1,721,258 research outputs found
TIME-SPACE EVOLUTION OF SECONDARY FLOW STRUCTURES IN A TWO-STAGE LOW-SPEED TURBINE
No full textThe aim of this work is to highlight the unsteady effects related to wake-blade and blade rows interactions, but also the time-space evolution of secondary flow structures in a two-stage low-speed turbine model designed and constructed to perform unsteady measurements with different techniques [1]. In this case attention has been addressed to the analysis of the flow field in the first stage of the turbine model. Measurements are performed with aerodynamic probes downstream of the first stator and using a single slanted hot-wire anemometer downstream of the first rotor.
Time-dependent relative flow field downstream of the first rotor (obtained from phase-locked averaging technique) have been reconstructed for different relative positions between stator and rotor blades. From these results the time- dependent secondary flow vectors have been obtained as well.
The mean reference flow used to determine the secondary flow structure has been evaluated for each frame by mass-averaged technique. The evolution of the secondary flow structure due to the influence of the upstream and downstream stators on the first rotor has been investigated. The main unsteady effects put in evidence the variation of the intensity and spatial extension of the vortex flow structure
The short FFT database and the peak map for the hierarchical search of periodic sources
No full textIn the hierarchical search for periodic sources the construction of the short FFT database (SFDB) plays a key role for the next steps of the search, in terms of easy and fast access to the needed information and of data quality. The last information is crucial when combining data over long time periods, given the presence of non-stationarities in the noise. We will outline here the procedure we use to construct the SFDB and in particular the peak map, which is the first step of the hierarchical procedure, describing the tools we use to remove disturbances, which would enhance the noise floor. We will also describe the data and information we evaluate and store to characterize each FFT Particular emphasis is given to the procedure used to construct the estimator of the average noise spectral density, which is needed for good detection efficiency in the identification of peaks. We will give some examples, using non-stationary data of the resonant detector Nautilus and simulated signals added to the noise
The influence of the IGV on the rotating stall cell structure in a two-stage low-speed axial-flow compressor
No full textEvaluation of sensitivity and computing power for the Virgo hierarchical search for periodic sources
No full textIn this paper we present the hierarchical search for periodic gravitational sources that we propose for the data analysis of the Virgo and Explorer and Nautilus resonant gravitational antennae. All the equations that can be used to 'tune' the algorithm are presented
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