Power plants – Motor operated by expansion and/or contraction of a unit of... – Unit of mass is a gas which is heated or cooled in one of a...
Patent
1999-05-06
2000-12-19
Nguyen, Hoang
Power plants
Motor operated by expansion and/or contraction of a unit of...
Unit of mass is a gas which is heated or cooled in one of a...
60524, F01B 2910
Patent
active
061613819
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a Stirling engine with a cylinder head which can be heated with a plurality of heating pipes bent in approximately U shape and with a cooler for the working gas.
Stirling engines are known in a number of forms; DE 4 016 238 C2 is here cited as an example, as a combination of such an engine with a boiler installation.
The basic principle of such a Stirling engine consists in that a constant volume of gas (helium is used mostly today) is forced to and fro within the Stirling engine by two pistons. On the one side the helium is heated in the heating pipes by the flame of a gas burner and the other side is cooled by a cooler. In between there is a regenerator, which extracts heat from the gas in its path from the hot side to the cold and feeds it back during the return flow. A gearbox connects the two piston so that power can be taken off, e.g. through generators. The pistons are moved alternately in parallel with or in opposition to one another, whereby the gas is compressed by the one piston and expanded again after the heat input by the other.
In addition to mechanical problems there is a perceived problem area on the one hand in optimizing the transfer of heat from the flame of the burner to the heating pipes and on the other hand in optimizing the cooler. A Stirling engine is known from DE 2 821 164 A1. The hot gas engine disclosed there is concerned not with the energy problems in the foreground here and this applies also to other solutions described in the state of the art. Thus for example DE 3 444 995 A1 shows a cyclone device with corresponding flow engines.
Furthermore, coolers are known from DE 4 232 555 A1 or for example from DE 4 401 247 A1 whose cooling bodies are provided with an outer, surrounding, helical groove traversed by the coolant. Such cooling bodies provided with a helical groove are comparatively expensive to make and in addition the coolant is always heating up as it passes through the helical groove, so that such cooling bodies cannot be optimally designed.
SUMMARY OF THE INVENTION
The object of the invention is to optimize the energy balance in a Stirling engine, and to improve the transfer of heat at the heating pipes and the efficiency of the cooler.
This object is met according to the invention in a Stirling engine of the kind initially defined in that the outwardly facing pipe sections of the heating pipes through which the working medium flows are provided at least locally with a ceramic backing for optimization of the flow of the heating gas.
With the construction here under discussion a heater usually comprises two coaxial rows of pipes, which are arranged concentrically in circular form and are joined by pipe bends into U-shaped heater pipes, wherein the pipes are connected at one end to the expansion chamber and at the other end to the regenerator.
The pipe rows arranged in a circle are favorably alongside each other in terms of heat transfer technology on the inside but the outer pipe rows are automatically spread apart because of the geometrical situation, so that the exhaust gas flow slows down in the interstices and the heat transfer becomes worse. As also shown in the reference defining the type in question, assistance has been obtained previously in that the outer pipes are designed as ribbed pipes, in that heat transfer ribs are soldered on for example, which necessarily involves substantial costs and thus cannot be justified economically.
Through the backing according to the invention with ceramic flow guiding elements, as representing a ceramic backing, optimization of the flow around the outer pipes is achieved with economically acceptable means.
The elements of the ceramic backing are advantageously formed from ceramic profiled elements approximately T-shaped in cross-section, where the T limb projects from the outside inwardly between adjacent pipes and the T crosspiece covers the pipes locally on the outside. At this point it should be noted that flow guiding elements on cooling pipes are known per se,
REFERENCES:
patent: 5664945 (1997-09-01), Maynard et al.
patent: 5755100 (1998-05-01), Lamos
Nguyen Hoang
SIPRA Patententwicklungs- u. Beteilgungsgesellschaft mbH
Striker Michael J.
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