Hydraulic Fluid Flow Research Articles

Failure law of hydraulic pipe joints sealing performance under vibration loads

Aviation hydraulic pipe joints are inevitably affected by vibration loads during service. Fatigue relaxation occurs in the pipe joint structure by vibration, and fretting fatigue wear occurs in its sealing interface, leading to a decline in sealing performance. In order to investigate the sealing performance of hydraulic pipe joints affected by vibration load, this paper first analyzes the modal distribution of the sealing system pipeline under different hydraulic pressures and hydraulic fluid flow rates through vibration frequency sweeping experiments. Secondly, the vibration load is applied to the pipe joints for different numbers of cycles, which reveals the microscopic wear behavior of the sealing interfaces under different tightening torques. Finally, by carrying out the leakage measurement experiment under vibration load, the evolution law of the sealing performance of pipe joints under different hydraulic fluid pressures and tightening torques was obtained.

Experimental and Theoretical Study of a Novel Hydraulic Fluid Flow Control Method

Experimental and Theoretical Study of a Novel Hydraulic Fluid Flow Control Method

Выбор гидравлической схемы для оптимальной работы забоечной машины

Blasthole stemming has a major impact on blasting operations. Depending on the stemming material, different types of equipment are used, one of which is described in this article. The article presents the ZM-7-G stemming truck manufactured by AZOTTEKH LLC, which is designed for mechanized stemming with loose material. The stemming truck complements a range of machines for mechanization blasting operations and improves the blasting efficiency, reducing the flyrock zone and enhancing the environmental situation in the quarry areas. An optimal hydraulic circuit is selected based on this model and taking into account the hydraulic fluid flow rate and pressure of the safety valves set to a specific value. Implementation of the hydraulic circuit with separated hydraulic fluid flows ensures efficient maintenance and economical consumption of the hydraulic fluid, correct operation of the crane with the rated capacity, as well as safe operation of all actuating mechanisms. Conclusions are made on operation of the telescopic crane with a clamp bucket, and a description of the selected hydraulic system is provided.

Investigation of the dynamic stability of pressure regulators when taking into account the inertial forces of the hydraulic fluid flow

The dynamic stability of pressure regulators in hydraulic systems of technological machines is considered, in which additional hydrodynamic forces arise in unsteady modes. The magnitude of these hydrodynamic forces is determined mainly by the first derivative of the flow rate through the throttle slot of the regulator in time. Experimental studies of pressure regulators have shown that hydrodynamic forces, depending on the switching scheme and the design dimensions of these devices, can affect their stability in various ways.

Synchronization in multi-motor hydromechanical systems

Introduction. The paper submits the analysis of existing design solutions of flow dividers used to synchronize hydraulic drives of working bodies of technological and mobile machines. The market demands for multithreaded throttle flow dividers without valves with the controlled division ratio, such as multi-axle vehicle chassis, are identified. The objective of the work was to analyze the possibility and rationale for developing a throttle four-way flow divider without valves with sensing elements of the Venturi tube type. The solution should provide the synchronicity of movement (rotation) of more than three working bodies of technological and mobile machines.Materials and Methods. A patent search for the designs of hydraulic flow dividers is carried out, and systems that require the division of the hydraulic fluid flow into more than two executive bodies are considered. An upgrade option, which allows dividing the flow into four branches, is proposed for the design of a three-channel throttle flow divider without valves.Results. The urgency of developing a multithreaded throttle flow divider without valves for application in industrial and mobile machines is validated. Two types of four-flow dividers are considered, their weaknesses are indicated. It is noted that the development of a multithreaded throttle flow divider based on the designs created in 1989 and 1991 will reduce the number of hydraulic pumps and get rid of the series connection of double-flow dividers. In this way, it is possible to reduce pressure losses in the hydraulic system and implement adaptive control of hydraulic motors of multi-motor mobile machines. The possibility to obtain a divider/combiner into four flows by adding an outlet chamber connected to the membrane chamber through a channel entering the Venturi nozzle on the basis of a three-flow throttle divider is shown. The principle of operation of such equipment is described.Discussion and Conclusions. The principles of construction of throttle flow dividers without valves are considered. An upgrade option is proposed to increase the number of division channels from three to four. However, to validate the operability of this design, a numerical analysis of the various modes of operation of the divider is required — calculation of the reduced volumetric stiffness of its working cavities. The information obtained can be used to modernize the hydraulic units of technological and mobile machines, increase their reliability, manufacturability, and efficiency. The issues that need to be solved in further research are identified.

