KR102515776B1 - Closed purge system and estimation method of evaporation gas adsorption mass and concentration thereof - Google Patents

Abstract

An airtight purge system according to a preferred embodiment of the present invention, when the boil-off gas of a fuel tank is loaded, a canister having activated carbon in which the boil-off gas is adsorbed and then desorbed, between the canister and the atmospheric rear end of the canister. A fuel tank shut-off valve provided in the fuel tank, and a purge control solid valve provided between the canister and the engine of the vehicle.

Description

Closed purge system and method for predicting the adsorption mass and concentration of evaporative gas thereof

The present invention relates to a method for predicting the adsorption mass and concentration of boil-off gas in a closed purge system.

Plug-in hybrid electric vehicles (PHEVs) and hybrid electric vehicles (HEVs), which have recently been in the spotlight, spend a lot of time using electric energy rather than fuel during driving.

In the case of such a hybrid vehicle, when driving for a long time, the period in which fuel must be stored in a fuel tank is longer than that of a gasoline vehicle. At this time, harmful evaporation gas is generated, and a closed purge system is applied to store and process it.

1 is a schematic block diagram of a conventional hermetic purge system.

Referring to FIG. 1, in the conventional closed purge system 1, a fuel tank isolation valve (FTIV) is located between a fuel tank 10 and a canister 20, and the fuel tank isolation valve When (FTIV) is opened, evaporation gas is loaded into the canister (20).

This conventional closed purge system 1 has the advantage of being able to calculate the loading amount of boil-off gas and control the purge concentration by controlling the opening time of the fuel tank cut-off valve (FTIV) based on factors affecting the amount of evaporation. there is

However, in the conventional closed purge system 1, when the pressure of the fuel tank 10 rises while performing purge control in a vehicle and the fuel tank shut-off valve (FTIV) needs to be opened, a high concentration of evaporation is instantaneously generated. As the gas flows into the engine and the air-fuel ratio becomes rich, the purge control is adversely affected, and in severe cases, the engine operation is stopped.

Republic of Korea Patent Publication No. 2020-0067487

Accordingly, the present invention has been made in view of the above circumstances, and the position of the fuel tank shutoff valve is located at the rear end (atmospheric side) of the vehicle canister, and the fuel tank shutoff valve is opened before purge control to allow boil-off gas to the canister. By performing purge control after loading, the loaded evaporation gas is adsorbed to the activated carbon in the canister and then desorbed and spread so that evaporation gas with a higher concentration than before does not flow into the engine and prevents the adverse effects of purge control. Its purpose is to provide

In addition, using a one-dimensional simulation tool, the loading amount of evaporation gas, the amount of evaporation gas adsorbed to the canister during the loading process, the concentration of the evaporation gas adsorbed during purging and entering the purge control solid valve, and the mass value The purpose of this study is to provide a method for predicting the adsorbed mass and concentration of boil-off gas in a closed purge system that builds boil-off gas concentration models for purge control under various operating conditions by calculating .

In order to achieve the above object, a hermetic purge system according to a preferred embodiment of the present invention includes a canister having activated carbon in which the boil-off gas is adsorbed and then desorbed when the boil-off gas of the fuel tank is loaded; a fuel tank shut-off valve provided between the canister and the rear end of the canister on the atmospheric side; and a purge control solid valve provided between the canister and the engine of the vehicle.

An active purge pump disposed between the canister and the purge control solid valve may be further included.

When the purge control is performed, the fuel tank shutoff valve may be opened to load the boil-off gas into the canister before opening the purge control solid valve.

When the boil-off gas loaded in the canister is adsorbed to and then desorbed from the activated carbon, the purge control solid valve may be opened and the fuel tank shut-off valve may be closed.

