Fluid Power Components Research Articles

Cavitation Erosion Resistance of Additively Manufactured Materials

AbstractCavitation‐induced wear, also known as cavitation erosion, can be found in many fluid power components, especially in water hydraulics. Cavitation erosion leads to component damage and might even cause system failure. The resistance of various materials to cavitation erosion when using conventional manufacturing processes has already been investigated in the past. In this work, the effects of additively manufactured materials on the resistance to cavitation erosion are investigated and compared to effects after conventional manufacturing. Also, the influence of the build‐up direction of the additively manufactured specimens on cavitation erosion is determined. As the main indicators of cavitation erosion, mass loss and the surface structure are determined for all specimens.

A Concept of Risk Prioritization in FMEA of Fluid Power Components

FMEA is a widely used tool for decades and is also used as an industrial standard. However, there are two main drawbacks of this analysis that have been specified from the beginning. The first one is risk prioritization, which is expressed by a risk priority number (RPN). The RPN is a product of three factors with equal weight: severity (S), occurrence (O), and detection (D), which may produce equal risk priority for different combinations of S, O, and D. The second is the uncertainties caused by converting linguistic terms into quantitative data. The essential data used in the FMEA strongly depend on subjective experts’ opinions, knowledge, and experience. For decades, various attempts of overcoming these weaknesses have been made, not only by academics but also by industry. The Automotive Industry Action Group (AIAG) and Verband der Automobilindustrie (VDA) have created an FMEA handbook that defines action priority (AP) depending on the combination of severity, occurrence, and detection numbers. This study presents an alternative to risk prioritization in FMEA based on failures of the tasks which analyzed systems perform. The fundamental factors S, O, and D have been redefined in a way to minimize uncertainties. The proposed method has been implemented in the flow control valve and can be easily applied in mechanical engineering applications.

Modelling and Validation of Cavitating Orifice Flow in Hydraulic Systems

Cavitation can occur at the inlet of hydraulic pumps or in hydraulic valves; this phenomenon should be always avoided because it can generate abnormal wear and noise in fluid power components. Numerical modeling of the cavitation is widely used in research, and it allows the regions where it occurs more to be predicted. For this reason, two different approaches to the study of gas and vapor cavitation were presented in this paper. In particular, a model was developed using the computational fluid dynamics (CFD) method with particular attention to the dynamic modeling of both gaseous and vapor cavitation. A further lumped parameter model was made, where the fluid density varies as the pressure decreases due to the release of air and the formation of vapor. Furthermore, the lumped parameter model highlights the need to also know the speed of sound in the vena contracta, since it is essential for the correct calculation of the mass flow during vaporization. A test bench for the study of cavitation with an orifice was set up; cavitation was induced by increasing the speed of the fluid on the restricted section thanks to a pump located downstream of the orifice. The experimental data were compared with those predicted by CFD and lumped parameter models.

Lumped parameter model of vane pumps developed in OpenModelica environment

In this paper, the authors present a 0D fluid dynamic model of a vane pump used to refill tanks with fuel. The model is entirely developed in OpenModelica environment, where the authors have created specific libraries of elements suitable for the physical modelling of fluid power components and systems. Among the different approaches, the zero-dimension (0D) fluid-dynamic modelling of positive displacement machines is suitable to study many aspects as: the instantaneous flow rate, pressure and torque transients, the fluid borne noise related to the flow rate and pressure irregularity, the dynamic behaviour of the variable displacement control. Overall, this approach in modelling allows to link the geometrical features of the machine with its dynamic behaviour and for this reason is particularly useful in guiding the design. The model of the vane pump is described together with the main design features that can be analysed in terms of their influence on the pump behaviour. Besides the specific results obtained regarding the design of the pump, the paper also demonstrates the use of OpenModelica language and environment, and its efficacy, into the applications of fluid power modelling and simulation.

