Steady State Characteristics of a Flapper-Nozzle Relief Valve

1987 ◽  
Vol 201 (2) ◽  
pp. 135-144 ◽  
Author(s):  
J S Yun ◽  
H S Cho
Keyword(s):  
Steady State ◽  
Pressure Control ◽  
Effective Area ◽  
Body Motion ◽  
Model Parameters ◽  
Dynamics Model ◽  
Relief Valve ◽  
Load Pressure ◽  
Hydraulic Load ◽  
The Relationship

The static and dynamic characteristics of flapper-nozzle type electromagnetic relief valves have not so far been investigated analytically in depth, although they have been widely used for hydraulic load pressure control. In this paper a non-linear model of the relief valve is formulated explicitly, based upon rigid-body motion and fluid dynamics. Model parameters such as discharge coefficients, effective area of the nozzle and the electromagnetic constant were identified from the steady state characteristics and physical dimensions of the valve. Based upon this constructed model the static characteristics such as the pressure override and the relationship between input current and main pressure were obtained analytically and compared with those obtained experimentally. The comparison shows that this constructed analytical model can precisely predict such characteristics.

The Modeling of Electrohydraulic Proportional Valves

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Davide Cristofori ◽  
Andrea Vacca
Keyword(s):  
Steady State ◽  
Linear Model ◽  
Nonlinear Model ◽  
3D Model ◽  
Fluid Dynamic ◽  
Body Motion ◽  
General Nature ◽  
Relief Valve ◽  
Real Component ◽  
Electromagnetic Model

The present work describes the modeling of a proportional relief valve actuated by an electromagnet. Two models were developed and compared each other: a detailed nonlinear model and its linearized version. The modeling approach presented has a general nature and can be applied to various types of electrohydraulic proportional valves (EHPV). The comparison between nonlinear and linear model results shows the limits of the linear approximation to study the real component. Substantially, the nonlinear model is composed by three submodels: the fluid-dynamic model (for the evaluation of the main flow features), the mechanical model (which solves the mobile body motion), and the electromagnetic model (which evaluates the magnetic forces and the electric transient). All submodels are based on a lumped parameter (LP) approach and they implement a specific set of nonlinear equations. However, to carefully model the main electromagnetic phenomena that characterize the proportional electromagnet behavior (including: magnetic losses, fringing effects, and magnetic saturation), a finite element analysis (FEA) 3D model was developed by the authors. The LP electromagnetic model is based on a particular use of the FEA 3D model steady state results. A series of transient simulations were performed through the FEA 3D model in order to quantify the effect of the eddy currents and to determine a second order transfer function used in the linear model to describe the electromagnet dynamics. The remaining parts of the linear model are obtained by linearizing the nonlinear model equations. The FEA 3D model was experimentally validated in steady-state conditions, while the results of the overall model of the valve were verified in both steady-state and dynamic conditions.

Computational fluid dynamics and experimental analysis of the influence of the energy recovery unit on the proportional relief valve

2017 ◽  
Vol 232 (4) ◽  
pp. 697-705 ◽  
Author(s):  
Tianliang Lin ◽  
Qiang Chen ◽  
Haoling Ren ◽  
Ruoxi Lv ◽  
Chen Miao ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Steady State ◽  
Energy Loss ◽  
Hydraulic System ◽  
Energy Recovery ◽  
Pressure Control ◽  
Steady State Flow ◽  
Relief Valve ◽  
Recovery Unit ◽  
Line Pressure

