A novel energy losses dependence on integral swirl flow parameters in an elbow draft tube of a Kaplan turbine

• Published in: Renewable energy 2021-09, Vol.175, p.550-558
• Main Author: Božić, Ivan
• Format: Article
• Language: English
• Subjects: Elbow draft tube; Hydraulic losses; Kaplan turbine; Swirl flow
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/j.renene.2021.05.014

Energy losses in the region between the runner and outlet section of a conventional hydraulic turbine have been the subject of investigation for a long time. In this paper as well, elbow draft tube losses are determined for the relevant wide range on-cam operating modes of the Kaplan turbine using a contemporary approach. The research considers the impact of swirl flow parameters, defined for the referent inlet of the draft tube, on the hydraulic losses. According to the methodology and obtained numerical results, a new formula for the calculation of draft tube losses is proposed. In the process of a hydropower plant refurbishment, the presented approach may enable more efficient and economically justified consideration of the performance improvement of the entire double regulated hydraulic turbine, especially in the case of keeping the existing elbow draft tube. •Energy losses in an elbow draft tube have impacts on the overall efficiency of a Kaplan turbine.•Complex swirl flow induces various dissipative phenomena in curvilinear draft tube configuration.•Energy losses dependence on the integral swirl flow parameters is researched.•The novel analytic relation between the losses and the inlet swirl flow parameters is proposed.•The presented approach is efficient, applicable and economically justified during hydropower plant refurbishment.