Computationally Efficient Practical Method for Solving the Dynamics of Fluid Power Circuits in the Presence of Singularities

In this article, a practical method is proposed for the efficient solution of fluid power systems with singularities originating (in particular) from the presence in the system of small volumes. The method is based on the use of an enhanced version of the pseudodynamic solver (the advanced pseudodynamic solver), which seeks the steady-state solution of pressure building up in the small volume. This solver can be attributed to the class of explicit solvers. There are two main advantages of the proposed solver. The first is the higher accuracy and numerical stability of the solution compared with the classical pseudo-dynamic solver, owing to the enhanced solver structure and the use of an adaptive convergence criterion. The second is the faster calculation time compared with conventional integration methods such as the fourth-order Runge–Kutta method, owing to the obtained possibility of larger integration time step usage. Thus, the advanced pseudodynamic solver can become a preferred method in the simulation of complex fluid power circuits. Simulation results of the C code implementation confirm that the advanced pseudodynamic solver is better than conventional solvers for the solution of the real-time systems that include fluid power components with small volumes.

Additive manufacturing of products with functional fluid channels: A review

Products with functional fluid channels can transfer mass or energy and have been widely used in various fields, including aerospace, robotic, and biomedical applications. The manufacturing of these products with complex fluid channels is usually difficult for conventional fabrication methods; thus, a portion of the fluid flow function must be sacrificed to realize the feasible and smooth fabrication. Additive manufacturing not only provides a new way to manufacture the products with complex internal channels but also highlights design revolution for existing products with regular internal channels currently limited by conventional fabrication methods. To date, many publications have been reported on the design and manufacture of products with functional fluid channels, but there is a lack of an overview on this topic. In this paper, the current state of additively manufactured products with fluid channels are reviewed. Different functional fluid channels in heat exchangers, fluid power components, bipolar plates of proton exchange membrane fuel cells, and artificial blood vessels are summarized, and the challenges and further direction of additively manufactured products with functional fluid channels are also discussed.

Coil Inductance Model Based Solenoid on⁻off Valve Spool Displacement Sensing via Laser Calibration.

Direct acting solenoid on–off valves are key fluid power components whose efficiency is dependent upon the state of the spool’s axial motion. By sensing the trajectory of the valve spool, more efficient control schemes can be implemented. Therefore, the goal of this study is to derive an analytical model for spool displacement sensing based on coil inductance. First, a mathematical model of the coil inductance as a function of air gap width and lumped magnetic reluctance is derived. Second, to solve the inductance from coil current, an optimization to obtain an initial value based on physical constraints is proposed. Furthermore, an experiment using a laser triangulation sensor is designed to correlate the magnetic reluctance to the air gap. Lastly, using the obtained empirical reluctance model to eliminate unknowns from the proposed air gap-inductance model, the model in atmosphere or hydraulic oil environments was tested. Initial results showed that the proposed model is capable of calculating the spool displacement based on the coil current, and the estimation errors compared to the laser measurement are within ±7% in air environment.

Products that are Worth the Eight

Can designing fluid power components from first principles with additive manufacturing in mind pay dividends?

A Hybrid Lumped Parameters/Finite Element/Boundary Element Model to Predict the Vibroacoustic Characteristics of an Axial Piston Pump

Low noise axial piston pumps become the rapid increasing demand in modern hydraulic fluid power systems. This paper proposes a systematic approach to simulate the vibroacoustic characteristics of an axial piston pump using a hybrid lumped parameters/finite element/boundary element (LP/FE/BE) model, and large amount of experimental work was performed to validate the model. The LP model was developed to calculate the excitation forces and was validated by a comparison of outlet flow ripples. The FE model was developed to calculate the vibration of the pump, in which the modeling of main friction pairs using different spring elements was presented in detail, and the FE model was validated using experimental modal analysis and measured vibrations. The BE model was used to calculate the noise emitted from the pump, and a measurement of sound pressure level at representative field points in a hemianechoic chamber was conducted to validate the BE model. Comparisons between the simulated and measured results show that the developed LP/FE/BE model is effective in capturing the vibroacoustic characteristics of the pump. The presented approach can be extended to other types of fluid power components and contributes to the development of quieter fluid power systems.

