Flow-induced vibrations of rigid prisms supported elastically were studied experimentally in a free-surface water channel with a high blockage (2/5). The study focused on finding the prism cross-sectional shape that maximizes the efficiency of energy harvesting. Seven cross-sectional shapes were tested: square, circular, 45° tilted square, equilateral triangle, isosceles 120° triangle, D-section, and C-section. All other dimensionless parameters of the problem, mass ratio, damping, blockage ratio, reduced velocity range, and the Reynolds (Re) number (characteristic velocity times characteristic length divided by kinematic viscosity) range (400–1070), were kept unchanged. By doing so, the effect of the cross-sectional shape was isolated. D-section proved to be the geometry with the highest values of energy transfer efficiency. A hysteresis loop was present in its oscillatory response (dimensionless oscillation amplitude vs reduced velocity). This loop was characterized by two branches, (+) and (−), meaning a bi-valued amplitude response for each reduced velocity. Regarding temporal patterns of wake topology and body motion, it was found that synchronization occurs in the (+) branch, but not in the (−). Regarding vortex shedding modes, particle image velocimetry was used for identification purposes, and it was found that the 2P mode is the dominant mode in the (+) branch, while the 2S mode pervades the (−). Finally, a new relative reduced velocity definition was introduced, and, when re-plotting the experimental results, it was found that the hysteresis loop disappears, thereby providing a more compact mathematical description of the observed phenomena.

With the recent drive towards higher thermal efficiencies and lower emission levels in the power generation market, advanced cycle power plants have become an increasingly appealing option. Among these systems, humid air turbines have been previously identified as promising candidates to deliver high efficiency and power output with notably low overall system volume, weight and emissions footprint. This paper investigates the performance of an advanced humid air turbine power cycle and aims to identify the dependencies between key cycle design variables, thermal performance, weight and cost by means of a parametric design optimization approach. Designs of the main heat exchangers are generated, aiming to ascertain the relationship between their technology level and the total weight and acquisition cost of them. The research outcomes show that the recuperator and the intercooler are the two components with the largest influence on the thermal efficiency and the total cost. The total weight of the power system is driven by the technology level of the recuperator and the economizer. Finally, the effectiveness of the aftercooler seems to have the greatest impact in reducing the total acquisition cost of the system with minimum penalty on its thermal efficiency.

A new gradient-like methodology has been developed for aeroengine diagnosis, determining the engine health condition, which is defined by the engine degradation from an undegraded state and uses measurements at various sensors distributed along the engine. The developed tools are able to accurately compute, not only the engine degradation, but also the turbine inlet temperature, which is very important and novel in the field. The quality of a given sensors set is evaluated, and a method is developed to guide in the improvement of deficient sensors sets. The methodology is tested in a representative two-spool turbofan engine, obtaining consistent results in a computationally inexpensive way. Moreover, results are robust in connection with the random noise added to the sensors data.

Purpose: This work presents a methodology for the conceptual aerodynamic design of rotating detonation engines (RDEs). The purpose of this paper is to assist feasibility studies and to help in the planning of experimental campaigns. Design/methodology/approach: The methodology is based on a surrogate data-driven physics-aware model. Simplified CFD is used to generate a data-tensor-form surrogate model of the RDE. Then, the surrogate model feeds an algorithm that solves the direct problem (prediction) and the inverse problem (multi-parameter design) of the RDE. The direct problem inputs are both operational and geometric RDE parameters. Outputs are performance parameters. The inverse design problem computes operational and geometrical parameters from prescribed performance parameters. Findings: The main practical finding is that the use of surrogate model-based data-driven techniques helps to increase the fidelity level of aerodynamic conceptual design tools for RDE. Originality/value: Traditionally, conceptual design studies of RDE have been carried out using thermodynamic path analysis in different forms. In this work, a methodological step ahead, which incorporates CFD simulations from the onset, is proposed. This was achieved by making use of a surrogate model approach. The main value of the proposed methodology is that it allows for extensive parametric studies with limited computational cost.

Nowadays, there is an ever growing interest for gas turbine and aeroengines prognostics. The capability to assess not only the current state of an asset, but also to be able to predict its remaining useful life (RUL), and hence to perform condition-based maintenance (CBM) —if, and only when, it is needed— can represent a huge deal in the manufacturer profits. Against the plethora of data-driven methods that have arisen in the past few years, there is still some knowledge to be gained in terms of understanding the underlying phenomenology of engine degradation. In fact, it is certainly a non-trivial problem, to realize what has happened to the rotating components of an engine just by observing the pressure being measured by certain sensor rise, or some other temperature measured along the main gas-path decrease its value. In this regard, model-based approaches —and, in particular, gas path analysis (GPA)— can assist us in gaining such knowledge. In this paper, a non-linear GPA technique is revisited, introducing some novelties to the solver, and making use of current computational methods and resources, to establish a solid ‘foundation’ that will serve as the basis for further research.