Hydraulic Energy Research Articles

Solution of unstable problem for hydraulic turbine in order to promote usage of hydraulic energy

Hydraulic power generation is one of the most commonly used electric power generation by renewable energy. It is necessary to solve some practical and operational problems relating to hydraulic power plant in order to spread usage of hydraulic power generation. S-shape characteristics, which is one of unstable problems in hydraulic power plant, should be solved for designing of hydraulic turbines. It is important for numerical flow simulation to predict the S-shape curve with high accuracy, because a lot of design ideas to prevent the S-shape characteristic curve can be generated by analysis of numerical results of flow patterns. In this research, Francis turbine with low specific speed was simulated by steady and unsteady analysis in two cases, such as guide vane opening of 100% and 40%. Numerical results of turbine head and torque agreed well with experimental ones at guide vane opening of 100%. In case of guide vane opening of 40%, the simulation predicted successfully an increase of head which appeared in the experimental result. As the result, S-shape appears in a numerical characteristic curve similarly to the experimental one. The guide vane opening of 100% had a small backward flow in a radial velocity at the chamber between guide vanes and runner blades. On the other hand, the opening of 40% had two different flow patterns in first half and last half of the S-shape characteristics curve. In first half, there are almost no back flow in radial velocity at the chamber between guide vanes and runner blades. In last half of S-shape characteristics, a stable vortex flow which contained two forward flows in crown and band side, and a backward flow in the middle region between crown and band appears. The runner torque changed to be minus when the backward flow appeared, and the minus torque means that the runner gave kinematic energy to the water. The water with high energy was transported to the upstream guide vane by the back flow and this flow patterns caused the head increase. And this head increase caused the S-shape character in characteristic curve of guide vane opening of 40%.

Quantitative response of riverine benthic invertebrates to sediment grain size and shear stress

The most widespread pressure impacting river ecological status is the degradation of key hydromorphologic elements, such as sediment type and flow rate. However, almost nothing is known about the quantitative relationship between benthic invertebrate abundance and these elements. This synthesis compiles quantitative data on physical requirements and thresholds for invertebrates relative to two hydromorphologic factors: substrate size and hydraulic energy (measured as shear stress). Both factors are commonly a focus of river rehabilitation. However, we found only limited literature data that we could use to identify invertebrate preferences (189 taxa). Preferred substrate sizes of all stream epifauna we examined varied between 0.05 and 400 mm and they prefer shear stresses from 0.13 to 3.67 N m−2. There was no difference in variation of preferred conditions between the examined taxonomic levels. We suspect that taxa preferring hydraulic environments with shear stresses < 0.64 N m−2 are affected more by environmental factors than solely being constrained by substrate or hydraulic energy preferences. Such taxa might be useful as sensitive indicator species for evaluating stream integrity. Hence, to optimize restoration success for riverine biota, hydromorphological forces should be mitigated by manipulating habitat complexity in a way that it enhances intact ecological processes.

Thermodynamic analysis of energy dissipation and unsteady flow characteristic in a centrifugal dredge pump under over-load conditions

The present paper aims to investigate the energy dissipation related to unsteady flow phenomena inside a three-bladed impeller of a centrifugal dredge pump under over-load operating conditions. Three-dimensional unsteady numerical simulations of the centrifugal pump are performed by adopting the SAS SST-curvature correction turbulence model with the total energy equation. The simulating results are verified by comparing the performance results and pressure fluctuation with available experimental data. The unsteady flow patterns and energy dissipation in the rotating impeller are analysed by entropy distribution and pressure fluctuation spectra. A high-entropy area appears in the impeller flow passage when the discharge increases. It is indicated in the unsteady simulation results that a vortex flow with high entropy generates and detaches periodically, which causes the hydraulic energy loss under over-load operating conditions. In numerical simulations, a frequency as 3.3 times of rotating frequency is found in the pressure spectral analysis at 1.45 Q0 operating condition, which is related to the unsteady flow structure. The secondary flow near the volute tongue is found at 1.45 Q0 operating condition due to the large angle of attack when discharge increases.

