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Apart from double acting type engines, Stirling engines have either 2 pistons in 2 cylinders or 2 pistons in a single cylinder. Typically, the heater, regenerator and cooler are installed between the 2 pistons. The pulse tube engine, on the other hand, consists of a single piston in a single cylinder, a pulse tube, a heater, a regenerator, a cooler and a second cooler. For this paper, a simple prototype engine that uses air at normal atmospheric pressure as the working gas was fabricated. The oscillating velocity of the working gas in the pulse tube was measured using LDV, and the work flow emitting out of the pulse tube was observed. In addition, the effect of inserting heat storage material in the pulse tube on shaft power and indicated power was examined experimentally. A dramatic increase in the shaft power was achieved.

The flow loss in the regenerator mainly depends on fluid friction through the regenerator matrix, but it is also generated by sudden expansion and contraction flow at the regenerator ends. The entrance areas at the regenerator ends of typical Stirling cycle machines are smaller than the cross-sectional area of the regenerator matrix. So, the gas flow in the matrix becomes a flow field with non-uniform velocity distribution accompanying the expansion and contraction flow. In this paper, the geometry of a tapered flow passage between the regenerator ends and the matrix to produce more uniform flow in the matrix, is examined experimentally using steady single-blow equipment to model a regenerator with a narrow flow passage at the ends. Additionally, the effects of the flow passages are analyzed using CFD. The effect of the tapered flow passage, in producing more uniform flow, is greater than that of the gap.

The optimization of regenerator performance, that is, the choice of an optimum matrix, is a key factor in the methods to raise the thermal efficiency of Stirling engines. Regenerator matrices often comprise of stacks of similar mesh size gauzes. In a fixed regenerator configuration, the size of the mesh and diameter only influence the matrix characteristics and greatly restrict the choice of the optimum matrix. In this paper, combined mesh matrices, which are composed of two stacked wire gauzes with different mesh sizes, are suggested. An approach to the design of combined mesh matrices is investigated by a simple analysis. In order to certify the matrix performance, the characteristics of three single mesh matrices and four combined mesh matrices are examined using a prototype of the semifree piston Stirling engine generator.

A heat engine called a pulse tube engine has been recently proposed, which consists of only a few parts, namely, differentially heated stacked metal meshes in a cylinder and one piston, coupled to a flywheel. We built the prototype engine and tested its working mechanism from the standpoint of a thermoacoustic framework. We measured the work flux density distribution over the cross section of the pulse tube to elucidate the work source of the engine. This engine belongs to the standing wave engine group and the work source resides not in the stacked metal meshes but in the pulse tube.

In designing Stirling engines stacked wire gauzes are often used as the regenerator matrix, but the choice procedure is not specified yet. In the previous paper, the fundamental characteristics of wire gauzes on the flow friction and heat transfer were studied by steady flow experiments and a theoretical analysis was made on the thermal behavior of the matrix. Based on these results, a method to choose stacked wire gauzes for a regenerator matrix was presented. The aim of this paper if to confirm the validity of the choice procedure. First, the optimum matrix for an experimental engine is chosen. Second, the matrices of various gauze materials and mesh numbers are set up at a constant heat capacity. Finally, engine data are compared with theoretical predictions of each matrix performance.

The engine speed and pressure dependences of performance of the laboratory research Stirling engine MELSE IIIs have been measured for six species of regenerator matrix ; five wire gauses with different mesh numbers and one smonge metal. In addition to the ordinary characteristics such as shaft power, indicated power and thermal input, the flow friction and reheat losses at the regenerator have been determined from the measurements of the instantaneous pressure changes and the heat removed by cooling water, respectively. These two losses related to regenerator matrix properties have been compared with the theoretical ones calculated from fundamental matrix data according to rather simple models. The results indicate that the optimum matrix and geometry of the regenerator can be obtained theoretically.

In Stirling engines, the regenerator matrices are often made up of stacks of similar mesh size gauzes. In a fixed regenerator configuration, mesh size only influence the matrix properties and greatly restrict the choice of optimum matrix. Hence, the combined-mesh matrices which are composed of two stacked wire gauzes with different mesh sizes are suggested. The air of this study is to confirm that this combined mesh extends the possibilities in choosing the optimum matrix and improves the matrix properties. This effect has been confirmed by the using V-type experimental engine.