Procedure and device for determining the composition of a fuel mixture
10 claims: 5 independent, 5 dependent
- 1PATENTKRAV 1. Förfarande för bestämning av sammansättningen av en bränsleblandning av ett första bränsle och åtminstone ett andra bränsle för drift av en självtändande förbränningsmotor med åtminstone en sensor som bestämmer förbränningsprocessen i åtminstone en cylinder hos förbränningsmotorn, kännetecknat av, att det vid sensorn handlar om en sensor som redan är tillhandahållen för reglering av förbränningen i förbränningsmotorn på basis av en förbränningsrumssignal, varvid sensorns utgångssignal används för bestämning av förbränningsförloppet, att ett mått på förbränningsförloppets stabilitet bildas genom statistisk utvärdering över flera förbränningscykler av en storhet som karakteriserar ett förbränningsförlopp i åtminstone en cylinder hos förbränningsmotorn och att bestämningen av bränsleblandningens sammansättning sker från måttet på förbränningsförloppets stabilitet, att bestämningen av storheten som karakteriserar förbränningsförloppet sker från en bestämning av ett cylindertryck eller en bestämning av en stomljudsignal hos förbränningsmotorn eller ett varvtal hos förbränningsmotorn eller en jonström hos en sond i cylindern betraktade var och en för sig eller från åtminstone två av dessa mätförfaranden i kombination.
- 2Förfarande enligt krav 1, kännetecknat av att som mått på förbränningsförloppets stabilitet i cylindern används den över ett förutbestämt antal förbränningscykler bildade standardavvikelsen hos läget för en förbränningstyngdpunkt eller standardavvikelsen hos ett indikerat cylindermedeltryck eller standardavvikelsen hos en maximal tryckgradient i cylindern eller standardavvikelsen hos ett maximalt differentiellt energifrisättande eller standardavvikelsen hos ett maximalt integrerat energifrisättande eller förhållandet mellan standardavvikelsen och medelvärdet hos det indikerade cylindermedeltrycket eller en från 533 288 Π dessa storheter härledd parameter betraktade var och en för sig eller åtminstone två av dessa storheter i kombination.
- 3Förfarande enligt något av kraven 1 eller 2, kännetecknat av att bildandet av måttet på förbränningsförloppets stabilitet sker i förutbestämda driftspunkter hos förbränningsmotorn.
- 4Förfarande enligt krav 1 till 3, kännetecknat av att ett gränsvärde för måttet på förbränningsförloppets stabilitet förutbestäms och att driftparametrar hos förbränningsmotorn inställs så att måttet på förbränningsförloppets stabilitet inte överskrider gränsvärdet.
- 5Förfarande enligt krav 4, kännetecknat av att för iakttagande av gränsvärdet för måttet på förbränningsförloppets stabilitet ombesörjs en ökning av en restgasmängd i förbränningsmotorns cylindrar eller en tidigareförskjutning av en börvärde hos en reglering av läget för en förbränningstyngdpunkt eller ett införande av en förinsprutning av bränsle betraktade var och en för sig eller åtminstone två av detta åtgärder i kombination.
- 6Förfarande enligt krav 5, kännetecknat av att ökningen av restgasmängden i förbränningsmotorns cylindrar sker genom en tidigare stängning av den respektive avgasventilen under utdrivningstakten eller genom ett kortvarigt öppnande av den respektive avgasventilen under insugningstakten.
- 7Förfarande enligt något av de ovanstående kraven, kännetecknat av att bestämningen av sammansättningen av bränsleblandningen sker med hjälp av det nödvändiga korrekturingreppet i regleringen av förbränningsmotorn för iakttagande av gränsvärdet för måttet på förbränningsförloppets stabilitet. 533 288 IS
- 8Användning av förfarandet enligt något av de föregående kraven för bestämning av sammansättningen av en bensin/alkohol-bränsleblandning och/eller för reglering eller styrning av stabiliteten hos förbränningsförloppet hos en med bensin eller en bensin/alkohol- 5 bränsleblandning driven självtändande förbränningsmotor.
