mach number at the fixed thrust and mass flow reduces the turbulent kinetic energy. The inverted velocity profile further reduces the turbulent kinetic energy, but it elevates the high-frequency noise source intensities near the nozzle exit. These two competing effects produce a double peak pattern in the far-field spectral sound pressure levels in the peak noise direction.
Criteria for the Occurrence of Tip Leakage Flow Induced Rotating Instability
Authors: Chen Xiangyi , Lange Martin , Koppe Björn , Jasmund Christoph , Chu Wuli , Mailach Ronald 
Published: August 2024

Abstract
In axial compressors, an unsteady flow phenomenon associated with fluctuating tip leakage flow can be observed at stable operating points with high aerodynamic loading close to stall, named rotating instability (RI). Within the frequency spectrum, e.g., from wall pressure measurements, RI is visualized as a hump lower than the blade passing frequency. Since RI indicates an increase in noise level and might cause blade vibration and other undesirable structural issues, it has been a hot-spot topic in the turbomachinery community over the last decades. In this paper, a study on RI is performed based on a single compressor rotor row of the Low Speed Research Compressor at Technische Universität Dresden. Firstly, setups with a solid casing and a casing groove mounted over the shroud are investigated based on the configuration with a blade tip clearance of 4.3% tip chord length. The results show that RI properties are dependent on the operating condition (flow coefficient) and the casing groove. By implementing dynamic mode decomposition on the transient simulation snapshots, the coherent flow structure corresponding to the dominant frequencies of RI is extracted and visualized as a wave-like flow feature located in the blade tip region. The RI is essentially equivalent to the superposition of periodic unsteady behaviors of the tip leakage vortex (TLV). Furthermore, RI is not detected in the configuration with a reduced blade tip clearance (1.3% of tip chord length), as the tip flow becomes less unsteady. Based on the comprehensive analysis, two criteria for the occurrence of RI are concluded as follows: The tip leakage flow from one blade tip gap can influence the formation of the TLV originating from the adjacent blade, and the inherent unsteadiness of the tip flow is intensive enough.