bluuebunny/crossref_metadata_2025_split huggingface dataset:
CO2-Based Power Cycles: What Effect Does Additive Molecular Complexity Have on the Cycle Layout?
Authors: Aqel Omar , White Martin , Sayma Abdulnaser 
Published: August 2024

Abstract
Since their inception, CO2 power cycles have gained prominence for their superior performance and compactness. However, the efficiency of the simple supercritical CO2 cycle is hindered by relatively large temperature differences in the recuperator, leading to increased exergy destruction. Although complex cycles like the recompression or precompression cycles can reduce recuperator irreversibility, their higher complexity and additional equipment requirements raise the cost of the power plant.
This paper aims to demonstrate that recuperator irreversibility in a simple recuperated transcritical cycle can be alleviated using CO2-based mixtures, without resorting to complex cycles. This is achieved by comparing the efficiencies of simple and recompression cycles using CO2-based mixtures with nine additives of various molecular complexities: H2S, SO2, C3H8, C4H10, C5H12, C6H6, C4H4S, TiCl4, and C6F6. The effect of additive molar fraction (ranging from 0.05 to 0.5) on the efficiency of both cycles is examined.
Thermal efficiency optimisation reveals a correlation between the efficiency difference of the simple and recompression cycles and the molecular complexity of the working fluid. The reduction in recuperator irreversibility is attributed to the decrease in the difference in the isobaric specific heat capacities between the streams in the recuperator with the use of complex additives. Consequently, the advantage of a recompression cycle diminishes as the aggregate molecular complexity of the working fluid increases. Simple additives like H2S, SO2, and C3H8 result in recompression cycles outperforming simple recuperated cycles by 4% to 8% in terms of absolute thermal efficiency, depending on the additive and its molar fraction. Conversely, more complex additives like C4H4S, TiCl4, and C6F6, exhibit thermal efficiencies in simple recuperated cycles comparable to those of recompression cycles. The additive molar fraction at which both cycles achieve similar performances depends on the molecular complexity of the additive; the more complex the additive, the lower the additive molar fraction required to create a complex working fluid. Moreover, the split fraction in recompression cycles exhibits a similar correlation with molecular complexity as observed in the efficiency difference, suggesting that recompression cycles will morph into simple recuperated cycles as molecular complexity increases.
In conclusion, the use of additives provides an additional dimension through which the efficiency of CO2 cycles can be optimised, enabling improved performance without the need for complex cycles.
Development of Thermo-Mechanical Service-Like Testing for Supercritical CO2 Expanders
Authors: Bucciarelli Federico , Checcacci Damaso , Macoretta Giuseppe , Disma Monelli Bernardo , Bertini Leonardo 
Published: August 2024

Abstract
The detailed prediction of the actual life expenditure of expanders operating in power plants has become a common topic of investigation. In the current energy market axial expanders are subjected to frequent load change and to the exposure to higher temperatures. The proper prediction of their life expenditure determines operability and availability improvements through faster start-ups and longer maintenance intervals. A common strategy to achieve this objective has led in the last years towards the development of progressively more and more detailed “service-like” tests aimed at recreating the actual loading conditions in terms of strain and temperature profiles. Recently the need to face the challenge of energy transition through the introduction of advanced cycle employing supercritical carbon dioxide is requiring to further improve this kind of tests by including the effect of environmental attack through corrosion and carburization. This work addresses this topic by presenting the development of customized specimens and of a testing campaign able to evaluate the degradation of creep and fatigue capabilities when high temperature carbon dioxide exposure occurs. After a short introduction on the state of the art, the specimen design will be detailed with FE simulation evaluating stress and temperature distribution in specimens and key insights will be given regarding the design of a proper test matrix and the essential theoretical framework for the interpretation of the results of a testing campaign.
GPU-Accelerated Full-Wheel Large-Eddy Simulations of a Transonic Fan Stage
Authors: Wang Kan , Bose Sanjeeb , Ivey Christopher 
Published: August 2024