In order to achieve the above object, a method for predicting the adsorbed mass and concentration of boil-off gas of a closed purge system according to a preferred embodiment of the present invention includes a canister having activated carbon, a fuel provided between the canister and the atmospheric rear end of the canister. A method for predicting the adsorption mass and concentration of boil-off gas of a closed purge system including a tank shutoff valve and a purge control solid valve provided between the canister and the engine of a vehicle, generating a one-dimensional model in consideration of the closed purge system 1-dimensional model generation step; a chemical reaction model generation step of generating a chemical reaction model in consideration of a chemical reaction between the activated carbon and the boil-off gas loaded into the canister and including it in the one-dimensional model; an adsorption mass calculation step of calculating an adsorption mass of the boil-off gas adsorbed on the activated carbon using the one-dimensional model; and a concentration calculation step of calculating the concentration of the boil-off gas purged through the purge control solid valve using the one-dimensional model.

Further comprising an analysis condition setting step of setting analysis conditions in which the fuel tank shutoff valve is opened and the purge control solid valve is maintained in a closed state for a predetermined time when calculating the adsorbed mass of the boil-off gas in the chemical reaction model. can do.

The analysis condition setting step may include analysis conditions in which the fuel tank cut-off valve is closed and the purge control solid valve is changed from a closed state to an open state after the predetermined time when the concentration of the boil-off gas is calculated in the chemical reaction model. It may include a step of setting.

In the calculating the adsorption mass, the adsorption mass of the boil-off gas may be calculated by extracting adsorption characteristics of the activated carbon from the chemical reaction model and varying the extracted adsorption characteristics.

In the concentration calculation step, the concentration of the boil-off gas may be calculated by extracting desorption characteristics of the activated carbon from the chemical reaction model and varying the extracted desorption characteristics.

A reference value comparison step of comparing the adsorbed mass and concentration of the boil-off gas with a reference value prepared in advance, and determining whether they match the reference value may be further included.

When the adsorbed mass and concentration of the boil-off gas do not match the reference value in the reference value comparison step, a characteristic modification step of modifying adsorption characteristics and desorption characteristics of the activated carbon to approximate the reference value may be further included.

In the reference value comparison step, when the adsorbed mass and concentration of the boil-off gas coincide with the reference value, an analysis end step of completing prediction of the adsorbed mass and concentration of the boil-off gas may be further included.

The one-dimensional model may be generated based on components of the fuel tank storing the boil-off gas, the canister, the canister and the active purge pump, and the purge control solid valve.

The chemical reaction model may be generated by setting the activated carbon as pure carbon particles, setting the boil-off gas as hydrocarbons, and quantifying a chemical reaction between the pure carbon particles and the hydrocarbons using a reaction rate equation.

According to the closed purge system according to a preferred embodiment of the present invention and the method for predicting the adsorbed mass and concentration of boil-off gas thereof, the position of the fuel tank shut-off valve is located at the rear end (atmospheric side) of the vehicle canister, and the purge control By opening the fuel tank shut-off valve before loading the boil-off gas into the canister, purge control is performed so that the loaded boil-off gas is adsorbed to the activated carbon in the canister and then desorbed and spread to prevent higher-concentration boil-off gas from entering the engine. and has the effect of preventing the adverse effects of fuzzy control.

In addition, using a one-dimensional simulation tool, the loading amount of evaporation gas, the amount of evaporation gas adsorbed to the canister during the loading process, the concentration of the evaporation gas adsorbed during purging and entering the purge control solid valve, and the mass value By calculating , there is an effect of constructing a boil-off gas concentration model for purge control in various operating conditions.

1 is a block diagram of a closed purge system according to the prior art.
2 is a block diagram of a closed purge system according to a preferred embodiment of the present invention.
3 is a flow chart of a method for predicting the adsorbed mass and concentration of boil-off gas in a closed purge system according to a preferred embodiment of the present invention.
4 is a view showing a carbon bed of a canister according to a preferred embodiment of the present invention.
5 is an example showing the result of predicting adsorption mass of a closed purge system according to a preferred embodiment of the present invention.
6 is an example showing the result of predicting the boil-off gas concentration of the closed purge system according to a preferred embodiment of the present invention.
7 is another example showing the prediction result of boil-off gas concentration of a closed purge system according to a preferred embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to components of each drawing, it should be noted that the same components have the same numerals as much as possible even if they are displayed on different drawings. In addition, although preferred embodiments of the present invention will be described below, the technical idea of the present invention is not limited or limited thereto and can be modified and implemented in various ways by those skilled in the art.

