Method for estimating the volume of a tank to be filled from a pressurized fluid distribution station.

Abstract

A method (10) for estimating the volume (V) of a tank (2) to be filled from a pressurized fluid distribution station (5), such as gaseous hydrogen, the method (10) comprising the following steps: - a step (S1) of injecting a pressurized fluid stream into the tank (2), - a step (S2) of determining a pressure variation (dp) in the tank (2) after the injection of the fluid stream, the pressure variation being determined relative to an initial pressure ( of the tank (2) before the injection, - a step (S3) of determining a quantity (dm) of the fluid stream injected into the tank (2), - a step (S4) of estimating the volume (V) of the tank (2) to be filled as a function of the quantity (dm) of the fluid stream injected into the tank (2) and as a function of the pressure variation (dp) in the tank (2) after the injection of the fluid stream.characterized in that the volume (V) of the reservoir (2) to be filled is also estimated as a function of an injection temperature ( ), i.e., a temperature of the fluid flow entering the reservoir (2), and as a function of a temperature change (dT) in the reservoir (2) after the injection of the fluid flow, the temperature change being determined relative to an initial temperature ( ) of the reservoir (2) before the injection. Figure of the abstract: Figure 2,

Description

Title of the invention: 1. Method for estimating a tank volume to be filled from a pressurized fluid distribution station.

[0001] The invention relates to a method for estimating a tank volume to be filled from a pressurized fluid distribution station. The fluid to be transferred may be gaseous hydrogen. The tank to be filled may be integrated into a vehicle, in particular a fuel cell vehicle.

[0002] The method for estimating a tank volume to be filled generally comprises the following steps: - a step of injecting a flow of pressurized fluid into the reservoir, - a step of determining a pressure variation in the reservoir after injection of the fluid flow, the pressure variation being determined relative to an initial pressure of the reservoir before injection, - a step of determining a quantity of the fluid flow injected into the reservoir, and - a step of estimating the volume of the reservoir to be filled based on the quantity of fluid flow injected into the reservoir and based on the pressure variation in the reservoir after injection of the fluid flow.

[0003] Knowing the volume of the tank to be filled makes it possible to determine in particular a pressure ramp according to which the tank will be filled.

[0004] If the volume of the tank can be communicated to the fluid distribution station using a communication system installed in the vehicle housing the tank to be filled, in the absence of such a communication system, or for the purposes of verifying data communicated by this communication system, the distribution station must be able to independently estimate the volume of the tank to be filled.

[0005] Current methods provide an estimate of the volume of the tank to be filled which is far from precise, so that a correction coefficient is generally necessary to approach the real value of the volume of the tank to be filled.

[0006] Moreover, the correction coefficient depends on the dimensions of the tank to be filled and the filling scenario (initial pressure, injection temperature, etc.). Thus, according to current methods for estimating the volume of a tank to be filled, it is necessary to recalculate this correction coefficient.

[0007] Furthermore, document FR0955229 discloses a method for estimating the volume of a tank to be filled, which has the advantage of being more precise. However, This method suffers from the disadvantage of requiring a relatively large number of calculations and an iterative process to converge these calculations on a volume value. Moreover, it may happen that the iterative process according to this method does not converge to any volume value.

[0008] With the growing development of the fuel cell vehicle market, and taking into account the diversity of tanks to be filled and filling stations, it appears necessary to develop a volume estimation method which is simple and universal, and which leads to more precise results.

[0009] To this end, the invention, moreover in accordance with the generic definition given in the preamble above, is characterized in that the volume of the reservoir to be filled is also estimated as a function of an injection temperature, that is to say a temperature of the flow of fluid entering the reservoir, and as a function of a temperature variation in the reservoir after the injection of the flow of fluid, the temperature variation being determined relative to an initial temperature of the reservoir before the injection.

[0010] Thus, for the estimation of the volume of the tank to be filled, the method according to the invention retains a thermodynamic hypothesis (namely a variation in temperature after injection) which is closer to reality. In this, the invention differs from the prior art according to which the temperature of the fluid in the tank is assumed to be constant during injection.

[0011] Furthermore, by taking into account the injection temperature and the variation in the temperature of the fluid in the reservoir after injection, the method according to the invention makes it possible to obtain a more precise estimate of the volume of a reservoir. Thus, the invention makes it possible to avoid the need to provide a correction coefficient, and opens up the possibility of estimating the volume of any type of reservoir, regardless of the filling scenario encountered at the distribution station.

[0012] The invention also makes it possible to obtain a volume estimate directly, without an iterative process.

