激光诱导空泡空化强化机理与激励特性研究

This project is committed to propose the cavitation enhancement technology of vacuoles induced by laser to solve the scientific issues on complicated mechanism and heavy damages of cavitation and cavitation erosion in hydraulic machinery. The formation of high speed and high pressure micro jet by constraining and optimizing the excited and vacuoles shock wave was stimulated based on the laser self-focusing and laser shock strengthening principles. The strengthening effects of micro jet on the processing and modification performances of hydraulic machinery was utilized to elaborate vacuoles micro jet strengthening theory induced by laser. Related scientific issues such as mechanism of laser cavitation, laser-induced symmetric motion model of vacuoles spherically, composite incentive mechanism of laser cavitation, the enhancement of micro jet and high cavitation performance pump model are studied from the theoretical and experimental aspects respectively. High speed photography and high-frequency test technology are applied to further explore the superimposed effect of bubble clusters and vacuoles propelled by the exploding of laser underwater. The suppression countermeasures of cavitation erosion in hydraulic machinery and evaluation guidelines for safe operation in cavitation conditions are also raised. The theory of laser shock processing strengthening combined with laser-induced vacuoles micro jet strengthening is innovatively proposed. Laser cavitation could become an effective means to improve the surface properties of materials through the researching and mastering of the cavitation erosion resistance technology and corrosion resistance technology by laser shock processing. A brand new laser cavitation strengthening theory and technique would be acquired. Moreover, the project is of very important scientific significances and has a broad engineering application prospects.

本项目针对水力机械空化空蚀机理复杂、危害严重的科学问题，提出激光诱导空泡推进空化强化理论与技术。基于激光共聚焦和激光冲击强化原理，对激发空泡冲击波优化约束形成高速高压空泡微射流，应用微射流强化效应对水力机械加工与改性，阐明激光空泡微射流强化新理论。从理论与实验两方面分别对激光空化机理、空化空泡球对称运动模型、激光-空化复合激励机制、微射流强化效应、高空化性能水泵模型等相关科学问题进行研究；融合高速摄影与高频测试技术，进一步探讨激光水下爆炸推进空泡群与空泡叠加效应，提出水力机械空化空蚀抑制对策及在空化条件下安全运行的评价准则；创新提出激光冲击强化与激光空泡微射流复合强化理论，研究并掌控激光强化提高部件抗空蚀性与耐腐蚀技术，促使激光空化成为一种可以改善材料表面性能的有效手段。本项目的研究可获得一种全新的激光空化强化理论与技术，具有很重要的科学意义与广阔的工程应用前景。

本项目围绕“激光诱导空泡空化强化机理与激励特性研究”新机理新工艺，着重解决水力机械空化空蚀机理复杂、危害重的科学问题。.本项目巧妙地将空化空泡溃灭产生的原本对水力机械造成冲蚀破坏、工作效率下降等严重副作用的高强度冲击力，优化控制转变为高幅值残余压应力，有效提高材料表面的微动疲劳抗力，达到对材料表面强化延寿的目的。研究从理论和实验方面深入研究了空化和空蚀现象，等离子体冲击波在水中的传播特性、激光空化的机械效应和化学效应、材料表面组织和力学性能、抗空蚀性能等内容。.项目完成并构建了多系统自动化协调工作的激光空化强化系统，研发出适用泵阀芯、水泵叶轮等典型部件的激光空化强化装备；获得了空泡惯性生长、溃灭和回弹规律，讨论了含气量、表面张力、液态粘性和可压缩性对空泡溃灭压力的影响，并测试出等离子体冲击波在水中的传播特性，探测出激光等离子体冲击波声压信号，定量测量了靶材表面的力学效应，揭示了激光空化的机械效应；测试出激光空化的羟自由基含量，建立羟自由基与2A02铝合金表面残余应力的关系，揭示激光空化的化学效应，形成了一种表征材料空化强化效果的新方法；通过求解质量连续方程、Navier-Stokes方程和界面方程研究了空泡冲击波和微射流，采用FLUENT软件中的VOF多相流模型和全空化模型获取空泡整个脉动过程气液两相分界面的动态变化序列图，揭示了激光空化强化的关键科学问题；获得了激光空化强化对铸铁和铝合金等金属材料的抗空蚀性能影响关系，阐述了激光空化增强材料抗空蚀机理与效果，提出并完善了激光空化强化机制。