DE19645913C2 - Combustion chamber with mutual swirls for internal combustion engines - Google Patents

Description

The invention relates to combustion chambers for diesel engines with direct and indi right fuel injection (prechamber engines), for gasoline engines with external Ge mixed formation, for petrol engines with direct fuel injection, for petrol engines with a prechamber in the cylinder head (stratified charge engines) and for hybrid engines.

The combustion chambers of diesel and gasoline engines correspond to the respective ones Mixture or combustion processes constructed and have thereby Known procedural disadvantages.

In diesel engines with direct fuel injection, the trough combustion chamber is in the Piston plate arranged so that a gas movement in the radial direction, the so-called called radial gas movement, is generated in the area of top dead center (without T.). The mixture formation and combustion requires a pronounced charge swirl (Air swirl), which is achieved by a corresponding construction of the intake system becomes. This reduces the degree of delivery (degree of filling) due to flow losses, resulting in reduced engine performance; the design of the intake systems is complex.

The forced charge swirl only moves in one direction. An even one This means that the fuel cannot be distributed to the air. There are areas che with different fuel concentration, which leads to increased pollutants mission (HC, CO and PM) especially lead to soot and particle emissions.

With gasoline engines, the most common is a trough combustion chamber in the piston crown and / or is arranged in the cylinder head for use. With the help of the combustion chamber design, in the form of squeeze areas, becomes a radial gas in the area of the top part movement achieved. However, this is not sufficient for a sufficiently large one Achieve burn rate. This prolongs the burn duration far into the expansion clock, which leads to a reduction of the we efficiency leads. This disadvantage is particularly pronounced in the partial load range low speeds and in lean operation (over-stoichiometric mixture, λ <1) of the gasoline engine.

In more recent developments, so-called shaft suction pipes and / or through the design of the intake system, similar to that of a diesel engine, is a charge swirl generated and thus increases the rate of combustion. Both measures are very complex and at the same time reduce the degree of delivery, especially in the upper turn number range and thus the performance of the gasoline engine.

Combustion chambers have also been patented to increase the combustion speed (e.g. US 5 065 715 and DE 27 32 005), which are the same for intensifying the turbulence Generate radial and tangential gas movements in the area of the upper part at an early stage. A he The main disadvantage of these combustion chambers is the overlapping of both gas movements,  whereby an orderly supply of air to fuel or fuel to Air is not possible. In contrast to these patents, patent DE 41 27 617 C1 the combustion chamber designed so that only very weak radial and tangential gas movements occur. In contrast, the separation of the individual force Material jets strictly observed in the combustion chamber.

The invention has for its object to the fuel jets in the combustion chamber separate, so that an orderly supply of air to the individual fuel jet len is possible. In comparison to the listed patents and the known ones Combustion chambers (e.g. trough-shaped, trough-shaped and hemispherical combustion chambers) are prevented the new combustion chamber especially the radial gas movement. In the combustion chamber only a charge movement in the tangential direction, the so-called Tangential gas movement. This is in the form of mutual swirls created and reached the highest intensity in the area of top dead center. The collision of the mutual swirl intensifies the mixture formation between fuel and air while accelerating combustion what to leads to increased efficiency and reduced pollutant emissions. A charge swirl created by an elaborate construction of the intake system is no longer required.

The object is achieved by the features listed in claims 1 to 6 and solved by the combustion chamber construction shown and described below.

Combustion chamber construction

In the piston base Kb and / or in the cylinder head Zk are two or more open radial channels K (Figure 1.1 and 1.2), verschiedenster geometric shape, up to a certain distance from the piston head circumference extended from the center of the piston crown and uniformly about the axis A of the cylinder Zy are distributed, manufactured. In Figure 1.3 and 1.4, two different geometric figures tric forms are shown as an example. The combustion chamber is particularly suitable for three-, four- and five-valve engines, since the injection nozzle Ed ( Fig. 1), the spark plug Zü ( Fig. 2), or the pre-chamber Vk ( Fig. 3) are arranged centrally in the combustion chamber is. The number i of the radial channels corresponds to the number of fuel jets from the fuel injector or the number of flame jets from the chamber. The fuel jets or the flame jets penetrate partially or altogether into the channels. The arrangement of the channels ensures an even fuel distribution in the combustion chamber.

Working gas movement

In the new combustion chamber, the charge swirl required for mixture formation and combustion is generated by squeezing the working gas into the radial channels during the compression stroke ( Fig. 1.2 and 2, 2). Two swirls D, ie a total of 2 × i working gas swirls, are generated in each channel. The swirls (a swirl pair) of a radial channel flow against each other ( Figure 1.2). In part, the two swirls penetrate the fuel jets in the case of direct fuel injection or the flame jets in the case of prechamber engines, and in part they surround them. This distributes the air evenly and orderly around the fuel jet. In gasoline engines with external mixture formation, this process additionally homogenizes the mixture and increases the turbulence.

The swirls are intensified in the area of the top dead center (without T.). The Winkelge speed ω _{D of} the mutual swirl can be several times greater than the Winkelge speed ω _{K of} the crankshaft. It is directly proportional to the engine speed and inversely proportional to the distance h between the piston crown and cylinder head in the area of top dead center. It is also inversely proportional to the number and volume of the channels. Taking all parameters into account, there is a maximum value for the angular velocity ω _D.