- 9Anordning för bestämning av sammansättningen av en bränsleblandning av ett första bränsle och åtminstone ett andra bränsle för drift av en självtändande förbränningsmotor med en variabel eller delvis variabel
- 1010 ventildrivning för variabel inställning av ventilöppningarna beroende på vevvinkeln och för variabel inställning av ventilernas öppningstvärsnitt, med en direktinsprutning för dosering av bränsleblandningen, med åtminstone en sensor för bestämning av förbränningsförloppet i åtminstone en cylinder hos förbränningsmotorn och med en reglerenhet 15 för reglering av förbränningsmotorn på basis av sensorns utgångssignal, kännetecknad av att som sensor används en sensor som redan är tillhandhållen för reglering av förbränningsmotorn, att en motorelektronik med en lagringsenhet är tillhandahållen, varvid 20 sensorns utgångssignal tillförs motorelektroniken som mått på förbränningsförloppet och lagras i lagringsenheten över ett förutbestämt antal förbränningscykler, att motorelektroniken är försedd med en utvärderingsanordning som är utformad på så sätt, att en statistisk utvärdering av en storhet som 25 karakteriserar förbränningsförloppet genomförs för bestämning av ett mått på förbränningens stabilitet, varvid bestämningen av storheten som karakteriserar förbränningsförloppet sker från en bestämning av ett cylindertryck eller en bestämning av en stomljudsignal hos förbränningsmotorn eller ett varvtal hos förbränningsmotorn eller en 30 jonström hos en sond i cylindern betraktade var och en för sig eller från åtminstone två av dessa mätförfaranden i kombination och 533 288 Η att anordningen vidare är utformad på så sätt, att bränsleblandningens sammansättning bestäms och en korrektur av förbränningsmotorns reglering genomförs från det bildade måttet på förbränningens stabilitet. 5 10. Självtändande förbränningsmotor enligt krav 9, kännetecknat av att för bestämning av förbränningens förlopp är åtminstone en cylindertrycksensor eller åtminstone en sensor för bestämning av förbränningsmotorns stomljudsignal eller åtminstone en varvtalssensor eller åtminstone en sensor för bestämning av jonströmmen i en cylinder 10 tillhandahållen. 533 288 1/1 Ο
Independent claims10
83 paragraphs in 9 sections, as filed
(12) Patent Specification do) SE 533 288 C2 <6 c>
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Sweden (21) Patent application number: 0950297-2 (45) Patent granted: 2010-08-10 (41) Application generally available: 2009-11-09 (22) Patent application submitted: 2009-05-04 (24) Maturity date: 2009- 05-04 (83) Deposit of microorganism: - (51) International class:
G01N 33/22 (2006.01)
F02D 19/08 (2006.01)
F02D 41/00 (2006.01)
F02D 41/14 (2006.01) (30) Priority information: 2008-05-08 DE 102008001668.3
<td>(73) Patent holders:</td><td>Robert Bosch GmbH, PO Box 30 02 20, DE-70442 Stuttgart DE</td>
<td>(72) Inventor:</td><td>Axel Loeffler, Backnang DE Wolfgang Fischer, Gerlingen DE Roland Karrelmeyer, Bietigheim-Bissingen DE Gerald Graf, Gaertringen DE Daniel Scherrer, Stuttgart DE</td>
<td>(74) Agents:</td><td>Albihns.Zacco AB, Box 5581, 114 85 Stockholm SE</td>
<td>(54) Name:</td><td>Method and apparatus for determining the composition of a fuel mixture</td>
<td>(56) Publications cited:</td><td>XP 025235878 · US 5050555 Al</td>
<td>(47) Summary:</td><td>The invention relates to a method and apparatus for determining the composition of a fuel mixture of a first fuel and a second fuel for a self-igniting internal combustion engine with a sensor which determines the combustion process in a cylinder of the internal combustion engine.</td>
In the process, a measure of the stability of the combustion process is formed from a quantity which characterizes a combustion process in a cylinder of the combustion engine, the determination of the composition of the fuel mixture being made from the measure of the stability of the combustion process.
The device includes a control unit for controlling the internal combustion engine on the basis of the output of the sensor, the output of the sensor being applied to a motor electronics as a measure of the combustion process and can be stored there over a predetermined number of combustion cycles, a statistical evaluation of the combustion pre-combustion engine can be stored. combustion stability, wherein the composition of the fuel mixture can be determined and a correction of the control of the combustion engine can be carried out from the measured measure of the stability of the combustion.
