Erosion Prediction of Gas Turbine Compressor Blades Subjected to Water Washing Process

Technical BriefsBlade fouling is a relevant problem in turbomachinery applications. It affects both compressors and turbines. In the first case, fouling can be generated by the presence of dust, ashes or brackish air (in offshore applications). In turbines, fouling is mainly generated by residual of combustion process. Blade fouling generally leads to a reduction of the performance due to an increase on profile losses. Here we focus on the fouling due to salt deposition on naval/off-shore applications referring to machines that are part of the fleet of gas turbines manufacturers. In such applications, it is common to introduce on-line washing devices aiming at removing fouling from the early stages of the compressors. The water is sprayed upstream of the first rotor, it impacts on the rotor blades and thus dissolving the deposited salt. However, this procedure possibly leads to blade erosion and/or corrosion. A clear comprehension of the erosion mechanism is the main objective of the present work. To this end, we propose an integrated multi-phase CFD tool. The multi-phase flow is analyzed by adopting a one-way coupling, thus assuming water droplets to be drag by the carrier flow without influencing the main flow. The droplets are dispersed and tracked singularly by adopting a Lagrangian approach. As for the erosion, well-known and widely accepted models are used. The capability of a Lagrangian code, P-Track, developed and validated at the Department of Mechanical & Aerospace Engineering, Sapienza University in Rome, is presented. The code is able to predict the droplets trajectories, as well as to simulate the impact on the solid walls and the erosion mechanism. Simulations were performed using 25 and 100 ?m droplet size. Results, expressed in terms of normalized erosion rate, show the erosion patterns and erosive effect of the two size classes. Erosive capacity is proportional to droplet size, and the most eroded part of the blade is the leading edge, which is in qualitative agreement with measurements

Erosion Prediction of Gas Turbine Compressor Blades Subjected to Water Washing Process

Technical BriefsBlade fouling is a relevant problem in turbomachinery applications. It affects both compressors and turbines. In the first case, fouling can be generated by the presence of dust, ashes or brackish air (in offshore applications). In turbines, fouling is mainly generated by residual of combustion process. Blade fouling generally leads to a reduction of the performance due to an increase on profile losses. Here we focus on the fouling due to salt deposition on naval/off-shore applications referring to machines that are part of the fleet of gas turbines manufacturers. In such applications, it is common to introduce on-line washing devices aiming at removing fouling from the early stages of the compressors. The water is sprayed upstream of the first rotor, it impacts on the rotor blades and thus dissolving the deposited salt. However, this procedure possibly leads to blade erosion and/or corrosion. A clear comprehension of the erosion mechanism is the main objective of the present work. To this end, we propose an integrated multi-phase CFD tool. The multi-phase flow is analyzed by adopting a one-way coupling, thus assuming water droplets to be drag by the carrier flow without influencing the main flow. The droplets are dispersed and tracked singularly by adopting a Lagrangian approach. As for the erosion, well-known and widely accepted models are used. The capability of a Lagrangian code, P-Track, developed and validated at the Department of Mechanical & Aerospace Engineering, Sapienza University in Rome, is presented. The code is able to predict the droplets trajectories, as well as to simulate the impact on the solid walls and the erosion mechanism. Simulations were performed using 25 and 100 ?m droplet size. Results, expressed in terms of normalized erosion rate, show the erosion patterns and erosive effect of the two size classes. Erosive capacity is proportional to droplet size, and the most eroded part of the blade is the leading edge, which is in qualitative agreement with measurements

Gut Microbiota Features in Young Children With Autism Spectrum Disorders

Proliferation and/or depletion of clusters of specific bacteria regulate intestinal functions and may interfere with neuro-immune communication and behavior in patients with autism spectrum disorder (ASD). Consistently, qualitative and quantitative alteration of bacterial metabolites may functionally affect ASD pathophysiology. Up to date, age-restricted cohort studies, that may potentially help to identify specific microbial signatures in ASD, are lacking. We investigated the gut microbiota (GM) structure and fecal short chain fatty acids (SCFAs) levels in a cohort of young children (2–4 years of age) with ASD, with respect to age-matched neurotypical healthy controls. Strong increase of Bacteroidetes and Proteobacteria and decrease of Actinobacteria was observed in these patients. Among the 91 OTUs whose relative abundance was altered in ASD patients, we observed a striking depletion of Bifidobacterium longum, one of the dominant bacteria in infant GM and, conversely, an increase of Faecalibacterium prausnitzii, a late colonizer of healthy human gut and a major butyrate producer. High levels of F. prausnitzii were associated to increase of fecal butyrate levels within normal range, and over representation of KEGG functions related to butyrate production in ASD patients. Here we report unbalance of GM structure with a shift in colonization by gut beneficial bacterial species in ASD patients as off early childhood

Corrigendum: Gut Microbiota Features in Young Children With Autism Spectrum Disorders

[This corrects the article DOI: 10.3389/fmicb.2018.03146.]

Erosion prediction of gas turbine compressor blades subjected to water washing process

Blade fouling is a very relevant problem in turbomachin-ery applications. It affects both compressors and turbines. In the first case, fouling can be generated by the presence of dust, ashes or brackish air (in offshore applications). In turbines, fouling is mainly generated by residual of combustion process. Blade fouling generally leads to a reduction of the performance due to an increase on profile losses. Here we focus on the foul-ing due to salt deposition on naval/off-shore applications refer-ring to machines that are part of the fleet of gas turbines man-ufacturers. In such applications, it is common to introduce on-line washing devices aiming at removing fouling from the early stages of the compressors. The water is sprayed upstream of the first rotor, it impacts on the rotor blades and thus dissolving the deposited salt. However, this procedure possibly leads to blade erosion and/or corrosion. A clear comprehension of the erosion mechanism is the main objective of the present work. To this end, we propose an integrated multi-phase CFD tool. The multi-phase flow is analyzed by adopting a one-way cou-pling, thus assuming water droplets to be drag by the carrier flow without influencing the main flow. The droplets are dis-persed and tracked singularly by adopting a Lagrangian ap-proach. As for the erosion, well-known and widely accepted models are used. Firstly, a CFD study will be carried out to investigate the fluid-dynamic field by using ANSYS CFX 16.2 for the turbulent flow simulation. CFX is also used for carrying out a compara-tive analysis of the blade erosion mechanism. However, due to limits of the available models, sand particle (and not water droplets) erosion was modeled. Then, the capability of a La-grangian code, P-Track, developed and validated at the De-partment of Mechanical & Aerospace Engineering, Sapienza University in Rome, is presented. The code is able to predict the droplets trajectories, as well as to simulate the impact on the solid walls and the erosion mechanism