Research On Paper Suspension Flow Mechanism And Numerical Simulation For New Type Of Hydraulic Headbox

Hydrodynamic headbox is the paper suspension (P.S.) delivering equipment of papermaking machine, which stands at the head of the paper machine. It's mainly used to flow the uniform and stable P.S. evenly up to wire section. In order to gain the uniform basis weight, even formation, and avoid fiber flocculation, the P.S. flow through the headbox should have uniform distribution in the CD (cross-machine direction) and MD (machine direction). The structure of all components of the headbox must conform to hydraulic mechanism. Paper suspension flows through the headbox, The P.S. velocity profile and Renault number basically value its flow property, and the P.S. pressure and micro-turbulence effect chiefly reflect distribution and uniform effects of the units of the headbox. Thereinto, the design of micro-turbulence generator is crucial to the performance of the hydrodynamic headbox.To study the flow characteristic of hydraulic headbox, this thesis adopt the newest software of computational fluid dynamics (CFD) to simulate the micro-turbulence flow. Through further studying the international advanced designing principle of dilute headbox , establishing the mathematical governing equations of P.S. ,and numerical CFD simulation on the dilute distributor ,turbulence flow generator and nozzle ,we can optimize the structure of distributor and turbulence flow generator as well as develop diluted water manipulative system that can give us designing basis and control means .Referring to technique of the newest model of headbox we have gathered and mastered , we'll develop domestic pulp headbox which is not inferior to the same kind of headbox internationally in capability and performance.First of all, on the basis of the research results of predecessor and according to the structure characteristic of hydrodynamic headbox, we analyze the mechanism of main components of headbox, such as P.S. distributor, micro-turbulence generator and nozzle jet. Moreover, wesummarize the fiber dispersion and uniform distribution mechanism from hydrodynamics' angle. As for the given diluted P.S. in hydraulic headbox, we establish the P.S. governing equation through reasonable hypothesis.Secondly, we amend the turbulent computational model in FLUENT to accord to established theoretical model. As far as different distributor and turbulence generator structure be concerned, under the condition of variational fiber concentration and inlet velocity, we simulate the flow property of P.S. in hydrodynamic headbox by FLUENT. At the same time, we apply flow velocity, pressure, turbulence intensity and turbulence scale as well as fiber concentration to measure and compare capability of headbox.At last, based on our study, we gain the optimal structure of hydrodynamic headbox and conclude the optimizing design method for headbox.The study achievements are based on numerical CFD simulation on 3-D multi-phase flow of fiber suspension, and certain results are basically consistent with international experimental research conclusion. As furthering our study, we can optimize and design a new model of hydrodynamic headbox according to academic analysis, numerical simulation and experimental analysis, and these achievements can direct design as well as manufacture of hydraulic headbox.