Method for determining a maximum flow rate setpoint for emptying a pressurized gas tank

Abstract

The invention provides a method for determining a maximum flow rate setpoint for emptying a pressurized gas tank for a mobile or stationary device in order to control the tank temperature during emptying. The determination method comprises the following steps: - measuring the temperature outside the tank and providing a value (Te) of the temperature measured outside the tank, - measuring the temperature inside the tank and providing a value (Ti) of the temperature measured inside the tank, - measuring the pressure inside the tank and providing a value (Pi) of the pressure measured inside the tank. Figure 1 (for the abstract)

Description

Title of the invention: Method for determining a maximum flow rate setpoint for emptying a pressurized gas tank

[0001] The invention relates to a method for determining a maximum discharge rate setpoint for a pressurized gas tank in a mobile or stationary device, particularly for controlling the tank temperature during discharge. The invention also relates to a method for monitoring the tank temperature during discharge. The invention further relates to a computer program and a computer-readable storage medium for implementing the aforementioned method. The invention is applicable to pressurized gas tanks equipping mobile devices such as, for example, motor vehicles (passenger cars, industrial vehicles (vans, trucks, etc.), transport vehicles (trams, subways, buses, etc.), agricultural vehicles (tractors, harvesters, etc.), construction equipment (excavators, bulldozers, etc.), trains, boats, aircraft, spacecraft, etc.) or stationary equipment such as, for example, power plants or generator sets.

[0002] Pressurized gas tanks are used to store and transport all types of gas under pressure. Pressurized gas tanks are generally classified according to one of the following five types: a type I pressurized gas tank having an all-metal construction; a type II pressurized gas tank having a metal construction including a fiber winding for the reinforcement of its cylindrical part; a type III pressurized gas tank having a metal liner with a composite reinforcement structure; a type IV pressurized gas tank including a plastic liner with a composite reinforcement structure; and a type V pressurized gas tank having a composite reinforcement structure and being without a liner.

[0003] Thus, in the prior art, a pressurized gas tank, for example, configured to store and transport gas at a pressure of at least 350 bar or at least 700 bar, the gas being, for example, hydrogen (H2), is already known. This pressurized gas tank is configured for use by a vehicle equipped with the pressurized gas tank for various functions, as an energy source or carrier. This tank is usually made of composite material for reasons of weight reduction and safety.

[0004] Such a pressurized gas tank is, for example, composed of an external composite reinforcement structure to increase the tank's rigidity and an internal casing called a "liner", which has a screw- sealing function with respect to the gas contained in the tank. The liner is, for example, made of a plastic material in the case of a Type IV tank, chosen for its lightness and low manufacturing cost. Alternatively, the liner can be made of a metallic material in the case of a Type III tank. When the tank is emptied to supply a gas-consuming device such as a fuel cell or an internal combustion engine, the temperature inside the tank tends to drop due to the phenomenon of adiabatic expansion. More specifically, for example in a hydrogen tank, when the tank valve is opened to empty the gas, its pressure decreases. Consequently, the temperature of the hydrogen inside the tank also decreases.

[0005] A temperature that is too low, for example between -35°C and -65°C, can cause the liner and / or the seals provided in the tank to degrade. Indeed, the liner and the seals are each made of a polymer material that can degrade at very low temperatures. Their degradation can compromise the tank's seal and thus cause a leak. Furthermore, safety in the vehicle is also at risk because the leaking pressurized gas can cause a fire.

