DE102010018616A1 - Device i.e. stirling engine, for converting heat into rotary motion, has rotor rotated vertically with respect to existence of difference in temperature, and turnstile rotatably mounted on pivots - Google Patents

Abstract

The device has multiple deformation elements secured to a rotor (1) that is rotatably mounted on a horizontal fixed axis, where shape of the elements is changed during change in temperature. Pivots (7) are eccentrically and rigidly supported with respect to the fixed axis. A turnstile is rotatably mounted on the pivots, where strong connection is provided between the turnstile and the elements. The rotor is rotated vertically with respect to existence of difference in temperature. The deformation elements are designed as thermal reacting solids e.g. bimetals or shape memory alloys.

Description

Introduction and purpose of the invention:

The invention relates to a method for the conversion of thermal into rotational mechanical energy based on a Stirling cycle process using thermal actuators. The previously little used Stirling engine has some advantages that prove to be beneficial especially in the development of different renewable energy sources. For one thing, he can with any heat source, eg. As solar heat, geothermal or waste heat, operated, on the other hand he (at least theoretically) achieves a relatively high efficiency.

Purpose of this invention should be to modify this heat engine by means of thermal actuators so that they can contribute to the economically meaningful use of renewable energy sources.

State of the art:

The Stirling engine was patented in 1816 by Robert Stirling. Its advantages, such as multi-fuel capability, the utilization of low-temperature heat, the closed system, low vibration and miniaturization, have since brought about ever new modifications. There are types with one or more cylinders, single or double acting and a variety of different engines. There are also exotic designs with oscillating air or water columns or sound waves. Also unbundled solar radiation and thus heat with low temperature can be harnessed. Such low-temperature Stirling engines can in sunny areas to promote water u. a. be used from wells. High-tech versions of the Stirling engine are used in conjunction with parabolic mirrors that focus the sun's rays (Dish-Stirling). In order for the engine to be able to do a lot of work per cycle, some of the gaseous working fluid is compressed up to 200 bar. This in turn results in technical problems in the sealing of the workspace. The necessary use of a regenerator as well as heater and radiator lead to dead spaces, which lower the efficiency of the engine. In addition, the working medium goes through the cycle at such high speeds that it sets itself up so fast that the efficiency is reduced.

Many patent ideas provide a rotationally symmetrical arrangement of many cylinders, so that more work per revolution can be implemented.

There are already attempts to harness thermal actuators in heat engines. In the "bimetallic solar engine" ( US 4,551,978 ) Bimetallic loops are alternately heated and cooled. The expansion of the bimetals causes lifting of the carriage mounted on rods, which releases energy. Here is - similar to many other ideas - the high structural complexity compared to a low performance of the machine.

Shape memory alloys were another hope for new engines shortly after their discovery. The ability to generate electricity from waste heat, geothermal or solar thermal energy generated great interest in "SMA heat engines". In the solution in patent US 3,913,326 For example, loops made of a shape memory alloy (nitinol) are drawn through water baths of different temperatures, whereupon they cool and / or heat alternately and thus become stretched or contract. The rotor mounted on an eccentric causes the actuators to undergo a cyclic process similar to that of a Stirling engine. However, the efficiency of such a machine is very low, which is due, inter alia, to the high friction generated by the shape memory loops when pulled through the water bath. In addition, it comes relatively quickly to the mixing of the two reservoirs.

There are many more similar patents that could never be used profitably. The shape memory effect encloses a small temperature span, whereby the efficiency is limited to 5%. In addition, a sudden change in shape is performed, which can tire the sensitive actuators faster.

The invention is therefore based on the object of obtaining a maximum amount of useful energy from a heat reservoir by means of a heat engine based on thermal actuators. In order to enable economically viable use, a simple structure, with no need for elaborate seals, robustness, the ability to self-start and an efficiency close to the Carnot efficiency to realize.

Solution approaches and essential features:

Various objects are achieved by a construction with the features specified in claim 1. Advantageous developments of the invention are the subject of the dependent claims.

The generation of a rotational movement is inventively by a rotor which is rotatably mounted on a fixed axis, attached thereto several deformation elements, which react to a change in temperature with a change in their shape, one, with respect to the fixed axis eccentrically and rigidly mounted, pivot, a rotatably mounted thereon turnstile and rigid connections between the deformation elements and the turnstile realized.

The deformation elements are preferably hollow bodies filled with a fluid or wax or other shape-changing agent, which transfer the change in volume of the shape-changing agent when the temperature changes via a working piston into an area outside the cylinder - referred to hereinafter as expansion work elements. Other possible elements consist of shape memory alloys, bimetals or other solids with a useful coefficient of thermal expansion. Advantageous properties are high volume work and high thermal conductivity of the forming agent. In one possible approach, expansion work elements filled with paraffin are used. During the phase change from solid to liquid, the paraffin increases its volume by about 15%. If this change is blocked, very large forces can be built up. The amount of heat needed to melt paraffin is quite high (about 200 KJ / kg). Therefore, these Dehnstoffarbeitselemente mechanically quite sluggish.