Matrix FMEA analysis with cause-effect diagram for selected fluid power component

Czasopismo Techniczne » 2017 » Volume 10 » Matrix FMEA analysis with cause-effect diagram for selected fluid power component A A A

Alternative Approach for Modeling Transients in Smooth Pipe With Low Turbulent Flow

A new simplified approach for modeling and simulating pressure transients resulting from the rapid acceleration or deceleration of turbulent flow in smooth-walled fluid lines is introduced. In contrast to previous approaches for modeling turbulence by modifying the head loss terms in the momentum partial differential equation, this approach is achieved by coupling the frequency domain analytical solution to the laminar flow version of the partial differential equations in series with a lumped resistance that has been sized so that the steady flow resistance for the line is equivalent to an empirical turbulent steady flow resistance. The model provides normalized pressure and flow transients that have good agreement with experimental data and with method-of-characteristics (MOC) solutions associated with previously validated turbulence models. The motivation for this research is based on the need for a practical means to simulate the effects of fluid transients in lines that are internal components within a total engineering system without the need to understand the different unsteady turbulence one- and two-dimensional (1D/2D) friction models and also be proficient with the complexities of nonlinear interaction of friction and interpolation errors encountered using MOC. This modeling approach utilizes a preprogramed inverse frequency algorithm, commonly used for system identification, which generates “equivalent” high-order normalized linear ordinary differential equations that can be coupled with models for other fluid power components and easily solved in the time domain using preprogramed numerical algorithms for ordinary differential equations.

Energy generation from weights of moving vehicles: A case study at Alaeddin Keykubad Campus-Konya/Turkey

In this study, an experimental analysis has been conducted to investigate whether the weights of vehicles moving along the roads could be utilised to generate energy or perform any useful mechanical work. The target is to harness the normally wasted energy from the vehicle weights through a hydraulic system placed underneath road bumps over which vehicles pass. To achieve the intended goal, an experimental set up composed of mainly mechanical and fluid power components was designed, manufactured and operated to simulate movements of the vehicles along the road. Parameters such as vehicle weights and speeds were used to find out how the loading and speed conditions of a vehicle can affect the energy generated by the system.

A novel approach for predicting the operation of external gear pumps under cavitating conditions

This paper addresses the problem of predicting the effects of gas cavitation in fluid power components, accounting for the dynamic features of gas (including free air and vapour) release and adsorption. Several approaches to evaluate fluid properties under cavitating conditions have been proposed in the past, but those suitable to model hydraulic components with the classic lumped parameter approach do not consider the dynamic nature of the gas cavitation process. Cavitation can have a relevant impact on component operation, particularly for positive displacement machines directly connected to the oil reservoir. With the goal of studying the cavitation effects in hydrostatic units, in this paper a novel model to describe fluid properties – which utilizes a simplified formulation of the Full Cavitation Model – was integrated in an existing lumped parameter model for external gear machines previously developed by the authors’ research team. While the basic formulation of the new fluid model was previously validated for a single closed fluid chamber, the present study extends its formulation for the case of complete systems in which multiple chambers with variable volume are connected to each other. A proper experimental set-up was developed to permit the validation of the proposed model for the case of external gear pumps. Comparisons between measured and simulated instantaneous internal tooth space pressures as well as the outlet flow rates are presented. The significance of the proposed model is highlighted by comparing its predictions with those obtained using classic models of fluid properties, which cannot predict with accuracy the effects of cavitation.

Research Regarding the Dynamic Behavior of Linear Hydraulic Servo-Systems

The paper presents the theoretical results of extensive research on the dynamic behavior of linear hydraulic motors, carried out in INOE 2000-IHP, in the framework of the NUCLEU Programmer. The research has been conducted both theoretically and experimentally, but, in this paper, is presented only the theoretical research. Theoretical research has taken place with the modern means of mathematical modeling and computer numerical simulation. The article presents some theoretical interested results obtained in the research, results that are of real scientific interest, but, also, with practical value through their use in the design of fluid power components and equipments.

