DE102009030173A1 - Stirling machine e.g. heat pump, for converting heat into mechanical energy and vice-versa, has pump mechanism for pumping working fluid to cold and warm zones at low pressure and high pressure - Google Patents

Abstract

The machine has a pump mechanism for pumping working fluid to a cold zone (2) at low pressure and to a warm zone (1) at high pressure, where heating process is applied to heat the working fluid. The pump mechanism is adapted so that the working fluid is squeezed into the cold/warm zone from a pump room by working pistons (4, 5) and sucked back from the cold/warm zone into the pump room. The working pistons are moved with a linear drive (3) that is operated as an engine and a generator.

Description

Affected technical areas

• Hot air engines (Stirlingmotore), chillers and heat pumps (especially according to the Stirling principle), control technology, linear drives

State of the art / description of the defects

Stirling machines in general

When Stirling machines are called machines that convert heat into mechanical ones Work (striling motor) or mechanical work in Heat differences implement (heat pump, chiller) and whose operation is at least similar to the Carnot process.

The The following description refers to Stirling engines described Leave problems and solutions but basically also on heating / cooling machines apply.

Stirling engines in general

Stirling engines generally have a warm and a cold zone. A gaseous working medium is by a displacer alternately transported to the cold / warm zone. Is it in the warm Zone, so it expands, and moves a working piston, the can do work now. Is it in the cold zone, so pull it collapses, and pulls back the working piston.

The Heat is usually through the case fed to the Stirling engine (and removed). Around a powerful one Stirling engine, it is necessary to the surface, if possible big too shape. In order to not let the design too big, this can done by attaching fingers, slats or the like.

Of the displacement promoted the medium from the warm to the cold zone, giving the place itself in the warm zone. It is desirable that the working medium as completely as possible the warm zone is removed, as remaining residual medium itself continues to expand and so the contracting working medium counteracts in the cold zone.

If the warm and the cold zone inside with fingers, slats or the like is equipped, the must displacement Naturally have a corresponding counter-mold so that the working medium between the fingers, the lamellae is displaced as well as possible. This is technically difficult to realize because due of thermal expansion and manufacturing tolerances between the housing and the displacer always Some air must be left. Do you want a big one surface so must, too to be left in many places, you get a big room for residual medium.

Stirling engines are available in different designs. But the two demands have to be in principle always possible well fulfilled but are difficult to reconcile.

Of the The invention is therefore the object of a Stirling engine so to shape that one one possible size surface for one preferably good heat transfer has, but at the same time the working medium as completely as possible which can move one zone into the other zone.

solution principle

The Idea is now not the working medium with a displacer to displace one zone out into the other, but with one Extract the pump from one zone and push it into the other.

One possible realization is in 1 shown. The warm zone ( 1 ) is heated from the outside and is internally equipped with a very large surface in order to achieve the best possible heat transfer. For example, it can be filled with small copper spheres or steel wool. The cold zone ( 2 ) is cooled from the outside and also has a large surface inside.

In 1 is the Stirling engine in the initial state, cold and warm zone are interconnected. First, we assume that the internal pressure is identical to the ambient pressure.

Now the right working piston ( 5 ) by an electromagnetic linear drive ( 6 ) to the left (step 1), as in 2 shown. Because the right working piston ( 5 ) at the gap to the cold zone ( 2 ) has passed, the working medium has now been divided into two parts. One part was moved to the warm zone ( 1 ) and is under pressure there. Due to the overpressure there is a good heat transfer to the working medium. The second part is in the cold zone ( 2 ) and in the piston chamber under negative pressure. Due to the negative pressure, there is a poor heat transfer away from the working medium. The pressure of the working fluid in the warm zone will increase appreciably due to the heating, but the pressure in the cold zone will hardly decrease due to the poor cooling (step 2).

