CN115859532B - Multi-cylinder engine air inlet molded line design method and multi-cylinder engine - Google Patents
Multi-cylinder engine air inlet molded line design method and multi-cylinder engine Download PDFInfo
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Abstract
The invention belongs to the technical field of engines, and discloses a multi-cylinder engine air inlet molded line design method and a multi-cylinder engine, wherein the multi-cylinder engine air inlet molded line design method comprises the following steps: s1, determining the maximum lift of an intake valve according to an engine structure and the value range of optimization parameters of each intake molded line, and determining the minimum air consumption according to the output torque requirement of the engine; s2, optimizing an air inlet molded line of a cylinder at the farthest end from the air inlet main pipe; optimizing an air inlet molded line of a cylinder at the nearest end of the air inlet main pipe; s3, determining target gas consumption and expected optimized gas inlet molded lines of the nearest cylinder and the farthest cylinder; s4, taking the target gas consumption as an optimization target, and adopting the method for optimizing the air inlet molded lines of the nearest cylinder in the step S2 to respectively optimize the air inlet molded lines of the rest cylinders of the engine. The optimized air inlet molded line of each cylinder is more close to an ideal molded line, and the air consumption consistency of each cylinder and the air inlet mixing uniformity of each cylinder are improved.
Description
Technical Field
The invention relates to the technical field of engines, in particular to a multi-cylinder engine air inlet molded line design method and a multi-cylinder engine.
Background
The gas engine air inlet channel injection technology needs to mix the gas injected into the air channel with fresh air, then mix the gas with EGR circulating waste gas in a mixer, and the mixed gas enters the air cylinders after entering the air inlet manifold of each air cylinder from the air inlet manifold. The equivalent combustion route of the gas engine requires that the mixed gas formed by three gases is uniformly mixed, and the proportion of the gas components is certain. In the prior air inlet system, in order to reduce air consumption, a Miller profile is generally adopted. However, the length of the air-fuel mixture air inlet path and the number of pipe joints of each cylinder of the existing air inlet system are obviously different, so that the air-fuel mixture pressure and the air-fuel mixture uniformity in the air-fuel mixture air inlet manifolds of different cylinders are different. The air inlet cams and the air inlet molded lines of the existing multi-cylinder gas engine are the same, so that the difference of the air consumption of each cylinder and the difference of the ratio of three gas amounts of mixed gas in each cylinder are caused, and the consistency of the combustion state of each cylinder is poor. The equivalent combustion of the gas engine has the knocking problem, the combustion state of each cylinder is inconsistent, the knocking of each cylinder is difficult to control, and the reliability of the engine is reduced. In addition, the intake valve profile affects not only the combustion state but also the gas consumption. The existing intake valve profile is basically symmetrical and is divided into an opening section and a closing section, namely, the lift of the intake valve is gradually increased, and the lift is gradually reduced after reaching the maximum lift at a certain crank angle. In order to avoid collision of the intake valve with the piston, flying off of the intake valve and overlarge contact stress, the opening acceleration of the intake valve is limited, and the closing section of the intake valve needs to control the seating speed of the intake valve. There is a large difference between the existing and ideal profiles, as shown in fig. 1. Therefore, the intake valve has a limited miller degree increasing capability and a limited degree of gas consumption reduction.
Therefore, there is a need for a multi-cylinder engine air intake profile design method and a multi-cylinder engine to solve the above problems.
Disclosure of Invention
The invention aims to provide a multi-cylinder engine air inlet molded line design method and a multi-cylinder engine, so that the optimized air inlet molded line of each cylinder is more similar to an ideal molded line, and the air consumption consistency of each cylinder and the air inlet mixing uniformity of each cylinder are improved.
To achieve the purpose, the invention adopts the following technical scheme:
the design method of the air inlet molded line of the multi-cylinder engine comprises the following steps:
s1, determining the maximum lift of an air inlet valve according to an engine structure and the value range of each air inlet molded line optimization parameter, and determining the minimum air consumption according to the output torque requirement of the engine, wherein each air inlet molded line optimization parameter comprises: intake valve open phase, open segment duration, maximum lift duration, and closed segment duration;
s2, optimizing an air inlet molded line of a cylinder at the farthest end from an air inlet main pipe: the method comprises the steps of taking a lower limit of a duration of an opening section and a lower limit of a duration of a closing section, taking all optimization parameters in a first optimization variable group as optimization variables, taking gas consumption not less than the minimum gas consumption as constraint conditions, taking the minimum gas consumption as an optimization target, and determining an optimized air inlet molded line of a cylinder at the farthest end, wherein the first optimization variable group comprises an opening phase of an air inlet valve and a maximum lift duration;
and (3) optimizing an air inlet molded line of a cylinder at the nearest end of the air inlet manifold: taking the duration lower limit of the closing section, taking all optimization parameters in a second optimization variable group as optimization variables, taking the EGR rate in a first set range and the air-fuel ratio in a second set range, taking the gas consumption not less than the minimum gas consumption as a constraint condition, and taking the minimum gas consumption as an optimization target to determine the air inlet molded line after the optimization of the nearest cylinder, wherein the second optimization variable group comprises an inlet valve opening phase, an opening section duration and a maximum lift duration;
s3, determining target gas consumption and expected optimized gas inlet molded lines of the nearest cylinder and the farthest cylinder: determining the optimized air consumption of the most remote cylinder corresponding to the optimized air intake profile of the most remote cylinder and the optimized air consumption of the most recent cylinder corresponding to the optimized air intake profile of the most recent cylinder, taking the larger air consumption of the most remote cylinder and the most recent cylinder as the target air consumption of each cylinder of the engine, taking the optimized air intake profile corresponding to the larger air consumption as the expected optimized air intake profile of the corresponding cylinder, taking the target air consumption as the optimization target, optimizing the air intake profile of the other cylinder by adopting an air intake profile optimizing method corresponding to the other cylinder in the step S2, and taking the optimized air intake profile as the expected optimized air intake profile of the cylinder;
s4, taking the target gas consumption as an optimization target, adopting the method for optimizing the air inlet molded lines of the nearest cylinder in the step S2 to respectively optimize the air inlet molded lines of other cylinders of the engine, and taking the air inlet molded lines after optimizing the other cylinders as expected optimized air inlet molded lines of the other cylinders.
