Onboard Measurements of Pressure and Strain Fluctuations in a Model of low Head Francis Turbine. Part 1 : Instrumentation

In this first part of a 2 papers series, we present the experimental procedure for onboard measurement of pressure and strain fluctuation in a model of low head Francis turbine. 28 miniature pressure sensors are fitted in the pressure and suction sides of two consecutive blades. A specific technique for sensors mounting has been developed allowing a direct manufacturing of the pressure sensors in the runner blades. This prevents from any geometry alteration of the hydraulic profile. Furthermore, miniature piezo electric strain gauges, 70 times more sensitive than conventional gauges, are embedded in pressure and suction side of 2 runner blades. Data acquisition is ensured by 32 channels onboard digitiser, having 12 bits resolution, 64 K-samples memory depth and 20 kHz maximum sampling frequency. Both static and dynamic calibration procedures of the pressure transducers are described. Analysis of experimental results and comparison with CFD calculation are presented in the second part (Ref. 7)

Interactions between microfibrillar cellulose and carboxymethyl cellulose in an aqueous suspension

New microstructures with interesting, unique and stable textures, particularly relevant to food systems were created by redispersing Microfibrillar cellulose (MFC). This paper reports the interactions between microfibrillar cellulose and carboxymethyl cellulose (CMC) in redispersed aqueous suspensions, by using rheological measurements on variable ratios of MFC/CMC and correlating these with apparent water mobility as determined by time domain NMR. MFC is a network of cellulose fibrils produced by subjecting pure cellulose pulp to high-pressure mechanical homogenisation. A charged polymer such as CMC reduces the aggregation of microfibrillar/fibre bundles upon drying. Small amplitude oscillatory rheological analysis showed the viscoelastic gel-like behaviour of suspensions which was independent of the CMC content in the MFC suspension. A viscous synergistic effect was observed when CMC was added to MFC before drying, leading to improved redispersibility of the suspension. Novel measurements of NMR relaxation suggested that the aggregated microfibrillar/fibre bundles normally dominate the relaxation times (T2). The dense microfibrillar network plays an important role in generating stable rheological properties and controlling the mobility of the polymer and hence the apparent mobility of the water in the suspensions

Characterization and properties of cationic cellulosic fibres

cited By 9International audienceThis paper is devoted to the rheological properties of cationic cellulosic fibres with different degrees of substitution and swelling. Depending on the concentration of the fibre suspension, the system behaves as a solution (C < 5 g/l) or as a gel. The rheological characteristics of the suspensions are directly related to the degree of substitution, the degree of swelling and the degree of fibrillation of the material. This paper is devoted to the rheological properties of cationic cellulosic fibres with different degrees of substitution and swelling. Depending on the concentration of the fibre suspension, the system behaves as a solution (C<5 g/l) or as a gel. The rheological characteristics of the suspensions are directly related to the degree of substitution, the degree of swelling and the degree of fibrillation of the material

Characterization and properties of cationic cellulosic microfibrils

International audienc