Abstract
A single-stage transonic axial-flow fan is simulated using GPU-accelerated wall-modeled large-eddy simulations. The computational meshes are generated using Voronoi-diagram based approach. Two types of mesh are employed for grid sensitivity study. The first type uses isotropic hexagonal close-packed (HCP) seeding whereas the second combines the background HCP mesh with anisotropic boundary-layer type of mesh around the blade surfaces. The effect of the rotor tip clearance is examined using a rotor-only configuration. Sweep of the performance curve at full rotation speed is carried out for both the rotor and the stage. The computational results are compared against the experimental measurement and excellent agreement is observed when adequate near-wall resolution is employed. The code performance of the GPU-accelerated solver is compared to the CPU-based version. The high throughput of the GPU solver significantly reduces the computational cost. On a mesh with 84 million control volumes, 10 rotor revolutions can be computed within one day using 20 GPUs.
LES Analysis of Loss Anomaly of a Turbine Blade With Large Trailing Edge Radius
Authors: Miki Kenji , Ameri Ali , Giel Paul 
Published: August 2024

Abstract
There is great interest in the usage of Ceramic Matrix Composites (CMC) as a turbine blade material. However, depending on the manufacturing process of the CMC, blades may have a thicker trailing edge. The design space therefore needs to be updated due to the resulting flow physics. Recently, experimental results acquired at NASA Glenn Transonic Turbine Blade Cascade Rig showed that a loss measure generally increased with increasing trailing edge thickness. For some cases however, the general downward trend of the loss with increasing Reynolds number was interrupted by a local loss peak around Re ∼1.24 × 106, and then subsequently dropped to the original pre-peak trend. A possible cause of this intriguing phenomenon was speculated to be transonic vortex shedding, which is the mechanism of vortex shedding promoted by reflected shed pressure waves at the trailing edge at relatively high Reynolds numbers and transonic Mach numbers. A Reynolds-averaged Navier-Stokes (RANS) analysis or an under-resolved large eddy simulation (LES) does not reproduce this apparent anomaly and thus a highly-resolved LES (the total mesh count of ∼290 million cells) was performed to investigate the aerodynamics of the CMC blade. The numerical results at Re = 1,246,350 show that the pressure waves generated by the vortex shedding in the wake travel upstream and significantly influence the transition and separation on the suction side thus enhancing the vortex shedding in the wake. This feedback does not hold under a low-Re condition (Re = 621,900). The Reynolds number dependence was also examined by numerical perturbation of the pressure waves in the wake and by examining how such perturbation attenuates or endures. It is confirmed that the perturbation of the pressure waves is quickly damped below a set Reynolds number.
Effect of Variable Stator Vanes With Penny Cavities on the Performance and Secondary Flow of a Single-Stage Axial Compressor
Authors: Chen Shuaitong , Chen Shaowen , Zhang Yimin , Yang Pengcheng 
Published: August 2024

Abstract
The present study focuses on the first stage of the E3 which is a typical variable compressor, comparing its performance with and without pennies. The changes in overall performance from the penny structures are investigated. Furthermore, a detailed analysis is carried out to investigate how the two kinds of gap influences the three-dimensional flow field at the blade tip and the corner separation zone. Using unsteady calculation methods, the flow characteristics and unsteady behavior of two kinds of gap leakage flow caused by the penny structures in the shroud and hub are discussed. The results show that the pennies on the endwalls significantly diminishes overall performance at the design speed, leading to a decline in isentropic efficiency and total pressure ratio by 1.79% and 1.8%, respectively. The secondary flow losses caused by the variable stator vanes structures accounts for 68.6% of the stator losses. Compared with the hub, the momentum rate distribution of penny cavity leakage flow at the casing is stronger and more concentrated, resulting in larger losses and wider influence range. At the same time, the counter-rotating leakage vortex pairs are found in the flow field near the shroud and hub, in which the radial gap leakage vortices have a relatively stable vortex structure in the flow field, while the penny cavity leakage vortices are generated in the form of shedding vortices and then broken into smaller three-dimensional vortices, and dissipate while rotating around the radial gap leakage vortices.
Characteristics of Premixed Ammonia/Methane/Air Blends As an Alternative Fuel in a Swirl-Stabilized Gas Turbine Combustor Under Varying Pilot Percentage
Authors: Das Chaudhury Meghna , Sahoo Abinash , Nonavinakere Vinod Kaushik , Fisher Wesley , Ekkad Srinath V. , Naranaswamy Venkateswaran , Fang Tiegang 
Published: August 2024

