Aeration of hydraulic turbines to increase downstream dissolved oxygen concentration

溶解氧浓度在水地球化学循环和水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站水库中的热分层，抑制混合，并导致水库的浅水层中的沃茨脱氧。利用涡轮机在深度抽水的水力发电导致下游水流中的低溶解氧，对下游河流生态系统产生负面影响。 法律（加拿大，美国和其他地方）现在要求满足溶解氧浓度的最低限度。利用气泡流对气流进行再充气的技术方法是一种解决方案，它还可以减少部分负荷涡轮机运行时的振动，随着可再生能源被送入电网，部分负荷涡轮机越来越多地用于平衡间歇性负荷。最好采用改造技术，使水流重新通气，因为它们对收入流的影响较小。加拿大安德里茨水电公司在约翰H。科尔发电厂，证明了这种改造系统的可行性。在初步探索性合作研究的基础上，本研究的目标是优化手肘偏转器技术，了解尾水管流中抽吸气泡群的两相流的物理过程，并量化随后氧气溶解到气流中。 试验台上的实验将提供物理模型结果，以检查设计参数对两相流中气泡群动力学的影响、氧气传输速率和尺度效应，并建立相似律。研究结果随后将用于支持开发一个计算模型，以预测原型操作。该项目将受益于加斯金教授15年的水电水力学研发经验。 加拿大安德里茨水电将自己定位为水电项目的领导者，在这些项目中，低溶解氧的环境影响很重要（气候温暖的国家，如美国，西班牙），能够保证满足（或超过）溶解氧的监管要求，同时优化涡轮机性能。

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.