Showing papers on "Hydraulic machinery published in 2016"
TL;DR: In this paper, the authors summarized the recent progress for the cavitation study in the hydraulic machinery including turbo-pumps, hydro turbines, etc., and identified the 1-D analysis method, which is identified to be very useful for engineering applications regarding the cavitating flows in inducers, turbine draft tubes, etc.
Abstract: This paper mainly summarizes the recent progresses for the cavitation study in the hydraulic machinery including turbo-pumps, hydro turbines, etc.. Especially, the newly developed numerical methods for simulating cavitating turbulent flows and the achievements with regard to the complicated flow features revealed by using advanced optical techniques as well as cavitation simulation are introduced so as to make a better understanding of the cavitating flow mechanism for hydraulic machinery. Since cavitation instabilities are also vital issue and rather harmful for the operation safety of hydro machines, we present the 1-D analysis method, which is identified to be very useful for engineering applications regarding the cavitating flows in inducers, turbine draft tubes, etc. Though both cavitation and hydraulic machinery are extensively discussed in literatures, one should be aware that a few problems still remains and are open for solution, such as the comprehensive understanding of cavitating turbulent flows especially inside hydro turbines, the unneglectable discrepancies between the numerical and experimental data, etc.. To further promote the study of cavitation in hydraulic machinery, some advanced topics such as a Density-Based solver suitable for highly compressible cavitating turbulent flows, a virtual cavitation tunnel, etc. are addressed for the future works.
296 citations
TL;DR: In this paper, the authors consider the incorporation of wave energy converters into the model of all the conversion stages from ocean waves to the electricity network, referred to as wave-to-wire (W2W) models, and identify the necessary components and their dynamics and constraints, including grid constraints.
Abstract: Control of wave energy converters (WECs) has been very often limited to hydrodynamic control to absorb the maximum energy possible from ocean waves. This generally ignores or significantly simplifies the performance of real power take-off (PTO) systems. However, including all the required dynamics and constraints in the control problem may considerably vary the control strategy and the power output. Therefore, this paper considers the incorporation into the model of all the conversion stages from ocean waves to the electricity network, referred to as wave-to-wire (W2W) models, and identifies the necessary components and their dynamics and constraints, including grid constraints. In addition, the paper identifies different control inputs for the different components of the PTO system and how these inputs are articulated to the dynamics of the system. Examples of pneumatic, hydraulic, mechanical or magnetic transmission systems driving a rotary electrical generator, and linear electric generators are provided.
120 citations
TL;DR: In this article, the authors reviewed literature published in the period 1990 to 2015 and available at major technical university libraries or e-journals and examined the advantages, limitations and possible configurations of the EHA.
Abstract: Electro Hydrostatic Actuator (EHA) is an emerging aerospace technology that aims at replacing centralised hydraulic system by a self-contained and localised direct drive actuator system. EHA has become an important part of modern flight control systems due to the increased efficiency, reduced leakages and lower overall weight compared to conventional hydraulic systems. This paper reviews literature (in English language only) published in the period 1990 to 2015 and available at major technical university libraries or e-journals. It examines the advantages, limitations and possible configurations of the EHA. The paper also includes control strategies, reliability and fault tolerant techniques along with the thermal aspects of the EHA system. EHA is a multi-domain system consisting of electrical, mechanical, hydraulic and control system. It is treated as a mechatronic system and review of publications related to multi-disciplinary modelling/simulation approaches have been presented in the paper. The...
73 citations
TL;DR: In this article, the authors present an alternative strategy to control water-hammer up-and down-surges, induced into a steel piping system, based on replacing a short-section of the transient sensitive regions of the existing piping system by another one made of polymeric material.