Preferably, the method further comprises the step S0 before the step S1, and an engine model is built in GT-Power software;
in step S2, with each optimization parameter in the first optimization variable set as an optimization variable, with the gas consumption not less than the minimum gas consumption as a constraint condition, and with the minimum gas consumption as an optimization target, determining the air intake profile after the optimization of the most remote cylinder includes:
establishing a first combination space of an opening phase of an intake valve and a maximum lift duration by a Latin hypercube method, thereby obtaining a first intake molded line combination;
substituting each air inlet molded line in the first air inlet molded line combination into an engine model for calculation, and extracting the corresponding air consumption of the most remote cylinder, so as to establish a first optimized variable group and a first sample space of the corresponding air consumption;
and establishing a mathematical proxy model of the first optimization variable group and the corresponding gas consumption by a neural network method, taking the minimum gas consumption as an optimization target, taking the value range of each optimization variable in the first optimization variable group as a first constraint condition, solving the mathematical proxy model of the first optimization variable group and the corresponding gas consumption by a sequential linear programming method to obtain an optimal solution of the first optimization variable group, and taking an air inlet molded line corresponding to the optimal solution as an air inlet molded line after the optimization of the most-far-end air cylinder.
Preferably, in step S2, with each optimization parameter in the second optimization variable set as an optimization variable, with the EGR rate being in the first set range and the air-fuel ratio being in the second set range, and with the air consumption being not less than the minimum air consumption as a constraint condition, and with the minimum air consumption as an optimization target, determining the most-recent cylinder post-optimization intake profile includes:
establishing a second combination space of an opening phase, an opening section duration and a maximum lift duration of an air inlet valve by a Latin hypercube method, thereby obtaining a second air inlet molded line combination;
substituting each air inlet molded line in the second air inlet molded line combination into an engine model for calculation, extracting the air consumption, the air quantity and the EGR rate of the nearest cylinder, and calculating the air-fuel ratio of the nearest cylinder, so as to establish a second sample space formed by a second optimized variable group, the corresponding EGR rate, the corresponding air consumption and the corresponding air-fuel ratio;
and establishing a mathematical proxy model formed by the second optimization variable group, the corresponding EGR rate, the corresponding gas consumption and the corresponding air-fuel ratio by a neural network method, taking the minimum gas consumption as a target, taking the value ranges of the opening phase of an intake valve, the duration of an opening section and the duration of a maximum lift and the second constraint condition that the EGR rate is in a first setting range and the air-fuel ratio is in a second setting range as a target, solving the mathematical proxy model of the second optimization variable group and the corresponding gas consumption by a sequential linear programming method to obtain an optimal solution of the second optimization variable group, and taking an air inlet molded line corresponding to the optimal solution as an air inlet molded line after the optimization of a nearest cylinder.
Preferably, in step S2, the air intake profile after optimization of the most-recent cylinder is substituted into the engine model to perform calculation, so as to obtain the air consumption corresponding to the air intake profile after optimization of the most-recent cylinder, and the air intake profile after optimization of the most-recent cylinder is substituted into the engine model to perform calculation, so as to obtain the air consumption corresponding to the air intake profile after optimization of the most-recent cylinder.
Preferably, step S4 further includes step S5, verifying and correcting the optimization result: and (3) taking the expected optimized air inlet line of each cylinder of the engine into an engine model for calculation, extracting the air consumption, the air quantity and the EGR rate of each cylinder, judging whether the air consumption root mean square, the air quantity root mean square and the EGR rate root mean square of each cylinder meet the design requirements, if so, determining the expected optimized air inlet line of each cylinder as the final air inlet line of each cylinder, and if not, adopting the method of optimizing the air inlet line of the rest cylinders of the engine in the step S4 to optimize the air inlet line of part of cylinders again to obtain the new expected optimized air inlet line of the part of cylinders, and repeating the steps in the step S5 until the air consumption root mean square, the air quantity root mean square and the EGR rate root mean square of each cylinder meet the design requirements.
