JP4802789B2 - Design value optimization method and design value optimization system - Google Patents

Description

  The present invention relates to a design value optimization method and a design value optimization system, and more particularly, a design value optimization method and design value suitable for optimizing a design value of an internal combustion engine using CFD (Computation Fluid Dynamics). It relates to an optimization system.

  Conventionally, as disclosed in JP-A-2005-249422, a method for predicting the performance of an internal combustion engine using CFD is known. CFD is a simulation method using a physical model that simulates the motion of a working fluid. According to the above conventional performance prediction method, by specifying the specifications of the internal combustion engine, the flow of intake and exhaust can be simulated by CFD. From the result, the internal combustion engine specified by the above specifications Can be predicted.

  The physical model of CFD can be, for example, a one-dimensional model that handles the flow of intake and exhaust as a one-dimensional flow. The model can also be a three-dimensional model that handles the flow of intake and exhaust as a three-dimensional flow. CFD using a one-dimensional model (hereinafter referred to as “one-dimensional CFD”) can be performed with a lighter computational load than CFD using a three-dimensional model (hereinafter referred to as “three-dimensional CFD”). . On the other hand, the three-dimensional CFD is superior to the one-dimensional CFD in simulating the behavior of the working fluid with high accuracy.

  The above-mentioned conventional publication describes that, when predicting the performance of an internal combustion engine, basically, one-dimensional CFD is performed, and three-dimensional CFD is performed only on a portion that requires particularly high accuracy. By switching between the one-dimensional CFD and the three-dimensional CFD in this way, it is possible to predict the performance of the internal combustion engine with sufficient accuracy while avoiding an unduly heavy calculation load. For this reason, the conventional method is useful as a method for accurately predicting the performance of the internal combustion engine whose specifications are specified in a short time.

JP 2005-249422 A JP 2005-249419 A JP 2005-249420 A JP 2004-239130 A

  In designing an internal combustion engine, it is desired to optimize individual design values (for example, intake pipe length). In performing such optimization, it is more efficient to repeatedly perform a performance prediction simulation while changing the design value than to actually test and evaluate an internal combustion engine.

  According to the above-described conventional method, for example, when the intake pipe length is to be optimized, performance prediction in which one-dimensional CFD and three-dimensional CFD are combined is repeatedly executed while gradually changing the intake pipe length. In this case, one simulation itself can be performed in a relatively short time and with high accuracy. However, since many iterations are necessary, as a whole, a great deal of time is required until an optimum design value is obtained. Man-hours are required. In this regard, the above-described conventional method is not necessarily an ideal method in terms of increasing efficiency in the scene where the design value is optimized.

The present invention has been made to solve the above-described problems, and an object thereof is to provide a design value optimization method capable of efficiently optimizing a design value that affects the behavior of a working fluid. And
A second object of the present invention is to provide a design value optimization system that automatically executes the design value optimization method described above.

In order to achieve the above object, the first invention uses a computer resource for low-dimensional CFD computation that simulates the relationship between the design value of the fluid path, the fluid physical quantity, and the rate of change of the fluid physical quantity in a low dimension. performing Te and low-dimensional CFD calculation means, before the relationship between Ki設 meter value and the fluid physical quantity and said rate of change, the high-dimensional CFD operation the computer simulates the high-dimensional high dimension than the low-dimensional A design value optimization method for optimizing the design value using a high-dimensional CFD calculation means executed using hardware resources ,
By allowing the low-dimensional CFD calculation means to execute the low-dimensional CFD calculation over the entire planned range of the design value, the relationship between the previous design value, the fluid physical quantity, and the rate of change is covered in the entire range. A first step of obtaining low dimensional characteristics;
By causing the high-dimensional CFD calculation means to execute the high-dimensional CFD calculation using the initial value of the design value to be attached to the high-dimensional CFD calculation as an input value of the design value , a fluid physical quantity and a change amount with respect to the input value can be obtained. A second step of calculating as a high- dimensional calculation result;
The design values cause a change rate corresponding to the high dimensional calculation result in the low dimensional characteristics, and a third step of determining a pair応値,
Input by adding the identified as the optimum design value design values for the most desirable value Oite the fluid physical quantity in a low-dimensional properties, the difference between the corresponding values with the optimum design value in the latest input value past A fourth step of updating the value;
A fifth step of causing the high-dimensional CFD calculation means to execute the high-dimensional CFD calculation using the updated input value as a design value;
It is characterized by including.

The second invention is the first invention, the third and fourth step is characterized Rukoto cause the computer to execute.