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533 288
SUMMARY
The invention relates to a method and apparatus for determining the composition of a fuel mixture of a first fuel and a second fuel for a self-igniting internal combustion engine with a sensor which determines the combustion process in a cylinder of the internal combustion engine.
In the process, a measure of the stability of the combustion process is formed from a quantity which characterizes a combustion process in a cylinder of the combustion engine, the determination of the composition of the fuel mixture being made from the measure of the stability of the combustion process.
The device includes a control unit for controlling the internal combustion engine on the basis of the output of the sensor, the output of the sensor being applied to a motor electronics as a measure of the combustion process and can be stored there over a predetermined number of combustion cycles, a statistical evaluation of the combustion pre-combustion engine can be stored. combustion stability, wherein the composition of the fuel mixture can be determined and a correction of the control of the combustion engine can be carried out from the measured measure of the stability of the combustion.
533 288
BACKGROUND OF THE ART
The invention relates to a method for determining the composition of a fuel mixture of a first fuel and at least a second fuel for operating a self-igniting internal combustion engine with at least one sensor which determines the combustion process in at least one cylinder.
The invention further relates to an apparatus for determining the composition of a fuel mixture of a first fuel and at least a second fuel for operating a self-igniting internal combustion engine with a variable or partially variable valve drive for variable adjustment of the valve openings depending on the crank angle and for variable setting of the valves of the valves. with a direct injection for dosing the fuel mixture, with at least one sensor for determining the combustion process in at least one cylinder of the internal combustion engine and with a control unit for controlling the internal combustion engine based on the sensor's output signal.
Self-igniting combustion processes in ottomotors are known under the terms gasoline HCCI (Homogeneous Charge Compression Ignition) or CAl (Controlled Auto Ignition) procedures. Compared to traditional processes, with ignition created by special devices, they have a significant potential for fuel savings in the event of reduced emissions of harmful substances.
533 288
Auto-ignition otto-type internal combustion engines are usually equipped with a variable valve drive and with a direct injection of gasoline. Various strategies are known to achieve CA1 operation. A common goal for these strategies is to achieve a relatively large residual gas mass in the combustion engine cylinder. This hot residual gas provides for the initiation of combustion during the compression phase.
Advantageously the control and control of combustion in a self-igniting internal combustion engine is advantageously based on a combustion chamber signal. As the sensor, the cylinder pressure sensors are preferably used here, which at high resolution over time determine the pressure flow during a combustion rate. In this case, for example, the indicated mean pressure pmi in at least one combustion chamber of the combustion engine can be used as a measure of the mechanical work done by the combustion engine and the position of the combustion center of gravity MFB50 (Mass Fraction Burnt 50%) controlled as control parameters.
Both ottomotors with special spark plugs and ottomotors with self-ignition are generally fueled with fossil fuel hydrocarbons based on refined crude oil. In this fuel, more and more ethanol or other alcohol produced from regenerating raw materials (plants) is added in various mixing conditions. In the US and Europe, a mixture of 70-85% ethanol and 15-30% gasoline is often used under the trade name E85. The internal combustion engines are designed to run on clean gasoline as well as with mixtures up to E85; this is called "Flex-Fuel-Drift". For economical operation with low emissions of harmful substances at the same time high engine power and good starting characteristics, the operating parameters of Flex-Fuel-Drift must be adapted to the respective fuel mixture present. For example, a stoichiometric fuel-air ratio is 14.7 parts by volume of air per share of gasoline, however, when using ethanol, an air portion of 9 volumes is set. Minor and / or slow changes in the alcohol content can be identified and taken into account by the combustion engine's motor control, for example by means of a lambda probe. However, rapid changes with considerable deviation in the composition of the fuel mixture may also occur, for example, after a refueling. According to the prior art, such rapid changes in the composition of the fuel mixture can be identified by means of an alcohol sensor. However, this component increases the cost of the internal combustion engine.
The addition of ethanol, in particular a high admixture rate of 50% to 85%, has a significant effect on the highly sensitive CA1 combustion. Measures to offset this impact are therefore necessary.
