Ansaldo Energia

This work presents an experimental investigation of heat transfer and pressure loss in high-aspect-ratio nominally rectangular channels with a single ribbed wall, representative of wall-integrated turbine blade cooling. In such designs, separate cooling passages lie directly beneath the blade's pressure and suction surfaces, so only the wall facing the hot gas path requires enhancement. Despite their relevance, systematic data for high-aspect-ratio, single-sided ribbed multi-pass channels at engine-relevant conditions remain limited. A three-pass test section with two 180 degrees turns was tested with air for Reynolds numbers up to 100,000. Three aspect ratios (AR = 3.7, 5.0, 7.5), three rib geometries (V-, W-, and staggered V-ribs), and three guide-vane designs (180 degrees, 135 degrees, and 90 degrees spans) were examined. Surface heat transfer was measured using transient liquid crystal thermography, and pressure drops were recorded in each passage and bend. Increasing aspect ratio leads to a systematic increase in area-averaged heat transfer, accompanied by a corresponding rise in pressure loss, highlighting a clear thermal-hydraulic trade-off. Among the investigated rib configurations, W-ribs generally exhibit higher and more uniform heat-transfer levels, while staggered V-ribs produce lower augmentation with reduced friction penalties; however, differences among rib types remain moderate. Guide-vane design strongly affects bend losses and downstream uniformity, with the 180 degrees vane providing the most favorable balance. Semi-empirical roughness functions for friction and heat transfer are derived and shown to predict the measurements consistently across all tested configurations, with mean absolute percentage errors below similar to 10% for friction and similar to 15% for heat transfer, providing a generalized framework for performance prediction in high-aspect-ratio single-wall ribbed channels.

Modern power grids are increasingly dominated by power-electronic interfaces and inverter-based resources, while the contribution of synchronous machines is declining. Together with the rapid growth of large converter-connected loads (e.g., data centres and electrolyser plants), this transition can reduce fault strength, worsen voltage quality, and challenge frequency stability when demand is not easily controllable. Synchronous Condensers offer proven support by providing voltage regulation, reactive power, short-circuit contribution, and rotational inertia. This work proposes a hybrid plant that couples a flywheel-equipped Synchronous Condenser with a Battery Energy Storage System (BESS) operated through a grid-forming inverter and coordinated by a plant-integrator controller. The Synchronous Condenser supplies stored inertia to damp frequency deviations and reduce ROCOF, while the BESS shifts renewable energy and delivers fast active-power response. Coordinated control enables grid services such as frequency and voltage control, power-factor support, dynamic reactive-power regulation, and black-start capability. An economic assessment for a German deployment context, where renewable penetration is high, and an inertia market started in 2026 (momentanreserve), suggests improved business cases through shared balance-of-plant components, lower CAPEX, and diversified ancillary-service revenues, supporting bankability during the energy transition.

With the growing integration of Renewable Energy Sources (RES) and High-Voltage Direct Current (HVDC) lines, maintaining grid stability has become increasingly complex. RES, being non-programmable, introduces fluctuations in voltage and frequency, while HVDC lines affect grid dynamics. Synchronous Condensers (SynConds) offer a robust , reliable and cost-effective solution by providing reactive power, voltage regulation, short-circuit power, and inertia. Built from standard turbogenerators and remotely controlled, SynConds deliver rapid dynamic response and can include flywheels to boost inertia with minimal energy and noise impact. Ansaldo Energia has been a pioneer in this field, starting with its first SynCond plant at Terna’s Codrongianos substation in Sardinia in 2014. Since then, it has developed multiple plants across Italy, particularly in Central and Southern regions where RES penetration is highest. The company also repurposes components from decommissioned coal and gas plants to create new SynConds, exemplified by a recent project in Southern Italy. As grid codes and market structures evolve, hybrid systems combining RES and thermal generation with SynCond capabilities offer new opportunities for grid balancing services. With global energy systems shifting toward renewables, the demand for SynConds is set to rise, ensuring reliable and stable power networks for the future.

This study presents the dynamic characterization of a gas turbine blade manufactured from two different nickel-based superalloys: on the first hand, a superalloy called René 80 and, on the second hand, a directionally solidified (DS) nickel-based anisotropic superalloy, investigated during the validation phase of the development process. Starting from the original CAD geometry, precise and very detailed finite-element models were developed, progressively refined and modified, and consequently validated to ensure mesh-independent modal predictions. The study examines multiple possible sources of discrepancy between experimentally measured and numerically predicted natural frequencies, including geometric deviations, grouping of different interesting points, broach-block test configuration, material anisotropy, and the influence of internal rib turbulators. Statistical analyses of dimensional variations revealed no significant correlation with the observed frequency scatter, redirecting the investigation toward material behavior and modeling fidelity. The inclusion of turbulators in the finite-element model proved essential, reducing prediction errors for the first two modes by approximately 2-3%. For the DS superalloy, the effect of grain orientation was evaluated over permissible angular deviations (extremes were considered); however, no systematic and clear improvement in frequency prediction was observed. Finally, several tuning strategies were assessed, leading to an optimization procedure that simultaneously adjusted the elastic moduli Ex and Ez, reducing modal frequency deviations to below 1% for the first two modes. The proposed methodology provides a robust and solid framework for the validation of turbine blade dynamic behavior across different materials and manufacturing conditions.

The design and safety assessment of innovative nuclear systems such as MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) require dedicated experimental facilities able to reproduce and investigate the complex thermal-hydraulic behaviour of key components. Among them, the Primary Heat eXchanger (PHX) plays a central role in the reactor's primary cooling system, ensuring effective heat removal under both nominal and transient conditions. To this end, the HEXACOM facility was conceived as a scaled experimental loop reproducing the thermal-hydraulic behaviour of the PHX under representative operating conditions. This paper presents the results of a comprehensive experimental campaign carried out on HEXACOM operated in Stand-Alone Open Loop mode, aimed at characterizing the system's steady-state and transient performance. The experimental activities were designed to provide high-quality data for code validation and to enhance the understanding of the coupled dynamics between primary, intermediate, and secondary cooling circuits. In parallel, a detailed system thermal-hydraulic (STH) model of the HEXACOM loop was developed using the RELAP5 code. To ensure reliability, stand-alone models of the main components-such as valves, the pump, and the PHX-were first implemented and validated against nominal data. These efforts ensured that the most influential components were represented with sufficient accuracy before their integration into the complete facility model. A post-test analysis was then performed by comparing RELAP5 simulation results with experimental data obtained from the HEXACOM test campaign. The comparison demonstrated a satisfactory agreement in terms of pressure, flow distribution, and heat transfer behaviour, confirming the model's predictive capability. On this basis, the RELAP5 model can be considered validated and reliable for further applications. Finally, a pretest analysis was conducted for a specific operating configuration whose experimental results are not yet available. This predictive study provides useful insights for the planning and interpretation of future experiments and supports the broader objective of validating the PHX thermal-hydraulic behaviour in MYRRHA.