Decentralized water supply by reservoir network reduces power demand for water distribution in a semi-arid basin

ABSTRACTIn the Brazilian semi-arid region, thousands of small dams have been built over time to enhance water availability, accumulating water and hydraulic energy at high altitudes. Simulations were performed in this study to assess how the arrangement of reservoirs impacts on the power demand for water distribution in the Banabuiú River Basin (19 800 km2), Brazil. The power required to pump water from 1405 reservoirs to all districts with diffuse demands is 6.5 GWh/year, whereas in the scenario with only the 12 larger strategic reservoirs, the power demand reached 45.3 GWh/year. Alone, the largest reservoir in the basin can supply water to all districts. Nonetheless, in that scenario, the power demand would reach 195 GWh/year, which is 30 times the power required in the real reservoir arrangement. Thus, decentralization by small reservoirs not only promotes more democratic access to water, but also increases energy efficiency by storing it at higher altitudes and closer to the diffuse demands.

Hydraulic performance and energy dissipation effect of pit structure flow channel emitter

In this paper, a drip irrigation emitter with new pit flow channels such as shunt, sharp turn, and confluence was constructed by the pit structure in the water transporting tracheid of bionic plant xylem. In order to study the hydraulic performance and energy dissipation effect of the pit flow channel, the geometric parameters of the pit flow channel were combined by simulation prediction and orthogonal test. The 25 sets of test schemes were carried out to test the hydraulic characteristics, and the Bernoulli equation was used to solve the structural loss coefficient. At the same time, the orthogonal test results were analyzed by the range and variance, and the regression model of geometric parameters and flow index was established. The results showed that the flow index of the emitter was 0.462~0.496, and its hydraulic performance was good. The structural loss coefficient under the pressure head of 5~25 m was 2120~6321, which showed that the energy dissipation effect was obvious. The order of influence of each geometric parameter on the flow regime was T>B>S>D>A, and the optimal scheme was T0.18B2.2S2.2D0.2A4. The regression coefficient of the model was significant. The value of the F statistic was 16.670, corresponding to the significance level Sig.=0<0.05, and the error of the experimental and simulated values of the flow index was less than 5%, which proved the accuracy and reliability of the regression model. This paper provides a new idea for agricultural drip irrigation control technology.

HydroShoot: a functional-structural plant model for simulating hydraulic structure, gas and energy exchange dynamics of complex plant canopies under water deficit—application to grapevine (Vitis vinifera)

AbstractThis paper presents HydroShoot, a leaf-based functional-structural plant model (FSPM) that simulates gas exchange rates of complex plant canopies under water deficit conditions. HydroShoot is built assuming that simulating both the hydraulic structure of the shoot together with the energy budget of individual leaves is the asset for successfully scaling-up leaf to canopy gas exchange rates. HydroShoot includes three interacting modules: hydraulic, which calculates the distribution of xylem water potential across shoot hydraulic segments; energy, which calculates the complete energy budget of individual leaves; and exchange, which calculates net carbon assimilation and transpiration rates of individual leaves. HydroShoot was evaluated on virtual and real grapevines having strongly contrasted canopies, under well-watered and water deficit conditions. It captured accurately the impact of canopy architecture and soil water status on plant-scale gas exchange rates and leaf-scale temperature and water potential. Both shoot hydraulic structure and leaf energy budget simulations were, as postulated, required to adequately scaling-up leaf to canopy gas exchange rates. Notwithstanding, simulating shoot hydraulic structure was found more necessary to adequately performing this scaling task than simulating leaf energy budget. That is, the intra-canopy variability of leaf water potential was a better predictor of the reduction of whole plant gas exchange rates under water deficit than the intra-canopy variability of leaf temperature. We conclude that simulating the shoot hydraulic structure is a prerequisite if FSPMs are to be used to assess gas exchange rates of complex plant canopies as those of grapevines. Finally, HydroShoot is available through the OpenAlea platform (https://github.com/openalea/hydroshoot) as a set of reusable modules.

Hydraulic properties and energy dissipation of deep hard rock under H-M coupling and cycling loads

The permeability of deep rock is closely related to the stability and safety of underground engineering. The rocks in deep stratum are mostly with high stress and high osmotic pressure. Therefore, it is necessary to consider the coupling effect between porewater pressure and in situ stress on rock mass. A series of triaxial cyclic loading and unloading experiments under hydraulic-mechanics coupling conditions are carried out to studied the mechanical and hydraulic properties of granite in the depth of 1300 m to 1500 m. Especially, the effect of the disturbance on the permeability of fractured rocks are investigated by unloaded the confining pressure. Tests results presented that the stress-strain curves of deep granite showed typical brittle characteristics. The principal stress of granite exhibited a linear relationship under the high confining pressure of 34-40 MPa and high osmotic pressure of 13-15 MPa. Dissipated energy of the rock decreased to a relatively low level after 2-3 loading cycles and then slowly increased. Permeability showed a decreasing trend as the loading and unloading cycles increase. Finally, acoustic emission technology was used to monitor the fracture evolution in rocks, the acoustic emission signal released as the fractures develop and energy dissipated. The results would provide basic data for the exploitation and excavation in the deep galleries.

