JP2008163900A - Fuel spray simulation method, device and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform highly accurate spray characteristic simulation of taking into consideration a change in an injection speed by time in a fuel injection period and a particle size change by time after injection. <P>SOLUTION: A spray model parameter is optimized by joining calculation data and experiment data together, by making a spray calculation under a constant vessel model by using a computer 1. In the spray calculation, a three-dimensional model is made by reading out a three-dimensional constant vessel model from a CAD database 2 (S1), and an initial condition of the spray model parameter is set (S2), and a time change in a spray arrival distance and a time change in an evaporation quantity and a droplet quantity, are calculated by making a three-dimensional spray calculation (S3). The data are joined together (S4). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel spray simulation method, a fuel spray simulation device, and a fuel spray simulation program.

  In the development of an engine, it has been conventionally performed to analyze the characteristics of a series of processes such as the flow of air sucked into a cylinder, fuel spray, combustion of an air-fuel mixture, and exhaust by computer simulation simulating an experiment. In the case of a direct injection engine that directly injects fuel into the engine cylinder, the spray characteristics of the fuel injected from the injection hole of the fuel injection valve greatly affect the performance of the engine, and the spray characteristics simulation data is Since it is necessary to increase the accuracy of spray characteristic simulation in order to increase the accuracy of combustion simulation performed using fuel, fuel injection is a spray characteristic simulation method that enables high-precision simulation of fuel spray using a computer. Calculate the average particle size based on the height and flow velocity of the fuel film near the nozzle hole outlet of the valve, create a particle size distribution function based on the average particle size, and simulate the fuel spray characteristics based on the function What to do is proposed (for example, refer patent document 1).

  Specifically, this spray characteristic simulation is based on design data in which the shape of the nozzle portion is digitized, and fuel spray injected by gas-liquid two-phase three-dimensional CFD (Computational Flow Dynamics) of fuel at the outlet of the nozzle hole. Estimate the liquid film thickness and flow velocity, calculate the initial average particle size from the calculated liquid film thickness and flow velocity values, and create a particle size distribution function from the calculated initial average particle size. The spray characteristic simulation is performed to calculate the spray characteristic data using the particle size distribution function, and it is easy to estimate the fuel film thickness and flow velocity using the gas-liquid two-phase three-dimensional CFD. At the same time, we are trying to enable highly accurate fuel spray simulation.

  However, in the conventional spray characteristic simulation, it is not possible to perform a highly accurate spray characteristic simulation in consideration of a temporal change in the injection speed during the fuel injection period and a temporal change in the particle size after the injection.

JP 2002-168163 A

  Therefore, it is an object to be able to perform highly accurate spray characteristic simulation in consideration of a temporal change in the injection speed during the fuel injection period and a temporal change in the particle size after the injection.

  The fuel spray simulation method of the present invention is a method for simulating the spray characteristics of fuel injected from the injection hole of the fuel injection valve, and an injection speed calculation step for calculating an injection speed that changes with time during the injection period; A particle size distribution function for calculating the spray characteristics is created based on the fuel particle size calculation step for calculating the fuel particle size that changes with the lapse of time after the start of injection, and the injection velocity calculation data and the fuel particle size calculation data. A particle size distribution function creating step, a spray characteristic simulation step for calculating a spray characteristic of the fuel injected from the nozzle hole of the fuel injection valve based on the injection speed calculation data, the fuel particle size calculation data, and the fuel distribution function; It is what has. According to this method, it is possible to perform highly accurate spray characteristic simulation in which the injection speed during the injection period and the fuel particle size after injection are changed over time.

  In this fuel spray simulation method, the injection speed calculation step may estimate the injection speed based on actual measurement data of the injection amount that changes during the injection period. For example, by actually measuring the fuel injection rate from the start of injection to the end of injection, the actual value of the injection amount (actually measured data) is obtained as the actually measured data, and the change in injection speed with time (changes with time) Value).

  In the fuel particle size calculating step, the average particle size of the fuel is preferably estimated based on injection speed calculation data. For example, the particle size distribution of sprays is large to small, and the distribution (percentage) of the particle size distribution is expressed by a known particle size distribution equation (Nukiyama / Tanazawa equation, Chi-square distribution). , Rosin-Rammler distribution, etc.), and an average particle diameter in which the time change of the average value of the particle diameter (average particle diameter: SMD) is approximately set from the particle size distribution that changes with the change in the injection speed according to the particle size distribution formula (SMD) is estimated.