2 is a block diagram of a closed purge system according to a preferred embodiment of the present invention.

Referring to FIG. 2 , the sealed purge system 100 according to a preferred embodiment of the present invention includes a fuel tank 110, a canister 120, a fuel tank shutoff valve 130, an active purge pump 140, and a purge A control solenoid valve 150 may be included.

In the closed purge system 100 according to a preferred embodiment of the present invention, the position of the fuel tank shutoff valve 110 is located at the rear end (atmospheric side) of the canister 120, and the fuel tank shutoff valve 130 is turned on before purge control. After opening and loading the boil-off gas into the canister 120, purge control is performed so that the loaded boil-off gas is adsorbed to the activated carbon of the canister 120 and then desorbed and spread so that a higher concentration of boil-off gas compared to the prior art is supplied to the engine 200 It is characterized in that it does not flow in and prevents the adverse effects of fuzzy control.

In addition, the closed purge system 100 according to a preferred embodiment of the present invention uses a one-dimensional simulation tool to determine the loading amount of evaporation gas, the amount of evaporation gas adsorbed to the canister 120 during the loading process, and the evaporation adsorbed during purging. It is characterized in that an boil-off gas concentration model for purge control under various operating conditions is built by calculating the concentration and mass value of the gas desorbed and flowing into the fuel tank shutoff valve 130.

Hereinafter, the configuration of the closed purge system 100 according to a preferred embodiment of the present invention will be described.

The fuel tank 110 is a device for storing fuel for driving various hybrid vehicles. The fuel tank 110 may accommodate various fuels such as gasoline and natural gas according to vehicle options.

The fuel tank 110 may include components necessary for generating a one-dimensional model. Here, the one-dimensional model may be for predicting the adsorbed mass and concentration of boil-off gas of the closed purge system 100. Components of the fuel tank 110 may include total volume and mass values.

In addition, components of the fuel tank 110 may include a filling amount of liquid fuel and a contact area with a tank wall according to filling. It can be used to calculate the convective heat transfer of liquid and gaseous (evaporative) fuels.

In addition, components of the fuel tank 110 may include a boundary area between liquid fuel and gaseous fuel. In addition, components of the fuel tank 110 may include initial pressure, temperature, and chemical composition (gasoline fuel value) of liquid fuel and gaseous fuel.

Also, components of the fuel tank 110 may include reid vapor pressure. Reed vapor pressure represents the absolute vapor pressure exerted by the vapor of a liquid and dissolved gases and moisture.

In addition, components of the fuel tank 110 may include a convective heat transfer coefficient between the outer wall of the tank and the atmosphere.

The canister 120 is a device that absorbs and stores boil-off gas from the fuel tank 110 when the engine of the hybrid vehicle is stopped. The canister 120 may communicate with the fuel tank 110 through a separate pipe. The canister 120 may have activated carbon having strong adsorbing power therein. The activated carbon may be a carbon bed, which is an amorphous carbon aggregate formed inside the canister 120 . Activated carbon has fine pores well formed during the activation process and has a large internal surface area.

The canister 120 may include components necessary for generating a one-dimensional model. Components of the canister 120 may include a size of a carbon bed having a front area and a length. This can be confirmed in FIG. 4 . The activated carbon of the canister 120 may have a specific area of 6×(1-void fraction)/D _particle . A solid fraction of the carbon bed may be 0.687.

Also, components of the canister 120 may include a pressure drop according to a flow rate passing through the carbon bed. In the case of a porous material such as a carbon bed, the amount of pressure drop may be expressed through the product of a friction factor (f) and a Reynolds number (Re). This may appear as in Equation 1.

<Equation 1>

In Equation 1, ε represents the void fraction.

In addition, the ratio of convection and conduction heat transfer to the flow passing through the carbon bed is defined as the Nussel number (Nu) and can be expressed as in Equation 2.

