In this paper, we report a method to control acoustic field in a main pipe of a thermoacoustic engine by onnecting a branch duct. This method is based on the fact that the complex acoustic admittance in the main pipe discontinuously changes at the position where the branch duct is connected. It is demonstrated that the connection of the branch duct with a proper length at a right position turns the existing acoustic field in the main pipe to a pure traveling wave field without introducing the acoustic power loss flowing down the branch duct. This method would be applicable to various thermoacoustic devices such as a looped-tube traveling wave engine.

View full abstract

In this research, our interests focused on the thermoacoustic prime mover to recover the waste heat and effective utilization of it. The advantages of this prime mover are the flexibility for various heat sources as an external engine and a possibility as the cost effective system due to simple structure. To improve the total thermal efficiency, various efforts have been made experimentally to grasp the optimization of stack structure which plays an important role to energy conversion. Finally, discussion on the future application of prime mover aiming to utilize the waste energy of exhaust gas is made.

View full abstract

To achieve a high efficiency of the thermoacoustic engine with a looped tube, we have to suppress an acoustic streaming such as Gedeon streaming. A lubber membrane and 'Jet Pump' can work as an acoustic-streaming suppressor. In this study, we use a lubber membrane as an acoustic-streaming suppressor, and determine the affect of position of the membrane to the onset temperature ratio and the acoustic field formed in the looped tube thermoacoustic engine. As a result, the optimum position of the acoustic-streaming suppressor to decrease the onset temperature and to generate traveling wave mode was determined.

View full abstract

Test models of free piston Stirling engine (FPSE) converter have been developed as heat-to-electricity power converters for a demonstration of solar heat energy utilization at the Japan Aerospace Exploration Agency (JAXA), for future aerospace applications. In the case of the FPSE, the output power of the working gas is directly used as the linear alternator input and then converted into electrical power. Therefore, the linear alternator is one of the most important devices in the FPSE. On the other hand, thermo-acoustic engine (TAE) is a technology that uses high-amplitude sound waves induced by a temperature difference. The work of the sound waves can be converted to electricity by a highly efficient linear alternator. Therefore, the linear alternator is also a key component for the TEA. To realize efficient linear alternators that are suitable for the TAE, several types of linear alternators have been designed and developed based on JAXA's FPSE technology. In this study, the performance evaluations of the linear alternators were conducted.

View full abstract

Numerical simulation of heat and fluid flow has been performed to investigate the difference in temperature change by the difference in thermal condition of the regenerator of a thermoacoustic oscillator. Transient one-dimensional equations of continuity, momentum and energy were solved utilizing the TVD scheme. A simple physical model was used for the numerical simulation. In this study, the effect of thermal condition of the regenerator on gas temperature was made clear.

View full abstract

One-piston type engines with the pulse tube and the stack, etc. are attractive energy-conversion devices that achieve simplicity. The operation mechanism has not been clarified enough yet though experimental studies have been conducted so far. We tried the analysis of the performance characteristics by employing a numerical simulation based on a nodal analysis, and searched for the directionality of a further performance improvement.

View full abstract