CN108918588B - Method for simulating combustion state of high-pressure common-rail diesel engine - Google Patents
Method for simulating combustion state of high-pressure common-rail diesel engine Download PDFInfo
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Abstract
The invention discloses a method for simulating a combustion state of a high-pressure common-rail diesel engine, which comprises the following steps: the method comprises the following steps: using a double-Weber combustion mathematical model, wherein the double-Weber combustion mathematical model comprises a main combustion stage combustion mathematical model and a tail combustion stage combustion mathematical modelMolding; step two: the method comprises the following steps of carrying out multiple combustion tests on the high-pressure common-rail diesel engine under normal working conditions, and collecting the following test data: corner of crankshaft
The burned fraction xb and the total heat release Qg, and drawing a heat release curve chart; step three: the heat release profile is analyzed and based on the known crank angle
And (3) fitting the heat release curve graph according to a double-Weber combustion mathematical model by using the burned fraction xb and the total heat release Qg, solving the Qg1 and the Qg2, and obtaining a fitted curve graph. Therefore, the method for simulating the combustion state of the high-pressure common rail diesel engine can obviously improve the fit degree of the model and the experimental value, and can set more reasonable control parameters, so that the development of the controller is better carried out.
Description
Technical Field
The invention relates to the technical field of combustion heat release of diesel engines, in particular to a method for simulating a combustion state of a high-pressure common-rail diesel engine.
Background
The diesel Engine Controller (ECU) is equivalent to the brain of the diesel engine electric control system, and outputs execution signals to each execution mechanism through the input of sensor signals and the calculation of the controller, so that the diesel engine can work correctly. Controller development traditionally uses hundreds to thousands of tables, uses a large amount of statistical data to build an interpolation mathematical model, takes an input signal as an input, and obtains an output execution signal through interpolation.
With the development of control technology, especially the advantages of model-based controller development technology in controller development becoming more and more obvious, the development of diesel engine controllers is also trending toward the development of model-based technology. The diesel engine controller development based on the model is to model each subsystem of the diesel engine through some mathematical formulas with physical significance, and is not a simple method of traditional table interpolation. At this time, each subsystem is either directly a mathematical formula derived from the physical meaning of the system or a semi-empirical mathematical model with the physical meaning.
In the controller, the most central system is the combustion system. Because the heat release process of the diesel engine is very complex and cannot be deduced by using a mathematical formula, a semi-empirical formula model with physical significance is more prone to be used traditionally, wherein a double weber heat release law model is most commonly used on the diesel engine. A double-Weber heat release law model divides diesel engine combustion into two stages of premixed combustion and diffusion combustion, and two Weber functions are used for representing the two stages respectively.
In the traditional mechanical pump era, because the injection pressure is lower, the duration of the premixing stage is long, the heat release process is obvious, and the combustion heat release law expressed by using the double Weber function is more consistent with the actual situation. However, for the existing high-pressure common rail injection diesel engine, the injection pressure is large, the speed is high, the atomization performance is good, the premixing combustion stage is not obvious any more, even can be ignored, and the applicability of the double-Weber function is not good any more.
As shown in fig. 1 to 2, fig. 1 is a graph showing a combustion heat release law of a diesel engine with a certain mechanical pump; fig. 2 is a graph showing a combustion heat release law of a certain conventional high-pressure common rail diesel engine. The combustion heat release rule curve of the mechanical pump diesel engine presents two wave crests which respectively represent two processes of premixed combustion and diffusion combustion; on a high-pressure common rail diesel engine, a small peak of premixed combustion cannot be seen, the whole combustion has only one peak, and if a traditional double-Weber combustion model is used for fitting the heat release rule, the heat release rule cannot be well matched with a test value.
As shown in fig. 3, fig. 3 is a graph of a heat release law of a conventional high-pressure common rail diesel engine fitted by a double weber function. In FIG. 3, the heat release rate curve at the initial stage of combustion, which has a very insignificant premixed combustion process, can be better matched by using the dual Weber function. However, at the end of combustion, the error between the double weber function and the test value is large, which indicates that the traditional double weber combustion model is not suitable for the current high-pressure common rail diesel engine. The method has the advantages that the fitting effect of the existing double-Weber combustion model based on the premixed combustion and the diffusion combustion stages on the combustion heat release of the high-pressure common rail diesel engine is poor, and the defect that the actual combustion heat release rule of the high-pressure common rail diesel engine is inconsistent is overcome.
