Numerical Simulation and Optimization of Cathodic Protection for Ship and Ocean Structure
|School||Harbin Engineering University|
|Course||Design and manufacture of ships and marine structures|
|Keywords||ocean corrosion cathodic protection numerical simulation boundary element method optimization|
With the rapid development of China’s shipping industry, ship and ocean structureincreasingly tend to be more and more complicated, which put forward higher request for theeffectiveness of cathodic protection system. Thus seeking practical and effective cathodicprotection potential prediction and optimization method of ship and ocean structures is ofgreat significance to the development of ship and ocean engineering.Traditional cathodic protection design mostly adopts measures or experience to estimatepotential distribution. Actual measurement, while intuitive, high reliability, because of timeand space and environmental factors limit, is often constructed difficulty and expensive.Estimates based on the experience to some extent also cannot guarantee the accuracy of theresults. In recent years the rise of the computer and the numerical simulation technologyprovides a new technical method to the prediction, evaluation and optimization of cathodicprotection system of ship and ocean structures. Numerical simulation method is quick andeconomy, so this article’s research has important theoretical significance and engineeringpractical value.At first, this paper applied traditional formula to design ship and ocean structurepreliminary cathodic protection scheme. According to the structure mode and operatingenvironment and electrochemical properties of the ship and ocean structures, selectedprotection method and main parameter of cathodic protection design——protection potentialand protection current density. Obtained protection area by structure drawings or formula, andthen determined the types and number of auxiliary anode or sacrificial anode. Finallyconclude preliminary scheme which satisfies the requirement of corrosion protection goals.The above work lays the foundation for numerical simulation and optimization of cathodicprotection.This paper used the three-dimensional boundary element method to calculate themathematical model of cathodic protection. Introduced piecewise quasi linearized method todeal with nonlinear problem of boundary conditions. Established linear equations and solve it.Finally applied FORTRAN language to development numerical simulation software forpredicts cathodic protection potential. The software has flexible modeling mode and variousresults output forms, and is advantageous for the operation and practical engineering applications. Compared with experimental data, the results calculated by the software areaccuracy. Applied the software to forecast protection potential of9200TEU container shipimpressed current cathodic protection system and400ft jack-up drilling platform sacrificialanode cathodic protection system, and get accurate results. Put forward the modeling processand the boundary condition setting method according to the engineering applicationexperience. Adopt the method that keep the potential unchange in the polarization curve, andchange current density to simulate coating breakage in simulation process of9200TEUcontainer ship impressed current cathodic protection. Adopt block boundary element methodto solve electrolyte continuous problem and points regional modeling to solve electrolyteinconsistency in400ft jack-up drilling platform sacrificial anode cathodic protection. Themodel loaded into the inside potential value obtained in the calculation of whole area interiorsurface corresponding to the nodes in the model as boundary condition, jack-up platformcomplex node protection potential distribution was obtained. From the results we canconcluded that the400ft jack-up drilling platform sacrificial anode cathodic protection systemmeet the protection targets and the9200TEU container ship impressed current cathodicprotection system needed optimized.With that evenly distributed protection potential and minimum anode output current asoptimize targets, and the anode output current as optimize parameters, combine simulatedannealing algorithm and boundary element method to achive the ship’s cathodic protectiondesign optimization. By controlling the cooling schedule, this software realized theoptimization of process control. Adopt numerical simulation methods to calculate cathodicprotection potential of before and after optimization, and through analysis the potentialcontours of the ship drawn that the methods are feasible and efficient.