Preferably, in step S5, re-optimizing the intake profile of a part of cylinders by using the method for optimizing the intake profile of the rest of cylinders of the engine in step S4 includes:
if the root mean square of the air consumption does not meet the design requirement, adopting the method of optimizing the air inlet molded lines of the rest cylinders of the engine in the step S4 to optimize the air inlet molded lines of the cylinders with the largest absolute value of the difference value between the air consumption and the average value of the air consumption of each cylinder again;
if the root mean square of the air quantity does not meet the design requirement, adopting a method for optimizing the air inlet molded lines of the rest cylinders of the engine in the step S4 to optimize the air inlet molded lines of the cylinders with the largest absolute value of the difference value between the air quantity and the average value of the air quantity of each cylinder again;
if the root mean square of the EGR rate does not meet the design requirement, the method of optimizing the air inlet molded lines of the rest cylinders of the engine in the step S4 is adopted to optimize the air inlet molded lines of the cylinders with the largest absolute values of differences between the EGR rate and the average value of the EGR rates of the cylinders again.
Preferably, step M is further included between step S0 and step S1, and the engine model is calibrated according to the engine bench experimental data.
Preferably, in step S1, the value range of the opening phase of the intake valve is 10 ° CA to 40 ° CA before the exhaust stroke piston reaches the top dead center, the value range of the opening period duration is determined according to the maximum lift of the intake valve by satisfying design requirements with no impact of the intake valve on the piston, no fly-off and contact stress, the value range of the closing period duration is determined by no detachment of the cam from the intake valve and no rebound of the intake valve seating, and the sum of the opening period duration, the maximum lift duration and the closing period duration is smaller than the difference of the intake stroke bottom dead center phase and the opening phase.
Preferably, in step S2, when the intake profile of the most-far-end cylinder is optimized, the intake profile of the other cylinder is consistent with the most-far-end cylinder, and when the intake profile of the most-far-end cylinder is optimized, the intake profile of the other cylinder is consistent with the most-far-end cylinder;
in step S4, when the intake profile of the remaining cylinders of the engine is optimized, the intake profiles of the other cylinders except the optimized cylinder are kept identical to those of the optimized cylinder.
The multi-cylinder engine has cylinders designed by adopting the multi-cylinder engine air inlet molded line design method.
The invention has the beneficial effects that:
according to the design method of the air inlet molded line of the multi-cylinder engine, the opening phase, the opening section duration, the maximum lift duration and the closing section duration of the air inlet valve are optimized while the torque of the engine is ensured, the opening section duration and the closing section duration are shortened as much as possible, the maximum lift duration is improved, and the optimized air inlet molded line of each cylinder is enabled to be closer to an ideal molded line, so that the air consumption of the engine is reduced through the Miller cycle of the engine. And after determining the greater one of the lowest air consumption of the most-far-end air cylinder and the most-far-end air cylinder, taking the air consumption as the target air consumption to optimize the air consumption of other air cylinders, improving the uniformity of the air consumption of each air cylinder, and because the air intake uniformity of the air cylinder which is closer to the air intake manifold is more likely to be insufficient, when optimizing the air consumption of other air cylinders except for the most-far-end air cylinder, adding the duration of the opening section into the second optimized variable group, taking the EGR rate and the air-fuel ratio as constraint conditions, so that the mixing uniformity of the air intake of each air cylinder can meet the requirement, the air intake mixing uniformity of each air cylinder can be ensured while the air consumption uniformity of each air cylinder is improved, the combustion state uniformity of each air cylinder can be effectively improved, and the knocking of each air cylinder can be controlled conveniently.
Drawings
FIG. 1 is a schematic illustration of a prior art profile and an ideal profile provided in the background of the invention;
FIG. 2 is a flow chart of a multi-cylinder engine air intake profile design method provided by an embodiment of the invention;
FIG. 3 is a schematic view of an optimized cylinder air intake profile provided by an embodiment of the present invention;
FIG. 4 is a flow chart of optimizing an intake profile for a cylinder furthest from an intake manifold according to an embodiment of the present invention;
FIG. 5 is a flow chart of optimizing an intake profile for a cylinder closest to an intake manifold according to an embodiment of the present invention;
FIG. 6 is a flow chart for determining a target air consumption and an expected optimal air intake profile for a most proximal cylinder and a most distal cylinder provided by an embodiment of the present invention.
Detailed Description
The invention is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting thereof. It should be further noted that, for convenience of description, only some, but not all of the structures related to the present invention are shown in the drawings.
In the description of the present invention, unless explicitly stated and limited otherwise, the terms "connected," "connected," and "fixed" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
In the present invention, unless expressly stated or limited otherwise, a first feature "above" or "below" a second feature may include both the first and second features being in direct contact, as well as the first and second features not being in direct contact but being in contact with each other through additional features therebetween. Moreover, a first feature being "above," "over" and "on" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature is higher in level than the second feature. The first feature being "under", "below" and "beneath" the second feature includes the first feature being directly under and obliquely below the second feature, or simply means that the first feature is less level than the second feature.
In the description of the present embodiment, the terms "upper", "lower", "right", etc. orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are merely for convenience of description and simplicity of operation, and do not indicate or imply that the apparatus or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the invention. Furthermore, the terms "first," "second," and the like, are used merely for distinguishing between descriptions and not for distinguishing between them.
