Showing papers on "Hydraulic machinery published in 2012"

Coherent structures in flow over hydraulic engineering surfaces

Abstract: Wall-bounded turbulence manifests itself in a broad range of applications, not least in hydraulic systems. Here, we briefly review the significant advances over the past few decades in the fundamental study of wall turbulence over smooth and rough surfaces, with an emphasis on coherent structures and their role at high Reynolds numbers. We attempt to relate these findings to parallel efforts in the hydraulic engineering community and discuss the implications of coherent structures in important hydraulic phenomena.

Application of Singular Perturbation Theory to Hydraulic Pump Controlled Systems

Abstract: In this paper, we use singular perturbation theory to simplify control designs for hydraulic systems and to make designs more feasible for engineering practice. The paper presents the derivations, simulations and experimental tests of control laws for a hydraulic displacement-controlled actuator. Analyses of applied conditions and stability proofs are provided. The developed control design procedure is simplified and is robust to variations in the bulk modulus. The proposed design is simulated with cases of different control input models. Experiments are conducted on a novel hydraulic circuit. The results show that position tracking error exponentially decays and control efforts are dominated by low-frequency signals.

Determination of optimal parameters for a hydraulic power take-off unit of a wave energy converter in regular waves

Abstract: Wave energy has the potential to be a major provider of renewable energy, especially in the UK. However, there is the major problem of producing efficient devices for a wide variety of sites with different operating conditions. This article addresses the time domain modelling of a heaving point absorber connected to a hydraulic power take-off (PTO) unit in regular waves. Two cases for the hydraulic PTO unit are considered: an ideal model and a model containing losses. Component losses are included to give a more accurate prediction of the maximum power pro- duction and to discover if the parameters to optimize the device change when losses are included. The findings show that both cases are optimized by varying the size of the hydraulic motor and the optimal size is only dependent on wave period and the trend is the same for both cases. Results also showed that to maximize the power produced for both cases, there is an optimal force that the unit produces, which can be derived from theory. Finally, power reduction as a result of the hydraulic losses is also observed with efficiencies reducing at larger wave heights.

Control of heave-induced pressure fluctuations in managed pressure drilling

Abstract: Managed pressure drilling is an advanced pressure control method which is intended to meet increasingly high demands in drilling operations in the oil and gas industry. In this method, the circulating drilling fluid, which takes cuttings out of the well, is released at the surface through a controlled choke. This choke is used for active control of the fluid pressure in the well. The corresponding automatic control system keeps the pressure at the bottom of the well at a specified set-point despite various disturbances. One of such disturbances, vertical motion of the drill string, causes severe pressure fluctuations which need to be actively attenuated. In this paper we present two different disturbance rejection strategies based on discretized partial differential equations for the well hydraulic system. The performance of the controllers is shown through simulations both under idealized conditions as well as by simulations on a high fidelity drilling simulator.

Permanent Magnet Synchronous Machine Sizing: Effect on the Energy Efficiency of an Electro-Hydraulic Forklift

Abstract: The energy efficiency of an electro-hydraulic forklift is significantly improved by using a permanent-magnet-synchronous-motor-servo-drive-based direct pump control to control the position of the fork without control valves. This paper provides a short evaluation of the hydraulic system and a more detailed analysis of the losses of the electric machine drive system. A theoretical approach is taken and the results are verified by practical measurements. Finally, possible improvements of the energy efficiency in the suggested system are discussed.

An overview of hydraulic systems in wave energy application in China

Abstract: Wave energy is being increasingly regarded in China as a major and promising resource. There are many different ways to convert wave energy to electricity and some other energy. Hydraulic systems are used most widely in some of them to realize this conversion. An overview of hydraulic systems in wave energy application as well as the relevant technologies in China is given in this article. Some basic principles are presented, assessment and advices are shown for each category. Some suggestions of the outlook of hydraulic systems in wave energy application are also given.

A review and design study of blade testing systems for utility-scale wind turbines

Abstract: Since the blades are one of the most critical components of a wind turbine, representative samples must be experimentally tested in order to ensure that the actual performance of the blades is consistent with their specifications. In particular, it must be demonstrated that the blade can withstand both the ultimate loads and the fatigue loads to which the blade is expected to be subjected during its design service life. In general, there are basically two types of blade testing: static testing and fatigue (or dynamic) testing. This paper includes a summary review of different utility-scale wind turbine blade testing methods and the initial design study of a novel concept for tri-axial testing of large wind turbine blades. This new design is based on a blade testing method that excites the blade in flap-wise and edgewise direction simultaneously. The flap motion of the blade is caused by a dual-axis blade resonance excitation system (BREX). Edgewise motion is delivered by the use of two inclined hydraulic actuators and linear guide rail system is used to move the inclined actuators in the flap-wise direction along the blade motion. The hydraulic system and linear guide rail requirements are analyzed and an initial cost estimate of the proposed system is presented. Recommendations for future work on this proposed system are given in the final section of this work.