Through the right linear drive ( 6 ) the right working piston ( 5 ) back to the starting point driven ( 1 ). The moment the right-hand piston ( 5 ) at the gap to the cold zone ( 2 ) and the two zones are reconnected, the working fluid would flow from the warm to the cold zone due to the remaining pressure difference. To prevent this and to use the energy as well as possible, the left working piston ( 4 ) driven by the linear drive ( 3 ) to the left to create pressure equality at the moment of opening the gap (step 3).

Now the left working piston ( 4 ) to the right ( 3 ) (Step 4). In the warm zone ( 1 ) there is now negative pressure, there is hardly any heat transfer to the working medium. In the separate cold zone ( 2 However, there is now an overpressure, the medium can cool well (step 5). Finally, the left working piston ( 4 ) back to the left, the right working piston ( 5 ) moves so that at the moment in which the left working piston ( 4 ) reaches the gap, again pressure equality prevails (step 6). The striling engine is back in its original state.

In steps 1-3, work is performed on the linear drives in total by the working pistons. In steps 3-6, the linear drives must deliver work to the working pistons in total. Because the cold zone ( 2 ) has a larger volume than the warm zone ( 1 ), the overpressure in the cold zone in step 5 is consequently lower than the overpressure in the warm zone in step 2, the work from steps 1-3 is greater than that from steps 4-6, so work is done in total ,

Out This description is the context with classic striling motors not yet apparent, but it still exists. We consider hereinafter only the "active" part of the Working medium. Summarizing steps 6 and 1, you get a total of a compression, since the working medium of the larger cold Zone was transported to the smaller warem zone. Step 2 presents the phase of warming steps 3 and 4 can be summarized as an expansion, as the working medium from the smaller warm zone into the larger cold Zone is transported. Step 5 represents the cooling phase. Man receives So overall a sequence, as you get from classic striling motors knows.

By a suitable mechanical structure must be achieved that the pressure always clearly above the negative pressure, thus the heat transfer, in the vacuum zone takes place, always neglected can be.

By a suitable mechanical structure must further be achieved that the pressurized part of the working medium is as completely as possible in the corresponding zone and the smallest possible residue remains in the piston chamber. This is in 2 so not shown, since this is only a schematic representation.

In a striling engine of the type described can already in the starting position an overpressure be introduced, so it can be "charged", as with common Stirling engines is the case. The workflow follows accordingly.

Now imagine, the structure from 1 is again completely umhaust (encapsulated). From this capsule only lines for the two linear actuators and pipes for the heat supply and discharge would go out. These can be sealed easily because they do not move. Now you can just seal the piston rods ( 8th ) omitting. The "inactive" part of the working medium is then directly connected to the medium in the interior of the capsule, which does not affect the function. A slight leak in the piston seals ( 7 ), which can not be completely avoided due to the moving piston, although reduces the performance of the Stirling engine, but does not lead to a loss of working fluid, since this can not escape from the capsule as a whole. Only for some time will the average pressure in the Stirling engine and the pressure in the capsule equalize.

application

One Stirling engine of this type is suitable for almost any Heat sources electricity to create. There just needs to be a sufficiently large temperature difference Otherwise, the efficiency and performance are too low.

Claims (5)

Stirling machine, characterized in that the working fluid can be brought by means of a pump mechanism in the cold zone to a low and in the warm zone to a high pressure, whereby a total of the working fluid significantly more heat than to dissipate, so it heats up. Stirling machine, characterized in that the working medium by means of a pump mechanism in the cold zone on a large and in the warm zone can be brought to a low pressure, thereby a total of significantly less heat is added to the working medium than is dissipated, it cools down. Stirling engine according to claim 1 and 2, since characterized in that the pump mechanism is realized so that the working fluid can be pressed by means of two pistons from the pump room in the cold / warm zone and sucked out of these back into the pump room. Stirling machine according to claim 3, characterized that the Both pistons are moved by a linear actuator, acting as a motor and generator can work. Stirling machine according to claim 3, characterized in that due an encapsulation of the whole machine 5.1 charged this (under Pressure can be set). 5.2 to a seal of the piston rods can be waived. 5.3 a minimal leakage of Piston seals do not lead to a loss of working fluid.