bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a Transonic Fan Research Facility Focused on Casing Treatments and Inlet Distortion Effects
Authors: Cusator Andrew C. , Brown William J. , Dai Yuning , Bedke Andrew M. , Key Nicole L.
Published: August 2024

Inlet distortion, stall margin enhancement, and aeromechanic excitations such as flutter and forced response are important issues for modern day fans. These topics are often studied both experimentally and computationally. While computational models continue to advance, these issues often require time-accurate or coupled fluid-structure interactions, which can be computationally expensive. Thus, there is a need to have experimental data at engine-relevant conditions so that computational models can be developed and validated. These research topics were the motivation behind the design, build-up, and commissioning of a new fan research facility. The fan hardware, which was donated by Honeywell Aerospace, consists of an 18 in (0.46 m) transonic rotor with 22 blades and 53 stator vanes. At the design speed (near 19,000 rpm), the tip speed is approximately 1,500 ft/s (457 m/s). Power is supplied by a 3,000hp (2.2 MW) motor, and fan power is evaluated using a torquemeter and mass flow rate measurements. The mass flow rate through the machine is measured upstream of the fan with a bellmouth flowmeter, and the flow is throttled downstream of the stators. Since the rotor is representative of a small turbofan engine, the flow splits downstream of the stator for the core and bypass exhaust, and each can be independently throttled to control bypass ratio. The baseline aerodynamic performance of this research article was evaluated to lay the groundwork for future studies.
Techno-Economic Optimisation of Gas Compressor Station Location As a Decision Variable
Authors: Ojo Oluwatayo Babatope , Igie Uyioghosa , Pilidis Pericles
Published: August 2024

An economical natural gas transportation will require the lowest possible capital and operating expenditures over its lifecycle. To attain these conditions, the designers and investors must estimate the number of compressor stations (CS) that are needed along the pipeline route. More so is the need to determine their optimised locations at various pipeline segments along the pipeline. This study considers the techno-economic optimisation of the compressor station and pipeline segments, making up the proposed Trans-Saharan Gas Pipeline (TSGP) project. The optimised lifecycle cost, CS locations and pipeline segments are evaluated with the main aim of minimising costs. A SIMULINK model is developed using the techno-economic and environmental risk analysis (TERA) framework. The model is incorporated with an optimiser that enables an economic analysis of the TERA framework. Including the optimiser affects the outcome of the TERA in terms of the lifecycle cost. The optimisation problems are formulated considering the compressor station location as the decision variable. The lifecycle cost of the compressor stations and pipeline system is the objective function. A scenarios-based techno-economic optimisation study is performed to mimic the standard compressor station and pipeline system network configurations in the real world. The baseline case consists of 18 compressor stations at fixed locations along the pipeline route.

The results show 12 compressor station locations along the pipeline route with a reduction in the lifecycle cost by 12.95% in one of the optimised scenarios compared to the baseline case. The net present value is $28.77 billion assuming a discount rate of 15%. The optimised compressor station locations are at 1, 38, 76, 113, 150, 186, 222, 260, 296, 332, 368, and 408 segments of the pipeline. The outcome of the analyses shows the importance of the two-level optimisation algorithm utilised by the SIMULINK model for the integrated TERA. Hence, this study shows the potential of the TERA modelling and CS location optimisation method utilised in this research in guiding decision-makers on the selection of compressor-turbine configurations. These configurations will give the optimal lifecycle cost at the optimised compressor station locations along the pipeline route.
A Numerical Study of Emission Characteristics in Bluff Body Stabilized Turbulent Premixed Methane-Air Flames in Confined Environments
Authors: Girdhar Anant , Kalathoor Sriram P. , Jagoda Jechiel , Sankar Lakshmi N.
Published: August 2024

Emissions and blow-off are two of the most pertinent issues in the operation of gas turbine combustors. Typical combustors are operated heavily fuel lean to optimize performance. As a result of this, lean blow-off (LBO) becomes an important phenomenon to address. Leaner combustors are cleaner in terms of emissions. However, finding a good operating regime between fuel-lean conditions and allowable emissions can be complicated. This problem is further exacerbated due to turbulent combustor operating conditions. Simulating these problems requires high enough fidelity to capture the detailed flame dynamics and emission profiles. In this study, we reduce this problem to study emission profiles of very lean methane-air flames in a bluff-body stabilized combustor at conditions similar to those studied by Pathania et al (2019). Large eddy simulations are performed using OpenFOAM (an open source, fully compressible reacting flow solver). Two chemical kinetic models — the reduced 17-species and 73-reaction model by Sankaran (2007) and the detailed GRI 3.0 model — are compared in their ability to capture CO emissions in a confined environment. The turbulent Reynolds number associated with the bluff-body flameholder diameter is 38,000. The combustor operates in ambient conditions with no inlet preheat. Simulations are carried out over a computational domain of 4.5 million grid points, and the dynamic k-equation model is used to compute sub-filter stresses. Various flow-flame dynamics are analyzed to assess characteristics such as heat release rates and emission profiles. A comparative analysis of flow field regions (such as upstream, recirculation/flameholding and downstream regions) and their turbulence properties is done. A comprehensive assessment of the spatio-temporal evolution of key intermediate species is also carried out for both models. Finally, the reasons for their respective behaviors and effects on CO production are discussed.
Heavy Duty H2 Gas Turbine Demonstration – A Combined Experience
Authors: Demougeot Nicolas , Bullard Timothy , Kalb Bryan , Hernandez Fred , Spalding Martin , Yaquinto Matt , Soffritti Gabriele , van den Hout Franklin , Lee Dong Ki , Hwang Jun Won
Published: August 2024