System-Decomposition-Based Multilevel Control for Hydraulic Press Machine

Abstract: In this paper, a novel system-decomposition-based multilevel control method is proposed to control the complex hydraulic press machine system. The key idea in this proposed method is to decompose the system complexity into a group of simple subsystems, and the control task is shared by a group of simple subcontrollers. First, the complex nonlinear system is decomposed into a group of simple subsystems according to the process knowledge, upon which every subsystem is easily controlled by a simple subcontroller. Then, a sequence control strategy is developed to help these subcontrollers to handle the coupling between subsystems. Finally, the proposed method is applied to control a practical hydraulic press machine and compared with the traditional proportional-integral-derivative control.

Dual hydraulic power steering system

Abstract: A hydraulic power steering system controllable by left and right steering wheels has two control valves, each valve connected to a respective left and right steering wheel, and a valve arrangement that selectively connects one control valve to a source of high-pressure fluid and disconnects the other control valve from the source of high-pressure fluid.

Design, Modeling, and Validation of a High-Speed Rotary Pulse-Width-Modulation On/Off Hydraulic Valve

Abstract: Efficient high-speed on/off valves are an enabling technology for applying digital control techniques such as pulse-width-modulation (PWM) to hydraulic systems. Virtually variable displacement pumps (VVDPs) are one application where variable displacement functionality is attained using a fixed-displacement pump paired with an on/off valve and an accumulator. High-speed valves increase system bandwidth and reduce output pressure ripple by enabling higher switching frequencies. In addition to fast switching, on/off valves should also have small pressure drop and low actuation power to be effective in these applications. In this paper, a new unidirectional rotary valve designed for PWM is proposed. The valve is unique in utilizing the hydraulic fluid flowing through it as a power source for rotation. An unoptimized prototype capable of high flow rate (40 lpm), high speed (2.8 ms transition time at 100 Hz PWM frequency), and low pressure drop (0.62 MPa), while consuming little actuation power (<0.5% full power or 30 W, scavenged from fluid stream), has been constructed and experimentally validated. This paper describes the valve design, analyzes its performance and losses, and develops mathematical models that can be used for design and simulation. The models are validated using experimental data from a proof-of-concept prototype. The valve efficiency is quantified and suggestions for improving the efficiency in future valves are provided. [DOI: 10.1115/1.4006621]

System and method for identifying impending hydraulic pump failure

Abstract: A system and method for predicting impending pump failure in a hydraulic system is disclosed. The system measures and compares the running and moving volumetric deficiencies of the hydraulic system as a whole and if they are not within range of each other by a predetermined threshold, the system determines that at least one of the pumps in the system is about to fail. If such a determination is made by the system, the pump displacement is at standby of each pump is then calculated and the pump with the greatest displacement at standby is determined to be the pump approaching failure. Once the pump approaching failure is identified, a signal is generated to apprise the operator or other entity to enable corrective action to be taken.

Adaptive Estimation-Based Leakage Detection for a Wind Turbine Hydraulic Pitching System

Abstract: Operation and maintenance (OM) cost has contributed a major share in the cost of energy for wind power generation Condition monitoring can help reduce the OM cost of wind turbine Among the wind turbine components, the fault diagnosis of the hydraulic pitching system is investigated in this study The hydraulic pitching system is critical for energy capture, load reduction, and aerodynamic braking The fault detection of internal and external leakages in the hydraulic pitching system is studied in this paper Based on the dynamic model of the hydraulic pitching system, an adaptive parameter estimation algorithm has been developed in order to identify the internal and external leakages under the time-varying load on the pitch axis This scheme can detect and isolate individual faults in spite of their strong coupling in the hydraulic model A scale-down setup has been developed as the hydraulic pitch emulator, with which the proposed method is verified through experiments The pitching-axis load input is obtained from simulation of a 15-MW variable-speed-variable-pitch turbine model under turbulent wind profiles on the FAST (fatigue, aerodynamics, structural, and tower) software developed by the National Renewable Energy Laboratory With the experimental data, the leakage and leakage coefficients can be predicted via the proposed method with good performance

Design, Construction and Testing of a Hydraulic Power Take-Off for Wave Energy Converters

Abstract: This paper presents the construction, mathematical modeling and testing of a scaled universal hydraulic Power Take-Off (PTO) device for Wave Energy Converters (WECs). A specific prototype and test bench were designed and built to carry out the tests. The results obtained from these tests were used to adjust an in-house mathematical model. The PTO was initially designed to be coupled to a scaled wave energy capture device with a low speed and high torque oscillating motion and high power fluctuations. Any Energy Capture Device (ECD) that fulfils these requirements can be coupled to this PTO, provided that its scale is adequately defined depending on the rated power of the full scale prototype. The initial calibration included estimation of the pressure drops in the different components, the pressurization time of the oil inside the hydraulic cylinders and the volumetric efficiency of the complete circuit. Since the overall efficiency measured during the tests ranged from 0.69 to 0.8 and the dynamic performance of the PTO was satisfactory, the results are really promising and it is believed that this solution might prove effective in real devices.