Abstract: Water-hammer control strategies constitute an essential and critical task for both hydraulic designers and manufacturers to ensure the global economic efficiency and safety operations of hydraulic utilities. The primary objective of this paper is to present an alternative strategy to control water-hammer up- and down-surges, induced into a steel piping system. The proposed technique is based on replacing a short-section of the transient sensitive regions of the existing piping system by another one made of polymeric material. Two types of polymeric materials, used for the short-section and including high- or low-density polyethylene (HDPE) or (LDPE), are addressed in this study. The 1-D pressurized-pipe flow model is used to describe the hydraulic system, along with the Ramos formulation, based on two decay coefficients being used for considering the pipe-wall viscoelastic behavior and unsteady friction effects. Numerical computations were performed using the fixed-grid method of characteristics. The efficiency of the numerical model is first verified against experimental data available from the literature. Thereafter, critical flow scenarios relating to water-hammer up- and down-surges, including a cavitating flow, are revealed and discussed to point out the efficiency of the used protection technique. From the case studied, it is found that such a technique could mitigate critical water-hammer surges and, hence, might greatly enhance the reliability of the industrial hydraulic systems and urban water utilities, while safeguarding operators. Despite the available protection measures, the utilized technique can substantially soften both up- and down-surge waves induced by severe water-hammer events. It is also found that the amortization of pressure rise and pressure drop is slightly more important for the case of a short-section made of LDPE polymeric material than that using an HDPE polymeric material. It is also observed that other factors contributing to the damping rate depended upon the short-section length and diameter. In fact, the examination of the pressure peak magnitude sensitivity, with the short-section length and diameter being the controlling variables, provides optimum values of these parameters for sizing the replaced polymeric short-section.
58 citations
TL;DR: In this article, a new methodology is proposed to help water managers quantify the potential energy recovering of an irrigation water network with adequate conditions of topographies distribution, and a case study has been analyzed in a typical Mediterranean region and the potential available energy has been estimated.
Abstract: Water irrigation systems are required to provide adequate pressure levels in any sort of network. Quite frequently, this requirement is achieved by using pressure reducing valves (PRVs). Nevertheless, the possibility of using hydraulic machines to recover energy instead of PRVs could reduce the energy footprint of the whole system. In this research, a new methodology is proposed to help water managers quantify the potential energy recovering of an irrigation water network with adequate conditions of topographies distribution. EPANET has been used to create a model based on probabilities of irrigation and flow distribution in real networks. Knowledge of the flows and pressures in the network is necessary to perform an analysis of economic viability. Using the proposed methodology, a case study has been analyzed in a typical Mediterranean region and the potential available energy has been estimated. The study quantifies the theoretical energy recoverable if hydraulic machines were installed in the network. Particularly, the maximum energy potentially recovered in the system has been estimated up to 188.23 MWh/year) with a potential saving of non-renewable energy resources (coal and gas) of CO2 137.4 t/year.
56 citations
TL;DR: In this paper, a novel offshore wind turbine comprising fluid power transmission and energy storage system is proposed, in which seawater is sucked through a variable displacement pump in nacelle connected directly with the rotor and utilized to drive a Pelton turbine installed on the floating platform.
53 citations
TL;DR: In this article, 3D simulations are carried out using the SST k-ω turbulence model in pump mode under different guide vane openings, which correspond to wave troughs in the external characteristic curves.
Abstract: The hump characteristic is one of the main problems for the stable operation of pump turbines in pump mode. However, traditional methods cannot reflect directly the energy dissipation in the hump region. In this paper, 3D simulations are carried out using the SST k-ω turbulence model in pump mode under different guide vane openings. The numerical results agree with the experimental data. The entropy production theory is introduced to determine the flow losses in the whole passage, based on the numerical simulation. The variation of entropy production under different guide vane openings is presented. The results show that entropy production appears to be a wave, with peaks under different guide vane openings, which correspond to wave troughs in the external characteristic curves. Entropy production mainly happens in the runner, guide vanes and stay vanes for a pump turbine in pump mode. Finally, entropy production rate distribution in the runner, guide vanes and stay vanes is analyzed for four points under the 18 mm guide vane opening in the hump region. The analysis indicates that the losses of the runner and guide vanes lead to hump characteristics. In addition, the losses mainly occur in the runner inlet near the band and on the suction surface of the blades. In the guide vanes and stay vanes, the losses come from pressure surface of the guide vanes and the wake effects of the vanes. A new insight-entropy production analysis is carried out in this paper in order to find the causes of hump characteristics in a pump turbine, and it could provide some basic theoretical guidance for the loss analysis of hydraulic machinery.
53 citations
TL;DR: In this article, a new theoretical analysis has been developed, which is more applicable to the buoy considering hydraulic system, and the results of the study could be a guidance for the PTO design of the heaving buoy sets.
50 citations
TL;DR: In this paper, a multi-body dynamic simulation with the discrete element method is used to describe the performance of the HPGR and the results show good agreement with the DEM approach with the current simple particle replacement model to predict the working gap at high initial nitrogen pressures.
49 citations
TL;DR: In this article, the wave speed and the bulk viscosity for the draft tube of a reduced scale physical model of a Francis turbine were derived based on experimental identification of the hydraulic natural frequency of the test rig.