Renewable energy sources are developing rapidly worldwide. The inherent intermittency of those is leading the electrical industry into finding alternate energy storage solutions and Hydrogen, a Carbon free fuel, is a prime candidate. South Korea is aspiring at being a World Leader in decarbonization of its energy sector and currently developing a dedicated, Carbon free, market.

Low pollutant Hydrogen combustion is notoriously difficult to achieve, low NOx in particular. Most OEMs are developing premix combustors but hurdles are numerous, adequate flashback margin being the biggest issue. PSM’s FlameSheet™ combustor was proven numerous times in various test rigs above the 80%vol H2 mark, but also in engines up to 25%vol H2. Full scale demonstration above 50%vol H2 in an engine was next.

PSM, Thomassen and Hanwha joined forces to move, convert and commission a 7EA capable of burning in excess of 50%vol H2. The site is located in the West of Korea, in a petro-chemical plant. Off-gas containing up to 40%vol H2 was used together with pure H2, and Liquified Natural Gas for start-up. A mixing station was designed to combine those three streams and precisely control a level of H2 in the mixture fueling the engine.

This paper will highlight the challenges faced and the solutions devised for the combustor, the fuel delivery system and the control sequences. Those were some of the key elements to success.

Safety was another important aspect and key principles will be described while an overview of the project will also be discussed.

After months of efforts including three months of commissioning, the GT achieved full load on April 14th, 2023. An official governmental measurement of 59.5%vol H2 and single digit NOx was demonstrated. The upcoming efforts will be briefly discussed.
Effect of Turning Vane on Tip Wall Heat Transfer in a Rotating Two-Pass Rectangular Channel
Authors: Huang Szu-Chi , Chia Kai-Chieh , Yeh Je-Wei , Liu Yao-Hsien
Published: August 2024

During gas turbine operation, the blade tip region experiences high thermal load. Adequate cooling near the tip is necessary to reduce thermal stresses and extend blade lifespan. This study examined heat transfer distribution on the tip wall of internal cooling channels through experimental measurement and numerical simulation. A two-pass rectangular channel with an aspect ratio (AR) of 1:4 and a hydraulic diameter of 25.6 mm was used. In the 180° turn region, both full turning vanes and slotted turning vanes were installed to minimize pressure loss while maintaining favorable heat transfer distribution. Thermochromic liquid crystals thermography and stroboscopic photography were employed in the experiment to obtain heat transfer distribution on the tip wall. The Reynolds number ranged from 10,000 to 30,000, while the rotation number ranged from 0 to 0.53. To increase rotation number, internal channel pressure was increased while keeping Reynolds number constant in order to decrease flow velocity. In the numerical study, ANSYS-Fluent R19.2 software was used for predicting flow field using a transition SST turbulence model with air as working fluid. The slotted turning vanes allowed flow impingement on the tip wall resulting in a higher heat transfer rate compared to cases with full turning vanes (10% higher). Both cases with turning vanes showed lower pressure drop and reduced heat transfer magnitude compared to smooth cases without turning vanes. Generally, rotation had less effect on tip wall heat transfer for cases with turning vanes due to reduction of rotation-induced secondary flow by these vane structures. The effect of channel orientation was less significant for cases with turning vanes compared to those without them.
Impact of Off-Design Performance of Turbines on Organic-Rankine Cycle Simulations for Solar-Power Applications
Authors: Yildirim Erdal , aus der Wiesche Stefan , Azmi Aktacir Mehmet
Published: August 2024

Organic Rankine Cycle (ORC) power systems offer a high potential for utilizing solar power for electricity generation. Inherently, the heat supply by solar power is time-dependent, and significant fluctuations occur during the day. Although some time-averaging of the heat input by thermal storage systems might be employed, the off-design performance of turbines is highly relevant for the mean thermal efficiency of such cycles. This study aims to analyze the effect of a hybrid power plant system obtained by combining an Organic Rankine Cycle (ORC) and a Linear Fresnel system (LFR) on the ORC turbine efficiency under part-load. The performance data of the LFR system is taken from an installed system designed to produce 20 kW of heat. The LFR-ORC system was modeled in detail, and thermodynamic calculations were performed using the cycle simulation program EBSILON. The local Direct Normal Irradiation (DNI) values for the selected day, the thermal efficiency of the system, and the temperature and mass flow rate of the thermal oil entering the system were used as inputs for ORC cycle. The ORC power plant was designed as a subcritical cycle with Novec 649 as the working fluid. The off-design performance of the ORC turbine used is compared with the nominal design operating performance using the Kroon and Tobiasz approach. The turbine efficiency as a function of the part-load operation was discussed within the framework of selected loss correlation. The analysis examined the thermal efficiency obtained from the turbine on the ORC side for varying thermal efficiency on the solar field side.
Aerodynamic Design Methodology for High-Load Compressor Blade Profiles at Low Reynolds Numbers
Authors: Xu Huafeng , Wang Mingyang , Zhao Shengfeng , Sheng Xiaoying , Lu Xingen
Published: August 2024