The third invention is the first or second invention, wherein
The fifth step calculates a high-dimensional calculation result similar to the second step,
The fluid physical quantity calculated in the fifth step, the increase rate for the most recent of the fluid physical quantity past calculated before that based on whether below the determination value, either of them, the best value of the fluid physical quantity Including a sixth step of determining whether or not
Until the determination of the best value is affirmed, the high-dimensional calculation result calculated in the fifth step is used in the third step, and the third to sixth steps are repeated. .

Moreover, 4th invention is set in 3rd invention,
If the determination of the previous SL best value is positive, the input values the basis of the larger of the fluid physical quantity calculated in the past recent fluid physical quantity and the fifth step, the optimal of the design value A seventh step of setting a value is included.

  According to a fifth invention, in any one of the first to fourth inventions, the design value is an intake pipe length of the internal combustion engine, and the fluid physical quantity is an in-cylinder inflow air quantity of the internal combustion engine. And

The sixth invention is a design value optimization system,
Low-dimensional CFD calculation means for performing low-dimensional CFD calculation that simulates the relationship between the design value of the fluid path, the fluid physical quantity, and the rate of change of the fluid physical quantity in a low dimension,
A high-dimensional CFD calculation means for performing high-dimensional CFD calculation for simulating the relationship between the design value of the fluid path, the fluid physical quantity, and the rate of change with a high dimension higher than the low dimension;
By allowing the low-dimensional CFD calculation means to execute the low-dimensional CFD calculation over the entire planned range of the design value, the relationship between the previous design value, the fluid physical quantity, and the rate of change is covered in the entire range. Low-dimensional characteristic acquisition means for acquiring low-dimensional characteristics;
By causing the high-dimensional CFD calculation means to execute the high-dimensional CFD calculation using the initial value of the design value to be attached to the high-dimensional CFD calculation as an input value of the design value , a fluid physical quantity and a change amount with respect to the input value can be obtained. High -dimensional calculation result acquisition means for calculating as a high-dimensional calculation result;
The design values cause a change rate corresponding to the high dimensional calculation result in the low dimensional characteristics, and the corresponding value determining means for determining a pair応値,
Input by adding the identified as the optimum design value design values for the most desirable value Oite the fluid physical quantity in a low-dimensional properties, the difference between the corresponding values with the optimum design value in the latest input value past An input value updating means for updating a value;
Update result acquisition means for causing the high-dimensional CFD calculation means to execute the high-dimensional CFD calculation as an updated input value as a design value;
It is characterized by providing.

The seventh invention is the sixth invention, wherein
The update result acquisition unit calculates a high-dimensional calculation result similar to the high-dimensional calculation result acquisition unit,
The update result acquiring means for fluid physical quantity calculated in, based on whether an increase rate for the most recent of the fluid physical quantity past calculated before that falls below the determination value, either of them, the best value of the fluid physical quantity A best value judging means for judging whether or not
Until the determination of the best value is affirmed, the corresponding value determination means, the input value update means, and the update are provided while providing the corresponding value determination means with the high-dimensional calculation result calculated by the update result acquisition means. A repeat instruction means for causing the result acquisition means to repeat the process;
It is characterized by providing.

The eighth invention is the seventh invention, wherein
If the determination of the previous SL best value is positive, the input values the basis of the larger of the fluid physical quantity calculated in the past recent fluid physical quantity and the updated result obtaining means, the optimum of the design value An optimum design value determining means for setting a value is provided.

According to a ninth invention, in any one of the sixth to eighth inventions, the design value is an intake pipe length of the internal combustion engine, and the fluid physical quantity is a cylinder inflow air quantity of the internal combustion engine. And

According to the first , second, or sixth invention, the design value can be optimized by combining the low-dimensional CFD calculation and the high-dimensional CFD calculation. Here, the calculation over the entire range of the design value is performed only for the low-dimensional CFD calculation (first step or low-dimensional characteristic acquisition means). The high-dimensional CFD calculation is first performed only on a predetermined input value (second step or high-dimensional calculation result acquisition means). A design value for obtaining a result corresponding to the high-dimensional calculation result obtained as a result by low-dimensional CFD calculation is determined as a corresponding value (third step or corresponding value determining means). The difference between the corresponding value obtained in this way and the optimum design value in the low-dimensional characteristic is an approximate value of the difference between the optimum design value for deriving the best fluid physical quantity by high-dimensional CFD calculation and the above input value. It becomes. According to the present invention, by updating the input value based on the approximate value, the updated value of the input value can be made a value approximated to the optimum design value for deriving the best value by the high-dimensional CFD calculation. Then, the fluid physical quantity close to the best value can be calculated by performing high-dimensional CFD calculation again with the updated value (fifth step or updated result acquisition means). As described above, according to the present invention, it is possible to obtain a design value sufficiently approximated to the optimum value by performing the high-dimensional CFD calculation only once. Further, only by performing the high-dimensional CFD calculation twice, the fluid physical quantity corresponding to the design value, that is, the evaluation value of the design value can be obtained. For this reason, according to this invention, the design value which influences the behavior of a working fluid can be optimized very efficiently.

