DE102006044698B4 - Combustion process for a spark-ignition internal combustion engine powered by direct fuel injection and supercharging - Google Patents

Abstract

A combustion method for a spark-ignition reciprocating internal combustion engine operated by direct fuel injection and supercharging, in which a charge movement about a tumble axis (13) extending substantially perpendicular to a cylinder axis is effected, characterized in that substantially over the entire load range of the reciprocating internal combustion engine substantially in the longitudinal direction of the tumble axis (13 ) is injected.

Description

The present invention relates to a combustion method for a spark-ignition internal combustion engine operated by direct fuel injection and supercharging according to the preamble of claim 1.

For Otto engine combustion, the intake manifold injection was used in the series technology area until not so long ago, in which the fuel was injected into an inlet channel of the reciprocating internal combustion engine in the area in front of a gas exchange component. In order to reduce the specific fuel consumption and thus the CO ₂ emissions, the direct fuel injection has already been used in the field of spark-ignition internal combustion engine. In order to further reduce the specific consumption and the pollutant emissions of the reciprocating internal combustion engine operated in this way, it has already become known to operate the reciprocating internal combustion engine in the so-called lean operation with excess air. Lean operation can be based either on a homogeneous air-fuel mixture or on an inhomogeneous mixture with charge stratification.

Based on DE 102 61 185 A1 is known to operate on the principle of direct-injection gasoline engine with spark ignition internal combustion engine, in which to avoid the problem of wetting the piston crown with fuel, the piston crown has cavities, in which the injected fuel jets can enter.

Based on WO 2006/024083 A1 For example, an internal combustion engine having an inlet control member in the form of a roller valve or rotary valve has become known, which is intended to achieve tumble flow.

Based on EP 1 161 620 B1 An internal combustion engine with direct fuel injection has become known, in which the fuel is injected via an injection nozzle into the combustion chamber in the direction of the piston, specifically in the form of a hollow cone-shaped fuel jet which widens in the direction of the piston.

Based on DE 198 01 607 A1 an internal combustion engine has become known, which can be operated in stratified lean operation, for this purpose during the compression stroke fuel is injected into a spaced second to the injection valve combustion chamber in the piston crown and the fuel is then transported during the compression stroke in the direction of the centrally located spark plug. A tumble-like fresh air flow is meanwhile held in a first combustion bowl in the piston head.

Based on JP 2000-161067 A has become known an internal combustion engine having two inlet openings with a support channel disposed therebetween, with this configuration, a tumble flow is to be formed and a concentrated air-fuel mixture is to accumulate near a spark plug.

Based on EP 1 179 662 B1 For example, a gasoline engine with direct injection has become known, in which fuel is injected via an injection element as mist in the form of a fan parallel to the central axis of a piston towards a recess of the piston.

A combustion process with charge stratification for a direct-injection, spark-ignited internal combustion engine is, for example, based on the Applicant WO 03/048540 A1 known. This known combustion method works with charge stratification and an inlet channel serving as a filling channel, which generates a tube-like swirl core directed in the direction of the cylinder axis. This swirl serves to generate an ignitable mixture cloud at late injection end in the stratified charge mode and to include wall-supported fuel in the combustion, so that the emission of hydrocarbon and soot is reduced.

Quite generally, the swirl in the case of in particular air-guided combustion processes serves to transport an ignitable fuel-air mixture to an ignition device in the form of a spark plug, for example, in order to achieve burn-through even in the case of a zone-dependent inhomogeneous fuel-air mixture.

In addition to these combustion methods used in reciprocating internal combustion engines without turbocharging, however, a combustion method for a spark-ignition reciprocating internal combustion engine operated by direct fuel injection and charging has already become known, in which an intense charge movement is effected by an axis of a roller flow which is substantially perpendicular to an axis of a working cylinder of the internal combustion engine Tumble is performed. This combustion process is characterized by a homogeneous operation with a stoichiometric air-fuel ratio and thus a working without stratified charge combustion process. In such, operated by direct fuel injection and supercharging known spark-ignition reciprocating internal combustion engine, the roller flow is required to intensive charge movement for the homogenization of the fuel air mixture and a To achieve combustion acceleration via macro- and micro-turbulence in order to realize a fast burn-through of the mixture and to avoid areas without flame front.

