Method for estimating volume of reservoir to be filled from pressurized fluid dispensing station

Abstract

The invention relates to a method (10) for estimating a volume (V) of a reservoir (2) to be filled from a pressurized fluid dispensing station (5), said method (10) comprising the following steps: a step (S1) of injecting a pressurized fluid flow into the reservoir (2), a step (S2) of determining a pressure change (dp) in the reservoir (2) after the injection of the fluid flow, a step (S3) of determining the quantity (dm) of the fluid flow injected into the reservoir (2), a step (S4) of estimating the volume (V) of the reservoir (2) to be filled on the basis of the quantity (dm) of the fluid flow injected into the reservoir (2) and on the basis of the pressure change (dp) in the reservoir (2) after the injection of the fluid flow, characterized in that the volume (V) of the reservoir (2) to be filled is also estimated on the basis of the injection temperature (Tinj), and the volume (V) of the reservoir (2) to be filled is calculated on the basis of the pressure change (dp) in the reservoir (2) after the injection of the fluid flow. The invention relates to a method for filling a reservoir (2), i.e. A temperature of a fluid flow entering the reservoir (2), and a volume (V) of the reservoir (2) to be filled is estimated on the basis of a temperature change (dT) in the reservoir (2) after the injection of the fluid flow, the temperature change being determined with respect to an initial temperature (T0) of the reservoir (2) before the injection.

Description

Technical Field

[0001] The invention relates to a method for estimating the volume of a reservoir to be filled from a pressurized fluid dispensing station. The fluid to be delivered may be gaseous hydrogen. The reservoir to be filled may be incorporated into a vehicle, in particular a vehicle with a fuel cell. Background Art

[0002] The method for estimating the volume of a reservoir to be filled generally comprises the following steps:

[0003] - a step of injecting a pressurized fluid stream into the reservoir,

[0004] - a step of determining the change in pressure in the reservoir after the injection of the fluid flow, the change in pressure being determined relative to the initial pressure of the reservoir before the injection,

[0005] - a step of determining the amount of fluid flow to be injected into the reservoir, and

[0006] - A step of estimating the volume of the reservoir to be filled based on the amount of fluid flow injected into the reservoir and the change in pressure in the reservoir after injecting the fluid flow.

[0007] By knowing the volume of the reservoir to be filled, it is possible in particular to determine the pressure gradient according to which the reservoir is filled.

[0008] If the reservoir volume can be communicated to the fluid dispensing station by means of a communication system installed in the vehicle housing the reservoir to be filled, in the absence of such a communication system, or in order to verify the data communicated by this communication system, the dispensing station must be able to independently estimate the volume of the reservoir to be filled.

[0009] Existing methods are far from accurate in estimating the volume of the reservoir to be filled, so correction factors must usually be applied to approximate the actual reservoir volume to be filled.

[0010] Furthermore, the correction factor depends on the size of the reservoir to be filled and on the filling conditions (initial pressure, injection temperature, etc.) Therefore, according to the existing methods for estimating the volume of the reservoir to be filled, this correction factor must be recalculated.

[0011] Document FR0955229 also discloses a method for estimating the volume of a reservoir to be filled, which has the advantage of being more accurate. However, this method has the disadvantage of requiring a relatively large number of calculations and requiring an iterative process to make these calculations converge to a volume value. It may also happen that the iterative process according to this method does not converge to any volume value.

[0012] As the fuel cell vehicle market continues to grow, there is an obvious need to develop a volume estimation method that is simple, universal, and provides more accurate results, taking into account the diversity of reservoirs to be filled and the variety of filling stations. Summary of the invention

[0013] To this end, while complying with the general definition given in the above introduction, the present invention is characterized in that the volume of the reservoir to be filled is estimated also based on the injection temperature (that is, the temperature of the fluid flow entering the reservoir) and based on the temperature change in the reservoir after the injection of the fluid flow, the temperature change being determined relative to the initial temperature of the reservoir before the injection.

[0014] Therefore, in order to estimate the volume of the reservoir to be filled, the method according to the invention takes into account a more realistic thermodynamic assumption (i.e., the temperature changes after injection). In this way, the invention differs from the prior art in which it is assumed that the temperature of the fluid in the reservoir is constant during injection.

[0015] Furthermore, by taking into account the injection temperature and the temperature change of the fluid in the reservoir after injection, the method according to the invention makes it possible to estimate the volume of the reservoir more accurately. Thus, the invention makes it unnecessary to provide a correction factor and makes it possible to estimate the volume of any type of reservoir, regardless of the filling situation encountered at the dispensing station.

