DE102006011190A1 - Method for operating a reciprocating internal combustion engine - Google Patents

Abstract

A method for operating a reciprocating internal combustion engine (1) with a fuel injection by means of an injector (8) directly into a combustion chamber (2) of the reciprocating internal combustion engine (1), in which a piston (3) periodically, by a Verbrennungslufteinlaßakt in the combustion chamber (2) introduced, in the combustion chamber (2) with fuel (9) mixed combustion air ignites by compression and then expels exhaust gases in a Abgasauslasstrakt, characterized by the following process steps:
Introducing combustion air into the combustion chamber (2);
Compressing the introduced into the combustion chamber (2) combustion air with the piston (3);
Injecting fuel (9) into the combustion chamber (2) during compression until an ignitable fuel / combustion air mixture is present;
Starting combustion by autoignition of the fuel / combustion air mixture;
Further injecting fuel (9) into the combustion chamber (2) to maintain combustion;
Stopping the injection of fuel (9) into the combustion chamber (2) when the reciprocating internal combustion engine (1) provides a requested power;
Pushing exhaust gas into the exhaust gas outlet tract.
The combustion process according to the invention represents a low-NOx combustion process.

Description

The The invention relates to a method for operating a reciprocating internal combustion engine with the features of the preamble of claim 1.

at Be direct injection internal combustion engines with auto-ignition often homogeneous lean fuel / air mixture brought to autoignition, so that high efficiencies and improved exhaust emissions achieved become. In such so-called HCCI (Homogenious Charge Combustion Ignition), or PCCI (Premixed Charge Compression Ignition) internal combustion engines, also known as internal combustion engines with Raumzündverbrennung is usually at part load a lean base mixture of air, fuel and restrained Exhaust gas formed and ignited itself. At full load becomes common a stoichiometric Fuel / air mixture formed and externally ignited, because at high loads could through the auto-ignition steep pressure increases in the combustion chamber occur, which leads to an impairment of the company would. This means that an operation of the internal combustion engine is only in a small one Map area (load over the speed) possible.

One fundamental Problem with HCCI combustion process is reliable operation with the auto-ignition to ensure.

To expand the map range is therefore in the German patent application DE 103 50 797 A1 , from which this invention proceeds, proposed an operating method, which is characterized in that in the combustion chamber of the internal combustion engine, the operating point is operated with compression ignition or spark ignition. Exhaust gas is retained during a compression ignition mode, which is compressed during the charge exchange, wherein a first amount of fuel is injected by means of a first disposed in the combustion chamber injector in the retained exhaust gas. Subsequently, a second quantity of fuel is supplied to the combustion chamber by means of a second injector arranged in the intake manifold, so that a homogeneous fuel / air mixture is formed in the combustion chamber. Preferably, the second amount of fuel is injected during the intake phase within the intake manifold.

The proposed, additional Fuel injection leads while at the same time reducing the raw emissions of the internal combustion engine to a better homogenization of the formed fuel / air mixture, thus to use a larger map area, however, the nitrogen oxide (NOx) emissions of the internal combustion engine are very high high, since even in the proposed combustion high temperatures be reached, where a nitrogen oxide formation takes place.

task The present invention is to show a measure to a generic internal combustion engine in a big one To be able to use the map area, while reducing nitrogen oxide emissions.

These The object is achieved by the features in the characterizing part of the claim 1 solved.

by virtue of of the proposed method of operation combustion begins with a minimum amount of ignitable fuel / air mixture, being after auto-ignition the combustion of the in-cylinder air flow away from the injector becomes. At the same time, while the ongoing combustion injected more fuel into the combustion chamber, which reacts with freshly introduced to the injector combustion gas and the further combustion gets upright. Controlled by this, Continuous combustion, is the map range of the internal combustion engine enlarged and at the same time the combustion temperatures are kept low, allowing a NOx formation during combustion is avoided. Possible This is because the pressure increase in the combustion chamber after ignition with the operating method according to the invention can be controlled.

A another possibility to enlarge the map area and To reduce the nitrogen oxide emissions, according to claim 2 in that the combustion air is admixed exhaust gas, which also the combustion temperature lowers.

The Admixture of exhaust gas to the combustion air can according to claim 3 either in the combustion air intake tract (intake or gas exchange inlet duct in the cylinder head) and / or in the combustion chamber. While the first variant called external exhaust gas recirculation is, the second variant is the so-called internal Exhaust gas recirculation. The can be done, for example, that the exhaust by an additional Valve is introduced into the cylinder head in the combustion chamber, or for example also by a valve overlap between the gas exchange inlet and gas exchange outlet valves.