Moreover, according to these inventions, in the second step or the high-dimensional calculation result acquisition means,
The change rate of the fluid physical quantity corresponding to the input value is calculated by high-dimensional CFD calculation. And third
In this step or the corresponding value determining means, the corresponding point in the low-dimensional characteristic is determined based on the above change rate. The fluid physical quantity obtained by the high-dimensional CFD calculation and the fluid physical quantity obtained by the low-dimensional CFD calculation show the same increasing / decreasing tendency with respect to the change of the design value. For this reason, if the corresponding value is determined based on the rate of change of the fluid physical quantity as in the present invention, the correspondence between the input value and the corresponding value can be correctly obtained.

According to the third or seventh aspect of the invention, either the fluid physical quantity calculated in the fifth step or the update result acquisition means and the latest fluid physical quantity calculated before that is the best value of the fluid physical quantity. Is determined. If this determination is negative, the corresponding value is determined again, the input value is updated, and the updated input value is based on the high-dimensional calculation result calculated by the fifth step or the update result acquisition means. A high-dimensional CFD operation based on is performed. According to the above processing, the input value can be efficiently brought close to the optimum value, and the arithmetic processing can be terminated when the optimum value is recognized.

According to the fourth or eighth invention, when the fluid physical quantity calculated by the fifth step or the update result acquisition means does not show a large increase with respect to the previous value, the increase of the fluid physical quantity has converged, that is, It is determined that the fluid physical quantity has reached the best value. Of the two fluid physical quantities calculated last, the larger value is the best value, and the input value from which the value is derived is the optimal design value. According to such a method, the design value that produces the best fluid physical quantity can be efficiently identified as the optimum design value.

According to the fifth or ninth invention, it is possible to efficiently specify the intake pipe length of the internal combustion engine that can optimize the characteristics of the in-cylinder inflow air amount of the internal combustion engine.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a block diagram for explaining the configuration of the design value optimization system according to the first embodiment of the present invention. The system of the present embodiment can be realized by installing software for realizing the functions described later in a normal computer system. Each block shown in FIG. 1 schematically represents a functional block realized by a computer system performing processing according to the above-described software.

  As shown in FIG. 1, the system of this embodiment includes an input interface (IF) 10 and an output IF 12. Specifically, the input IF 10 is realized by a keyboard or a mouse. The output IF 12 is realized by a display or a speaker.

  The system includes a one-dimensional (1D) CFD unit 14 and a three-dimensional (3D) CFD unit 16, and a control unit 18 that controls the entire system. Each block mentioned above is comprised so that data communication can be performed mutually.

  The 1DCFD unit 14 includes a one-dimensional physical model that simulates a fluid flow as a one-dimensional flow (a uniform flow in a plane perpendicular to the flow direction). According to the 1DCFD unit 14, by determining various specifications, the behavior of the fluid appearing with respect to the specifications, that is, fluid physical quantities such as flow rate, flow velocity, pressure, etc. are simulated based on a one-dimensional physical model. Can do. For example, in a scene where the 1DCFD unit 14 is used for designing an internal combustion engine, by specifying the specifications of the internal combustion engine, the physical quantities of intake air and exhaust gas obtained under the specifications are simulated according to a one-dimensional physical model. be able to. Hereinafter, this simulation operation is referred to as “1DCFD calculation”.

  The 3DCFD unit 16 includes a three-dimensional physical model that simulates a fluid flow as a three-dimensional flow (a non-uniform flow in a plane perpendicular to the flow direction). According to the 3DCFD unit 16, by defining various specifications, the fluid physical quantity appearing with respect to the specifications can be simulated based on the three-dimensional physical model. For example, in a scene where the 3DCFD unit 16 is used for designing an internal combustion engine, by specifying the specifications of the internal combustion engine, the physical quantities of intake air and exhaust gas obtained under the specifications are simulated according to a three-dimensional physical model. be able to. Hereinafter, this simulation operation is referred to as “3DCFD calculation”.

  In this embodiment, a case where the 1DCFD unit 14 and the 3DCFD unit 16 are used for designing an intake system of an internal combustion engine will be described. Also, here, one of the specifications to be specified (various design values) includes the intake pipe length, and both the 1DCFD calculation and the 3DCFD calculation simulate the in-cylinder inflow air amount. It is assumed that it is set.