This study presents a novel design methodology that integrates design, experimentation, and computational fluid dynamics (CFD) to tackle the aerodynamic challenges of high loads and low Reynolds numbers (Re) in high-altitude, long-endurance unmanned aerial vehicle (UAV) engines. By applying high-speed experiments at low Re and large eddy simulation, a comprehensive database for high-load compressor cascades was constructed, covering Mach numbers from 0.4 to 0.7 and Re from 0.8 × 105 to 2.5 × 105. The fundamental strategy involves managing the pressure peak at the blade’s leading edge and load distribution. Precise velocity control at the leading edge and strategic load distribution optimization facilitate flow transition, inhibit separation bubble formation, and ensure blade aerodynamic efficiency and stability. Using this method, the article redesigns the rotor and stator blade profiles for a specific high-load booster stage. The design of the original rotor and stator blades was initially based on traditional methods and optimized using algorithms. The effectiveness of the methodology was validated through the integration of experimental data and extensive CFD analysis. Results demonstrate that this technique ensures excellent aerodynamic performance for high-load compressor blades under low Re and complex flow conditions. The findings significantly advance technological innovation, enhancing performance, endurance, and mission adaptability in high-altitude, long-endurance UAVs.
A Parallel Online Performance Optimization Method for ATR Engines Based on Ensemble Neural Network
Authors: Cai Weidong , Zhao Wei , Liu Binbin , Yang Xuesen , Luo Weiwei , Zhao Qingjun
Published: August 2024

To address the issue of lengthy optimization processes for ATR engines using swarm intelligence optimization algorithms such as Particle Swarm Optimization (PSO) and Genetic Algorithm (GA), a novel Ensemble Neural Networks based Parallel Performance Optimization (ENNPPO) methodology is proposed. This strategy amalgamates several small neural networks into a comprehensive larger model for the construction of an advanced onboard ATR engine model, moreover, the independence of each small neural networks allows for the reduction of computational time through parallel processing on GPUs. The method then harnesses the PSO algorithm to refine performance. Numerical simulations carried out with embedded GPU computing chips demonstrate that the average optimization time per test case is 0.28 seconds, with an energy consumption of 1.22 Joules. The proposed method achieves an optimization precision that is 78.40% and 84.30% higher than that of traditional neural network approaches and Linear Parameter-Varying (LPV) model methods, respectively. Furthermore, the computation speed is enhanced by a factor of at least 7.8 times than CPU, directly attributable to the expedited parallel processing enabled by GPUs.
Aerodynamic Characterization of an Industrial Inlet Particle Separator for Turboshaft and Turboprop Engines
Authors: Sanapo Carlo , Castaldi Marco , Mayo Yague Ignacio , Demolis Jacques , Eulitz Frank
Published: August 2024

Inlet Particle Separators (IPS) can be installed at the intake of turboprop and turboshaft engines as filtering protections, ensuring improved performance and operational stability in challenging environments. To validate and characterize novel IPS designs, it is essential to assess their performance before integrating them into the aircraft powerplant. In this paper, we aim at providing the experimental and numerical characterization of an IPS designed for industrial applications, defining a methodological approach that can be applied to similar test cases, as well as for training reduced order models. A comprehensive test campaign was undertaken at the von Karman Institute to analyze the pressure loss and separation efficiency of the IPS within an innovative test rig. This facility enables the exploration of different geometrical configurations and IPS flow regimes, mirroring real-world application and environmental conditions. The investigation mainly focused on parameters such as Reynolds number, bypass ratio and Stokes number. Both steady and unsteady Computational Fluid Dynamics (CFD) simulations with Lagrangian particle tracking were also performed, with two levels of resolution (based on the grid size), to gain more insights on the flow and particle trajectories inside the channels, and to complement the experimental findings. The reliability of the numerical tools is validated by comparing the CFD results with the experimental data. The authors specifically discuss on the discrepancies between the numerical and experimental outcomes in certain flow configurations, reasoning on the uncertainty analysis of the experimental data, and on potential deficiencies of the chosen CFD models.
Experimental and Numerical Investigation of NH3/H2/N2 Combustion in a Premixed/Stratified Swirl Burner
Authors: Davies Jordan , Mazzotta Luca , Sato Daisuke , Mashruk Syed , Pugh Daniel , Borello Domenico , Valera Medina Agustin
Published: August 2024

Interest in using renewably produced, partially cracked ammonia in gas turbines is gaining traction, but challenges relating to emissions of NOx and unburned ammonia remain. The present work progresses existing research on using hydrogen stratification to reduce NOx from ammonia/hydrogen flames by experimentally and numerically investigating the effects of also injecting nitrogen from the cracking process. It additionally assesses the NOx reduction capability of a recently developed novel swirl burner by adding hydrogen to the stratified flow to maintain the diffusive equivalence ratio at two high NO production conditions, slightly lean and stoichiometric.

