DE10330819A1 - Motor vehicle compression ignition internal combustion engine combustion control procedure uses light intensities from carbon, aldehyde and OH emissions to adjust parameters for homogeneous combustion - Google Patents

Abstract

A compression ignition engine (3) combustion control (10) procedure measures (5) the fuel air mixture burning using emitted light intensities from carbon and in the aldehyde (8, 9) and OH (7) bands to adjust (11) the mixture injection (4) time, pressure and distribution or charge parameters to produce homogeneous combustion.

Description

The The invention relates to a method for operating an internal combustion engine according to the preamble of claim 1.

It is well known that the amount and proportions of the emissions released during the combustion of an air-fuel mixture, for example soot or NO _x components in the exhaust gas, depend on the combustion process in the combustion chamber. In modern engines, therefore, various concepts of charge formation are pursued (for example, layer charge) in order to generate an ignition-willing charge in the combustion chamber, which burns as completely as possible at low exhaust emissions.

It is known to achieve as complete as possible combustion at low emissions through the use of a homogeneous fuel-air mixture. For this purpose, fuel is injected directly into the combustion chamber at a (suitable) point in time or finely atomized or vaporized fuel is supplied to the combustion chamber in the form of a homogeneous fuel-air mixture. The homogeneous charge is then ignited by compression ignition, the combustion being homogeneous at a low temperature level. Zones rich mixtures do not occur in the homogeneous charge. Combustion produces only very low soot and NO _x emissions. The control of the homogeneous combustion turns out to be difficult, since the start of combustion can be selectively controlled neither on the start of injection, as in the conventional diesel engine process, nor on the ignition, as in Otto engine method.

There it is like the diesel engine process to a compression ignition process the combustion is essentially dependent on the compression pressure, the compression temperature and the mixture composition influenced. Relevant control parameters for an auto-ignition process therefore the amount of charge, the part of recycled or remaining in the cylinder Exhaust gas and the injection quantity and their distribution and the compression ratio.

at the homogeneous combustion gains the state of charge, in particular the temperatures of supplied Fresh air, recirculated exhaust gas and also of fuel importance. Through the long period between Injection and start of combustion (ignition delay) Compared to the diesel engine process are the mixture formation processes, the Pre-reactions and also the ignition strongly from the temperature, Depending on the pressure and the charge composition, which in turn depends on the entire combustion effect.

in the Contrary to the known diffusion-controlled and thus heterogeneous burning diesel engine process is the homogeneous combustion by a simultaneous inflammation the charge in the entire combustion chamber. The burning takes place evenly throughout the combustion chamber without training a flame front. Narrow flame zones with high peak temperatures, as they are produced during diesel engine combustion in the homogeneous combustion by the space ignition of the premixed fuel-air mixture avoided. The energy release is typically in a very short time interval, as the combustion is ideally everywhere in the combustion chamber at the same time.

The setting of a homogeneous combustion in the combustion chamber is advantageous in two respects with regard to the pollutants produced: On the one hand, the homogeneous charge avoids the formation of mixture zones with lambda <0.7, which lead to soot formation during combustion. On the other hand, a uniform temperature profile avoids high peak temperatures and thus greatly reduces NO _x emissions.

Around ensure homogeneous combustion through auto-ignition To control, the course of combustion in the combustion chamber must be observed and be judged. This is especially true under the conditions changing engine load and speed in near real time required.

Generally It is already known, by means of an optical sensor during the Combustion emitted light in the combustion chamber of an internal combustion engine record and selected Spectral ranges of this light to control the combustion too to use.

Proposed, for example, in the DE 101 45 649 A1 to evaluate the combustion process in diesel internal combustion engines in particular with regard to the soot conversion by evaluating a band of OH radiation at 310 nm and a section of the soot radiation intensity at 660 nm.

Furthermore, it is already known from the DE 196 32 607 A1 a measuring device for determining the stoichiometric ratio of hydrocarbons. The intensity of the CH molecule fragments formed at combustion is measured at 431.5 nm and the resulting C-atom-containing molecular fragments at 516 nm, and from this ratio of CH and C ₂ radiation to the stoichiometric ratio closed during combustion. The device furthermore provides for a correction of the intensities by means of a third measured value, which evaluates the intensity of the background radiation, for example caused by thermal radiation. The stoichiometric ratio in the combustion chamber can be adjusted by changing the fuel and / or air supply from the measurement results in connection with a control device.

Previously known from the US 4,444,169 the assessment of the combustion conditions in the combustion chamber of an internal combustion engine on the evaluation of the combustion light at 431.5 nm and 306.4 nm. According to the evaluation of the radiation of the CH or OH band of this wavelength, the air-fuel ratio supplied to the engine is controlled.

adversely in the known method is that with the optical sensors only certain operating conditions the engine in otto- or conventional diesel engine operation are detectable and thus the combustion in the combustion chamber only in the process-specific limits can be influenced.