[Optimization Method in Embodiment 1]
FIG. 2 is a diagram for explaining the concept of the design value optimization method used in the present embodiment. A curve 20 indicated by a solid line in FIG. 2A indicates the relationship between the intake pipe length obtained by the 1DCFD calculation and the in-cylinder inflow air amount. Hereinafter, this relationship is referred to as “one-dimensional characteristic 20”. Further, a curve 22 indicated by a broken line in FIG. 2A shows the relationship between the intake pipe length obtained by the 3DCFD calculation and the in-cylinder inflow air amount. Hereinafter, this relationship is referred to as “three-dimensional characteristic 22”.

  Specifically, the one-dimensional characteristic 20 is obtained by repeatedly executing the 1DCFD calculation while changing the intake pipe length L over the entire predetermined range, and connecting a large number of in-cylinder inflow air amounts obtained as a result. be able to. Similarly, the three-dimensional characteristic 22 is obtained by repeatedly executing the 3DCFD calculation while changing the intake pipe length L over the entire predetermined range, and connecting a large number of in-cylinder inflow air amounts obtained as a result. be able to.

  Since 1DCFD calculation treats the flow of fluid as a one-dimensional one, it can be performed with a lighter load than 3DCFD. However, the air flow inside the intake pipe is not originally one-dimensional and does not become uniform in a plane perpendicular to the traveling direction. This tendency is particularly noticeable inside a complicated path shaped like an intake port. According to the 3DCFD calculation, the flow in such a complicated path can be simulated with high accuracy, and therefore the in-cylinder inflow air amount can be simulated more accurately than the 1DCFD calculation. The two curves 20 and 22 shown in FIG. 2A are different due to the above-described difference in accuracy.

  In an internal combustion engine, it is desirable that the in-cylinder inflow air amount be as large as possible. According to this viewpoint, the optimum value of the intake pipe length L can be defined as a value having the maximum in-cylinder inflow air amount. Then, such an optimal intake pipe length L can be obtained accurately by obtaining an accurate three-dimensional characteristic 22 and specifying the intake pipe length L that maximizes the in-cylinder inflow air amount in the three-dimensional characteristic 22. Can do.

  However, according to the above method, it is essential to repeatedly execute a 3DCFD operation with a high calculation load many times. For this reason, this method is not necessarily an efficient method for specifying the optimum value of the intake pipe length L.

  The optimization method of the present embodiment is a method for efficiently optimizing the intake pipe length L as compared with the above-described method. Here, first, the 1DCFD calculation with a light load is repeatedly executed over the entire range of the intake pipe length L. By this processing, the one-dimensional characteristic 20 can be obtained (1).

  Next, the initial value of the intake pipe length L3 to be attached to the 3DCFD calculation is set with reference to past experience and the optimum value in the one-dimensional characteristic 22 (2).

  Next, the sensitivity of the evaluation function with respect to the intake pipe length L3 is calculated by 3DCFD calculation. Specifically, first, 3DCFD calculation is performed using the intake pipe length as the L3 initial value, and a point (point 24 in FIG. 2A) corresponding to the L3 initial value on the three-dimensional characteristic 22 is determined. Next, a change rate ΔGa3 (sensitivity) of the in-cylinder inflow air amount (evaluation function) at the point 24 is calculated (3).

  Subsequently, in the one-dimensional characteristic 20, a point where the sensitivity of the evaluation function is the same as the above sensitivity (a point 26 in FIG. 2A) is specified. That is, in the one-dimensional characteristic 20, the point at which the change rate of the in-cylinder inflow air amount becomes ΔGa3 is specified (4).

  Next, as shown in FIG. 2B, the one-dimensional characteristic 20 is translated so that the point 26 specified by the process (4) overlaps the point 24 specified by the process (3). (Five).

  The entire area of the one-dimensional characteristic 20 has already been clarified. For this reason, in the one-dimensional characteristic 20, it is possible to specify the intake pipe length that maximizes the in-cylinder inflow air amount, that is, the optimum value of the intake pipe length in the one-dimensional characteristic 20. In the optimization method of this embodiment, following the process of (5) above, the intake pipe length that is the optimum value in the one-dimensional characteristic 20 after movement is specified, and the value is taken into the intake air to be subjected to the second 3DCFD calculation. The tube length is L3 (updated value) (6).

  The one-dimensional characteristic 20 and the three-dimensional characteristic 22 show similar increase / decrease trends with respect to changes in the intake pipe length. Therefore, the difference ΔL1 generated between the optimum value of the intake pipe length in the one-dimensional characteristic 20 and the intake pipe length corresponding to the point 26 is the intake pipe length that maximizes the in-cylinder inflow air amount in the three-dimensional characteristic 22. It can be handled as an approximate value of the difference occurring between the intake pipe length corresponding to the point 24 (L3 initial value). According to the processing of (6) above, the L3 update value is made sufficiently close to the optimum value of the intake pipe length in the three-dimensional characteristic 22 by setting the value obtained by adding ΔL1 to the L3 initial value as the L3 update value. Can do.

