Driving Theory & Experimental Study On Piezoelectric Stack Pump Used To Transport ER Fluid

Piezoelectric stack pump used to transport electro rheological (ER) fluid is developed in this paper based on request of the item'Principle and Key Technology Study on Piezoelectric/ER Mixing Extra-Precision Stepper Actuator'. Piezoelectric stack which has the characteristics of high power density, large output force, fast response and high resolution ratio is used to realize the transportation of ER fluid. Piston and diaphragm are coherent to change the dimension, which is adopted in this paper to study and develop piezoelectric stack pump used to transport ER fluid though theory analysis, CFD simulation and experimental testing.1. IntroductionThe item'Principle and Key Technology Study on Piezoelectric/ ER Mixing Extra-Precision Stepper Actuator'is put forward to realize high frequency switch control with the characteristics of high frequency and high precision fluid driving of piezoelectric stack pump with no valve, and with the characteristics of rapid change between liquid and solid under the effect of outer electric field, continuous control and low energy consuming of ER fluid, in the same time, terminal executing organization (rigid fluid cylinder) is used to achieve minutely stepper driving, thereby, high precision impulse hydraulic pressure stepper actuator of high frequency, high stepper speed, high resolution ratio, large journey and driving power is formed. Piezoelectric stack pump is studied in this paper.2. Piezoelectric Materials Piezoelectric StackBasic physical property and some important performance parameters of them is discussed, for example, electromechanical coupling factor, piezoelectric constant, mechanical quality factor, etc.In order to understand the working characteristics and usage better, the characteristics of displacement (under constant force and stress), rigidity and frequency response of piezoelectric stack pump are tested and analyzed though establishing rigid displacement testing and controlling system, rigidity testing system and dynamic testing system. Electric model of piezoelectric stack with loading is established though electromechanical similarity principle.3. Trial-Product of Piezoelectric Stack Pump with Single CavityA new makeup of the combination of diaphragm and piston is put forward in this chapter though the analysis of advantages and disadvantages of piezoelectric stack which is combined with diaphragm and piston. Via the libration analysis to piezoelectric stack pump, some factors that influence the amplificatory coefficient of piezoelectric stack pump are obtained. And the newly produced piezoelectric stack pump with single cavity is tested, and the factor that influences the working performances of piezoelectric stack pump are analyzed in this chapter, which contains cavitation, water hammer, driving waveform and frequency, the rigidity of metal airproof diaphragm, pre-tightening force, the combination way of diaphragm and piston, and some solving methods are brought forward.4. Fluid Field Analysis of ER in the Cavity of PumpER fluid is non-newtonian fluid, and its apparent viscidity is related to shear velocity. The research methods of fluid-solid two phases flow are put forward though analysis on the makeup of ER fluid, and then the flow of ER fluid in the cavity is simulated. To contrast easily, the flow of water and solid oil in the cavity is simulated respectively. It comes out that, the solid particles in the ER fluid increased its apparent viscidity which reduces when flows, and the existence of solid particles increases the flow inertia in some extent.5. Trial-Product and Experimental Research on Piezoelectric Stack Pump with Double Cavities in Parallel ConnectionBased on previous experience, piezoelectric stack pump with double cavities in parallel connection is adopted to gain more flux and output pressure, and the flow field of the flow way is analyzed when the holes in valve are in symmetrical distributing and interleaving distributing. Considering overall, the scheme that holes in valve is in interleaving distributing is adopted in this paper to avoid the influence of disturbed flow when the holes in valve is in symmetrical distributing and increase the flow ability of the ER fluid, and the inner distributing cantilever girder valve is also designed. Cuniform pre-tightening mechanisms is designed to adjust the pre-tightening more exactly and with more reliability. In order to make the cavities structure of the piezoelectric stack pump more reasonable, the flow's flow energy loss in the cavities is discussed, especially the loss of the pipeline with sudden expansion and sudden contraction, in the same time, the cavities structure of piezoelectric stack pump is improved correspondingly. Experimental research is made on piezoelectric stack pump with double cavities in parallel connection, and two cavities in parallel connection are tested mainly when they are work at the same time and respectively to get the performance differences.