Of the Invention is based on the object, a method for operating to provide an internal combustion engine, in which from the determined Combustion conditions in the combustion chamber in a self-ignition one homogeneous combustion in a low temperature range and at low emissions detected and controlled on this basis can be.

These Task is in generic method for operating an internal combustion engine according to the invention the characterizing features of claim 1 solved.

Thereby, that from the determined intensities of certain spectral ranges of the light emitted during the combustion of the charge a regulation the parameter of the mixture to be supplied to the cylinder space, the Residual gas content in the cylinder and a possibly adjustable compression ratio takes place, is achieved that a homogeneous combustion of supplied Setting fuel-air mixture in the combustion chamber. Up with this the basis of the evaluation of the emitted during combustion of the charge Light-oriented regulation of the internal engine combustion process is achieved that in the combustion chamber, a homogeneous combustion with a on the entire combustion chamber distributed reaction zone is present, which has a uniform temperature profile has and thus avoids high peak temperatures. At the same time in the thus set homogeneous combustion, the nitrogen oxide and soot formation reduced so that their exhaust emissions meet the required standards of considerably below today's emissions legislation.

One Another advantage of the solution according to the invention is that the to control the burning process required discrete intensities the recorded combustion light in time as well as in the intensity of a differentiated Behave. This gives the possibility of the presence or the intensity the individual radiation shares the character of the combustion in detail to capture and thus timely by regulating the parameters of the cylinder space to be supplied Mixture charge, the residual gas content in the cylinder and a possibly. adjustable compression ratio To be able to influence the combustion.

Further advantageous embodiments are described in the subclaims; they are explained in the description together with their effects.

Based of drawings, the invention will be described below by way of example described in more detail. In the corresponding Drawings show:

1 : A schematic representation of the course spectrum of the radiation occurring during combustion and

2 : A schematic representation of the solution according to the invention for the determination and evaluation of the combustion radiation and for controlling the combustion.

In the 2 is shown schematically the basic structure for the determination and evaluation of the combustion radiation and for controlling the combustion process according to the inventive method. On an internal combustion engine 3 is a known probe 5 arranged, with which in the combustion chamber of the internal combustion engine 3 Combustion radiation emitted when burning the fuel-air mixture is absorbed. The supply of the fuel-air mixture into the combustion chamber of the internal combustion engine 3 is known to be via a fuel injection 4 ,

According to the invention, the radiation intensity is determined from a suitable section of the course spectrum of the soot radiation, for example 695 to 705 nm. However, this section may also be from another spectral range of the festival body radiation of the soot can be selected in the range between 500 and 8000 nm. Furthermore, the intensities of the aldehyde bands are determined at 375 to 385 nm and at 425 to 435 nm and the OH radiation at 305 to 315 nm. With the help of these determined variables, a regulation of the engine operating parameters takes place in such a way that a homogeneous combustion of the supplied fuel-air mixture is established. The by means of measuring probe 5 absorbed combustion radiation is a soot detector via a light guide 6 , an OH radiation detector 7 and the aldehyde detectors operating at different wavelengths 8th and 9 for determining the intensity of the radiation of the respective wavelength range and an evaluation device 11 which determines whether a homogeneous combustion is present. The combustion radiation of the formaldehyde bands, which is characteristic of the homogeneous combustion, is present before the actual start of combustion and is thus already clearly detectable in front of the soot radiation and OH band radiation.

In the 1 the course of the intensities of the soot radiation of the OH band and the aldehyde bands at the respective wavelengths and for different mixture preparation conditions over degrees KW is shown. In the enlarged section, this early emission by the peaks is for the aldehyde bands 1 . 1a and 2 . 2a recognizable, which are characteristic of a homogeneous and partially homogeneous combustion of premixed fuel-air mixture.

By means of the soot detector 6 is checked in a first step, if at 695 to 705 nm wavelength soot radiation occurs or a predetermined threshold of soot radiation is exceeded. If this is the case, there is no completely homogeneous combustion, but there are still inhomogeneities or an excessively low lambda <0.7.

When through the soot detector 6 Soot radiation has been detected by the soot detector 6 a per se known engine control unit 10 a signal decoded according to the determined magnitude of the soot radiation is transmitted for changing and regulating the parameters of the mixture charge supplied to the cylinder space.