At slightly globally rich conditions, maintaining the diffusive equivalence ratio at 0.9 resulted in an order of magnitude reduction in NO emissions with only a 33% increase in unburned NH3, compared to a fully premixed flame with the same fuel and air flow rates. This stratified configuration was found to increase consumption of NO by NH2, likely due to flame morphology effects, while NO production from OH and HNO pathways was reduced. The reduced OH intensity was posited as the cause for increased NH3 emission. A strong emissions sensitivity to diffusive equivalence ratio was found, as the case with a stoichiometric diffusive equivalence ratio did not show such marked improvements over its corresponding premixed condition. Both stratified and premixed flames were found to be stable, however stratification has potential to trigger instabilities at different frequencies to premixed.
Flow and Heat Transfer Characteristics in a Rotating Wedge-Shaped Cooling Channel With Detached Guiding Pin-Fin
Authors: Chen Jianian , Rao Yu , Xu Chao , Yang Li
Published: August 2024

Experiments and numerical simulations are conducted to investigate the flow and heat transfer characteristics of the guiding pin-fin array in a rotating wedge-shaped channel that represents the internal cooling passage features for turbine blade trailing edges. The rotating experiments cover Reynolds number ranges from 10,000 to 80,000 and rotation number ranges from 0 to 0.46. The results demonstrate that, with a proper arrangement, the guiding pin-fin array can significantly reduce the endwall temperature and pressure loss in the wedge-shaped channel. However, it was observed that at the mid-span of the guiding pin-fin array channel, heat transfer was relatively low, forming a high-temperature region. To enhance channel heat transfer uniformity, 2 mm clearances were introduced to the guiding pin fins at the channel root region, 2 mm from the trailing endwall. The numerical results show that this structural modification effectively improved the endwall heat transfer intensity at the mid-span of the wedge-shaped channel, particularly on the leading surface. In cases with Reynolds number (Re) equal to 50,000 and rotation number (Ro) equal to 0.075, the leading and trailing endwall Nusselt numbers of the detached guiding pin-fin array were 6.5% and 4.8% higher than those of the guiding pin-fin array. The secondary flow and transverse vortex induced by the detached pin fins reduced the main stream velocity, thereby inhibiting the Coriolis force effect and diminishing the endwall heat transfer discrepancy. Further comparisons at Re = 50,000 and Ro = 0.075 and 0.15 revealed that the leading and trailing endwall heat transfer discrepancy coefficient (δ) of the detached guiding pin-fin array was 61.8% and 42.2% lower than that of the circular pin-fin array, respectively.
LCA Modelling of Forged Components for Turbomachinery: Improved Approach Based on Production Data
Authors: Al Freijat Mosè , Orlandi Rachele , Ragni Giacomo , Pucciarelli Martina , Serra Angela , Fantozzi Francesco
Published: August 2024

Life Cycle Assessment (LCA) is a well-defined methodology employed to evaluate environmental impacts along the life cycle of products and services. Even if the methodology is standardized, its applicability relies on the availability of representative inventory data. Utilization of LCA in the turbomachinery sector is recent, therefore the lack of representative processes of this sector in commercial databases. Commercial databases provide generic processes, not always representative of the turbomachinery industry processes, which may increase the uncertainty of the LCA results and provide low accuracy. An example is the forging process, which is employed to manufacture most turbomachinery components, due to high material properties requirements. The forging process strictly depends on geometry, material, and size of component to be produced. Ideally, for each forged item, primary data would be collected to create and inventory and an LCA model. The data collection but would require a huge effort in terms of time by the forging industry and the LCA practitioner. Up to now, the lack of primary data on the specific processes has been overcome by leveraging on company validated information. This article presents an approach to overcome the lack of primary data to be used to model the forging process of semi-finished components considering all the processes required for its production. A simplified model has been developed, based on validated databases and Baker Hughes’supply chain real data. This model allows a quick and more accurate estimation of the environmental impact in terms of Carbon Footprint (CF) of forging process with a lower uncertainty compared to commercial database.
Investigation of Grooved Front Plate for Inlet Swirl Reduction in Brush Seals
Authors: Abbas Abdullah M. , Pekris Michael J. , Chew John W.
Published: August 2024