From the applicant's published patent application DE 10 2007 023 900.0 A1, a method for determining the composition of a fuel mixture of a first fuel and a second fuel for operating an internal combustion engine is known, the first and second fuels having different combustion rates and / or different specific energy content and wherein the combustion engine has at least one pressure sensor in at least one combustion chamber; by which a temporal and / or angular synchronous pressure course in the combustion chamber is determined. It is thereby ensured that the composition of the fuel mixture is determined from the temporal and / or angular synchronous pressure course of the gas pressure in the combustion chamber (s) during a combustion phase. A disadvantage here is that the effect of the ethanol blend on the evaluated standard factors, such as the indicated average pressure pmi as a measure of the work done by the combustion engine or as the combustion center of gravity MFB50, is not so strongly marked that a sufficiently accurate determination of combustion is possible. This is especially true at high admixture rates of more than 50% ethanol.
From the applicant's published patent application DE10 2007 060 223.7 A1 is known a method for determining the composition of a fuel mixture of a first fuel and a second fuel or for determining the quality of a fuel for operating an internal combustion engine with at least one cylinder pressure sensor in at least one cylinder of internal combustion engine too
533 288 determination of the pressure process during a combustion process and a cylinder pressure-based engine control for controlling the combustion engine load and combustion position. In this way, it is ensured that the determination of the composition of the fuel mixture or the quality of the fuel is made with the guidance of the cylinder pressure-based engine control information. Further, the use of the method is provided for determining the composition of a fuel mixture and / or the quality of a fuel for operating an internal combustion engine with special ignition and / or a self-ignition internal combustion engine. Particularly during operation of the internal combustion engine with medium to high partial load, ie at an indicated average pressure above 3 bar, the CAI combustion process becomes unstable when operating with different fuel mixtures without further measures. The direct determination of the composition of the fuel mixture on the basis of the cylinder pressure-based control information can only be carried out with very low accuracy under these operating conditions.
The object of the invention is to provide a method and apparatus which enable an accurate determination of the composition of a fuel mixture of at least two fuels for the operation of a self-igniting internal combustion engine.
DESCRIPTION OF THE INVENTION
BENEFITS OF THE INVENTION
The process of the invention with respect to the process is solved by forming a measure of the combustion process stability by statistical evaluation over several combustion cycles of a quantity which characterizes a combustion process in at least one cylinder of the combustion engine and the determination of the composition of the fuel mixture for the measurement of combustion combustion takes place. The CA1 combustion instability is the main characteristic of, for example, a high degree of ethanol blend in gasoline. In particular, the effect of an ethanol blend on combustion stability is more pronounced than on the standard factors indicated mean pressure pmi and combustion center position MFB50. Combustion instability is already so high at average load that it cannot be rated as acceptable. Therefore, a method, which identifies this instability, thereby determines the degree of browsing and directly compensates for its effects very advantageously.
The determination of the magnitude that characterizes the combustion process is made from a determination of a cylinder pressure or a determination of a silent sound signal of the internal combustion engine or a rotational speed of the internal combustion engine or from an ionic current of a probe in the cylinder, each separately or from at least two of these measurements. . In this case, the sensor already provided for the control of combustion in the self-igniting internal combustion engine is used on the basis of a combustion chamber signal, the sensor output signal being used for determining the combustion process.
A measure of combustion stability which is easy to determine can be achieved by measuring, as a measure of the stability of the combustion process in the cylinder (s), the standard deviation of a predetermined number of combustion cycles, the position of a combustion center of gravity, or the standard deviation of a indicated degree of displacement the standard deviation of a maximum differential energy release or the standard deviation of a maximum integrated energy release or the ratio of the standard deviation to the mean of the indicated cylinder mean pressure or a parameter derived from these quantities, each or at least two of these quantities are considered in combination. These quantities or at least some of these quantities are already available to a self-igniting internal combustion engine regulated on the basis of a combustion chamber signal, thus no further building elements are needed for the execution of the process. The number of combustion cycles that the statistical evaluation must take into account can be adjusted to the accuracy required and to the required evaluation speed. It can further be determined depending on the combustion engine's operating para 533 288 meters. The standard deviation of the quantities gives a direct measure of the spread of the parameters that characterize the combustion in successive combustion processes and consequently a statement regarding the stability of the combustion. For a fuel mixture with an ethanol blend degree exceeding 50%, the standard deviation of the MFB50 combustion center of gravity at a change of 5% ethanol blend may change 1.3 ° angle of rotation. This can be well evaluated, whereby a very good identification accuracy regarding the composition of the fuel mixture from 3% to 5% can be achieved at high ethanol blend rates. In addition to the direct statistical evaluation of the cylinder pressure-based quantities, further unambiguously correlating factors and parameters for determining the composition of the fuel mixture can also be evaluated.