Mining Institute, Far Eastern Branch of the Russian Academy of Sciences

The problem of processing sands from polymineral placer deposits of the Far Eastern region is a complex technical and technological process. The predominance of high-clay placers with high content of valuable components of small and thin fractions is noted. At the same time the content of fine gold fractions smaller than 0.5 mm reach more than 90 % at some sites with the predominance of fractions smaller than 0.3 mm. The necessity to improve the technologies and technical facilities for processing placer high-clay sands with a high content of fine and nanoscale particles of valuable components is substantiated. Therefore, the purpose of the study is to substantiate approaches to the construction of a phenomenological model for processing of placer high-clay sands by gravitational methods to ensure safety of crystals and reduce the loss of valuable components with reduced energy intensity. On the basis of the proposed exponential dependence of variation of specific interfacial surface of mineral particles on system thermodynamic potential, it has been found out that interdependence of hydraulic fluid efflux and flow rates plays a decisive role in microdesintegration of mineral particles under conditions of turbulization initiated by the jet falling on the flat surface of the cavitation reactor. The calculations performed allowed to estimate the growth of the specific interfacial surface of particles in the intervals of 1.8–3.3 times depending on regulation of hydraulic fluid flow rate, its density and initiation time. Presented mathematical dependencies will allow to control the process when testing cavitation reactor, assess installation quality and operation nature, as well as adjust the design and introduce necessary changes. We propose a general processing scheme for placers with the use of a number of innovative installations of a new type including those based on the combination of turbulence and cavitation at low energy intensity. The impact of hydrodynamic effects initiated by turbulent effects and cavitation on hydraulic fluid of high-clay sands is able to ensure reliable microdesintegration-dispersion and provide a significant reduction in technological losses of valuable components. The study results obtained can be used for further development of theoretical approaches to the description of cavitation processes modeled in proposed installations.

Modeling separation of mineral particles in the upward flow

The paper presents a new tested and approved physico-mathematical model which sufficiently accurately and reliably describes the path of mineral particles in the upward flow along the inclined surface. The Mineral Dressing Laboratory at the Institute of Mining of the North has developed the separation method in the upward flow of hydraulic fluid and the high-angle concentrator design. The modeling results can be used to control separation in the working zone of the high-angle concentrator.

Development of a trajectory planning algorithm for a 4-DoF rockbreaker based on hydraulic flow rate limits

In this paper, a novel trajectory planning methodology is proposed for use within a semi-automated hydraulic rockbreaker system. The objective of the proposed method is to minimize the trajectory duration while hydraulic fluid flow rate limits are respected. Within the trajectory planning methodology, a point-to-point path planning approach based on the decoupling of the motion of the rockbreaker’s first joint is compared with an alternative approach based on Cartesian straight-line motion. Each of these path types is parameterized as a function of time based on an imposed trajectory profile that ensures smooth rockbreaker motions. A constrained nonlinear optimization problem is formulated and solved with the trajectory duration as the objective function while constraints are applied to ensure that flow rate limits through the rockbreaker’s proportional valves and hydraulic pump are not exceeded. The proposed methodology is successfully implemented to compute a set of representative trajectories, with the path planning approach based on the decoupling of the motion of the rockbreaker’s first joint consistently producing shorter trajectory durations.

ANALISA PENYEBAB KERUSAKAN PADA IMPELLER POMPA SENTRIFUGAL DENGAN MENGGUNAKAN METODE FAILURE MODE EFFECTS ANALYSIS (FMEA) DI PT. MESKOM AGRO SARIMAS (IN PRESS)

Centrifugal pump is one type of dynamic pump, centrifugal pump is also one of the hydraulic fluid flow machines basically used to machines basically used to move incopessible fluid flow from one place to another. At PT. MESKOM AGRO SARIMAS, one of the production processes uses a centrifugal pump to supply canal water in the manufacture of mineral water. These centrifugal pumps often experience small or large damage specifically in the impeller. This study uses a failure mode effect analysis (FMEA) method to analyze the causes of damage to the pump used at PT. MESKOM AGRO SARIMAS . The FMEA method is a method used to analyze damage to components that might cause damage to centrifugal pumps. The results of the analysis found that the critical pump components based on the diagram are fishbone which has 5 failures with the highest value of Rpn. Keywords : FMEA, fishbone , impeller , centrifugal pump

