Study On Water Hammer Protection And Nozzle Performance In High Pressure Water Descaling System

In the hot strip production, descaling which is used to clean the furnace oxide scale(First oxide scale) and regenerated oxide scale (secondary oxide scale) in the surface ofslab has been an indispensable important process, the current technology that domesticand international widely used is high-pressure water descaling, which not only becauseof the economy, and effective. In the domestic high-pressure water descaling system,most of them in accordance with the hot rolling mill of the same type in foreign andwith the analogy to design, it is difficult to meet the requirements of the rolling processchanges, and it can not also guarantee that the strip surface quality. Due to water in thesystem piping is at high pressures, opening and closing time sequence of descalingvalve is uncertain. They both result that water hammer and vibrates often occurs in thepipeline, this is also bound to probably damage the pipeline as well as attachedequipments and threaten the operation of production systems in serious conditions. So,this paper would carry out numerical calculation and necessary test for water hammerphenomenon on the basis of the computational theory of water hammer, and then tounderstand the fluid transient conditions within high-pressure water descaling systempiping, and to develop appropriate water hammer protection measures. By studying thecore component of descaling equipment–nozzle, so as to further improve thetechnology and the overall performance of the descaling system.This paper consists of following parts:(1) Discusses the basic differential equations of water hammer and water hammermethod of characteristics. The boundary conditions of high pressure water descalingsystem is established with the characteristic method, including: pump (normal operatingconditions), the injection valve (pipe end), accumulators, series and parallel pipelineand so on, in order to establish the universal mathematical model of high-pressure waterdescaling system water hammer calculations;(2) Carry out numerical calculation and experimental research for water hammerphenomenon in simple pipeline on the basis of the computational theory of waterhammer. The comparison and analysis of test and calculation results when the valve isclosed suddenly and quickly, the valve is closed slowly, the valve is opened and closedby the order, the valve is opened and closed in rapid and succession, so as to verify thecorrectness of numerical calculation; (3) Aimed at water hammer phenomenon in high-pressure water descaling process,a numerical calculation was carried out. The main analysis and research protectionfeatures of accumulators to water hammer, for example: the influence of water hammerprotection performance on the installation location of accumulators, the size ofaccumulators, the quantity of accumulators, and the setting of the pipe fixed braces, anddevelop appropriate protective measures for the water hammer in high-pressure waterdescaling system;(4) By the inside flow field numerical simulation for high-pressure water descalingnozzles, it can be obtained to the influence of the inside flow field on nozzle structuralparameters (such as: astringent angle, ratio of length to diameter, V-cut angle), and thusthe relationship between the nozzle structural parameters and dynamic performance areestablished. As to further improve the performance of descaling nozzles, so that it can toensure that the export jet velocity at the same time, reduce the water-head pressure indescaling system, and fundamentally reduce the harm brought about the water hammer.