Understanding and Mitigating Water Droplet Impingement Erosion

了解和减轻水滴冲击侵蚀

• 批准号: RGPIN-2018-06789
• 负责人: Medraj, Mamoun
• 金额: $ 3.35万
• 依托单位: Concordia University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=714445
• 关键词: Understanding; Mitigating; Water; Droplet; Impingement

Water droplet impingement erosion (WDIE) is caused by high speed collision between water droplets and solid surfaces. This phenomenon is encountered in gas and steam turbines, helicopters, and jet engines. Although large efforts have been performed to address this problem, the WDIE process is still not well understood because these efforts have been mostly directed towards studying the water droplets or the solid material separately. However, in order to understand this phenomenon, the water droplets and the solid surface should be considered at the same time. Therefore, this will be attempted in this project through combining experimental studies with numerical modeling. To date, it is not easy to accurately relate the WDIE lab test results to the in-service blade life. What makes things more complicated is the difficulty in comparing WDIE results obtained by different groups using different rigs. Direct comparison is very difficult because of different design and testing conditions. This makes the large data produced by different labs not useful for the industry. For example, in the literature some data is reported in terms of time of exposure without accurate account of the actual amount of droplets impacting the solid surface. Other papers report material loss versus number of rotations of the solid sample which again does not take into account the actual number of droplets and their size distribution. In this work we will develop a more representative method that will enable comparing results obtained using different rigs. This will also help the industry in relating the lab test results to the actual blades life. Large number of researchers tried to explain WDIE as a fatigue process. Nevertheless, three processes that are known to improve fatigue performance have been studied by the applicant's group. These are laser shock peening (LSP), low plasticity burnishing (LPB) and ultrasonic nanocrystalline surface modification (UNSM). The choice of these processes was because each one modifies the surface through different attributes that result in improving the fatigue life. While all the three result in deep and high compressive residual stresses, LPB causes surface hardening but without any noticeable microstructural changes unlike the UNSM process. Among these processes, only UNSM causes noticeable WDIE improvement in Ti64 alloy. This means that fatigue mechanism is not the only dominating damage mechanism in WDIE. This also suggests that for improving WDIE resistance, a synergy between compressive residual stress, microstructural changes and surface hardening is required. We would like to further understand the underlying damage mechanisms at different WDIE stages. For instance, to understand the combined effect of residual stresses and microstructural changes, WDIE performance of LPB-treated 17-4PH stainless steel will be studied because it does not show significant strain hardening.

水滴冲击腐蚀是水滴与固体表面高速碰撞而产生的一种腐蚀现象。这种现象在燃气和蒸汽涡轮机、直升机和喷气发动机中遇到。虽然已经进行了大量的努力来解决这个问题，但WDIE过程仍然没有得到很好的理解，因为这些努力主要是针对分别研究水滴或固体材料。然而，为了理解这种现象，水滴和固体表面应同时考虑。因此，这将是尝试在这个项目中，通过结合实验研究和数值模拟。 到目前为止，还不容易准确地将WDIE实验室测试结果与叶片的使用寿命联系起来。使事情变得更加复杂的是，难以比较不同小组使用不同钻机获得的WDIE结果。由于设计和测试条件不同，直接比较非常困难。这使得不同实验室产生的大量数据对行业没有用处。例如，在文献中，一些数据是以暴露时间的形式报告的，而没有准确地说明撞击固体表面的液滴的实际量。其他论文报道了固体样品的材料损失与旋转次数的关系，同样没有考虑液滴的实际数量及其尺寸分布。在这项工作中，我们将开发一个更具代表性的方法，将能够比较使用不同的钻机获得的结果。这也将有助于行业将实验室测试结果与实际叶片寿命联系起来。 大量的研究人员试图将WDIE解释为疲劳过程。尽管如此，申请人的小组已经研究了三种已知的改善疲劳性能的方法。它们是激光冲击强化（LSP）、低塑性抛光（LPB）和超声纳米晶表面改性（UNSM）。选择这些工艺是因为每种工艺都通过不同的属性来修改表面，从而提高疲劳寿命。虽然这三种工艺都会产生深度和高的压缩残余应力，但LPB会导致表面硬化，但与UNSM工艺不同，没有任何明显的微观结构变化。在这些工艺中，只有UNSM在Ti64合金中引起显著的WDIE改善。这意味着疲劳机制不是WDIE中唯一的主导损伤机制。这也表明，为了提高抗WDIE性，需要压缩残余应力、微观结构变化和表面硬化之间的协同作用。我们希望进一步了解不同WDIE阶段的潜在损伤机制。例如，为了了解残余应力和微观结构变化的综合效应，将研究LPB处理的17-4PH不锈钢的WDIE性能，因为它没有显示出显著的应变硬化。