[0013] Embodiments of the invention may include one or more of the following features:

[0014] The initial temperature is estimated at room temperature.

[0015] The volume of the reservoir to be filled is related to the quantity of the injected fluid flow, to the pressure variation, to the injection temperature and to the temperature variation in the reservoir, through a function obtained from an equation of state applied to the fluid in the reservoir, and from an enthalpy balance applied to the same fluid in the reservoir.

[0016] The equation of state applied to the fluid in the reservoir is a real gas equation

[0017] given by: pV = gRz(p, T)Twith p [Pa], V [m3], T [K], m [kg], M [kg / mol] and z (unitless) respectively the pressure, volume, temperature, mass, molar mass and compressibility of the fluid in the tank to be filled, and R [J / mol.K] the ideal gas constant. The function relating the reservoir volume to the injection temperature, the quantity of fluid flow injected into the reservoir, the pressure variation in the reservoir, and the temperature variation in the reservoir, can be written as a product of two factors: - a first constant factor depending only on the quantity of fluid flow injected into the reservoir and the pressure variation in the reservoir, and - a second factor f Tinb P ) ^pending on the initial pressure in the tank, injection temperature and initial temperature.

[0018] The second factor can be written as follows: ff T T- ■ n ) - rzTn + l F1 - rpTn~ - rf z+Tn™ ) — ] 1\1mj! Pq) iziQf Cp p 1 Aojp ) cP j where cP[J / (kg.K)], p[l / K], P[kg / m3] and |^p [J / kg] represent respectively the specific heat capacity, the coefficient of isobaric expansion, the density and the specific enthalpy of the fluid in the reservoir; j^p [J / kg] represents the specific enthalpy of the fluid flow injected into the reservoir, and1 the ratio between the ideal gas constant R [J / mol.K] and the molar mass M [kg / mol] of the fluid in the reservoir to be filled.

[0019] The second factor f Tq, Tjnj, pj is approximated by an interpolation polynomial f ( Tq, Tjnj, po j •

[0020] The polynomial f*^Tg, Tjnj, pj of interpolation of the second factor f TC), Tjnj, pj is a polynomial of degree two and with three variables pj re respectively presenting the initial temperature of the fluid in the reservoir, the injection temperature and the initial pressure of the fluid in the reservoir.

[0021] The tank to be filled is fluidically connected to a source tank of the fluid distribution station via a distributor.

[0022] The quantity of fluid flow injected into the reservoir as well as the pressure variation in the reservoir are measured using sensors positioned at the distributor.

[0023] Other features and advantages will appear on reading the description below. after, made with reference to the following figures in which:

[0024] [Fig. 1] schematically illustrates a tank to be filled fluidically connected to a station for distributing a pressurized fluid;

[0025] [Fig.2] schematically illustrates the steps of the method according to the invention.

[0026] As illustrated in [Fig.l], the invention relates to a method 10 for estimating a volume V of a tank 2 to be filled (receiving tank) from a source tank 3 containing a pressurized fluid.

[0027] With reference to [Fig. 2], the tank 2 to be filled can be integrated into a vehicle 4, and in particular a fuel cell vehicle. The source tank 3 can be installed at a station 5 for distributing a pressurized fluid. The fluid concerned can be gaseous hydrogen.

[0028] In particular, the distribution station 5 also comprises a distribution member 6 and a valve 7 positioned between the source reservoir 3 and the distribution member 6.

[0029] The distribution member 6 comprises a filling pipe connected to the source tank 3 as well as a nozzle (not shown) intended to engage in a receptacle provided at the level of the vehicle 4 containing the tank 2 to be filled. In addition, the distribution member 6 can be equipped with sensors (not shown) making it possible to measure respectively the temperature, the pressure, the flow rate of a flow of fluid entering the tank 2 to be filled.

[0030] The estimation method 10 comprises a step S0 which consists of connecting the distribution member 6 of the station 5 to the receptacle of the vehicle 4 containing the tank 2 to be filled (fluid communication between the filling pipe comprising the distribution member and the volume of the tank 2). During this step S0, the valve 7 remains closed. A pressure balancing takes place between the distribution member 6 and the tank 2 to be filled. This balancing makes it possible to determine or measure the initial pressure pO of the tank 2 to be filled.

[0031] During this same step S0, the ambient temperature is measured by the distribution station 5. It can be used to estimate the initial temperature To in the tank 2 to be filled.

