CN106548029A - The determination method of the regular empirical coefficient of weber burning - Google Patents

Abstract

It is an object of the invention to provide the determination method of the regular empirical coefficient of weber burning, using weber (Wiebe) combustion law for having existed, linear transformation is carried out to formula, and with reference to the experimental data of existing measure, linear fit is carried out to weber (Wiebe) combustion law using least square method, the empirical coefficient in weber (Wiebe) burning rule is rapidly and precisely calculated.The zero dimension combustion model of rule of being burnt based on weber (Wiebe) so as to fast construction.Present invention reduces the simulation study time of internal combustion engine in-cylinder combustion, significantly increases the reliability and accuracy of empirical coefficient, the efficient matchings of burning rule and true burning are realized.

Description

The determination method of the regular empirical coefficient of weber burning

Technical field

The present invention relates to the Forecasting Methodology of engine combustion rule.

Background technology

In order to solve increasingly serious problem of environmental pollution, International Emissions regulation is more and more harsher, limits having for engine Evil emission, causes manufacturer, and the emission control to engine is seen particularly important.And in the emission performance of diesel engine and cylinder Combustion process has close contact, therefore it is important to realize that emission control of the real-time control to combustion process to engine has Meaning.With the fast development of computer technology, computer simulation technique has flourishing vitality, by reality system Abstract imitation, take out system model, people are simulated experimental study to such model on computers, have both dropped saving Research and production costs, reduce risk, also improve scientific research efficiency.So reliability and accuracy of system model, directly Connect the reliability and accuracy for determining simulation result.In field of internal combustion engine, zero dimension combustion model-weber (Wiebe) combustion model It is in-cylinder combustion procedures system model, simply, modeling difficulty is little for combustion model, while possessing certain in certain condition range Simulation accuracy.By this standard weber Wiebe) based on combustion model, numerous researchers successfully to direct-injection, non-direct-injection, Two stroke diesel engine has carried out the prediction of in-cylinder pressure and temperature.Although weber Wiebe) the regular empirical coefficient of burning can be direct The accuracy of weber (Wiebe) combustion model is affected, but seldom has the document can be to the experience of standard weber (Wiebe) combustion model The selection of coefficient is specialized in.

The content of the invention

It is an object of the invention to provide improving the accuracy of weber (Wiebe) burning rule, realizing to combustion process The determination method of the regular empirical coefficient of weber burning of real-time precise control.

The object of the present invention is achieved like this：

The determination method of weber burning rule empirical coefficient of the present invention, is characterized in that：

(1) according to weber burning rule：Wherein x_bIt is burning product for fuel percentage, m Matter index, a be the efficiency of combustion factor,For instantaneous crank angle,For combustion continuation angle,For timing of combustion, orderFor 0% The corresponding crank angle of the fraction of combustionAfter algebraic transformation, conversion, the expression formula of weber burning rule is as follows：

(2) by after conversion weber burning rule expression formula carry out linearization process, make A=m+1,The linearisation equation of weber burning rule It is converted into：

(3) via measuringAnd x_bN group data, respectively Obtain the linearisation equation of weber burning ruleCorresponding experimental data WhereinAccording to same method Draw

(4) data distribution of the linearisation equation of weber burning rule is presented the relation of linear function, then a linear most young waiter in a wineshop or an inn Corresponding normal equation is taken advantage of to be system of linear equations, the coefficient matrix of system of linear equations is nonsingular, and equation group has unique solution, then Weber burning regular linear equation group is as follows：

Obtained according to equation group：

(5) by step (4), after being fitted curve coefficients A and B, weber burning rule are drawn by substitution of variable Empirical coefficient then：

Combustion quality index

The efficiency of combustion factor

(6) according to the combustion quality exponent m and efficiency of combustion factor a for obtaining, try to achieve timing of combustion WhereinIt is taken as q_rThe corresponding crank angle of maximum, q_rTo fire fraction x_bIt is right Derivative.