[0016] The present invention is also able to estimate the volume directly without the need for an iterative process.

[0017] Embodiments of the invention may include one or more of the following features:

[0018] Estimate the initial temperature at ambient temperature.

[0019] The volume of the reservoir to be filled is related to the amount of fluid flow injected, the pressure change, the injection temperature and the temperature change in the reservoir via a function obtained from the equation of state applied to the fluid in the reservoir and the enthalpy balance applied to the same fluid in the reservoir.

[0020] The equation of state applied to the fluid in the reservoir is the ideal gas equation:

[0021]

[0022] Among them, p[Pa], V[m 3 ], T [K], m [kg], M [kg / mol] and z (unitless) are the pressure, volume, temperature, mass, molar mass and compressibility of the fluid in the reservoir to be filled, respectively, and R [J / mol·K] is the ideal gas constant.

[0023] The function relating the volume of the reservoir to the injection temperature, the amount of fluid flow injected into the reservoir, the pressure change in the reservoir, and the temperature change in the reservoir can be written in the form of a product of two factors:

[0024] - a first constant factor, which depends only on the amount of fluid flow injected into the reservoir and the pressure variation in the reservoir, and

[0025] -The second factor f(T0,T inj ,p0), which depends on the initial pressure in the reservoir, the injection temperature and the initial temperature.

[0026] Therefore, the second factor can be written as:

[0027]

[0028] where c p [J / (kg·K)], β[1 / K], ρ[kg / m 3 ] and h(p0,T0)[J / kg] are the mass heat capacity, isobaric expansion coefficient, density and mass enthalpy of the fluid in the reservoir, respectively; h(p0,T inj ) [J / kg] is the mass enthalpy of the fluid flow injected into the reservoir, and r is the ratio of the ideal gas constant R [J / mol·K] to the molar mass M [kg / mol] of the fluid to be filled in the reservoir.

[0029] The second factor f(T0,T inj ,p0) through the interpolation polynomial f * (T0,T inj ,p0) is approximately obtained.

[0030] The second factor f(T0,T inj ,p0) of the interpolation polynomial f * (T0,T inj ,p0) is a variable with three variables (T0,T inj ,p0), a quadratic polynomial of three variables (T0,T inj , p0) represent the initial temperature of the fluid in the reservoir, the injection temperature and the initial pressure of the fluid in the reservoir respectively.

[0031] The reservoir to be filled is fluidically connected to a source reservoir of the fluid dispensing station via a dispenser.

[0032] The amount of fluid flow injected into the reservoir and the pressure change in the reservoir are measured with the aid of sensors located in the dispenser. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Other particular features and advantages will become apparent from a reading of the following description provided with reference to the following drawings, in which:

[0034] [ Figure 1 ] schematically illustrates a reservoir to be filled in fluid connection with a pressurized fluid dispensing station;

[0035] [ Figure 2 ] schematically illustrates the steps of the method according to the present invention. DETAILED DESCRIPTION

[0036] like[ Figure 1 ] As shown in FIG. 1 , the present invention relates to a method 10 for estimating the volume V of a reservoir 2 (receiving reservoir) to be filled from a source reservoir 3 containing a pressurized fluid.

[0037] refer to[ Figure 2 ], the reservoir to be filled 2 can be incorporated in a vehicle 4, in particular a vehicle with a fuel cell. The source reservoir 3 can be installed at a pressurized fluid distribution station 5. The fluid involved can be gaseous hydrogen.

[0038] In particular, the dispensing station 5 also comprises a dispensing member 6 and a valve 7 located between the source reservoir 3 and the dispensing member 6 .

[0039] The dispensing member 6 comprises a filling line connected to the source reservoir 3 and a nozzle (not shown) for engaging in a container provided in the vehicle 4, said container containing the reservoir to be filled 2. The dispensing member 6 may also be equipped with sensors (not shown) for measuring respectively the temperature, pressure and flow rate of the fluid flow entering the reservoir to be filled 2.

[0040] The estimation method 10 comprises a step S0 of connecting the dispensing member 6 of the station 5 to the container of the vehicle 4 containing the reservoir 2 to be filled (including fluid communication between the filling line of the dispensing member and the volume of the reservoir 2). In this step S0, the valve 7 remains closed. A pressure balance occurs between the dispensing member 6 and the reservoir 2 to be filled. This balance makes it possible to determine or measure the initial pressure p0 of the reservoir 2 to be filled.

[0041] In the same step S0 , the dispensing station 5 measures the ambient temperature. This can be used to estimate the initial temperature T0 in the reservoir 2 to be filled.

