SE467837B - ENERGY CONVERTERS WORKING ON STIRLING- ERICSSON OR SIMILAR THERMODYNAMIC CYCLES - Google Patents

Description

467 857 10 15 20 25 30 35 2 is reduced at all or at least not in proportion to the reduction in power, so that the efficiency of the engine is significantly reduced. This working condition with reduced efficiency lasts the time the gas pump needs to pump the required amount of working gas back to the pressure vessel.

Other ways of rapidly lowering the power of energy converters exist, such as dead volume control, ie switching on and off of secondary spaces at constant average pressure, but they are either too slow, too complicated or subject to other limitations, not least spatial, such as makes them impractical to use. The object of the invention is to provide an energy converter which enables rapid control of the output without major efficiency losses occurring.

The energy converter must also be simple in its construction and, if required, can be made very compact and light.

This object is achieved according to the invention by means of at least one low-pressure container housed in the energy converter and filled with working gas, in which the gas pressure is substantially below the mean pressure and which is connected partly to the inlet side of the gas pump and via the valve (s) for controlling the mean pressure reduction with the energy converter cylinder , whereby the total volume of the low-pressure tank (s) is significantly larger than the stroke volume of the energy converter.

By connecting a relatively large low-pressure container between the valve for reducing the average pressure and the inlet of the gas pump according to the invention, large amounts of gas can be drained from the energy converter cylinder / s in a very short time, regardless of the gas pump capacity. The only requirement for the gas pump is that it must be able to ensure that there are sufficiently large pressure differences between the high-pressure tank and the energy converter's cylinder (s) and between the cylinder (s) and the low-pressure tank (s), which in practice means that compared to technology position can often choose a slightly smaller pump, which can for example be accommodated in the crankcase of the energy converter and can then be driven directly by the crank mechanism of the energy converter.

The most advantageous arrangement is achieved if the crankcase of the energy converter is used as a low-pressure container, since the volume of the crankcase generally has a size suitable for the purpose and it is therefore not necessary to increase the dimensions of the energy converter. The relatively low pressure in the low-pressure container (crankcase) also means that one can choose a favorable, small wall thickness in terms of weight and that the crank mechanism is not significantly affected due to the relatively thin atmosphere.

If it is desired to further reduce the dimensions of the energy converter, the high-pressure container is suitably also arranged inside the energy converter. In the case of energy converters with a dome-shaped displacement piston, this can be achieved by using the displacement piston as a high-pressure tank.

Several containers or volumes with both high and low pressure can be arranged in modulated pressure stages with gas pumps, which regulate the mutual pressure between the volumes. This has the advantage that the constituent volumes can be optimally pressurized with regard to their strength and wall thickness, for example if a fully encapsulated energy converter uses a magnetic shaft coupling that requires a thin partition between the driving and the driven unit, or with regard to the risk of leakage. of working gas to the environment, for example if you use a continuously rotating shaft in the crankcase with a shaft seal against the environment.

The invention can also be used to advantage for energy converters which in themselves integrate a Stirling motor as a drive source, and a heat pump or cooling machine of the Stirling type as a driven unit. The effects in the driving and driven units can be modulated by ensuring that the average gas pressure in the driving unit differs in a suitable manner from the average gas pressure in the driven unit, so that the desired effects are achieved. At the same time, the pressure in the crankcase can be kept at a relatively low level. In the crankcase, a mechanically driven gas pump pumps working gas to a high-pressure container, from which the working gas can be quickly distributed either to the driving or driven unit or to both. Alternatively, the working pressure in the driving or driven unit can be quickly reduced by allowing working gas to return to the crankcase. In this way, the two integrated Stirling units can be quickly controlled and regulated without the efficiency of the units deteriorating.

In an integrated machine of the above type with a driving Stirling motor and a driven Stirling heat pump or cooling machine, one or more electric generators can also be connected to the crank mechanism, whereby the modulation of the average pressures in the driving and driven units can be determined so that a desired part of the generated mechanical energy is used to generate electricity while the rest is used by the heat pump or cooling machine. You can thus control the power levels in the various parts of the integrated machine in the desired way without loss of efficiency.

As mentioned, it is an advantage of the invention that in fully encapsulated energy converters operating according to Stirling, Ericsson or similar thermodynamic cycles, in order to reduce the weight of the energy converter, the wall thickness in the walls can be reduced to the spaces where there is low gas pressure. When the energy converter is switched off, working gas is first pumped from the low-pressure tank to the high-pressure tank so that the equalized gas pressure in the rest of the energy converter does not exceed the nominal working pressure in, for example, the crankcase and other low-pressure spaces.