The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Disclosure of Invention
The invention aims to provide a method for simulating the combustion state of a high-pressure common rail diesel engine, so as to overcome the defects that a double-Weber combustion model based on premixed combustion and diffusion combustion stages in the prior art has poor fitting effect on heat release of the high-pressure common rail diesel engine and is inconsistent with the actual combustion heat release rule of the high-pressure common rail diesel engine.
In order to achieve the aim, the invention provides a method for simulating the combustion state of a high-pressure common rail diesel engine, which comprises the following steps: the method comprises the following steps: a double-weber combustion mathematical model is used, and comprises a main combustion stage combustion mathematical model and a tail combustion stage combustion mathematical model; step two: the method comprises the following steps of carrying out multiple combustion tests on the high-pressure common-rail diesel engine under normal working conditions, and collecting the following test data: corner of crankshaft
The burned fraction xb and the total heat release Qg, and drawing a heat release curve chart; step three: the heat release profile is analyzed and based on the known crank angle
Fitting the heat release curve graph according to a double-Weber combustion mathematical model by using the burned fraction xb and the total heat release Qg, solving Qg1 and Qg2, and obtaining a fitted curve graph;
wherein c1 represents the combustion coefficient in the main combustion stage, c2 represents the combustion coefficient in the tail combustion stage, Qg1 represents the heat release value in the main combustion stage, Qg2 represents the heat release value in the tail combustion stage, m represents the combustion quality index,
z represents the duration of combustion,
which indicates the angle of the start of combustion,
indicates the combustion duration of the main combustion,
indicating the combustion duration of the tail-burn,
a crank angle indicating the time of day,
indicating the combustion initiation angle of the main combustion,
indicating the combustion initiation angle of the tail-burn,
and
represents a crank angle, and Q represents a heat release amount;
step four: adjusting the proportion of Qg1 and Qg2 in the fitting curve graph, respectively calculating the fitting degree of the fitting curve graph and the heat release curve graph under different proportion conditions of Qg1 and Qg2 through Eviews software, and determining the parameters of the fitting curve graph when the value of the fitting degree R is greater than 0.99 to obtain a double-Weber combustion mathematical model of the high-pressure common-rail diesel engine; step five: and inputting the formula of the obtained double-weber combustion mathematical model and various parameters in the formula into a diesel engine controller to obtain the diesel engine controller based on the main combustion and tail combustion double-weber combustion mathematical model.
Preferably, in the above technical solution, the degree of fitting is calculated by one of a residual sum of squares test, a chi-square test or a linear regression test.
Preferably, in the above technical solution, the heat release value Qg1 in the main combustion stage accounts for 90% -95% of the total heat release, the heat release value Qg2 in the tail combustion stage accounts for 5% -10% of the total heat release, and the sum of the heat release value Qg1 in the main combustion stage and the heat release value Qg2 in the tail combustion stage is the total heat release Qg.
Preferably, in the above technical solution, the combustion quality index m is equal to 2.0.
Preferably, in the above technical solution, c1 ═ c2 ═ 6.9.
Preferably, in the above technical solution, the combustion initiation angle
The crank angle corresponding to the burned fraction of 1% was taken.
Compared with the prior art, the invention has the following beneficial effects: the method for simulating the combustion state of the high-pressure common rail diesel engine can obviously improve the fit degree of the model and the test value, and can set more reasonable control parameters, thereby better developing a controller.
Drawings
FIG. 1 is a graph of the combustion heat release profile of a prior art mechanically pumped diesel engine.
Fig. 2 is a graph showing a combustion heat release law of a certain conventional high-pressure common rail diesel engine.
FIG. 3 is a graph of the heat release law of the existing high-pressure common rail diesel engine fitted by a double Weber function.
FIG. 4 is a graph of a heat release law of a double-Weber function fitting high-pressure common rail diesel engine according to the method for simulating the combustion state of the high-pressure common rail diesel engine.
Fig. 5 is a graph of the relationship between the ignition start angle and the main combustion in the method for simulating the combustion state of the high pressure common rail diesel engine according to the present invention.
Detailed Description
The following detailed description of the present invention is provided in conjunction with the accompanying drawings, but it should be understood that the scope of the present invention is not limited to the specific embodiments.