Unless the soot detector 6 No or only a very low soot radiation intensity is detected, in a further step by means of the OH radiation detector 7 the course of the OH radiation in the range between 305 and 315 nm considered and compared with the position of the Aldehydbandenstrahlung. The evaluation of the OH radiation and aldehyde band radiation is indicated since the absence of soot radiation alone is not an indication of homogeneous combustion. If the soot formation temperature or the lambda-dependent soot formation limit in the combustion chamber is not reached or not exceeded, no soot or soot radiation is produced, but OH radiation occurs both in homogeneous and in heterogeneous combustion and also in combustion with single-stage high-temperature ignition and can be used as an indicator of the start / end of the combustion.

to Distinction of combustion with single-stage high-temperature ignition from a homogeneous combustion, in turn, the timing used the radiation emissions. Is a simultaneous emission start detectable by OH and aldehyde bands (no deposited aldehyde band radiation), so it is a one-stage high-temperature flame with nitric oxide formation and not the desired multi-stage process the combustion. This latter runs initially on the oxidation of the long-chain CH chains to intermediates (alkyl peroxides) from, in turn upon reaching a critical concentration to formaldehydes disintegrate (Emission of aldehyde bands) and thus the desired low-emission low-temperature process control of Identify homogeneous combustion.

In the case of combustion with single-stage high-temperature ignition, this is also done via the engine control unit 10 a regulation of combustion.

In order to be able to detect a homogeneous combustion, it is therefore necessary to monitor the aldehyde band emission by means of the aldehyde detector 8th at a wavelength between 375 and 385 nm as well as through the aldehyde detector 9 between 425 and 435 nm and to compare with the beginning of OH radiation. Only if there is a markedly reduced aldehyde band emission in comparison to the OH emission start, can a homogenous combustion of a fuel-air mixture due to autoignition be assumed.

From the evaluation device 11 is in the presence of a homogeneous combustion the engine control unit 10 also transmitted a signal. Through the engine control unit 10 However, in this case, no changes are made to the present parameters, since an optimal setting has already been made.

• – die Einspritzung des Kraftstoffes bzgl. Zeitpunkt, Druck, Mengenaufteilung
• – und/oder die Ladungszusammensetzung
• – und/oder die Ladungstemperatur bzw. Ladedruck
• – und/oder das Verdichtungsverhältnis
• - und/oder die Ladungsbewegung wie Drall und Tumble

regelbar verändert.In the case of detected inhomogeneous combustion or combustion with single-stage high-temperature ignition, the parameters of the mixture charge supplied to the cylinder space by the engine control unit are known per se 10 changed. As controllable factors are either

• The injection of the fuel with respect to time, Pressure, quantity distribution
• And / or the charge composition
• - and / or the charge temperature or boost pressure
• - and / or the compression ratio
• - and / or the charge movement such as spin and tumble

controllably changed.

1

peak

1a

peak

2

peak

2a

peak

3

Internal combustion engine

4

Fuel injection

5

probe

6

Rußdetektor

7

OH radiation detector

8th

Aldehyddetektor

9

Aldehyddetektor

10

Engine control unit

11

evaluation

Claims (9)

Method for operating an internal combustion engine, in which a charge consisting of a fuel-air mixture is ignited by compression ignition and the combustion is evaluated by means of the light emitted in the combustion chamber during combustion and the combustion is influenced by control parameters, characterized in that the signal intensities the soot radiation in the range of 500 to 8000 nm, the aldehyde bands at 375 to 385 nm and at 425 to 435 nm and the OH radiation at 305 to 315 nm, a regulation of Motoreinstellparameter carried out such that a homogeneous combustion of the supplied fuel-air Mixes. Method according to claim 1, characterized in that that the soot radiation preferably detected in the range of 695 to 705 nm. Method according to Claims 1 and 2, characterized that for a homogeneous combustion characteristic combustion radiation the Aldehydbanden is detected before the start of combustion, the beginning of the burning determined by the course of the signal intensity of the OH radiation and a soot formation in the permitted Range limits is determined. Method according to Claims 1 to 3, characterized that at a detected homogeneous combustion, the parameters the supplied to the cylinder chamber Mixture charge unchanged to be kept. Method according to Claims 1 to 3, characterized that at a detected inhomogeneous combustion or combustion with one-stage high-temperature ignition by changing the Parameter of the mixture charge supplied to the cylinder space, such as change the injection of the fuel with respect to time, pressure, quantity distribution, and / or the change the charge composition, the charge pressure, the charge temperature, the charge movement such as spin or tumble, the compression ratio and the like, a homogeneous combustion is set. Method according to Claims 1 to 5, characterized that an inhomogeneous and soot-forming Combustion is detected when in the range of 500 to 8000 nm, For example, at 695 to 705 nm, exceeded a threshold of soot radiation becomes. Method according to Claims 1 to 5, characterized that combustion with single-stage high-temperature ignition is present when the OH radiation at 305 to 315 nm no temporal upstream significant signal intensity in the range of aldehyde wavelengths is present. Method according to claim 7, characterized in that that the beginning and end of the course of OH radiation in approximation to Start and end of the main combustion corresponds. Method according to Claims 1 to 8, characterized that the radiation profile of the combustion process is recorded via a probe and over fiber optics fed to an evaluation unit and using the data obtained via an engine control unit, the setting parameters the supplied to the cylinder chamber Mixture charge can be adjusted adjustable.