船舶腐蚀相关的轴频电场特征

Research on the corrosion related to shaft-frequency electric field

通过测量和分析船舶缩比模型轴频电场信号,研究了与船舶腐蚀相关的轴频电场特征.实验结果表明,船模轴频电场是由于螺旋桨转动调制腐蚀电流和阴极保护电流而产生的,是以螺旋桨转动速率为基频的低频电场.轴频电场随着螺旋桨转速逐渐增大,信号特征越来越明显,幅值越来越大.调制阴极保护电流而产生的轴频电场最大的幅值比调制腐蚀电流所产生的电场大10倍之多.船模轴频电场三分量除在幅值上有很大差异外,功率谱密度强度也有显著差异.其中x分量轴频电场最大,y分量轴频电场次之,z分量轴频电场最小.

By NI signature gathering system, the shaft-frequency electric field of ship＇ s physical scale model is measured. At the same time, the source mechanism of the corrosion related to shaf-frequency electric field is described. Results show that the shaft-frequency electric field signature arises around a vessel and transmits in the surrounding seawater due to the current flow from impressed current cathodic protection （ICCP） system and the current flow resulting from the corrosion of dissimilar metals during propeller rotation, which contains both shaft fundamental and harmonics. The signature character of electric field is more and more marked with the shaft rotation speed increasing. The amplitude of electric shaft-frequency electric field by modulating the current of ICCP system is 10 times greater than that of corrosion current. Besides amplitude, the power spectrum density intensity of shaft-frequency electric field also shows markedly difference from each other in three directions. The shaft-frequency electric field of x-axis direction is the greatest, and that of z-axis direction is the smallest.