Construction proposal of hydraulic equipment designed to test hydraulic components and energy carriers

The aim of the present article is the construction of a device for measuring and testing hydrostatic converters and subsequent verification measurement of the proposed device. This device will allow the measurement and testing of hydraulic pumps under laboratory conditions. In our case, we will test the hydraulic pump UD–25R, which is used in hydraulic drives of agricultural machines. Last but not least, the device described in the article can be used to test individual energy carriers used in hydraulic systems. The described device can simulate conditions that occur in operation. Using verification measurements we have proved that the designed laboratory equipment is suitable for testing hydraulic components and also allows monitoring and testing of the properties of individual hydraulic fluids. The measurement will result in a change in flow rate over time.

Self-Tuning Control Techniques for Wind Turbine and Hydroelectric Plant Systems

The interest on the use of renewable energy resources is increasing, especially towards wind and hydro powers, which should be efficiently converted into electric energy via suitable technology tools. To this aim, self-tuning control techniques represent viable strategies that can be employed for this purpose, due to the features of these nonlinear dynamic processes working over a wide range of operating conditions, driven by stochastic inputs, excitations and disturbances. Some of the considered methods were already verified on wind turbine systems, and important advantages may thus derive from the appropriate implementation of the same control schemes for hydroelectric plants. This represents the key point of the work, which provides some guidelines on the design and the application of these control strategies to these energy conversion systems. In fact, it seems that investigations related with both wind and hydraulic energies present a reduced number of common aspects, thus leading to little exchange and share of possible common points. This consideration is particularly valid with reference to the more established wind area when compared to hydroelectric systems. In this way, this work recalls the models of wind turbine and hydroelectric system, and investigates the application of different control solutions. Another important point of this investigation regards the analysis of the exploited benchmark models, their control objectives, and the development of the control solutions. The working conditions of these energy conversion systems will also be taken into account in order to highlight the reliability and robustness characteristics of the developed control strategies, especially interesting for remote and relatively inaccessible location of many installations.

Oscillation impacter improves the rate of penetration

In order to improve the rate of penetration and drilling performance, a tool named oscillation impacter is designed, which enables hydraulic energy to transform into mechanic one and generate static-and-dynamic loading on the bit and local instantaneous low pressure at the bottom. This paper attempts to analyse the structure and working principle of oscillation impacter, study the rock breaking mechanism of local instantaneous low pressure through theoretical analysis and the rock breaking mechanism of static-and-dynamic loading by the method of numerical simulation. Reasonable working parameters are recommended after analysing the influence that frequency and the maximum amplitude of dynamic loading act on rock breaking. According to the simulation results, corresponding drilling technology is established and field tests are conducted in Huabei oilfield. The statistical results manifest that the performance of oscillation impacter is favourable in different formations and the ROP is improved significantly. [Received: July 6, 2015; Accepted: January 6, 2017]

Development of Wind and Hydraulic Energy Hands-on Activity Task for Contents of 'New and Renewable Energy' of Middle School Technology and Home-Economics Subjec

Development of Wind and Hydraulic Energy Hands-on Activity Task for Contents of 'New and Renewable Energy' of Middle School Technology and Home-Economics Subjec

Influence of Guide Ring on Energy Loss in a Multistage Centrifugal Pump

Multistage centrifugal pumps are highly efficient and compact in structure. Pump efficiency can be improved by an effective understanding of hydraulic behavior and energy loss, however, the traditional hydraulic loss evaluation method does not readily reveal the specific locations of energy loss in the pump. In this study, a guide ring was imposed in multistage pumps, and an entropy production theory was applied to investigate irreversible energy loss of a multistage pump with and without guide ring. Detailed distributions of energy losses in the pumps were calculated to determine the respective entropy production rates (EPRs). The EPR values as calculated are in close accordance with actual hydraulic loss values in the pumps. EPR values were higher in the multistage pump with the guide ring than the pump without a guide ring under part-load flow conditions (0.2Qd). However, the vortex flow in the pump was weakened (or eliminated) by the guide ring as flow rate increased; this reduced energy loss in the chambers. Flow passing the chamber was stabilized by the guide ring, which decreased shock and vortex loss in the chamber and guide vane. Under both designed flow condition and overload conditions, the EPR values of the guide ring-equipped multistage pump were lower than those without the guide ring. Furthermore, minimum efficiency index (MEI) values were also calculated for the two chamber structures; it was found that overall efficiency of pump with guide ring is better than that without.