In other words, in the supercharged reciprocating internal combustion engine, the tumble flow is required even at an air ratio or λ of 1 to ensure effective burnout of the fuel air mixture.

If now the spark-ignition reciprocating internal combustion engine operated with turbocharging and direct fuel injection is operated with additional air to reduce fuel consumption and reduce pollutant emissions, the problem arises of providing a combustion process for this purpose, which provides an ignitable fuel-air mixture in local and temporal terms at the flame origin. The present invention is based on the object of providing such a combustion process.

The combustion method provided according to the invention has the features specified in claim 1. Advantageous embodiments thereof are described in the further claims.

In the supercharged, spark-ignited reciprocating internal combustion engine or internal combustion engine, the tumble is used to intensify the charge motion to obtain a sufficiently mixed fuel-air mixture so that after the spark ignition the flame front fully propagates through the thus formed mixture cloud, thus areas of unburned fuel avoidance, which would lead to increased consumption and high pollutant emissions in the exhaust gas. The roller-shaped movement of the tumble, which rotates largely perpendicular to a cylinder axis of the cylinder of the internal combustion engine, thus leads to a homogenization of the mixture cloud and therefore counteracts an intended layer charge. In order to operate the charged spark-ignition internal combustion engine with the tumble in the stratified charge to realize lean combustion with excess air, according to the present invention, a combustion method is provided for operated by direct fuel injection and supercharged spark-ignition reciprocating internal combustion engine, in which a charge movement about a substantially perpendicular to a Cylinder axis extending tumble axis is brought about, in which the fuel is largely injected over the entire load range of the reciprocating internal combustion engine substantially in the longitudinal direction of the tumble axis.

Thus, the injected fuel is injected into the region of the quiet center of the tumbles, so that adjusts a locally narrow limited mixture cloud in this area and thus considered on the stroke volume of the cylinder of the internal combustion engine, an area with a relatively high concentration of fuel, which in Axial longitudinal direction of the cylinder axis considered areas connect with lower concentrations of fuel and thus higher air ratio, so that so that the goal can be achieved to operate the supercharged and direct fuel injection and spark-ignited internal combustion engine in stratified charge mode.

If, for example, a subset of the fuel intended for injection at the respective piston stroke is already injected during the intake stroke of the piston in the longitudinal direction of the tumble axis, this generates an area with higher fuel concentration, which then occurs when the piston in the cylinder moves in the direction of bottom dead center , viewed in the direction of the cylinder axis areas with lower fuel concentration or areas with almost exclusively air follow. Due to the increasing in-cylinder space and the kinetic energy of the high-pressure fuel due to the movement of the piston during the intake stroke, the mixture cloud may spread in the direction of the tumble axis due to the relatively quiet space there, thus extending substantially perpendicular to the cylinder axis to form a continuous tubular channel in which there are then finely divided fuel particles to form in this way a burn-through channel, when the fuel-air mixture has been ignited by spark ignition.

Due to the lying in the distance to the piston surface Tumbleachse the tubular mixture cloud is at a distance from the piston surface, so that Wandanlagerung on the piston surface can also be largely avoided and an attachment of the tubular mixture cloud on the cylinder wall of the cylinder in that the injection of fuel substantially in the longitudinal direction of the tumble axis in time and with respect to the amount of injected fuel so that fogging of the cold cylinder wall is largely avoided.

According to a development of the invention, it is provided that the fuel is injected on both sides of a longitudinal center of the tumble axis largely in the longitudinal direction of the tumble axis halves such that the piston conveys an ignitable fuel mixture in the direction of at least one arranged in a cylinder head of the reciprocating internal combustion engine ignition device in the compression stroke. This will fuel in each case In the longitudinal direction of the resulting halves of the tumble axis injected on both sides of the longitudinal center of the tumble axis and it forms the previously described tubular mixture cloud, which is then transported by the piston in the compression stroke as an ignitable fuel mixture in the direction of a cylinder head of the reciprocating internal combustion engine to which an ignition device in the shape of, for example, a spark plug is provided.