According to a particularly preferred embodiment of the invention, the formation of the measure of the stability of the combustion process can take place at predetermined operating points of the internal combustion engine. The statistical evaluation of the combustion at idle enables well reproducible operating conditions, which often exist. The evaluation at a medium to high load of the combustion engine, on the other hand, results in large well-evaluable differences in the combustion stability of different composite fuel mixtures. It is ensured that a limit value for the measure of the stability of the combustion process is predetermined and that the operating parameters of the combustion engine are set so that the measure of the stability of the combustion process does not exceed the limit value, thus the obtained measure of the stability of the combustion process can be used. For example, in the event of an increase in combustion instability following a mixing change as a result of a refueling process, stability-enhancing measures can be immediately initiated to offset this effect.
Stabilization of the combustion can be achieved by observing the limit value for the measure of the stability of the combustion process, an increase of a residual gas mass in the cylinders of the combustion engine, or an earlier setting of a setpoint for controlling a combustion center of a burst respectively, or at least two of these measures in combination. All measures serve to increase the stability-enhancing temperature during the compression phase. For example, in the CA1 process of residual gas retention, the introduction of a fuel injection into the intermediate compression results in the release of energy and thereby a rise in temperature of the residual gases.
If the amount of hot residual gas in the cylinders of the combustion engine is increased during the compression phases, then this also results in an increase in the temperature of the gas mixture and an improved combustion start during the compression phase. Therefore, it may be ensured that the increase of the residual gas mass in the cylinders of the internal combustion engine occurs by a previous closing of the respective exhaust valve during the expulsion phase or by a brief opening of the respective exhaust valve during the suction rate. In combustion engines with several exhaust valves per cylinder, all exhaust valves can be controlled in a corresponding way.
The correction procedure for stabilizing the combustion in the control of the combustion engine takes place depending on the measure of stability formed. The size of the necessary corrective action therefore depends on the instability of the combustion engine's combustion and consequently on the composition of the fuel mixture. Therefore, in an alternative embodiment of the invention it may be ensured that the composition of the fuel mixture is determined by the necessary corrective intervention in the control of the combustion engine to observe the limit value for the measure of the stability of the combustion process.
The method may preferably be used to determine the composition of a gasoline / alcohol fuel mixture and / or to control or control the stability of the combustion process in a gasoline or petrol / alcohol fuel mixture self-igniting combustion engine.
533 288
The object of the invention with regard to the device is solved by the use of a sensor which is already provided for controlling the internal combustion engine, that a motor electronics with a storage unit is provided, whereby the output signal of the sensor as measured on the combustion process is supplied to the storage electronics , the engine electronics are provided with an evaluation device which is designed in such a way that a statistical evaluation of a quantity characterizing the combustion processes is carried out to determine a measure of the combustion stability; wherein the determination of the magnitude 10 which characterizes the combustion process takes place from a determination of a cylinder pressure or a determination of a silent sound signal of the internal combustion engine or a rotational speed of the internal combustion engine or an ionic current of a probe in the cylinder individually or from at least two of these meters. combination and that the device is further designed in such a way that the composition of the fuel mixture is determined and a proof of combustion engine control is carried out from the measured measure of combustion stability. The storage of the sensor data from successive combustion cycles enables the statistical evaluation, on the basis of which the stability of the combustion can be evaluated. If the combustion instability20 is determined, then direct intervention in the control and control of the internal combustion engine can be made to stabilize the combustion. For this purpose, the motor electronics can be directly connected to the combustion engine's control unit or the control unit is an integral component of the motor electronics. An admixture of, for example, ethanol in gasoline, depending on the admixture degree, gives a significant change in the combustion stability. Therefore, with the aid of the quantities that describe the combustion stability, a conclusion regarding the composition of the fuel mixture can be drawn. The composition of the fuel mixture so determined may be provided with additional control device functions, such as the lambda function, which can then properly adjust its calculations. Furthermore, the identification and compensation of an ethanol blend can be combined with a cylinder pressure based combustion camps 533 288 glazing, for example with the indicated average pressure pmi or the combustion center of gravity position MFB50 as control quantities.