<Equation 2>

The fuel tank shutoff valve 130 is a device that blocks evaporation gas from the fuel tank 110 from flowing into the canister 120 . The fuel tank shutoff valve 130 may be located at the rear end (atmospheric side) of the canister 120 . The fuel tank shutoff valve 130 may be opened before purging is performed so that the canister 120 may be loaded with boil-off gas from the fuel tank 110 . At this time, since the evaporation gas loaded in the canister 120 is adsorbed to the activated carbon and then desorbed and spread, there is an effect that high concentration evaporation gas does not occur in the purge control.

The active purge pump 140 may be provided between the canister 120 and the engine 200 . The active purge pump 140 may perform a pumping operation to introduce boil-off gas from the canister 120 into the engine 200 during purge control.

The active purge pump 140 may include components necessary for generating a one-dimensional model. There is a disadvantage in that the engine of an eco-friendly vehicle such as a hybrid vehicle is frequently turned on or off, so that there is not enough time to learn the purge amount compared to conventional internal combustion engine vehicles. The evaporation gas is forcibly purged and at the same time interlocked with the duty amount of the purge control solid valve 150, and a one-dimensional model can be created through learning the purging amount.

A volume flow rate or mass flow rate value over time acquired in a test may be input to the one-dimensional model. At this time, when the one-dimensional model is analyzed, a corresponding flow rate value according to time is formed so that the boil-off gas adsorbed in the fuel tank 110 and the canister 120 flows into the engine 200 via the purge control solenoid valve 150. can do.

The purge control solenoid valve 150 is a valve serving to transfer boil-off gas generated in conjunction with the operation of the active purge pump 140 to the engine 200 side.

The purge control solenoid valve 150 may include components necessary for generating a one-dimensional model. The one-dimensional model may learn the amount of purge flowing into the engine 200 . To this end, the duty value of the purge control solenoid valve 150 may gradually increase or decrease over time.

In the one-dimensional model, when a duty value according to time acquired in a test is input, the corresponding duty value may be converted into an opening area or an orifice diameter of the purge control solenoid valve 150 and reflected therein.

In the above-described purge amount learning, if the concentration value of the current purge gas is known before performing the purge in the actual vehicle, if the concentration is selected as the initial pilot value and then purge control is performed, learning is not performed. Sometimes it is necessary to open the purge valve slowly. In contrast, if the purge control solenoid valve 150 is opened relatively quickly, the purge amount learning time may be reduced.

In this way, when the initial learning for generating the one-dimensional model is successful, the air fuel ratio feedback control may be performed.

In the analysis technology according to a preferred embodiment of the present invention, the main purpose is to find the initial maximum concentration value of boil-off gas to be selected as a pilot value, and the adsorption and desorption characteristics of the canister 120 are identified in order to select the maximum concentration value. It should be.

In other words, in the closed purge system 100 according to a preferred embodiment of the present invention, unlike the prior art, the fuel tank shutoff valve 130 is located at the rear end (atmospheric side) of the canister 120, so that the fuel tank shutoff valve 130 ) is opened, the fuel stored in the fuel tank 110 is introduced into the canister 120 by natural evaporation, and the introduced evaporation gas is adsorbed to the activated carbon in the canister 120. At this time, the active purge pump 140 may be in an inoperative state and the purge control solenoid valve 150 may be in a closed state.

In addition, in the closed purge system 100 according to a preferred embodiment of the present invention, when the fuel tank shutoff valve 130 is closed, the flow to the atmosphere does not occur, so that the boil-off gas in the fuel tank 110 flows through the canister 120. do not enter into.

That is, in the sealed purge system 100 according to a preferred embodiment of the present invention, when the boil-off gas is diffused in the pipe before the fuel tank shutoff valve 130 and the purge control solenoid valve 150, the pressure in the pipe is reduced in the conventional way. Compared to the case where the fuel tank shut-off valve is closed, since it does not rise high, even if the purge control solenoid valve 150 is opened thereafter, high-concentration boil-off gas can be prevented from flowing into the engine 200.

