| Thermoacoustic engine is a new type of machinery based on thermoacoustic effect, which exhibits a broad application prospect over traditional engines, such as simple design, environment friendliness, and low-grade thermal energy utilization and so on. It also makes more and more researchers begin to pay close attention to the development of the thermoacoustic engine. In order to further explore the thermoacoustic conversion mechanism and improve the conversion efficiency, this paper supported by Natural Science Foundation of China (NO.51276201) researches on the following several aspects:1. Starting with the research thermoacoustic theory, this paper introduced the development of thermoacoustic theory, and analyzed the shortcomings of existing thermoacoustic theory. Introduced the field synergy theory of convection heat transfer and combined it with acoustic power flow equation in linear thermoacoustic theory. Created the field synergy model of thermoacoustic engine using CFD.2. Research of synergy between temperature field, flow field and the system interior sound field. Based on the field synergy model of thermoacoustic engine established above, sound pressure amplitude and resonance tube volume rate varied with temperature at hot end and stack position were obtained. Fluctuation cycle of system parameters fluctuations and the phase angle between pressure and volume flow rate varied with temperature at hot end and stack position were analyzed. Results show that the period of oscillation was mainly associated with resonant tube length, hardly changing with the change of temperature at hot end and stack position; phase angle increased with the temperature at hot end upward and decreased first and then increased as stack position moved to the right and a symmetric distribution was observed. Studying on the acoustic power the system outputted, a maximum value of acoustic power about137.81w was found when the hot end temperature was850k, which means that temperature field and system interior sound field reach a good synergy. A maximum value of acoustic power about122.49w was found when the stack position was at0.03m, which means that flow field and system interior sound field reach a good synergy. In addition, the flow characteristics and heat transfer characteristics of the system were analyzed; studies show that the resonance tube pressure cycles were an important reason to produce alternating flow in the system, the maximum heat flow between stack and gas at positive direction was bigger than that in negative direction, and this is the macro performance of the thermoacoustic effect.3. Research of synergy between gravity field, magnetic field and the system interior sound field. Based on the field synergy model of thermoacoustic engine established above as well, sound pressure amplitude and resonance tube volume rate varied with installation angle was obtained. The changes of system oscillation period and phase angle under three kinds of installation angle were analyzed. It turns out that when the installation angle was0°, oscillation amplitude, phase angle, sound power all maximized, the system performance was optimal, which means that gravity field and system interior sound field reach a good synergy. The distribution of heat flow waveform under different installation angles was also studied; the results show that heat flow waveform was almost the same when the installation angles were90and-90°and it was much smaller than that of0°By means of adding volume force source term, the synergy between gradient magnetic field and interior sound field and the influence of gradient magnetic field on pressure amplitude and volume flow rate amplitude distribution were studied. The influence of gradient magnetic field on the period of oscillation and the phase Angle between pressure and volume flow rate was analyzed. It shows that the gradient magnetic field can increase the phase angle between pressure and volume flow rate, which can effectively improve the acoustic power output of the system. |
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