  In this fuel spray simulation method, in the particle size distribution function creation step, for example, an expected change in injection speed with time and an estimated average particle size (SMD) are used as initial conditions (input variable parameters, spray model parameters) for spray calculation. A known distribution model (Reitz-Diwakar, Pilch-Erdman, Hasiang-Faeth, etc.) is selected to create a viscosity distribution function.

  In this fuel spray simulation method, the spray characteristic simulation step preferably calculates the spray characteristic under a constant container model.

  The spray characteristics simulation is finally performed by simulating a state in which fuel is actually injected into the cylinder of the engine. However, in the actual engine cylinder, there is air flow and piston movement, which is unsteady. Since it is difficult to adjust the spray characteristics to the actual measurement values by simulation because the condition is expected, there is no unsteady factor such as air flow or piston movement before the simulation that is injected into the actual engine. Simulation is performed in a constant container that can simulate the increase in pressure and pressure, and is combined with the experimental data in the same constant container. Thus, the spray characteristics can be simulated without being affected by the intake air flow or the like.

  In addition, the spray characteristic simulation step includes, as spray characteristics, for example, the spray reach distance that changes with the passage of time after the start of injection, the equivalence ratio distribution of the liquid phase and the vapor phase that changes with the passage of time after the start of injection, and the start of injection The amount of droplets and the amount of vapor that change over time are calculated.

  This fuel spray simulation method includes a determination step for determining whether or not the spray characteristic calculated in the spray characteristic simulation step matches the actual spray characteristic, and the spray characteristic calculated in the determination step is the actual spray characteristic. When a deviation occurs, an optimization step for repeatedly performing spray characteristic simulation can be provided.

  In this way, the change in spray speed over time and the average particle size (SMD) so that the actual measurement data and calculation (prediction) of the time change of the spray reach distance (penetration) and the time change of the evaporation amount and the appropriate amount of liquid match. Change the initial condition (input variable parameter) setting of the time change of, calculate and adjust. Thereby, the spray characteristics such as the time change of the spray reach distance, the equivalence ratio distribution of the liquid phase and the vapor phase, the time change of the evaporation amount and the appropriate amount of the liquid can be accurately matched to the actual spray characteristics.

  The measured raw data is obtained as an image. By performing image processing on this, the distribution of the vapor amount and the droplet amount can be analyzed. The image processing technique is known per se.

  Each spray model parameter (injection speed profile, particle size distribution, coefficient of particle size distribution equation, coefficient of splitting model), equivalence ratio distribution of liquid phase and vapor phase, and spray reach distance optimized in the fuel spray simulation with a fixed container in this way Thereafter, spray characteristics simulation (simulation of A / F distribution, etc.) by the engine model is performed using the time variation of the liquid, the appropriate amount of liquid, and the time variation of the steam amount, and then combustion simulation is performed.

  The fuel spray simulation device of the present invention is a device for simulating the spray characteristics of fuel injected from the injection hole of the fuel injection valve, and calculates the injection speed that changes with time during the injection period. A particle size distribution function for calculating the spray characteristics based on the means, the fuel particle size calculating means for calculating the fuel particle size changing with the passage of time after the start of injection, and the injection velocity calculation data and the fuel particle size calculation data. Spray characteristic simulation for calculating the spray characteristics of the fuel injected from the nozzle hole of the fuel injection valve based on the particle size distribution function creating means to be created, the injection speed calculation data, the fuel particle size calculation data, and the fuel distribution function Means. The fuel spray simulation according to the above method is performed by this apparatus.

  Further, the fuel spray simulation program of the present invention is a computer for calculating the injection speed that changes with the passage of time during the injection period in order to simulate the spray characteristics of the fuel injected from the injection hole of the fuel injection valve. Means, a fuel particle size calculating means for calculating a fuel particle size that changes over time after the start of injection, a particle size distribution for calculating spray characteristics based on the injection speed calculation data and the fuel particle size calculation data Based on the particle size distribution function creating means for creating a function, the calculation data of the injection speed, the calculation data of the fuel particle size, and the fuel distribution function, the spray characteristics of the fuel injected from the nozzle hole of the fuel injection valve It is a fuel spray simulation program for making it function as a spray characteristic simulation means to calculate. The fuel spray simulation according to the above method is carried out by this program.

