HIGH-RESOLUTION DATA-PROCESSING FOR PHASE-DOPPLER MEASUREMENTS IN A COMPLEX 2-PHASE FLOW

Measurements of the particle size and velocity in a gas-solid two-phase flow using the phase-Doppler technique based on transient recorder data processing and the cross-spectral density (CSD) function are improved in accuracy by introducing new complex interpolat on functions to the discrete frequency lines. The improvements of the accuracy for size and velocity measurements are additionally based on the use of an external electronic unit, which is allowed to trigger the transient recorder near the peak of the envelope of the band-pass filtered bursts. This procedure could improve the signal-to-noise ratio of the processed part of the signal and hence the accuracy and data rate. Furthermore, any uncertainty in setting a predefined trigger level could be avoided. Especially in complex flows where regions of low velocity exist, a very accurate velocity estimation is necessary in order to reduce the relative error. A simultaneous measurement of the gas velocity is achieved by seeding the flow with small spherical glass beads which have the same refractive index as the dispersed phase particles. The identification of signals from these seeding particles - with a diameter less than 4-mu-m - is based on the phase between the two signals.