Buried channels provide keys to infer Quaternary stratigraphic and paleo-environmental changes: A case study from the west coast of India

High resolution shallow seismic data was acquired from inner continental shelf of Goa, west coast of India to map underlying stratigraphic and buried geomorphic features of shelf strata. Seismic data revealed characteristic channel incisions beneath 4–15 m thick sediment layer and corresponds to multi cycle incisions. Stratigraphic analysis of these incision signatures reveals three prominent subaerial unconformities S6, S7 and S9. These unconformities were exposed during the last glacial, penultimate glacial (MIS-6) and prior to penultimate glacial (MIS-8) periods. On the basis of interpreted age of subaerial unconformities and differences in their morphological features, observed channel incisions have been divided grossly into three phases of incision. Phase-1 incisions are older than ∼330 kyr BP, whereas, incisions of Phase-2 and Phase-3 correspond to ∼320–125 kyr BP and ∼115–10 kyr BP respectively. Plan form of these incisions varied from a straight channel type to ingrown meander and then to anastomosing channel types. These channels meet at the confluence of present-day Mandovi and Zuari rivers. The confluence point has varied in due course of time because of cyclic incision and burial with repeated sea level fluctuations. The preserved main channel width varies from ∼100 m to 1000 m, and maximum channel depth reaches up to ∼35 m. Comparison of quantitative and qualitative morphologic results of different phases of incisions suggest that Phase-2 channels had ∼33% more mean bank full discharge than that of the Phase-3 channels. Phase-2 incisions had been carved in higher hydraulic energy condition as compared to Phase-3 incisions implying that the Indian summer monsoon was better during formative stages of Phase-2 incisions.

ВЛИЯНИЕ КОНСТРУКЦИИ КОНТАКТНОГО УСТРОЙСТВА НА ГИДРАВЛИЧЕСКОЕ СОПРОТИВЛЕНИЕ РЕКТИФИКАЦИОННОЙ КОЛОННЫ

ы, клапанные тарелки, ударно-распылительная насадка.&#x0D; Abstract. It is shown that the use of a new highly efficient shock-spray regular packing instead of direct-flow valve plates in the distillation column for the separation of the isopentane fraction&#x0D; will significantly reduce the hydraulic resistance and energy costs. The low hydraulic resistance of the&#x0D; shock-spray packing is explained by its design features: regular layout, high free cross section, low&#x0D; amount of retained fluid

Energy analysis and optimization of main hydraulic system in 10,000 kN fine blanking press with simulation and experimental methods

In this paper, a low-high pressure double oil hydraulic system with accumulators was presented with the features of high working efficiency, high control precision and large working capacity. To analyze the hydraulic system energy characteristic, a novel analytical approach, based on the mathematical energy dissipation model of hydraulic components, was proposed to calculate the system energy dissipation by establishing high accuracy simulation model. A test rig with a 10,000 kN hydraulic fine blanking press was built up and used to validate the proposed system and the energy analytical approach. Finally, the system energy dissipation of the 10,000 kN hydraulic fine blanking press was analyzed and the pump output pressure was optimized to minimize the energy dissipation with the genetic algorithm. Results indicate that the energy efficiency of the hydraulic fine blanking press hydraulic system is low, and especially under low-load conditions it is (0–50% full load rate) less than 15%. About 50% of the total input energy is consumed in the form of valve dissipation resulted from the imbalance of installed and demanded energy. After optimization, the total input energy decreases by nearly 50% and the energy efficiency increases by 10%, especially under low-load conditions.