  If the L3 update value is determined by the processing of (6) above, then 3DCFD calculation is performed using that value (7). A point 28 shown in FIG. 2B is a point obtained by the above calculation. FIG. 2B shows a state in which the point 28 is away from the best point in the three-dimensional characteristic 22 to some extent. The in-cylinder inflow air amount Ga3 at the point 28 is sufficiently larger than the in-cylinder inflow air amount Ga3 at the point 24 previously obtained by 3DCFD calculation. The Ga3 increase rate from the previous 3DCFD calculation to the current 3DCFD calculation becomes smaller as Ga3 approaches the maximum value, that is, as the L3 update value that is the basis of the 3DCFD calculation approaches the optimum intake pipe length. For this reason, it is possible to determine whether or not the L3 update value has approached the optimum value of the intake pipe length by paying attention to the increasing rate of the in-cylinder inflow air amount Ga3 from the previous time to this time.

  In the optimization method of the present embodiment, the above determination is made each time 3DCFD calculation is performed based on the L3 update value. As a result, if it can be determined that the L3 update value has not yet been sufficiently optimized, the processing from (3) onward is repeated again.

  Specifically, first, as shown in FIG. 2C, the change rate ΔGa3 at the point 28 is obtained (8). Next, in the one-dimensional characteristic 20, a point 30 having a change rate of ΔGa3 is specified (9). Further, as shown in FIG. 2D, the one-dimensional characteristic 20 is translated so that the point 30 specified by the process (9) overlaps the point 28 specified by the process (8) ( Ten). Then, as in the case of the process (5), the intake pipe length that is the optimum value in the one-dimensional characteristic 20 is set as a new L3 update value (11).

  In the example shown in FIG. 2D, the L3 update value calculated for the second time is a value that generates the maximum in-cylinder inflow air amount Ga3 in the three-dimensional characteristic 22, that is, a value that is sufficiently close to the optimum value of the intake pipe length. It has become. According to the optimization method of the present embodiment, in this case, the L3 update value obtained for the second time is recognized as the optimum value of the intake pipe length, and the optimization process is terminated at that time.

  As described above, in the optimization method of the present embodiment, the calculation over the entire range of the intake pipe length is performed only for the 1DCFD calculation. For the 3DCFD calculation, only a small number of times are executed for the L3 initial value and the L3 update value. On the other hand, according to the method of the present embodiment, the L3 update value can be brought close to the optimum value of the intake pipe length very efficiently by using the tendency of the one-dimensional characteristic 20. For this reason, according to the optimization method of the present embodiment, it is possible to efficiently optimize the intake pipe length without causing an excessive calculation load.

[Outline of processing for realizing the optimization method of the first embodiment]
Next, with reference to FIG. 3, an outline of processing for efficiently performing the above-described optimization method on a computer will be described. Specifically, the design value optimization system shown in FIG. 1 advances the optimization of the intake pipe length according to the procedure described below. In FIG. 3, the same elements as those shown in FIG.

  When the optimization method of the present embodiment is executed on a computer, a predetermined range of the intake pipe length is determined and the range is input to the computer. The computer performs 1DCFD calculation over the entire area, and calculates a one-dimensional characteristic 22 as shown in FIG. 3A (1).

  Further, the intake pipe length L3 that is the initial value of the 3DCFD calculation is input to the computer. The computer receives the input and calculates the in-cylinder inflow air amount Ga3 and the change rate ΔGa3 at the point 24 shown in FIG. 3B (3).

  Next, on the one-dimensional characteristic 20, a point 26 (see FIG. 3C) where the change rate of the in-cylinder inflow air amount becomes ΔGa3 is specified (4). Further, a difference ΔL1 between the intake pipe length L1 at the point 26 and the optimum intake pipe length L1peak in the one-dimensional characteristic 20 is calculated (5 ′). Next, by adding the difference ΔL1 to the L3 initial value, an L3 update value is obtained (6 ′) as shown in FIG.

  The processes (4), (5 ′), and (6 ′) described above may be executed by a computer, or may be executed by a manual process by an operator. The processes (5 ′) and (6 ′) are the processes (5) and (6) described with reference to FIG. 2, that is, the L3 update value is obtained by translating the one-dimensional characteristic 20. It corresponds to processing.

  When the L3 update value is specified, the computer performs 3DCFD calculation using the value (7). As a result, the point 28 shown in FIG. 3D is specified. More specifically, the in-cylinder inflow air amount Ga3 at the point 28 and the change rate ΔGa3 at that point are calculated (7).

