Search Results (398)

During hot deformation of GH4706 alloy forgings, to achieve effective control over the uniformity of its microstructure, it is first necessary to establish a quantitative relationship between the microstructural characteristics of an entire hot-formed turbine disk forging and process parameters using reliable methods. Based on hot compression test results of GH4706 alloy at temperatures ranging from 950 °C to 1150 °C and strain rates from 0.001 s⁻¹ to 1 s⁻¹, this study developed a microstructure evolution model. Multi-scale high-precision numerical simulations were performed to predict the parameter field distribution and microstructure distribution of the turbine disk. The results reveal that the inhomogeneity of strain distribution is the primary cause of mixed grain formation. Statistical comparisons between simulation predictions at six validation points and industrial experimental data revealed the following relative deviations: 5.21% for average grain size (AVG), 9.65% for the standard deviation of grain size distribution (SD), and 5.31% for DRX fraction. Additionally, the standard deviations of prediction error for these three parameters are 3.26% for AVG, 4.06% for SD, and 3.12% for DRX fraction. These results demonstrate that the multi-scale dynamic recrystallization model developed in this study exhibits satisfactory prediction accuracy and stability. The modeling approach presented in this paper is of great significance for precisely controlling the uniformity of microstructural distribution during the hot deformation of GH4706 alloy. Full article

Dedicated platforms for floating vertical-axis wind turbines (VAWTs) require an in-depth understanding of their strongly unsteady coupled dynamics, yet the effects of platform configuration on motion stability, aerodynamic loading, and wake recovery remain insufficiently clarified. This study develops a high-fidelity aero-hydro-mooring coupled framework base on computational fluid dynamics (CFD) to compare Φ-type floating VAWTs supported by semi-submersible and spar platforms under identical wind–wave excitation. The results show that the semi-submersible configuration, owing to its larger structural scale near the free surface, experiences stronger wave interaction and more pronounced wave-frequency heave, surge, and pitch responses. The spar configuration reduces wave-frequency hydrodynamic excitation because of its deep-draft slender structure, but it is more prone to mean pitch offset and sway–roll–yaw coupling. Mooring responses are governed by mean surge drift, mean pitch inclination, and wave-frequency motions, with the semi-submersible system exhibiting stronger tension fluctuations and the spar system showing a more uneven load distribution among the mooring lines. Under the examined wind–wave condition, the spar configuration exhibits larger fluctuations in instantaneous power, thrust and single-blade torque than the semi-submersible configuration. Wake analysis indicates that the semi-submersible system maintains stronger wake coherence, while the spar system enhances vortex breakdown, turbulent mixing, and velocity-deficit recovery. These findings support platform selection, load control, and array layout optimization for floating VAWTs. Full article

When methane (natural gas) fuel gas turbines switch to hydrogen–ammonia co-fuel, their thermodynamic performance undergoes significant changes. To expand the operating range of heavy-duty gas turbines when using hydrogen–ammonia co-fuel and to improve their thermodynamic performance, based on the 255.6 MW heavy-duty gas turbine at the Banshan Power Plant in Hangzhou, China, a simulation model was established. A strategy based on changing the angle of the compressor inlet guide vanes (IGVs) was proposed. The thermodynamic performance, turbine stage supercritical flow velocity, and flow matching characteristics of gas turbines were studied under different hydrogen–ammonia mixing ratios. The results indicate that the developed model can accurately predict the performance of the gas turbine under rated operating conditions, yielding a rated output power of 254.59 MW and an efficiency of 36.33%, with relative errors of −0.4% and −1.54% compared with the design values, respectively. When hydrogen–ammonia blended fuel is employed, the outlet Mach numbers of the second- and third-stage turbine stators exceed the safety limit unity. Reducing the IGV angle effectively decreases the turbine stator outlet Mach number and improves operational safety, although a slight reduction in gas turbine efficiency is observed. As the ammonia volumetric fraction in the blended fuel increases, the gas turbine output power increases while the efficiency decreases slightly, accompanied by a reduction in turbine stator outlet pressure and an increase in outlet temperature. Further investigation shows that, after IGV regulation, the combustor outlet pressure, gas turbine power output, and efficiency all increase. Under a fixed IGV opening condition, the gas turbine efficiency gradually decreases with increasing ammonia volumetric fraction. Under off-design fuel flow conditions, increasing the relative fuel flow leads to higher combustor outlet pressure and temperature, whereas increasing the ammonia volumetric fraction causes a slight reduction in these parameters. This research can provide theoretical support for the optimal design and operation of gas turbines using hydrogen–ammonia mixed fuel. Full article