Abstract
Alternative low carbon fuel blends are a promising way towards clean energy transition in the transportation and power generation sectors. In this work, the objective was to study the combustion characteristics of one such low carbon fuel blend (premixed Ammonia, Methane and Air) in a swirl stabilized Gas Turbine Can Combustor under varying % of pilot fuel flow (= 8 % to 10 % of the main fuel flow rate) at atmospheric pressure conditions. Pure Methane was used as the pilot flame which helped in the ignition and stabilization of the main flame and was kept on throughout the experiment. Different volume % of Ammonia and Methane blends were analyzed (starting from 10 to 50 % Ammonia in the fuel blend and the rest being Methane) at Reynolds number of the incoming air ∼ 50000, and at equivalence ratio = 0.6 and 0.7. Characteristics such as Combustor liner wall heat load and flame stability were studied using the Infrared Thermography technique and High-Speed flame imaging respectively. Additionally, both carbon and NOx emission trends were estimated for selected cases using the CONVERGE CFD software under steady state conditions incorporating the RANS RNG k-ϵ and SAGE modeling techniques. Among all cases, wall heat load was observed to be the least for the 50 % Ammonia-50 % Methane case and for cases under reduced pilot %. Also, under reduced pilot %, flames were mostly unstable wherein the manifestation of instabilities at equivalence ratio = 0.6 and 0.7 were markedly different from one another.
Performance and Flexibility of the DLN 2.6e Combustion System on the 7HA.03 Gas Turbine
Authors: York William D. , Cai Jun , Stoia Lucas J. 
Published: August 2024

Abstract
At GE Vernova, the newest advanced dry-low NOx (DLN) combustion system for HA gas turbines is the DLN 2.6e. After describing the key enabling features of the DLN 2.6e, this paper focuses on the emissions performance and operational flexibility of the combustion system on the 7HA.03, currently GE Vernova’s most efficient gas turbine in the 60 Hz electric power generation segment. While some full-scale, single-can lab results are presented, the primary focus of this manuscript is the performance on natural gas fuel from the testing of three 7HA.03 gas turbines, one at the GE Vernova full-load test stand and two at a commercial generating facility.
The DLN 2.6e is a can-annular, lean premixed combustion system. The advanced premixer at the head end efficiently mixes fuel and air in straight tubes, which are arranged in three fueling circuits. Additionally, the DLN 2.6e system has four axial fuel staging injectors located in the downstream half of the combustion liner, split into two fueling circuits. At high load, the axial fuel stage creates a secondary combustion zone with a substantial fraction of the total energy release and with a low residence time to the combustor exit plane. These features, along with the efficient premixing at the head end, enable the system to achieve below 25 ppm NOx at 15% O2 at the high firing temperatures of the 7HA.03. From full load, the combustor exit temperature may be lowered to attain 5 ppm NOx at 15% O2 before lean blow out occurs. At low loads, the fuel flow to one of the two axial fuel stage circuits may be eliminated, enabling the system to achieve less than 25 ppm NOx at 15% O2 and 9 ppm CO emissions down to near 15 percent of gas turbine full load.
7HA.03 engine data is presented showing low combustion dynamics and little change to emissions when running with cold fuel, representing a 22 percent increase in modified Wobbe index compared to the heated fuel design point. The combustion and control systems support accelerated load ramping. A 7HA.03 gas turbine was demonstrated to progress from ignition to full load in around ten minutes. Finally, the DLN 2.6e has been demonstrated in lab testing to be operable with up to 50% hydrogen by volume in the fuel, and an associated increase in NOx emissions was observed.
Turbine Rear Frame Interface – Thermal Modelling Improvement Using CFD Based Approach
Authors: Soundiramourty Sendilkumaran , Tippireddy Vishnu Vardhan Reddy , Cubeda Simone 
Published: August 2024

