Estimation of the Aerodynamic Force Induced by Vaneless Diffuser Rotating Stall in Centrifugal Compressor Stages

Abstract Rotating stall in centrifugal compressors not only adversely affects the performance before surge, but also can generate high subsynchronous vibrations, marking the minimum flow limit of a machine. Recent works presented an experimental approach to estimate the stall force induced by the unbalanced pressure field in a vaneless diffuser using dynamic pressure measurements. In this study, the results of a 3D-unsteady simulation of a radial stage model were used to estimate the stall force and to compare it with the approximation obtained with an "experimental-like" approach. Results showed that: a) the experimental approach, using an ensemble average approach for transposing data between time and space domains provides sufficiently accurate results; b) the momentum contribution, neglected in experiments, gives negligible contribution to the final intensity of the stall force

Development of a Research Test Rig for Advanced Analyses in Centrifugal Compressors

Abstract In this study, the design process of a new research test rig for centrifugal compressor stages is presented. The rig has been specifically conceived for advanced analyses, with particular focus on rotating stall and in general on the operating conditions close to the minimum flow limit, which represent the research frontier in view of an extension of the stages rangeability. The new rig will be able to test industrial impellers at peripheral Mach numbers up to 0.7, operating in open-loop with ambient inlet conditions. A modular design will allow to test different stage configurations and then to carry out systematic optimization campaigns on a single specific component. The conceptual design of the rig is here described and explained, including the selection of the best architecture and layout, the drivetrain assessment and the rotordynamic analysis

DNA-ENCODED PEPTIDE LIBRARIES AND DRUG DISCOVERY

Over the past decade, several methods have been developed for the construction of DNA-encoded peptide libraries. The common principle behind all these methods is the establishment of a physical linkage between a displayed peptide and its encoding DNA. Vast libraries can be generated, binding peptides can be isolated with simple selections, and the sequences of selected peptides can be rapidly determined from the sequence of the linked DNA. As a result, DNAencoded libraries can provide specific ligands for essentially any protein. These ligands can be used to determine the natural binding specificities of protein–protein interactions, and this information can be used to identify natural binding partners or to aid the design of organic mimics. Binding peptides can also be used for target validation and the development of high-throughput screens for small-molecule libraries. Finally, binding peptides themselves could prove useful as drugs

Place-Based Policies and Political Discontent: The Mediating Role of Local Spending Programmes

This paper introduces the special issue «Recent developments in the geography of discontent». The contributions cover topics of increasing interest to the regional science community in recent years: the analysis of the main determinant behind the geographically heterogeneous rise of political discontent, the role played by regional institutions and bottom-up place-based policies in contrasting the expansion of right-wing populist parties, and the advantages of applying sophisticated statistical learning tools for studying the geography of discontent. The studies suggest relevant policy implications ranging from improving the quality of local institutions to addressing local economic and educational fragilities

Cocleo-labirintopatie nel bambino. Come non perdere l'equilibrio.

Cochleo-labyrinthopathy (CL) is an affection that involves cochlea and vestibular system. It occurs with the association of auditory symptoms (sensorineural hearing loss and tinnitus), vestibular symptoms (objective vertigo, unidirectional horizontal-rotary nystagmus and static or dynamic balance disorders) and neurovegetative signs (nausea, vomiting, pallor, sweating, etc.). The diagnosis may be difficult in paediatric age since the child is unable to clearly express their discomfort and symptoms. Multiple causes have been recognized but, in acute cases, infection is the most frequent etiological agent. The paper describes a case of CL due to Herpes Virus 1-2 infection responsive to acyclovir and reports a flowchart for the diagnostic approach to the vertiginous syndromes in childre

UN OMBELICO...TROPPO SPESSO BAGNATO

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Bambini, soprattutto: storia di bambini-migranti dei nostri giorni

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Experimental analysis of the pressure field inside a vaneless diffuser from rotating stall inception to surge

An accurate estimation of rotating stall is one of the key points for high-pressure centrifugal compressors, as it is often connected with the onset of detrimental subsynchronous vibrations which can prevent the machine from operating beyond this limit. With particular reference to vaneless diffuser rotating stall, the most common practice in industrial machines is to make use of a limited number of dynamic pressure probes to reconstruct the stall characteristics after an ensemble averaging approach. In this study, a 1:1 model of an industrial compressor stage was tested in a dedicated test rig and equipped with 24 pressure probes properly distributed along the diffuser circumference with the scope of providing a real-time visualization of the spatial pressure distribution within the diffuser. The results allowed the assessment of some important characteristics of the stall cells that were historically supposed based on averaged data, e.g. the cells rigidity. Moreover, the present study confirmed the existence of a stall pattern with two almost axisymmetric lobes. Finally, the transient analysis of both the stall inception and the surge onset was carried out, highlighting the flow field evolution in the diffuser under these conditions