It is provided that for determining the course of the combustion, at least one cylinder pressure sensor or at least one sensor for determining the combustion engine's audible signal or at least one speed sensor or at least one sensor for determining the ion current can be provided so that a supply of fuel can be provided so that . With these sensors, the position of a combustion center of gravity or an indicated cylinder mean pressure or a maximum pressure gradient in the cylinder or a maximum differential energy release or a maximum integrated energy release can be determined. From these quantities, the motor electronics can, by a suitable statistical evaluation over a predetermined number of combustion cycles, determine the respective standard deviation or the ratio of the standard deviation to the mean of, for example, the indicated cylinder mean pressure as a measure of the combustion stability. Preferably, the sensors which are already provided for controlling the combustion in the self-igniting internal combustion engine are used on the basis of a combustion chamber signal.
DESCRIPTION
The invention is explained in more detail below with reference to the embodiment illustrated in the figures. It shows:
Figure 1, through a first diagram, the effect of combustion instability on the standard deviation sMFB50 of the position of the combustion center at different loads (in pmi) in a self-igniting internal combustion engine;
Figure 2 through a second diagram the influence of the fuel composition on the differential heating process dQ, drawn against the crank angle.
DESCRIPTION OF EMBODIMENTS
533 288
Figure 1 shows through a first diagram 10 the effect of combustion instability on a standard deviation sMFB50 11 of the position of the combustion center of gravity at different loads (in pmi) in a self-igniting internal combustion engine. The internal combustion engine is then operated with gasoline or with a mixture of gasoline and ethanol according to the so-called CA1 (Controlled Auto Ignition) procedure, which is also called gasoline HCCI (HCCI: Homogeneous Charge Compression Ignition).
In the first diagram 10, the standard deviation sMFB50 11 in crank angle 10 is plotted against an indicated average pressure pmi 12 in bar. The indicated mean pressure pmi 12 defines the combustion engine load at a speed of 2000 rpm in the illustrated embodiment. The standard deviation sMFB50 11 of the position of the combustion center of gravity is determined in the illustrated embodiment over 20 consecutive combustion cycles.
It is a measure of the combustion stability, whereby a small standard deviation sMFB50 11 is present at a stable combustion and a correspondingly large spread in the position of the combustion center of gravity and consequently a high standard deviation sMFB50 11 is present at an unstable combustion.
In the first diagram 10, four curves sMFB50 20, 21, 22, 23 for different fuels and fuel mixtures are illustrated. The respective standard deviations sMFB50 at the indicated mean pressures pmi 12 of 2 bar, 2.5 bar and 3 bar have been determined.
The curve sMFB50 S95 20 shows the standard deviation sMFB50 11 depending on the combustion engine load for the fuel Super 95, ie gasoline with an octane number of 95. The curve sMFB50 E50 21 shows the same dependence for a fuel mixture E50 of 50% gasoline and 50% ethanol, the curve sMFB50 a fuel mixture of 15% gasoline and 85% ethanol. Curve sMFB50 E85 / -4<sup>0</sup>
KW 23 shows the standard deviation sMFB50 11 depending on the indicated mean pressure pmi 12 for a fuel mix E85, whereby an increase of the negative valve overlap at -4 ° crank angle is provided as a pre-stabilizing fire stabilizing measure. This measure, designated Exhaust Valve Closing (AEVC), retains a certain additional amount of residual gas in the cylinder.
An increasing standard deviation sMFB50 11 is shown in all combustion engine load areas with increasing ethanol content in the fuel mixture, which corresponds to an increase in combustion instability. Furthermore, for the respective fuels, an increase in the standard deviation sMFB50 11 is shown at rising load of the internal combustion engine, ie at rising indicated average pressure pmi 12.