In the expansion cycle, the direction of the swirl movement is reversed ( Figure 2.3). The swirls now consist of flame gas, hot gas, hot air, fuel droplets and / or fuel vapor. Two swirls from two different radial channels collide and penetrate each other. The mutual penetration of the hot gas flows increases the combustion speed and thus shortens the combustion time.

The new combustion chamber enables the mixture formation and combustion to be controlled by varying the ratio between the total volume of the Radial channels and the compression volume of the combustion chamber as well as through the geometric shape of the radial channels.

Application in diesel engines with direct fuel injection

The new combustion chamber is used for mixture formation and combustion Working gas movement (swirl movement), as described above, by the Squeezing surfaces between the radial channels in the piston crown or cylinder head aims. This eliminates the complex construction of the intake system; the delivery degree increases.

By the forced swirl movement and the collision of two against each other side swirls in the compression stroke, the air becomes orderly and even Fuel jet led. At the same time there is an air movement around and through the force jet achieved. As a result, the mixture formation improves. The air gap tongue increases at full load.

By reversing the swirl movement in the expansion cycle, the mixture is formed tion process additionally improved and the combustion rate in particular which increased in the last part of the combustion.

The advantages are as follows:

• - Smaller displacement with the same performance
• - lower fuel consumption
• - reduced soot and particle emissions
• - reduced NOx emission at full load

Use with gasoline engines

If the spark plug is located in the center of the combustion chamber in gasoline engines, then the following model of combustion is to be assumed:

The flame core is created around the spark plug and is very stable because the mixing movement is low at this point. The flame spreads evenly in the radial direction ( Figures 2.1 and 2.2). The mutual mixture flows (swirls) meet in the radial channels and collide, which intensifies the mixture formation and increases the turbulence. As a result of increasing turbulence, the flame speed in the radial channels increases. In the expansion cycle, the swirls reverse and the flame fronts spread out above the piston crown. Then the mutual flame fronts collide and penetrate each other ( Figure 2.3). The combustion now takes place at the depth of the turbulent flame fronts, which increases the speed of combustion and, as a result, shortens the duration of combustion.

The advantages are as follows:

• - Increased efficiency, especially in the partial load range and at low Speeds due to the shortened burning time
• - Reduced tendency to knock due to the increased charge turbulence
• - higher speeds because the flame speed is proportional to the Speed increases
• - Reduced pollutant emissions (NOx, CO, HC) due to more stable ignition
• - Reduced pollutant emissions (NOx, CO, HC) by diluting the mixture due to increased charge turbulence
• - Improved control of mixture formation and combustion through Variation of the ratio between the total volume of Radial channels and the compression volume of the combustion chamber
• - simplified intake system

Use in gasoline engines with a prechamber

For petrol engines with a prechamber in the cylinder head (stratified charge engines), in the pre-chamber formed a substoichiometric ("fat") mixture and the Ver Burn started by spark ignition. The flame rays of the "fat" Gemi flows out of the pre-chamber openings and penetrate into the radial channels (The number i of the radial channels corresponds to the number of flame beams from the front chamber) and ignite the "lean" mixture in the channels or in the main burner room. Due to the forced swirl movement in the compression cycle, the "ma gere "mixture in the main combustion chamber evenly and ordered to the flame beam guided.  

In the expansion cycle, the flame fronts (flame currents) spread above of the piston crown as an inverted swirl at high speed and ever because two swirls from two different radial channels collide and penetrate each other. This increases the rate of combustion and the Shortened burn time. This enables an increased mixture dilution, which lead to a lower pollutant emission and an increased efficiency in Partial load range leads.

Claims (6)

1. combustion chamber with mutual swirls for internal combustion engines, characterized in that

• 1. two or more open radial channels are arranged in the piston crown / cylinder head and are evenly distributed on the circumference;
• 2. the radial channels meet at the center of the piston crown / cylinder head and are of various shapes in cross-section;
• 3. the areas between the radial channels, which are evenly distributed around the circumference, form squeeze areas and only produce a tangential gas movement in the form of mutual swirls;
• 4. The mutual swirls collide in the compression and expansion phase in the area of top dead center (without T.).

2. Combustion chamber according to claim 1, for diesel engines with direct fuel injection, characterized in that the number of radial channels the number of force corresponds to blasting into which some or all of the fuel is injected. 3. Combustion chamber according to claim 1 for gasoline engines with a central spark plug and external Mixture formation, characterized in that the number of radial channels is at least two. 4. Combustion chamber according to claim 1 for gasoline engines with a central spark plug and direct Fuel injection into the cylinder or into the combustion chamber, towards the beginning or End of the compression stroke, characterized in that the number of Radial channels is at least two. 5. Main combustion chamber according to claim 1 for gasoline and diesel engines with a central Antechamber in the cylinder head, characterized in that the number of radial channels channels corresponds to the number of prechamber openings. 6. Combustion chamber according to claim 1 for hybrid engines in which the fuel against Injected at the end of the compression stroke and the mixture is ignited externally, characterized in that the number of radial channels is at least two.