The study presents an application of virtual prototyping and numerical analysis in engineering practice for an in-stream hydropower system. The performed analyses aimed to compare different design configurations of the crossflow turbine. All simulations use virtual prototypes and computational fluid dynamics to review design performance in detail under various environmental conditions. Specifics of mixed fluid flows are outlined. The major focus is on virtual prototype testing, aiming to demonstrate its ability to deliver fast results for complex, expensive structures. This work is a good example of the practical application of numerical analysis and virtual prototyping and demonstrates a specific, complex field, such as computational fluid dynamics. Full article

This study investigates heat transfer enhancement in the cooling channels of gas turbine blade turbulators using modified transverse baffles with isosceles triangular sawtooth perforations. The proposed baffle design aims to improve convective heat transfer by promoting flow mixing and disrupting the thermal boundary layer. Experiments were conducted in a rectangular channel with an aspect ratio of 3.75 under constant heat flux conditions using air (Pr = 0.7) as the working fluid. The effects of Reynolds number (Re = 6000–24,000), sawtooth width ratio (a/W = 0.0, 0.0625, 0.125, 0.25, and 0.5), and sawtooth height ratio (b/e = 0.0, 0.25, 0.5, 0.75, and 1.0) were systematically investigated. The blockage ratio (e/H) and pitch ratio (P/H) were maintained at 0.3 and 1.5, respectively. Heat transfer characteristics were evaluated using the thermochromic liquid crystal (TLC) technique, while thermal–hydraulic performance was assessed in terms of the Nusselt number (Nu), friction factor (f), and thermal performance factor (TPF). The results demonstrate that introducing sawtooth perforations significantly enhances heat transfer compared with a smooth channel, yielding Nusselt number ratios (Nu/Nu_s) between 1.6 and 2.6. The highest heat transfer enhancement was achieved at a/W = 0.0625 and b/e = 0.25, where the relatively small sawtooth openings generated stronger jet impingement, enhanced flow mixing, and more effective disruption of the thermal boundary layer. However, these geometric modifications also increased the pressure loss due to intensified flow blockage and recirculation, resulting in friction factor ratios (f/f_s) ranging from 8.9 to 14.9. The maximum pressure-drop penalty occurred at b/e = 0.25 because the smaller openings produced stronger turbulence and increased flow resistance. Despite the increased friction loss, the optimum configuration (a/W = 0.0625 and b/e = 0.25) achieved the highest thermal performance factor of 1.2 at Re = 6000. Full article

Pressure management in water distribution networks requires the integration of hydraulic modeling and discrete device allocation, naturally leading to mixed-integer nonlinear programming (MINLP) formulations. This study presents a MINLP problem for the joint placement of pressure-reducing valves and pumps as turbines, using the Global Excess Power index to quantify energy inefficiencies related to excess pressure and leakage. The formulation incorporates nonlinear hydraulic equations, leakage–pressure relationships, and operational constraints. Application to a real network illustrates model behavior and highlights the computational challenges associated with energy-oriented pressure control in practical water distribution systems. Full article