When starting the energy converter, working gas is supplied to the cylinder, so that a suitable starting pressure is achieved.

The art known in the art and preferred embodiments of the invention are described in more detail below with reference to the accompanying drawings.

Fig. 1 schematically shows a known energy converter with medium pressure control. Fig. 2 schematically shows a single-cylinder Stirling engine with medium pressure control according to the invention.

Fig. 3 schematically shows a four-cylinder double-acting Stirling engine with medium pressure control according to the invention.

Fig. 4 schematically shows a double-acting four-cylinder Stirling engine, which is connected both to a double-acting four-cylinder heat pump, which also operates according to the Stirling cycle, and to integrated electricity generators, whereby both the Stirling engine and the heat pump are medium pressure regulated according to the invention.

The common known power control with a so-called short-circuit valve is shown in Fig. 1. In the cylinder 101 of a single-cylinder Stirling engine, the displacement piston 102 moves the working gas from the hot upper part of the cylinder past the heater 103, in which heat is supplied to the engine from a external energy source, such as a combustion chamber. In the regenerator 104, the supplied heat accumulates, so that it can be utilized at the right moment in the thermodynamic cycle. The cooler 105 removes heat, which is not converted to pressure energy and mechanical energy, by means of the working piston 106, which on its upper part is affected by the varying gas pressure and on its lower part is affected by the pressure in the buffer 107, whose pressure is determined by a non-return valve 108. In the case shown, a pressure prevails in the buffer that is close to the maximum pressure of the bicycle.

In order to increase the engine power at a given engine speed, working gas is supplied from the high-pressure tank 109 by opening a valve 110, so that the average pressure of the engine rises rapidly and thus the engine power also increases rapidly.

To reduce the power at a given engine speed, a valve III is opened, and a gas pump 112 pumps at a rate determined by its capacity working gas back to the high pressure vessel 109. However, this process is slow, about 10-30 seconds at best, and unsatisfactory. in many uses. Therefore, there is a so-called short-circuit valve 113, which quickly equalizes the pressure differences 467 ß37. 10 15 20 25 30 35 6 over the work piston and thus quickly lowers the engine power.

During the time that the short-circuit valve 113 is open, a quantity of fuel and energy must be supplied to the engine corresponding to the higher output power. Only when the gas pump has pumped back a sufficient amount of working gas to the high-pressure tank 109 can the amount of fuel and energy supplied be reduced. When using the engine with many rapid power reductions and thus frequent use of the short-circuit valve 113, the engine's fuel consumption will be unfavorably high.

Fig. 2 shows a single-cylinder Stirling engine 201 with a combustion chamber 202 and an air preheater 203. The heat generated during combustion is supplied to the engine in a heater 203. Heat is stored in a regenerator 205, and heat which is not converted to pressure energy or mechanical energy is dissipated in a cooler 206. A displacement piston 207 moves the working gas from a hot part of the engine to a cold and vice versa, a pressure variation occurring on the underside of the working piston 208. In a buffer space 209 there is a mean gas pressure with only small variations, since the buffer volume is significantly greater than the engine displacement. The pressure difference across the working piston drives a mechanism 210 in the crankcase 211, in which a substantially lower gas pressure prevails than in the buffer 209. The crank mechanism 210 drives two counter-rotating electric generators 212, which are hermetically enclosed in the crankcase. Only one power cable, which delivers the beneficial electrical power, is connected to the environment.

The crank mechanism also drives a gas pump 213, which pumps working gas from the crankcase to a high pressure cylinder 214.

By means of a valve 215, working gas can be quickly supplied to the engine cylinder, so that the engine power increases rapidly. In the same way, a valve 216 can be opened, so that working gas is quickly removed from the engine cylinder, whereby the engine power is rapidly reduced. In this way, the engine power can be changed quickly in the desired way while maintaining the efficiency and thus without increasing the fuel consumption. Fig. 3 shows the corresponding function of a four-cylinder double-acting Stirling engine 301, which has a combustion chamber 302, which is common to all four cylinders, heating pipes 303, which are arranged in a circle around the combustion zone, regenerators 304, radiators 305 and pistons 306, one in each cylinder. The cylinders are arranged in a row and connected to the heat exchangers according to the known double-acting Stirling principle. The movement of the pistons is transmitted to rotation via the yoke 307 by means of two counter-rotating crankshafts 308, which are enclosed in the crankcase 309. The crankshafts 308 are mutually synchronized by means of gears 310. In addition, each crankshaft is connected to a rotating electric generator 311 integrated in the crankcase.

