M

Dundee foundry, hut was subsequently abandoned because of repeated failure of the displacer cylinders, caused by overheating of the poor iron then available.

Single-acting versions of the machine, in various arrangements, are shown in Fig. 6.7. The version having a regenerative displacer may be identified as a Laubereau-Schwartzkopff engine, and. with a separate regenerator, as a Heinrici engine. An arrangement where the cylinder axes were at 90° was made commercially in the last century in fairly large numbers, and was known as the Robinson engine. A machine with interesting possibilities, proposed by II. Rainbow of Bristol. England, in 1971, is shown in Fig. 6.7. This machine has two pistons and a single displacer. This arrangement allows considerable flexibility in the drive mechanism, and facilitates the solution of both sealing and cooling problems.

Single-acting mitItiple-pision arrangements

Single-acting Stirling engines with multiple-piston arrangements can be classified broadly into four groups:

(a) piston-cylinder combinations,

(b) rotary assemblies,

(c) bellows-and-diaphragm types.

(d) free-piston devices.

Piston-cylinder combinations are the best known of all these groups, l ig. 6.8 shows a variety of single-acting two-piston machines, three with stationary cylinders and one rotary-cylinder machine. Of these possibilities only the Rider arrangement of parallel cylinders with the pistons coupled to a crankshaft was produced in any quantity in the last century.

The possible configurations embracing rotary assemblies, or bellows-and-diaphragm systems, is virtually endless. Most represent attempts to overcome difficulties of imbalance or seal problems, arising from reciprocating elements and the associated linkage, but. so far as is known, none ot' these has been brought to a commercial stage. One interesting rotary machine, proposed by Zwiauer.t is shown in Fig. 6.9. Two Wankel-typc rotary engines are coupled on the same shaft, and two (or three) regenerators are arranged symmetrically around the axis. One Wankel unit constitutes the compression unit, and the other constitutes

! Unpublished project proposal. University of Calgary.

Fio. 6.6. Iiarlv twin single-acting Stirling engine with piston and displacer in separate cylinders.

(al Diagrammatic crow-section, showing arrangement of the drive mechanism, (b) Copy of an old engraving of a beam engine dating back to 1827 (after Fmkelstein 1959).

Double-cylinder singlc-acting pision-dispiacer engines

Parallel-cylinder regenerative dispbiccr

(I-auberca^^ Schwartzkopfl")

Twin-expansion cylinder

Twin-expansion cylinder

(Kninbnw)

(Kninbnw)

Parallel-cylinder external regenerator ±=r-i

Parallel-cylinder external regenerator ±=r-i ll leinrici)

ll leinrici)

Cylinders at riglu angles, regenerative displacer

(Rohinsonl

Fig. 6.7. Alternative arrangements of the double-cylinder single-acting pisron-displaocr engine i he expansion unit. Each unit comprises three distinct spaces, and each space experiences Iwo separate expansion or compression processes per revolution. Thus, a combination of the two engines embraces three separate systems, each undergoing two complete cycles per revolution. It is thought thai this arrangement could provide a compact high-specific-ouipui machine, but this has not been reduced lo practice at the present lime.

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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