In addition, the hermetic purge system 100 according to a preferred embodiment of the present invention performs forced pumping through the active purge pump 140 when the boil-off gas is purged toward the engine 200 according to the above-described characteristics. At this time, the degree of opening of the purge control solenoid valve 150 varies according to the duty value. there is.

In addition, the closed purge system 100 according to a preferred embodiment of the present invention calculates the adsorption mass and desorption mass of the canister 120 using an analysis method using a one-dimensional simulation tool, and evaporates gas by purge control. It is characterized by calculating the concentration of.

3 is a flow chart of a method for predicting the adsorbed mass and concentration of boil-off gas in a closed purge system according to a preferred embodiment of the present invention.

Referring to FIG. 3, the method for predicting the adsorbed mass and concentration of boil-off gas of the closed purge system according to a preferred embodiment of the present invention includes a one-dimensional model generation step (S310), a chemical reaction model generation step (S320), and analysis condition setting step. (S330), an adsorption mass calculation step (S340), a concentration calculation step (S350), a reference value comparison step (S360), a characteristic correction step (S370), and an analysis termination step (S380) may be included.

In the 1D model generation step ( S310 ), the electronic control unit may generate a 1D model in consideration of the closed fuzzy system 100 . Here, the one-dimensional model may be generated based on components of the fuel tank 110, the canister 120, the fuel tank shutoff valve 130, the active purge pump 140, and the purge control solid valve 150. . Since components of the fuel tank 110, the canister 120, the fuel tank shutoff valve 130, the active purge pump 140, and the purge control solid valve 150 have been described above, detailed descriptions thereof will be omitted.

In the chemical reaction model generating step ( S320 ), the electronic control unit may generate a chemical reaction model of the closed purge system 100 .

Hereinafter, a process of generating a chemical reaction model will be described.

In one embodiment, the chemical reaction process related to the adsorption and desorption of the boil-off gas loaded in the canister 120 assumes that the activated carbon for collecting the gas in the canister 120 is pure carbon particles (element symbol: C), gasoline Hydrocarbons (chemical name: HC) that have adverse effects on air pollution are specified among the boil-off gas components of fuel, and the reaction mechanism between these two materials can be quantified by the reaction rate formula. A chemical reaction process related to the adsorption and desorption of the boil-off gas may be applied to a chemical reaction model.

Hereinafter, a reaction rate applied to a chemical reaction model will be described.

First, the reaction rate between two substances is determined by the concentration and reaction order of the substance according to the known Arrhenius equation. In addition, in a reaction between two materials, a chemical reaction including a forward reaction or a reverse reaction may occur by activation energy, which is the minimum energy required for the reaction, and reaction heat (Q) generated at this time.

Activated carbon in the canister 120 requires forward reaction modeling in which it is adsorbed during loading of the boil-off gas, and modeling of a reverse reaction in which it is desorbed when the boil-off gas is purged.

The total reaction rate (Net Reaction Rate) may be defined as in Equation 3 below.

<Equation 3>

In Equation 3, coverage (θ, coverage) represents the adsorption rate of activated carbon, and C represents the concentration of boil-off gas. Here, the coverage (θ) represents the ratio between the maximum saturation amount of boil-off gas that can be adsorbed on the activated carbon and the actually adsorbed boil-off gas. It can appear as a value of approximately 0 to 1.

In addition, if the reaction process is assumed to be a steady state and an isothermal process, and the pressure is summarized, it can be expressed as Equation 4 below.

<Equation 4>

In Equation 4, r _a represents the reaction rate in the forward direction, and r _d represents the reaction rate in the reverse direction. k represents the overall adsorption characteristics (Overall Rate Multiplier) for both the forward and reverse directions. The des_multi value represents the desorption multiplier during the reverse reaction. Reaction rate and desorption characteristics are characteristic values of activated carbon, and are not values determined through theoretical formulas and can be calculated by testing.

A carbon bed is a porous material having numerous pores therein due to its manufacturing characteristics and purpose. Accordingly, evaporation gas exists only in the pores of the carbon bed and reacts with the activated carbon. At this time, the total reaction rate r value can be calculated by multiplying the value of the void fraction in Equation 4 above. This can be expressed as in Equation 5 below.

