Disclosure of Invention
Aiming at the technical problems, the invention provides an engine key technology evaluation method based on fuel economy, which can determine the sensitivity, influence weight and interaction between key technologies of the key technologies to the fuel economy of an engine, thereby shortening the development period, improving the efficiency, reducing the cost and better providing a theoretical basis for the development of the engine.
The invention is realized by the following technical scheme:
the method comprises the steps of evaluating key technologies of the engine based on fuel economy, wherein the evaluation method is used for determining the sensitivity of the key technologies to the fuel economy of the engine, influence weight and interaction among the key technologies; the evaluation method comprises the following steps:
establishing and calibrating a simulation model of the working process of the engine;
determining and setting key technical parameters;
and (3) calculating a simulation model: adopting an engine working process simulation model to simulate and calculate the fuel consumption rate of the engine when each key technical parameter changes and other key technical parameters are not changed;
determining a regression equation of each key technical parameter about fuel economy;
determining a sensitivity function of each key technical parameter according to the regression equation;
determining the sensitivity of each key technical parameter according to the sensitivity function;
orthogonal combination design of key technology;
determining the influence weight of the key technology through range analysis;
the interaction of the key technology is determined by range analysis.
Further, the establishment and calibration of the engine working process simulation model specifically comprises the following steps: building modules of all parts of the engine according to structural parameters of the engine, and building a combustion mathematical model, a heat transfer mathematical model, a fluid flow mathematical model and a friction mathematical model; and then calibrating the simulation model according to the engine test data to ensure that the relative error between the calculation result and the test result of the simulation model is less than 5 percent.
Further, the determination and setting of the key technical parameters specifically include: determining 5 key technical parameters including the Miller degree of the Miller cycle technology, the air inlet timing and the air outlet timing of the variable valve timing technology, the EGR rate of the exhaust gas recirculation technology and the compression ratio of the high compression ratio technology;
the setting of the key technical parameters comprises the following steps: setting a value range, a step length and a reference value for each key technical parameter.
Further, the calculation of the simulation model specifically includes: and respectively calculating the fuel consumption rate of the engine when a single key technical parameter changes in a value range and other key technical parameters are not changed by using the calibrated engine working process simulation model.
Further, the determining a regression equation of the key technical parameters with respect to the fuel economy is specifically as follows: extracting the corresponding engine fuel consumption rate when each key technical parameter changes according to the simulation calculation result of the calculation step of the simulation model, and fitting the engine fuel consumption rate corresponding to each key technical parameter by a quadratic regression method to obtain a regression equation of each key technical parameter about fuel economy:
Ybe=a0+a1Xi+a2Xi2,Ai≤Xi≤Bi,i=1,2,3,4,5
wherein, YbeThe engine fuel consumption rate is represented, and i is 1,2,3,4 and 5, and the key technical parameters of the Miller degree, the air inlet timing, the exhaust timing, the EGR rate and the high compression ratio are represented respectively; xi represents the value of the ith key technical parameter; a. thei、BiRespectively representing the value lower limit and the value upper limit of the ith key technical parameter; a is0a1a2Is the coefficient of each item.
Further, the determining a sensitivity function of the key technical parameter according to the regression equation specifically includes: for each key technical parameter, the relative variation of the fuel consumption rate is divided by the relative variation of the key technical parameter to obtain the sensitivity function of each key technical parameter:
wherein S isi(xi) A sensitivity function representing the ith key technical parameter.
Further, the determining the sensitivity of the key technical parameter according to the sensitivity function specifically includes: respectively substituting the reference values of all the key technical parameters into respective sensitivity functions Si(xi) Obtaining the sensitivity value S of each key technical parameteri*(xi)。
Further, the orthogonal combination design of the key technology specifically includes: four key technologies are as follows: the Miller cycle technology, the variable valve timing technology, the exhaust gas recirculation technology and the high compression ratio technology are used as four influencing factors, each factor adopts or does not adopt two levels, an orthogonal combination design method is utilized, the fuel consumption rate is used as an assessment index, and the orthogonal combination design of interaction is considered at the four factors and the two levels.
Further, the determining the influence weight of the key technology through range analysis specifically includes: and (3) performing range analysis on orthogonal design results of key technical factor lists in orthogonal combination design by taking the fuel consumption rate as an assessment index to obtain a range value of each key technology, and dividing the range value of each key technology by the range values of all key technologies to obtain the influence weight of the key technologies.
Further, the determining of the interaction of the key technology through range analysis specifically includes: and (3) performing range analysis on the orthogonal design result of the interaction factor column in the orthogonal combination design by taking the fuel consumption rate as an assessment index to obtain a range value of the interaction, which represents the interaction size of the key technology.
