An internal combustion engine with steam expansion stroke

ES 2 311 628 T3

DESCRIPTION

Internal combustion engine with motive stroke based on steam expansion.

Field of the invention

The present invention is related to a method for controlling internal combustion engines, whereby the explosion strokes that are mainly based on expanding combustion gases can be alternated with the explosion strokes that are mainly based on water vapor. in expansion, in order to transform into useful work the heat that is generated in the combustion in the cylinder, and in the exhaust gases.

The invention is also applicable to internal combustion engines regardless of the type of combustion cycle. The Otto, Diesel, HCCI and free piston types are examples by which the invention is useful. However, the engines have to be provided with controllable valves and equipment for the injection of water and / or steam in order to allow their implementation.

The invention requires a control system, for example, which is provided as a part of the control system that is used to control controllable valves and fuel injection, etc. Background of the invention

During recent years, internal combustion engines, for example for vehicles, have been designed towards improved operational economy, and with a reduced effect on the environment, by means of the introduction of digital control systems for optimization in different operational situations. These are, for example, the case of fuel injection, ignition, variable compression and controllable valves. In terms of methods of transforming heat lost through cylinder cooling and exhaust gases into useful work, there have been no notable improvements.

Different variants of water injection have been tested in internal combustion engines. On the one hand, the intention has been to decrease the combustion temperature, in order to reduce the generation of nitrogen oxides, and on the other hand, the intention has been to reduce cooling losses in order to achieve a high degree of work performed. Furthermore, attempts have been made to inject steam at high pressure in connection with combustion. The high pressure steam has been generated by the evaporation of water by the hot exhaust gas media. Attempts have shown that the generation of nitrogen oxides decreases with the use of water / steam. In addition to that, improved performance has been tested. A problem that has restricted the aforementioned attempts, during the injection of water / steam, has been that a large amount of energy is consumed, as the injection takes place in relation to the end of the compression stroke and / or during the combustion, where the cylinder pressure is high. Another problem with restricted effect is the presence of a substantial amount of water, with a significant cooling effect during evaporation, which takes place during combustion, resulting in an undesirable increase in unburned hydrocarbons. The positive effects are not outweighed by the aforementioned drawbacks.

Document GB-A-2077853 discloses an internal combustion engine, where at the end of the exhaust stroke water is injected into the combustion chamber thereof, in order to generate a subsequent steam expansion stroke. The water will have a cooling effect on the cylinder walls, but when the cylinder wall is cool enough, performance will not be optimal, and the additional injection of water will not result in subsequent steam expansion strokes with a possibly efficient performance.

GB-2-028918 discloses an internal combustion engine, in which at the end of the normal exhaust stroke steam is injected into the combustion chamber, in order to generate a subsequent expansion steam stroke. The introduction of steam is positive for motor performance, but under certain conditions it will not be sufficient to achieve the required cylinder wall cooling, resulting in the need for external cylinder wall cooling.

The present invention eliminates the aforementioned problems, and the heat that is normally lost through the cooling of the cylinder and through the exhaust gases, is transformed into useful work, to a remarkable degree.

Object of the invention

The object of the present invention is to avoid the aforementioned problems, to a remarkable degree, and to transform the heat that is lost, in current engines, by means of the cooling of the cylinder and the exhaust gases into useful work.

Summary of the invention

The object of the invention is achieved by means of the initially defined method, characterized in that water and / or steam is supplied to a combustion chamber, in relation to the end of the exhaust stroke, where some of the exhaust strokes steam expansion are selected to primarily include a supply of water to the interior of the combustion chamber, and wherein the remaining steam expansion strokes are selected to comprise primarily a supply of steam in the combustion chamber, and wherein the engine comprises controllable valves, the control of which is based on an electronic control system, which is based on a computer program, and wherein the valves to the combustion chamber are closed as a response to the control system supplying a signal indicating that water / steam has to be supplied to the combustion chamber.

Power strokes are mainly based on expanding water vapor, being characterized in that the water and / or water vapor are supplied to the combustion chamber in relation to the end of the exhaust stroke, and when the piston reaches its top dead center.