  Next, the increase rate of the in-cylinder inflow air amount Ga3 is calculated. Specifically, how much the in-cylinder inflow air amount Ga3 (Ga3 at point 28) calculated this time has increased with respect to the in-cylinder inflow air amount Ga3 (Ga3 at point 24) calculated last time. calculate. If the increase rate is equal to or greater than the determination value ε (for example, an allowable error recognized in the cylinder inflow air amount in the actual machine), Ga3 has not yet converged to the maximum value, that is, the L3 update value is Judge that it has not converged to the optimum design value yet. On the other hand, if the increase rate is below the determination value, it is determined that the L3 update value has converged to the optimum design value. This determination may be executed by a computer or by an operator by manual processing.

  When it is determined that the L3 update value has not converged to the optimum design value, the process shown in FIG. 3E is continued to proceed with further optimization. That is, a point 30 that realizes the rate of change ΔGa3 on the one-dimensional characteristic 20 is specified (9), and a difference ΔL1 from the optimum value on the one-dimensional characteristic 20 is calculated (10 ′).

  Thereafter, as shown in FIG. 3F, a new L3 update value is obtained using the difference ΔL1 (11 ′). When the L3 update value is newly found, the rate of increase of the in-cylinder inflow air amount Ga3 is found for that value. If the increase rate is equal to or greater than the determination value, the process for updating the L3 update value is repeated again. On the other hand, when the increase rate is less than the determination value, the L3 update value obtained in the process (11 ′) is specified as the optimum value of the intake pipe length. According to the above processing, the design value optimization processing in the present embodiment can be easily realized using a computer.

[Specific Processing in System of Embodiment 1]
As described above, the optimization method of the present embodiment can be realized by causing a computer to execute all the processes or by setting some processes to manual processes. The system shown in FIG. 1 implements the optimization method of the present embodiment by a method in which all processing is executed by a computer. Hereinafter, the contents of processing executed by the system shown in FIG. 1 to realize the function will be described.

  FIG. 4 is a flowchart of a routine executed by the system shown in FIG. The routine shown in FIG. 1 is started in a state in which a predetermined range of the intake pipe length and an L3 initial value attached to 3DCFD calculation are input. In this routine, first, in-cylinder inflow air amount Ga1 and its change rate ΔGa1 are calculated by 1DCFD calculation over the entire range of the intake pipe length range (step 100). The result calculated by the processing in this step is stored as a one-dimensional characteristic 20.

  Next, 3DCFD calculation is performed using the L3 initial value (step 102). As a result, the in-cylinder intake air amount Ga3 corresponding to the L3 initial value and the change rate ΔGa3 are calculated.

  Next, based on the one-dimensional characteristic 20 and the change rate ΔGa3, the intake pipe length L1 that causes the same change rate ΔGa1 as the change rate ΔGa3 on the one-dimensional characteristic 20 is specified (step 104).

  Next, the difference ΔL1 = L1peak−L1 between the optimum intake pipe length L1peak in the one-dimensional characteristic 20 and the intake pipe length L1 is calculated (step 106).

  Further, the L3 update value is calculated by adding the difference ΔL1 to the current L3 (step 108).

  Then, the 3DCFD calculation is executed with the newly calculated L3 update value (step 110). As a result, the in-cylinder inflow air amount Ga3 corresponding to the L3 update value and the change rate ΔGa3 are acquired.

  Next, it is determined whether the increase rate of the cylinder inflow air amount Ga3 calculated by the above processing is smaller than the determination value ε (step 112). Specifically, the difference between the latest Ga3 calculated in step 110 and the previously calculated Ga3 is calculated as the increase amount. Then, it is determined whether the increase amount is smaller than ε% of the previous Ga3.

  When it is determined that the increase rate of Ga3 is equal to or greater than the determination value ε by the process of step 112, the calculated value of the in-cylinder inflow air amount Ga3 greatly increases with the update of L3 from the previous time to this time. It can be judged. In this case, it can be determined that Ga3 may still have a large room for increase, that is, there may still be a large room for optimization in the L3 update value. In this case, in order to realize further optimization, the processing after step 104 is executed again.

  On the other hand, when it is determined in step 112 that the increase rate of Ga3 is less than the determination value ε, it can be determined that the calculated value of the in-cylinder inflow air amount Ga3 has already reached the maximum value. In this case, the intake pipe length L3peak that causes the maximum of Ga3 calculated at that time is specified as the optimum value of the intake pipe length (step 114).

  In step 114, more specifically, first, the in-cylinder inflow air amount Ga3 (i) calculated based on the latest L3 update value and the in-cylinder inflow air amount Ga3 (i− 1) is compared. If Ga3 (i) is larger than Ga (i-1), the latest L3 update value is the optimum value. If Ga3 (i) is smaller than Ga (i-1), the previous L3 is optimum. Value.