The invention has the advantages and positive effects that:
the fuel economy-based engine key technology evaluation method provided by the invention can evaluate the influence of the key technology on the fuel economy of the engine, and can better guide the selection and application of the key technology in the development of the engine. In addition, when the key technology is selected and applied, the method provided by the invention can greatly reduce the economic cost and the time cost, and can quickly and better match the key technology according to the evaluation result.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
On the contrary, the invention is intended to cover alternatives, modifications, equivalents and alternatives which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, certain specific details are set forth in order to provide a better understanding of the present invention. It will be apparent to one skilled in the art that the present invention may be practiced without these specific details.
The engine key technology evaluation method based on fuel economy is obtained based on simulation calculation, sensitivity analysis and orthogonal combination design, and can better guide selection and matching of key machines during engine development. The general idea of the evaluation method of the embodiment of the invention is as follows: firstly, establishing an engine working process simulation model; then, calibrating the simulation model according to the test data, so that the error between the calculated value of the simulation model and the test value is less than 5 percent, and ensuring the accuracy and reliability of the simulation model; then determining relevant technical parameters of the key technology and setting the relevant technical parameters in the model; obtaining the corresponding engine fuel consumption rate when each key technical parameter changes independently through simulation calculation of the model, and determining a regression equation of the key technical parameters about fuel economy through a quadratic regression method; obtaining a sensitivity function of the key technical parameter through a regression equation, and substituting the reference value of the key technical parameter into the sensitivity function to obtain the sensitivity value of the key technical parameter; and then, taking the fuel economy as an assessment index, taking the key technology as an influence factor, carrying out four-factor two-level consideration interaction orthogonal combination design, and finally carrying out range analysis on an orthogonal design result to obtain the influence weight and the interaction of the key technology.
As shown in FIG. 1, the evaluation method for the key technology of the engine based on the fuel economy provided by the embodiment of the invention comprises the following steps:
s1: establishing and calibrating a simulation model of the working process of the engine: building modules of all parts of the engine according to structural parameters of the engine, and building a combustion mathematical model, a heat transfer mathematical model, a fluid flow mathematical model and a friction mathematical model; and then calibrating the simulation model according to the engine test data to ensure that the relative error between the calculation result and the test result of the simulation model is less than 5 percent.
Preferably, the engine working process simulation model is established and calibrated by using GT-POWER software; and when the calibration is carried out, the relative error between the calculated value and the test value, including the in-cylinder pressure, the exhaust temperature, the exhaust pressure, the power, the torque and the fuel consumption rate, is less than 5 percent, so as to obtain the calibrated engine working process simulation model. And obtaining the engine working process simulation model with higher reliability and accuracy.
S2: determining and setting key technical parameters: determining 5 key technical parameters including the Miller degree of the Miller cycle technology, the air inlet timing and the air outlet timing of the variable valve timing technology, the EGR rate of the exhaust gas recirculation technology and the compression ratio of the high compression ratio technology;
and the key technical parameters are set by determining the reference value X of the key technical parameters according to the characteristics of the key technical parameters0And a value range Ai≤Xi≤BiAnd the step size Δ, X of variationiA value representing the ith key technical parameter;
s3: and (3) calculating a simulation model: and respectively calculating the fuel consumption rate of the engine when a single key technical parameter changes in a value range and other key technical parameters are not changed by using the calibrated engine working process simulation model.
S4: determining a regression equation of each key technical parameter about fuel economy: extracting the corresponding engine fuel consumption rate when each key technical parameter changes according to the simulation calculation result of the calculation step of the simulation model, and fitting the engine fuel consumption rate corresponding to each key technical parameter by a quadratic regression method to obtain a regression equation of each key technical parameter about fuel economy:
Ybe=a0+a1Xi+a2Xi2,Ai≤Xi≤Bi,i=1,2,3,4,5
wherein, YbeRepresenting the fuel consumption rate of the engine; i is 1,2,3,4 and 5, which respectively represent 5 key technical parameters of Miller degree, air inlet timing, exhaust timing, EGR rate and high compression ratio; xiA value representing the ith key technical parameter; a. thei、BiRespectively representing the value lower limit and the value upper limit of the ith key technical parameter; a is0a1a2Is the coefficient of each item.
S5: determining a sensitivity function of each key technical parameter according to the regression equation: for each key technical parameter, the relative variation of the fuel consumption rate is divided by the relative variation of the key technical parameter to obtain the sensitivity function of each key technical parameter:
wherein S isi(xi) Whether it represents a sensitivity function for the ith key technology parameter.