Abstract: The operation of Francis turbines at off-design conditions may cause the development of a cavitation vortex rope in the draft tube cone, acting as a pressure excitation source. The interactions between this excitation source and the hydraulic system at the natural frequency may result in resonance phenomena, causing serious hydro-mechanical oscillations. One-dimensional draft tube models for the simulation and prediction of part load resonances require an accurate modelling of the wave speed and the bulk viscosity for the draft tube flow. This paper introduces a new methodology for determining these two hydroacoustic parameters in the draft tube of a reduced scale physical model of a Francis turbine, based on experimental identification of the hydraulic natural frequency of the test rig. Finally, dimensionless numbers are derived to define both the wave speed and bulk viscosity for different operating points of the turbine.
48 citations
TL;DR: In this paper, an adaptive integral robust controller is developed for high accuracy motion tracking control of a double-rod hydraulic actuator, which takes unknown constant parameters including the load and hydraulic parameters, and lumped unmodeled disturbances in inertia load dynamics and pressure dynamics into consideration.
TL;DR: In this paper, the authors present a study of practically implementable active tuning methods for a Wave Energy Converter (WEC) power take-off (PTO) power control system.
TL;DR: In this article, the authors present a hybridization methodology which allows to compare different system layouts, to dimension the energy storage devices, to define the optimal control policies, and finally to determine the more effective hybrid system layout.
TL;DR: In this paper, a mathematical model of the working process of an air-driven hydropneumatic (HP) transformer was developed and a dedicated test bench for the HP transformer was established and studied.
TL;DR: In this paper, a new type Electric Hydraulic Actuator (EHA) adopted variable displacement pump is presented to enhance the dynamic response of EHA, this system combines the advantages of electric with hydraulic systems and it is easy to be integrated with the whole electric system, which is a promising tendency to save energy and enhance control performance.
Abstract: In this paper, a new type Electric Hydraulic ActuatorNew EHA adopted variable displacement pump is presented to enhance the dynamic response of EHA. This system combines the advantages of electric with hydraulic systems and it is easy to be integrated with the whole electric system, which is a promising tendency to save energy and enhance control performance. Firstly, the basic principle and the difference with the traditional EHA are introduced. Moreover, the mathematical model is constructed. Then, the controller by using the fuzzy algorithm is designed. Finally, the simulation and experiment for the New EHA are investigated, both of the results show the effectiveness of the New EHA.
01 Oct 2016
TL;DR: In this paper, a fault diagnosis method combining a two-step empirical mode decomposition (EMD) method based on waveform matching and extrema mirror extension with fuzzy C-means clustering was proposed.
Abstract: Hydraulic piston pumps are commonly used in aircrafts and various other equipment, and efficient fault diagnosis of them is playing an important role in improving the reliability and performance of hydraulic systems. Given that the discharge pressure signal of piston pump is a quasi-periodic signal and contains variety of state information, this article proposes a fault diagnosis method combining a two-step empirical mode decomposition (EMD) method based on waveform matching and extrema mirror extension with fuzzy C-means clustering. Based upon discharge pressure signals of piston pumps, the two-step EMD method which can restrain the end effects of traditional EMD is adopted to decompose the original signal. Characteristic vectors are then constructed by computing the normalized characteristic energy of selected Intrinsic Mode Function (IMF) components on the basis of local Hilbert marginal energy spectrum. Finally, fuzzy C-means clustering algorithm is used to identify the faults of pumps. Experimental r...
TL;DR: In this article, the authors investigated the concept of introducing a hydraulic motor in the nacelle to convert rotor shaft work into hydraulic power that is transmitted to the electric generator at ground/sea level.
TL;DR: In this article, two fault-tolerant control strategies are proposed for a hydraulic turbine in a high-fidelity simulator of a hydropower system using Matlab and Simulink environments.
TL;DR: A differentiator with a continuous time-varying gain, constructed from pressure measurements, achieves chattering attenuation without compromising the performance of estimation, and is constructively tuned using analysis based on a time-Varying Lyapunov function.
Abstract: In mobile hydraulic systems, velocities are typically not measured. However, using their reliable estimates for feedback is known to allow designing better control laws. We are going to present a specialized technique to compute such estimates using measurements of positions and pressures in the chambers of hydraulic cylinders. With a rough estimate for an upper bound of the second derivative, computed online from pressures, the goal is to find the first derivative of the position signal in the presence of noise. We propose a differentiator with a continuous time-varying gain, constructed from pressure measurements, achieving chattering attenuation without compromising the performance of estimation. The gain is constructively tuned using analysis based on a time-varying Lyapunov function. In addition, the obtained ultimate bounds on differentiation errors provide a criterion for the enhancement of the precision of the proposed algorithm with a constructive design of its parameters. The experimental results over a forestry-standard mobile hydraulic crane confirm the advantages of the methodology.