[0042] In step S1, valve 7 is opened for a relatively short time interval, lasting a few seconds (e.g., 5 seconds; in other words, a discrete or "pulsed" jet is ejected). Then, according to a predefined pressure gradient (e.g., 5 bar / s), fluid is injected from source reservoir 3 into reservoir to be filled 2. Injecting fluid into reservoir to be filled 2 results in an increase in pressure measured by the pressure sensor.

[0043] After the valve 7 is closed, the pressure measured by the pressure sensor drops to a certain value p1. This pressure p1 is the same as the pressure of the reservoir 2 to be filled.

[0044] In step S2, the method 10 provides a measurement of the pressure variation between the injection start time t0 and the end time t1. This pressure variation can be written as dp=p1-p0. In addition, in the same step S2 or in a different step S3, the method 10 also provides a measurement of the amount dm of the fluid flow injected into the reservoir 2 to be filled.

[0045] The amount dm of the fluid flow injected into the reservoir 2 to be filled (hereinafter referred to as the material amount dm) can be obtained by time-integrating the mass flow rate between the times t0 and t1:

[0046] In step S4 of method 10 , the volume V of the reservoir to be filled is determined. The calculation of the volume V of the reservoir 2 to be filled takes into account the pressure variation dp, the amount dm of the fluid flow injected into the reservoir 2 to be filled and the initial temperature T0 of the reservoir 2 to be filled.

[0047] According to the invention, the calculation of the volume V also takes into account the injection temperature T inj , that is to say the temperature of the fluid flow entering the reservoir 2 to be filled, and the temperature change dT in the reservoir 2 after the injection of the fluid flow, which temperature change is determined relative to the initial temperature T0 of the reservoir 2 before the injection.

[0048] When estimating the volume V of the reservoir 2 to be filled, the initial pressure p0 and initial temperature T0 of the reservoir 2 before injection, the temperature change dT and mass change dm in the reservoir 2 after injection, and the injection temperature T are taken into account. inj :

[0049] V=f(p0,T0,dT,dm,T inj )

[0050] The above relationship is obtained from the equation of state applied to the fluid flow entering the reservoir 2 to be filled and from the enthalpy balance applied to the same fluid flow.

[0051] Advantageously, the fluid is considered to be an ideal gas and the equation of state applicable to the fluid injected into the reservoir 2 to be filled can be written as follows:

[0052]

[0053] Among them, p[Pa], V[m 3 ], T [K], m [kg], M [kg / mol] and z (unitless) are the pressure, volume, temperature, mass, molar mass and compressibility of the fluid in the reservoir to be filled, respectively, and R [J / mol·K] is the ideal gas constant.

[0054] The enthalpy balance of the fluid to be filled in reservoir 2 is written as follows:

[0055]

[0056] in,

[0057] β[1 / K], c p [J / (kg·K)] and h[J / kg] are the isobaric expansion coefficient, mass heat capacity and mass enthalpy of the gas, respectively;

[0058] u inj [m / s] is the velocity of injected gas;

[0059] S w [m 2 ]、T g,w [K], k g [W / m 2 / K] are the inner surface area of ​​the reservoir, the average temperature of the inner wall surface, and the heat transfer coefficient between the gas and the wall, respectively.

[0060] The heat exchange between the gas and the walls of the reservoir to be filled is not taken into account (that is, it is assumed that k g S w (T g,w -T)≈0), nor does it consider the kinetic energy of the fluid relative to the enthalpy (that is, assuming The enthalpy balance can then be written as:

[0061]

[0062] After deriving the above equation of state and combining the derived expression with the simplified expression of the above enthalpy balance, the volume V of the reservoir 2 to be filled, the injection temperature T inj The relationship between the quantity dm, the pressure change dp and the temperature change dT can be written as follows:

[0063] in

[0064] The initial temperature T0 can be approximated by the ambient temperature measured at the dispensing station 5 .

[0065] It should be noted that the function f(T0,T inj ,p0) is determined based on ideal gas data provided by the literature (e.g., data published by the National Institute of Standards and Technology (NIST) of the United States).

[0066] In the absence of ideal gas data, and / or for rapid and accurate machine calculation of volume, the present invention provides the use of interpolation polynomials f * (T0,T inj ,p0) to replace the function f(T0,T inj ,p0).

[0067] Advantageously, the interpolation polynomial f * (T0,T inj ,p0) can be a variable with three variables (T0,T inj ,p0). This polynomial can be written as follows:

[0068]

[0069] Interpolation polynomial f * (T0,T inj ,p0) i (where i∈[0,10]) can be determined by the least squares linear regression method.