Pumped-storage hydropower requires pump-turbines to operate safely and efficiently under off-design conditions, where stall-induced unsteady flows can redistribute hydraulic losses and reduce operational stability. Unlike previous analyses focused mainly on spatial correlations, this study develops a spatiotemporal framework to clarify how hydraulic loss (HL) and vortex evolution (VE) co-vary under different stall states at the valley point of the pump-mode hump region in a low-specific-speed, ultra-high-head pump-turbine. Detached eddy simulations (DES) were performed for an original-runner scheme (ORI) and an optimized-runner scheme (OPT), with identical stationary components, boundary conditions, and numerical settings. The comparative cases cover four representative flow states: non-stall, fixed stall, rotating stall, and mixed stall. The local hydraulic-loss rate (LHLR) was decomposed into dissipation (DIS) and transport (TRANS) terms, and Liutex-based vorticity decomposition was used to distinguish shear- and rigid-rotation-related vortex quantities. Pearson correlation analysis was then applied in both space and time. The results show that DIS is consistently associated with shear enstrophy ${\Omega }_{\mathrm{S}}$, whereas the spatiotemporal correlation associated with TRANS and VE parameters exhibits stronger regional and stall-state dependence. These findings provide a quantitative basis for identifying loss-sensitive vortex features and support flow-control and runner-optimization strategies for improving pump-turbine efficiency and stability. Full article

Pumped hydro storage remains one of the most established technologies for balancing supply and demand in electricity markets with high shares of renewable energy. This paper investigates the short-term economic optimization of a pumped hydro storage plant operating under real day-ahead market conditions. A Mixed-Integer Linear Programming model is used to optimize hourly dispatch decisions based on actual day-ahead electricity prices in Slovenia for the year 2024. The model accounts for technical constraints, including turbine and pump capacities, round-trip efficiency, energy storage limits, and restricted startup frequencies. The simulation results show that pumped hydro storage can achieve a positive market-based operating result by responding effectively to price volatility and frequent negative pricing events. Seasonal variations reveal higher revenues during summer months due to solar overproduction. The findings confirm the potential of pumped hydro storage to enhance grid flexibility and support the implementation of national energy transition objectives. By linking large-scale energy storage operations with renewable energy integration, grid flexibility, and market-based dispatch, the study also contributes to the technical and economic dimensions of sustainable energy system development. Full article

Robust flame stabilization in low-Mach, low-enthalpy supersonic combustors is a core bottleneck for turbine-based combined cycle (TBCC) mode transition. Existing studies mainly focus on single-injector configurations, while the injection angle modulation mechanism for multi-injector cavity flameholders remains unclear under TBCC-relevant conditions. This work experimentally investigated the effects of 30°, 45°, and 90° injection angles on cold-flow mixing, reacting flow topology, and flame stabilization in a Mach 1.6, 660 K dual-injector cavity combustor. Results showed that the overall cold-flow jet penetration capacity in the fully developed far field increased with injection angle following the order of 90° > 45° > 30°. Combustion heat release universally enhanced jet penetration, with a maximum 25% augmentation observed at 30° injection, which attenuated with steepening injection angle. Moreover, flame stability exhibited a non-monotonic trend in the tested dual-injector configuration. Full article

The control of micro energy grids (MEGs) is characterized by volatility, uncertainty, and decentralization. Traditional power distribution algorithms, designed for centralized, dispatchable generators, are inadequate for MEG environments. Controllable load management provides peak shaving, load balancing, frequency regulation, and voltage stability, as well as fast balancing services for renewable energy grids in distributed power systems. A non-grid-tied inverter costs a fraction of its grid-tied counterpart for the same capacity. In the initial setting, one or more inverters are used. As the demand grows, more non-grid-tied inverters are added to the mix. Non-grid-tied inverters cannot be connected in parallel. There is no practical solution available in the market for the optimum utilization of this type of setting. Unlike a grid-tied microgrid, in non-grid-tied mode, a microgrid uses grid power only when needed, prioritizing renewable sources. This paper explores autonomous strategies for controlling and coordinating multiple renewable energy sources in MEG settings. It reviews and develops an algorithmic framework for optimal load distribution among multiple renewable sources, including solar photovoltaic (PV), wind turbines, and battery energy storage systems (BESSs). The proposed framework integrates resource forecasting, multi-objective optimization, and adaptive supervisory control to ensure stability, maximize renewable penetration, and minimize operational costs. Performance considerations, mathematical modelling, and potential implementation architectures are discussed. A hybrid approach, combining multiple algorithms, is therefore proposed. In this paper a real-life solution is proposed to a real-life problem. Full article