Thus, the further the piston moves in the compression stroke in the direction of the upper end of the cylinder combustion chamber, the shorter the distance between the tubular mixture cloud moving from the piston and the ignition device will be, until the tubular mixture cloud is ignited by the ignition device.

According to a development of the invention, it is provided that the fuel is injected by means of a Ringlochdüse as a fuel jet substantially in the longitudinal direction of the tumble axis and / or the Tumbleachsenhälften. Thus, if, for example, the ring-hole nozzle with two hole-shaped openings is arranged in the region of the upper end of the cylinder combustion chamber, the fuel is injected as a fuel jet in the direction of the tumble axis or the tumble-axis halves. For example, the amount of fuel injected through the annular orifice nozzle may be sufficient to operate the reciprocating internal combustion engine from the load at idle to within the range of the low part load.

According to a development of the invention, it is provided that for the load control of the reciprocating internal combustion engine additional fuel is injected in particular as a cone sheath jet. The fuel injection in the direction of the tumble axis or the Tumbleachsenhälften is thus superimposed according to the embodiment of the invention, a fuel injection for load control, which can be carried out, for example, as a Kegelmantelstrahleinspritzung. Thus, if the internal combustion engine is loaded according to its load spectrum with a medium partial load, this can be achieved by injecting a predetermined amount of fuel, for example as a conical jacket jet in addition to the injection of fuel in the direction of the tumble-axis halves.

Quite generally, it is provided according to a development of the invention that a fuel injection during the suction stroke and / or the compression stroke of the piston volume variable takes place at least once. Thus, according to the invention both in the direction of the tumble axis and / or Tumbleachsenhälften a fuel injection also repeatedly and with different fuel quantity, which can be superimposed on a fuel injection for load control, which can also be variable in volume and multiple.

The additional fuel injection provided according to the invention can take place, for example, from a specific work of the reciprocating internal combustion engine of about 0.4 kJ / dm ³ . It means in other words that, depending on the work obtained with the reciprocating internal combustion engine, the additional fuel injection takes place, wherein the additional fuel can be injected as a conical jacket jet into the cylinder chamber. It is also provided according to the invention to inject the additional fuel with a mold into the combustion chamber, which at least substantially does not lead to a contact with the injected in the direction of the tumble axis and / or Tumbleachsenhälften fuel, so that the first-mentioned fuel so injected is that the fuel particles do not come into physical contact with the largely injected in the direction of the tumble and / or Tumbleachsenhälften fuel particles. Merely by way of example, a cone-jet jet injection can be mentioned here in which the lateral components which go in the direction of the tumble axis and / or the tumble-axis halves remain cut-out via a corresponding nozzle shape.

As already mentioned above, according to one embodiment of the method according to the invention, the fuel is injected substantially in the longitudinal direction of the tumble-axis halves lying on both sides of the longitudinal center of the tumble axis. It forms in this way a tubular in the quiet center of the tumbles lying mixture cloud from the longitudinal center of the Tumbleachse seen from expansion tendencies towards the two-sided cylinder jacket wall has. This mixture cloud into which fuel can also be injected during the compression stroke of the piston, ie shortly before the ignition TDC in the direction of the tumble axis and / or the Tumbleachsenhälften is then transported by the piston during the compression stroke in the direction of the upper boundary of the cylinder chamber. After ignition of this tubular mixture cloud, a burn-through channel is formed, in which the flame front continues through the entire mixture cloud. In order to achieve a further improvement of the Durchbrennverhaltens the tubular Durchbrennkanals, it is provided according to a development of the invention that the fuel air mixture is ignited by means of two ignition devices, each adjacent to a cylinder jacket wall of each cylinder of the reciprocating internal combustion engine are arranged such that a connecting distance between the Ignition devices in one of the cylinder axis and Tumbleachse spanned plane is located and after ignition of the fuel air mixture, a burn-through channel is generated by the radially outer regions of the fuel-air mixture in the direction of the radially inner region of the fuel-air mixture.