S6: determining the sensitivity of each key technical parameter according to the sensitivity function: respectively substituting the reference values of all the key technical parameters into respective sensitivity functions Si(xi) Obtaining the sensitivity value S of each key technical parameteri*(xi)。
S7: orthogonal combination design of key technology; four key technologies are as follows: the Miller cycle technology, the variable valve timing technology, the exhaust gas recirculation technology and the high compression ratio technology are used as four influencing factors, each factor adopts or does not adopt two levels, an orthogonal combination design method is utilized, the fuel consumption rate is used as an assessment index, and the orthogonal combination design of interaction is considered at the four factors and the two levels.
S8: determining the influence weight of the key technology through range analysis; and (3) performing range analysis on orthogonal design results of key technical factor lists in orthogonal combination design by taking the fuel consumption rate as an assessment index to obtain a range value of each key technology, and dividing the range value of each key technology by the range values of all key technologies to obtain the influence weight of the key technologies.
S9: the interaction of the key technology is determined by range analysis. And (3) performing range analysis on the orthogonal design result of the interaction factor column in the orthogonal combination design by taking the fuel consumption rate as an assessment index to obtain a range value of the interaction, which represents the interaction size of the key technology.
In the embodiment, a certain 1.2L supercharged gasoline engine is taken as an example, and four key technologies applied to the gasoline engine are evaluated based on fuel economy according to the step flow shown in fig. 1. Establishing an engine working process simulation model by utilizing GT-POWER software and calibrating the simulation model, so that the simulation model has higher reliability and accuracy, and then determining key technical parameters corresponding to a key technology: the Miller degree of the Miller cycle technology, the air inlet timing and the air outlet timing of the variable valve timing technology, the EGR rate of the exhaust gas recirculation technology and the compression ratio of the high compression ratio technology are 5 key technical parameters, and the reference value, the value range and the step length are determined as follows:
| key technical parameter | Reference value | Value range | Step size |
| Degree of Miller X1,° | 10 | 0~70 | 10 |
| Intake timing X2,°CA | 320 | 280~340 | 10 |
| Exhaust timing X3,°CA | 392 | 372~432 | 10 |
| EGR Rate X4,% | 3 | 0~18 | 3 |
| Compression ratio X5 | 10 | 9.5~14 | 0.5 |
Calculating by using a simulation model, changing each key technical parameter respectively during calculation, keeping other parameters as reference values unchanged, obtaining the change condition of the key technical parameter corresponding to the fuel consumption rate when the key technical parameter changes, fitting the calculation result by using a quadratic regression method to obtain a regression equation of the key technical parameter about the fuel economy, determining the sensitivity function of the key technical parameter according to the regression equation, and substituting the reference value of each key technical parameter into the sensitivity function to obtain the sensitivity value of each key technical parameter (as shown in fig. 2).
Orthogonal combination design is carried out, and four key technologies are as follows: the miller cycle technique, the variable valve timing technique, the exhaust gas recirculation technique and the high compression ratio technique are used as four influencing factors, and each factor takes two levels, level 1: without this technique, level 2: by adopting the technology, the orthogonal combination design method is utilized, the fuel economy is taken as an assessment index, four-factor two-level orthogonal design considering interaction is carried out, and the head of an orthogonal meter is as follows:
performing simulation calculation by using an orthogonal table, performing range analysis on an orthogonal design result, firstly analyzing the assessment indexes of the key technology factor column to obtain the range value of each key technology, and dividing the range value of each key technology by the range values of all key technologies to obtain the influence weight of each key technology (as shown in fig. 3). Then, the evaluation indexes of the interaction factor column are subjected to range analysis, and the order of the interaction among the key technologies is obtained as follows: miller cycle and high compression ratio technology > high compression ratio technology and variable valve timing technology > miller cycle technology and exhaust gas recirculation technology > high compression ratio technology and exhaust gas recirculation technology > miller cycle technology and variable valve timing technology > high compression ratio technology and exhaust gas recirculation technology > variable valve timing technology and exhaust gas recirculation technology. Therefore, when the key technologies of the engine are selected based on the fuel economy, the high compression ratio technology and the variable valve timing technology are mainly considered, other key technologies have little influence on the fuel economy, and meanwhile, attention needs to be paid to the interaction among the key technologies.
The engine key technology evaluation method based on the fuel economy can reasonably quantify the influence of the key technology on the fuel economy of the engine, obtain the sensitivity, influence weight and interaction of the key technology on the fuel economy of the engine, better guide the selection of the key technology when the engine is developed, improve the development efficiency of the engine, shorten the development period and save the development cost.
The above description is only for the preferred embodiment of the present invention, and modifications within the spirit and scope of the present invention are within the scope of the appended claims and their equivalents.