Brush seals are plausible replacements for conventional labyrinth seals in gas turbines for managing internal air system flows and leakages. They can offer superior leakage performance compared to labyrinth seals due to their compliant nature, and a reduced effective clearance during operation. Despite their improved sealing performance, highly swirling flow and aerodynamic forces on the upstream bristles could lead to aero-elastic instability within the bristle pack. This study investigates grooves as a means of improving brush seal robustness in high-shaft speed locations by reducing the inlet swirl that is incident on the bristle pack. The material removed and implied manufacturing effort and cost are considered. A parametric study of a simple groove geometry was conducted using CFD and a porous medium representation of the bristle pack whose resistance coefficients were calibrated to Bayley and Long’s data to achieve representative seal leakages. This identified groove length, width, angle and pitch as the important groove parameters for swirl reduction and demonstrated that the performance of ribs from previous research can be replicated and improved upon. A Design of Experiments (DOE) approach was adopted to investigate a novel groove design geometry. Combining a horizontal channel with an inclined groove enables a higher pitch to achieve the same swirl reduction by increasing drag and exploiting fluidic effects. The results indicate that the novel groove design performs as intended in substantially reducing the swirl incident on the bristle pack. Adding these features to the traditional front plate may improve brush seal robustness by reducing the effect of aerodynamic forces which could drive bristle pack instabilities, thus having the potential to aid their deployment in high-radius or high-shaft speed engine locations.
Investigation of Conjugate Heat Transfer in Wall-Modeled Large Eddy Simulation of High-Speed Compressible Wall-Bounded Flows
Authors: Muller Julia A. , Dutta Meghna , Boisvert Joshua , Oefelein Joseph C.
Published: August 2024

A parameter study is performed in a compressible boundary-layer at supersonic conditions to investigate the accuracy of a validated loosely-coupled Conjugate Heat Transfer (CHT) model combined with an advanced wall model approach for Large Eddy Simulation (LES). Fully-coupled CHT typically introduces extreme additional cost to numerical simulations due to large time-scale disparities between processes in the fluid and solid domains. Loosely-coupled CHT methods seek to mitigate this cost while simultaneously maintaining the correct boundary layer dynamics and local heat transfer processes. Likewise, wall-modeling makes LES more computationally tractable, but has not been widely used with CHT. The current investigation demonstrates the performance (accuracy and computational cost) of these approaches when implemented as a unified model. Results demonstrate that the selected wall-modeled LES, combined with a fully-integrated loosely-coupled CHT model, can reproduce the accuracy of reference DNS and wall-resolved LES data with orders of magnitude reduction in cost. Moreover, they demonstrate the implementation requirements necessary to achieve this accuracy.
Prediction of a Crack Propagation in a Steam Turbine Rotor
Authors: Chatterton Steven , Pennacchi Paolo , Vania Andrea , Dassi Ludovico
Published: August 2024

The early detection of shaft cracks in rotating machines is essential to avoid catastrophic damage, long outages and high maintenance costs. An increasing number of transverse and circumferential cracks caused by thermal fatigue have been detected in steam turbines, in recent years. Because of usual long-time intervals between two subsequent planned inspections of the rotors, it is very important to identify the presence of a shaft crack by the online analysis of the harmonic content of the machine vibrations measured by Condition Monitoring Systems. As the symptoms caused by shaft cracks in the system response are often masked by the effects induced by other common malfunctions, it is very useful to study the sensitivity of the dynamic behavior of turbine shafts to the propagation of transverse cracks and to predict the lowest value of the crack depth that can cause detectable symptoms in the machine vibration. This paper shows the results provided by a numerical approach, aimed at identifying the propagation of shaft cracks, which has been applied to the analysis of a real intermediate-pressure steam turbine in which a first crack initiation had been detected.
A High-Performance Code for Analyzing Loss Transport Equations in High-Fidelity Simulations
Authors: Biassoni Daniele , Russo Matteo , Viviani Paolo , Vitali Giacomo , Lengani Davide
Published: August 2024

The subject of the present paper is the development of a general procedure to calculate the terms of the total pressure transport equations using a High-Performance Data Analytics (HPDA), based on Proper Orthogonal Decomposition (POD) and leveraging on High Performance Computing. This method is applied to data obtained from high fidelity simulations of low pressure turbine (LPT) blades in order to separate the different loss contributions and to visualize the associated structures to the fluid dynamics phenomena that occur inside the passage. This procedure is developed in Python environment because it easily allows parallel computing.

This paper discusses the mathematical framework behind the decomposition of total pressure transport equation and its implementation in Python. The scalability tests are performed for two exemplary datasets and compared to previous implementation showing a considerable speed-up. The procedure applied to Large Eddy Simulation (LES) data shows significant improvement over traditional approaches. It provides more detailed information about the phenomena associated with the generation of losses in the turbine blades, allowing for quick identification of where these losses occur. The HPDA code can be applied to all high fidelity simulations (LES and DNS) in order to get more information from simulations that are extremely expensive, allowing the full exploitation of such large datasets. In addition, to demonstrate the ease of code’s implementation, the data obtained from the POD are compared with data obtained from Fourier decomposition to validate the procedure. The procedure is open access and available in an online repository.
Towards Low NOx Emissions Performance of a 65kW Recuperated Gas Turbine Operated on 100% Hydrogen
Authors: Villatoro Walther , Slope John , McDonell Vincent , Hu Ray , Steele Robert
Published: August 2024