The power control of the engine is performed in case of need for increased power by supplying working gas to the connecting line 312 in the engine between the radiator 305 and the cold space under the piston 306 by opening a valve 313, so that high pressure working gas flows from a high pressure bottle 314. Gas is continuously pumped from the engine crankcase 309 to the high pressure cylinder 314 by means of four gas pumps 315, one for each cylinder, the pumps being built into the crankcase and driven directly by the piston rods 316. At reduced power demand, working gas is drained from the engine via a valve 317 to the crankcase, in which 315 a significantly lower pressure is present than the average gas pressure in the engine. In this way, the engine power can be quickly increased and decreased by means of the valves 313 and 317, which are connected to all four cylinders in the engine, so that these are regulated in the same way. the crankcase 309 may alternatively be hermetically sealed with integrated electric generators, be connected by magnetic couplings on the crankshafts to externally driven devices or be provided with sealed shaft bushings arranged in the crankcase wall.

In Fig. 4, the invention is demonstrated by means of a double-acting, four-cylinder Stirling engine 401, which via piston rods 402 and a crank mechanism 403 drives a double-acting, four-cylinder heat pump 404, which operates according to the Stirling cycle. The crankshafts 405 are simultaneously connected to a rotating electric generator 406, which are integrated in the crankcase. The heat pump has a heat-absorbing heat exchanger 407, a heat-emitting heat exchanger 408 and a regenerator 409.

Heat exchanging medium circulates in the heat exchanger 407 through an inlet 410 and an outlet 411. Similarly, the heat exchangers 408 have an inlet 412 and an outlet 413 for a heat exchanging medium. With the help of the high-pressure cylinder 414, the Stirling engine with its four cylinders can be pressurized via the valve 415, while the Stirling heat pump with also four cylinders can be pressurized via the valve 416. In the crankcase 417 there is significantly lower pressure than in the two Stirling cycles, thanks to four gas pumps 418 b, c, d, one for each cylinder, pumps working gas to the high pressure tank. The power of the Stirling engine and the Stirling heat pump can be increased individually in this way by supplying working gas. The power of both energy converters is reduced in an analogous manner by draining working gas from the cycles to the crankcase via the valve 419 for the engine and the valve 420 for the heat pump. The electric generators connected to the crankshafts can be made to supply more or less electric current depending on how the effects of the motor and the heat pump are regulated.

The heat pump in Fig. 4 can alternatively function as a cooling machine, where the cooling medium flows through the heat exchanger 407 via the inlets and outlets 410 and 411.

The examples shown in Figures 2-4 constitute only some of the possibilities for energy converters which operate according to Stirling, Ericsson or similar thermodynamic cycles and which can be power-regulated by modulated average pressure control according to the invention. It is also possible to use two or more pressure levels in the low pressure part, for example by letting the crankcase operate at a low pressure level and the electric generator housing or housings at another low pressure level, provided that several sets of gas pumps and valves are used. Likewise, several high pressure levels can be provided, for example a level in the interior of the displacement piston, which is connected to the gas pump through a tubular piston rod, and another level in an external high pressure bottle.

Claims (4)

1. 467 837 10 15 20 25 30 35 1o_ PATENT REQUIREMENTS 1. Energy converters, which operate according to Stirling, Ericsson or similar thermodynamic cycles and which are power regulated by regulating the average pressure of the working gas, which regulation is achieved by means of at least one filled with working gas and to the pressure vessel's cylinder (s) connected to the energy converter cylinder (214: 314; 414), in which the gas pressure substantially exceeds the mean pressure and which thus enables an increase thereof, at least one gas pump connected to the outlet side of the pressure vessel (213: 315; 418a, b, c, d), which at its inlet side creates a negative pressure which enables a reduction of the working gas pressure, and valves (215, 216; 313, 317; 415, 416, 419, 420) for controlling both the pressure increase and the decrease, k - n - drawn by at least one low-pressure container housed in the energy converter and filled with working gas, in which the working gas pressure is significantly below the average pressure and which is connected partly to the inlet side of the gas pump, partly via the valve (s) for controlling the decrease in mean pressure with the cylinder (s) of the energy converter, the total volume of the low pressure vessel (s) being significantly larger than the stroke volume of the energy converter. Energy converter according to claim 1, characterized in that the energy converter's crankcase (211: 309; 417), which is sealed both against the energy converter's cylinder (s) and against the environment, constitutes a low pressure container. 3. An energy converter as claimed in Claim 1 or 2, characterized in that generator or gearbox housings included in the energy converter or connected to the energy converter, which are sealed to the surroundings, serve as low pressure vessels. 4. An energy converter as claimed in any one of claims 1-3, characterized by several low pressure vessels with mutually different pressures.