Particularly from an average load of the internal combustion engine at an indicated average pressure pmi 12 of 3 bar, a strong dependence on the standard deviation sMFB50 11 on the composition of the fuel mixture can be observed. While Super 95 quality petrol shows a standard deviation sMFB50 11 of about 1 ° crank angle, it already rises at a fuel mixture E50 to a value of about 2 ° crank angle. Without stability-enhancing measures, the standard deviation sMFB50 11 for a fuel mix E85 rises to a value of about 11 ° crank angle, which means a significant effect on the combustion engine's operation no longer acceptable influence of the fuel composition on combustion stability. In the selected embodiment, the combustion control is active with the control quantities indicated mean pressure pmi 12 and the position of the combustion center of gravity MFB50. An increase in ethanol content of 5% between the fuel mixtures E50 and E85 means approximately an increase of the standard deviation MFB50 11 by a 1.3 ° turning angle, which can be easily detected.
The curves sMFB50 20, 21, 22, 23 show that the increasing instability of the CA1 combustion is an essential characteristic of a high degree of ethanol admixture. Thereby, the influence of the ethanol blend on combustion stability is more pronounced than on the standard factors indicated mean pressure pmi 12 or the position of the combustion center of gravity MFB50, which are used as control variables in conventional control concepts for self-igniting internal combustion engines. Furthermore, it can be observed that this instability, already at a medium part load 335 characterized by an indicated average pressure pmi 12 of 3 bar, is so great that it can no longer be considered acceptable. Therefore, a method that identifies this instability, thereby determining the degree of interference and compensating for its effects, is very advantageous.
From a comparison of the curve MFB50 E85 / -4<sup>0</sup> The KW 23 process, for a fuel mix E85 and an AEVC = -4 ° turn angle preceded shut-off of the exhaust valve, with the curve sMFB50 E85 22 further shows that the negative valve overlap with thereby achieved increased residual gas volume in the cylinder provides a clear improvement of the combustion stability. Alternatively, to stabilize the combustion, residual gas can also be sucked back by briefly opening the exhaust valve during the suction phase.
Figure 2 shows in a second diagram 30 the influence of the fuel composition on the differential heating process dQ 31, again for a self-igniting combustion engine driven by the CA1 process with active combustion control. Thereby, gasoline or a mixture of gasoline and ethanol is provided as fuel.
Shown is the differential heat flow dQ 31 in joules per degree of crank angle versus crank angle at degree crank angle. The differential heat flow dQ 31 can be calculated from a measured cylinder pressure flow and is a measure of the energy release per degree of angle of rotation.
The second diagram 30 contains five curves dQ 40, 41,42, 43, 44, which show the differential heat dQ 31 depending on the crank angle 32 for different fuel mixtures and for various measures that stabilize the combustion stability. The averages of the individual values of the curves dQ 40, 41, 42, 43, 44 are shown over 20 combustion cycles.
The curve dQ S95 40 shows the differential heating process dQ 31 depending on the crank angle 32 for petrol of the quality Super 95. The curve dQ E50 41 illustrates533 288 makes the differential heating process dQ 31 for a fuel mixture E50, ie 50% gasoline and 50% ethanol. dQ E85 42 shows the differential heating process dQ 31 for a fuel mixture E85, ie 15% gasoline and 85% ethanol.
Curve dQ E85 / -4<sup>0</sup> KW 43 illustrates the differential heating process dQ 31 for a fuel mix E85 during operation of the internal combustion engine with an increase of the negative valve overlap of -4 ° as a measure to improve combustion stability, while the curve dQ E85 / -8<sup>0</sup> KW 44 illustrates correspondingly in the case of an increase in the negative valve overlap of -8 °.
The progress of curve dQ S95 40, curve dQ E50 41 and curve dQ E85 42 show the effect of an increasing degree of ethanol admixture on the differential heat flow dQ 31. The smaller local around the middle more smoothed combustion at fuel mixture E85 compared to fuel Super 95 can be clearly identified. This is evidenced by the progress over a larger crank angle range of curve dQ E85 42 compared to curve dQ S95 40 and the less pronounced maximum value of curve dQ E85 42. The curve dQ E50 41 lies between the two curves dQ S95 40 and dQ E85 42. The result corresponds to the statistical evaluation of the standard deviation sMFB50 11, which is shown in Figure 1.
By stability-enhancing measures, which in the exemplary embodiment increased retention of residual gas by an early closing of the exhaust valve of -4 ° crank angle in accordance with the curve dQ E85 / -4<sup>0</sup> KW 43 or about -8 ° turning angle in accordance with curve dQ E85 / -8<sup>0</sup> KW 44, the heating process can again approach the original curve dQ S95 40 for pure gasoline.