  Thus, according to the present invention, it is possible to perform a highly accurate spray characteristic simulation in which the injection speed during the injection period and the fuel particle size after the injection are changed over time, the time change of the spray arrival distance, the liquid The spray characteristics such as the equivalence ratio distribution of the phase and vapor phase, the evaporation amount, and the time variation of the appropriate amount of liquid can be accurately matched to the actual spray characteristics.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIGS. 1-8 demonstrates an example of embodiment of this invention. 1 is an explanatory diagram of a fuel spray simulation analysis system, FIG. 2 is an explanatory diagram of a constant container model, FIG. 3 is a graph of injection rate actual measurement data, FIG. 4 is a graph of injection speed calculation data, and FIG. FIG. 6 is a comparison graph of actual measurement data and calculation data of spray reach distance, FIG. 7 is a comparison graph of actual measurement data and calculation data of droplet amount and vapor amount, and FIG. 8 is an equivalence ratio of liquid phase and vapor phase. It is a comparison figure of the measurement result of distribution, and a calculation result.

  In this embodiment, as shown in FIG. 1, a fuel spray simulation analysis of a direct injection engine that directly injects fuel into the cylinder of the engine is performed as a preliminary stage of the fuel spray simulation by an engine model in which fuel is injected into the cylinder. In addition, the spray calculation is performed under the constant container model using the computer 1, and the spray model parameters are optimized by combining the calculation data and the experimental data. FIG. 2 shows an example of a constant container model.

  When the spray calculation starts, first, a three-dimensional constant container model is read from the CAD database 2 to create a three-dimensional model (step S1).

  Then, the nozzle hole diameter, the flow rate profile, and the particle size distribution are read from the injector spec database 3 and initial conditions of the spray model parameters are set (step S2).

  Then, the three-dimensional injection calculation (three-dimensional CFD tool) is performed in the following procedure to calculate the time change of the spray arrival distance and the time change of the evaporation amount and the droplet amount (step S3).

  In the three-dimensional injection calculation, first, the fuel injection rate from the start of injection to the end of injection is measured, and an actual value (measured flow rate) of the injection amount is obtained as actual measurement data. FIG. 3 shows an example of actual injection rate measurement data (actual flow rate profile).

  Next, a temporal change in the injection speed is predicted from the actually measured data. FIG. 4 shows an example of injection speed calculation data (injection speed profile).

  Next, select a particle size distribution formula (Nukiyama / Tanazawa method, chi-square distribution, rosin Ramler distribution, etc.) to calculate the particle size distribution, change the coefficient of the fuel distribution equation, and change the injection speed by the particle size distribution equation From the changing particle size distribution, an SMD profile (a graph of the temporal change of the average particle size) in which the time change of the average particle size (SMD) is approximately set is predicted. FIG. 5 shows an example of average particle size prediction data (SMD profile).

  Next, the expected change in injection speed with time and average particle size (SMD) are given as input variable parameters (spray model parameters) for spray calculation, and split models (Reitz-Diwakar, Pilch-Erdman, Hasiang-Faeth, etc.) To create a viscosity distribution function.

  Then, three-dimensional injection calculation (three-dimensional CFD tool) is performed to calculate the time change of the spray arrival distance and the time change of the evaporation amount and the droplet amount.

  Thus, after performing the three-dimensional spray calculation, the measured data and the predicted data (calculated data) are compared, and the equivalence ratio distribution of the liquid phase and the vapor phase, the time variation of the spray arrival distance, the appropriate amount of liquid and the time of the vapor amount If there is a discrepancy between the actual measurement and the calculation, the temporal change in the injection reach distance and the temporal change in the evaporation amount and the appropriate amount of liquid are calculated and calculated (predicted). ) And adjust the initial conditions (input variable parameters) of the temporal change of the injection speed and the average particle size (SMD) to adjust the measurement so that the actual measurement and the calculation match. (Step S4). At that time, the actual measurement data is read from the actual measurement database 4. The measured data of the equivalence ratio distribution of the liquid phase and the vapor phase, the time variation of the spray arrival distance, the liquid proper amount and the time variation of the vapor amount are obtained by image processing of raw data (image). FIG. 6 shows an example of actual measurement data (square plot) and calculation data (solid line) of the spray arrival distance. The time of the spray arrival distance with respect to the time after the end of injection when the fuel injection end timing of the fuel injection valve is 0 ms. Shows history. FIG. 7 shows an example of measured data (triangle plot) and calculated data (dotted line) of the droplet amount, measured data (square plot) and calculated data (solid line) of the vapor amount. The time history of the vapor amount and the droplet amount with respect to the time after the end of injection when the injection end timing is set to 0 ms is shown. The droplet amount shows an increase during the injection period, but shows a decrease after the end of the injection. On the other hand, it is shown that the steam amount increases with the lapse of time after the end of the injection from the injection period. FIG. 8 shows the actual measurement result and calculation result of the equivalence ratio distribution of the liquid phase and the vapor phase.

