Regenerative Displacer Engines

Another model engineer interested in the Stirling engine is W. D. Urwick, of Malta, who has undertaken an extensive program of testing the regenerative displacer. In the Urwick design, the conventional displacer is replaced by a series of screen discs mounted on the displacer shaft, which act as a regenerator. Urwick (1975) reported various experiments in which the engine tested performed as well or better with this regenerative displacer than with a conventional displacer, despite the greatly reduced compression ratio accompanying the change. Discolora-

tion of the screen discs suggested that a very even temperature gradient is maintained between the discs. Other experiments showed the effect of greatly increased dead volume on engines with very low compression ratios.

l.ater Urwick (1977) described a number of different engines incorporating his type of displacer, including one with a swash-plate and several with nutator (wobble-plate) drives. An Urwick engine of 5 cm1 (0.3 in1) design is shown in Figs. 20.4 and 20.5. He has resisted the temptation, sometimes strong among model engineers, to pursue every new idea. Rather, he has continued carefully and patiently to explore this regenerative displacer idea, in an effort to realize whatever potential it may have.

Collins (1977) has also developed a regenerative displacer engine. This very interesting 5.5 watt 5 cm* (0.3 in5) engine operates on air at just over 0.6 MN/ni'1 (90lb per sq in.), and incorporates a simple but effective shaft seal that permits runs of up to 56 hours without supplemental pressure. As with most model engines, this machine has been tested in several different configurations. Some tests were made with conventional displaces, and others with regenerative displacers.

Etc.. 20.4. Model Stirling engine with regenerative displacer by W. D. Urwick (I975).

Malta Stationary Engines
Fig. 20.5. Cross-section of Urwick engine with nutator drive.
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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