Acoustic to electric energy conversion using piezoelectric transducers

Presented is an analysis of a piezoelectric transduction system and a comparison to experimental data. A mathematical model is used to compare the external electric effects of an electric energy conversion system using piezoelectric ceramic transducers. The energy conversion is from electric to mechanical and back to electric.;The transduction system is modeled by an electromechanical circuit in which electrical and mechanical lumped elements represent the electrical and mechanical characteristics of the transducers. The analysis uses combinations of lumped parameter approximations of single transducers. The model is tested using a first set of transducers operating as an acoustic driver connected to a second set of transducers operating as a generator.;Two models are derived that consider the transfer of mechanical energy in different ways. The first model makes the approximation that the mechanical support is insignificant. This model allows mechanical energy transfer through one external surface. The second model considers the mechanical impedance of the mechanical support. This model allows mechanical energy transfer independently through opposite sides of the transducers. The mathematical model agrees well with the measurements. The measurements allow the determination of effective parameter values of material constants for the piezoelectric material.;The input electrical capacitance calculated using the model is compared to experimental measurements. Through these measurements, the parameters most sensitive to the measurements are approximated. Additional measurements of energy conversion are compared with the model adjusted by the parameter values taken from the capacitance comparisons. A value of effective stiffness is a third parameter that is adjusted to match the resonant frequency of the model and the experimental observations. These are the only adjustments to the model. The parameter adjustments required a 2% change in electrical permittivity, 30% change in electromechanical coupling, and 26% change in ideal static stiffness of the value of dynamic stiffness.;A second experiment simulates the second model that includes the impedance effects of the apparatus. The experiment performed to correlate the second model calculations proved to be far too lossy to be of practical value. Further, measurements showed undesirable nonlinear effects that were not modeled. The energy conversion experiment demonstrates a minimum of 85% efficiency, and a power density as high as 889 watts per kilogram of the piezoelectric material.