So it can be provided, for example, two spark plugs per upper end of each cylinder of the internal combustion engine, which form a link between them. This connecting path now does not run obliquely or obliquely to the tumble axis of the tumbles, but coincides in a plan view of the cylinder from above with the tumble axis, so that the tubular mixture cloud is conveyed from the piston going up to the two ignition devices. Ignite both ignition devices simultaneously, the fuel air mixture burns starting from the ignition towards the radially inner center of the tumble axis, so that sets a blow-through, which ensures low-pollution combustion of the mixture cloud of the stratified charge reciprocating internal combustion engine. Since it is provided according to the invention that the fuel injection takes place in the direction of the tumble axis and / or Tumbleachsenhälften over largely the entire load range of reciprocating internal combustion engine, this burn-through channel also takes the fuel, which is additionally injected for load control of the reciprocating internal combustion engine.

According to a development of the invention, it is provided that the fuel injected by means of the fuel injection substantially in the longitudinal direction of the tumble axis and / or the tumble-axis halves is dimensioned such that the air ratio in the region of a fuel-air mixture formed thereby is in the range between 1 and 1.3. In other words, this means that the fuel mass flow injected only by the fuel injection in the direction of the tumble axis and / or the tumble axis halves ensures that the air ratio λ integrally in the range of 1 and 1.3 moves, so that by the fuel injection in the direction of Tumbleachse or the Tumbleachsenhälften a fuel mixture is formed, which may already have excess air.

In order to ensure safe combustion, it is provided according to a development of the invention that the fuel-air mixture generated by the fuel injection substantially in the longitudinal direction of the tumble axis and / or the tumble-axis halves has an inner region having an air ratio λ ≤ 1.0 and after ignition forms a burn-through. The fuel injection in the direction of the tumble axis or the tumble-axis halves therefore takes place in such a way that a rich mixture can form in the inner region of the tubular mixture cloud which permits reliable ignition and forms a burn-through channel which also covers the regions in the cylinder with λ ≥ 1.0 inflamed.

In order to meet the different load conditions of the reciprocating internal combustion engine, it is provided according to a development of the invention that the fuel mass flow injected substantially in the longitudinal direction of the tumble axis and / or the tumble axis halves is changed depending on the load state of the reciprocating internal combustion engine. This ensures that this fuel injection in the direction of the tumble axis or the tumble axis halves also operation of the internal combustion engine in the low part load range is possible without additional fuel must be injected in substantially the Zylinderachsrichtung.

The invention will be explained in more detail with reference to the drawing. This shows in:

1 a schematic representation of a cylinder of a reciprocating internal combustion engine in the intake stroke for explaining the method according to the invention;

2 a representation similar 1 rotated 90 degrees;

3 a representation of the working cylinder after 1 at the beginning of the combustion cycle; and

4 a representation similar 3 rotated 90 degrees.

1 The drawing shows a schematic representation of a working cylinder 1 a not shown reciprocating internal combustion engine with a piston also shown only schematically 2 , The piston 2 moves, as can be seen by the arrow P, directed in the downward direction, ie towards the bottom dead center. The working cylinder 1 forms above the piston 2 a combustion chamber 3 out. The combustion chamber 3 gets down from the piston 2 completed and up from a boundary 4 in the form of, for example, a dome. The dome may be formed in a cylinder head, not shown, of the reciprocating internal combustion engine and has approximately centrally disposed a nozzle 5 , about the fuel in the combustion chamber 3 can be introduced.

In the illustrated embodiment, the nozzle is 5 around a nozzle, which can deliver both jet-shaped fuel, as well as cone-shaped. In addition, the dome points 4 also two ignition devices in the form of two spark plugs 6 on. As it is readily apparent, the spark plugs are 6 at the illustrated Embodiment of the working cylinder 1 each adjacent to the cylinder surface 7 arranged. In the reciprocating internal combustion engine, not shown, it is a gasoline engine operated with a supercharging, wherein the fuel through the nozzle 5 directly into the combustion chamber 3 is introduced.