[0006] It is known, notably from document KR10-2019-0075239, to control the temperature inside the tank by controlling the tank emptying rate in order to protect the liner and the seals of a hydrogen tank. It is also known from document EP4159995 to provide a control system for controlling the emptying of a hydrogen tank in such a way as to protect the liner. This system is configured to control the emptying rate by estimating, during the operation of an accelerator, a temperature reached in the tank after a certain time has elapsed with maximum acceleration. Once this temperature is estimated, the control system is able to limit the emptying rate so as to maintain it below a predetermined maximum rate. For this estimation, the temperature measured inside the tank is considered, generally towards the central axis of the tank.This measurement method has several inaccuracies. In addition to the temperature drop caused by pressure reduction within the tank, the temperature outside the tank (or ambient temperature) can significantly influence the temperature inside, primarily due to the natural heat exchange through the tank wall. Furthermore, the gas inside the tank tends to distribute unevenly, creating warmer and cooler zones. In the case of hydrogen, the colder gas tends to settle at the bottom of the tank, while the warmer gas rises. Therefore, depending on its placement within the tank, the temperature sensor may not accurately measure the temperature. Because the internal temperature is such that the estimated temperature drop is relatively rough, the tank emptying rate may be unduly limited as a precaution to avoid the risk of excessively low temperatures. However, an inadequate limitation of the emptying rate can unnecessarily reduce vehicle performance. For example, in this document, the temperature estimation calculations assume maximum acceleration over a given time period, so the flow rate may be limited even when the acceleration was not as significant, and therefore the temperature did not decrease as much as estimated.

[0007] The invention aims in particular to improve the determination of a maximum flow rate setpoint for emptying a pressurized gas tank for a mobile or stationary device, such as a motor vehicle, in order to avoid compromising the tank's sealing without unnecessarily reducing the vehicle's performance.

[0008] To this end, the invention relates to a method for determining a maximum flow rate setpoint for emptying a pressurized gas tank for a mobile or stationary device in order to control the temperature of the tank during its emptying, the determination method comprising the following steps:

[0009] - measure the temperature outside the tank and provide a value (Te) of temperature measured outside the tank,

[0010] - measure the temperature inside the tank and provide a value (T;) of temperature measured inside the tank,

[0011] - measure the pressure inside the tank and provide a pressure value (P;) measured inside the tank,

[0012] - determine, from each of these three values ​​(Te, T, P) and i) from a pre-recorded database and / or ii) from a predefined mathematical function, a maximum tank emptying flow rate setpoint and provide a maximum tank emptying flow rate setpoint value (Qmax).

[0013] Thus, the invention proposes to consider three distinct parameters to determine a maximum discharge flow rate that the tank can withstand while preventing it from reaching a temperature that is too low and could damage a liner or tank seals. The three distinct parameters are the temperature measured outside (Te) of the tank, the temperature measured inside (TO) of the tank, and the pressure measured inside (P) of the tank. The term "triplet" will be used hereafter to refer to these three parameters or values.

[0014] In particular, by considering the temperature outside the tank, the process takes into account the influence of the ambient temperature on the internal temperature of the tank during its emptying. This therefore makes it possible to make the Estimates concerning the temperature reached at the level of a liner or tank seals are used to more accurately determine a maximum flow rate (Qmax) setpoint for emptying the tank. It is understood that the "maximum flow rate (Qmax) setpoint" is a computer-defined value. It is understood that the maximum flow rate setpoint can subsequently be taken into account by the device's control system to reduce, if necessary, the gas injection into a component of the device, and therefore the emptying rate. "Mobile devices" refers, for example, to vehicles (passenger cars, industrial vehicles (vans, trucks, etc.), transport vehicles (trams, subways, buses, etc.), agricultural machinery (tractors, harvesters, etc.), construction equipment (excavators, bulldozers, etc.), trains, boats, aircraft, spacecraft, etc.), and "stationary devices" refers, for example, to power plants or generator sets.

[0015] It is also understood that the steps of measuring the temperature outside the tank, measuring the temperature inside the tank and measuring the pressure inside the tank can be carried out simultaneously or successively, in any order.

[0016] Advantageously, the maximum flow rate setpoint is a mass flow rate value expressed in g / s (grams per second). Furthermore, preferably, the maximum flow rate setpoint corresponds to an average flow rate rather than an instantaneous flow rate. "Average flow rate" means a flow rate at which the tank can be emptied to a predetermined pressure without exceeding a predetermined temperature threshold (Tmin) inside the tank.

