Study On The Influences Of The Reception Mode And Parameters Of PDA On The Measure Of Gas-Solid Flow Field

With the in-depth study of two-phase flow,its measurement tools are constantly improving. The PDA which manufactured on the basis of the Laser Doppler principles has widely used in research because of its own advantages. But because the hardware debugging and software preferences are very complex, there is some doubt in measurements. In order to resolve the existing problems, this paper analyzed the measurement ways and the results of PDA in this experiment.The thesis expounded speed,concentration and diameter metrical principles measured with PDA. It explained the common concept in measurements, and put forward that the optimized configuration of Fiber PDA, using Lorenz-Mie scattering theory analyzed why forward scatter is better than backscatter.The thesis designed an experiment plat to calibrate the PDA. In the experiment, it used the flute pipe which had calibrated by the standard pitot to measure speed, and used the pressure sensor to survey the powder quantity, then to compute the speed mean value and the concentration mean value of measurement section. In the experiment, it used the forward scatter and the backscatter separately to measure the measurement section under the different concentrations, and made the comparison between integral values with the demarcation result. Discovering what kinds of dimension PDA were used, the measure for speed fluctuated little and the relative error was also small. It can be said that PDA was satisfied the scientific research experiment to the speed measure. Surveying the concentration with different dimension PDA in forward scatter, by comparison with the demarcation result, the error basically in 30% scope, and the error tendency of 1D PDA, 2D PDA and the 3D PDA is increasing. But when using the backscatter, the concentration deviated by far to the demarcation result, also the diameter was about three times bigger than real value. The error tendency of 1D PDA to 3D PDA is decreasing. Using the same dimension PDA under the backscatter to measure the concentration, we can find that with the enlargement of concentration, the observed value not all increased, It beacouse of the light intensity weakened when the concentration increased.And the result waits for further confirms. The thesis also simulated the experiment with the FLUENT software.The paper compared the result among the PDA coincidence, PDA non-coincidence and the transformed value of PDA non-coincidence. analyzing influence of the different samples at one point, and concluded that in the experiment, when the sample number was bigger than 5000 at one point, the change tendency of surveyed value tended to steady and approached to the true value. The thesis also proposed the parameter configuration suggestion basing on the contrast between the bandwidth and the record length when they were set at different value. Besides, it offered that the light intensity will be weakened, when light and granule traversed each other.In view of the long-standing question, such as the receive probe work distance, the photomultiplier tube and so on, the thesis gave the explanation; proposed the debugging step and method of the PDA instrument, and it will be good for the proceeding of later scientific research experiment.