The paper reviews recent research and development activities in the field of hydropower technology. It covers emerging and advanced technologies to mitigate flow instabilities (active and passive ...approach) as well as emerging magneto-rheological control techniques. Recent research findings on flow instabilities are also presented, especially concerning fluid-structure interaction and transient operating conditions. As a great number of the existing large-scale hydroelectric facilities were constructed decades ago using technologies that are now considered obsolete, technologies to achieve the digitalisation of hydropower are also analysed. Advances in the electro-mechanical components and generator design are presented; their potential role to adapt hydropower to the current operating conditions is also highlighted. The text explores current efforts to advance hydropower operation, mainly in terms of European projects. It provides a detailed overview of the recent efforts to increase the operational range of hydraulic turbines in order to reach exceptional levels of flexibility, a topic of several recent research projects. Variable speed hydropower generation and its application in pumped storage power plants are presented in detail. Moreover, revolutionary concepts for hydroelectric energy storage are also presented with the analysis focusing on underwater hydro storage and hydropower's hybridisation with fast energy storage systems. Efforts to minimise hydropower's environmental footprint are also presented via the utilisation of small-scale and fish-friendly installations.
•Recent research and development activities in the field of hydropower technology are reviewed.•Novel concepts of hydropower energy storage are presented.•The perspective of the digitalisation of existing and new hydropower stations is analysed.•Fish-friendly, environmental-friendly and small-scale hydropower solutions are outlined.
The paper focuses on the influence of the reshaped elbow geometry of the draft tube on the unsteady pressure field under different operating conditions. The experimental investigations are conducted ...considering two simplified geometrical configurations of the draft tubes with sharp heel elbow and modified/reshaped elbow, respectively. The discriminated power spectra (rotating and plunging components) of the acquired pressure signals on the wall are determined on five levels for seven operating conditions to quantify the influence of the reshaped elbow. The influence of the reshaped elbow on the fundamental frequencies of both rotating and plunging components and on the amplitude of the rotating component is negligible. In contrast, the equivalent amplitude associated with the root mean square of the plunging power spectrum that propagates along the hydraulic passage is mitigated up to 25% by the reshaped geometry of the elbow. The equivalent amplitude on the narrow band around the fundamental frequency of the plunging component is diminished with 40–50% by reshaping the elbow geometry of the simplified draft tube.
Water hammer influences the life cycle of hydraulic passages and may even cause catastrophic structural failures. Several catastrophic failures of hydraulic power units have been reported in the ...literature due to the effects of transient regimes. The objective of the study is to highlight the global trend in water hammer assessment and to quantify the effect of factors influencing overpressure in hydraulic passages during load rejection in different hydropower plants. A brief and concise literature review is conducted to document the parameters associated with the water hammer phenomenon and to thereby identify the necessary prerequisites to validate theoretical and numerical results against experimental data. The purpose of the analysis is to identify extreme transient loads on hydraulic passages in order to properly adapt hydropower unit operation, to make recommendations for design and industry, and to guide the progress of adapted models and numerical simulations to capture complex phenomena. Empirical correlations are determined based on the experimental data that are transferable from one unit to another, even if a deep flow analysis is performed. The experimental results confirm that the rapid closure rate of the guide vanes has a significant impact on the phenomenon. A third order polynomial equation is applied to capture the general overpressure trends. Equation parameters change from case to case depending on the type of hydraulic power unit, closing rate and the type of hydraulic passage. The results confirm also that overpressure values depend significantly on other factors, some of which are not usually taken into account (e.g., runner speed). Experimental correlations make it possible to understand the water hammer phenomenon, which could help not just assessing and optimizing loads, but also verifying and validating more complex physical models, to ensure that hydraulic passages are reliable. A well-documented analysis also makes it possible to optimize equipment design, improve and adapt maintenance programs and to recommend appropriate operating parameters to increase equipment lifespan, while preventing incidents.
The present paper introduces the creation of an algorithm and the software used to determine the energetic performance and monitor the efficiency of hydraulic pumps working in various industrial ...applications, such as water supply systems, water treatment processes, and irrigation systems, particularly in the cases where there is no permanent monitoring. Our field investigations and the surveyed literature show that the only parameter that is neither monitored nor computed is the efficiency of the pumps. The software implementation allows for determining the in-service efficiency of the pumps and comparing it to the value associated with the best efficiency point (BEP). The solution is user-friendly and can be easily installed on any computer or smartphone. The software has been applied and tested in the Hydraulic Machines Laboratory at the “Politehnica” University Timişoara and at the AQUATIM S.A. regional water supply company. The software module monitors the operating regimes of the pumps and supports the deployment of predictive maintenance and servicing.
•There is a hidden energy potential in existing hydropower plants, and this was assessed for Europe.•Heat recovery from generators can reach 5 TWh/y, and can be used either for powerhouse heating or ...for district heating.•The harvesting of the tailrace water energy can increase European generation by 0.43 %, equivalent to thousands of micro hydropower plants 100 kW each.•Capturing degassing methane can increase sustainability, but more R&D is necessary.