About a in 2 The drawing schematically illustrated gas exchange component in the form of an inlet valve 8th is opened via an inlet channel after opening 9 Intended for combustion air into the combustion chamber 3 introduced, there a roll-shaped flow or a tumble 10 formed. The tumble 10 leads into the combustion chamber 3 to a charge movement, which is a largely perpendicular to a cylinder axis of the working cylinder 1 running movement, as indicated by the arrows 11 is apparent. The charge movement is therefore not a swirl extending around the cylinder vertical axis, but a roller-shaped charge movement about a cylinder axis of the working cylinder which is largely perpendicular to the vertical axis 1 around. The tumble 10 owns in its largely central area 12 a quiet zone with a tumble axis 13 , in the 1 the drawing is shown schematically. As can be readily seen, the tumble axis runs 13 while largely perpendicular to the vertical axis of the working cylinder 1 ,

About the nozzle 5 In this case, according to the combustion method according to the invention fuel is in the quiet central area 12 injected substantially in the longitudinal direction of the tumble axis 13 as this is based on the spray pattern 14 the case is that shows a slightly expanding due to the cylinder internal pressure fuel jet.

This fuel injection substantially in the longitudinal direction of the tumble axis 13 leads to a fuel air mixture or a mixture cloud 15 , which are largely in the central quiet area 12 around the tumble axis 13 forms around and takes a tubular shape. Moves the piston 2 now directed in the direction of arrow P down, so the mixture cloud moves 15 along with the tumble 10 directed downward, then in the compression stroke of the piston 2 towards the spark plugs 6 to be promoted.

In addition to the fuel injection in the direction of the tumble axis 13 or in the direction of tumble-axis halves, which are from a longitudinal center of the tumble axis 13 are formed in the direction of both sides, shows 1 and 2 also a fuel injection through the nozzle 5 in the combustion chamber 3 in the form of a cone-sheath jet 16 , This fuel injection in addition to the fuel injection in the direction of the Tumbleachse or the Tumbleachsenhälften serves the load control of the reciprocating internal combustion engine, not shown, and is the fuel injection in the direction of the tumble axis 13 or the Tumbleachsenhälften superimposed if the load control requires it.

Is the piston located 2 now in the compression stroke in the direction of top dead center, so is the tubular mixture cloud 15 towards the two spark plugs 6 transported and formed after the ignition by the two spark plugs 6 a burn through channel 17 in which the flame front from the place of ignition, ie the spark ignition by the two spark plugs 6 from radially outward in the direction radially inward propagates and thus for safe combustion of the combustion chamber 3 introduced fuel provides. In the center of the mixture cloud 15 can thereby be the air ratio λ ≤ 1, the fuel injected only by the fuel injection in the direction of the tumble axis or the Tumbleachsenhälften leads to a fuel-air ratio of about 1 to 1.3, so that even this alone a combustion is realized with excess air.

Due to the fuel concentration in the quiet central area 12 of the tumbles 11 but here is a safe burning Durchbrennkanal created, for the ignition of the entire in the combustion chamber 3 of registered fuel. The arrangement of spark plugs 6 is chosen such that an imaginary link between the two spark plugs 6 lying in the plane, that of the cylinder axis and the Tumbleachse 13 is formed, so that the tubular mixture cloud 15 through the piston going upwards 2 to the two spark plugs 6 transported. The ignition of the mixture cloud 15 through the two spark plugs 6 then leads to the already mentioned above initial ignition of the blow-through channel 17 , as shown by the rotated by 90 degrees in 4 the drawing is visible and thus to a safe and low-emission combustion of the entire in the combustion chamber 3 registered fuel.

