Study On Erosion-corrosion Behavior Of Marine B10 Copper-nickel Elbow

With the gradual implementation of the strategic goal of "Marine Powerful Country" and the upgrading of the demand for offshore oil and gas resources development,China's shipbuilding industry develops rapidly,while the marine water pipeline system of ships undertakes important functions such as power,cooling and fire protection,and is an important work unit to ensure the normal navigation of ships.Due to the complex marine environment,under the condition of long-term transmission of sandy seawater by B10copper-nickel pipelines commonly used in seawater pipeline system,the leakage problem caused by erosion-corrosion is more serious,especially in the 90° elbow where the flow state of seawater has changed,the leakage occurs frequently in a short time,which causes serious economic losses and safety hazards.At present,the research on elbow erosion-corrosion is still limited to the general situation of overall erosion-corrosion.There is no systematic understanding and quantitative research on the difference of local erosion-corrosion behavior of elbow at different locations,and the evolution law of erosion-corrosion over time is not clear.Therefore,the research on the erosion-corrosion behavior of B10 copper-nickel elbow in this thesis not only has practical engineering value,but also provides certain theoretical reference for the corrosion and protection of pipelines.In this thesis,taking B10 copper-nickel elbow as research object,the erosion-corrosion behavior of B10 copper-nickel elbow was systematically studied by means of CFD,array electrode technology,electrochemical test and characterization of micro-morphology.The change rule of erosion-corrosion behavior of the elbow with time and space was clarified,and the difference and essence of erosion-corrosion in different space locations inside and outside of the elbow were revealed.The inhibition of BTA corrosion inhibitor on erosion-corrosion of copper-nickel alloy in sandy seawater was also discussed.The main research work is as follows:(1)The erosion-corrosion behavior of B10 copper-nickel 90° elbow is studied by CFD numerical simulation.The results show that under single-phase flow,the velocity inside the elbow is faster,and the secondary flow phenomenon at the inner outlet is obvious.The inner outlet of the elbow is a dangerous area of erosion-corrosion;Under the condition of liquid-solid two-phase flow,the order of influence of different factors on the erosion and corrosion of elbow is: B(inlet flow rate)> A(pipe diameter)> e(sand mass flow)> d(sand diameter)> C(liquid flow direction).When B is 5 m / S,a is 30 mm,e is 0.03 kg / s,C liquid flow direction is horizontal and vertical,and D is 500 ?m,the erosion-corrosion rate reaches the maximum,about 3.4 mm/a,and the dangerous area of leakage is concentrated at the outside and outlet of the elbow(the axial angle ? = 60° ? 90°,radial angle ? = 180°)?(2)Based on the numerical simulation results,the erosion-corrosion experiment of B10copper-nickel elbow was carried out by using array electrode,electrochemical test method and pipe flow cycle experimental device,and the erosion-corrosion rate distribution at different positions of the elbow was determined quantitatively.The results show that the erosion-corrosion rate of each array electrode increases gradually along the flow direction of the elbow,the erosion-corrosion rate of the inner electrode is generally lower than that of the outer electrode,and the erosion-corrosion rate reaches the maximum at the outer outlet of the elbow(No.5 electrode).The experimental results are in good agreement with the numerical simulation in the distribution law of erosion-corrosion of the elbow.(3)Based on the feasibility of practical pipeline corrosion protection,the corrosion inhibition effect of BTA(benzotriazole)inhibitor on B10 copper-nickel elbow under the condition of erosion-corrosion is studied by using array electrode.The experimental results show that BTA inhibitor can effectively reduce the corrosion current density of electrode,inhibit the erosion-corrosion of electrode,and achieve high inhibition efficiency.