<Equation 5>

In the analysis condition setting step (S330), the electronic control unit may set analysis conditions. Here, the analysis conditions may be conditions for predicting the adsorbed mass and concentration of boil-off gas. In order to predict the mass value of the boil-off gas adsorbed on the activated carbon of the canister 120, the reaction rate between the carbon grains of the activated carbon and the boil-off gas must be calculated first. However, the rate multiplier k value presented in the reaction rate calculation formula does not have a constant value due to the production distribution of activated carbon. Accordingly, a process of finding the adsorption characteristic k value of the related reaction rate calculation formula through a separate test is required.

In order to find the adsorption characteristic k value, only the loading process on the system can be considered. In this case, the fuel tank shutoff valve 130 may be always open, and the purge control solid valve 150 may be maintained in a closed state for a predetermined time. The predetermined time may be approximately 500 seconds, but is not limited thereto.

In the adsorbed mass calculation step (S340), the electronic control unit may calculate the adsorbed mass of the evaporation gas adsorbed on the activated carbon of the canister 120 using a chemical reaction model with set analysis conditions. The electronic control unit may extract the adsorption characteristics of the activated carbon from the chemical reaction model and calculate the adsorption mass of the boil-off gas by varying the extracted adsorption characteristics. The electronic control unit may calculate the mass of boil-off gas adsorbed on the activated carbon by applying a value approximately 10 times or 100 times increased and decreased based on the default value of 0.027 for the reaction rate k value in the canister 120. .

In the boil-off gas concentration calculation step (S350), the electronic control unit may calculate the boil-off gas concentration purged to the purge control solid valve according to the purge control. The electronic control unit may calculate the concentration of boil-off gas by extracting the desorption characteristics of the activated carbon from the chemical reaction model and varying the extracted desorption characteristics. First, the electronic control unit may generate a flow rate by driving the active purge pump 140 . The electronic control unit may calculate the concentration value of boil-off gas when the flow rate generated by the active purge pump 140 passes through the purge control solid valve 150 and flows into the engine 200 side. The flow rate generated at this time is evaporation gas desorbed from the activated carbon of the canister 120, and since the concentration value is changed by the above-described desorption characteristics, a process of finding through a separate test is required in the same way as the adsorption characteristics.

In order to find the desorption characteristic value des multi, only a purging process may be considered in the system. At this time, the fuel tank shutoff valve 130 may be in a closed state, and the purge control solid valve 150 may be in an open state.

The desorption process is possible in a state in which a certain amount of evaporation gas is adsorbed to the activated carbon in the canister 120 . The electronic control unit immediately opens the purge control solid valve 150 after being closed for about 500 seconds under analysis conditions for selecting adsorption characteristics, and calculates the concentration of boil-off gas passing through the purge control solid valve 150. At this time, the des multi value may be a concentration value for about 8 cases from 2 to 35 based on 20 presented as a default value. The eight cases may include 2, 5, 10, 15, 20, 25, 30, and 36, but are not limited thereto.

In the reference value comparison step (S360), the electronic control unit may compare the adsorbed mass and concentration of the boil-off gas with a preset reference value to determine whether they match. Here, the reference value may include an adsorption mass value and a concentration value prepared through an actual test process.

The electronic control unit compares the adsorption mass of evaporative gas in the canister 120 according to the change in the adsorption characteristic k value and the adsorption mass value in the actual test to select the k value having the closest mass value to the actual test value. The k value can be set to a unique value of the carbon bed inside the canister applied to the test device.

In addition, the electronic control unit compares the evaporation gas concentration at the rear end of the purge control solenoid valve 150 according to the change in the des_multi value of the desorption characteristic and the evaporation gas concentration in the actual test to des_multi having a concentration value closest to the actual test value. value can be selected. At this time, the selected 'des_multi' value cannot be regarded as a unique value of the internal carbon bed of the canister 120 applied to the test device, unlike the adsorption characteristic k value. This is because, in addition to the BOG desorbed from the activated carbon, BOG introduced from the fuel tank is partially present in the BOG flowing into the purge control solid valve 150.

