Kazuhiro Hamaguchi

Work flux density measurements in a pulse tube engine

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.

Effects of Flow Passage Equipped Matrix Housing Ends on a Uniform Flow in Regenerators

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.

Effects of Entrance and Exit Shapes on a Uniform Flow in Regenerators

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.

Performance Characteristics of an Atmospheric Pulse Tube Refrigerator

The pulse tube refrigerator does not have moving parts in the cold section and has high reliability. So, it has already been used practically as a cryocooler. However, this type of refrigerator is not developed for residential freezer or air conditioner use. Then, an inertance type refrigerator, which used atmospheric pressure air for the working gas has been developed in order to examine the possibility of the refrigerator for the temperatures around 0 C. In this paper, the effect of inertance dimensions and the regenerator matrix on cool-down characteristic is examined experimentally. Additionally, effects of inertance length on COP and heat loss are analytically examined. As a result, the working gas temperature in the cold head has lowered from room temperature of about 55 C. The gas temperature in the cold head is -32 C.

Improvement of Semifree Piston Stirling Engine Regenerator Performance by Combined Mesh Matrices.

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.