The rotor is a rotationally symmetrical body and preferably consists of a solid, poorly heat-conducting material. The connection between the rotor and the deformation elements can be made rigid or movable, but in any case so that the forces resulting from the change in shape can be absorbed. Ideally, no heat is transferred from or to the rotor, which can be approximately realized by an additional insulating layer.

The pivot and the turnstile mounted thereon are eccentric and rigidly mounted to the axis of the rotor and connected to the forming means so that the forces resulting from the change in shape can be absorbed. Ideally, turnstile, pivots and joints are also thermally insulated with respect to the strain elements and their surrounding medium.

Through this entire mechanical construction is realized that at a temperature increase in a certain area there located the deformation elements react accordingly, so expand or pull together, but which, by attachment to the rotor and turnstile, can only be performed by rotation of the rotor - There is a torque on the rotor. Meanwhile, the next forming elements mounted on the rotor are conveyed to the higher temperature region and undergo the same cycle. Meanwhile, all already heated strain elements are cooled again and returned to the state before heating. As a result, a cyclic process is carried out.

This principle of several radially symmetrically arranged deformation elements and the achieved by the connection with a rigid eccentric upon rotation cyclic deformation is already in US 3,913,326 and WO 2008/064614 A1 explained. Nevertheless, this solution differs according to the invention of US 3,913,326 in that the rigid axis is aligned horizontally and thus the rotor rotates vertically. In addition, the differently tempered areas, unlike in WO 2008/064614 A1 horizontally separated from each other, that is, in the vertical direction is below the cooling and above the heated heat transfer.

According to the invention, there is a regenerator between these two regions, that is to say a heat carrier with low vertical and high horizontal heat conduction. If the pivot is only offset in the horizontal direction with respect to the axis of the rotor, a Stirling cycle is carried out during one rotation. The four state changes, isothermal expansion in the hot region - isochoric cooling - isothermal compression in the cold region and isochoric heating, run (as with the Stirling engine) with the limitations that the stroke changes sinusoidally and therefore all processes are approximated only to the ideal. On the other hand, running through the processes slowly is an advantage over the Stirling engine with gas as the working medium, as this leaves more time for the transfer of heat.

The heating and the cooling heat carrier touch the deformation elements, so that it comes to heat transfer. Advantageously, a high volume-specific heat capacity and high thermal conductivity of the heat carrier, so that much heat can be transferred at the contact point. In a first approach, the use of a liquid, for. As water provided. The problem of mixing hot and cold areas like in US 3,913,326 is solved by the vertical structure and the resulting vertical layering of the temperature. With slow rotation of the rotor, such as using paraffin-filled expansion elements, this stratification is hardly affected by resulting flows.

In another approach, the separation of heating and cooling Heat transfer fluid through the use of two or more immiscible liquids, eg. As oil and water, even better prevented. The hot oil floats on the water and is thus - separated from the colder area - above.

Another approach involves the use of solids exclusively or in addition to a fluid as a heat transfer medium. Good heat conducting materials, such as preferably aluminum or copper, are arranged in the layer structure with thermal insulators so that the horizontal heat conduction is improved and the vertical heat conduction is deteriorated.

The hot heat transfer area should be thermally insulated from the environment, which can be realized by various types of insulation. The cooling area can either be covered with a good heat conductor and cooled by the environment (passive cooling), or by an additional cooling circuit and / or fans (active cooling).

Presentation of the solution advantages:

The advantage according to the invention lies in the ability of the heat engine to potentially extract the highest possible proportion of useful energy from a heat reservoir. The theoretical Stirling cycle is approximated very well, which is ensured in particular by the slow rotation and the resulting long time for heat transfer and low friction losses. In addition, there is no dead volume during the process, which would reduce the efficiency.

The simple, inexpensive construction can be realized in different sizes. There are only minor maintenance required, because piston seals are not needed. The conversion of rotational energy into electrical current can be done via an additional translation and a generator.

The engine, like any other Stirling engine, does not require a specific heat source and is therefore suitable for the use of renewable energies. Furthermore, the use of low temperature heat is an advantage of the system. Thus, the spectrum of possible heat sources can be extended to waste heat, geothermal energy and unconcentrated sun rays. The heat transfer medium can be introduced directly into the system without additional heat exchangers.

The heat engine starts from a certain temperature difference by itself, which makes a complex automatic start superfluous. Thus self-sufficient systems can be realized.

EXAMPLES

All subsequent descriptions of an embodiment of the invention have only exemplary character, according to which all listed features in this form are not necessarily necessary for the realization of the invention.

