Research Publications Authored by SLIIT Staff
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This collection includes all SLIIT staff publications presented at external conferences and published in external journals. The materials are organized by faculty to facilitate easy retrieval.
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Publication Embargo Thermo-electro-mechanical performance of piezoelectric stack actuators for fuel injector applications(Sage Publications, 2009-03-01) Senousy, M.S; Li, F.X; Mumford, D.; Gadala, M.; Rajapakse, R.K.N.DPiezoelectric actuators are increasingly used in fuel injectors due to their quick response, high efficiency, accuracy, and excellent repeatability. Current understanding of their thermo-electro-mechanical performance under dynamic driving conditions appropriate for fuel injection is, however, limited. In this paper, the thermo-electro-mechanical performance of soft Lead Zirconate Titanate (PZT) stack actuators is experimentally investigated over a temperature range of -30°C to 80°C, under driving electric fields of up to 2.0 kV/mm (using an AC drive method and a biased DC offset), different frequencies, and a constant preload of about 5 MPa. Experimental results show that the dynamic stroke of the actuators increases with the magnitude and frequency of the applied electric field, as well as ambient temperature. The dynamic stroke was also found to increase with decreased driving field rise time, which is equivalent to increasing the driving field frequency. At driving frequencies lower than the resonance frequency of the test apparatus (~500 Hz), the strain-electric field behavior under different temperatures agreed well with previously obtained quasi-static results. The duty cycle was found to have a minimal effect on dynamic stroke but significantly affected the amount of heat generated under high electric field magnitudes and/or frequencies. The temperature increase due to self-heat generation under a continuous AC driving field (100% duty cycle) was very high, and limited the maximum driving field magnitude and/or frequency. Reducing the duty cycle significantly decreased the amount of heat generation.Publication Embargo Self-heat generation in piezoelectric stack actuators used in fuel injectors(IOP Publishing, 2009-03-18) Senousy, MS; Mumford, D; Gadala, MS; Rajapakse, R. K. N. DMultilayer piezoelectric actuators are used in fuel injectors due to their quick response, high efficiency, accuracy, low power consumption, and excellent repeatability. Experimental results for soft lead zirconate titanate (PZT) stack actuators have shown that a significant amount of heat is generated when they are driven under high frequency and/or high electric-field magnitudes, both of which occur in fuel injectors. Self-heat generation in these actuators, mainly caused by losses, can significantly affect their reliability and piezoelectric properties, and may also limit their application. Other studies have demonstrated that at large unipolar electric-field magnitudes, displacement–electric-field loss (displacement hysteresis) shows a direct relation with polarization–electric-field loss (dielectric hysteresis). In this paper, a simplified analytical self-heating model is presented. The model directly relates self-heating in multilayer piezoelectric actuators to displacement–electric-field loss (displacement hysteresis). The model developed is based on the first law of thermodynamics, and accounts for different parameters such as geometry, magnitude and frequency of applied electric field, duty cycle percentage, fuel type, and environmental properties. The model shows reasonable agreement with experimental results at low and high electric-field magnitudes.