| Energy internet is one of the hot topics in modern world energy field. Thermoacoustic electric generation technology has great market potential and wide application value, because it can increase the primary energy efficiency on the application of the cold and hot cogeneration system directly. It can also be applied in solar energy, automobile exhaust,industrial waste heat and other renewable energy power generation areas. Thermoacoustic electric generation technology could be an important part of micro grid and energy internet.Thermoacoustic line electric generation system(TALEGS) is composed by thermoacoustic engine and permanent magnet linear generator(PMLG). Embedded in the thermoacoustic engine acoustic passageway PMLG leads to acoustic impedance mismatch of the two subsystems.The mismatch decreases acoustic power capturing and electric power output, and reduces the acoustic-to-electric efficiency. So it becomes a problem to be solved urgently in the large-scale engineering application for TALEGS. The acoustic impedance match mechanisms on linear generator and thermoacoustic engine were systematically studied in this dissertation for improving acoustic power capturing, electric power output and acoustic-to-electric efficiency, and the optimal designs of linear generator acoustic impedance matching thermoacoustic engine were put forward to improve the performance of the whole system. Major jobs in this paper are listed as follows.Considering the mathematical models of thermoacoustic effect, acoustic pressure, volume flowrate and acoustic power, thermoacoustic engine output characteristics were analyzed.According to acoustics two phase flow theorem, mesoscopic thermodynamic cycle theory in alternating flow engine, acoustic linear theory and thermoacoustic current source theory, an acoustic impedance interconnection model on linear generator and thermoacoustic engine was built by the method of acoustic-power-electric analogy. Acoustic impedance interconnection model systematically presents the acoustic impedance structure of linear generator and coupling characteristics with thermoacoustic engine. The function of the linear generator mechanical spring stiffness coefficient, the load capacitance and the load resistance were systematically analyzed in acoustic impedance interconnection model. Compared with the existing research, the model provides a new thought from the viewpoint of linear generator on the TALEGS optimal design.At the same time it also provides the theory basis to design the acoustic impedance of linear generator for two engines acoustic impedance match.For a raise of acoustic power capturing, electric power output and acoustic-to-electric efficiency in TALEGS, an elastic energy-storage tuning method with dynamic constraint on linear generator was presented. Combining the acoustic impedance interconnection model with elastic energy-storage tuning mechanism with dynamic constraint on linear generator, double threshold designs about the spring mechanical impedance and load capacity reactance of linear generator were put forward. The designs achieve the maximal acoustic power capturing from the acoustic port of thermoacoustic engine.Acoustic impedance match method on the optimal dual power of linear generator was raised. Through the threshold design for the spring mechanical impedance, load capacity reactance and load capacity reactance, the method achieved the maximal electric power output under the constrained conditions of the safe operation of the system and the improvement of capturing acoustic power. The acoustic impedance match methods of linear generator to realize the maximal acoustic-to-electric efficiency were put forward. The elastic energy-storage tuning method with the dynamics constraints of linear generator is easily designed in engineering. The method is good controllability and strong real-time. It can effectively improve the TALEGS match.The mathematical models of acoustic power capturing, electric power output,acoustic-to-electric efficiency, stator current, stator voltage, moving displacement for linear generator on elastic energy-storage tuning were built according to the acoustic impedance interconnection model and acoustic linear theory. The analytic expressions of active and reactive component of gas volume flowrate, real and imaginary part of acoustic impedance of line generator, acoustic impedance angle, active and reactive component of electrical magnetic force of linear generator were also established. The mathematical models provide parameter calculation and design for thermoacoustic electric generation technology on linear generator.The threshold law was achieved for PMLG acting as acoustic impedance, acoustic capacitive and acoustic inductive load in thermoacoustic engine. The threshold law provides theory basis for the optimizing designs that linear generator is embedded thermoacoustic engine in different location.The TALEGS experimental platform was built, which was mainly made of thermoacoustic engine, PMLG, detecting system, control system, and electric load et al. Formsimulating low quality heat source heating by the combustion of butane gas, the heat into thermoacoustic engine was changed by controlling the butane flow. The spring mechanical stiffness coefficient, load resistance and load capacitance threshold were optimized to change the acoustic impedance for linear generator. The acoustic power capturing, electric power output and acoustic-to-electric efficiency of PMLG were measure under the conditions of the optimal design and the non-optimal design.The elastic energy-storage tuning method with dynamic constraint on linear generator, namely the maximal acoustic power capturing double threshold method, double power optimization method and the maximal acoustic-to-electric efficiency method were verified validity by Matlab numerical calculation and experimental platform. Double threshold method achieves the maximal acoustic power capturing,comparing the experimental data of the double threshold method and double resonance method.Double power optimization method achieves the maximal electric power output,comparing the experimental data of the acoustic tuning Stub methods, double resonance method and double power optimization method.The maximal acoustic-to-electric efficiency method was proved effectively,comparing the experimental data of the acoustic tuning Stub methods, double resonance method and the maximal acoustic-to-electric efficiency method.The acoustic impedance characteristics of linear generator and match with the thermoacoustic engine were studied in this article. The paper provides a new research ideas and methods to improve TALEGS performance. |
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