As shown in fig. 1, the embodiment provides a method for designing an air inlet molded line of a multi-cylinder engine, which includes:
s1, determining the maximum lift of an air inlet valve according to an engine structure and the value range of each air inlet molded line optimization parameter, and determining the minimum air consumption according to the output torque requirement of the engine, wherein each air inlet molded line optimization parameter comprises: the method comprises the steps of opening an intake valve, opening a period duration, a maximum lift duration and a closing period duration, wherein when the valve lift reaches a certain value, a valve flow coefficient is basically unchanged, and a lift value with the maximum valve flow coefficient and the minimum valve lift is selected as the maximum lift of the intake valve;
s2, optimizing an air inlet molded line of a cylinder at the farthest end from an air inlet main pipe: the method comprises the steps of taking a lower limit of a duration of an opening section and a lower limit of a duration of a closing section, taking all optimization parameters in a first optimization variable group as optimization variables, taking gas consumption not less than the minimum gas consumption as constraint conditions, taking the minimum gas consumption as an optimization target, and determining an optimized air inlet molded line of a cylinder at the farthest end, wherein the first optimization variable group comprises an opening phase and a maximum lift of an air inlet valve;
and (3) optimizing an air inlet molded line of a cylinder at the nearest end of the air inlet manifold: taking the duration lower limit of the closing section, taking each optimization parameter in a second optimization variable set as an optimization variable, taking the EGR rate (the ratio of the recirculated exhaust gas amount to the total intake air amount of the sucked cylinder) in a first setting range and the air-fuel ratio in a second setting range, taking the gas consumption amount not less than the lowest gas consumption amount as a constraint condition, and taking the minimum gas consumption amount as an optimization target, and determining the optimized intake line of the nearest cylinder, wherein the second optimization variable set comprises an opening phase of an intake valve, the duration of the opening section and the duration of the maximum lift;
s3, determining target gas consumption and expected optimized gas inlet molded lines of the nearest cylinder and the farthest cylinder: determining the optimized air consumption of the most remote cylinder corresponding to the optimized air intake profile of the most remote cylinder and the optimized air consumption of the most remote cylinder corresponding to the optimized air intake profile of the most remote cylinder, taking the larger air consumption of the most remote cylinder as the target air consumption of each cylinder of the engine, taking the optimized air intake profile corresponding to the larger air consumption as the expected optimized air intake profile of the corresponding cylinder, taking the target air consumption as an optimization target, optimizing the air intake profile of the other cylinder by adopting an air intake profile optimization method corresponding to the other cylinder in the step S2, taking the optimized air intake profile as the expected optimized air intake profile of the cylinder, for example, if the larger air consumption is the optimized air consumption of the most remote cylinder corresponding to the optimized air intake profile of the most remote cylinder, the target air consumption is the optimized air consumption of the most remote cylinder, the optimized air intake profile of the most remote cylinder at the moment is the expected optimized air intake profile of the most remote cylinder, taking the duration of the lower limit, taking each optimization parameter in the second optimization variable set as an optimization variable, setting the second optimization variable set as the optimal air intake profile of the most cylinder, setting the most air consumption at the most remote air intake profile as the most optimal air intake profile of the most air cylinder, setting the most air intake profile of the most optimal air intake profile of the most air cylinder, and setting the most air consumption at least than the most optimal air intake profile at the most air intake profile of the most end;
s4, taking the target gas consumption as an optimization target, adopting the method for optimizing the air inlet molded lines of the nearest cylinder in the step S2 to respectively optimize the air inlet molded lines of other cylinders (except the nearest cylinder and the farthest cylinder) of the engine, and taking the air inlet molded lines of the other cylinders after optimization as expected optimized air inlet molded lines of the other cylinders. The method for optimizing the air inlet profile of the nearest cylinder in the step S2 is adopted to optimize the air inlet profile of the rest cylinders of the engine respectively, namely, the method comprises the following steps of: and taking the duration lower limit of the closing section, taking each optimization parameter in the second optimization variable group as an optimization variable, taking the EGR rate in a first setting range and the air-fuel ratio in a second setting range as a constraint condition, taking the gas consumption not less than the minimum gas consumption as an optimization target, and determining the air inlet molded lines of the other cylinders after optimization.
According to the multi-cylinder engine air inlet molded line design method, engine torque is ensured, and simultaneously, the opening phase, the opening period duration, the maximum lift period duration and the closing period duration of the air inlet valve are optimized, so that the opening period duration and the closing period duration are shortened as much as possible, the maximum lift period is improved, and the optimized air inlet molded line of each cylinder is more close to an ideal molded line, so that the air consumption of the engine is reduced through the Miller cycle of the engine. And after determining the greater one of the lowest air consumption of the most-far-end air cylinder and the most-far-end air cylinder, taking the air consumption as the target air consumption to optimize the air consumption of other air cylinders, improving the uniformity of the air consumption of each air cylinder, and because the air intake uniformity of the air cylinder which is closer to the air intake main pipe is possibly insufficient is more likely to be insufficient, when optimizing the air consumption of other air cylinders except for the most-far-end air cylinder, adding the duration of the opening section into the second optimized variable group, taking the EGR rate and the air-fuel ratio as constraint conditions, ensuring the mixing uniformity of the air intake of each air cylinder while improving the air consumption uniformity of each air cylinder, effectively improving the combustion state uniformity of each air cylinder, and being convenient for controlling knocking of each air cylinder. The optimized air inlet profile of a certain cylinder is shown in fig. 3.
In this embodiment, the cylinders having the same distance from the intake manifold are used as a group, and the group of cylinders are together optimized for the intake profile, that is, the most-recent cylinder is the group of cylinders closest to the intake manifold, and for an engine in which two cylinders are symmetrically arranged, each group of cylinders includes two cylinders.