The overflow energy loss in relief valve, which is one of the main reasons leading to the low efficiency of the hydraulic system, had been considered to be impossible to solve. The principle of the overflow energy loss of the relief valve is analyzed and a novel method to reduce the overflow loss using an energy recovery unit, which can improve the return line pressure of the pilot proportional relief valve, is proposed. The influence of the energy recovery unit on the pressure control characteristics and steady-state flow force of the pilot proportional relief valve are discussed. The effects of the return line pressure on the distribution of the flow field and the pressure control characteristics are analyzed through computational fluid dynamics simulation and experiment. The results show that with the increase of the return line pressure, the displacement of the main valve spool increases and the reset spring force increases accordingly. While the steady-state flow force decreases dramatically with the increase of the return line pressure, which results in a smaller pressure differential the pressure differential can be reduced from 15% to 2.5%. It is also observed that the flow rate of the pilot proportional relief valve can be maintained at a certain value with a small oscillation and that the pilot proportional relief valve can release the redundant flow of hydraulic system. This verifies that the pilot proportional relief valve with the outlet connecting to the energy recovery unit to recovery the overflow energy loss cannot reduce the pressure control characteristics, but can achieve a better pressure control accuracy of the pilot proportional relief valve.

CFD Assisted Steady-State Modelling of Restrictive Counterbalance Valves

2020 ◽  
Author(s):  
Jannik H. Jakobsen ◽  
Michael R. Hansen
Keyword(s):  
Steady State ◽  
Friction Model ◽  
System Stability ◽  
Model Parameters ◽  
Cfd Modelling ◽  
Data Set ◽  
Load Pressure ◽  
Basic Model ◽  
And Performance ◽  
Approach To Steady State

The counterbalance valve is an important component in many hydraulic applications and its behaviour hugely impacts system stability and performance. Despite that, CBVs are rarely modelled accurately due to the effort required to obtain basic model parameters and the complexity involved in identifying expressions for flow forces and friction. This paper presents a CFD assisted approach to steady-state modelling of CBVs. It is applied to a 3-port restrictive commercially available counterbalance valve. The model obtained is based on detailed measurements of the valve geometry, a single data set and CFD modelling and includes flow forces and friction. The CFD assisted model is compared to experimental data at three temperatures and two versions of more classical steady-state model based on the orifice equation, uniform pressure distribution and experimental results. The results support the CFD assisted approach as a way to increase modelling accuracy. The load pressure corrected coulomb friction model used manages to capture the changes to hysteresis with temperature but not the changes with pilot pressure.

scholarly journals Steady-state modelling and performance of a rotary direct drive digital valve

2020 ◽  
Vol 53 (3-4) ◽  
pp. 311-319
Author(s):  
Yuesong Li
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Angular Displacement ◽  
Stepper Motor ◽  
Direct Drive ◽  
Rotary Valve ◽  
Steady State Flow ◽  
Load Pressure ◽  
State Flow ◽  
The Relationship

A rotary direct drive digital valve driven by a stepper motor was proposed. By analysing its working principle, the steady-state mathematical model reflecting the relationship between the pressure, the flow and the angular displacement was deduced. Based on this mathematical model, the models of the null valve coefficients, the zero leakage flow and the steady-state flow torque were given. The simulation shows that the relationship between the pressure and the flow of the rotary valve is nonlinear; however, under a constant load pressure, the flow characteristics and the steady-state flow torque characteristics of the rotary valve with rectangular throttle orifices are linear. The experimental results show that the flow is directly proportional to the steps of the stepper motor, and the proposed mathematical models are valid.

scholarly journals Study on dynamic characteristics of underwater pressure compensator considering nonlinearity

2020 ◽  
Vol 11 (1) ◽  
pp. 183-192
Author(s):  
Songyu Li ◽  
Xinguang Du ◽  
Luyao Zhang ◽  
Ken Chen ◽  
Shuai Wang
Keyword(s):  
Steady State ◽  
Hydraulic System ◽  
Total Mass ◽  
Effective Area ◽  
Compensation System ◽  
Spring Stiffness ◽  
Pressure Compensation ◽  
The Relationship ◽  
State Pressure ◽  
Type Pressure

