WO2005108769A1

WO2005108769A1 - Reciprocating engine with cyclical displacement of working medium

Info

Publication number: WO2005108769A1
Application number: PCT/GR2005/000015
Authority: WO
Inventors: Leonidas Tsikonis
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-05-06
Filing date: 2005-05-04
Publication date: 2005-11-17
Anticipated expiration: 2006-11-06
Also published as: GR1004921B

Abstract

A reciprocating engine that functions following thermodynamic cycles such as the CARNOT, STIRLING and OTTO after appropriate modifications. Its main characteristics are that it consists of a number of chambers equivalent to the phases of the thermodynamic cycle it follows in each instance and that for the approach of the theoretical cycle a displacement of the working medium from chamber to chamber in a cyclical pattern is performed. The cylinders are interconnected by pipes and their pistons are connected to a crankshaft with a 180° phase difference. During the shaft rotation the working medium is displaced from cylinder to cylinder and at the same time moves to a different phase of the thermodynamic cycle. The cylinders have different piston displacements, which correspond to the volume of the working medium at the end of each thermodynamic process. The thermal exchanges between the working medium and the hot and cold reservoirs as well as among phases of the thermodynamic cycle are carried out by heat exchangers introduced to the pipes. The engine can be used for the production of mechanical or cooling work.

Description

Reciprocating engine with cyclical displacement of working medium

The invention is about a reciprocating engine the function of which may follow thermodynamic cycles such as the CARNOT, STIRLING and OTTO cycles. Its main features are that it consists of a number of chambers equivalent to the number of phases of the thermodynamic cycle it follows in each instance and that for the approach of the theoretical cycle a displacement of the working medium from cylinder to cylinder in a cyclical pattern is performed.

Until now there have been efforts to approach thermodynamic cycles of high thermodynamic efficiency such as the CARNOT and the STIRLING cycles. Especially in the case of the STIRLING cycle, a piston engine has already been developed which is widely used in research as well as in practical applications. The main disadvantages of the aforementioned engine are firstly its complexity and the difficulty to approach the isothermal process, which is carried out with the use of heat regenerators.

For CARNOT cycle several suggestions have been made. Such examples are the rotary engines that are described in the inventions Patent Number US5325671 and US3867815 or piston engines with particularly complex mechanisms such as the ones described in the inventions Patent Number JP52037645 and DE4429616. There is also the invention Patent Number JP4054264 in which an engine comprising of four cylinders corresponding to the four phases of the CARNOT cycle is suggested. Contrary to the aforementioned inventions, no specific engine layout seems to be suggested in the drawings but there is only a theoretical projection of four cylinders, which exchange fluids in a particularly complex manner. In other words, there is no suggestion of practical application of the invention. In the abstract it is stated that the cylinders follow an "airtight ring" layout, which is not clearly depicted, but even in this case balancing problems would occur due to non-uniformities in its operating cycle.

The present invention faces all the aforementioned problems and at the same time differs from all previous inventions. The concept and the suggested mechanism are simple. Moreover with the present invention issues concerning the air-tightness of the working medium and the engine balancing are examined and resolved. Finally, as shown in the following drawings and examples, with the present invention and with simple modifications, the CARNOT, STIRLING and OTTO cycles may be approached, a fact that offers great potential in its use.

The present invention (reciprocating engine with cyclical displacement of working me- dium) consists of cylinders with pistons connected to a crankshaft. The cylinders have different piston displacements, which correspond to the volume of the working medium at the end of each thermodynamic process in the thermodynamic cycle followed. The real volumes are not necessarily equal to the theoretical ones because the quantities in the connecting pipes as well as the real thermodynamic properties of the working me- dium must also be calculated. The piston connecting rods are attached to the crankshaft with a 180° phase difference, that is, when a piston is at its lowest point, the adjacent piston(s) are at the highest point of their movement. The cylinders are interconnected by pipes in order for the working medium to move from chamber to chamber during the crankshaft rotation. But since the working medium has to circulate in the pipes in a specific direction only, a suitable valve system is installed in the pipes - elec- trovalves, for example, controlled by a corresponding control system. The valve system allows the working medium to move in the direction imposed by the thermodynamic cycle. Depending on the length of the pipe, the number of valves used may be either one per pipe or two valves per pipe, one at each end. The heat exchanges between the working medium and the hot and cold reservoirs or among different thermodynamic states of the working medium are carried out by heat exchangers that are introduced between the cylinders and connected with the pipes.