  The condition of step 112 may be satisfied only when the latest L3 update value has passed the optimal value. Under such circumstances, the L3 used last time may be more suitable as the optimum value than the latest L3 update value. According to the processing in step 114, the optimum value of the intake pipe length can always be appropriately determined including such a case. For this reason, according to the system of the present embodiment, the optimization of the intake pipe length can be realized constantly and efficiently without causing an excessive calculation load.

  In the first embodiment described above, in step 112, Ga3 is the best value based on the rate of increase of the current in-cylinder inflow air amount Ga3 (i) with respect to the previous in-cylinder inflow air amount Ga3 (i-1). However, the determination method is not limited to this. That is, whether or not Ga3 is approaching the best value is determined based on whether or not the change rate ΔGa3 calculated based on the latest l3 update value is a sufficiently small value in step 110. Also good.

  In the first embodiment described above, the intake pipe length that maximizes the in-cylinder inflow air amount is defined as the optimal intake pipe length, and the intake pipe length is optimized, but the application of the present invention is limited to this. It is not limited. For example, the parameter for evaluating the optimum value may be a physical quantity of the fluid, and may be a pressure or a flow rate in addition to the flow rate. Further, the optimization target may be a design value that affects the behavior of the fluid. For an internal combustion engine as an example, the intake pipe diameter, surge tank length, surge tank capacity, exhaust pipe length, exhaust pipe diameter, etc. It is good also as the object.

  In Embodiment 1 described above, the 1DCFD operation and the 3DCFD operation are used in combination, but the present invention is not limited to this. That is, the present invention can be realized by using a combination of a low-dimensional CFD operation and a high-dimensional CFD operation. Therefore, as long as this condition is satisfied, the 1DCFD calculation or the 3DCFD calculation in Embodiment 1 may be replaced with another dimension (for example, two dimensions).

  Further, in the first embodiment described above, the intake pipe length that maximizes the in-cylinder inflow air amount is defined as an optimal design value. Therefore, in step 112, it is determined whether the “increase rate” is smaller than the determination value. Although it is determined to determine whether the result of the 3DCFD calculation has converged around the maximum value, the present invention is not limited to this. That is, when the design value that minimizes the fluid physical quantity is defined as the optimum design value, instead of the above judgment, whether the result of 3DCFD calculation has converged around the minimum value ("decrease rate" is It is appropriate to judge whether it is small.

  In the first embodiment described above, the 1DCFD calculation and the 3DCFD calculation correspond to the “low-dimensional CFD calculation” and the “high-dimensional CFD calculation” in the first or sixth invention, respectively. Further, step 100 is the “first step” in the first invention and “low-dimensional characteristic acquisition means” in the sixth invention, and step 102 is the “second step” in the first invention and the above Steps 104 and 108 are included in the "third step" in the first invention and the "corresponding value determination means" in the sixth invention in the "high-dimensional calculation result acquisition means" in the sixth invention. In the “fourth step” in the first invention and the “input value updating means” in the sixth invention, the step 110 is the “fifth step” in the first invention and the “update” in the sixth invention. It corresponds to “result acquisition means”.

  Further, in the first embodiment described above, the in-cylinder inflow air amount Ga3 and the change rate ΔGa3 calculated in step 102 are the “fluid physical quantity” and “fluid physical quantity change rate” in the second or seventh aspect of the invention. It corresponds.

  In the first embodiment described above, step 112 is not satisfied with the condition of step 112 in the “sixth step” in the third invention and the “best value judging means” in the eighth invention. In this case, the processing for instructing the repetition of the processing after step 104 corresponds to the “repetition instruction means” in the eighth invention.

  In the first embodiment described above, step 114 corresponds to the “seventh step” in the fourth invention and the “optimum design value determining means” in the ninth invention.

It is a block diagram of the design value optimization system of Embodiment 1 of this invention. It is a figure for demonstrating the concept of the design value optimization method used in Embodiment 1 of this invention. In Embodiment 1 of this invention, it is a figure for demonstrating the content of the process which the system shown in FIG. 1 performs. 3 is a flowchart of a routine executed by the system shown in FIG. 1 in Embodiment 1 of the present invention.

Explanation of symbols

10 Input interface 12 Output interface 14 One-dimensional CFD unit (1DCFD unit)
16 3D CFD unit (3DCFD unit)
20 One-dimensional characteristics 22 Three-dimensional characteristics

Claims (9)

