Fluid structure interaction for circulation valve of hydraulic shock absorber

Based on the working principle and the damping characteristic of hydraulic shock absorber, a fluid structure interaction method was presented, which was used to analyze the microcosmic and high-frequency processing mechanism of fluid structure interaction between circulation valve and liquid of hydraulic shock absorber. The fluid mesh distortion was controlled by the CEL language, and the fluid struc^tre interaction mathematical model was established. The finite element model was established by ANSYS CFX software and was analyzed by dynamic mesh technique. The local sensitive computational area was meshed by prismatic grid, which could reduce the negative volume problem during the simulation. The circulation valve and liquid of hydraulic shock absorber were simulated and analyzed under the condition of sinusoidal inlet velocity loads. Flow characteristic and dynamics characteristic were obtained. The pressure distribution and the displacement of circulation value were obtained, and the acceleration curve of circulation valve was simulated and analyzed. The conformity of the final simulation results with the experimental datum indicates that this method is accurate and reliable to analyze the dynamics characteristic between circulation valve and liquid of hydraulic shock absorber, which can provide a theoretical foundation for optimizing hydraulic shock absorber in the future.

Underwater hydraulic shock shovel control system

The control system determines the effectiveness of an underwater hydraulic shock shovel. This paper begins by analyzing the working principles of these shovels and explains the importance of their control systems. A new type of control system’s mathematical model was built and analyzed according to those principles. Since the initial control system’s response time could not fulfill the design requirements, a PID controller was added to the control system. System response time was still slower than required, so a neural network was added to nonlinearly regulate the proportional element, integral element and derivative element coefficients of the PID controller. After these improvements to the control system, system parameters fulfilled the design requirements. The working performance of electrically-controlled parts such as the rapidly moving high speed switch valve is largely determined by the control system. Normal control methods generally can’t satisfy a shovel’s requirements, so advanced and normal control methods were combined to improve the control system, bringing good results.

ANALYSIS OF THE DEFLECTION OF REEDS IN AUTOMOTIVE HYDRAULIC SHOCK ABSORBERS

The deformation of reeds in automotive hydraulic shock absorbers is analyzed with the finite element method. Combination of different thick reeds mounted on different supports is studied. The computational results show that deformation of the overlapped reeds is not always equal to the sum of deflection of single reed under any conditions. Experimental results prove computational results to be correct and computational method effective. The method of analysis and view of point can provide reference to the design and manufacture of hydraulic shock absorbers using reeds.

Modeling and simulation of twin-tube hydraulic shock absorber thermodynamic characteristics and sensitivity analysis of its influencing factors

In order to find out the sensitivity of the thermophysical and structural parameters to the thermodynamic characteristics of twin-tube hydraulic shock absorbers,based on the bench test,a method for calculating the time-varying rate of the external work on the shock absorber oil is proposed.And then,a thermodynamic model of the twin-tube hydraulic shock absorber is established by using the basic thermodynamic principles.By analyzing the influence of each parameter on the thermodynamic characteristics of the shock absorber,it can be seen that,the radius of the working cylinder outer wall has the greatest influence on the temperature rise of the shock absorber,followed by the thermal conductivity of the oil,the height of the oil,the heat transfer length of the cylinder barrel,the radius of the oil storage cylinder outer wall,the emissivity of the oil storage cylinder outer wall,the height of the nitrogen,the thermal conductivity of the nitrogen,the specific heat capacity of the oil,the density of the oil,the thermal conductivity of the cylinder,and the mass of the working oil.The kinematic viscosity of the oil has the least influence on the temperature rise of the shock absorber.The research can provide an effective theoretical guidance and reference for the design of the twin-tube hydraulic shock absorber.

Accounting for Quadratic and Cubic Invariants in Continuum Mechanics–An Overview

The differential equations of continuum mechanics are the basis of an uncountable variety of phenomena and technological processes in fluid-dynamics and related fields.These equations contain derivatives of the first order with respect to time.The derivation of the equations of continuum mechanics uses the limit transitions of the tendency of the volume increment and the time increment to zero.Derivatives are used to derive the wave equation.The differential wave equation is second order in time.Therefore,increments of volume and increments of time in continuum mechanics should be considered as small but finite quantities for problems of wave formation.This is important for calculating the generation of sound waves and water hammer waves.Therefore,the Euler continuity equation with finite time increments is of interest.The finiteness of the time increment makes it possible to take into account the quadratic and cubic invariants of the strain rate tensor.This is a new branch in hydrodynamics.Quadratic and cubic invariants will be used in differential wave equations of the second and third order in time.

On the Modeling of Non-Classical Problems Involving Liquid Jets and Films and Related Heat Transfer Processes

Non-classical subjects relating to the dynamics of jet and film flow and related heat transfer processes are considered.These problems,which are relevant to several technological applications,cannot completely be addressed in the frame of the canonical Navier-Stokes equations.The first example deals with the formation of a film flow as a result of the hydraulic shock of a vertical jet impinging on a horizontal plane.The effective thickness of the film resulting from the hydraulic shock is much less than the value obtained using the conventional approach(relying on the assumption of smooth flow),while the corresponding speed is much higher.The next case is a jet penetrating into a pool of another liquid,which under certain conditions can form a jet head of a fungoid shape.When the jet penetrates the pool,it expands sharply,and this situation is another example of circumstances where classical models are flawed.Moreover,by virtue of the intense radiating heat transfer taking place at the front of the jet,a high-temperature jet can penetrate a pool of evaporating coolant,like a“jet in a bag of steam”.These exotic problems are modeled and explained in the present article along with experimental data used for model validation.Several new hydrodynamic phenomena discovered over recent years are presented together with their practical applications,in particular,the modes of soliton-like and shock-wave decay of jets during vibration and electromagnetic resonant decomposition of the jet into droplets of a given size.These phenomena are relevant to the areas of granulation of metal melts,cooling of molten corium during postulated severe accidents in nuclear power plants and in other industrial and technological devices and processes.

Shock waves and water wing in slit-type energy dissipaters

The slit-type energy dissipater（STED）is widely used in hydraulic projects of high water head,large discharge,and narrow river valley,thanks to its simple structure and high efficiency.However,the water wing caused by the shock waves in the contraction section of the STED may bring about harmful effects.A coefficient is introduced for the application of Ippen？s theory in the STED.The expression of the coefficient is experimentally obtained.Simplified formulas to calculate the shock wave angle and the water wing scope are theoretically derived,with relative errors within 5%.