Research On Rheological Characteristics Of Coal Water Slurry And Its Measurement Technologies

Rheological characteristics are one of the most important indicators for quantity evaluation of coal water slurry, refer as CWS. It plays a key role for in the process of transport, storage and atomization of CWS. The commonly used rheological characteristics measurement methods are the rotational rheometer and capillary rheometer, which are not suitable for on-line operation. Consider of the thixotropy of CWS, the measuring results of these methods cannot reflect the actual rheological characteristics of the CWS in the production line. So that it has practical significance to find a new on-line measurement method for rheological characteristics of CWS.Starting with the analysis of rheological characteristics of CWS, it pointed out that the practical CWS should possess yield point, exhibit regions of pseudo-plastic behavior or little dilatants, and has low apparent viscosity. Consider of these, a lot of constitutive equations for non-Newtonian fluid were analyzed and compared with. The result show that the Bingham fluid model, the yield power law model and the Casson model are also with high goodness-of-fitting for CWS at moderate shear rates, and these model are function only when thixotropy effect is removed. Theory analysis of the thixotropy of CWS was processed then, and a thixotropy model of CWS was proposed. This model fit experiment data very well. After the study of the influence factor of the rheological characteristics of CWS, BP neural network was used for predicting rheological characteristics of CWS for the first time, and it has better effect than the Yield Power.According to the study of the rheological characteristics of CWS, the flow field distribution in the pipeline transports was analyzed in the dissertation. For steady transportation of multi-phase flow, it is point out that it is should be steady laminar flow and with plug flow for CWS in the pipeline transports. The velocity range was calculated. Base on the previous research, a moving-blade rheological characteristics measurement method for CWS was proposed. The method is studied base on non-Newtonian fluid mechanics theory and boundary layer theory, the dynamics model was achieved, and the rheological characteristics measurement model was given. The chosen problems of sampling position and the value of driven force were studied. And the plug flow influence to the measuring result was studied also. A plug flow measurement method was proposed in order to implement speed compensation for the moving-blade rheological characteristics measurement method. Consider to the influent of the slip effect of pipe flow. An optical cross-correlation slip speed measurement method was proposed. The measurement principle and the probe structure was study. In order to solve the integral filter effect of the optical fiber probe to the flow noise of CWS,2-D cross-correlation arithmetic was proposed, and polarity cross-correlation arithmetic was used to improve computing speed. In the dissertation, the blade shape improve method, the shading pulse processing circuits designing, the density measurement method and calibration method were studied also. The error analysis was done at last.The moving-blade rheological characteristics measurement method and the optical cross-correlation slip speed measurement method are innovative and with practical value, they could solve the problem that there is lack of fast and effective on-line rheological characteristics measurement method for CWS product process. These methods could also extend to on-line measure the rheological characteristics of other fluid, have broad application prospects.