[0017] Considering the three parameters (Te, 1), P, 2), a maximum flow rate setpoint is determined in order to provide this value (Qmax) to a control system of the device. Advantageously, this value (Qmax) corresponds to a flow rate limit value to ensure that the temperature inside the tank at the level of a liner or seals always remains above a predetermined threshold (Tmin). This threshold temperature corresponds to the temperature limit that a liner and / or seals can withstand without suffering damage. By controlling the maximum discharge flow rate, it is therefore possible to control the temperature inside the tank, which varies. Thus, the maximum flow rate to be applied is determined in a particularly advantageous way, and therefore the temperature inside the tank is better controlled to prevent damage to the liner and / or seals.

[0018] The term "reservoir" refers to a fluid storage volume that can be divided / distributed into several sub-volumes, which may be identical or different. Each fluid storage sub-volume can be stored in a container separate from the others. The proposed method is particularly advantageous for a reservoir of Type IV, which includes a liner and seals made of polymer materials. However, this process is not limited to Type IV tanks and may also be of interest for other types of tanks, for example Type I, II, III and V tanks, which include seals whose constituent material may not be able to withstand very low temperatures, for example temperatures between -35°C and -65°C.

[0019] Furthermore, by determining the maximum flow rate in an improved manner, it is also possible to better manage the quantity of gas exiting the tank to avoid unnecessarily reducing the device's performance. In particular, unlike the prior art, here the maximum flow rate setpoint is not determined by assuming that the device is under maximum load for a period of time. On the contrary, according to the invention, the estimates are based primarily on what is measured inside and around the tank to best estimate the temperature inside the tank at the level of the liner or the seals, and to allow, as far as possible, a discharge flow rate based on the actual demand of the device operator.

[0020] To determine the maximum flow rate setpoint, the method includes, in a first case, consulting a pre-recorded database. Preferably, the database contains a plurality of possible data for each of the three measured parameters. Once each parameter is measured, that is, once each of the three values ​​Te, T, P is known, the database is consulted to determine an optimal maximum flow rate value with regard to the three measured values ​​Te, T; In other words, the pre-recorded database is constructed with pre-recorded input data for temperatures outside the tank, temperatures inside the tank, and pressures inside the tank, and pre-recorded output data for the maximum tank discharge flow rate setpoint. The maximum flow rate value, indicated in the database, can be obtained beforehand from an experimentally identified limit flow rate, or obtained through numerical simulation. Advantageously, the database includes a plurality of possible maximum flow rate values, considering several possibilities for temperature outside the tank, temperature inside the tank, and pressure inside the tank.

[0021] Alternatively, the process may include, instead of consulting the database, a step of performing a mathematical calculation based on a predefined mathematical function, once each parameter has been measured. For example, the mathematical function is of the type f(Te, T, P) and f is a polynomial function. According to a relatively simple example, the function f is an affine function of the form f(Te, T, P) = aT + bTe + cP, where a, b, and c are three real numbers. dependent on tank parameters, such as tank volume, tank wall thickness, or tank operating pressure. In more complex examples, the function f is a polynomial function of higher degrees.

[0022] It is further understood that the method may include, in order to determine the maximum flow rate setpoint, both consulting a pre-recorded database and performing a mathematical calculation from a predefined mathematical function, in particular by performing a mathematical calculation before or after consulting the database.

[0023] Thus, the determined maximum flow rate setpoint can be an output data from the pre-recorded database and / or a data calculated from the predefined mathematical function.

[0024] The method for determining a maximum flow rate setpoint may further include one or more of the following optional features, taken alone or in combination:

[0025] - The database may include discrete data or data Continuous data. "Discrete data" refers to data that can only take certain values; it comprises a limited number of values. "Continuous data" refers to data that can take all possible values ​​within an interval. For example, regarding the outside temperature, the database could include the discrete values ​​of -20°C, 0°C, 20°C, and 40°C, or continuous values ​​in the form of intervals such as: less than -20°C, [-20°C; 0°C], ]0°C; 20°C], ]20°C; 40°C], and greater than 40°C.