Optionally, step S0 is further included before step S1, and an engine model is built in GT-Power software. Various operation parameters of the engine under various air inlet molded lines, including air consumption, EGR rate, air quantity and the like, can be determined through engine model simulation, and compared with the bench experiment of producing a large number of engines with different molded lines, the design period and design cost are greatly reduced by establishing an engine model in GT-Power software for simulation calculation. The engine model comprises structures such as a supercharger, an intercooler, a cylinder, a crankcase, an air inlet and outlet main pipe, a connecting pipe system and other input parameters such as the actual air inlet and outlet molded lines of the existing engine cylinder.
Further, step M is further included between step S0 and step S1, the engine model is calibrated according to the experimental data of the engine bench, simulation verification is carried out on the engine model, the pressure wave rule and the temperature of an air inlet manifold of the engine model and the pressure wave rule and the temperature of an air inlet manifold of each cylinder are consistent with the experimental values, and the consistent judgment standard is that the root mean square error is lower than 0.05.
Optionally, in step S2, when the intake profile of the most-far-end cylinder is optimized, the intake profile of the other cylinders is consistent with the most-far-end cylinder, and when the intake profile of the most-far-end cylinder is optimized, the intake profile of the other cylinders is consistent with the most-far-end cylinder; in step S4, when the intake profile of the remaining cylinders of the engine is optimized, the intake profiles of the other cylinders except the optimized cylinder are kept identical to those of the optimized cylinder. In other embodiments, when the air intake profile of a cylinder is optimized, the optimized cylinder may use the air intake profile of the cylinder after optimization, and the non-optimized cylinder may use the actual air intake profile of the engine cylinder, that is, the air intake profile of the engine cylinder which is not optimized.
Optionally, as shown in fig. 4, in step S2, with each optimization parameter in the first optimization variable set as an optimization variable, with the gas consumption not less than the minimum gas consumption as a constraint condition, and with the gas consumption minimum as an optimization target, determining the intake profile after the optimization of the most remote cylinder includes:
the method comprises the steps that a first combination space of an opening phase of an air inlet valve and a maximum lift duration is established through a Latin hypercube method, so that a first air inlet molded line combination is obtained, the Latin hypercube method is a common sampling method in the field, and the specific process of sampling the opening phase of the air inlet valve and the maximum lift duration to establish the first combination space of the opening phase of the air inlet valve and the maximum lift duration is not repeated here;
substituting each air inlet molded line in the first air inlet molded line combination into an engine model for calculation, and extracting the corresponding air consumption of the most remote cylinder, so as to establish a first optimized variable group and a first sample space of the corresponding air consumption;
the method comprises the steps of establishing a mathematical proxy model of a first optimization variable group and corresponding gas consumption by a neural network method, taking the minimum gas consumption as an optimization target, taking the value range of each optimization variable in the first optimization variable group as a first constraint condition, solving the mathematical proxy model of the first optimization variable group and the corresponding gas consumption by a sequential linear programming method to obtain an optimal solution of the first optimization variable group, taking an air inlet molded line corresponding to the optimal solution as an air inlet molded line after the most remote cylinder is optimized, and establishing a mathematical proxy model of an independent variable and a dependent variable by the neural network method as a conventional technical means in the field, wherein the specific process is not repeated, and the independent variable is an air inlet molded line optimization parameter and the dependent variable is the minimum gas consumption.
Optionally, as shown in fig. 5, in step S2, with each optimization parameter in the second optimization variable set as an optimization variable, with the EGR rate being in the first set range and the air-fuel ratio being in the second set range, and with the air consumption not less than the minimum air consumption as a constraint condition, and with the minimum air consumption as an optimization target, determining the most-recent cylinder post-optimization intake profile includes:
establishing a second combination space of the opening phase of the air inlet valve, the duration of the opening section and the duration of the maximum lift by a Latin hypercube method so as to obtain a second air inlet molded line combination, wherein the Latin hypercube method is a common sampling method in the field, and the specific process of sampling the opening phase of the air inlet valve, the duration of the opening section and the duration of the maximum lift to establish the second combination space of the opening phase of the air inlet valve, the duration of the opening section and the duration of the maximum lift is not repeated here;
substituting each air inlet molded line in the second air inlet molded line combination into an engine model for calculation, extracting the air consumption, the air quantity and the EGR rate of the nearest cylinder, and calculating the air-fuel ratio of the nearest cylinder, so as to establish a second sample space formed by a second optimized variable group, the corresponding EGR rate, the corresponding air consumption and the corresponding air-fuel ratio;
the mathematical proxy model formed by the second optimization variable group and the corresponding EGR rate, the corresponding air consumption and the corresponding air-fuel ratio is established through a neural network method, the minimum air consumption is taken as a target, the value range of the opening phase of the intake valve, the duration of the opening section and the duration of the maximum lift and the EGR rate and the air-fuel ratio are in required values as second constraint conditions, the mathematical proxy model of the second optimization variable group and the corresponding air consumption is solved through a sequential linear programming method, the optimal solution of the second optimization variable group is obtained, the air inlet molded line corresponding to the optimal solution is taken as the air inlet molded line after the most-recently-end cylinder is optimized, the mathematical proxy model of the independent variable and the dependent variable is established through the neural network method as a conventional technical means in the field, the specific process is not repeated, and in the embodiment, the independent variable is the air inlet molded line optimization parameter, and the dependent variable is the minimum air consumption.
