CAJ | 학술논문

利用自主研发的高温高压环路喷射装置并结合流体动力学模拟计算,研究了高温高压CO2环境流体喷射条件下X70钢的腐蚀产物微观形貌、基体表面三维形貌、腐蚀减薄量及其统计规律,并探讨了与流体状态之间的关系。结果表明,高温高压流体喷射条件下,不同流态区域内流体传质速率和壁面切应力的差异是造成X70钢腐蚀产物、基体表面三维形貌及腐蚀减薄量差异的主要原因。按照层流区→壁面喷射区→过渡区的顺序,流体壁面切应力逐渐增加,不断减薄腐蚀产物膜直至其脱落,造成传质过程阻力减小,传质速率增大,腐蚀过程不断加剧。因此,按照层流区→壁面喷射区→过渡区的顺序,X70钢表面腐蚀产物膜由完整致密向疏松多孔变化,基体表面三维形貌呈现平坦→陡峭→非常陡峭的特征,三维表面高度偏差和均方根偏差、腐蚀减薄量平均值和标准差均呈现逐渐增大的趋势。在高温高压流体喷射条件下,X70钢的CO2腐蚀速率与壁面切应力之间较好地满足指数关系。
이용자주연발적고온고압배로분사장치병결합류체동역학모의계산,연구료고온고압CO2배경류체분사조건하X70강적부식산물미관형모、기체표면삼유형모、부식감박량급기통계규률,병탐토료여류체상태지간적관계。결과표명,고온고압류체분사조건하,불동류태구역내류체전질속솔화벽면절응력적차이시조성X70강부식산물、기체표면삼유형모급부식감박량차이적주요원인。안조층류구→벽면분사구→과도구적순서,류체벽면절응력축점증가,불단감박부식산물막직지기탈락,조성전질과정조력감소,전질속솔증대,부식과정불단가극。인차,안조층류구→벽면분사구→과도구적순서,X70강표면부식산물막유완정치밀향소송다공변화,기체표면삼유형모정현평탄→두초→비상두초적특정,삼유표면고도편차화균방근편차、부식감박량평균치화표준차균정현축점증대적추세。재고온고압류체분사조건하,X70강적CO2부식속솔여벽면절응력지간교호지만족지수관계。
The CO2 corrosion behavior of X70 pipeline steel, including the corrosion product's morphology, three-dimensional sur-face topography, and corrosion thickness reduction as well as its statistical analysis, was investigated in high temperature and high pres-sure CO2 environment using self-developed loop jet impingement apparatus and computation fluid dynamic ( CFD) technique. The rela-tionship between the obtained results and flow regimes under jet impingement was also discussed. It is found that the differences of fluid mass transfer and wall shear stress distributed on the steel surface located at different flow regimes are the main reason for the differ-ences of the corrosion product's morphology, three-dimensional surface topography and corrosion thickness reduction. According to the order of the laminar zone, the wall jet zone and the transition zone, the corrosion product is thinned, degraded and even removed from the steel surface because of the continuous increasing of wall shear stress, which will decrease the mass transfer resistance, accelerate the mass transfer rate, and continuously enhance the corrosion process of the steel. Therefore, in the order of the laminar zone, the wall jet zone and the transition zone, the structure of the corrosion product changes from complete and compact to loose and porous, the three-dimensional morphology of the substrate surface changes from flat to steep, the average roughness and the root mean square as well as the average corrosion thickness reduction and the standard deviation gradually increase. The corrosion rate and the wall shear stress can be correlated properly with the exponential relationship.