Advantage of the invention is that：The present invention is regular according to traditional weber (Wiebe) burning, using available data and minimum Square law algorithm, is fitted to weber (Wiebe) regular linear, calculates efficiency of combustion factor a and combustion quality exponent m, leads to Cross the regular empirical coefficient of weber (Wiebe) burning that the method draws, with higher reliability and stability, high degree The error of the system convention brought because of the error of empirical coefficient is reduced, the real-time precise control to combustion process is realized, is Engine energy-saving is reduced discharging and provides feasible program.

Description of the drawings

Fig. 1 is the flow chart of the present invention.

Specific embodiment

Illustrate below in conjunction with the accompanying drawings and the present invention is described in more detail：

With reference to Fig. 1, the core of the present invention there is provided the determination method of the regular empirical coefficient of weber (Wiebe) burning, with Obtain the burning rule of more high precision.In order that the technical staff of field of internal combustion engine is better understood from the present invention program, and pass through Preferred example in detail embodiments of the present invention.

Present example, there is provided the regular following parameter side of weber (Wiebe) burning of internal combustion engine zero dimension burning modeling Journey：

Wherein：x_bFor fuel percentage；M is combustion quality index；A is the efficiency of combustion factor；- instantaneous bent axle

Corner；- combustion continuation angle；- timing of combustion.

Then in IC engine cylinder, zero dimension models the determination method of the regular empirical coefficient of weber (Wiebe) burning, and which specifically includes Following steps：

Step 1：According to above-mentioned weber (Wiebe) burning rule,Order

For the 0% corresponding crank angle of the fraction of combustionWeber (Wiebe) the burning rule after algebraic transformation, conversion Then

Expression formula it is as follows：

Step 2：According in step 1, weber (Wiebe) the burning rule after deformation carries out linearization process, makes A=m+ 1；So weber (Wiebe) burning is regular Linearisation equation be：

Step 3：Via the n group data of measuring, respectively In step 2, it has been assumed thatSo Wei weber (Wiebe) burning The linearisation equation of ruleCorresponding experimental data Can just combine and draw, its method is： Can draw in the same manner

Step 4：Because the data distribution of the linearisation equation of weber (Wiebe) burning rule is presented the pass of linear function System, so the normal equation corresponding to linear least-squares must be system of linear equations, the coefficient matrix of system of linear equations is non-strange It is different, and equation group has unique solution, then weber (Wiebe) burning regular linear equation group is as follows：

Solve this equation group to obtain：

Step 5：By step 4, curve coefficients A and B after fitting are given, can be calculated by substitution of variable Go out the empirical coefficient of weber (Wiebe) burning rule, it is as follows：

Combustion quality exponent m=A-1；So

The efficiency of combustion factorSo

Extremely This is according to the experimental data for determining, it is possible to calculate the empirical coefficient of weber (Wiebe) burning rule.

Step 6：According to the combustion quality exponent m and efficiency of combustion factor a obtained, using formula

Obtain timing of combustionIt is taken as q_r(q_rTo fire fraction x_bIt is right Derivative) the corresponding crank angle of maximumx_bsmaxForPlace is corresponding to have fired fraction.

Using available data and least square method algorithm, weber (Wiebe) regular linear is fitted, calculates burning effect Rate factor a and combustion quality exponent m, the regular empirical coefficient of the weber drawn by the method (Wiebe) burning, with higher Reliability and stability, the error for reducing the system convention brought because of the error of empirical coefficient of high degree, to follow-up The deep tool of engine simulation research is of great significance.

