Multi-Cylinder, Double-Acting Hot Gas Engine

1. Field of the Invention

The present invention relates to a multi-cylinder, double-acting hot gas engine in which each cylinder is surrounded by an annular regenerator-cooler unit and in which a cold gas connection duct connects the end of a cooler remote from the regenerator surrounding a cylinder with a variable volume, low temperature chamber of another cylinder.

2. Description of the Prior Art

A hot gas engine of the type referred to above has been described e.g. in the U.S. Pat. No. 2,590,662. In order to obtain an evenly distributed gas flow through the annular cooler-regenerator unit it is necessary to provide a gas chamber of a substantial volume at the end of the cooler connected to the variable volume chamber of an adjacent cylinder through a duct. Although such gas chamber will have little or no influence on the efficiency of the engine it will descrease the power output and thus increase the engine cost for a desired output.

The object of the present invention is to provide an improved distribution of the flow of gas through the annular regenerator cooler unit of a hot gas engine of the type referred to above while avoiding excessive dead volumes--i.e. volumes not being variable--at the low temperature section of the engine.

The object of the invention is in accordance with the invention obtained thereby that the said cold gas connecting duct consists of a plurality of parallel flow paths leading to different segments of the cooler.

FIG. 1 is a vertical section of a hot gas engine of the type described e.g. in U.S. Pat. No. 2,590,662.

FIG. 2 is a section through the lower end of a hot gas engine according to the present invention and

FIG. 3 is a section along the line III--III of FIG. 2.

Reference will now be made in detail to the preferred embodiment of the invention shown in FIGS. 2 and 3 and to the background technology shown in FIG. 1. In this latter Figure two cylinders of a hot gas engine have been designated by 1 and 2 respectively. Each cylinder 1, 2 contains a piston 3 and 4 respectively dividing the interior of the cylinders into lower and upper variable volume chambers 5, 6, 7 and 8. The lower variable volume chamber 5 of the cylinder 1 is connected to the upper variable volume chamber 8 of the cylinder 2 via a cold gas connecting duct 9 a plenum chamber 10 a cooler 11, a regenerator 12, a plenum chamber 13 and a system of heater tubes 14 (only one of which is shown). In order to obtain an even distribution of the gas flow through the cooler 11 surrounding the cylinder 2 it is necessary to design the plenum chamber 10 so as to have a substantial volume. However, as any volumes containing working gas and not being variable during the operation of the engine will cause a higher weight-power ratio it is desired to keep the volumes of the duct 9 and the plenum chamber 10 at a minimum.

FIGS. 2 and 3 show how the cold gas connecting duct according to the invention has been divided into four parallel ducts 9a, b, c and d leading to four segments 10a, b, c and d of the plenum chamber. The longest ducts 9a, d are leading to plenum chamber segments 10a, d adjacent to cooler segments shadowed by the cylinder 2 as viewed from the variable volume chamber 5 to which they are connected. The shorter ducts 9b and c are leading to smaller segments 10b and c of the plenum chamber. The segments of the plenum chamber are separated by ridges 11.

In a hot gas engine having such size that the volume swept by each piston is 275 ccm the volume of the ducts 9a and d may be 21.6 ccm each and the volume of the ducts 9b and c 8.25 ccm each. The volume of the segments 10a and d under the cooler 11 may be 16.5 ccm each, and the volume of the segments 10b and c 5 ccm each.