Modeling, simulation and control of a wind turbine with a hydraulic transmission system

Abstract: A complete mathematical model of a hydraulic transmission concept for use in wind turbines is presented. The hydraulic system transfers the power from the nacelle to ground level. The main focus has been to develop a model that takes into account the most important dynamics affecting the wind turbine and the hydraulic transmission system involved, such that the model can be used to analyze the dynamic feasibility of a hydraulic transmission concept. Further, dynamic analysis of a hydraulic transmission system for wind turbines is investigated. The nonlinear dynamic model is developed in MATLAB Simulink. Analytical calculation of natural periods of a linearized model corresponds well with simulations of the overall system. A valve control system is proposed to reduce pressure and power fluctuations at operation both below and above the rated wind speed for the wind turbine. Further, a blade pitch control system based on an aerodynamic power estimator is proposed for operation above the rated wind speed. System simulations for one case below and one case above the rated wind speed show that the dynamic response of the overall system is stable and that the wind turbine variables are within typical ranges for conventional variable speed wind turbines with mechanical transmission. Copyright © 2012 John Wiley & Sons, Ltd.

Electro-hydraulic system for recovering and reusing potential energy

Abstract: A hydraulic system includes a hydraulic actuator, a pump configured to supply fluid to the hydraulic actuator, and a first accumulator fluidly connected to the hydraulic actuator. The first accumulator is configured to store fluid received from the hydraulic actuator. The hydraulic system also includes a motor drivingly connected to the pump and fluidly connected to the first accumulator. The motor is configured to receive the stored fluid from the first accumulator to drive the pump. The hydraulic system further includes a first discharge valve fluidly connected between the first accumulator and the hydraulic actuator. The first discharge valve is configured to supply the stored fluid from the first accumulator to the hydraulic actuator without the stored fluid from the first accumulator circulating through the pump.

Modal Analysis of the Aircraft Hydraulic-System Pipeline

Abstract: DOI: 10.2514/1.C031660 Inthispaperamodalanalysisofanaircrafthydraulic-pipelinevibrationiscarriedoutconsideringtheinfluenceof the fluid–structure interaction. Aircraft hydraulic pipes are always configured in curved rather than straight lines for the limited aircraft space. Therefore, the influence of curvature and friction of the pipeline should be accounted for in the vibration analysis. A mathematical model is developed to predict the vibration of the selected aircraft hydraulic-pipeline section. Vibration testing of the aircraft hydraulic pipeline is carried out, and comparison between the developed model and test is given, which illustrates that the developed model is correct. The research resultsalsoshowthatthemostimportantfactorfortheresonantfrequencyofthepipelinesectionisitslengthbetween the two supports, which can obviously increase the resonant frequency. The friction influence on the resonant frequency of the pipeline is less than the influence of the curvature. And the friction influence can reduce the stress response range, especially at the pressure peaks.

Soft switching approach to reducing transition losses in an on/off hydraulic valve

Abstract: A method for significantly reducing the losses associated with an on/off controlled hydraulic system is proposed. There has been a growing interest in the use of on/off valves to control hydraulic systems as a means of improving system efficiency. While on/off valves are efficient when they are fully open or fully closed, a significant amount of energy can be lost in throttling as the valve transitions between the two states. A soft switching approach is proposed as a method of eliminating the majority of these transition losses. The operating principle of soft switching is that fluid can temporarily flow through a check valve or into a small chamber while valve orifices are partially closed. The fluid can then flow out of the chamber once the valve has fully transitioned. Thus, fluid flows through the valve only when it is in its most efficient fully open state. A model of the system is derived and simulated, with results indicating that the soft switching approach can reduce transition and compressibility losses by 79%, and total system losses by 66%. Design equations are also derived. The soft switching approach has the potential to improve the efficiency of on/off controlled systems and is particularly important as switching frequencies are increased. The soft switching approach will also facilitate the use of slower on/off valves for effective on/off control; in simulation, a valve with soft switching matched the efficiency an on/off valve that was 5 times faster.