With the method step according to claim 4, a controlled, continuous combustion is achieved.

By the method step according to claim 5 is a good, but speed-dependent cylinder filling with Combustion air achieved.

The Speed dependency the cylinder filling is reduced by the method step according to claim 6. Thus, almost over the entire speed range of the engine always an optimal Charge of the combustion chamber ensured. By this measure become particularly high-performance and high-torque as well as economical Internal combustion engines achieved.

In Advantageously, according to claim 7 the charging of the combustion chamber by means of an exhaust gas turbocharger or a mechanical pump, such. As a compressor or Roots blower or a combination of both charging methods.

in the The following is the burning process according to the invention closer by four figures explained.

1 shows a section through a combustion chamber, wherein the piston is in a position 30 ° before ignition TDC;

2 shows the same section through the combustion chamber, with the piston is in a position 25 ° before ignition TDC.

3 shows the same section through the combustion chamber, with the piston is in a position 15 ° before ignition TDC.

4 shows the section through the same combustion chamber, wherein the piston is in a position 5 ° before ignition TDC.

In the 1 to 4 , the same reference numbers apply to the same components.

In the 1 to 4 is in each case a section through a schematically illustrated reciprocating internal combustion engine 1 shown. A combustion chamber 2 is enclosed by a piston 3 , which is movable in a cylinder 4 is arranged, and a cylinder head 5 on the side opposite the piston. In the cylinder head 5 are a gas exchange inlet valve 6 and a gas exchange outlet valve 7 arranged. Between the gas exchange inlet valve 6 and the gas exchange outlet valve 7 is a fuel injector 8th arranged with the fuel 9 in the combustion chamber 2 einbring-, or is injectable.

Under the combustion chamber 2 is understood in the present embodiment, the variable-stroke volume, which of the piston 3 , the cylinder 4 and the cylinder head 5 is included. In the inventive method for operating the reciprocating internal combustion engine 1 First, combustion air is introduced into the combustion chamber 2 then it is introduced into the combustion chamber 2 introduced combustion air with the piston 3 compressed and then fuel during compression 9 in the combustion chamber 2 introduced until an ignitable fuel combustion air mixture is present. With even greater compression, the fuel-combustion air mixture is ignited by autoignition, with more fuel 9 in the combustion chamber 2 , to maintain combustion, is injected. The injection into the combustion chamber 2 is stopped as soon as the reciprocating internal combustion engine 1 provides a requested performance, or a limit temperature of the exhaust gas is achieved. Subsequently, the exhaust gas from the piston 3 pushed out into the exhaust gas outlet tract.

In the 1 to 4 is in each case a piston position to a defined crankshaft position with the respective operating state of the reciprocating internal combustion engine 1 shown. In 1 is the piston 3 30 ° before ignition TDC (30 ° before the piston reaches its top dead center, in which an ignition, in this case, a self-ignition, takes place), with the injector 8th fuel 9 in the combustion chamber 3 is introduced.

In 2 is the piston 3 25 ° before ignition TDC and it can be seen how the fuel 9 self-ignited at 25 ° before ignition TDC and combustion 10 starts.

In 3 is the piston 3 15 ° before ignition TDC. Due to a charge movement 11 in the combustion chamber 2 the combustion moves 10 in the direction of the outlet valve 7 further, wherein by further injection of fuel 9 in the combustion chamber 2 with the injector 8th the burning 10 is maintained.

In 4 is the piston 3 5 ° before ignition TDC. Due to the charge movement 11 is the burning 10 at this crank angle already under the exhaust valve 7 , where continue to fuel 9 in the combustion chamber 2 is injected until a termination criterion (exhaust gas temperature, power, etc.) is met.

To the reciprocating internal combustion engine 1 To make even pollutant, an exhaust gas recirculation can be provided. The exhaust gas recirculation can be designed both as internal and external exhaust gas recirculation, ie the exhaust gas recirculation takes place in. Case of external exhaust gas recirculation via the intake tract or, in the case of internal exhaust gas recirculation, through targeted valve overlap of inlet and outlet gas exchange valve. A combination of both exhaust gas recirculations is possible.