Additional features of the invention are set out in the following description and in the patent claims.

Controllable valves refer to valves to the combustion chamber of the engine cylinder, wherein said valves are capable of opening and closing, for example, by means of a pressurized fluid, based on signals preferably coming from a system of electronic control, which is based on a computer program.

ES 2 311 628 T3

In this case, the motive stroke refers to the case in which the energy of an expanding mass of gas is transformed into mechanical work. According to the invention, the gas mass consists mainly of combustion gases or it is mainly constituted by water vapor.

The escape or evacuation stroke refers to the moment, for example, when a piston after the motive stroke, during its movement from bottom dead center to top dead center, forces the mass of gas to expand during the stroke drive to exit through the outlet valves.

The reason that controllable valves are a necessary requirement is because power strokes that are primarily based on expanding combustion gases have to alternate with power strokes that are primarily based on expanding water vapor. Powertrain strokes based on expanding combustion gases will now and later be referred to as combustion strokes, and powertrains, based on expanding water vapor, will now and later be referred to as expanding steam strokes. In current piston combustion engines, which are exemplified in the present invention, the intake valves open and the exhaust valves close relative to the end of the exhaust or exhaust stroke. When the control system transmits a signal ordering the supply of water and / or steam to the combustion chamber for the execution of a steam expansion stroke, the inlet valves for the regular air supply will not open, but they will be kept closed instead, after the end of the escape or evacuation run. Consequently, when the water and / or steam is supplied, the exhaust or outlet valves as well as the intake valves will be closed, and the pressure in the cylinder will be low. When water is supplied, an attempt will be made to evaporate it by the heat that is present by means of the piston and the additional hot surfaces of the combustion chamber. During evaporation, hot surfaces will cool, while simultaneously generating steam pressure relative to the start of a steam expansion stroke. When supplying water vapor, it will have been generated by an evaporation of the water by means of the heat present in the exhaust gases. During delivery, the steam will be pressurized. After the water supply as well as the water vapor supply, the water vapor will expand and do useful work as the piston travels to its bottom dead center. At piston bottom dead center, the outlet valves will open upon receiving a signal from the control system, and the water vapor evacuation or escape stroke will begin. When the control system transmits a signal commanding a combustion stroke to run, the inlet valves will be controlled to open as normal at the end of the evacuation or exhaust stroke.

In this case, the steam expansion stroke will refer to a motive stroke in a two-stroke or two-stroke cycle without any combustion, where the water and steam are supplied relative to the top dead center of the piston and with the end of an evacuation or escape race. The supply is carried out by opening the injection valves, suitable for this purpose, for the simultaneous injection in general with or after the closing of the exhaust or outlet valves. At this stage, the cylinder pressure is relatively low, which is a notable advantage compared to the attempts that have been discussed earlier in the introductory part of the description. The water is supplied, so that through evaporation it can cool the surfaces that are heated by the combustion gases and that delimit the combustion chamber, and in order to simultaneously generate a high pressure water vapor . High pressure water vapor is also generated by the evaporation of water, by means of heat from the exhaust gases, which would otherwise be released into the atmosphere. Steam or water can be supplied on separate occasions, as described above, but also during the same power stroke. This means that only water can be supplied before and / or during the motive stroke or that steam can be supplied before and / or during the motive stroke, or both water and steam can be supplied before and / or during the motor race. Through the expanding water vapor, the indicated work will be generated as the piston travels toward its bottom dead center. By alternating the steam expansion strokes and the combustion strokes, a notable improvement in efficiency can be obtained. An engine can be totally cooled by the means of the steam expansion strokes, based on the injection of water into the combustion chamber, alternating with the combustion strokes to a suitable degree. The control system decides up to what level the steam expansion strokes based on the water injection have to be executed.

The part of the losses in an Otto engine that are due to cylinder cooling is approximately 30%, and an approximately equal part is lost through the exhaust gases. For diesel engines, the losses are lower, but still so high that the invention would lead to markedly improved efficiency. Likewise, the other types of internal combustion engines have heat losses of a corresponding degree.

