| Water hydraulics technology which is operated by fresh water or seawater, has become more and more appealing to engineering fields across the globe, owing to its great advantages such as environment friendliness, non-flammability, cheapness, cleanliness and high availability of the operating fluids. Water hydraulic servo control technology which is an important and indispensable component, and a very important development branch and direction of water hydraulic technology, has already become an extremely important research problem of front disciplines in the world at present.Water hydraulic servo valves are high-precision components, which are the combination of mechanic, electronic and hydraulic technology. Its performance determines the quality of the whole system.In this paper, a structure of hydraulic servo valves has been developed according to the characteristics of water. The water hydraulic servo bridge model,in which the two tandem fixed dampers are adopted as prepositive dampers, is developed. The flow characteristics of the Hydraulic servo bridge is studied especially. The parameter sensitivity analysis for the hydraulic bridge is undertaken. The relationship among the flapper displacement, the spool speed and the end pressure of the spool is explored. The influence of parameters, including the diameter of the nozzle, the diameters of the two tandem fixed dampers, the spool diameter and its sliding speed, the initial clearance between nozzle and flapper, on the characteristics of the hydraulic bridge is also investigated. The orthogonal design is used to analyze the influence and the interaction of those parameters on the characteristics of the hydraulic bridge. This has laid the theoretical foundation for the design of water hydraulic servo valves.The static characteristics and the transmission characteristics of the Hydraulic servo valve are analyzed theoretically, educing its feedback block diagram. According to the block diagram of the servo valve system, the transfer function of the system is obtained. Through the simulation of the transfer function, the bode diagram of the system is drawn, verifying the stability of the servo valve.The flow characteristics of the typical throttles and hydraulic half bridge which consists of two tandem fixed dampers and a flapper-nozzle, are numerically studied using RNG k ?εturbulent model combined with mass transfer equation, volume fraction equation and two-layer zonal model through commercial CFD software package FLUENT. There are two structures of the tandem fixed dampers; one is two small orifices; the other is a small orifice and annular gap damper. By changing the fixed orifice diameter, ring slot length of the gap and, clearance of the gap, the nozzle displacement parameters, the flow characteristics of the Hydraulic bridge is obtained in different geometric conditions and different boundary conditions. The test-bed is technologically reconstructed, a series of coupled elements, including flapper-nozzle, annular gap damper and fixed orifice, are designed. Under the conditions of various throttle clearances, experimental tests are conducted to obtain the flow characteristics of these typical throttles. The force of liquid on the nozzle-flapper is testedOn the basis of these studies, the design and manufacture of the hydraulic servo valve is completed. And by the use of existing test equipment, the test rig of the static characteristics of the hydraulic servo valve is designed. The hardware interface circuit of the experiment device is developed. The multifunction data acquisition and control software is compiled. The test on the static characteristics of the water hydraulic servo valves is completed, and the correlation of test results is analyzed. The static characteristics including no-load flow characteristics, load flow characteristics, leakage characteristics and the characteristics of internal pressure are studied. The Null bias, Hysteresis, Flow gain, Pressure gain, Nonlinearity and Unsymmetry of the Hydraulic servo valve has researched on the basis of the static characteristics. |
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