Energy Sources Adoption Technologies
Energy Converter Stirling Engine

As noted energy converter technologies are crucial in distributed power generation systems; and one of the energy converter technologies is one-cylinder Gas Engines. Although energy converter gas engines, as a technology class, provides a general approach to converting heat energy into mechanical energy or potential, the use of such engines is severely limited by several factors that limit the application in energy technologies:

• Rapid transfer of heat into the gas
• Rapid removal of heat from the gas
• High heat source temperature of operation
• Precision Displacer Piston Cylinder-Wall spacing for high drag force piston displacement
• Design of Cyclicity or Flywheel Device to support cyclic operation
• Initial activating piston placement for heat zone initiation.

In addition to these factors is the complexity of the piston rod return force balance engineering analysis required to ensure the cyclicity of the engine operation.

However, each design that has addressed each of the factors and has provided significant improvement has contributed to an innovative design of gas engines. One particular such innovative design resulted in the special gas engine commonly known as the Stirling Engine, which significantly shortened the time to raise the gas temperature to operating temperature through the use of a Regenerative heat exchanger within the engine. In operation, the regenerator serves as an internal heat storage device, during the heating cycle and then transfers the heat to the gas after the cooling cycle, therefore bring the gas temperature closer to the operating temperature before the start of the next heating cycle.

Yet, the actual problem of enhanced heating by higher rate of heat transfer into the gas really was not solved by the regenerator.  Plausibly though, such issue of rate of heat transfer into gas can be reasonably resolved with the radiative transfer and heating heat-source design.

Basic Converter Stirling Engine Design
Given that a Stirling Engine is an improvement on a gas engine consisting of the incorporation of a regenerator, then for all intents and purposes, an Energy Converter Stirling Engine can be developed from the energy converter gas engine by the simple integrating a regenerator into the gas-engine design.

Regenerators of several varied forms and designs have been developed and adopted Stirling Engines over the years. All the same, in adopting a design in this report for the purposes of constructing a configuration, concept design of consideration being adopted is not encumbered with intellectual proprietary rights, as such have long-expired. Of course, such could therefore be subjected to prospective design innovation without interference while also covering the configuration being presented as under possible intellectual property rights.

Basic Regenerator Heat Exchanger Design
A design of regenerative heat exchange that meets the objects of Stirling Engines must necessarily be placed between bounds of the heating zone of the engine, or in the extreme case be placed at the virtual interface between the heating and cooling zones.  In any event, given the design of a regenerative heat exchanger based on the commonly referenced design of regenerator using screen as the heat storage device, the placement is made in the Displacer Piston.

Effectively, the regenerator configuration being presented is based on the use of screen. The regenerator by configuration consists of a high temperature ceramic matrix of the shape of a thread bobbin,  and with a tubular cylindrical core. The flanges of the bobbin are perforated to enable flow through of fluid, but the perforations of each flange are misaligned with the perforations of the other. The misalignment has the object of aiding mixing. The cylindrical rod between the flanges is wrapped with a continuous roll of screen-mesh and thinly weld-secure and flush with the flanges radial boundaries.

Integration of the regenerator into the piston is accomplished by embedding. More specifically, the regenerative heat exchanger is fabricated into the Displacer Piston and made part of the piston. As a further support of the functionality of the heat exchange process, the section of the piston below the regenerator is also perforated but in alignment with the perforations of the nearer ceramic flange of the regenerator bobbin. The radial span of the bobbin is also by design flush with the piston at the radius, resulting in a uniform lateral surface.

During operation of the engine, the full displacement-force due to the expanding gas is impressed on the piston upper surface. However, during the return cycle impelled by the flywheel mechanism, some of the gas flows through the lower perforations into the screen and then out laterally back into the gas mix; and in the process is heated by the heat energy transferred from the screen.

The performance of the regenerator, of course,  depends on the details of the configuration as defined by the screen. Each configuration of the regenerator however, obviously is impacted by several factors such as the mesh wire size and the mesh size, as well as the thermal characteristics of the material of which the wire is made. Evaluation of the screen properties, however, is also not easy by any means, because several features must be evaluated in synchronization and used to size the screen mesh size and wire size. The evaluation of the screen characteristics relative to the overall performance of the regenerator is guided by the rate of flow through the perforations of the flanges, the design engine-cycle start-temperature and rate of heat transfer before the prevalence of cycle start state, and the duration of piston displacement during heat transfer. The tasks are not easy and must evaluated only with unsteady state heat transfer analysis.

Admittedly, just a specialization of a well known standard design material has been incorporated in the regenerator, and indisputably regenerators of several varied forms and designs have been developed and adopted in Stirling Engines over the years. Even then, the careful fabrication of the design presented here in the energy converter gas engine should provide an efficacious energy converter for the integration of distributed power generation systems. Remarkably, in all of these technologies, the primary task accomplished is use of the simple one-cylinder engine to effect the  conversion of heat energy into mechanical energy or potential.

Attempts to shorten the heat transfer  lag-time with innovative regenerators continues to remain a formidable area of research. This reason has been singularly accountable as well for the lack of use of the technology in high torque drive-mechanisms.  Hence, there is still opportunity to innovate in this regards; although, each design will come with its demands and characteristics and as such different set of factor for consideration.

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