Energy plays an essential role in economic advancement for any nation. However, escalating worldwide energy demands coupled with environmental and climate change issues resulting from the excessive consumption of conventional energy sources highlight the importance of identifying sustainable energy resource alternatives. Jordan, with its very limited fossil-fuel resources, is actively expanding its energy mix by investing in renewable sources, particularly wind energy. Therefore, the current work provides an evaluation of the wind power potential of Gharandal town within Tafila governorate, in southern Jordan, using hourly wind data recorded at 90 m elevation within a one-year monitoring period. The investigation reveals that the Weibull distribution more accurately models the wind speed in Tafila compared to the Rayleigh distribution based on parameters estimated through the maximum likelihood approach. The investigation at 90 m also shows that the annual wind power is 296 W/m², indicating that Tafila has marginal suitability for wind potential (Class 2) under the Pacific Northwest Laboratory classification system and has fairly good and suitable conditions for installing a wind farm per the European Wind Energy Association classification system. Most of the time, the prevailing winds at Tafila originate from the west direction (i.e., 270°), accounting for 23% of all occurrences. Finaly, the Tafila region contains promising areas for wind energy generation, particularly with the implementation of modern wind turbine technologies. Full article

Background: Inferior turbinate hypertrophy is a major cause of chronic nasal obstruction and can be treated with several surgical techniques. However, current surgical decision-making is often not personalized to the dominant anatomical and functional substrate of obstruction. No widely adopted structural classification of the inferior turbinate exists, and no standardized algorithm links individual anatomical phenotypes to targeted surgical strategies. Methods: A structured narrative review of PubMed and Scopus was performed from database inception to 1 February 2026, using predefined search terms and eligibility criteria. Studies were selected if they addressed inferior turbinate anatomy, histopathology, imaging morphology, endoscopic grading, nasal valve or septal anatomy, surgical techniques, postoperative outcomes, complications, or patient-reported outcomes. Randomized and prospective trials, histopathological studies, CT morphometric analyses, and validated endoscopic grading systems were considered. Four phenotypes of inferior turbinate hypertrophy were identified and linked to preferred surgical options within a clinically oriented decision algorithm integrating endoscopy, functional testing, and selective CT imaging. This framework was developed to support individualized treatment planning and shared decision-making. Results: Four structural phenotypes were defined: (i) predominantly cavernous/mucosal hypertrophy; (ii) predominantly bony hypertrophy; (iii) anterior nasal valve-turbinate conflict; and (iv) mixed hypertrophy. For mucosal-dominant disease, radiofrequency ablation and laser turbinoplasty are preferred first-line, mucosa-preserving options. For bony hypertrophy, mucosa-preserving powered inferior turbinoplasty is favored for the mid/posterior turbinate, whereas endoscopic pyriform aperture turbinoplasty is preferred for anterior valve-level conflict. Mixed phenotypes are best managed with combined skeletal and mucosal procedures. The algorithm aims to avoid mismatched treatments, such as mucosal-only techniques for rigid bony hypertrophy or extensive skeletal reduction in purely mucosal disease. Perioperative variables relevant to shared decision-making, including type of anesthesia, postoperative morbidity, recovery profile, and expected limitations, were summarized for each technique. Conclusions: This phenotype-guided algorithm provides a structured, evidence-informed framework for the personalized selection of inferior turbinate surgery, emphasizing mucosal preservation, anatomical specificity, patient-centered decision-making, and avoidance of mismatched procedures. It is intended to support, not replace, clinical judgment and to guide future prospective validation studies in personalized rhinologic surgery. Full article