[0026] - When the maximum tank emptying flow rate setpoint is determined from of each of the three values ​​(Te, T;, P,) and a pre-recorded database, and when at least one of the three values ​​(Te, T;, P;) is absent from the pre-recorded database, the maximum tank emptying flow rate setpoint is determined by interpolating data present in the pre-recorded database.

[0027] Interpolation is defined as a mathematical method used to estimate values ​​from known data. It consists of estimating an intermediate value between two discrete values ​​using a mathematical model. The objective of interpolation is to find an approximation for data that are not explicitly present in the database but lie between the known values. Typically, interpolation is very well suited if the database contains discrete data. Thus, thanks to interpolation, even if a measured value is not explicitly indicated in the database, it is still possible to provide a maximum flow rate setpoint. The interpolation is, for example, linear interpolation. It is also possible to use polynomial or other types of interpolation. The approximate value obtained by interpolation is not While not a value present in the database, it helps maintain a temperature above the threshold temperature (Tmin) to prevent the tank from reaching a temperature that is too low and could damage the liner and / or the tank seals.

[0028] - When the maximum tank emptying flow rate setpoint is determined at starting from each of the three values ​​(Te, T;, P;) and a pre-recorded database having, as input, pre-recorded data (T'e, T'j, P'i) of temperature outside the tank, temperature inside the tank and pressure inside the tank, and, as output, corresponding data of maximum tank emptying flow setpoint, and that at least one of the three values ​​(Te, T;, P;) is absent from the pre-recorded database, the maximum tank emptying flow setpoint is determined by selecting in the pre-recorded database an output data corresponding to input data equal to or less than the temperature values ​​(Te, Tj) or input data equal to or greater than the pressure value (P;).

[0029] Thus, when a measured value is not present in the database, instead of interpolating to find an approximation of the missing data, the method selects a maximum flow rate value that corresponds to input data in the database that are equal to or directly less than the values ​​(Te, T;) for the temperature measured outside and inside the tank, particularly when the internal or external temperature values ​​are missing. When the pressure value inside the tank is missing, the method selects a maximum flow rate value that corresponds to input data in the database that are equal to or directly greater than the value (Pi) for the pressure measured inside the tank. Thus, the tank is considered to be in a more "critical" temperature and pressure state compared to its actual state, which is a safety measure.Indeed, the colder the tank, the closer the internal temperature is to the threshold temperature (Tmin). Considering a more critical state, the process determines a maximum flow rate setpoint that prevents the tank temperature from dropping too low. Even if the maximum flow rate value selected for the maximum flow rate setpoint is not optimal, it prevents the temperature inside the tank from falling below the threshold temperature (Tmin) in order to protect the liner and / or the tank seals from damage caused by excessively low temperatures.

[0030] - The step of measuring the temperature inside the tank is followed by a step correction to obtain a corrected indoor temperature value (Tic), so that the step of determining the maximum tank emptying flow rate setpoint is done based on: * the corrected indoor temperature value (Tic), * the temperature value (Te) measured outside the tank, and * the value (P;) of pressure measured inside the tank.

[0031] The invention thus proposes a correction step to correct the temperature measured inside the tank. Indeed, within the tank, the temperature may be distributed unevenly, such that the temperature reading taken by a temperature sensor may give inaccurate readings. Consequently, a correction step is provided to consider a more precise temperature that corresponds to the actual temperature inside the tank. This correction is particularly useful in the case of a hydrogen tank, because the cold gas tends to stagnate at the bottom of the tank and the warmer gas to rise. The temperature measured at the center of the tank therefore does not allow for determining the lowest temperature in the tank, and the correction makes it possible to take this local temperature variation into account.

[0032] - The correction step includes taking into account a correction margin, The correction margin varies depending on the measured indoor temperature (T), outdoor temperature (Te), and / or indoor pressure (Pi). Preferably, the correction margin varies depending on the measured indoor temperature (T), for example, between 0 and 30°C.