Optionally, in step S1, the value range of the opening phase of the intake valve is 10 ° CA to 40 ° CA before the exhaust stroke piston reaches the top dead center, the value range of the opening period duration is determined according to the maximum lift of the intake valve according to the design requirement that the intake valve does not strike the piston, does not fly off and the contact stress is satisfied, the value range of the closing period duration is determined according to the condition that the cam does not disengage from the intake valve and the intake valve is seated and does not rebound, and the sum of the opening period duration, the maximum lift duration and the closing period duration is smaller than the difference value between the intake stroke bottom dead center phase and the opening phase. It should be noted that there are two factors affecting the duration of the closing section, one is the closing speed of the intake valve, the other is the negative curvature of the seating control area (30 ° CA before closing the intake valve), in order to ensure that the cam is not separated from the valve, the closing speed of the intake valve is maximum, and in order that the intake valve is not rebounded, the negative curvature radius of 30 ° CA before closing the valve cannot be greater than a certain value, that is, the line change trend of the seating control area cannot be slowed down to minimum requirement, the lower limit of the duration of the closing section is the maximum speed of closing the intake valve, and the negative curvature radius of 30 ° CA before closing the valve takes the certain value. When the maximum lift of the intake valve is determined, a lower limit value of the open period duration and a lower limit value of the closed period duration are determined.
Optionally, in step S3, the air intake profile after optimization of the most-recent cylinder is substituted into the engine model to perform calculation, so as to obtain the air consumption corresponding to the air intake profile after optimization of the most-recent cylinder, and the air intake profile after optimization of the most-recent cylinder is substituted into the engine model to perform calculation, so as to obtain the air consumption corresponding to the air intake profile after optimization of the most-recent cylinder.
Optionally, as shown in fig. 2 and fig. 6, step S4 further includes step S5, verification and correction of the optimization result: and (3) taking an expected optimized air inlet line of each cylinder of the engine into an engine model for calculation, extracting air consumption, air quantity and EGR rate of each cylinder, judging whether the air consumption root mean square, the air quantity root mean square and the EGR rate root mean square of each cylinder (including a nearest cylinder and a farthest cylinder) meet design requirements, if so, determining the optimized air inlet line of each cylinder as an expected optimized air inlet line of each cylinder, if not, correcting the optimized result, and carrying out re-optimization on the air inlet line of a part of cylinders by adopting a method for optimizing the air inlet line of the rest cylinders of the engine in the step S4, so as to obtain a new expected optimized air inlet line of the part of cylinders, and repeating the steps in the step S5 until the air consumption root mean square, the air quantity root mean square and the EGR rate root mean square of each cylinder meet the design requirements. The root mean square of gas consumption meets the design requirement, so that the gas consumption consistency of each cylinder can meet the requirement, the root mean square of air quantity and the root mean square of EGR rate meet the design requirement, the mixing uniformity of air intake of each cylinder can meet the requirement, the mixing uniformity of gas consumption and air intake can meet the requirement, and the combustion consistency of each cylinder can meet the design requirement. In the step S4, the method for optimizing the air inlet profile of the rest cylinders of the engine optimizes the air inlet profile of part of cylinders again, namely: and taking the duration lower limit of the closing section, taking each optimization parameter in the second optimization variable group as an optimization variable, taking the EGR rate in a first setting range and the air-fuel ratio in a second setting range as a constraint condition, taking the gas consumption not less than the minimum gas consumption as a constraint condition, taking the target gas consumption as an optimization target, redefining the optimized air inlet molded line of the part of cylinders, and taking the redefined optimized air inlet molded line of the part of cylinders as a new expected optimized air inlet molded line of the part of cylinders. If the root mean square of the air consumption, the root mean square of the air quantity and the root mean square of the EGR rate of each cylinder still cannot meet the design requirement after multiple corrections, or the results of the multiple corrections are the same, the weight of each constraint condition can be modified and then corrected again.
Further, in step S5, re-optimizing the intake profile of a part of cylinders by using the method for optimizing the intake profile of the rest of cylinders of the engine in step S4 includes: if the root mean square of the air consumption does not meet the design requirement, adopting the method of optimizing the air inlet molded lines of the rest cylinders of the engine in the step S4 to optimize the air inlet molded lines of the cylinders with the largest absolute value of the difference value between the air consumption and the average value of the air consumption of each cylinder again; if the root mean square of the air quantity does not meet the design requirement, adopting a method for optimizing the air inlet molded lines of the rest cylinders of the engine in the step S4 to optimize the air inlet molded lines of the cylinders with the largest absolute value of the difference value between the air quantity and the average value of the air quantity of each cylinder again; if the root mean square of the EGR rate does not meet the design requirement, the method of optimizing the air inlet molded lines of the rest cylinders of the engine in the step S4 is adopted to optimize the air inlet molded lines of the cylinders with the largest absolute values of differences between the EGR rate and the average value of the EGR rates of the cylinders again. In other words, in step S5, when the root mean square of air consumption does not meet the design requirement, the method of optimizing the air inlet profile of the rest of the cylinders of the engine in step S4 is adopted to optimize the air inlet profile of the cylinder with the largest difference between the air consumption and the rest of the cylinders of the engine in step S4, and when the root mean square of EGR rate does not meet the design requirement, the method of optimizing the air inlet profile of the rest of the cylinders of the engine in step S4 is adopted to optimize the air inlet profile of the rest of the cylinders of the engine.