Modeling and Control Design for an Inlet Metering Valve-Controlled Pump Used to Control Actuator Velocity Via H-Infinity and Two-Degrees-of-Freedom Methods

Using a unique inlet metering pump with fixed displacement and speed, this work introduces a new way to control a linear hydraulic actuator velocity. The inlet metering system consists of an inlet metering valve that adjusts the hydraulic fluid flow that enters the pump and a fixed displacement pump. Fluid is supplied to the inlet metering valve at a fixed pressure. Energy losses associated with flow metering in the system are reduced because the pressure drop across the inlet metering valve can be small compared to a traditional valve-controlled system. A velocity control system is designed using the inlet metering pump to control the fluid flow into a hydraulic cylinder. First, the valve dynamic model is ignored, the open-loop response is studied, and closed-loop proportional and proportional derivative controllers are designed. Next, the valve dynamic model is included and closed-loop proportional integral derivative, H∞, and two-degrees-of-freedom controllers are designed. Designs with the goals of stability and performance of the system are considered so that a precise velocity control system for the hydraulic cylinder is achieved. In addition to the potentially high efficiency of this system, there is potential for low-cost, fast-response, and less complicated dynamics compared to other systems. The results show that the velocity control system can be designed so that the system is stable for all cases and with 0% overshoot and no oscillation depending on valve dynamics using the two-degrees-of-freedom controller for tracking the desired velocity.

글라스울을 단열재로 활용한 멀티코어튜브의 단열 성능 분석 및 실험에 관한 연구

This study is to investigate the temperature characteristic of insulated multi-core tube to use a glass wool as an insulator on the multi-core tube used for efficient use of limited space and an essential part of high pressure hydraulic control line. Testing and modeling has been conducted to the manufactured insulated multi-core tube to investigate the inside temperature characteristic of the insulated multi-core tube related to the outside air temperature, supplied with hydraulic fluid temperature and hydraulic fluid flow rate. As a result of the study area, when hydraulic fluid flow rate is 3.28(ℓ/min), hydraulic fluid outlet temperature has been received the lowest effect of supplied temperature and outside air temperature of hydraulic fluid.

Model natężenia przepływu płynu hydraulicznego przez nieszczelności par precyzyjnych sterownika elektrohydraulicznego automatycznej skrzyni biegów

Przedstawiono warunki pracy oraz funkcje płynu ATF w automatycznej skrzyni biegów (ASB). Wykazano, że istotny wpływ na prawidłową pracę sterownika elektrohydraulicznego ASB ma jakość płynu ATF. Przeanalizowano zjawisko przepływu płynu ATF przez szczeliny (luzy) hydraulicznych par precyzyjnych „nazywane natężeniem przepływu nieszczelności wewnętrznej” lub „przeciekiem wewnętrznym”. Wykazano, że nadmierne „przecieki wewnętrzne”, spowodowane nadmiernym zużyciem elementów hydraulicznych i niską lepkością oleju, mogą być powodem spadku ciśnienia płynu w układzie hydraulicznym ASB i przyczyną jej nieprawidłowego jej działania. Zaproponowano model natężenia przepływu przez nieszczelności wewnętrzne hydraulicznych par precyzyjnych elementów rozdzielczych. Wykorzystano zależność na natężenie przepływu przez nieszczelności wewnętrzne hydraulicznej pary precyzyjnej ze szczeliną pierścieniową koncentryczną. Sformułowano założenia modelu i warunki badań. Wartości luzów par precyzyjnych sterownika elektrohydraulicznego określono podczas pomiarów na obiekcie rzeczywistym - po przebiegu eksploatacyjnym ASB. Pomierzono odpowiednie średnice tłoczków i suwaków oraz średnic wewnętrznych otworów cylindrycznych suwaków rozdzielczych i tłumików hydraulicznych. Przeprowadzono wariantowe badania modelu określając sumaryczne przecieki sterownika układu hydraulicznego ASB z różnymi wartościami stopnia zużycia par precyzyjnych i temperatury (lepkości i gęstości) płynu dla warunków jazdy na przełożeniu „1” i „2”.