Consequently, the cylinders of an engine can be insulated externally, in order to obtain a greater need for internal cooling by means of injecting water into the combustion chamber, as described herein. The more efficient the insulation, the more heat will be accessible for the evaporation of the water on the surfaces that delimit the combustion chamber. However, the possibility of achieving the maximum effect outside the engine is somewhat limited by this method. However, the use also of a cooling system of the traditional type, in combination with the invention, will result in notable advantages in terms of efficiency.

The exhaust gas system of an engine can advantageously be isolated to the outside, in order to obtain an increased capacity for the production of pressurized steam. The more efficient the insulation, the more heat from the exhaust gas will be accessible for evaporation of the water. By implementing the invention for automobiles, it will be a great advantage if the water in the exhaust gases can be recycled. Therefore, there will be large amounts of water that you have

ES 2 311 628 T3 have to evaporate in a heat exchanger in the exhaust gas system. This water will be contaminated, for example, by soot and other particles. The water, which defines a truly effective particle collector, is filtered before being used to generate steam or to be injected into the combustion chamber. After evaporation of the water, the exhaust gases are remarkably clean, and can advantageously be recycled to a suitable degree, called EGR.

As mentioned, water injection in connection with combustion is well known. In the present invention, the pressurized water and / or steam are supplied without any connection to the combustion. Consequently, combustion does not take place in large amounts of supplied water, such as in the attempts described, which is a notable advantage in efforts to avoid unburned hydrocarbons. In a multi-cylinder engine, the expanding combustion gas-based power stroke can take place in one cylinder while, simultaneously, the expanding steam-based power stroke can take place in another cylinder.

During the injection of water, it is desirable that the water begins to evaporate as soon as possible, in order to obtain the greatest possible vapor pressure at the beginning of the motive stroke. In order to reduce the time to start the evaporation, the temperature of the water can already be adapted when supplying the water, so that the evaporation starts immediately without requiring substantial additional heating of the water. During evaporation, the pressure in the cylinder increases due to the generation of steam, and the temperature required for continuous evaporation also increases. Evaporation takes place as heat is absorbed from the surfaces surrounding the combustion chamber. This heat accumulates in the material that defines the mentioned surfaces, during the preceding combustion cycles. At a certain level of pressure, the accumulated heat will have been transformed into water vapor up to a certain level, which if it were additional water, evaporation would stop. The quantity of water supplied must be adapted in such a way that sufficient cooling is achieved without any liquid accumulating in the motor.

The water vapor, generated by the heat of the exhaust gas, can have a high relative pressure and a high temperature. For example, the pressure and temperature levels can be 100 to 150 bar and 300 to 350 degrees Celsius. At these levels, the contribution to the useful work of the engine becomes remarkably high. During operation, the control system, among other things, monitors the need for useful engine work, and the need for cooling and accessible amounts of steam and high pressure water. The control system ensures that the combustion strokes alternate with the necessary steam expansion strokes, which are based on the injection of water into the combustion chambers, in order to obtain sufficient cooling of the pistons and cylinders. In addition to this, the control system ensures that steam expansion strokes that are based on pressurized water vapor obtained by means of exhaust gas heat are used at the appropriate times.

The device according to the invention comprises one or more sensors to measure the temperature of the cylinder, and based on this information from these sensors, the control system will decide when to execute the steam expansion stroke based on the water supply. to the combustion chamber, and what will be the amount of water that has to be supplied, and executing the request for water injection, by means of control signals. By means of the sensors to detect the pressure of the pressurized water vapor, the control system determines the instant and the amount in which the pressurized water vapor will be supplied to the combustion chamber, and requesting the injection of water vapor by the means of a control signal. Advantageously, the pressurized steam is supplied when its pressure has reached a level such that the useful work carried out during the expansion stroke of the steam is generally the same as during all the additional motive strokes, such that for example the driver of the vehicle does not recognize any variation in engine operation. The control system will optimize the alternation between the combustion strokes and the described steam expansion strokes.

