Aeration of hydraulic turbines to increase downstream dissolved oxygen concentration

溶解氧浓度在生物地球化学循环和水生生态系统功能中起着至关重要的作用。在温暖的气候条件下，温暖的温度导致水电水库热分层，抑制混合，导致水库低阴离子水脱氧。水轮机深层抽水发电导致下游水流溶解氧低，对下游河流生态系统产生负面影响。立法（加拿大、美国和其他地方）现在要求溶解氧浓度达到最低限度。利用气泡流对水流进行再充气的技术方法是一种解决方案，也可以减少部分负荷涡轮机运行时的振动，随着可再生能源进入电网，这种振动越来越多地用于平衡间歇性负荷。再曝气的改造技术是首选，因为它们对收入流的影响较小。Andritz Hydro Canada公司在John H. Kerr电厂使用弯头偏转器实现了首个尾水管曝气原型之一，证明了该改造系统的可行性。在初步探索性合作研究的基础上，本研究旨在优化弯头导流板技术，了解尾流管中吸入气泡群两相流的物理过程，并量化随后氧气在流中的溶解。在试验台上进行的实验将提供物理模型结果，以检验设计参数对两相流中气泡群动力学、氧转移速率和尺度效应的影响，并开发相似定律。结果将随后用于支持计算模型的开发，以预测原型操作。该项目将受益于Gaskin教授在水电液压方面15年的研发经验。Andritz Hydro Canada将把自己定位为水电项目的领导者，在这些项目中，低溶解氧对环境的影响很重要（气候温暖的国家，如美国、西班牙），能够保证在优化涡轮机性能的同时满足（或超过）溶解氧的监管要求。

The concentration of dissolved oxygen plays a vital role in biogeochemical cycling and in aquatic ecosystem function. In warm climates, warm temperatures cause thermal stratification in hydropower reservoirs inhibiting mixing and leading to deoxygenation of waters in the hypolimnion of the reservoir. Hydropower generation with turbines withdrawing water at depth results in low dissolved oxygen in the downstream flow negatively impacting the downstream riverine ecosystem. Legislation (Canada, USA and elsewhere) now requires minimum limits for dissolved oxygen concentration to be met. Technological approaches to re-aerate the flow with bubble streams is a solution that also reduces vibrations at part-load turbine operation increasingly used to balance intermittent loads as renewables are fed into the grid. Retrofit technologies to re-aerate flows are preferred, as they have smaller impacts on revenue streams. Andritz Hydro Canada implemented one of the first prototypes of draft tube aeration using elbow deflectors at the John H. Kerr power plant, demonstrating the viability of this retro-fit system. Building on an initial exploratory collaborative study, in this study we aim to optimize the elbow deflector technology, understand the physical processes of the two-phase flow of the aspirated bubble swarm in the draft tube flow and quantify the subsequent dissolution of oxygen into the flow. Experiments on a test rig will provide physical model results to examine the effect of design parameters on the bubble swarm dynamics in the two-phase flow, the rate of oxygen transfer and scale effects and to develop similitude laws. The results will be subsequently used to support development of a computational model to predict prototype operations. The project will benefit from the 15 years of experience in R&D of hydropower hydraulics of Prof. Gaskin. Andritz Hydro Canada will position itself as a leader for hydropower projects, in which environmental impacts of low dissolved oxygen are important (countries with warm climates, e.g. USA, Spain), able to guarantee meeting (or exceeding) the regulatory requirements for dissolved oxygen while optimizing turbine performance.