This work supports the development of a low NOx emission 65 kW natural gas turbine capable of operating on 100% hydrogen. This gas turbine has been demonstrated to operate from cold start to full load on up to 30% hydrogen mixed into natural gas with single digit ppm NOx emissions. To reach operation on 100% hydrogen, injectors specifically designed to 1) avoid challenges with flashback and 2) be field retrofittable were developed and tested. The injectors must be designed to prevent flashback while having a high degree of mixing coupled with fuel lean operation to achieve desired low NOx emissions. Successful operation of the engine from cold start to full load on 100% hydrogen was demonstrated. With the successful demonstration of operability, the new injectors serve as a starting point to improve the turbine performance and emissions when operated on hydrogen. To support the development, a chemical reactor network (CRN) is used in conjunction with experimental injector mixing characterization. The CRN analysis predicts NOx using perfectly stirred reactors (PSR). A strategy to account for variation in mixing performance was developed and utilized with the CRN to connect NOx emissions to the injector mixing performance. Fuel concentration profiles produced by different injector designs were measured and the CRN model was used to infer the effects on NOx emission. The CRN model was validated/tuned using measured NOx emissions data from two combustion liners and two injector designs and the corresponding measured injector fuel distributions. The results illustrate how NOx emissions are directly influenced by local fuel rich regions found at the injector outlet. The CRN model can thus be used to screen injector designs and infer NOx performance and will be used to guide the development of injectors for hydrogen that can attain desired fuel distributions, concentrations, and velocities. The results affirm the direction needed to attain improved mixing and to operate at overall leaner conditions made possible by the stabilizing features inherent to hydrogen.
A High-Speed, High-Temperature Micro-Cantilever Steam Turbine for Hot Syngas Compression in Small-Scale Combined Heat and Power
Authors: He Victoria , Van Herle Jan , Schiffmann Jürg
Published: August 2024

Coupling a biomass gasifier with a solid oxide fuel cell system through a high-temperature syngas compressor holds great promise to achieve low-emission, small-scale combined heat and power, since it reduces the number of heat exchangers and increases the system efficiency. However, due to the demanding operating conditions (high temperatures, toxic and explosive gases), electrical motors are not suitable to drive the syngas compressor. Therefore, a high-speed, small-scale cantilever steam turbine that can valorize the system’s waste heat to power the compression is designed and developed. An iterative process involving preliminary design, meanline analysis, commercial tools, and in-house codes is used for the design. The design is then numerically analyzed using computational fluid dynamics. The 2.8 kW cantilever steam turbine with a tip diameter of 21 mm runs up to 210 krpm at temperatures of 525°C while being supported on dynamic steam-lubricated bearings. A low-reaction, full-admission design has been chosen to lower the steam consumption, the axial forces, and the turbine backface leakage. The turbine rotor is made of Ti6Al4V and coated for structural integrity and to withstand high temperatures. Despite the small scale of this design, the results obtained from the established correlations based on large-scale turbines yield a remarkable concordance with the results from the numerical analysis, in particular for the isentropic expansion efficiency prediction.
Evaluations of Superposition Predictions of Adiabatic and Overall Effectiveness for Three Rows of Film Cooling Holes With Differing Hole Geometries
Authors: Ellinger Molly E. , Flachs Elise M. , Kulkarni Ameya N. , Bogard David G.
Published: August 2024

Prediction of film cooling performance on turbine airfoils with multiple rows of film cooling holes based on the measured performance of a single row of holes relies on use of superposition analysis. There have been many past studies of superposition predictions of film cooling adiabatic effectiveness with similar hole shapes, either cylindrical or shaped holes. Recently there has also been a study proposing using a superposition technique to predict overall cooling effectiveness for multiple rows of film cooling holes. In this study, superposition predictions for adiabatic effectiveness and overall cooling effectiveness were evaluated for multiple rows of film cooling holes with varying hole geometries. The test configurations used mimicked the influence of upstream showerhead film cooling holes followed by either baseline 7-7-7 holes or an additively manufactured optimized film cooling hole which included external vortex generators that improved attachment of the coolant jets. Results showed the commonly used Sellers superposition model provided reasonable predictions of adiabatic effectiveness for the more standard 7-7-7 holes, but poor predictions for the optimized holes using vortex generators. Accuracy of the predictions of overall cooling effectiveness based on measured adiabatic effectiveness were found to be good.
Effects of Recess Depth and Orifice Diameter on Pneumatic Hammer Instability in Hydrostatic Thrust Bearings: Analysis and Experimental Validation
Authors: Lim Homin , Kim Kyuman , Ryu Keun
Published: August 2024