As it has already been mentioned, the present invention examines and faces several issues of a practical nature. One of these problems is the air-tightness of the engine, which is resolved as follows: Firstly, the cylinder and crankshaft assembly is enclosed in a hermetically closed housing so as to avoid leakage of the working medium. Secondly, a pressure reset device allows reversion of a quantity of the working medium from the crankshaft area to the cylinders in case of leakage of the working medium from the chambers to the crankshaft area due to insufficient air-tightness of the pistons. Thirdly, the airtight housing includes a reduction gear and an electric generator, so that the mechanical work produced on the crankshaft is released by the engine in the form of electrical energy. The same happens when energy is delivered into the engine shaft. It should be mentioned that the great importance attributed to the air-tightness of the engine has to do with the possibility of this latter to use, as a working medium, gases such as helium or hydrogen, which present excellent thermodynamic properties and a behavior very similar to that of the ideal gases. Another issue is the lubrication of the engine, which may be carried out with the known lubrication methods applied in modern piston engines. Finally, the layout suggested by the present invention permits the easy balancing of the engine by means of counterweights on the crankshaft or an extra or more groups of cylinders and pistons or via other methods applied in modern piston engines.

The following examples and attached drawings describe the invention.

Figure 1 presents the CARNOT thermodynamic cycle on a pressure (p) - volume (v) diagram, which will be approached in the first example. As shown, the CARNOT cycle consists of an adiabatic compression (process 1-2), an isothermal expansion (process 2-3), during which the working medium receives heat (Q^ from the hot reservoir, an adiabatic expansion (process 3-4) and closes with an isothermal compression, during which the working medium releases heat (Q₂) to the cold reservoir. The theoretical work of this cycle equals the heat received by the working medium minus the heat released.

Figure 2 presents a schematic diagram of an engine of discrete phases that approaches the CARNOT cycle. It shows the four cylinders (5, 10, 16, 20), which corre- spond to the four characteristic volumes of the theoretical cycle, the pipes (7, 8, 12, 18) through which the working medium moves from one chamber to another and, consequently, from one phase of the cycle to another, the valves that control the direction of the working medium flow (6, 9, 11, 15, 17, 19), the heat exchangers for the isothermal expansion (13) and the isothermal compression (14), the system of connecting rods, bearings and crankshaft of the engine (25) and the reduction gear (24) and generator (23) system for the production of electricity. It also shows the pressure reset device that returns working medium escaped to the crankshaft area due to leakage, which includes a pipe (22) and a suitable valve (21) which is activated when reversion is needed. Figures 3 up to 6, depicting the four phases of the engine operation cycle, show in greater detail how the function of the aforementioned layout approaches the CARNOT theoretical cycle. In Figure 3 due to the rotation of the crankshaft and the layout of the cylinders the working medium is displaced from chamber 26 to chamber 28 through pipe 27. The transfer is adiabatic. In fact, the cylinder piston displacements are such that the process is actually an adiabatic compression that approaches the process 1-2 in Figure 1. In Figure 4 the shaft rotation and the piston movement continue resulting to 5 the displacement of the working medium concentrated in cylinder 29 to chamber 32 through pipe 30 and heat exchanger 31. During this phase the working medium receives heat isothermally and the cylinder piston displacements are such that process 2- 3 of Figure 1 is approached. In Figure 5 the process 3-4 of Figure 1 is approached, i.e. adiabatic expansion, via an adiabatic movement of the working medium from chamber

10 33 to the larger volume of chamber 35. The last process (4-1) of the thermodynamic cycle shown in Figure 1 is a result of the isothermal compression described in Figure 6, where the working medium moves from chamber 39 to chamber 36 through pipe 37 and heat exchanger 38. The aforementioned process concerns the production of mechanical work. If this process is reversed, the engine can be used for the production of