A low-dimensional CFD operation means for performing with a design value and a fluid physical quantity and the hardware resources of the fluid physical quantity of the relationship between the change rate simulates the low dimensional low-dimensional CFD operation the computer of the fluid path, before Ki設 meter A high-dimensional CFD calculation means for executing a high-dimensional CFD calculation that simulates a relationship between a value, the fluid physical quantity, and the rate of change using a computer hardware resource that simulates a high-dimensional higher dimension than the low-dimensional A design value optimization method for optimizing the design value using
By allowing the low-dimensional CFD calculation means to execute the low-dimensional CFD calculation over the entire planned range of the design value, the relationship between the previous design value, the fluid physical quantity, and the rate of change is covered in the entire range. A first step of obtaining low dimensional characteristics;
By causing the high-dimensional CFD calculation means to execute the high-dimensional CFD calculation using the initial value of the design value to be attached to the high-dimensional CFD calculation as an input value of the design value , a fluid physical quantity and a change amount with respect to the input value can be obtained. A second step of calculating as a high- dimensional calculation result;
The design values cause a change rate corresponding to the high dimensional calculation result in the low dimensional characteristics, and a third step of determining a pair応値,
Input by adding the identified as the optimum design value design values for the most desirable value Oite the fluid physical quantity in a low-dimensional properties, the difference between the corresponding values with the optimum design value in the latest input value past A fourth step of updating the value;
A fifth step of causing the high-dimensional CFD calculation means to execute the high-dimensional CFD calculation using the updated input value as a design value;
The design value optimization method characterized by including. The design value optimization method according to claim 1, wherein the third and fourth steps are executed by a computer. The fifth step calculates a high-dimensional calculation result similar to the second step,
The fluid physical quantity calculated in the fifth step, the increase rate for the most recent of the fluid physical quantity past calculated before that based on whether below the determination value, either of them, the best value of the fluid physical quantity Including a sixth step of determining whether or not
Until the determination of the best value is affirmed, the high-dimensional calculation result calculated in the fifth step is used in the third step, and the third to sixth steps are repeated. The design value optimization method according to claim 1 or 2. If the determination of the previous SL best value is positive, the input values the basis of the larger of the fluid physical quantity calculated in the past recent fluid physical quantity and the fifth step, the optimal of the design value The design value optimization method according to claim 3, further comprising a seventh step of setting values.   5. The design value optimization method according to claim 1, wherein the design value is an intake pipe length of the internal combustion engine, and the fluid physical quantity is an in-cylinder inflow air amount of the internal combustion engine. Low-dimensional CFD calculation means for performing low-dimensional CFD calculation that simulates the relationship between the design value of the fluid path, the fluid physical quantity, and the rate of change of the fluid physical quantity in a low dimension,
A high-dimensional CFD calculation means for performing high-dimensional CFD calculation for simulating the relationship between the design value of the fluid path, the fluid physical quantity, and the rate of change with a high dimension higher than the low dimension;
By allowing the low-dimensional CFD calculation means to execute the low-dimensional CFD calculation over the entire planned range of the design value, the relationship between the previous design value, the fluid physical quantity, and the rate of change is covered in the entire range. Low-dimensional characteristic acquisition means for acquiring low-dimensional characteristics;
By causing the high-dimensional CFD calculation means to execute the high-dimensional CFD calculation using the initial value of the design value to be attached to the high-dimensional CFD calculation as an input value of the design value , a fluid physical quantity and a change amount with respect to the input value can be obtained. High -dimensional calculation result acquisition means for calculating as a high-dimensional calculation result;
The design values cause a change rate corresponding to the high dimensional calculation result in the low dimensional characteristics, and the corresponding value determining means for determining a pair応値,
Input by adding the identified as the optimum design value design values for the most desirable value Oite the fluid physical quantity in a low-dimensional properties, the difference between the corresponding values with the optimum design value in the latest input value past An input value updating means for updating a value;
Update result acquisition means for causing the high-dimensional CFD calculation means to execute the high-dimensional CFD calculation as an updated input value as a design value;
A design value optimization system characterized by comprising: The update result acquisition unit calculates a high-dimensional calculation result similar to the high-dimensional calculation result acquisition unit,
The update result acquiring means for fluid physical quantity calculated in, based on whether an increase rate for the most recent of the fluid physical quantity past calculated before that falls below the determination value, either of them, the best value of the fluid physical quantity A best value judging means for judging whether or not
Until the determination of the best value is affirmed, the corresponding value determination means, the input value update means, and the update are provided while providing the corresponding value determination means with the high-dimensional calculation result calculated by the update result acquisition means. A repeat instruction means for causing the result acquisition means to repeat the process;
6 Symbol mounting design value optimization system of claim, characterized in that it comprises a. If the determination of the previous SL best value is positive, the input values the basis of the larger of the fluid physical quantity calculated in the past recent fluid physical quantity and the updated result obtaining means, the optimum of the design value 8. The design value optimizing system according to claim 7 , further comprising an optimum design value determining means for setting a value. The design value is the intake pipe length for an internal combustion engine, the fluid physical quantity, design value optimization system of any one of claims 6 to 8, characterized in that a cylinder inflow air quantity of the internal combustion engine.

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