Hydrostatic thrust bearings are required in various turbomachinery systems due to their substantial load capacity and superior rotor axial positioning capabilities, which minimize friction and heat generation. However, when lubricated with compressible fluids, these bearings can experience pneumatic hammer instability especially if the recess volume is significant. This study aims to establish design guidelines and experimentally validate the performance of hydrostatic thrust bearings, with a focus on predicting and mitigating pneumatic hammer instability. The research includes an investigation into the static load characteristics of these bearings when operated with air as the lubricant. The analysis in this paper covers the effects of varying supply pressures, recess depths, and orifice diameters on pneumatic hammer instability, as well as on the load capacity, stiffness, and damping coefficients of the bearings. To validate these findings, experiments are conducted using two test bearings with differing recess depths and orifice diameters. The results from both predictive models and experimental data consistently show that a shallow recess depth is effective in preventing pneumatic hammer instability without notably diminishing the bearing load capacity. Nonetheless, modifying the orifice diameter to control pneumatic hammer instability requires careful design consideration, as it might lead to decreased load capacity and stiffness. This research addresses the challenge of preventing pneumatic hammer instability in hydrostatic thrust bearings through a combined approach of numerical analysis and experimental testing. It contributes significantly to the field by offering practical design recommendations for optimizing recess depth and orifice diameter. These guidelines aim to eliminate pneumatic hammer instability while preserving critical performance aspects of hydrostatic thrust bearings, such as load capacity and stiffness.
Impinging Jet Heat Transfer of Liquid Carbon Dioxide at Constant Enthalpy
Authors: Park Seong-Hyeok , Kim Seon Ho , Hsu Wei-Ting , Park Hee Seung , Cho Hyung Hee
Published: August 2024

This study focuses on investigating the heat transfer characteristics of boiling with liquid (subcritical) carbon dioxide impinging jet at identical enthalpy conditions, specifically examining the influence of varying operating pressures on its behavior. The experiments were conducted within a range of operating pressures from 6.37 MPa (0.86 PC) to 7.30 MPa (0.99 PC), slightly below the critical pressure, PC, of 7.38 MPa. Using RTD sensors equipped with a thin film ITO heater, this study measured the wall temperature and wall heat flux at the stagnation point, enabling the calculation of the heat transfer coefficient. The impinging jet, operating at a Reynolds number of 40,000, was directed onto the impinging plate through a 9.4 mm-diameter nozzle. The findings reveal that at the liquid state, the wall temperature at the stagnation point rises in correspondence with the increase in wall heat flux. Moreover, at the given pressure, the wall temperature eventually reaches a saturation point as the wall heat flux continues to increase, leading to the emergence of wall superheat at an operating pressure of 6.37 MPa. However, as the operating pressure increases, the phenomenon of wall superheat diminishes, eventually nearly vanishing.
Cooling System Topology of High-Endurance Dual Stack Proton Exchange Membrane Fuel Cell System for Heavy Duty Trucks
Authors: Nguyen Huu Linh , Yu Sangseok
Published: August 2024

The adoption of proton exchange membrane fuel cell (PEMFC) technology in heavy-duty trucks represents a promising solution for addressing the pressing issues of emissions and sustainability in the transportation sector. Achieving high-endurance operation is critical for the success of these systems, and effective cooling is central to this goal. This paper explores innovative cooling topologies and control strategies designed to extend the endurance and operational longevity of dual PEMFC stack systems in heavy-duty truck applications. To address these issues, a comprehensive analytical model for a dual PEMFC stack system is developed to assess the heat generation within the fuel cell stacks, enabling a meticulous evaluation of the cooling requirements. Two strategies for controlling coolant bypass flow are evaluated, one based on coolant temperature and the other based on stack temperature, during dynamic operation. Three different topologies are designed to achieve efficient cooling systems, and their impact on parasitic power and energy consumption is examined. The results suggest that control strategy in which the bypass valve open ratio is controlled based on the stack temperature, performs better in regulating the fuel cell operating temperature precisely. Among the various topologies, the distributed topology which involves setting up two independent cooling systems for each stack, significantly reduces energy consumption. In particular, it saves up to 71% of energy consumption compared to the integrated topology, where a single cooling system is used for both stacks.
An Innovative Filtering Apparatus for Gas Turbines
Authors: Zanini Nicola , Suman Alessio , Piovan Mattia , Pinelli Michele , Rossin Stefano , Minotti Stefano
Published: August 2024

Air contaminants can severely affect the life of gas turbines. Particles that enter the compressor section can interact with the internal surfaces of the machine leading to the modification of the airfoil shapes and surface roughness. Depending on the particle size and chemical composition, thus the working site of the gas turbine, different degradation mechanisms can occur, such as fouling, erosion, and corrosion. All these phenomena implicate performance drops over time and reduce the reliability of the plant. Multistage filtration systems are usually employed to reduce the contamination at the heavy-duty gas turbine inlet. Inertial separators, wet barriers, self-cleaning filters, and media filters work together in the so-called “filter house” to obtain the most appropriate filtration system according to the contamination of the surrounding environment and the contaminant typology. Inertial separators are more effective against bigger particles (> 10 μm) while media filters can capture smaller ones (< 10 μm). Media filters are commonly installed in the last stages to face the smaller residual particles captured. The continuous exposure to contaminants leads to the increment of the pressure drop and consequently, the media filter replacement is required after having reached a threshold pressure drop. In this work, an innovative particle separator that combines an inertial barrier with a high-voltage electric field is presented. An extensive experimental laboratory-scale campaign is carried out to evaluate the performance of the device against different types of contaminants, particle concentration, and environmental conditions.
Numerical Prediction of Lean Blow Out Event in an Industrial Gas Turbines Through an LES Based CFD Analysis
Authors: M. Rajesh , R. Meloni , A. K. Arun
Published: August 2024