The steam expansion stroke can also be executed after a mixture of the two methods mentioned above. This is not a departure from the invention. Furthermore, it is not a departure from the invention to allow the water to evaporate on the surfaces that surround the combustion chamber externally, or to do this in combination with the method described above. Description of the drawings

Hereinafter a preferred embodiment of the invention will be described, with reference to the drawing, in which:

Figure 1 is a schematic cross section of part of a combustion engine according to the invention.

Description of a realization

Figure 1 is a schematic image by way of example, of a device according to the invention, showing a cylinder 1 with a piston 16. The device comprises an inlet valve 2 and an outlet valve 3, which are constituted by controllable valves, where both valves are closed in an instant after an evacuation or escape stroke that has just ended. The piston 16 will have reached its top dead center. The water will have been supplied to the combustion chamber 15 by the means of the injection valve 10, in order to cool the surfaces surrounding the combustion chamber 15, an increase in evaporation and pressure taking place before a cycle of expansion or escape of steam. Circuit 4 is used to activate valves 2 and 3. Control unit 5 is operatively connected to circuit 4, for signal control of the circuit, and of valves 2 and 3 that are connected to the circuit. The member 6, for example, of the accelerator pedal, is operatively connected to the control unit 5, provided on a graduated arc 9 which is mounted on the motor shaft 8, and operatively connected to the control unit 5, repeatedly provides information to the control unit 5 about the rotational speed of the engine, and about the position of the piston 16 in the cylinder 1. The control unit 5 decides when the controllable valves 2 and

ES 2 311 628 T3 have to be opened and closed. The pressurized fluid circuit 11, operatively connected to the control unit 5, is used in order to activate means, defined by an injection valve 10, for the supply of water or steam to the combustion chamber 15 The return member 14 is used to return the water vapor, for injection by the means of the injection valve 10. In a steam generator connected with the exhaust gas system and with the pressure gauges 13 and operatively connected with the control unit 5, there is an evaporation of the water which, by means of the return member 14, upon producing a signal from from the control unit 5 to the circuit 11, which in turn activates the injection valve 10, being supplied to the combustion chamber 15. The temperature indicator 12, which is operatively connected to the control unit 5, provides the control unit 5 with information about the temperature of the current cylinder. The control unit 5 uses this information on the temperature of the cylinder in order to determine the moment in which the circuit 4 will order the closing of the valves 2 and 3, and the moment in which the circuit 11 is commanded to activate the valve. injection 10 for injecting water into the combustion chamber 15. All the water and all the water vapor used will be mixed with the exhaust gases, and supplied to the exhaust gas system. In the heat exchanger 17, operatively connected to the control unit 5, in the downstream zone of the steam generator in the exhaust gas system, the amount of water that is required will be recycled by means of condensation, it is that is, cooling the exhaust gases by air. This water, which is the condensation, is purified in a particle filter 21, which is positioned in the heat exchanger 17, before being used. On the one hand, this treatment is relevant for the water used for cooling the surfaces that surround the combustion chamber internally, and on the other hand for the water that has to be transformed into water vapor by means of the heat of the exhaust gas. The water to be injected into the combustion chamber is transported by means of the return member 18 to the circuit 11. From the heat exchanger 17, the water is transported to the steam generator, which is provided with pressure gauges 13. The inlet valve 10 can be subdivided into two independent valves, one for water and the other for steam. Water. On an Otto engine, the injection valve can also be attached to the spark plugs and / or the fuel injection valve. On a diesel engine, it can be attached to the fuel injection valve. By means of the concentrating member 19, operatively connected to the control unit 5, the exhaust gases are concentrated, in order to be supplied to the engine in a suitable quantity, by the means of the return member 20. This is commonly referred to as the EGR system. The connection between the concentrating member 9 and the return member 20, and the operational connection with the control unit 5 are not shown in the drawing.

It will be noted that the plurality of variants of the embodiment of the device, and the method according to the invention that has been described above, will be obvious to the person skilled in the art, without departing from the scope of the invention, such as the method set forth. it is defined in the appended claims, supported by the description and by the accompanying drawings.

It is also emphasized that the device according to the invention, in a suitable but not necessary form, comprises all the components that have been indicated in the description of the preferred embodiment.