[0032] During a step S1, the valve 7 is opened for a relatively short period of time, of the order of a few seconds (for example 5s, i.e. there is injection of a discrete jet “pulse” in English). The fluid coming from the source reservoir 3 is then injected into the reservoir 2 to be filled according to a predefined pressure ramp, for example 5 bar / s. The injection of the fluid into the reservoir 2 to be filled causes an increase in the pressure measured by the pressure sensor.

[0033] After closing the valve 7, the pressure measured by the pressure sensor decreases to reach a certain value pi. This pressure pl is identical to that of tank 2 to fill.

[0034] During a step S2, the method 10 provides a measurement of the pressure variation between a start t0 and an end t1 of the injection. This pressure variation can be written dp = p - p Furthermore, during this same step S2 or a different step S3, the method 10 also provides a measurement of the quantity dm of the flow of fluid injected into the reservoir 2 to be filled.

[0035] The quantity dm of the fluid flow injected into the reservoir 2 to be filled (also simply called in the following quantity dm of material) can be obtained by time integration of the mass flow rate between the instants t0 and tp b dm = ] mdt

[0036] During a step S4 of the method 10, the volume V of the tank to be filled is determined. The calculation of the volume V of the tank 2 to be filled takes into account the pressure variation dp, the quantity dm of the fluid flow injected into the tank 2 to be filled, and the initial temperature To of the tank 2 to be filled.

[0037] According to the invention, the calculation of the volume V also takes into account an injection temperature T ij, i.e. a temperature of the fluid flow entering the reservoir 2 to be filled, and a temperature variation dT in the reservoir 2 after the injection of the fluid flow, the temperature variation being determined relative to the initial temperature To of the reservoir 2 before the injection.

[0038] The initial pressure p0 and the initial temperature To of the reservoir 2 before injection, the temperature variation dT, and the mass variation dm in the reservoir 2 after injection, as well as the injection temperature Tinj are taken into account in the estimation of the volume V of the reservoir 2 to be filled through a correlation which can be written as follows: V = f(p0, To, dT, dm, Tinj)

[0039] The above correlation is obtained from an equation of state applied to the fluid flow in the tank 2 to be filled, and from an enthalpy balance applied to the same flow.

[0040]

[0041] Advantageously, by considering the fluid as a real gas, the equation of state of the fluid injected into the reservoir 2 to be filled can be written as follows: pV = f Rzip. T)T with p [Pa], V [m3], T [K], m [Kg], M [kg / mol] and z (unitless) respectively the pressure, volume, temperature, mass, molar mass and compressibility of the fluid in the tank to be filled, and R [J / K / mol] the ideal gas constant. The enthalpy balance of the fluid in tank 2 to be filled is written as follows: mcp^ = +k^(Tt«-T) TW) + 41 -h(p. T)^“ P [1 / K], cp [J / (kg.K)], h [J / kg] respectively the coefficient of isobaric expansion, the specific heat capacity and the specific enthalpy of the gas; uinj [m / s] the injection gas velocity; Sw [m2], Tg,w [K], kg [W / m2 / K] respectively the inner surface of the tank, the average temperature of the inner wall surface and the heat exchange coefficient between the gas and the wall.

[0042] By neglecting the heat exchange between the gas and the wall of the tank to be filled (i.e. by setting kgS^Tg.wT) « 0), and by neglecting the kinetic energy of the fluid in front of the enthalpy (i.e. by setting u^i , ), the enthalpy balance can 2 to write: HT ~ Hn । ' u 1 " mCp upt mCp uni

[0043] After deriving the equation of state presented above, and combining the derived expression with the simplified expression of the enthalpy balance above, the correlation between the volume V of the reservoir 2 to be filled, the injection temperature Tinj, the quantity dm, the pressure variation dp, and the temperature variation dT can be written as follows: Vf / Tv T- - LT , V “1(10 1 inr Poj dp / x lzlo+---------------j fpo Tjnj, p I = “r

[0044] The initial temperature To can be approximated by an ambient temperature measured at the distribution station 5.

[0045]

[0046]

[0047] It should be noted that the function fy^ y,^ p is determined from real gas data provided by the literature (e.g. data from the National Institute of Standards and Technology (NIST)). In the absence of real gas data and / or for a rapid and precise volume calculation by an automaton, the invention provides for the use of an interpolation polynomial f^Tg, pj instead of the function fy^ y_ p j. Advantageously, the interpolation polynomial y^ Tjnj, pj can be a polynomial of degree 2 and with three variables ^y^ y_ p j. This polynomial can be written as follows: f (Th Tmj, pj = ao + aiPj + aaTinj + ajTinjPy^Tj + ajTiP] + a6TjnjT1 + a7T1TinjP1 + a8Tf+ +a10p2 The coefficients a; (with i €[0, 10]) of the polynomial f* / y y. . n \ of interpolation * y 1 (hx Pg y

[0049] can be determined by a least squares linear regression method. A validation study of the method according to the invention has shown that the volume V estimated using the interpolation polynomial Tjnj, p ) differs very little from the volume V estimated using the function f pj • Furthermore, an ap approximation of the initial temperature To by the ambient temperature measured at the station gives satisfactory results.