  When the adjustment is completed, the result database 5 shows the optimized spray model parameters (injection speed and average particle size profile, particle size distribution, particle size distribution coefficient, split model coefficient), liquid phase and vapor phase equivalents. The ratio distribution, the time change of the spray arrival distance, the liquid change amount and the time change of the steam amount are stored, and these data are then subjected to the spray calculation by the engine model (simulation such as A / F distribution), and then the combustion calculation (simulation). Used for.

  The present invention is not limited to the above embodiment, and can be implemented in various other forms.

It is explanatory drawing of the fuel spray simulation analysis system which concerns on embodiment of this invention. It is explanatory drawing of the constant container model in embodiment of this invention. It is a graph of the injection rate actual measurement data in the embodiment of the present invention. It is a graph of the injection speed calculation data in the embodiment of the present invention. It is a graph of the average particle diameter prediction data in the embodiment of the present invention. It is a comparison graph of the actual measurement data and calculation data of the spray reach distance in the embodiment of the present invention. It is a comparison graph of the measurement data and calculation data of the droplet amount and the vapor amount in the embodiment of the present invention. It is a comparison figure of the measurement result and calculation result of the equivalence ratio distribution of the liquid phase in the embodiment of the present invention, and a vapor phase.

Explanation of symbols

1 Computer 2 CAD database 3 Injector spec database 4 Actual measurement database 5 Result database

Claims (8)

A method for simulating the spray characteristics of fuel injected from a nozzle hole of a fuel injection valve,
An injection speed calculating step for calculating an injection speed that changes with time during the injection period;
A fuel particle size calculating step for calculating a fuel particle size that changes over time after the start of injection;
A particle size distribution function creating step for creating a particle size distribution function for calculating spray characteristics based on the calculation data of the injection speed and the calculation data of the fuel particle size;
A fuel spray having a spray characteristic simulation step of calculating a spray characteristic of the fuel injected from the nozzle hole of the fuel injection valve based on the calculation data of the injection speed, the calculation data of the fuel particle size, and the fuel distribution function. Simulation method. The fuel spray simulation method according to claim 1, wherein the injection speed calculation step estimates an injection speed based on actual measurement data of an injection amount that changes during an injection period. The fuel spray simulation method according to claim 1, wherein the fuel particle size calculation step estimates an average particle size of the fuel based on the calculation data of the injection speed. The fuel spray simulation method according to claim 1, wherein the spray characteristic simulation step calculates a spray characteristic under a constant container model. The spray characteristic simulation step includes, as spray characteristics, a spray reach distance that changes with the passage of time after the start of injection, an equivalence ratio distribution of a liquid phase and a vapor phase that changes with the passage of time after the start of injection, and a time after the start of injection. The fuel spray simulation method according to claim 4, wherein a droplet amount and a vapor amount that change with the passage of time are calculated. A determination step of determining whether or not the spray characteristics calculated in the spray characteristics simulation step match the actual spray characteristics;
The fuel spray simulation method according to claim 1, further comprising an optimization step of repeatedly performing the spray characteristic simulation when the calculated spray characteristic deviates from the actual spray characteristic in the determination step. An apparatus for simulating the spray characteristics of fuel injected from a nozzle hole of a fuel injection valve,
An injection speed calculating means for calculating an injection speed that changes with time during the injection period;
A fuel particle size calculating means for calculating a fuel particle size that changes over time after the start of injection;
A particle size distribution function creating means for creating a particle size distribution function for calculating spray characteristics based on the calculation data of the injection speed and the calculation data of the fuel particle size;
A fuel spray provided with spray characteristic simulation means for calculating a spray characteristic of the fuel injected from the injection hole of the fuel injection valve based on the calculation data of the injection speed, the calculation data of the fuel particle size, and the fuel distribution function. Simulation device. A computer to simulate the spray characteristics of the fuel injected from the nozzle of the fuel injection valve,
An injection speed calculating means for calculating an injection speed that changes with time during the injection period;
A fuel particle size calculating means for calculating a fuel particle size that changes over time after the start of injection;
A particle size distribution function creating means for creating a particle size distribution function for calculating spray characteristics based on the calculation data of the injection speed and the calculation data of the fuel particle size;
Based on the calculation data of the injection speed, the calculation data of the fuel particle size, and the fuel distribution function, the function for functioning as a spray characteristic simulation means for calculating the spray characteristic of the fuel injected from the nozzle hole of the fuel injection valve Fuel spray simulation program.

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