超音波振動を利用したマルチパーパス微小流体駆動デバイス（第２報, ミキシングおよびポンピング性能の定量的評価）

超音波振動を利用したマルチパーパス微小流体駆動デバイス（第２報, ミキシングおよびポンピング性能の定量的評価）

Modelling the Pressure and Temperature Dependence of Viscosity and Volume for Hydraulic Fluids

Viscosity and compressibility have a major impact upon the efficiency and dynamic response of fluid power systems. The viscosity and compressibility of five hydraulic fluids have been measured for temperatures to 150 oC and pressures to 350 MPa. A new correlation of viscosity with temperature and pressure based on the thermodynamic scaling rule of Roland et al. is offered. This correlation provides a means to model elastohydrodynamic effects in fluid power components and extends the accuracy of fluid power system models to higher pressure. The role of phase change and the resulting thixotropy in mineral based fluids is experimentally investigated.

WTC Special 2009 Issue: —Papers from the mini-Symposium on Tribological Aspects of Fluid Power—

The Japanese Society of Tribologists organized the WTC World Tribology Congress 2009, held in Kyoto on 6-11 September 2009, in which 12 Mini Symposia were also held concurrently. Tribological Aspects of Fluid Power was one of those Symposia.The brief scope of this Symposium, designated as Tribological Aspects of Fluid Power, was: “Tribology is the key technology of fluid power components. Not only bearings and seals but also sliding parts of hydraulic pumps and motors as well as cylinders and valves are extremely important elements of such components. Their performance and characteristics strongly affect the reliability and efficiency of those related components.”During this Symposium session, the basics and application of fluid power were discussed.At the Symposium, lubrication models and numerical analyses for hydraulic pumps, motors, valves, and seals as well as tribological characteristics and development of hydraulic oils were presented among other topics. They were then discussed in two sessions. The papers submitted to Tribology Online have subsequently undergone a normal peer review process by multiple reviewers. In this special issue, six papers—four articles and two short communications—are published following the decisions of the authors themselves to submit their papers for peer review.On behalf of the Symposium members, I, the Main Organizer and the Guest Editor, would like to express my sincere gratitude to the Presenters, the Participants, and the Authors for the success of this Symposium and preparing their manuscripts for this special issue. I also thank the Reviewers and the Publication Coordinators for their great efforts undertaken to complete the peer-review processes and perform the difficult and time-consuming tasks of publication. Finally, I extend my special thanks to Dr. Heinrich W. Theissen of RWTH Aachen University, Co-Organizer of this Symposium, as well as Professor Masabumi Masuko, the Editor-in-Chief of this Journal, for their expert help and thoughtful consideration.Main Organizer and Guest EditorToshiharu Kazama

Analysis of unsteady fluid flow inside fluid power components – a challenge to CFD-simulation

Hydraulic and pneumatic valves and hydrostatic pumps are key-components of fluid power drive and control systems. Due to their inherent transient operating conditions and the moving devices included they are posing challenges for numerical simulation. Unsteady fluid flow, moving and deforming flow domain and strong nonlinearities caused by physical phenomenon like aeration and cavitation in hydraulics and shock waves in pneumatics are some of them. Another aspect of increasing importance in design of fluid power components is the need of reduced pulsation and noise emission...

Prediction of Vibration & Noise of Hydraulic Fluid Power Components and Systems

Prediction of Vibration & Noise of Hydraulic Fluid Power Components and Systems

Compositional Modelling of Fluid Power Systems using Predictive Tradeoff Models

AbstractSystem-level decisions can have a large impact on the success of any design project, including those in the fluid power domain. Regardless of efforts by designers to optimize individual fluid power components, poor decisions at the systems level can lead to poor system performance and unsatisfied design requirements. In this paper, the principles of system-level decision making are applied to the design of fluid power systems. Describe a methodology for modelling fluid power component technology using predictive modelling and data mining techniques in a way that facilitates system-level modelling and decision making is described. This approach is demonstrated on the design of a hydraulic log splitter.