Energy Efficient Cooling Systems for Machine Tools

Abstract: Cooling systems are used in machine tools e.g. for the cooling of the spindle, the drives, the cooling lubricant, the control cabinet and the hydraulic system. Cooling systems are one of the main consumers of energy of machine tools. This paper analyses and compares different decentral cooling systems with regard to their power consumption for an exemplary machining centre. To achieve this, the power consumption of the exemplary machining centre is analysed for different operating conditions. On the one hand a cooling system is analysed that from the perspective of energy efficiency represents state-of-the-art technology. And on the other hand a unit is examined whose energy consumption has been optimized. Besides power, displacement of tool centre point and further values as pressure, flow rate and temperature are monitored for the different machining conditions and cooling systems.

Subsea actuation system

Abstract: A subsea drilling, production or processing actuation system comprising a variable speed electric motor (10) adapted to be supplied with a current, a reversible hydraulic pump (8, 28) driven by the motor, a hydraulic piston assembly (92, 101, 1 1 1, 121, 131 ) connected to the pump and comprising a first chamber (2), a second chamber (3) and a piston (4) separating the first and second chambers and configured to actuate a valve (91 ) in a subsea system, a fluid reservoir (14) connected to the pump and the hydraulic piston assembly, the pump, hydraulic piston assembly and reservoir connected in a substantially closed hydraulic system, and a pressure compensator (13, 65) configured to normalize pressure differences between outside the hydraulic system and inside the hydraulic system.

Excavator energy-saving efficiency based on diesel engine cylinder deactivation technology

Abstract: The hydraulic excavator energy-saving research mainly embodies the following three measures: to improve the performance of diesel engine and hydraulic component, to improve the hydraulic system, and to improve the power matching of diesel-hydraulic system-actuator. Although the above measures have certain energy-saving effect, but because the hydraulic excavator load changes frequently and fluctuates dramatically, so the diesel engine often works in high-speed and light load condition, and the fuel consumption is higher. Therefore, in order to improve the economy of diesel engine in light load, and reduce the fuel consumption of hydraulic excavator, energy management concept is proposed based on diesel engine cylinder deactivation technology. By comparing the universal characteristic under diesel normal and deactivated cylinder condition, the mechanism that fuel consumption can be reduced significantly by adopting cylinder deactivation technology under part of loads condition can be clarified. The simulation models for hydraulic system and diesel engine are established by using AMESim software, and fuel combustion consumption by using cylinder-deactivation-technology is studied through digital simulation approach. In this way, the zone of cylinder deactivation is specified. The testing system for the excavator with this technology is set up based on simulated results, and the results show that the diesel engine can still work at high efficiency with part of loads after adopting this technology; fuel consumption is dropped down to 11% and 13% under economic and heavy-load mode respectively under the condition of driving requirements. The research provides references to the energy-saving study of the hydraulic excavators.

Agricultural implement and method of controlling an agricultural implement

Abstract: An agricultural implement, for working soil across which the agricultural implement travels or is towed, comprises a frame (10), a first depth maintaining unit (12a, 12b), comprising a first hydraulic actuator (13a) for adjusting the height of the first depth maintaining unit relative to the frame, a second depth maintaining unit (14), comprising a second hydraulic actuator (15a) for adjusting the height of the second depth maintaining unit relative to the frame, at least one soil working tool (16), and a hydraulic system (17) comprising the hydraulic actuators (13a, 15a), which is adapted to be connected to means (23) for supplying hydraulic fluid to the hydraulic system. A first side of the first hydraulic actuator (13a) communicates with a first side of the second hydraulic actuator (15a) and measuring means (18, 19) are arranged to provide a measured value corresponding to a first amount of hydraulic fluid occurring on said first sides.

Computational fluid dynamics (CFD)-based centrifugal pump multi-working condition hydraulic power optimization method

Abstract: The invention discloses a computational fluid dynamics (CFD)-based centrifugal pump multi-working condition hydraulic power optimization method. The method comprises the following steps of: 1, establishing an initial specimen bank for centrifugal pump multi-working condition hydraulic power optimization on the basis of external characteristic tests; 2, establishing a CFD-based centrifugal pump multi-working condition hydraulic power optimization model; 3, generating a specimen bank for the centrifugal pump multi-working condition hydraulic power optimization and constructing a response surface approximate model by CFD technology on the basis of single point hydraulic design and uniform design methods; 4, globally optimizing the approximate model by a global optimization algorithm; and 5, performing hydraulic power design on a centrifugal pump by a parametric computer aided design (PCAD) according to optimization results so as to obtain a multi-working condition hydraulic power model of the centrifugal pump. The method can perform the multi-working condition hydraulic power optimization on the centrifugal pump according to the performance requirements under multiple working conditions so as to improve the weighted average efficiency and enlarge the high efficiency area range, and can provide references for unstable flowing under the working conditions of actively controlling low flow and cavitation under the working conditions of inhibiting high flow.