The spark plugs 6 can be arranged in the longitudinal direction of the engine, not shown, and due to the two independent fuel injections, on the one hand largely in the longitudinal direction of the tumble axis 13 or the Tumbleachsenhälften and on the other hand, the Kegelmantelstrahleinspritzung 16 for a safe burning of the fuel. The injection of the fuel can also take place multiple times, this applies both to the fuel injection in the direction of the tumble axis and / or the Tumbleachsenhälften and the fuel injection through the central cone sheath jet. For the idling mode and the lower or low partial load operation of the internal combustion engine, the fuel is injected only in the direction of the tumble axis or the tumble-axis halves, which ensures a safe burn-through channel in the combustion engine operated with excess air. From about a central part load up to and including full load, both the hole jet injection, which is the spray pattern 14 leads, as well as the cone-jet injection 16 , which serves for the combustion of increasing mixture quantities and thus for load regulation. The two fuel injections, the spray pattern 14 and the cone sheath jet 16 lead, are independently controllable. The combustion method according to the invention leads to a stable combustion process through the burn-through channel 17 , which is independent of the load and the speed of the internal combustion engine. The burn-through channel has a reproducible unique position in the combustion chamber of the internal combustion engine and generates a flame front, which continues along the tumble axis from outside to inside and leads to a safe and low-emission combustion of the entire fuel in the combustion chamber.

With regard to features of the invention which are not explained in greater detail above, reference is expressly made to the claims and the drawings, moreover.

LIST OF REFERENCE NUMBERS

1

working cylinder

2

piston

3

combustion chamber

4

Limitation, calotte

5

jet

6

spark

7

Cylinder surface

8th

intake valve

9

inlet channel

10

Tumble

11

arrow

12

Middle area

13

Tumbleachse

14

spray pattern

15

mixture cloud

16

Conical surface beam

17

Burnout channel

P

arrow

Claims (10)

Combustion method for a spark-ignition reciprocating internal combustion engine operated by direct fuel injection and charging, in which a charge movement about a tumble axis extending substantially perpendicular to a cylinder axis (FIG. 13 ) is brought about, characterized in that fuel substantially over the entire load range of the reciprocating internal combustion engine substantially in the longitudinal direction of the tumble axis ( 13 ) is injected. Combustion method according to claim 1, characterized in that the fuel is on both sides of a longitudinal center of the tumble axis ( 13 ) is injected largely in the longitudinal direction of the tumble-axis halves in such a way that the piston ( 2 ) in the compression stroke, an ignitable fuel-air mixture in the direction of at least one arranged in a cylinder head of the reciprocating internal combustion engine ignition device ( 6 ). Combustion method according to claim 1 or 2, characterized in that the fuel by means of a Ringlochdüse as a fuel jet substantially in the longitudinal direction of the tumble axis ( 13 ) and / or tumble axis halves is injected. Combustion method according to one of the preceding claims, characterized in that for the load control of the reciprocating internal combustion engine additional fuel in particular as a conical jacket jet ( 16 ) is injected. Combustion method according to one of the preceding claims, characterized in that a fuel injection during the suction stroke and / or the compression stroke of the piston ( 2 ) Variable amount at least once. Combustion method according to claim 4 or 5, characterized in that the additional fuel injection takes place from a specific work of the reciprocating internal combustion engine of about 0.4 kJ / dm ³ . Combustion method according to one of the preceding claims, characterized in that the fuel-air mixture by means of two ignition devices ( 6 ) is inflated, each adjacent to a cylinder jacket wall ( 7 ) of each cylinder of the reciprocating internal combustion engine are arranged such that a connection path between the ignition devices ( 6 ) in one of the cylinder axis and the tumble axis ( 13 ) spanned plane and after ignition of the fuel air mixture, a burn-through channel ( 17 ) is generated by the radially outer regions of the fuel-air mixture in the direction of the radially inner region of the fuel-air mixture. Combustion method according to one of the preceding claims, characterized in that the fuel injection by means of the fuel injection substantially in the longitudinal direction of the tumble ( 13 ) and / or Tumbleachsenhälften injected fuel mass flow is such that the air ratio in the range of a fuel-air mixture formed therewith in the range of 1 ≦ λ ≦ 1.3. Combustion method according to one of the preceding claims, characterized in that by means of the fuel injection substantially in the longitudinal direction of the tumble axis ( 13 ) and / or tumble-axis halves produced fuel mixture has an inner region with an air ratio λ ≤ 1.0 and after ignition has a burn-through channel ( 17 ) trains. Combustion method according to one of the preceding claims, characterized in that substantially in the longitudinal direction of the tumble axis ( 13 ) and / or Tumbleachsenhälften injected fuel mass flow in response to the load condition of the reciprocating internal combustion engine is changed.

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