Combustion processes operating under fuel lean conditions can reach very low emissions and extremely high efficiency. However, ultra-lean combustion is more prone to thermos-acoustic instabilities and the flame can even get extinguished by the blowing out of the combustion chamber. Hence the Lean Blow-Out (LBO) limit plays a critical role in the stable performance of gas turbine combustors since it represents the boundary between the flame extinction and the stable flame region. The occurrence of LBO in real engines can significantly reduce the engine availability and operating reliability. Therefore, early detection of LBO is a key performance parameter that needs to be investigated. In this way, the engine can be guided through precautionary actions using a control system, like setting the max air-to-fuel ratio, changing the split among fuel lines, etc.

From a numerical perspective, the unsteady phenomena of LBO are indeed challenging to be captured as the flame is marching towards to the quenching conditions from a stable point. The present work leverages the capabilities of a tabulated chemistry approach in predicting the process of a lean blowout occurring in a swirled technically-premixed flame. One of the experimental events conducted at high pressure and high temperature to understand the LBO event for a given geometry/fuel composition is considered as benchmark condition for the numerical investigation. The paper will presents the validation of the numerical model/approach against the experimental measurements. More in detail, an Extended Turbulent Flame Speed Closure (ETFC) model was implemented to introduce the effect of stretch and heat loss on the partially premixed flame. The exploitation of the numerical results is carried out through the analysis of the main fields like the heat-release rate, the pressure fluctuation and the temperature. The extinction equivalence ratio is predicted quite accurately, showing that the ETFC is suitable for the study of the blow-off for the partially premixed flames, without an increase in computational cost. The presented methodology would serve as the primary benchmark for assessing the models’ effectiveness in capturing the flame dynamics: the approach can be extended/repeated to other operating conditions of the combustor to define the LBO map for a finite TCD range and different fuel split.
Structural Dynamics of an Axial Compressor’s Rear Blisk Drum and Multi-Stage Coupling
Authors: Gambitta Marco , Beirow Bernd , Klauke Thomas
Published: August 2024

Modern turbomachinery compressor design favors the introduction of multi-stage drums to reduce the components’ weight and increase the machine efficiency. The drum design creates a direct connection between the stages, which can lead to a collaboration of the stages in the system structural dynamics. This motivates the investigation of multi-stage coupling for the structure. The objective is to propose a method to characterize such collaboration for coupled components.

To investigate the multi-stage coupling, the analysis of the structural dynamics has to consider the drum system. In consequence, compared to the investigation of individual stages, significantly higher computational costs are expected. Moreover, also when considering the tuned reference geometry, the full drum loses the cyclic symmetrical property of the individual stages due to the different airfoil counts. A reduction method to compute the system modes is investigated, taking advantage of the nominal individual stages’ periodicity. The quality of the results is assessed comparing the computed mode-shapes and natural frequencies with the respective full model of the investigated drum.

The identification and quantification of the coupling is finally crucial to describe the structural dynamics of the drum system. Modes with high coupling show a co-participation of the stages in the dynamics. This implies vibrational responses on a stage due to the excitation of a different drum row. In this work, a formulation for an index is proposed, named coupling strength, to quantify the intensity of this collaboration for each mode. The formulation considers an arbitrary number of stages and can be extended in general to different coupled structures.
Guideline for Large-Scale Analysis of Centrifugal Blower Using Wall-Resolved Large Eddy Simulation
Authors: Tsukamoto Kazuhiro , Kato Chisachi
Published: August 2024

In order to reduce the number of prototypes during product design and accurately predict unsteady phenomena occurring at off-design points, a method for accurately predicting the performance of centrifugal blowers through numerical analysis is required. This paper presents a guideline for accurately predicting the performance of centrifugal blowers using compressible flow analysis with Large Eddy Simulation (LES). In LES analysis, it is important to have a grid resolution that resolves the minimum vortex scale near the wall (referred to as wall-resolved LES) and to consider detailed geometry such as the length of the suction pipe.

The calculations in this study used a model blower, which is a scale model of a single-stage centrifugal blower for use in industrial plants. The model blower was experimentally measured for various parameters such as the blower pressure coefficient, the static pressure rise coefficients of the impeller and vane-less diffuser, the shaft power, and the pressure fluctuations at the inlet of the impeller and the inlet of the vaneless diffuser. The results of these measurements were compared with those obtained from the wall-resolved LES.

The study confirmed that the accuracy of performance prediction can be improved to less than a 4.0% error in the blower pressure coefficient at both design and off-design operating points by resolving the minimum vortex scale with 14.6 billion grid elements and considering the detailed geometry.