Development of the pressure-time method as a relative and absolute method for low-head hydraulic machines
2013 (English)Conference paper, Presentation (Refereed)
The pressure-time method is an absolute method common for flow measurements in power plants. The method determines the flow rate by measuring the pressure and estimating the losses between two sections in the penstock during a closure of the guide vanes. The method has limitations according to the IEC41 standard, which makes it difficult to use at Swedish plants where the head is generally low. This means that there is limited experience/knowledge in Sweden on this method, where the Winter-Kennedy is usually used. The present work presents pressure-time measurements (with L=5 m) performed on a 10 MW Kaplan turbine compared to transit-time flow measurements. A new formulation taking into account the unsteady losses allows a better estimation of the flow rate, up to 0.3%, in the performed experiments. As an alternative to the Winter-Kennedy widely used in Sweden, the pressure-time method was tested as a relative method by measuring the pressure between the free surface and a section in the penstock without knowing the exact geometry, i.e., pipe factor. Such measurements may be simple to perform as most of the inlet spiral casings have pressure taps. Furthermore, the viscous losses do not need to be accurately determined as long as they are handled similarly between the measurements. The pressure-time method may thus become an alternative to the Winter-Kennedy.
Place, publisher, year, edition, pages
Research subject Fluid Mechanics
IdentifiersURN: urn:nbn:se:ltu:diva-37421Local ID: b72130eb-34d4-4fcf-8301-7019bbbd0da4OAI: oai:DiVA.org:ltu-37421DiVA: diva2:1010919
Hydro 2013 : International Conference and Exhebition : Promoting the Versalite Role of Hydro 07/10/2013 - 09/10/2013
Godkänd; 2013; 20131009 (cervante)2016-10-032016-10-03Bibliographically approved