Throughout the specification and claims, unless explicitly stated otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or component but not the exclusion of any other element or component.
Fig. 4 is a graph of a heat release law of a double weber function fitting high-pressure common rail diesel engine according to the method for simulating the combustion state of the high-pressure common rail diesel engine of the present invention, as shown in fig. 1 to 5, and fig. 5 is a graph of a relationship between a tail-burning start angle and a main burning in the method for simulating the combustion state of the high-pressure common rail diesel engine according to the present invention.
The method for simulating the combustion state of the high-pressure common rail diesel engine comprises the following steps of: the method comprises the following steps: a double-weber combustion mathematical model is used, and comprises a main combustion stage combustion mathematical model and a tail combustion stage combustion mathematical model; step two: carrying out multiple combustion tests on the high-pressure common-rail diesel engine under normal working conditions, and collecting the following testsAnd (3) data testing: corner of crankshaft
The burned fraction xb and the total heat release Qg, and drawing a heat release curve chart; step three: the heat release profile is analyzed and based on the known crank angle
Fitting the heat release curve graph according to a double-Weber combustion mathematical model by using the burned fraction xb and the total heat release Qg, solving Qg1 and Qg2, and obtaining a fitted curve graph;
wherein c1 represents the combustion coefficient in the main combustion stage, c2 represents the combustion coefficient in the tail combustion stage, Qg1 represents the heat release value in the main combustion stage, Qg2 represents the heat release value in the tail combustion stage, m represents the combustion quality index,
z represents the duration of combustion,
which indicates the angle of the start of combustion,
indicates the combustion duration of the main combustion,
indicating the combustion duration of the tail-burn,
a crank angle indicating the time of day,
indicating the combustion initiation angle of the main combustion,
indicating the combustion initiation angle of the tail-burn,
and
represents a crank angle, and Q represents a heat release amount;
step four: adjusting the proportion of Qg1 and Qg2 in the fitting curve graph, respectively calculating the fitting degree of the fitting curve graph and the heat release curve graph under different proportion conditions of Qg1 and Qg2 through Eviews software, and determining the parameters of the fitting curve graph when the value of the fitting degree R is greater than 0.99 to obtain a double-Weber combustion mathematical model of the high-pressure common-rail diesel engine; step five: and inputting the formula of the obtained double-weber combustion mathematical model and various parameters in the formula into a diesel engine controller to obtain the diesel engine controller based on the main combustion and tail combustion double-weber combustion mathematical model.
Preferably, the degree of fit is calculated by one of a residual sum of squares test, a chi-square test or a linear regression test method.
Preferably, the heat release value Qg1 for the main burn stage is 90% -95% of the total heat release, the heat release value Qg2 for the tail burn stage is 5% -10% of the total heat release, and the sum of the heat release value Qg1 for the main burn stage and the heat release value Qg2 for the tail burn stage is the total heat release Qg.
Preferably, the combustion quality index m is equal to 2.0; c1 ═ c2 ═ 6.9; angle of combustion initiation
The crank angle corresponding to the burned fraction of 1% was taken.
In summary, referring to fig. 4 to 5, the tail-burning starts substantially near the end of the main-burning stage (90% -95% of the burning is completed), and the physical meaning of the tail-burning is satisfied: immediately after the main fuel combustion is completed, the partially unburned fuel concentration is low, and the ignition is slowly continued in a high-temperature environment.
