Charles Louis Franchot

Interconnecting adjacent cylinders constitute one system.

Interconnecting adjacent cylinders constitute one system.

(Siemens)

(Siemens)

I'll?. 6.1. Alternative arrangements of double-acting multiple cylinder engines.

gities. Single-acting engines will doubtless continue to dominate the small-engine field.

Single-acting Stirling engines were invented early in the nineteenth century, and the application in IS I 5 by Robert Stirling for his lirst engine patent may perhaps be reckoned an appropriate date. Other variations and arrangements of single-acting Stirling engines have been conceived at intervals since.

Double-acting Stirling engines were also invented in the nineteenth century. Babcock (1885) ascribes the invention of the two-cylinder, twin-system, double-acting engine to the French engineer, Charles Louis Franchot in 1853. This was subsequently re-invented a century later by Finkelslcin and Polanski (1959) and was later incorporated in a multiple-cylinder, free-piston arrangement by Finkelstein (1963b). The general form of double-acting engines with three or more cylinders is ascribed by Babcock to the celebrated British scientist/engineer Sir William Siemens, better known for his work in steel making. Siemens designed the double-acting Stirling engine shown in Fig. 6.2, having four cylinders each containing a single piston and connected to a wobble plate drive. So far as is known. Sir William's concept was never reduced to practice, and it

Fig. 6.2 Four-cylinder double-acting engine invented by Sir William Siemens in 1863

(after Babcock 1975).

Fig. 6.2 Four-cylinder double-acting engine invented by Sir William Siemens in 1863

(after Babcock 1975).

invented SU years later by van Weenan (1949) in the early days of the Philips program.1"

Different versions of Siemens engines are currently the focus of development effort in Europe and the United States. The Philips/Ford automotive engine is a four-cylinder Siemens engine with a swashplatc drive. The Swedish United Stirling engines are of the Siemens variety using crank-connecting rod drives with four cylinders arranged in a 'square' configuration. The MAN/MWM engines of West Germany utilize in-line or Vee arrangements of Siemens double-acting engines.

Walker (1978b) conceived the free-piston double-acting Siemens engine actually during the course of preparation of this book. Finkel-stein (1978a) has described a numbeT of new concepts and arrangements for multiple-cylinder, free-piston, 'cyclic-compounded' Siemens engines.

DESIGN VARIANTS OF SINGt I- ACTING ST1ULINO ENGINES

All existing arrangements for the single-acting Stirling engine may be broadly classified into two groups: (a) two-piston machines, and (b) piston-displacer machines. A further subdivision can be made in the latter group between machines in which the piston and displacer operate in a single cylinder, and those in which separate cylinders are provided. A representative example of each of these three arrangements is shown in Fig. 6.3. The principal distinction between a piston and a displacer is that there is a large pressure dilferencc between the upper and lower faces of a piston so that a fluid seal is required to prevent the passage of gas from one side to the other. A displacer on the other hand has the same pressure of fluid both above and below, apart from aerodynamic-flow losses. When reciprocating, the displacer does no work on the gas, but merely displaces it from one side of the displacer to the other.

In the case of a piston, the pressure of fluid, above and below it. is not the same, except perhaps momentarily at some point iu the cycle. Work is done on the gas by the piston, or on the piston by the gas. as the piston moves in the cylinder.

In some machines, the displacer is made up (either partly or wholly) by a porous metallic matrix, which itself constitutes the regenerative heat exchanger. Such an element is called a regenerative displacer.

Single-cylinder piston-if is pi acar muchin es

Some of the possible alternative arrangements of single-cylinder piston-displacer machines are shown in Fig. 6.4. This is a particularly favourable

1 In my earliei work. Siirfing Cycle Machines, (O.U.P. l'>73), I inadvertently attnhuted the re-invenlion ol the Siemens engine to H. Rinia of the Philips Co. I now understand the invention was made, in fact, by van Weenan and oiler mv apologies lo Ir. van Weenan herewith G.W.

I 1C. 6.3. Tinec basic arrangements by which most types of Stirling engines may be classiiied la) Piston-dispJaccr in the same cylinder.

(b) Piston-displuccr :n sepárete cylinders.

(c) Two-piston machine.

Single-cylinder piston-displaccr engines

Oscillating

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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