Abstract
Particle concentration or mass flux measurements by phase-Doppler anemometry are based on counting the number of particles crossing the probe volume. In complex particulate flows this requires the knowledge of the particle size-dependent cross-section of the measurement volume perpendicular to the instantaneous particle velocity for each sample. A new method is presented which allows to estimate the instantaneous particle velocity using a one-component PDA-system with the aid of the integral value under the envelope of the Doppler signal.
The envelope is reliably determined by a recently developed analogue burst detection electronic circuit using narrow band-pass filters and a synchro detector. The particle size-dependent measurement volume is obtained by the mean log-arithmic amplitude method introduced by Qiu and Sommerfeld (1992).
The special signal processing requirements for realizing this method were implemented in a novel signal processor which additionally involves a burst detection based on an online estimation of the signal-to-noise ratio (SNR) and hence the data aquisition is only triggered for signals above a pre-set SNR level. The estimation of the signal frequency and phase is based on the calculation of the cross-spectral density using a hardware FFT (Fast Fourier Transform) chip.
In order to demonstrate the accuracy of the novel method for particle concentration and mass flux determination, measurements were performed in a liquid spray and a particle laden swirling flow. Especially in the swirling flow, the particles exhibit random trajectories through the measurement volume and the powerfulness of the present method is demonstrated especially for this complex flow.
References
Aizu Y; Domnick J; Durst F; Grehan G; Onofri F; Qui HH; Sommerfeld M; Xu TH; Ziema M (1994) A new generation of phase-Doppler instruments for particle velocity, size, and concentration measurements. Particle and Particle Systems Characterization 11: 43–53
Goodman JW (1968) Introduction to Fourier Optics. McGraw-Hill.
Grehan G; Gouesbet G; Naqwi A; Durst F (1992) On elimination of the trajectory effect in phase-Doppler systems. PARTEC, Preprints of the 5. European Symposium Particle Characterization 1: 309–318
Qiu HH; Sommerfeld M; Durst F (1991) High-resolution data processing for phase-Doppler measurements in a complex two-phase flow. Measurement Science Technology 2: 455–463
Qiu HH; Sommerfeld M; Durst F (1994) Two noval signal identification methods for laser-Doppler and phase-Doppler anemometry. Measurement Science Technology 5: 169–778
Qiu HH; Sommerfeld M (1992) A reliable method for determining the measurement volume size and particle mass fluxes using phase-Doppler anemometry. Exp Fluids 13: 393–404
Qiu HH (1994) Signalverarbeitung bei der Phasen-Doppler Anemometrie zur Geschwindigkeits-, Größen- und Konzentrationsmessung in zweiphasigen Strömungen. Ph. D. Thesis, University Erlangen/Nürnberg
Saffman M (1987) Automatic calibration of LDA measurement volume size. Appl Opt 26: 2592–2597
Saffman M (1989) Phasen-Doppier-Methode zur optischen Partikelgrößenmessung. Technisches Messen 56: 298–303
Sankar SV; Bachalo WD (1991) Response characteristics of the phase Doppler particle analyzer for sizing spherical particles larger than the wavelength. Appl Opt 30: 1487–1496
Sommerfeld M; Qiu HH (1993) Characterization of particle-laden, confined swirling flows by phase-Doppler anemometry and numerical calculation. Int J Multiphase Flow 19: 1093–1127
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The development of the presented method for concentration measurements was performed in the framework of the JOULE I project: “Advanced flow modelling for industrial applications” (Contract: JOUE-CT91-0067). The financial support of the CEC is gratefully acknowledged.
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Sommerfeld, M., Qiu, H.H. Particle concentration measurements by phase-doppler anemometry in complex dispersed two-phase flows. Experiments in Fluids 18, 187–198 (1995). https://doi.org/10.1007/BF00230264
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DOI: https://doi.org/10.1007/BF00230264