Abstract. The external pressure is the biggest problem faced by underwater hydraulic systems. The strength and sealing ability of the structure are facing enormous challenges. For this problem, the common solution is to use pressure compensation technology. The pressure of the seawater is transmitted to the inside of the hydraulic system through a pressure compensator, which equalizes the return pressure of the hydraulic system and the seawater pressure. The structure of the compensation system, the volume and dynamic characteristics of the compensator, and the compensation failure caused by hydraulic oil leakage will all affect the normal operation of the underwater equipment. Therefore, it is necessary to study the pressure compensation system. This paper analyzes the pressure characteristics of the rubber-bellows type compensator. The dynamic characteristic equation of the pressure is established. Due to the strong nonlinear nature of rubber, the finite element method is used to simulate the deformation process of the rubber-bellows type pressure compensator. The relationship between the volume variation and the spring displacement of the rubber-bellows type pressure compensator is calculated by FE simulation. The relationship is brought into the theoretical equation result to obtain the pressure characteristics of the compensator. Through the control variable method, the influence of damping, total mass, effective area and spring stiffness on the internal pressure of the compensator is obtained. According to the analysis result, the damping ratio should be appropriately increased to reduce the overshoot of pressure fluctuations in the design. Since the damping is difficult to control, the total mass of the end cap, the guide post, the rubber bellows and the spring can be minimized. It also reduces the quality of the equipment. The spring stiffness and effective area have a significant influence on the steady-state pressure. A softer spring should be used and the effective area should be increased as much as possible to reduce the final steady-state pressure.

Pilot Slasher Yarn Drying Model Identification

1988 ◽  
Vol 58 (1) ◽  
pp. 27-34 ◽  
Author(s):  
Allen M. Haas ◽  
Morton W. Reed ◽  
Dennis C. Williams
Keyword(s):  
Steady State ◽  
Model Identification ◽  
Model Parameters ◽  
Operating Characteristics ◽  
First Order ◽  
Percent Moisture ◽  
Basic Operating ◽  
On Line ◽  
Drying Model ◽  
The Relationship

The steady state and dynamic response of a pilot slasher were investigated. Continuous on-line recording of moisture was used to determine the response of the exit moisture to step changes in yarn speed. A method to determine the drying rate from steady state data was developed, and a model describing the relationship between yarn speed and percent moisture regain was proposed and evaluated. The model consists of two first order systems acting in parallel, where the model parameters are functions of yarn speed. This work points out basic operating characteristics of pilot and industrial slashers.

Energy Saving in Electro-Hydraulic System Using a MIMO Fuzzy Controller

2012 ◽  
Vol 622-623 ◽  
pp. 75-79 ◽  
Author(s):  
Pornjit Pratumsuwan ◽  
Santi Hutamarn ◽  
Watcharin Po-Ngaen
Keyword(s):  
Power Consumption ◽  
Energy Saving ◽  
Hydraulic System ◽  
Fuzzy Controller ◽  
Asynchronous Motor ◽  
Pressure Control ◽  
Experimental Result ◽  
Relief Valve ◽  
Load Pressure ◽  
Reduce Power Consumption

Energy saving in the electro-hydraulic system (EHS) that currently exists in most inverter used to adjust speed of the asynchronous motor (ASM) which drive a fixed displacement pump. The most controller commonly used control system such as PID and multi-input single-output (MISO) fuzzy controller. In this paper, a multi-input multi-output (MIMO) fuzzy controller is used to improve the energy saving performance of the EHS. The proposed controller is designed to control the pressure of the EHS to suit the actual needs of the load. The two inputs of controller received signals from the error and change in error of the load pressure of the EHS. For the two outputs of the controller, one output is used to control the inverter to adjust speed of an ASM which drive hydraulic pump, and one output that is used for control proportional pressure relief valve. The proposed controller was implemented to pressure control of compression machine. The experimental result showed that using a proposed controller can reduce power consumption was higher than compared with PID and MISO fuzzy controllers. Particularly, a MIMO fuzzy controller can reduce power consumption by up to 70.22% when compared to the conventional system.

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