TL;DR: In this article, a mathematical model coupled with a large-scale reciprocating compressor, actuator and hydraulic system is built, and some performances of the system are tested by the experiment, and the results show that the maximum displacement of actuator increases with the oil pressure until it is limited by the lift limiter.
TL;DR: In this article, a rule-based supervisory control strategy was employed to achieve near-optimal system efficiency with a 50% downsized engine over the standard load-sensing (LS) architecture.
Abstract: Recent demands on improved system efficiency and reduced system emissions have driven improvements in hydraulic system architectures as well as system supervisory control strategies employed in mobile multi-actuator machinery. Valve-controlled (VC) architectures have been in use for several decades and have seen moderate improvements in terms of system efficiency. Further, throttle-less concepts such as displacement-controlled (DC) actuation have been recently proposed and successfully demonstrated efficiency improvements in numerous prototypes (wheel-loaders, excavators, and skid-steer loaders) of different sizes. The combination of electric or hydraulic hybrid systems for energy recovery (for a single actuator) with VC actuation for the rest of the actuators has also been recently deployed by original equipment manufacturers (OEMs) on some excavator models. The combination of DC actuation together with a series hydraulic hybrid actuator for the swing drive has been previously proposed and implemented as part of this work, on a mini-excavator. This combination of highly efficient DC actuation with hydraulic hybrid configuration allows drastic engine downsizing and efficiency improvements of more than 50% compared to modern-day VC-actuated systems. With a conservative, suboptimal supervisory control, it was previously demonstrated that over 50% energy savings with a 50% downsized engine over the standard load-sensing (LS) architecture for a 5-t excavator application. The problem of achieving maximum system efficiency through near-optimal supervisory control (or system power management) is a theoretically challenging problem, and has been tackled for the first time in this work for DC hydraulic hybrid machines, through a two-part publication. In Part I, the theoretical aspects of this problem are outlined, supported by simulations of the theoretically optimal supervisory control as well as an implementable, near-optimal rule-based supervisory control strategy that included a detailed system model of the DC hybrid hydraulic excavator. In Part II, the world's first prototype DC hydraulic hybrid excavator is detailed, together with machine implementation of the novel supervisory control strategy proposed in Part I. The main contributions of Part I are summarized below. Dynamic programming (DP) was employed to solve the optimal supervisory problem, and benchmark implementable strategies. Importantly, the patterns in optimal state trajectories and control histories obtained from DP were analyzed and identified for different working cycles, and a common pattern was found for engine speed and DC unit displacements across different working cycles. A rule-based strategy was employed to achieve near-optimal system efficiency, with the design of the strategy guided by optimal patterns. It was found that the strategy replicates optimal system behavior with the same rule for controlling engine speed for different cycles, but different rules for the primary unit (of the series-hybrid swing drive) for different cycles. Thus, in terms of practical implementation of a rule-based approach, the operator is to be provided with a family of controllers from which one can be chosen so as to have near-optimal system behavior under all kinds of cyclical operation.
TL;DR: In this paper, the performance of a breastshot water wheel with two geometric inflow configurations was evaluated, i.e., a sluice gate at different openings and two vertical overflow weirs.
01 Jul 2016
TL;DR: In this paper, an energy management strategy based on dynamic programming is developed to give full system optimization including both the drivetrain and the working functions for a power-split hydraulic hybrid wheel loader.
Abstract: Energy management strategies for a power-split hydraulic hybrid wheel loader are studied in this paper. The differences between the powertrain and the energy management system for on-road vehicles and the powertrain and the energy management system for off-road vehicles are first identified. Unlike on-road vehicles where the engine powers only the drivetrain, the engine in a wheel loader powers both the drivetrain and the working hydraulic system. In a non-hybrid wheel loader, the two subsystems interfere with each other since they share the same engine shaft. By using a power-split powertrain, this not only allows for optimal engine operation and regenerative braking but also greatly reduces the interference between the drivetrain and the working functions. An energy management strategy based on dynamic programming is developed to give full system optimization including both the drivetrain and the working functions. Both a long loading cycle and a short loading cycle are studied in this paper. The dynami...
TL;DR: Results indicate that the proposed HIS system can be able to independently enhance the mode stiffness/damping, in which the additional bounce/pitch and roll/warp mode stiffness are determined by the difference and summation of the top and the corresponding bottom piston surface area, respectively.