Further features of the solutions according to the invention will become apparent from the dependent claims, the following description of an exemplary embodiment and the accompanying drawings. It shows:

1 : Schematic representation of the side view of the engine with exemplarily selected eight deformation elements, carried out as filled with a shape change means cylinder, which are preferably according to the invention evenly spaced from each other.

2 : Schematic representation of a re 1 horizontal cross-section

3 : Possible arrangement of several machines for power amplification.

In 1 the engine is shown schematically in the side profile. The mechanical construction is surrounded by the heat transfer medium ( 8th . 9 . 10 ). In this case, in the vertical direction above, the heating medium ( 8th ), below the cooling ( 10 ) and therebetween is the medium with layer by layer rising temperature ( 9 ), which acts as a regenerator. If the heat transfer medium is a fluid, an enclosing housing must separate it from the environment. The entire mechanism is mounted horizontally on one axis ( 6 ). On it is the rotatably mounted rotor ( 1 ). At this are strain elements, exemplified by eight with a shape-changing means such. B. Paraffin ( 3 ), filled cylinders ( 2 ) shown attached. In these expansion work elements is via a working piston ( 4 ) and in the further a connecting rod ( 5 ) transferring the shape change of the shape-changing agent out of the cylinder to the outside. In this approach, comparatively simple membrane seals are sufficient. A further illustrated component is the pivot ( 7 ), so over a turnstile ( 11 ) with the connecting rod ( 5 ) and is connected to the expansion work element that in the change in shape of the shaping agent ( 3 ) can be absorbed ( 2 ). Decisive for the emergence of a rotation is the relative to the axis ( 6 ) eccentric bearing of the pivot ( 7 ). Thus, the Dehnstoffarbeitselemente are alternately in a retracted and extended state during a revolution. Through this entire mechanical construction is realized that at a temperature increase in the heated area ( 8th ) The deformation elements located there react, so expand in the case shown. However, this can be performed by the attachment to the rotor and turnstile, only by a rotation of the rotor counterclockwise - it creates a torque on the rotor. Meanwhile, the next forming elements mounted on the rotor are conveyed to the higher temperature region and go through the same cycle. Meanwhile, all already heated strain elements are cooled again and returned to the state before heating. In 1 and 2 a Stirling cycle is carried out because the trunnion ( 7 ) is located horizontally from the axis ( 6 ) and thus by the arrangement of the heat baths ( 8th . 9 . 10 ) the typical sequence of isothermal expansion in the heating area ( 8th ), isochoric cooling in the regenerator ( 9 ), isothermal compression in the cooling area ( 10 ) and isochoric heating in the regenerator ( 9 ). The regenerator must have very good horizontal and poor vertical heat conduction, because ideally the heat given off to the heat bath during isochronous cooling must be returned to the same level at isochoric heating on the other side of the rotor. In order to increase the horizontal heat conduction, in addition to the use of highly conductive materials, an arrangement of several machines, as in 3 shown. The path between cooling and heating in the regenerator is shortened by two rotors rotating side by side in the same direction. This will potentially transfer more heat with less material usage. In addition, in 3 shown in the vertical direction one above the other machines. This is a conceivable configuration when there is a high temperature gradient between the hot and cold sides of the motor and there are several different shape modifiers needed to convert them into a rotary motion.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 4551978 [0005]
• US 3913326 [0006, 0015, 0015, 0017]
• WO 2008/064614 A1 [0015, 0015]

Claims (8)

A device for converting heat into a preferably rotational movement, implemented by a rotor rotatably mounted on a fixed axis, attached thereto a plurality of deformation elements which respond to a change in temperature with change in shape, a, with respect to the fixed axis eccentrically and rigidly mounted pivot rotatably mounted turnstile and rigid connections between the deformation elements and the turnstile, characterized in that the fixed axis is mounted horizontally and the rotor rotates in the presence of a vertical temperature difference. Device according to claim 1, characterized in that the deformation elements comprise expansion work elements, d. H. preferably with a wax and / or fluid-filled hollow body with working piston and sealing to the environment are. Apparatus according to claim 1, characterized in that the deformation elements are thermally reacting solids, preferably bimetals or shape memory alloys. Device according to one or more of the preceding claims, characterized in that the heat transfer medium surrounding the deformation elements is in the form of one or more non-miscible fluids of different densities, so that the temperature increases in a vertical upward direction in layers. Apparatus according to claim 4, characterized in that the heat carrier is supplemented by additional solids preferably in the layer structure. Device according to one or more of the preceding claims, characterized in that the axes of several such devices are preferably on the same horizon and next to each other and the direction of rotation of the rotors is the same. Device according to one or more of the preceding claims, characterized in that a plurality of such devices lie on one axis and the direction of rotation of two adjacent rotors is in opposite directions. Device according to one or more of the preceding claims, characterized in that the axes of several devices lie on different horizons.

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