[0070] Verification studies of the method according to the invention have shown that using the interpolation polynomial f * (T0,T inj ,p0) and the volume V estimated using the function f(T0,T inj ,p0) has little difference in the estimated volume V. In addition, approximating the initial temperature T0 by the ambient temperature measured at the station gives satisfactory results.

Claims

1. A method (10) for estimating the volume (V) of a reservoir (2) to be filled from a station (5) for dispensing a pressurized fluid, such as gaseous hydrogen, comprising the following steps: - a step (S1) of injecting a pressurized fluid into said reservoir (2), - a step (S2) of determining the pressure variation (dp) in said reservoir (2) after the injection of the fluid flow, said pressure variation being determined relative to the initial pressure (p0) of said reservoir (2) before the injection, - a step (S3) of determining the amount (dm) of the fluid flow injected into said reservoir (2), - a step (S4) of estimating the volume (V) of the reservoir (2) to be filled based on the amount (dm) of the fluid flow injected into the reservoir (2) and based on the pressure variation (dp) in the reservoir (2) after the injection of the fluid flow, Characterized in that the volume (V) of the reservoir (2) to be filled is also estimated based on the injection temperature (Tinj), that is, the temperature of the fluid flow entering the reservoir (2), and based on the temperature change (dT) in the reservoir (2) after the fluid flow is injected, wherein the temperature change is determined relative to the initial temperature (T0) of the reservoir (2) before injection.

2. The method (10) according to the preceding claim, characterized in that The initial temperature (T0) is estimated to be equal to the ambient temperature.

3. The method (10) according to any one of the preceding claims, characterized in that The volume (V) of the reservoir (2) to be filled is related to the amount of fluid flow injected (dm), the pressure change (dp), the injection temperature (Tinj) and the temperature change (dT) in the reservoir (2) by means of a function obtained from the state equation applied to the fluid in the reservoir (2) and the enthalpy balance of the same fluid applied to the reservoir (2).

4. The method (10) according to the preceding claim, characterized in that The equation of state applied to the fluid in the reservoir (2) is the ideal gas equation, which is given by: Among them, p[Pa], V[m 3 ], T[K], m[kg], M[kg / mol] and z (unitless) are respectively the pressure, volume, temperature, mass, molar mass and compressibility of the fluid in the reservoir (2) to be filled, and R[J / mol·K] is the ideal gas constant.

5. The method (10) according to any one of claims 3 and 4, characterized in that The volume (V) of the reservoir (2) and the injection temperature (T inj ), the amount of fluid flow injected into the reservoir (2) (dm), the pressure change in the reservoir (2) (dp) and the temperature change in the reservoir (2) (dT) can be written in the form of a product of two factors: - a first constant factor which depends only on the amount of fluid flow injected into said reservoir (2) (dm) and on the pressure variation (dp) in said reservoir (2), and -The second factor f(T0,T inj , p0), which depends on the initial pressure (p0) in the reservoir (2), the injection temperature (T inj ) and initial temperature (T0).

6. Method according to the preceding claim, characterized in that The second factor f(T0,T inj ,p0) is written as follows: where c p [J / (kg·K)], β[1 / K], ρ[kg / m 3 ] and h(p0,T0)[J / kg] are respectively the mass heat capacity, isobaric expansion coefficient, density and mass enthalpy of the fluid in the reservoir (2); h(p0,T inj ) [J / kg] is the mass enthalpy of the fluid flow injected into the reservoir (2), and r is the ratio of the ideal gas constant R [J / mol·K] to the molar mass M [kg / mol] of the fluid in the reservoir (2) to be filled.

7. The method (10) according to the preceding claim, characterized in that The second factor f(T0,T inj ,p0) through the interpolation polynomial f * (T0,T inj ,p0) is approximately obtained.

8. The method (10) according to the preceding claim, characterized in that The second factor f(T0,T inj ,p0) of the interpolation polynomial f * (T0,T inj ,p0) is a variable with three variables (T0,T inj ,p0), wherein the three variables respectively represent the initial temperature of the fluid in the reservoir (2), the injection temperature and the initial pressure of the fluid in the reservoir (2).

9. The method (10) according to any one of the preceding claims, characterized in that The reservoir to be filled (2) is fluidically connected to the source reservoir (3) of the fluid dispensing station (5) via a dispenser (6), the amount of fluid (dm) injected into the reservoir (2) and the pressure change (dp) in the reservoir (2) being measured by means of a sensor located at the dispenser (6).

Images