15 cooling work following the CARNOT cycle in the opposite direction. The drawing in Figure 7 presents a simplified example of application of the reciprocating engine with cyclical displacement of working medium. The engine in this example has two series of cylinders on both sides of the crankshaft. The numbers refer mostly

20 to the upper array of cylinders. The Figure shows the chambers (41, 51, 59, 61), their pistons (43, 52, 58, 62), the connecting rods (42, 65, 66, 67), the crankshaft (68) and the engine housing (40) which ensures the air-tightness of the engine and thus prevents any working medium leakage to the environment. It also presents the cylinder heads (44, 48, 57, 60) whose form ensures the least possible losses during the transfer 5 of the working medium between chambers and through the pipes (45, 46, 50, 54, 55). Finally, Figure 7 shows the valves that control the flow in the pipes (47, 49, 53, 56), the reduction gear (63) and the generator (64). Figures 9 and 11 present a few examples that make clear the potential of adjustment of 30 the reciprocating engine with cyclical displacement of working medium in order to follow the STIRLING (Figure 9) and OTTO (Figure 11) cycles. These versions present a different cylinder layout than the one shown in Figure 2. That is for space saving and due to different balancing. Nevertheless, the engine works on the same principle. Figure 8 shows the STIRLING thermodynamic cycle on a pressure (p) - volume (v) dia- 35 gram, characterized by two isothermal and two constant-volume processes, on a pressure (p) - volume (v) diagram, while Figure 10 shows the OTTO cycle, characterized by two adiabatic and two constant-volume processes. The symbols Q₁ and Q₂ correspond, respectively, to the heat received and released by the working medium from the hot reservoir or to the cold reservoir, while Q₃ symbolizes the heat transferred between 0 different quantities of the working medium during the constant-volume processes.

Claims

1. Reciprocating engine with cyclical displacement of working medium characterized by a number of chambers equivalent to the number of phases of the thermodynamic cycle that is followed during its operation.

2. Reciprocating engine with cyclical displacement of working medium, in accordance with Claim 1 , characterized by cylinders with different piston displacements and that each volume corresponds to the volume that the working medium has at the peaks of the pressure-volume diagram of the thermodynamic cycle followed.

3. Reciprocating engine with cyclical displacement of working medium, in accordance with Claim 1 , characterized by the fact that the cranks of the crankshaft are joined with the piston connecting rods in such a way that the piston of each cylinder has a 180° phase difference with the pistons of the previous and next cylinder in the engine operation cycle.

4. Reciprocating engine with cyclical displacement of working medium, in accordance with Claim 1 , characterized by pipes which connect the adjacent cylinders as well as the first with the last one and allow the working medium to move from one cylinder to another in a cyclical pattern.

5. Reciprocating engine with cyclical displacement of working medium, in accordance with Claim 1, characterized by a valve system and a suitable valve control system which allow the working medium to move from one cylinder to another in a single direction and at the right moment for the correct operation of the engine.

6. Reciprocating engine with cyclical displacement of working medium, in accordance with Claim 1 , characterized by heat exchangers for the heat exchange between the working medium and the hot and cold reservoirs of the thermodynamic cycle or among different thermodynamic states of the working medium.

7. Reciprocating engine with cyclical displacement of working medium characterized by a suitable hermetically closed housing which encloses all the moving parts of the engine so as to avoid working medium leakage from the engine to the environment.

8. Reciprocating engine with cyclical displacement of working medium, in accordance with Claims 1 and 7, characterized by the presence of a reduction gear and a generator within the hermetically closed housing in order to release the mechanical work produced by the engine in the form of electrical energy so as to avoid working medium leakage from the engine to the environment.

9. Reciprocating engine with cyclical displacement of working medium, in accordance with Claims 1 and 7, characterized by a device for the restoration of the pressure in the crankshaft area and the return of a quantity of the working medium from this area to the interior of the cylinders.