The embodiment also provides a multi-cylinder engine, and the cylinders of the multi-cylinder engine are designed by adopting the multi-cylinder engine air inlet molded line design method.
It is to be understood that the above examples of the present invention are provided for clarity of illustration only and are not limiting of the embodiments of the present invention. Various obvious changes, rearrangements and substitutions can be made by those skilled in the art without departing from the scope of the invention. It is not necessary here nor is it exhaustive of all embodiments. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the invention are desired to be protected by the following claims.
Claims (10)
1. The design method of the air inlet molded line of the multi-cylinder engine is characterized by comprising the following steps of:
s1, determining the maximum lift of an air inlet valve according to an engine structure and the value range of each air inlet molded line optimization parameter, and determining the minimum air consumption according to the output torque requirement of the engine, wherein each air inlet molded line optimization parameter comprises: intake valve open phase, open segment duration, maximum lift duration, and closed segment duration;
s2, optimizing an air inlet molded line of a cylinder at the farthest end from an air inlet main pipe: the method comprises the steps of taking a lower limit of a duration of an opening section and a lower limit of a duration of a closing section, taking all optimization parameters in a first optimization variable group as optimization variables, taking gas consumption not less than the minimum gas consumption as constraint conditions, taking the minimum gas consumption as an optimization target, and determining an optimized air inlet molded line of a cylinder at the farthest end, wherein the first optimization variable group comprises an opening phase of an air inlet valve and a maximum lift duration;
and (3) optimizing an air inlet molded line of a cylinder at the nearest end of the air inlet manifold: taking the duration lower limit of the closing section, taking all optimization parameters in a second optimization variable group as optimization variables, taking the EGR rate in a first set range and the air-fuel ratio in a second set range, taking the gas consumption not less than the minimum gas consumption as a constraint condition, and taking the minimum gas consumption as an optimization target to determine the air inlet molded line after the optimization of the nearest cylinder, wherein the second optimization variable group comprises an inlet valve opening phase, an opening section duration and a maximum lift duration;
s3, determining target gas consumption and expected optimized gas inlet molded lines of the nearest cylinder and the farthest cylinder: determining the optimized air consumption of the most remote cylinder corresponding to the optimized air intake profile of the most remote cylinder and the optimized air consumption of the most recent cylinder corresponding to the optimized air intake profile of the most recent cylinder, taking the larger air consumption of the most remote cylinder and the most recent cylinder as the target air consumption of each cylinder of the engine, taking the optimized air intake profile corresponding to the larger air consumption as the expected optimized air intake profile of the corresponding cylinder, taking the target air consumption as the optimization target, optimizing the air intake profile of the other cylinder by adopting an air intake profile optimizing method corresponding to the other cylinder in the step S2, and taking the optimized air intake profile as the expected optimized air intake profile of the cylinder;
s4, taking the target gas consumption as an optimization target, adopting the method for optimizing the air inlet molded lines of the nearest cylinder in the step S2 to respectively optimize the air inlet molded lines of other cylinders of the engine, and taking the air inlet molded lines after optimizing the other cylinders as expected optimized air inlet molded lines of the other cylinders.
2. The multi-cylinder engine air inlet molded line design method according to claim 1, wherein the method further comprises the step of S0, wherein an engine model is built in GT-Power software before the step of S1;
in step S2, with each optimization parameter in the first optimization variable set as an optimization variable, with the gas consumption not less than the minimum gas consumption as a constraint condition, and with the minimum gas consumption as an optimization target, determining the air intake profile after the optimization of the most remote cylinder includes:
establishing a first combination space of an opening phase of an intake valve and a maximum lift duration by a Latin hypercube method, thereby obtaining a first intake molded line combination;
substituting each air inlet molded line in the first air inlet molded line combination into an engine model for calculation, and extracting the corresponding air consumption of the most remote cylinder, so as to establish a first optimized variable group and a first sample space of the corresponding air consumption;
and establishing a mathematical proxy model of the first optimization variable group and the corresponding gas consumption by a neural network method, taking the minimum gas consumption as an optimization target, taking the value range of each optimization variable in the first optimization variable group as a first constraint condition, solving the mathematical proxy model of the first optimization variable group and the corresponding gas consumption by a sequential linear programming method to obtain an optimal solution of the first optimization variable group, and taking an air inlet molded line corresponding to the optimal solution as an air inlet molded line after the optimization of the most-far-end air cylinder.
3. The intake profile design method of a multi-cylinder engine according to claim 2, wherein in step S2, with each optimization parameter in the second optimization variable set as an optimization variable, with the EGR rate in the first setting range and the air-fuel ratio in the second setting range, and with the gas consumption amount not less than the minimum gas consumption amount as a constraint condition, and with the minimum gas consumption amount as an optimization target, determining the most-recent cylinder post-optimization intake profile includes:
establishing a second combination space of an opening phase, an opening section duration and a maximum lift duration of an air inlet valve by a Latin hypercube method, thereby obtaining a second air inlet molded line combination;
substituting each air inlet molded line in the second air inlet molded line combination into an engine model for calculation, extracting the air consumption, the air quantity and the EGR rate of the nearest cylinder, and calculating the air-fuel ratio of the nearest cylinder, so as to establish a second sample space formed by a second optimized variable group, the corresponding EGR rate, the corresponding air consumption and the corresponding air-fuel ratio;
and establishing a mathematical proxy model formed by the second optimization variable group, the corresponding EGR rate, the corresponding gas consumption and the corresponding air-fuel ratio by a neural network method, taking the minimum gas consumption as a target, taking the value ranges of the opening phase of an intake valve, the duration of an opening section and the duration of a maximum lift and the second constraint condition that the EGR rate is in a first setting range and the air-fuel ratio is in a second setting range as a target, solving the mathematical proxy model of the second optimization variable group and the corresponding gas consumption by a sequential linear programming method to obtain an optimal solution of the second optimization variable group, and taking an air inlet molded line corresponding to the optimal solution as an air inlet molded line after the optimization of a nearest cylinder.