While gas-turbine combustors have received much research attention, the forced response of large atmospheric industrial flames is much less studied. To improve the understanding of thermoacoustic instabilities in industrial combustion systems, the forced response of a large natural-gas fired test furnace is computed using Scale-Adaptive Simulations (SASs) with a Flamelet Generated Manifold model. Two test burner configurations are compared. One produces a partially premixed flame (case P) and the other a non-premixed flame. Furthermore, the non-premixed configuration is simulated at both a slightly rich (case N) and a slightly lean set point (case NL). The flame is forced by perturbing the airflow using a superposition of sine waves at four discrete frequencies. That way, the gain and phase of the Flame Transfer Function (FTF) are determined in three simulations for a total of 12 discrete frequencies between 10 and 230 Hz. The results show very different behaviour of the partially premixed and non-premixed configurations. Case P is simulated to be a compact flame, with a maximum FTF gain of one around 70–80 Hz and a quasi-steady limit of 0.7. Case N and NL are characterised by slightly lifted flames acting as low-pass filters that quickly drop off towards higher frequencies. While the phase shift in case P is linearly dependent on frequency and can be related to its flame length, the non-premixed cases have a sharp initial phase shift that levels off with increasing frequency as the gain reduces to zero. Importantly, a non-zero phase shift at 0 Hz is observed for case NL. The nature of the combustion dynamics is further explored by a Proper Orthogonal Decomposition (POD) analysis. The FTFs are applied to predict the thermoacoustic stability using an Acoustic Network Model (ANM). This model is able to reproduce the stability of the cases observed in experiments. The results presented in this study provide insight on the effect of mixing and stoichiometry on the stability of large industrial furnaces. Full article

Tidal energy assessment in tropical estuaries is constrained by low current velocities and high spatial variability, which limit conventional evaluation approaches. This study proposes a methodological framework adapted to velocity-constrained environments. The framework integrates ADCP-calibrated hydrodynamic modeling, velocity-exceedance-based site selection, low cut-in tidal turbine compatibility analysis, and a localized Levelized Cost of Energy evaluation within a unified decision-support structure. The methodology is applied to Buenaventura Bay, Colombia, where numerical simulations reproduce the mixed tidal regime with errors of approximately 0.30 m in water levels and 0.022 m/s in current velocities, enabling consistent characterization under low-flow conditions. Results at three locations indicate average available power densities of 64 W/m² at La Bocana, 19 W/m² at Buoy 29, and negligible values at Aguadulce, supporting the identification of marginal and non-viable sites based on velocity distributions. Under a low-velocity turbine configuration (10 m rotor diameter, 0.4 m/s cut-in speed), annual energy production is about 18 MWh per unit, while a 300-turbine array would generate approximately 5.4 GWh per year. The results indicate that annual energy production and capital expenditure are the main drivers of techno-economic feasibility in low-energy estuarine systems. Full article

Wake interactions between wind turbines have a significant impact on the performance of downstream turbines and the overall efficiency of wind farms. In this study, wind tunnel experiments were carried out to investigate the wake characteristics of multiple wind turbines under different inflow conditions, upstream yaw angles, and turbine arrangements. The applicability of a previously proposed blade optimization method for reduced-scale wind turbine wake experiments was further assessed, and several wake velocity superposition models were evaluated. The results indicate that inflow turbulence intensity has a greater influence on wake recovery than inflow velocity and that increased turbulence intensity accelerates wake mixing and velocity recovery. Moreover, an appropriate upstream yaw angle and a staggered turbine arrangement can alleviate the wake deficit experienced by the downstream turbine. Additionally, the experimental data confirm that the optimized blade design method is effective for multi-turbine wake experiments. Among the models considered, the geometric sum model shows the best agreement with the experimental data under non-yaw conditions with small turbine spacing. The present study provides useful reference data for wind farm layout optimization and wake model development. Full article