Lattice Gas Method Simulation Of Thermoacoustic Oscillation

Thermoacoustic heat engines (including refrigerators) have some advantages,such as simple structure,no or least moving parts,high reliability, potential possibility of operating on low energy level heat source, using environmentally friendly working substance, and etc. In recent these years, because of these inherent advantages, thermoacoustic engines draw researchers'great interests. In the practice applications, thermoacoustic engines usually operate under the nonlinear conditions. Thus, research and development of numerical methods, capable of predicting the performances of nonlinear thermoacoustic devices, is of great significance to the practice applications of thermoacoustic devices. The conventional numerical methods have some difficulties in the simulating on thermoacoustic issues with complicated boundary conditions and nonlinearity. In the present thesis, lattice gas, a modern fluid computation method, was applied to the numerical simulation of thermoacoustic prime movers, and some simulated results and conclusions were achieved, which is hard to obtain in the conventional methods.In simulation, two-dimensional 9-bit lattice gas model was applied to the simulation of thermoacoustic oscillation. A complete multi-particle collision rule was established, and a method for dealing with viscous and thermal boundary was provided in the present model. The onset behaviour of thermoacoustic oscillations with various heat source temperatures was simulated, and the time responses of the temperatures at both ends of stack were also investigated numerically. The studied results demonstrated whether collision rule was perfect or not had important influence on the simulated results from lattice gas model.Temperature field in system had a lagging response to the disturbance of temperature difference across the stack, and the temperature difference influenced directly on the onset behavior of thermoacoustic oscillations. Moreover, heat source with lower temperature was more sensitive to the noise from lattice gas model. Reseau was also researched using two different schemes.In this thesis, the effects of the structural parameters and positions of thermoacoustic stack in the resonator tube were simulated. The quantitative computation method of lattice gas noise was also preliminarily investigated. Two quantitative computation methods for noise estimation, square-difference-like method and area method, were proposed, and main influential factors and measures for reducing lattice gas noise were discussed in this thesis work. This thesis had only done little limit fundamental research work in the aspect of thermoacoustic lattice gas simulation. Of course, there are still many issues in need of further deep investigations. In these aspects such as of quantitative parameters for lattice gas model, thermoacoustic Boltzmann lattice method, and the applications of these lattice methods in thermoacoustic refrigerator simulations, much hard open research work is needed.