Abstract
In the power generation world, Aero-derivative Gas Turbines plays an important role due to their inherent efficiency and Power to Weight advantage. There is a heavy competition among the manufacturers to capture the market with their best products. Baker Hughes has many products in this segment with a range of output levels.
The Gas Turbine Rear Frame (TRF) is a structural member, which supports the Gas Turbine casings at the rear end and transfers the load to the base plate or ground. It also houses the last bearing on which the power turbine rotor is supported. Also, this component experiences hot gases on the mainstream side and relatively colder air on the cooling path. It has many non axi-symmetric features which makes the design of this component very challenging.
This paper describes the approach used to improve the thermal prediction of the TRF, Rotor Aft Wheel Cavity and vent air cavity region, which is critical to understand the mechanical behavior of the component and assess the component life. Quasi-3D flow analysis is used to understand the flow structures in the cavities and simulated those flow structures in the 2D thermal models which improved the model prediction, and which is also validated with test data.
Unsteady Flow Mechanism of Impeller Stall Inception in a High-Pressure Ratio Centrifugal Compressor With Bleed Slots
Authors: Fujisawa Nobumichi , Yamamoto Yuta , Ohta Yutaka , Ogino Atsushi , Nakayama Ryo , Kitamura Eijiro 
Published: August 2024

Abstract
The impeller stall inception in a high-pressure ratio centrifugal compressor with bleed slots was investigated by the experiments and unsteady numerical analysis. This study reported that the flow instability of the internal flow was first initiated around the leading edge of the splitter blades and finally resulted in tip-leakage flow instability at the leading edge of the main blades. The impeller stall consisted of a stall cell and rotated about 70% of the impeller rotational speed. Furthermore, a pressure disturbance occurs at the splitter blade leading edge before the main blade leading edge. The blockage within the passage of the suction side at the leading edge of the splitter blade was first increased because the leading-edge separation on the suction surface of the splitter blade was enlarged. The blockage within the passage of the pressure side was increased after that of the suction side stopped increasing. Therefore, the blockage development of both pressure and suction passage at the leading edge of the splitter blade was the main cause of the stall inception. Then, a longitudinal vortex was formed near the bleed slots and blocked the mainstream near tip side. Subsequently, the reverse flow region in the inducer was developed and extended to the impeller inlet. Finally, the flow angle to the main blade increased, the spillage occurred at a leading edge of a main blade, and the rotating stall was generated. The cause of impeller instability was the separation of the suction surface of splitter blade and the formation of a stagnation region on the pressure surface at the splitter leading edge.
100% H2 DLE Gas Turbine Combustion Technology Platform Development
Authors: Hermeth Sebastian , Panek Lukasz , Witzel Benjamin , Grandt Christopher , Koestlin Berthold , Wanjura Stefan , Teuber Hannes , Parsania Nishant , Sadasivuni Suresh , Bulat Ghenadie , Yilmaz Ertan , Koenig Mike 
Published: August 2024