Claims

Claims

1. Method (10) for estimating a volume (V) of a tank (2) to be filled from a station (5) for distributing a pressurized fluid, such as gaseous hydrogen, the method (10) comprising the following steps: - a step (S1) of injecting a flow of pressurized fluid into the tank (2), - a step (S2) of determining a pressure variation (dp) in the tank (2) after the injection of the fluid flow, the pressure variation being determined relative to an initial pressure (nj of the tank (2) before the injection, !(V - a step (S3) of determining a quantity (dm) of the fluid flow injected into the tank (2), - a step (S4) of estimating the volume (V) of the tank (2) to be filled as a function of the quantity (dm) of the fluid flow injected into the tank (2) and as a function of the pressure variation (dp) in the tank (2) after injection of the fluid flow,characterized in that the volume (V) of the reservoir (2) to be filled is also estimated as a function of an injection temperature (Tjnj), i.e. a temperature of the fluid flow entering the reservoir (2), and as a function of a temperature variation (dT) in the reservoir (2) after the injection of the fluid flow, the temperature variation being determined relative to an initial temperature (To) of the reservoir (2) before the injection.,

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

3. Method (10) according to any one of the preceding claims, characterized in that the volume (V) of the reservoir (2) to be filled is linked to the quantity (dm) of the injected fluid flow, to the pressure variation (dp), to the injection temperature (Tjnj) and to the temperature variation (dT) in the reservoir (2), through a function obtained from an equation of state applied to the fluid in the reservoir (2) and from an enthalpy balance applied to the same fluid in the reservoir (2).

4. Method (10) according to the preceding claim, characterized in that the equation of state applied to the fluid in the reservoir (2) is a real gas equation given by: pV^Rzfc T)T With p [Pa],V [m3], T [K], m [kg], M [kg / mol] and z (unitless) 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] the ideal gas constant.

5. Method (10) according to any one of claims 3 or 4, characterized in that the function linking the volume (V) of the reservoir (2) to the injection temperature (Tjnj), the quantity (dm) of the fluid flow injected into the reservoir (2), the pressure variation (dp) in the reservoir (2), and the temperature variation (dT) in the reservoir (2), can be written in the form of a product of two factors: - a first constant factor depending only on the quantity (dm) of the fluid flow injected into the reservoir (2) and the pressure variation (dp) in the reservoir (2), and a - second factor Tjnj, p ) depending on the initial pressure (p0) in the reservoir (2), the injection temperature (T^j) and the initial temperature (To).

6. Method according to the preceding claim, characterized in that the second factor p / t T- n 1 is written as follows: 1m.rPo / f / TT n 1 - [f7T , rnT — + Where cP[J / (kg.K)], P[l / K], P[kg / m3] and |^p [J / kg] represent respectively the specific heat capacity, the isobaric expansion coefficient, the density and the specific enthalpy of the fluid in the reservoir (2); t. j [J / kg] represents the specific enthalpy of the flow v 0' mJ / of fluid injected into the reservoir (2), and1 the ratio between the perfect gas constant R [J / mol.K] and the molar mass M [kg / mol] of the fluid in the reservoir (2) to be filled.

7. Method (10) according to the preceding claim, characterized in that the second factor fpj is approximated by an interpolation polynomial Tjnj, p

8. Method (10) according to the preceding claim, characterized in that the polynomial f ^Tg, T^j, p ) of interpolation of the second factor f(T(> Tinj, p()j is a polynomial of degree two and with three variables pj representing respectively the initial temperature of the

9. fluid in the reservoir (2), the injection temperature and the initial pressure of the fluid in the reservoir (2). Method (10) according to any one of the preceding claims, characterized in that the reservoir (2) to be filled is fluidically connected to a source reservoir (3) of the fluid distribution station (5) via a distributor (6), the quantity (dm) of the fluid flow injected into the reservoir (2) as well as the pressure variation (dp) in the reservoir (2) being measured using sensors positioned at the distributor (6).

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