The determination method concrete principle of the regular empirical coefficient of weber (Wiebe) burning is as follows：

There are four empirical coefficients in weber (Wiebe) burning rule, by adjusting empirical coefficient to be fitted the combustion for measuring Fraction x_bWith than heat liberation rate, heat release rate q_r.It is regular for nonlinear function, the wherein calibration of empirical coefficient yet with weber (Wiebe) burning With certain difficulty.For the fraction of combustion for measuring and than heat liberation rate, heat release rate, there is substantial amounts of noise signal and introduced by Calculation of Heat Transfer Uncertainty, need to take certain measure to avoid noise signal and the uncertain interference to the calibration of Wiebe empirical coefficients. Fire fraction and the ignition initial point for thus calculating is also resulted in than the noise signal in heat liberation rate, heat release rate and uncertaintyExist very big It is uncertain.To reduce the difficulty of empirical coefficient calibration, conventional method is generally adoptedAs in weber (Wiebe) burning rule Timing of combustionUnder each operating mode, efficiency of combustion factor a is taken as identical definite value.However, research shows, willAs In Wiebe burning rulesCalibration accuracy larger fluctuation can be made；A is taken as different definite values with working conditions change, compare take it is identical Definite value, the regular fitting precision of weber (Wiebe) burning can be significantly improved；A is compared, and fraction has been fired to burn profile index (m) It is more sensitive, therefore m needs more estimation with caution；Fraction is fired to the susceptibility of each empirical coefficient and substantially more proportional than heat liberation rate, heat release rate Relation.According to above research conclusion, the present invention proposes following corrective measure to reduce the calibration essence of weber (Wiebe) burning rule Degree：

1st, cast out x_b≤ 5% and x_b>=95% test data, using 95% ＞ x_bTest data between ＞ 5% is carried out The regular empirical coefficient of calibration weber (Wiebe) burning.

2nd, m is first calibrated, a is calibrated according to m then.

3rd, a is obtained according to m, and operating mode difference value is different.

4th, adopt q_rTake data point at maximum to be calculated according to m and a

Claims (1)

1. the determination method of the regular empirical coefficient of weber burning, is characterized in that：

(1) according to weber burning rule：Wherein x_bRefer to for combustion quality for fuel percentage, m Number, a be the efficiency of combustion factor,For instantaneous crank angle,For combustion continuation angle,For timing of combustion, orderFor 0% The corresponding crank angle of combustion fractionAfter algebraic transformation, conversion, the expression formula of weber burning rule is as follows：

(2) by after conversion weber burning rule expression formula carry out linearization process, make A=m+1,

The linearisation of weber burning rule Equation is converted into：

(3) via measuringAnd x_bN group data, respectively Obtain The linearisation equation of weber burning ruleCorresponding experimental data WhereinDraw according to same method

(4) data distribution of the linearisation equation of weber burning rule is presented the relation of linear function, then linear least-squares institute Corresponding normal equation is system of linear equations, and the coefficient matrix of system of linear equations is nonsingular, and equation group has unique solution, then weber Burning regular linear equation group is as follows：

Obtained according to equation group：

$A=1/n\[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\widetilde{y_i}-\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\widetilde{x_i}.\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\widetilde{y_i}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\widetilde{x_i}-n\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\widetilde{x_i}\widetilde{y_i}}{{\left(\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\widetilde{x_i}\right)}^2-n\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\left(\widetilde{x_i}\right)}^2}\]$

$B=\frac{\underset{i=1}{\overset{n}{\Σ}}\widetilde{y_i}\underset{i=1}{\overset{n}{\Σ}}\widetilde{x_i}-n\underset{i=1}{\overset{n}{\Σ}}\widetilde{x_i}\widetilde{y_i}}{{\left(\underset{i=1}{\overset{n}{\Σ}}\widetilde{x_i}\right)}^2-n\underset{i=1}{\overset{n}{\Σ}}{\left(\widetilde{x_i}\right)}^2};$

(5) by step (4), after being fitted curve coefficients A and B, weber burning rule is drawn by substitution of variable Empirical coefficient：

Combustion quality index

The efficiency of combustion factor

(6) according to the combustion quality exponent m and efficiency of combustion factor a for obtaining, try to achieve timing of combustion WhereinIt is taken as q_rThe corresponding crank angle of maximum, q_rTo fire fraction x_bIt is rightDerivative.