4. The method for designing an intake profile of a multi-cylinder engine according to claim 3, wherein in step S3, the intake profile after optimization of the most-recent cylinder is substituted into the engine model to calculate, so as to obtain the air consumption corresponding to the intake profile after optimization of the most-recent cylinder, and the intake profile after optimization of the most-recent cylinder is substituted into the engine model to calculate, so as to obtain the air consumption corresponding to the intake profile after optimization of the most-recent cylinder.
5. The method for designing the air inlet molded line of the multi-cylinder engine according to claim 2, wherein the method further comprises the following step S5, verification and correction of an optimization result: and (3) taking the expected optimized air inlet line of each cylinder of the engine into an engine model for calculation, extracting the air consumption, the air quantity and the EGR rate of each cylinder, judging whether the air consumption root mean square, the air quantity root mean square and the EGR rate root mean square of each cylinder meet the design requirements, if so, determining the expected optimized air inlet line of each cylinder as the final air inlet line of each cylinder, and if not, adopting the method of optimizing the air inlet line of the rest cylinders of the engine in the step S4 to optimize the air inlet line of part of cylinders again to obtain the new expected optimized air inlet line of the part of cylinders, and repeating the steps in the step S5 until the air consumption root mean square, the air quantity root mean square and the EGR rate root mean square of each cylinder meet the design requirements.
6. The method for designing the air intake profile of the multi-cylinder engine according to claim 5, wherein the step S5 of re-optimizing the air intake profile of the part of the cylinders by using the method for optimizing the air intake profile of the rest of the cylinders of the engine in the step S4 comprises the steps of:
if the root mean square of the air consumption does not meet the design requirement, adopting the method of optimizing the air inlet molded lines of the rest cylinders of the engine in the step S4 to optimize the air inlet molded lines of the cylinders with the largest absolute value of the difference value between the air consumption and the average value of the air consumption of each cylinder again;
if the root mean square of the air quantity does not meet the design requirement, adopting a method for optimizing the air inlet molded lines of the rest cylinders of the engine in the step S4 to optimize the air inlet molded lines of the cylinders with the largest absolute value of the difference value between the air quantity and the average value of the air quantity of each cylinder again;
if the root mean square of the EGR rate does not meet the design requirement, the method of optimizing the air inlet molded lines of the rest cylinders of the engine in the step S4 is adopted to optimize the air inlet molded lines of the cylinders with the largest absolute values of differences between the EGR rate and the average value of the EGR rates of the cylinders again.
7. The multi-cylinder engine air inlet molded line design method according to claim 2, wherein the method further comprises a step M between the step S0 and the step S1, and the engine model is calibrated according to engine bench experimental data.
8. The method according to claim 1, wherein in step S1, the intake valve opening phase is within a range of 10 ° CA to 40 ° CA before the exhaust stroke piston reaches the top dead center, the opening period duration is determined in accordance with the maximum lift of the intake valve by the intake valve not striking the piston, not flying off, and the contact stress satisfying the design requirements, the closing period duration is determined in accordance with the cam not disengaging from the intake valve and the intake valve seating not rebounding, and the sum of the opening period duration, the maximum lift duration, and the closing period duration is smaller than the difference of the intake stroke bottom dead center phase and the opening phase.
9. The intake profile design method for a multi-cylinder engine according to claim 1, wherein in step S2, the intake profile of the other cylinder is kept identical to the most-distal cylinder when the most-distal cylinder is subjected to intake profile optimization, and the intake profile of the other cylinder is kept identical to the most-proximal cylinder when the most-proximal cylinder is subjected to intake profile optimization;
in step S4, when the intake profile of the remaining cylinders of the engine is optimized, the intake profiles of the other cylinders except the optimized cylinder are kept identical to those of the optimized cylinder.
10. A multi-cylinder engine, characterized in that its cylinders are designed by the multi-cylinder engine intake profile design method according to any one of claims 1-9.
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| CN102393302A (en) * | 2011-08-02 | 2012-03-28 | 天津大学 | Device and method for measuring difference of molded lines of valves in fully variable valve mechanism |
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| IT201900006862A1 (en) * | 2019-05-15 | 2020-11-15 | Marelli Europe Spa | Method for estimating and controlling the intake efficiency of an internal combustion engine |
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| CN102393302A (en) * | 2011-08-02 | 2012-03-28 | 天津大学 | Device and method for measuring difference of molded lines of valves in fully variable valve mechanism |
| CN109108235A (en) * | 2018-08-15 | 2019-01-01 | 许云东 | A kind of formative method and device for green sand molding |
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