Disputation – Shahab Shiraghaee

Water flowing through a hydro dam

Shahab Shiraghaee på LTU disputerar med avhandlingen: Experimental Investigation and Mitigation of Part-load Pressure Pulsations in Hydro Turbines Using Solid-body Protrusion inside the Draft Tube.

The work of Shahab Shiraghaee aims to introduce and investigate the concept of protrusion-based methods to mitigate part load pressure pulsations. The latter is attempted by perturbing the flow in the turbine with the radial insertion of solid bodies into the draft tube. The proposed geometries include cylindrical rods and flat plates. The impact of cylindrical rods has been examined on multiple scales of axial turbines, including a downscaled model turbine, a model turbine, and a prototype. These effects were observed with different measurement tools depending on the investigated turbine. The obtained results presented in this work for rod protrusion experiments include turbine operation parameters, time-resolved pressure data, strain data, flow visualization, and efficiency. As an improvement to the rod protrusion concept, the flat plates were tested on the downscaled model turbine.

The obtained mitigation rates under these conditions reached as high as 80%. In addition, this method proved effective in reducing flow induced fatigue at lower PL and even speed-no-load (SNL) conditions. However, rod protrusion entailed mixed results under the PL conditions where the RVR induced the strongest periodic oscillations. Moreover, the rods caused a maximum efficiency drop of approximately 3% of the BEP efficiency. More importantly, for all the investigated scales, under the conditions where the rods appeared effective, an optimum protrusion length was found where the most significant mitigation occurred. On the other hand, the investigation of plates on the downscaled model showed complete mitigation of the RVR-induced pressure pulsations under the entire turbine PL range, and the turbine efficiency was even improved under lower PL conditions.

• Dag: 18 juni 2024
• Tid: 09.00-11.30
•  https://ltu-se.zoom.us/j/69596626588

Läs doktorsavhandlingen: Experimental Investigation and Mitigation of Part-load Pressure Pulsations in Hydro Turbines Using Solid-body Protrusion inside the Draft Tube