It can be seen from the relationships illustrated in Figures 1 and 2 that by means of a statistical evaluation of parameters that characterize combustion, a measure of the combustion stability can be obtained, which strongly correlates with the composition of the fuel mixture and is easy to evaluate.
533 288
This allows for the determination of the composition of the fuel mixture and the initiation of measures to stabilize the combustion stability.
The method rests on a feedback from at least one combustion chamber of the internal combustion engine, which can be obtained by measuring the cylinder pressure, a silent signal), the internal combustion engine speed or an ion current signal.
On the basis of the signal obtained, at least one factor which characterizes the combustion is determined, which is evaluated statistically over several combustion cycles to obtain a factor which characterizes the combustion stability.
Suitable factors that characterize the combustion stability are, for example, the cylinder pressure-based factors
- the standard deviation of the combustion center position MFB50
- the standard deviation of the indicated mean pressure pmi
- the standard deviation of the maximum pressure gradient one ppm
- the standard deviation of the maximum differential energy release dQmax
- the standard deviation of the maximum integrated energy release dQmax or derived factors such as the ratio of the standard deviation to the mean of the indicated mean pressure pmi.
Further suitable quantities are calculated from the signals from the measurement of the cylinder pressure, the audible noise signal, the internal combustion engine speed or the ion current signal, which clearly correlate with the said cylinder pressure-based factors.
533 288
For example, if, after a tank operation, an increase in combustion instability is observed in a CA1 operating point, then stability-enhancing measures can be initiated without delay, to offset this effect. Hereby, for example, an increase in the hot residual gas mass is suitable through an earlier closing of the exhaust valve, an earlier displacement of an MFB50 control setpoint or the introduction of a pre-injection amount, which during the intermediate compression results in the release of energy and consequently a rise in temperature of the residual gases.
This can be done within the framework of a control or control, in which the setpoint is a maximum value for the instability factor, for example, the standard deviation sMFB50 11 of the combustion center of gravity position. In the control case, the identification can also be done indirectly, ie not by the increase of the instability factor but by the size of the necessary correction rope.
The determined composition of the fuel mixture can be provided with additional control device functions, such as the lambda function, which can thereby properly adjust their calculations.
Furthermore, it is possible to combine, as control quantities, the identification and compensation of the composition of the fuel mixture with a cylinder pressure-based combustion position control, for example with the indicated mean pressure pmi 12 and the position of the combustion center of gravity MFB50.
533 288
Ib
Contents9
4 sheets
Sheet 1 Sheet 2 Sheet 3 Sheet 4
6 members in 4 offices
Priority claims4
| Document | Office | Kind | Date |
|---|---|---|---|
| 102008001668 | Germany | A | |
| 102008001668 | Germany | A | |
| 1020080016 | – | – | – |
| DE20081001668 | – | – | – |
Members6
| Document | Office | Kind | |
|---|---|---|---|
| SE0950297L | Sweden | L | |
| DE102008001668A1 | Germany | A1 | |
| US2009281708A1 | United States of America | A1 | |
| BRPI0901606A2 | Brazil | A2 | |
| SE533288C2This record | Sweden | C2 | |
| US8032294B2 | United States of America | B2 |
Numbers
- Publication, DOCDB
- 533288
- Publication, EPODOC
- SE533288
- Application
- 950297
- Application, DOCDB
- 0950297
- Application, EPODOC
- SE20090050297
Titles2
- English
- Method and apparatus for determining the composition of a fuel mixture
- Swedish
- Förfarande och anordning för bestämning av en bränsleblandnings sammansättning
Classification
- CPC, 18
- F02D35/02
- F02D19/08
- F02B1/12
- F02D13/0249
- F02D13/0273
- F02D35/023
- F02D35/028
- F02D41/0025
- F02D41/3035
- F02D2200/0612
- F02D19/084
- F02D19/088
- F02D35/021
- F02D2041/286
- F02M26/01
- Y02T10/30
- F02D41/1497
- G01N33/2852
- IPC, 4
- G01N33 22
- F02D19 08
- F02D41 00
- F02D41 14
