Hydraulic Absorber Research Articles

Design and dynamic analysis of landing gear system in vertical takeoff and vertical landing reusable launch vehicle

Landing gear system is a key part of the implementation of reusable vertical takeoff and vertical landing launch vehicle, where its buffing performance is directly related to the vehicle whether it can land safely or stably. According to the reusable launch vehicle general scheme, outrigger landing legs are designed, and the hydraulic absorber is used for the landing gear system. Meanwhile, a scaling principle prototype of landing gear system is developed, and the landing impact test is carried out. A dynamic simulation model of the landing vehicle has been set up, researching the influence of parameters, such as the horizontal velocity, initial inclination, surface friction coefficient, and pitch angular velocity on the landing performance. Four kinds of extreme conditions are identified, and dynamic response characteristics of landing system under each extreme condition are conducted. The simulation results are in good agreement with the experimental data. The buffing performance of the vehicle meets the design requirements, which provides a reference for the design of landing gear system of the vehicle.

Advancing Tube Receiver Performance by Using Corrugated Tubes

Abstract Direct introduction of solar energy into a Brayton cycle using Solar Tower systems enables a highly efficient conversion of the solar energy, especially so when combined cycles are used. One key component of such a solar gas turbine system is the receiver. High and inhomogeneous heat fluxes pose the main challenge for the design of such receivers. One possible design of the receiver uses directly irradiated metallic tubes arranged in an insulated cavity. The paper presents the results of a study comparing thermo hydraulic absorber tube layouts with varying absorber tube dimensions and number of parallel tubes. The more parallel tubes are used the lower is the velocity of the fluid flow and in the same way the heat transfer coefficient is reduced. This leads to higher wall temperatures and therefore to a lower receiver efficiency. Using corrugated tubes instead of smooth tubes gives the possibility to increase the heat transfer coefficient.A thermo hydraulic test bench was developed in order to analyze the influence of different structures of corrugated tubes on heat transfer capability and pressure drop. The geometry of helicallyribbed tubes was optimized using CFD modelling. Design goal was a high heat transfer coefficient without exceeding the allowed pressure drop of the turbine. The resultingconfigurations were used to improve a tubular receiver based on the SOLUGAS receiver design. A thermal FEM model was used to analyze the temperature field and the efficiency of the different receiver designs. Solar radiation, convection to fluid, radiation exchange, convective and conductive losses were considered in the model. It was found that the receiver efficiency of about 0.719 (at design point) could be increased up to 0.835 by using more parallel absorber tubes than needed to fulfill the pressure drop limit.

Development of hydraulically driven shaking table for damping experiments on shock absorbers

The hydraulically driven shaking table has been developed for damping characteristic experiments on shock absorbers in this paper. The damping characteristics and corresponding experiments on the double-tube hydraulic absorber are analyzed firstly, and its damping force model is also built. Then the working principle is introduced, and the structure and components of the physical shaking table are described, especially the hydraulic actuator, composed of servo valve controlled asymmetric cylinder with damping load, is analyzed. Considering parameter uncertainty, nonlinearity, asymmetry and time-variation of such hydraulic system, as well as repeatability of desired trajectory, an open-closed-loop ILC scheme is designed to solve the challenging control issue. The simulation and experiments are developed to verify the feasibility of working principle and the superiority of proposed control method. The hydraulically driven shaking table developed by discussed electro-hydraulic control technology has been applied in actual damping characteristic experiments for a serial of shock absorbers, and achieved satisfactory testing performance.

Optimization Rules of Hydraulic Absorbers Energy Absorbing

For optimizing hydraulic absorbers energy absorbing, weve studied the effects of the velocity point (Vmax), the valves opening gate (V0), the stage after the valve is open and the hysteretic lag. The equations of the F-V history curve and the F-S curve at the stage before the valve is open (T1) and after the valve is open (T2) were set up. When Vmax was bigger, T1 was shorter and the displacement of the opening gate (S0) was smaller. But S0 was approximate to A. If we advanced V0, S0 would be smaller, but S0 was was still close to A and it might cause an abnormal vibration. The F-S curve was an ellipse curve at T2. The area of this ellipse was close to k2, but the plumpness degree (φ) was a constant. The damping forces hysteretic lag would induce the F-S curves un-plumpness and over-plumpness. The un-plumpness is more severe than the over-plumpness. It is proper to use the opening gate instead of Φ to describe the damping forces hysteretic lag.

Rod Orifice Hydraulic Absorber and Application for Impact Crash Simulation

Crash simulation systems in laboratory are widely used in the development of components or protect against the crash pulse. Based on a rod control hydraulic engery absorber, the paper describes a new crash simulator providing repeatable simulation of the important parameters of the automobile deceleration pulses during crash condition. The mathematic models of absorber and the control rod design method were presented also .According to replaced the different variable diameter control rod of absorber, the simulator is simple and easy to simulate different crash pulses including total velocity and acceleration during the pulse. and the control effect of the simulator was tested and verified by experiments.

Synchronization and sommerfeld effect as typical resonant patterns

We analyze a classical problem of oscillations arising in an elastic base caused by rotor vibrations of an asynchronous driver near the critical angular velocity. The nonlinear coupling between oscillations of the elastic base and rotor takes place naturally due to unbalanced masses. This provides typical frequency–amplitude patterns, even let the elastic properties of the base be linear one. As the measure of energy dissipation increases, the effect of bifurcated oscillations can disappear. The latter circumstance indicates the efficiency of using vibration absorbers to stabilize the dynamics of the electromechanical system. The second section of this paper presents results of theoretical studies inspired by the problem of reducing the noise and vibrations by using hydraulic absorbers as dampers to dissipate the energy of oscillations in railway electric equipments. The results of experimental trials over this problem and some theoretical calculations, discussed in the text, are demonstrated the ability to customize the damping properties of hydraulic absorbers to save an electric power and to protect the equipment itself due to utilizing the synchronous modes of rotation of the rotors.

Adaptive vibration active control of fluid pressure pulsations

Conventionally, passive hydraulic absorbers are utilized in order to reduce the vibrations of the fluid power supply systems. It is very difficult to adapt the variable operation conditions, such as inconsistent vibration frequency and varying loads. This paper presents a new vibration active control method to diminish the vibrations of the fluid power supply efficiently. This method is adaptive and robust in controlling the fluctuating frequencies and load disturbances and is capable of keeping the vibrations at a minimum level under variable pump speeds. This paper illustrates the theory and experimentation of vibration active control of a fluid power supply pipeline system in detail. The multilayer piezoelectric technology (PZT) driven orifice valve is designed with characteristics of a proportional opening area to the control voltage, a high-frequency bandwidth and small size. The adaptive-optimum control method is adopted to adjust the control parameters at any instant against emerging disturbances. Based on the test rig, different vibration control methods were applied; the results indicate and confirm the validity of this principle.

A Hydraulic Absorber for Wideband Vibration Reduction in Ship Hulls

A vibration reduction of ship hulls by an active absorber system is proposed. In the scheme, a tuned mass is moved according to the hull vibration as measured by a multi-mode sensing system in order to generate a suitable active force for vibration reduction of hull girder. In order to supply the large amount of required power, a hydraulic servo system is implemented. Then the dynamic characteristic of the hydraulic system is considered for system design. Based on stochastic theory and optimal theory, the control law of the system is derived in order to approach the optimal level of vibration reduction. A 10-t absorber is applied to a 87,000-t oil tanker to demonstrate the feasibility of this scheme. The results show that the multi-peak values of resonance are suppressed in frequency response. Moreover, the vibration excited by propeller and engine is reduced to an extremely efficient level by this scheme.