[0033] Thus, according to a first embodiment, a correction margin corresponding to a fixed value can be applied, which is systematically subtracted from the measured internal temperature (Ti). For example, the fixed value is between 15°C and 25°C, preferably close to 20°C. This fixed value is considered to account for the temperature difference between the center of the tank and the lower part, which receives the cooler gas. According to another embodiment, the correction margin is variable depending on the measured internal temperature (Ti) and is predefined; that is, the pre-recorded database includes pre-corrected internal temperature values.According to yet another embodiment, after measuring the internal temperature (Tj) and before determining the maximum emptying flow rate setpoint, a database is consulted, generally different from the one containing pre-recorded data, grouping as input data possible values ​​of temperature (Tj) measurable inside the tank and as output data, corresponding values ​​of corrected temperature (Tic).

[0034] - When the maximum tank emptying flow rate setpoint is determined at Starting from each of the three values ​​(Te, T, PO) and a pre-recorded database, the database includes pre-recorded discrete values ​​for the (Te) temperature values ​​measured outside the tank, and pre-recorded discrete values ​​for the (TO) temperature values ​​measured inside the tank, the discrete values ​​being spaced 20°C apart, preferably 10°C, preferably even 5°C apart. For example, the database includes at least the following discrete values ​​for the internal temperature (T): -20°C, 0°C, 20°C, 40°C, 60°C, 80°C.

[0035] - When the maximum tank emptying flow rate setpoint is determined from From each of the three values ​​(Te, T, P) and a pre-recorded database, the database includes pre-recorded discrete values ​​for the pressure values ​​(P) measured inside the tank, the discrete values ​​being spaced 50 bar apart, preferably 25 bar, and preferably 10 bar apart. For example, the database includes at least the following discrete values ​​for the internal pressure: 50, 150, 250, 350.

[0036] - When the maximum tank emptying flow rate setpoint is determined from From each of the three values ​​(Te, T, P) and a pre-recorded database, the database comprises at least two values ​​(Qmax), preferably at least five values ​​(Qmax), and preferably at least ten values ​​(Qmax). It is understood that these values ​​are distinct.

[0037] Advantageously, the database can include as many maximum discharge flow rate setpoint values ​​as there are different triplets for the parameters. Preferably, the database groups several distinct values ​​for temperatures outside the tank, temperatures inside the tank, and pressures inside the tank, along with a plurality of maximum flow rate values ​​related to the corresponding triplets. This makes it possible to limit the flow rate as closely as possible to the operator's needs and requirements, particularly for the proper management of the gas contained in the tank. Consequently, unlike the prior art, the performance of the device is optimized.

[0038] - The maximum tank emptying flow rate setpoint is determined in such a way periodic, preferably every 10 seconds, preferably even more so every second.

[0039] In other words, the maximum discharge flow rate setpoint is adjusted over time, which is particularly advantageous for optimizing resources. Thanks to this periodic determination, the maximum flow rate setpoint is regularly adapted. to prevent the temperature inside the tank from being too low without unduly limiting the performance of the device.

[0040] The invention also relates to a method for controlling the temperature of a pressurized gas tank for a mobile or stationary device during tank emptying, the tank emptying being controlled by a control system of the device for the purpose of using the gas by a gas consumption device, the control method comprising the following steps:

[0041] - implement the determination method as presented above,

[0042] - provide the value (Qmax) to the device's control system in order to control the tank emptying rate as a function of the value (Qmax).

[0043] The temperature control method may further include one or more of the following optional features, taken alone or in combination:

[0044] - The control system is a control system for a fuel cell of the device or any other control system integrated into the device.

[0045] - The gas consumption device is a fuel cell or an engine internal hydrogen combustion.

[0046] - The control system controls the tank emptying rate according to the value (Qmax) by limiting the tank emptying rate so as not to exceed the maximum tank emptying rate setpoint.

[0047] - The process is configured so that the temperature measured inside the tank remains above a predetermined threshold (Tmin), the predetermined threshold (Tmin) being between -35°C and -65°C, preferably close to -40°C.

[0048] The invention also relates to a computer program comprising instructions which, when the program is executed by a computer, lead the latter to implement the steps of the determination process as described above.

