Thermoacoustic converters are devices for direct conversion of acoustic energy into thermal energy in the form of temperature difference, or vice versa – for converting thermal energy into an acoustic wave. In the first case, the device is called a thermoacoustic heat pump, in the second – thermoacoustic engine. Thermoacoustic devices can use (or produce) a standing or travelling acoustic wave. This paper describes the construction and properties of a single-stage thermoacoustic engine with a travelling wave. This kind of engine works using the Stirling cycle. It uses gas as a working medium and does not contain any moving parts. The main component of the engine is a regenerator equipped with two heat exchangers. Most commonly, a porous material or a set of metal grids is used as a regenerator. An acoustic wave is created as a result of the temperature difference between a cold and a hot heat exchanger. The influence of working gas, and such parameters as static pressure and temperature at heat exchanger on the thermoacoustic properties of the engine, primarily its efficiency, was investigated. The achieved efficiency was up to 1.4% for air as the working medium, which coincides with the values obtained in other laboratories. The efficiency for argon as working gas is equal to 0.9%.

The paper is concerned with an important issue from the field of thermoacoustics - the numerical modelling of the flow field in the thermoacoustic engine. The presented way of modelling is based on the solution to fundamental fluid mechanics equations that govern the flow of compressible, viscous, and heat-transferring gas. The paper presents the way of modelling the thermoacoustic engine, the way of conducting calculations and the results which illustrate the correctness of the selected computational technique.

Thermoacoustic refrigerator uses acoustic power to transport heat from a low-temperature source to a high-temperature source. The increasing interest in thermoacoustic technology is caused due to its simplicity, reliability as well as application of environmentally friendly working fluids. A typical thermoacoustic refrigerator consists of a resonator, a stack of parallel plates, two heat exchangers and a source of acoustic wave. The article presents the influence of the stack position in the resonance tube and the acoustic frequency on the performance of thermoacoustic refrigerator with a standing wave driven by a loudspeaker, which is measured in terms of the temperature difference between the stack edges. The results from experiments, conducted for the stack with the plate spacing 0.3 mm and the length 50 mm, acoustic frequencies varying between 100 and 400 Hz and air as a working fluid are consistent with the theory presented in this paper. The experiments confirmed that the temperature difference for the stack with determined plate spacing depends on the acoustic frequency and the stack position. The maximum values were achieved for resonance frequencies and the stack position between the pressure and velocity node.

Paper presents the results of numerical modelling of a rectangular tube filled with a mixture of air and CO2 by means of the induced standing wave. Assumed frequency inducing the acoustic waves corresponds to the frequency of the thermoacoustic engine. In order to reduce the computational time the engine has been replaced by the mechanical system consisting of a piston. This paper includes the results of model studies of an acoustic tube filled with a mixture of air and CO2 in which a standing wave was induced.

A thermoacoustic heat engine (TAHE) converts heat into acoustic power with no moving parts. It exhibits several advantages over traditional engines, such as simple design, stable functionality, and environment-friendly working gas. In order to further improve the performance of TAHE, stack parameters need to be optimized. Stack’s position, length and plate spacing are the three main parameters that have been investigated in this study. Stack’s position dictates both the efficiency and the maximum produced acoustic power of the heat engine. Positioning the stack closer to the pressure anti-node might ensure high efficiency on the expense of the maximum produced acoustic power. It is noticed that the TAHE efficiency can further be improved by spacing the plates of the stack at a value of 2.4 of the thermal penetration depth, δ_k. Changes in the stack length will not affect the efficiency much as long as the temperature gradient across the stack, as a ratio of the critical temperature gradient Γ; is more than 1. Upon interpreting the effect of these variations, attempts are made towards reaching the engine’s most powerful operating point.

For thin-walled structures invariably exposed to thermal and noise environment, their dynamic response is an extreme concern in the design of the component of advanced hypersonic aircraft. To address the problem, three theoretical models are established with three typical graded thermal distributions considered. By introducing the thermal moment, membrane forces and acoustic loadings into the vibration equation of plate, the governing equation is derived and it is solved combined with boundary conditions of the plate, the modal function and velocity compatibility equations at the fluid-structure coupling surface. The accuracy of the theoretical predictions is checked against finite element results with good agreement achieved. The results show that not the physical parameters with variation of temperature but the thermal moments and membrane forces, cause the buckling phenomenon. It is noted that buckling phenomenon occurs not only in uniform temperature field but also in graded temperature distribution filed. The mechanism analysis about modal snap-through and losing phenomenon indicates that thermoacoustic loadings will affect the stiffness matrix and mass matrix of structure. With the increase of temperature, the lower modes of the plate are lost, the higher modes appear in advance, and the losing phenomenon occurs in accordance with the order.