Early Detection Of Rotating Stall Phenomenon In Centrifugal Compressors By Means Of ASME PTC 10 Type 2 Test

LectureA centrifugal compressor presenting rotating stall can exhibit many problems, as limitation on its operational range, high level of subsynchronous vibrations, reduced efficiency and premature bearing wear. There are many design criteria and standard practices for aerodynamic design of impellers and diffusers of centrifugal compressors. Nonetheless, the inception of rotating stall in new projects is still a reality. Therefore, an early detection of this phenomenon in a compressor is highly desirable. This paper proposes a way to detect the rotating stall problem during an ASME PTC10 Type 2 Test and how to scale these results (amplitude of vibration and inception point) as an estimative to site conditions. A comparison between the results of the proposed extrapolation from ASME PTC10 Type 2 Tests to the full load/density (almost an ASME PTC-10 Type 1 test) conditions is also presented. Scaling up guidelines for vibrations from similarity test to full density conditions are presented. Finally, an acceptance criterion for the amplitude of subsynchronous vibrations is proposed

Genomic epidemiology reveals how restriction measures shaped the SARS-CoV-2 epidemic in Brazil

Abstract Brazil has experienced some of the highest numbers of COVID-19 infections and deaths globally and made Latin America a pandemic epicenter from May 2021. Although SARS-CoV-2 established sustained transmission in Brazil early in the pandemic, important gaps remain in our understanding of local virus transmission dynamics. Here, we describe the genomic epidemiology of SARS-CoV-2 using near-full genomes sampled from 27 Brazilian states and an adjacent country - Paraguay. We show that the early stage of the pandemic in Brazil was characterised by the co-circulation of multiple viral lineages, linked to multiple importations predominantly from Europe, and subsequently characterized by large local transmission clusters. As the epidemic progressed, the absence of effective restriction measures led to the local emergence and international spread of Variants of Concern (VOC) and under monitoring (VUM), including the Gamma (P.1) and Zeta (P.2) variants. In addition, we provide a preliminary genomic overview of the epidemic in Paraguay, showing evidence of importation from Brazil. These data reinforce the need for the implementation of widespread genomic surveillance in South America as a toolkit for pandemic monitoring and providing a means to follow the real-time spread of emerging SARS-CoV-2 variants with possible implications for public health and immunization strategies