Energy and exergy analysis of hydraulic free-piston engines

A hydraulic free-piston engine is an unconventional reciprocating piston internal combustion engine in which the piston assembly motion is determined by in-cylinder gas pressure and load force. Fuel combustion energy is directly converted into hydraulic energy. These affect the work process of cylinder and efficiency of energy conversion. In order to study the energy utilization efficiency and to explore the recovery potential of waste heat energy of hydraulic free-piston engine, in this paper, the energy distribution and waste heat energy characteristics of hydraulic free-piston engine have been studied by combining energy and exergy analysis. The thermal efficiency was analyzed by the first law of thermodynamics, and exergy balance was analyzed by the second law. The effect of the characteristic parameters on the thermal and exergy efficiency was studied through the simulation analysis comparing the energy utilization of hydraulic free-piston engine and conventional engines. The results show that control of the injection timing parameter is effective for optimizing efficiency because the cycle characteristic parameters can be controlled by changing the injection timing. The experimental results show that the thermal efficiency is 40.8% and the exergy efficiency is 46.3%. The simulation result show that the thermal efficiency of hydraulic free-piston engine is 38.0% and the conventional diesel engine is 33.0%.

Generation of Photovoltaic Solar Energy. Evaluation of the Demand Curve with the Insert of Grid-connected Photovoltaic Power System at CINDACTA II, Curitiba-PR, Brazil.

ABSTRACT Unlike some countries, Brazil has a predominantly hydraulic energy matrix, a clean and renewable source. But, in recent years, both the non-renewal of the normal volumes of water in the reservoirs and the lack of consciousness in the consumption of water and energy have placed the country in a critical state of energy supply leading to many intensive policies to reduce its consumption. In contrast, energy from Photovoltaic (PV) on-Grid Systems has grown dramatically in recent years. In this sense, this study presents an analysis of the contribution of the energy generated by a PV on-Grid Systems to be installed in CINDACTA II, in order to make re-contracting a lower demand possible and also reduce electric energy consumption and its cost.

Inverse modeling approach for parametric frequency domain analysis of an electrohydraulic system

Abstract This paper presents parametric frequency domain analys.isf an electrohydraulic system, in particular, with respect to the hydraulic supply pressure. The supply pressure is a design parameter of significance such that it affects control bandwidth, load capability and system durability. However, intensive analysis on this parameter has not been reported yet due to the nonlinear dynamic features of an electrohydraulic system. In this paper, the inverse generalized frequency response functions are derived and used to conduct multi-dimensional Fourier analysis of the control input and to investigate its relation to the supply pressure. In addition, the hydraulic energy consumption is analyzed with respect to the supply pressure. The analysis reveals that the supply pressure is a critical design parameter that determines the degree of nonlinearity and trade-off between the control bandwidth and energy consumption.

FLOW MODELLING AND PERFORMANCE ASSESSMENT OF ROTARY SLIDING VANE PUMP USING COMPUTATIONAL FLUID DYNAMICS

A pump is a mechanical device that converts mechanical energy into hydraulic energy. The aim of the current work is to examine the behavior of fluid flow inside a rotary sliding vane pump and assessing the performance by studying the effect of change of the rotational speed, number of vanes and the radial clearance gap size between vane tips and stator surface on the performance of the pump. The commercial finite-volume solver ANSYS Fluent was used to simulate flow behavior in the pump with an additional C source code for the description of the dynamic mesh motion. Pump flow has been studied using lubricating oil, 5W-30, as the working fluid. Several computational configurations were used for the numerical simulation. The numerical results showed that 100% increase of the number vanes decreases the overall efficiency by 46.5%, while increasing the clearance gap size from 0.025 to 0.05 decreases the overall efficiency by 9.72%, and results in a 42.85% increase in the internal leakage within the pump.

Underwater mechanical behavior of closed cell PVC foams under hydrostatic loading through 3D DIC technique

The underwater constitutive behavior of poly vinyl chloride foams with varying densities was investigated in this study. The experiments were conducted in an optically clear acrylic tube, which allowed for visualization of the specimen and the application of 3D Digital Image Correlation. A series of calibration experiments was conducted to investigate the applicability of the Digital Image Correlation technique for measuring the deformation of objects underwater inside of a curved acrylic tube of considerable thickness. The results of the calibration experiments demonstrated that a submerged object located in the middle of the acrylic tube appears magnified in the radial direction. This apparent magnification was taken into account during the analysis of the deformation for all underwater experiments. The hydrostatic loading was achieved by fitting the acrylic tube with a nylon piston, and compressing the piston with an Intron testing machine. Hydrostatic load of up to 5 MPa was achieved during quasi-static compression of the piston. The load applied by the Instron machine was coupled with the Digital Image Correlation data to analyze the constitutive behavior of the PVC foams. The hydraulic crush pressure, bulk modulus, and energy stored up to densification strain were determined for each foam density.