System dynamic modelling and simulation of hydrodynamic machines

A graph-theoretic framework for the dynamic simulation of hydrodynamic (both axial and radial flow) machines is presented in this article. The physics based analytical models are developed by considering the dynamics of the hydraulic fluid flow and its interaction with the mechanical components. A linear graph is used to capture the topology of the system and the interconnection of the constituent components. Using the graph-theoretic framework, a dynamic model of an automotive hydrodynamic torque converter is developed to simulate its behaviour under different flow conditions. The ability of the model to capture different features of the torque converter will also be demonstrated by simulation. The simulation results are compared with and validated by experimental results in the literature.

PREDICTION OF FLOW CHARACTERISTICS THROUGH A CIRCULAR PORT OF A SPOOL VALVE USING CFD APPROACH.

Hydraulic spool valves are used in a variety of ind ustrial equipment’s like earth moving machinery, ai rcrafts and machine tools etc. A hydraulic spool valve is a switching device used for controlling hydraulic devices. A spool val ve can turn the flow of hydraulic fluid from a hydraulic pump to an actuato r in forward or reverse directions or on and off by blocking offthe route of the fluid takes. A controller moves the valve back and forth in its case to slide the spools into different positions. As the spool moves across the inlet port, the port which is initially fully open, circular in shape and permitting the fl uid flow, is getting closed gradually. Once the spool starts moving, the inlet port becomes non circular and continues to be so ti ll closure. The shape and the area of the port that is still left open for the oil to flow is steadily changing. The area which is o riginally circular is becoming far away from circularity. It is required to study the flow in such port-spool combination. The purpose o f the dissertation is to compute the flow for different port openings. ANSYS CFD FLOTRAN software is used to predict the flow c haracteristics. The exact flow path is simulated. The predicted results are compared with the analytical calculations.

Homogeneous Flow of Hydraulic Fluid Retaining Gap

This paper presents the laminar flow of homogeneous liquids in crevices of smooth hydraulic resistance. The paper presents a theoretical model for the distribution of pressure in the gap and the flow rate through the slot hydraulic. The presented theoretical models for the distribution of pressure and flow in the gap on conventional hydraulic resistance of hydraulic joints, whose shape is related to the errors of their execution. In deriving the theoretical models, by introducing a variable height of the gap in the initial episode, was founded stream velocity profile variability in the hydraulic fluid retaining gap and zero values of local losses at the entrance to the slot. An analysis of the validity of the simplifications adopted in the given formulas for the distribution of pressure and flow in the hydraulic gap and on the basis provides guidelines for estimating the energy losses that occur cracks in the hydraulic resistance.

Efficient Control of a Piezoelectric Linear Actuator Embedded Into a Servo-Valve for Aeronautic Applications

Inside a direct-drive servo-valve (DDV), the motion of the spool controlling the direction of the hydraulic fluid flow is directly actuated by an electrical motor. Due to the small stroke needed, it is possible to use a linear amplified piezoelectric actuator directly connected to the spool. The aim of this paper is to investigate how to design the power and control electronics of a DDV based on a linear amplified piezoelectric actuator to take full advantage of such a motor. In particular, it will be shown that the voltage applied on the piezoelectric stacks may be successfully controlled by use of four-quadrant choppers with the benefits that the injected electrical charge stored in their capacity can be recovered. This leads to the low-consumption scheme presented which can be easily fed by a boost converter from the aircraft 28 Vdc.

액셜 피스톤 펌프내 유압유 유동에 대한 수치해석적 연구

Axial piston pumps have been widely used as power sources for hydraulic systems, but studies on the fluid flow within the pump have been usually performed using 1-D analysis because of the difficulties in considering the fluid compressibility, high-speed revolution, variation of the flow rate, and complicated geometry. The goal of this study was to understand the hydraulic fluid flow within axial piston pumps by using the 3-D numerical method and the process of generating discharge pressure ripples. To improve the convergence and robustness of the simulation model, a grid system was constructed with hexahedron-type grids around the valve plate. Furthermore, we employed an empirical formula to describe the relationship between the oil density and pressure. The CFD (computational fluid dynamics) results compared well with the experimental data.