In the case of the purge concentration ratio, there is a change in the concentration value over time, so there is a problem of when the concentration value at a point in time should be compared with the reference value of the actual test value. It is reasonable to use the maximum concentration value as a criterion like the model of the purge control solid valve 150 described above.

Although there is a change in the adsorption mass with time, the adsorption mass value of the accumulated gas at the completion point of 500 seconds selected in the analysis condition can be compared with the reference value, but the concentration of boil-off gas is not.

In the characteristic correction step (S370), when the adsorbed mass and concentration of the boil-off gas do not match the reference values, the electronic control unit may modify the adsorption characteristics and desorption characteristics of the activated carbon to approximate the reference values. The electronic control unit can apply the adsorption and desorption characteristics of the modified activated carbon to the chemical reaction model.

In the analysis end step (S380), the electronic control unit may complete prediction of the adsorbed mass and concentration of the boil-off gas when the adsorbed mass and concentration of the boil-off gas coincide with the reference values.

5 is an example showing the result of predicting adsorption mass of a closed purge system according to a preferred embodiment of the present invention.

Referring to FIG. 5 , the adsorption mass varies according to the change in the adsorption characteristic value, and the adsorption characteristic value is 0 to -1.29 g, and it can be confirmed that gas adsorption to the activated carbon hardly occurs. On the other hand, as the adsorption characteristic value increases from 0.00027 to 0.27, the adsorption mass also tends to increase.

However, except for the adsorption characteristic value of 0, there is little change in the adsorption mass between other adsorption characteristic values. This is the adsorption mass of the evaporation gas that appears when the fuel in the fuel tank 110 is spontaneously evaporated for a rather short time of about 500 seconds. The distinctiveness can be confirmed when high-temperature environmental conditions with high evaporation of fuel and fuel with high vapor pressure are applied.

In addition, since it is impossible to measure the adsorbed mass in real time in the actual test device, the total weight of the canister 120 before and after the test was measured, and the difference was regarded as the adsorbed mass of the evaporation gas, and the amount was approximately 18.15 g, which is the predicted result. It is found to be approximately equivalent to

6 is an example showing the result of predicting the boil-off gas concentration of the closed purge system according to a preferred embodiment of the present invention.

Referring to FIG. 6, the concentration of boil-off gas according to the change in the desorption characteristic value is confirmed to change within the initial 70 seconds when the maximum concentration occurs, and there is no significant difference in all the desorption characteristic values after about 70 seconds. It can be seen that the boil-off gas concentration value similar to the test concentration is approximately at the desorption characteristic (des_multi) value of 20 to 25.

7 is another example showing the prediction result of boil-off gas concentration of a closed purge system according to a preferred embodiment of the present invention.

Referring to FIG. 7 , as in FIG. 6 , it can be confirmed that the change in adsorption mass according to the change in the adsorption characteristic value is not large. This is because, as described above, the period during which the evaporation gas is adsorbed to the activated carbon is short, and also, unlike the gaseous state concentration value, the solid state mass value is less sensitive to the adsorption characteristic value.

In FIG. 7, the desorption characteristic value is applied to the value of 20 to 25 found in FIG. 6, and the adsorption characteristic value is changed from 0.00027 to 2.7, and the adsorption mass of activated carbon is generated at the rear end of the purge control solid valve 150. It can be confirmed that the concentration values in the gaseous state were compared.

Analysis conditions for predicting the boil-off gas concentration include a condition in which the fuel tank shutoff valve 130 is always open for about 500 seconds and the purge control solid valve 150 is opened after about 500 seconds after it is closed.

In order to select the adsorption characteristic value, the concentration of the purge control solid valve 150 is calculated according to the adsorption characteristic value after fixing the desorption characteristic value instead of analyzing the change in adsorption amount of activated carbon. As a result, the maximum concentration of the test value and found to be of equal level.

