498 Stirling Engine Burnerpreheater Cross Section

E:IO. 7.to. Cross-section of Philips-Ford 4 98 Stirling engine hurner preheater.

Regenerative heat exchangers olfer the prospect of air preheaters that are lighter in weight, less bulky, cheaper, and with reduced tendency to fouling than recuperative exchangers.

Regenerative exchangers are used in the Philips/Ford multicylinder engines with swashplate drive which are under development for automotive use. Fig. 7.16 is a cross-section of the hot parts assembly of a Philips/Ford automotive Stirling engine showing the regenerative heat exchanger (called on the drawing the preheater core). Similar units are incorporated in Stirling engines for automotive use being developed by United Stirling of Sweden.

In all these cases the regenerative exchanger is of the form of the 'thermal wheel' shown in Fig. 7.17. A flat disc of porous matrix material, usually ceramic but sometimes metal, is contained within two adjacent ducts through which the hot and cold fluids are passing. The axis of the disc is parallel to Ihe fluid motion. The disc is caused to rotate slowly so that a given element of the disc moves alternately through the exhaust gas and inlet air streams and a regenerative heat exchanger is thus created. If the fluid flows are in opposite directions an appreciable self-cleaning effect is obtained.

The 'thermal-wheel' regenerative heat exchanger has been studied extensively tu connection with the development of gas-turbine engines for vehicular applications, and the technology is directly applicable to ihe Stirling-engine air preheater. The disc may be fabricated from any

I*IG. 7.17. Thermal wheel* regenerative heat exchanger

suitable porous material but ceramic materials arc preferred. This is because their extremely low coefficient of thermal expansion endows the ceramic thermal wheel with the potential capacity to sustain extended use while experiencing repeated thermal and cooling cycles when rotated in the hot and cold fluid streams. In many metallic materials, the repeated heating and cooling causes cracks to appear and distortion to occur, a condition described generally as thermal fatigue.

The vehicular gas turbine literature contains many papers relating to thermal-wheel regenerative heat exchangers and progress is reported regularly at the semi-annual Vehicle Contractor Coordination meetings of the U.S. Department of Energy, the American Society of Mechanical Engineers International Gas l urhine Conferences, and the Annual Inter-society Energy Conversion Engineering Conferences.

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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