Kinematic Analysis of a Swash-Plate Controlled Variable Displacement Axial-Piston Pump With a Conical Barrel Assembly

Variable displacement, swash-plate controlled, axial-piston pumps are widely used in applications that require high pressure and variable flow rates. The pump consists of a rotating barrel assembly that houses several pistons in a circular array. A swash-plate is used to control the displacement of the pistons to adjust the output flow of hydraulic fluid. As the barrel rotates, the pistons slide along the angled swash-plate and draw oil from the supply and then discharge oil into the high pressure circuit. This results in an almost constant output flow rate. This paper analyzes the kinematics of a pump based on its geometry dependent characteristics. The analysis assumes an idealized case in which there is no oil leakage and the fluid is considered to be incompressible. It is revealed through the analysis that the piston displacement and the pump output flow are slightly increased by using a conical barrel. Instantaneous and mean flow rate equations are used to describe the output flow characteristics and flow ripple effect. The output flow rate ripple profile is found to be a function of both swash-plate angle and the conical barrel angle. A term defined as the flow rate uniformity coefficient is used to better quantify the flow ripple phenomenon. A frequency analysis is performed on the output flow rate and an additional order is found to be present when using a conical barrel pump versus one with a cylindrical barrel when the pumps have an odd number of pistons. Conical barrel piston pumps are found to have a slight increase in piston displacement, velocity, and acceleration relative to the rotating barrel frame of reference over a pump with a cylindrical barrel. This translates into an increase in the output flow rate for a conical piston pump under the same operating conditions. The conical barrel is also found to have a reduction in the rotational inertia allowing for faster angular acceleration. The presence of an extra order from a frequency analysis for a conical pump with an odd number of pistons has the potential to cause unwanted noise or vibration to the structure or components attached to the pump.

Elastohydrodynamic Analysis of an Elastomeric Hydraulic Rod Seal During Fully Transient Operation

A soft elastohydrodynamic model of a reciprocating elastomeric hydraulic rod seal has been developed. It consists of coupled fluid mechanics, contact mechanics, and deformation analyses. The model has been used to analyze a U-cup lip seal in an injection molding application with a time-varying sealed pressure and rod velocity. Results include the histories of the hydraulic fluid flow rate, fluid transport, mean shear stress on rod, sealing zone length, and friction force on rod, as well as distributions of the fluid pressure, film thickness, and contact pressure.

AUTOMATIC CONTROL ALGORITHMS FOR THE ABIOCOR® IMPLANTABLE REPLACEMENT HEART SYSTEM

The AbioCor® Implantable Replacement Heart System (AbioCor) is designed to physically and functionally replace the failing human heart. There are three primary control algorithms that allow the device to automatically respond to changing physiologic demands of the patient: motor speed control, balance control, and beat rate control. The motor speed control algorithm adjusts the speed of the hydraulic pump resulting in the desired hydraulic fluid motion which, when coupled across flexible membranes, translates into optimal blood ejection on every beat to achieve a constant stroke. The motor speed control algorithm is based on the shape of pressure waveform generated in the hydraulic pumping chambers of the thoracic unit (TU). Specifically, for each half beat, the algorithm optimizes the left and right stroke motor speeds in order to achieve an appropriate “end of stroke” spike. This design allows the TU to produce a fixed left stroke volume despite changes in vascular tonc. Both balance control and beat rate control are based on estimates of the atrial pressures derived from the hydraulic pumping chamber pressures during the TU filling phases. For balance control, the desired difference in the left and the right side blood flow (primarily to compensate for bronchial shunt flow) is achieved by maintaining physiologic atrial pressures based on estimates derived from diastolic hydranlic pressures. Extreme atrial pressures must be avoided for the safety of the patient. Because the hydraulic fluid flow out of each side of the AbioCor are closeiy coupled, the blood flows must be correctly balanced by changing the stroke volume of the right side of the device via diversion of hydraulic fluid to a “balance chamber.” For beat rate control, an estimate of right atrial pressure is used to control the beat rate (and therefore flow). As the right atrial pressure rises from about 3 to 18mmHg, the flow increases from about 4 to 8L/min. This keeps the inflow pressures in a safe range and may increase blood flow as activity increases. All algorithms have performed adequately clinically. The beat rate control has not been exercised over a broad range.