Rotating stalls are generally the first instability met in turbomachinery, before surges. This 3D phenomenon is characterized by one or more stalled flow cells which rotate at a fraction of the impeller speed. The goal of the present work is to shed some light on the entropy generation in a centrifugal fan under rotating stall conditions. A numerical simulation of entropy generation is carried ...

A combination of theoretical and computational nonlinear analysis techniques are used to study the scenario of bifurcations responsible for the initiation of rotating stall in an axial ow compressor model. It is found that viscosity tends to damp higher-frequency modes and so results in a sequence of bifurcations along the uniform-ow solution branch to stall cells of diierent mode number. Lower...

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A comparative study of two combined blowing/suction flow control methods was conducted on the pitching airfoil using unsteady Reynolds-averaged Navier–Stokes (URANS) method. One used leading-edge blowing and trailing-edge suction, which is referred to as a co-flow jet (CFJ), conformal slot CFJ (C-CFJ) adopted. Another suction with blowing, called reversed (R-CFJ). The S809 baseline its stall ch...

We show an application of the method of extremum seeking to the problem of maximizing the pressure rise in an axial flow compressor. First we apply extremum seeking to the Moore–Greitzer model and design a feedback scheme actuated through a bleed valve which simultaneously stabilizes rotating stall and surge and steers the system towards the equilibrium with maximal pressure. Then we implement ...

Health prophylaxis management practices have acquired a major role in the success of dairy herd health programs, however, little is known about the scope and level of implementation on Swiss dairy farms. The main objective of this study was therefore to provide a general overview of the most important preventive measures which are currently being used on these farms. In March 2011, an online su...

Blower and exhaust fans consume over 30% of electricity in a thermal power plant, and faults of these fans due to rotation stalls are one of the most frequent reasons for power plant outage failures. To accurately predict the occurrence of fan rotation stalls, we propose a support vector regression machine (SVRM) model that predicts the fan internal pressures during operation, leaving ample tim...

Based on the three-dimensional elliptic governing equations and the throttle model, an unsteady numerical simulation of rotating stall is undertaken in the case of G4-73 type centrifugal fan and the correctness of simulation results is verified by experiments. In this study a new rotating stall inception criterion is put forward, that the inlet flow or outlet back pressure fluctuations graduall...