Abstract: A new hydraulically interconnected suspension (HIS) system is proposed to enhance the roll dynamics of the tri-axle straight trucks. The impedance of the hydraulic system is derived with impedance transfer matrix method, and integrated to establish the equations of motion of the mechanical and hydraulic coupling system. Based on the obtained equations, the additional mode stiffness/damping of the vehicle body and wheel state forces are explicitly described with the physical parameters of the hydraulic system. The obtained results indicate that the proposed HIS system can be able to independently enhance the mode stiffness/damping, in which the additional bounce/pitch and roll/warp mode stiffness are determined by the difference and summation of the top and the corresponding bottom piston surface area, respectively. The mode damping is caused by the direction and roll damper valves, simultaneously. The later valves alter the mode damping like the accumulators change the mode stiffness. The comparison of dynamic responses between the trucks with the conventional suspension and the HIS system shows that the HIS system can effectively suppress the roll motion of the truck body and favorably reduce the warp mode force for the wheel stations. Finally, the loss coefficients of the damper valves are tuned in terms of dimensionless factors to handle the compromising indices based on the dynamic responses.
TL;DR: A dynamic model for the CHPU has been developed based upon simplified engine operating characteristics and a set of experimentally identified parameters and experimental testing of the prototype confirms the dynamic model and the output capacity of theCHPU.
TL;DR: In this article, a harmony search multi-objective (HSMO) optimization approach is adapted to the pump scheduling problem, and the model interfaces with the popular hydraulic solver, EPANET 2.0, to check the hydraulic constraints and evaluate the performances of the selected schedules.
19 Aug 2016
TL;DR: In this article, a practical method named feedback nonlinear robust control with disturbance compensation is proposed for a hydraulic system with matched and mismatched generalized uncertainties, in which a finite-time disturbance observer and a non linear robust controller are integrated together by backstepping method.
Abstract: In this article, a practical method named feedback nonlinear robust control with disturbance compensation is proposed for a hydraulic system with matched and mismatched generalized uncertainties (e...
Patent•
15 Jun 2016
TL;DR: In this article, a multi-working-condition comprehensive simulation test system for the reciprocating seal of an aviation actuator is presented, in which a test actuator, a reciprocating driving loading system and a hydraulic system are used.
Abstract: The invention discloses a multi-working-condition comprehensive simulation test system for reciprocating seal of an aviation actuator. The multi-working-condition comprehensive simulation test system comprises a test actuator, a reciprocating driving loading system and a hydraulic system, wherein the reciprocating driving loading system is connected with a piston rod of the test actuator; the hydraulic system is connected to an oil inlet/outlet of a cylinder body; the test actuator comprises an end cover, the piston rod and the cylinder body; the reciprocating driving loading system comprises an electric cylinder, a transmission shaft, a transmission vibration isolating device, a force sensor and an LVDT sensor, and the transmission shaft is connected with the force sensor through the transmission vibration isolating device; and the hydraulic system comprises a pump source module, a pressurization module, a pressure maintaining module and a pipeline heater. By using the multi-working-condition comprehensive simulation test system, multi-working-condition comprehensive conditions such as high pressure, wide temperature range, variable speed and airborne vibration of the aviation actuator can be effectively simulated, and the friction force character of multi-type shaft seal of single piston rod and the leakage rate obtained after repeated reciprocation can be accurately measured under various working conditions; and the multi-working-condition comprehensive simulation test system has the characteristics of convenience in use, operation stability, test accuracy, long service life and the like.
TL;DR: In this paper, an auxiliary error signal-based robust control method and an adaptive control strategy are synthesized through backstepping method for high precise motion tracking control of double-rod hydraulic servo systems.
Abstract: In this study, an introduced auxiliary error signal-based robust control method and an adaptive control strategy are synthesised through backstepping method for high precise motion tracking control of double-rod hydraulic servo systems. The controller takes the non-linear behaviour in flow, unmatched disturbances in inertia load dynamics, and matched uncertainties in pressure dynamics into consideration. In addition, the developed controller does not require a priori knowledge on the bounds of the lumped disturbances and the gain of the devised robust control law can be tuned itself. As a result, the obtained control strategy can achieve an exact tracking performance for the whole closed-loop hydraulic system in the presence of matched and unmatched uncertainties simultaneously. Extensive experiments are carried out for the trajectory tracking control of a double-rod hydraulic servo system and the results reveal the high-performance of the presented controller.