Unlike FIG. 6 based on the adsorption mass, it can be seen that a slight difference from the test maximum concentration occurs at an adsorption characteristic value of 0.027 or less in FIG. 7, and the change is greatly slowed at an adsorption characteristic value of 0.027 or more. That is, it can be confirmed that the adsorption characteristic value is at least 0.027.

The above description is merely an example of the technical idea of the present invention, and those skilled in the art can make various modifications, changes, and substitutions without departing from the essential characteristics of the present invention. will be. Therefore, the embodiments disclosed in the present invention and the accompanying drawings are not intended to limit the technical idea of the present invention, but to explain, and the scope of the technical idea of the present invention is not limited by these embodiments and the accompanying drawings. .

100: closed purge system
110: fuel tank
120: canister
130: fuel tank shutoff valve
140: active purge pump
150: purge control solid valve
200: engine

Claims (14)

delete delete delete delete Boiled gas of a closed purge system including a canister equipped with activated carbon, a fuel tank shut-off valve provided between the canister and the rear end of the canister on the atmospheric side, and a purge control solid valve provided between the canister and the engine of the vehicle. In the adsorption mass and concentration prediction method,
a one-dimensional model generating step of generating a one-dimensional model in consideration of the closed fuzzy system;
a chemical reaction model generation step of generating a chemical reaction model in consideration of a chemical reaction between the activated carbon and the boil-off gas loaded into the canister and including it in the one-dimensional model;
an adsorption mass calculation step of calculating an adsorption mass of the boil-off gas adsorbed on the activated carbon using the one-dimensional model; and
a concentration calculation step of calculating a concentration of the boil-off gas purged through the purge control solid valve using the one-dimensional model;
A method for predicting the adsorption mass and concentration of boil-off gas of a closed purge system comprising a. According to claim 5,
Further comprising an analysis condition setting step of setting analysis conditions in which the fuel tank shutoff valve is opened and the purge control solid valve is maintained in a closed state for a predetermined time when calculating the adsorbed mass of the boil-off gas in the chemical reaction model. A method for predicting the adsorption mass and concentration of boil-off gas of a closed purge system, characterized in that. According to claim 6,
In the step of setting the analysis conditions,
Setting an analysis condition in which the fuel tank shutoff valve is closed and the purge control solid valve is changed from a closed state to an open state after the predetermined time when calculating the concentration of the boil-off gas in the chemical reaction model A method for predicting the adsorption mass and concentration of boil-off gas of a closed purge system, characterized in that. According to claim 6,
The adsorption mass calculation step,
Extracting the adsorption characteristics of the activated carbon from the chemical reaction model and calculating the adsorption mass of the boil-off gas by varying the extracted adsorption characteristics. According to claim 7,
The concentration calculation step,
Extracting the desorption characteristics of the activated carbon from the chemical reaction model, and calculating the concentration of the evaporation gas by varying the extracted desorption characteristics. According to claim 5,
A reference value comparison step of comparing the adsorption mass and concentration of the evaporation gas with a previously prepared reference value and determining whether they match the reference value. According to claim 10,
When the adsorbed mass and concentration of the boil-off gas do not match the reference value in the reference value comparison step, a characteristic correction step of modifying the adsorption and desorption characteristics of the activated carbon to approximate the reference value A method for predicting the adsorption mass and concentration of boil-off gas in a purge system. According to claim 10,
In the reference value comparison step, when the adsorbed mass and concentration of the boil-off gas match the reference value, an analysis end step of completing the prediction of the adsorbed mass and concentration of the boil-off gas Adsorption mass and concentration prediction methods. According to claim 5,
The one-dimensional model,
A closed purge system characterized in that it is generated based on components of a fuel tank in which the boil-off gas is stored, the canister, an active purge pump provided between the canister and the purge control solid valve, and the purge control solid valve. Evaporation adsorption mass and concentration prediction method. According to claim 5,
The chemical reaction model,
The activated carbon is set to pure carbon particles, the boil-off gas is set to hydrocarbons, and the chemical reaction between the pure carbon particles and the hydrocarbons is quantified by a reaction rate formula. Concentration prediction method.

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