1,721,649 research outputs found
Some Considerations about the Rotating Cell Structure
No full textRotating stall instability in axial flow compressors arises when the mass flow is reduced at constant rotational speed. Despite the number of experimental and theoretical work already published in the scientific literature, many questions still remain unanswered. A complete model that could be of help both in the design process and in the modelling process of existing engines is not yet available. A fundamental research program has been carried out at the Department of Mechanical Engineering of Cagliari with the scope of reaching a better understanding of the basic flow structures and of the global performance in stall. The cinematic structure of the cell during abrupt full 1-cell stall in a two-stage axial flow compressor with IGV, has been analysed with the aid of hot-wire anemometer and of a total pressure probe. The results have revealed interesting features about the cell flow structures and their variations along the stalled performance branch of the compressor. The present work aims at pursuing further the flow analysis including the investigation of upstream flow field. Therefore, the inlet duct has been extended to perform the measurements The complete flow field measurements will allow to obtain a complete cinematic description of the cell
Development and implementation of a 3D numerical code for designing and predicting performances of PCM thermal energy storage systems
No full textThe present work is focused on the development of thermal energy storage systems (TES) based on phase changing materials (PCM), to be used as back-up devices during transient operations of small and medium scale concentrated solar plants (CSP). The development of the storage device will be performed recurring to numerical simulation and experimental testing in the laboratory.
At the current stage the laboratory is being built, while the implementation of a numerical tool to simulate the behaviour of tanks with different geometries and different working materials has started.
The preliminary development of the storage device is carried out by means of a 3D numerical simulation code specifically implemented in the COMSOL Multiphysics environment. The code is used to solve direct (design) and indirect (analysis) problems considering heat storage tanks with different geometries and different working materials. The geometry chosen for this preliminary analysis is the shell and tube heat exchanger, whose shell is filled with PCM and the working fluid flows on the tube side (up to 200-220°C to simulate the heat transfer fluid from the solar field). The system is designed for a heat storage capacity of 36 MJ
Distinguishing between dark-matter interactions with gravitational-wave detectors
No full textGround-based gravitational-wave interferometers could directly probe the existence of ultralight dark matter [O(10-14-10-11) eV/c2] that couples to standard model particles in the detectors. Recently, many techniques have been developed to extract a variety of potential dark-matter signals from noisy gravitational-wave data; however, little effort has gone into ways to distinguish between types of dark matter that could directly interact with the interferometers. In this work, we employ the Wiener filter to follow-up candidate dark-matter interaction signals. The filter captures the stochastic nature of these signals and, in simulations, successfully identifies which type of dark matter interacts with the interferometers. The power of this method to distinguish between different types of dark matter comes from different coupling mechanisms that result in different power spectra, as well as different correlations between detectors spread across the Earth. We apply the Wiener filter to outliers that remained in the LIGO/Virgo/KAGRA search for dark photons in data from the most recent observing (O3) [R. Abbott (LIGO Scientific, Virgo, KAGRA Collaborations), Phys. Rev. D 105, 063030 (2022)PRVDAQ2470-001010.1103/PhysRevD.105.063030] and show that they are consistent with noise disturbances. Our proof-of-concept analysis demonstrates that the Wiener filter can be a powerful technique to confirm or deny the presence of dark-matter interaction signals in gravitational-wave data and distinguish between scalar and vector dark-matter interactions
Experimental analysis of stall inception in a two-stage, low-speed axial-flow compressor
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Una metodologia per l'analisi sperimentale dell'interazione fra scie e schiere di pale in un compressore bistadio
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