To the nitrogen oxide emissions as low as It is possible to keep fuel from injecting 9 in the combustion chamber 2 stopped as soon as a defined exhaust gas temperature is exceeded (NOx formation takes place at temperatures> 2200 ° K). The method according to the invention is characterized above all by the fact that an already formed combustion 10 (Combustion volume) due to the charge movement 11 in the combustion chamber 2 from the injector 8th is moved away while simultaneously fresh gas to the injector 8th is moved to the combustion 10 to maintain.

The reciprocating internal combustion engine 1 can be designed as a suction internal combustion engine, ie the combustion air is of which in the cylinder 4 lowering piston 3 in the combustion chamber 2 sucked. In other embodiments, charging with fresh combustion air may also be provided. This can be done for example with an exhaust gas turbocharger or a mechanical pump, such as a compressor or a Roots blower.

Because it is his auto-ignition reciprocating internal combustion engine 1 For example, hydrocarbons can be used as fuel 9 be used. This may be diesel fuel, gasoline or alternative fuels such as hydrogen and bio-oils.

It should be noted that in the 1 to 4 shown injection and ignition timing with respect to the piston position are exemplary only. In particular, the injection time, or the injection duration can vary over wide ranges.

• – Auflösung des Zielkonfliktes Verbrauch vs. NO_x und damit Erfüllung zukünftiger Emissionsvorschriften ohne Verbrauchseinbußen;
• – Weltweit einsetzbares Mager-Brennverfahren;
• – Reduzierter Aufwand und Kosten für die Abgasnachbehandlung.

In contrast to the HCCI combustion process (homogeneous charge combustion ignition), the combustion process according to the invention is not a homogeneous combustion process but a lean, stratified combustion process. This means that in the combustion chamber 2 an unequal distribution of fuel 9 is present. Through the continuous injection of fuel 9 in the combustion chamber 2 Slow combustion is achieved without high temperatures. Thus, the nitrogen oxide emissions are almost zero. Through the controlled addition of fuel 9 ensures that the NOx formation temperatures (> 2200 K) are not exceeded even at higher loads of the internal combustion engine and the pressure increase in the combustion chamber 2 remains controllable. The method according to the invention affords the following advantages:

• - Resolution of the conflict of objectives consumption vs. NO _x and thus fulfillment of future emission regulations without loss of consumption;
• - Worldwide usable lean combustion process;
• - Reduced effort and costs for the exhaust aftertreatment.

1

Reciprocating internal combustion engine

2

combustion chamber

3

piston

4

cylinder

5

cylinder head

6

Gas exchange inlet valve

7

Gaswechselauslassventil

8th

injector

9

fuel

10

combustion

11

charge movement

Claims (7)

Method for operating a reciprocating internal combustion engine ( 1 ) with a fuel injection by means of an injector ( 8th ) directly into a combustion chamber ( 2 ) of the reciprocating internal combustion engine ( 1 ), in which a piston ( 3 ) periodically, through a combustion air intake tract into the combustion chamber ( 2 ), in the combustion chamber ( 2 ) with fuel ( 9 ) mixed combustion air ignites by compression and then expels exhaust gases in a Abgasauslasstrakt, characterized by the following process steps: - introducing combustion air into the combustion chamber ( 2 ); - Compressing into the combustion chamber ( 2 ) introduced combustion air with the piston ( 3 ); - injection of fuel ( 9 ) in the combustion chamber ( 2 ) during compression until an ignitable fuel / combustion air mixture is present; - Starting combustion by auto-ignition of the fuel / combustion air mixture; - further injection of fuel ( 9 ) in the combustion chamber ( 2 ) to maintain combustion; - stopping the injection of fuel ( 9 ) in the combustion chamber ( 2 ), when the reciprocating internal combustion engine ( 1 ) performs a requested service; - pushing exhaust gas into the exhaust gas outlet tract. Method according to claim 1, characterized that the combustion air is mixed with exhaust gas. Method according to claim 2, characterized in that the admixture of exhaust gas in the combustion air inlet tract and / or in the combustion chamber ( 2 ) he follows. Method according to one of the claims 1 to 3, characterized in that burnt fuel / combustion air mixture during the compression by a charge movement in the combustion chamber ( 2 ) from the injector ( 8th ) away and fresh burns air to the injector ( 8th ) moves. Method according to one of the claims 1 to 4, characterized in that the combustion air from the piston ( 3 ) in the combustion chamber ( 2 ) is sucked. Method according to one of the claims 1 to 4, characterized in that the combustion air into the combustion chamber ( 2 ) is pumped. Method according to claim 6, characterized in that combustion air from an exhaust gas turbocharger or a mechanical pump into the combustion chamber ( 2 ) is pumped.