蒸汽发生器换热管电磁超声纵向导波换能器设计与优化

高温气冷堆蒸汽发生器换热管特殊的螺旋结构导致传统外置型电磁超声导波换能器难以进行有效检测。本文针对蒸汽发生器不锈钢换热管的缺陷检测，开发了一种新型内置型电磁超声纵向导波换能器，建立了有限元多物理场耦合模型，研究了换能器铁磁结构的静态磁场分布，并对换能器激励出的纵向导波进行了时域仿真。结果表明：采用挤压聚磁的换能器结构可保证线圈附近的垂直方向磁场远大于水平方向磁场，能高效地在管道内部激励单一模式的纵向导波；优化后的探头可检测直径为5 mm的通孔缺陷和长×宽×深为20 mm×1.5 mm×1.2 mm的环向槽缺陷。因此，新型电磁超声纵向导波换能器可有效激励纵向导波，并有望应用于高温气冷堆蒸汽发生器换热管的在役缺陷检测。

Design and Optimization of Electromagnetic Ultrasonic Longitudinal Guided Wave Transducer for Heat Exchange Tube of Stream Generator

The special spiral structure of the heat exchange tube of the steam generator of the high-temperature gas-cooled reactor makes it difficult for the traditional external electromagnetic ultrasonic guided wave transducer to be effectively detected. Aiming at the defect detection of stainless steel heat exchange tube of stream generator, a new built-in electromagnetic ultrasonic longitudinal guided wave transducer is developed, a finite element multi physical field coupling model is established, the static magnetic field distribution of ferromagnetic structure of the transducer is studied, and the longitudinal guided wave excited by the transducer is simulated in time domain. The results show that: the use of the squeezed magnetization transducer structure can ensure that the vertical magnetic field near the coil is much larger than the horizontal magnetic field, and can efficiently excite a single mode of longitudinal guided waves inside the tube. The optimized probe can detect through-hole defects with a diameter of 5mm and circular groove defects with a length × width × depth of 20 mm×1.5 mm×1.2 mm. Therefore, the new electromagnetic ultrasonic longitudinal guided wave transducer can effectively excite the longitudinal guided wave, and is expected to be applied to the in-service defect detection of the heat exchange tube of the steam generator of the high-temperature gas-cooled reactor.