Velocity field and discharge measurements at the turbine inlet of Iron Gate 2 hydropower plant

<p>To define the performance characteristics of turbines in Hydropower Plants (HPP) accurate hydraulic, mechanical and electrical quantities are needed. The discharge is the most difficult quantity to measure and assess its uncertainty (Adamkowski, 2012). Traditionally, during field acceptance tests the discharge is measured using velocity-area method. Often, no direct flow measurements are possible and only index methods are used, with flow coefficients obtained during physical model testing. In the non-standard situations, with adverse flow conditions this may lead to unpredicted flow uncertainty.</p><p>             The system used at the Iron Gate 2 HPP for control flow measurement at the inlet of bulb turbine is presented in this paper. The HPP is situated on a Danube river, between Serbia and Romania and is operational from 1985. The HPP is equipped with 20 horizontal Kaplan low head bulb turbines. The physical model experiments (JČInstitute, 2006) have concluded that due to the upstream flow conditions, the incident water flow direction is not parallel to the turbines (depending on operating conditions and can be up to 40<sup>o</sup>) as was assumed during the turbine’s model tests, raising the question of used Winter-Kennedy’s method accuracy.</p><p>             To perform a control flow measurement, a modular velocity-area system was designed. The system can be installed at the intake of any turbine, upstream of the trash rack. It consists of the 14.5x3.1 m steel frame, shaped to minimize flow disturbances, which can be traversed vertically through the flow cross section (28 m). Due to the high incident angles and large vortices in the front of the trash rack, propeller current meters were not suitable. The novel spherical 3D electromagnetic velocity meter (EMVM) was developed (Svet Instrumenata), enabling fast and continuous measurements of all the velocity vector components, with low flow disturbance. The 15 EMVMs were mounted on the frame and connected into the measurement network. Redundant velocity measurement was done using 2 Nortek “Vector” ADVs (Nortek). The measurement network also comprises of 2 water level pressure transducers and 2 steel frame position transducers (UniMeasure). All measurements were synchronized with HPP’s SCADA, so turbine’s operational parameters were downloaded off-line and merged.</p><p>             During the 2020, measurement system was used on the two turbines. The velocity profile was measured using two strategies: incrementally, the steel frame was raised from the bottom (average depth of 26 m) in increments of ~1.0 m and kept for at least 10 min in fixed position, and continuous where the steel frame was traversed through the flow cross-section with a constant speed of 0.05 m/s. Uncertainty assessment procedure, specifically tailored for this application, yielded discharge measurement uncertainties between 1.02 % and 2.00 %  for incremental, and between 1.65 % to 2.79 % for continuous regime.</p><p>References</p><p>Adamkowski, A. (2012). Discharge measurement techniques in hydropower systems with emphasis on the pressure-time method. Hydropower-practice and application.</p><p>Jaroslav Černi Institute (2006). Scale model investigation of turbine runner inflow at an unfavorable angle at HPP „Đerdap II“, SDHI (in Serbian)</p><p>NORTEK: https://www.nortekgroup.com/products/vector-300-m</p><p>Svet Instrumenata: http://www.si.co.rs/index-e.html</p><p>UniMeasure: https://unimeasure.com/wp-content/uploads/2019/12/HX-EP-SERIES-CATALOG-PAGES-1.pdf</p>

Vertical Velocity Profile on the Noncircular Flow Cross-Section of Water Intake Pipeline with Deposition on Bottom

Under small water-intake flow or overhaul periods, sediments deposit in the water intake pipeline with noncircular flow cross-section formed. According to the hydrostatic settling test results of fine sediments in circular pipeline, the sectional features of the deposition on pipe bottom is provided. And the vertical velocity profiles on perpendicular bisectors of noncircular flow cross-sections are measured under three kinds of typical deposition thickness. The relative positions of the maximum velocity point and the center of flow cross-section should be determined with an overall consideration to the two factors of wall roughness and wall restraint which is controlled by the transverse width of flow cross-section. When the mean velocity of flow cross-section keeps a constant value, the larger the deposition thickness is, the larger the velocity near the deposition surface, which is more favorable for sediment incipient motion.

Reconstruction of the Flow Cross-Section Temperature Based on the Radiation Balance Between Infinitesimal

The reconstruction of three-dimensional temperature field is a difficult problem. But three-dimensional temperature measurement can be simplified by the reconstruction of the flow cross-section temperature. In this paper, a theory of reconstruction is proposed and a simulation test system is implemented by MATLAB based on emission spectra tomography (EST) and radiation temperature measurement, which also take the emission and absorption characteristics in the processing of radiative transfer under consideration. Finally, by analyzing the difference of the original temperature and reconstructed temperature we can get the accuracy of the reconstruction theory.