Abstract
Siemens Energy is developing the required technologies to operate its gas turbines up to 100% H2 by 2030 to support the target of limiting global warming to 1.5 degrees Celsius. A focused effort has been undertaken to develop a combustion system technology platform for the complete Siemens Energy gas turbine portfolio which will enable gas turbine operation across the entire range of H2/natural gas blends within emissions compliance and hardware integrity.
This paper presents an update of Siemens Energy’s 100% Hydrogen DLE Gas Turbine Combustion Technology Platform Development presented at the 2022 ASME Turbo Expo [20]. While the 2022 paper showed initial rig test results at scaled pressure, the update includes new results from rig testing at full pressure, a summary of results from SGT-400 full engine tests conducted on natural gas at the Siemens Energy factory in Lincoln (UK), and SGT-400 full engine tests with various levels of hydrogen up to 100% at a customer site in Saillat-Sur-Vienne (France) as part of the HYFLEXPOWER project. An engine safe operation envelope with respect to flashback will be presented and engine data will be compared against rig test data obtained at Clean Energy Center at relevant engine conditions. Siemens Energy actively researches and develops methods to investigate hydrogen embrittlement effects in metallic materials, particularly those applied in gas turbines. Through extensive testing of base materials and their joint connections, Siemens Energy aims to improve understanding of hydrogen’s effects on materials and optimize gas turbine components’ lifespan. The current state of development in this regard is presented here. Finally, the paper will provide an outlook on the scaling of the demonstrated hydrogen technology to Siemens Energy’s gas turbine portfolio.
Steam Whirl Detection and Correction in 135 MW Steam Turbine
Authors: Chumai Roengchai , Lertsongkram Pisut , Koondilogpiboon Nuntaphong 
Published: August 2024

Abstract
Steam whirl is the self-excited vibration that causes the rotor of a steam turbine to whirl at its first critical speed. It is caused by the combination of steam excitation (in blade rows and steam glands) and low damping of the journal bearings. Steam whirl usually occurs in the high-pressure rotor at high power output where the steam pressure and flow rate are high. The occurrence of the steam whirl prevents maximum power operation. The steam whirl can be rectified by bearing/seal modifications.
A case study was presented on the remote startup support service for a 135 MW steam turbine and generator after a major overhaul. The vibration amplitudes measured at high-intermediate pressure (HP/IP) rotor fluctuated due to subsynchronous vibration frequency when the unit was operated at over 103 MW. Furthermore, the amplitudes significantly increased as the load was further increased and the unit tripped at 134 MW due to the excessive vibration amplitudes at bearing 2. The unit was then restarted and the maximum output was limited to around 103 MW until the following outage where both bearings of the rotor were replaced with the tighter clearance ones and the alignment between bearing 1 and the main oil pump was done. The subsequent startup showed acceptable and stable vibration amplitudes of the HP/IP rotor during baseload operation.
Model-Driven Optimization for the Conceptual Design of Aeroengine Turbine Flow Path
Authors: Chen Yifan , Chen Jinwei , Zhang Huisheng 
Published: August 2024

Abstract
In the conceptual design process of aeroengines, the thermal parameters and the fundamental structure must be determined. To reduce iterative adjustments between the conceptual and detailed design, it is necessary to obtain a method that can meet the performance requirements quickly and accurately. At the same time, considering the different methods of subject-level modeling, a tool is needed to support the data interaction of the analysis model. Therefore, an optimization approach combining multidisciplinary design optimization (MDO) and model-based systems engineering (MBSE) is proposed for conceptual design. Taking turbine flow path as the research object, a MBSE-MDO framework for overall design is proposed. First, a Requirements, Functional, Logical, Physical (RFLP) modeling procedure is applied in this study to implement the entire design process from requirements to system architecture. Based on semantic modeling technology, the automatic transformation of the knowledge representation of the model is realized. Then, relying on the consistency and scalability provided by semantic modeling, MDO is performed. With fuel consumption, weight, and noise as the system-level optimization objectives, aerodynamics, heat, and structural strength are considered as disciplinary constraints. The main cycle parameters for specific scenarios and requirements are obtained. Finally, validation at the early stage of the design is performed to ensure that the design meets the defined requirements. The accuracy of the overall design results is verified based on the existing engine data. The average error of the design parameters is 1.55% and the maximum error is 3.02%. It indicates that the design method proposed in the paper meets the accuracy requirements for engine-related parameters in the overall design phase. The method proposed in this study is expected to rapidly and accurately obtain design parameters that meet the performance requirements, thereby reducing the development cycle of the turbine flow path. Based on the optimization of turbine flow path in this paper, the optimization design of other components can be further carried out to realize the overall optimization, laying a technical foundation for the overall multidisciplinary optimization design.