Hydropower is the giant of the renewable energy sector, and a well-established source of energy. In order to reduce the impacts of new barriers in rivers, the retrofitting of existing facilities with new technologies is deserving a great attention, especially when hydropower technologies are hybridized with other energy devices. In this study a European-scale assessment is carried out to quantify the potential associated to the exploitation of the excess (and wasted) energy sources in existing hydropower facilities. Three sources of energy are assessed: 1) the hydrokinetic energy of the tailrace water flow and the potential energy associated to the unexploited head below Pelton units, 2) the thermal energy of the cooling system of the electric generators and 3) the chemical energy of the degassing methane. Considering the available technology, 5.0 TWh/y of heat could be generated by exploiting the thermal energy of the cooling system. 2.4 TWh/y of electricity could be generated by harnessing the hydrokinetic energy at the tailrace; this would correspond to thousands of micro hydropower plants 100 kW each), and would avoid new installations in natural freshwater systems. Degassing methane is relevant at the global scale, especially in tropical reservoirs. In Europe 5,950 tons/year of degassing methane could be theoretically captured, since minor methane emissions from reservoirs occur. R&D activities are ongoing to overcome the current technological limitations and high installation costs. Different novelties are included in this study: for the first time, a continental assessment is carried out on this topic, establishing methodologies that could be implemented at any regional scale. For each technology, a literature review is carried out to collect data and case studies. Data to estimate the number of units and the operating range of Francis, Kaplan and Pelton turbines in Europe, and equations to estimate the degassing methane emissions, are provided. These data can be used for similar large scale assessments.
In this paper, we introduce a novel passive control method to mitigate the unsteadiness effects associated to the swirling flows with self-induced instabilities. The control method involves a ...progressive throttling cross-section flow at the outlet of the conical diffuser. It adjusts the cross-section area with a diaphragm while maintaining all positions of the circular shape centered on the axis. It improves the pressure recovery on the cone wall while the pressure fluctuations associated with the self-induced instability are mitigated as it adjusts the cross-section area. It can adjust the diaphragm in correlation with the operating conditions of the turbine. We investigated the passive control method on a swirl generator, which provides a similar flow as a hydraulic turbine operated at a partial discharge. The plunging and rotating components are discriminated using the pressure fluctuation on the cone wall to provide a clear view of the effects induced by this passive control method. As a result, the novel proof of concept examined in this paper offers valuable benefits as it fulfils a good balance between the dynamical behavior and the hydraulic losses.
Integrity Analysis of the Rainwater Pump Impeller Galatanu, Sergiu-Valentin; Muntean, Sebastian; Marsavina, Liviu ...
MATEC Web of Conferences,
01/2018, Letnik:
188
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The purpose of this paper is to examine the failure problems encountered during the operation of the rainwater pump impellers installed in a wastewater station. The rainwater pumps are specially ...designed to operate in wastewater plants. The fibbers and wastes are discharged together with rainwater during storms with this type of pumps to avoid the flood of the wastewater station. Several problems have occurred in service due to the fibbers clog the gap between the impeller blades and the pump casing. The analysis of the catastrophic events associated to the rainwater pumps installed in a wastewater station is performed. As a result, it has been identified that the catastrophic events are due to the brittle fracture of the fasten bolts connecting the impeller blades and the pump hub, respectively. Analytical and numerical analysis were perform in order to determine the maximum shear stress on the fasten bolts. As a conclusion the partial clogging of the gap between one impeller blade and pump casing, inducing the lock of the blade and leading to catastrophic failure.
This paper introduces a numerical methodology based on a 3D turbulent flow computation developed to assess the aerodynamic performances of lumber drying kilns. The numerical results are validated ...against experimental data obtained by applying five different fan speeds and reversible air flow. The distributions of the energy loss coefficient and of the non-uniformity flow coefficient were plotted along the flow path in both normal and reverse directions and the regions with larger air loss values were identified. The numerical computation revealed that three quarters of the airfl ow delivered by the fans bypasses the wood stacks through different gaps, consequently leading to a low aerodynamic effi ciency (of 24-25 %) of the kiln.
The key ingredient for any turbine runners design procedure and failure analysis is the material and its mechanical and fatigue properties. Starting from this observation, a series of static and ...dynamic tests were performed on the T10CuNiCr180 stainless steel after more than three decades of service. The fatigue tests were carried out under constant amplitude at a stress ratio of 0.1 and a frequency of 20 Hz. In the high cycle fatigue range, the S-N median curve was plotted and the fatigue limit for 3106 cycles to failure was determined at 93.35 MPa expressed in stress amplitude. The casting and welding defects that were observed on fracture surfaces explained this lower fatigue limit. The fatigue crack growth tests were performed on compact tension specimens and a three-parameter model was used to plot the crack length versus number of cycles curves. In addition, the material constants from Paris law were determined. Finally, the experimental results are compared against published data for another stainless steel.
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