In summary, the method for simulating the combustion state of the high-pressure common rail diesel engine has the following beneficial effects:
1. the combustion model provided by the invention is composed of two weber functions of main combustion and tail combustion, which respectively represent the main combustion heat release process and the later-stage slow continuous combustion process of the diesel engine, and through fitting, a new combustion model can be well matched with a test value; moreover, the combustion model provided by the invention has clear physical significance: after the fuel combustion is finished, the concentration of the fuel which is not completely combusted is low, and the fuel is slowly and continuously ignited in a high-temperature environment; the tail combustion is started basically when the main combustion stage is close to the end, and the physical meaning of the tail combustion is met;
2. the double-weber combustion model provided by the invention has the advantages that the parameters of the double-weber combustion model are consistent with those of the double-weber combustion model based on the premixed combustion and diffusion combustion stages in the prior art, the parameters are not required to be additionally increased on the basis of the original diesel engine control system software, the controller can be developed on the basis of the original software, the construction period is not influenced, the original control system software can be directly used, the bottom layer of the control software is not required to be changed, the implementation method is simple and fast, and the difficulty is low;
3. the method for simulating the combustion state of the high-pressure common rail diesel engine obtains the crank angle of a double-Weber combustion mathematical model by performing experiments on the high-pressure common rail diesel engine
Parameters such as the burned fraction xb and the total heat release Qg are fitted with a curve through experimental parameters, so that the reliability of the fitted curve is higher than that of theoretical calculation, and the fitted curve and a heat release curve graph obtained through actual test are used for further optimizing the fitted curve, so that the double-weber combustion mathematical model is more consistent with the combustion heat release condition of the high-pressure common rail diesel engine;
4. the double-Weber combustion model provided by the invention can obviously improve the fit degree of the model and the test value, and can set more reasonable control parameters, so that the development of a controller is better carried out.
The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable one skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.
Claims (6)
1. A method for simulating the combustion state of a high-pressure common rail diesel engine is characterized by comprising the following steps:
the method comprises the following steps: a double-weber combustion mathematical model is used, and the double-weber combustion mathematical model comprises a main combustion stage combustion mathematical model and a tail combustion stage combustion mathematical model;
step two: the method comprises the following steps of carrying out multiple combustion tests on the high-pressure common-rail diesel engine under normal working conditions, and collecting the following test data: corner of crankshaft
The burned fraction xb and the total heat release Qg, and drawing a heat release curve chart;
step three: the heat release profile is analyzed and based on the known crank angle
Fitting the heat release curve graph according to a double-Weber combustion mathematical model by using the burned fraction xb and the total heat release Qg, solving Qg1 and Qg2, and obtaining a fitted curve graph;
wherein c1 represents the combustion coefficient in the main combustion stage, c2 represents the combustion coefficient in the tail combustion stage, Qg1 represents the heat release value in the main combustion stage, Qg2 represents the heat release value in the tail combustion stage, m represents the combustion quality index,
the duration of combustion is indicated,
which indicates the angle of the start of combustion,
indicates the combustion duration of the main combustion,
indicating the combustion duration of the tail-burn,
a crank angle indicating the time of day,
indicating the combustion initiation angle of the main combustion,
indicating the combustion initiation angle of the tail-burn,
and
represents a crank angle, and Q represents a heat release amount;
step four: adjusting the proportion of Qg1 and Qg2 in the fitting curve graph, respectively calculating the fitting degree of the fitting curve graph and the heat release curve graph under different proportion conditions of Qg1 and Qg2 through Eviews software, and determining the parameters of the fitting curve graph when the value of the fitting degree R is greater than 0.99 to obtain a double-Weber combustion mathematical model of the high-pressure common-rail diesel engine;
step five: and inputting the formula of the obtained double-weber combustion mathematical model and various parameters in the formula into a diesel engine controller to obtain the diesel engine controller based on the main combustion and tail combustion double-weber combustion mathematical model.
2. The method of simulating a combustion state of a high pressure common rail diesel engine according to claim 1, wherein the degree of fitting is calculated by one of a residual sum of squares test, a chi-square test, or a linear regression test.
3. The method for simulating the combustion state of a high pressure common rail diesel engine according to claim 1, wherein the heat release value Qg1 of the main combustion stage accounts for 90% -95% of the total heat release, the heat release value Qg2 of the tail combustion stage accounts for 5% -10% of the total heat release, and the sum of the heat release value Qg1 of the main combustion stage and the heat release value Qg2 of the tail combustion stage is the total heat release Qg.
4. The method for simulating the combustion state of a high-pressure common rail diesel engine according to claim 1, wherein the combustion quality index m is equal to 2.0.
5. The method for simulating the combustion state of the high-pressure common rail diesel engine according to claim 1, wherein c 1-c 2-6.9.
6. The method of simulating a combustion state of a high pressure common rail diesel engine of claim 1, wherein the combustion initiation angle is
The crank angle corresponding to the burned fraction of 1% was taken.
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| CN107092723B (en) * | 2017-03-22 | 2020-11-03 | 哈尔滨工程大学 | Automatic calibration method for empirical parameters of double weber combustion rules |
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