Study On Gas-injected Transportation Technology Of Cutter Suction Dredger

Cutter suction dredger plays an important role in engineering projects with its wide application in lake dredging, channel regulation, port construction and land reclamation, and so on. To transport slurry in long distance from dredging waters to slurry storage place, the dredging projects often encounter limitation on efficience, operation scope and operation costs and meet probles like huge pipe resistance, high energy consuming, pipe blocking and short transportation distance, since slurry has the features like its high concentration, nonuniform particles and complex ingredients. The key of the solution to such limitation and problem lies in how to apply aided techniques to reduce pipe resistence and lengthen transportation distance with less abrasion.This dissertation researches on resistance reducing mechanism, its effect and relevant scope from the theoretical, experimental and applied levels. The theoretical research includes identifing the quality and category of slurry, analyzing slurry flow states in the inner pipe and how such states change after air injection to pipes. Here flow states under various parameters in the inner pipes are mainly divided into 4 types such as stratified flow, slug flow over a stationary bed, slug flow over a moving bed, and fully suspended slug flow as well. These four flow types have their respective mathematical modals to calculate inner pipe pressure distritution with relevant parameters of gas flow, slurry flow, slurry density, slurry concenration and pipe diameter. The pressure distritution reflects corresponding resistance force in pipe and helps to identify critical velocities of injected gas and transported slurry.Experimental research first focuses on optimizitation of gas-injected transportation test-bed, invovling optimized data-collecting system,monitoring system and air-injector.The next attention is given to testing plans, which adjust slurry flow through power change of main pump, reinforce gas flow through air compressor, and increase slurry concentration from clear water to 30%.The experimental research sorts out groups of data and makes comparison with the calculated results from theoretical models to examine accuracy and applicability of mathematical models, providing theoretical basis and evidence to air-injected effect and resistance reducing efficeincy.Applied research gives assessments to the applicability of the whole air-injected transportation system. The gas-injected equipments are exchanged for commonly-applied relay pump equipments, which are tested under different slurry concentration and flow. The two systematical data are comparatively analyzed from the aspects of flow, transportation distance, output of slurry, and energy consumption to identify their respective advantages and disadvantage to serve as reference to engineering projects.