[0049] The invention also relates to a computer-readable recording medium comprising instructions which, when executed by a computer, lead the computer to implement the steps of the determination process as described above. Brief description of the figures

[0050] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the accompanying drawings in which:

[0051] [Fig-1] is a schematic view of a pressurized gas reservoir for the implementation of a method for determining a maximum discharge flow rate setpoint according to an embodiment;

[0052] [Fig.2] is a diagram illustrating a method for determining a maximum flow rate setpoint for emptying the tank of [Fig.1];

[0053] [Fig.3] is a diagram similar to that of [Fig.2] according to another embodiment,

[0054] [Fig.4a] is a diagram similar to that of [Fig.2] according to yet another embodiment; and

[0055] [Fig.4b] is a diagram illustrating a variant of the diagram in [Fig.4a]. Detailed description

[0056] Figure 2 illustrates the process 100 comprising the steps to determine a maximum flow rate setpoint for emptying a pressurized gas tank in order to control the temperature of the tank.

[0057] Such a method 100 is suitable for pressure vessels for mobile devices, such as vehicles, in particular electric or internal combustion vehicles, such as the tank 2 shown schematically in [Fig. 1]. The method 100 is also suitable for stationary devices, for example power plants or generator sets. For ease of reading, we describe below the case of a motor vehicle, but the invention is not limited to motor vehicles.

[0058] Such vehicles include pressurized tanks containing a gas, for example hydrogen (H2), to be injected into a gas consumption device, for example a fuel cell or a hydrogen internal combustion engine, for the movement or propulsion of the vehicle. The tank 2 generally includes, among other things, a gas distribution end 3, equipped with a relief valve. The valve, and therefore the gas injection, is advantageously controlled by a control system 4; this control system may, for example, be integrated into the vehicle's control unit or ECU (for "Electronic Control Unit").The tank 2 also includes, among other things, a temperature sensor 5 for measuring the temperature inside the tank and a pressure sensor 6 for measuring the pressure inside the tank. These sensors are mounted on a rod positioned along the axis of the tank, attached to an end 7, in this example opposite the end 3 which includes the valve. End 3 also includes, in this example, a temperature sensor 8 for measuring the temperature outside the tank, as well as an electronic unit 9 capable of receiving information from the measurements of sensors 5, 6, and 8. The electronic unit also includes a storage space for integrating a database and / or computing resources and for transmitting information to the control system 4.

[0059] The method 100 is particularly suitable for providing a maximum flow rate setpoint (Qmax) to the control system 4 in order to control the emptying flow rate of the tank 2 as a function of the value (Qmax). Advantageously, the flow rate control of The emptying process allows for the control of the temperature of tank 2, particularly the temperature inside the tank, which tends to drop during emptying. Controlling the internal temperature of the tank ensures its watertightness. In this example, the tank is a type IV tank and comprises an inner liner and an external reinforcement. The tank also includes sealing gaskets. Both the liner and the sealing gaskets are made of a polymer material that can degrade if subjected to very low temperatures, for example, between -35°C and -65°C, preferably -40°C. Process 100 allows for the determination of a maximum flow rate setpoint so that the temperature measured inside the tank remains above a predetermined threshold (Tmin).The predetermined threshold (Tmin) is between -35°C and -65°C, preferably close to -40°C to prevent the tank from reaching a temperature that is too low and could damage the liner and / or the tank seals.

[0060] To this end, and as illustrated in [Fig. 2], the method 100 comprises 10 measurement steps for: - measure the temperature outside the tank 2, using the sensor 8, and provide the electronic unit 9 with a temperature value (Te) measured outside the tank, - measure the temperature inside tank 2, using sensor 5, and provide electronic unit 9 with a value (TO) of the temperature measured inside the tank, - measure the pressure inside tank 2, using sensor 6, and provide electronic unit 9 with a value (P;) of the pressure measured inside the tank.

[0061] The measurement steps 10 are represented as a single block in [Fig. 1]. These measurements can be carried out simultaneously using sensors 5, 6, 8. Alternatively, the measurement steps 10 can be carried out consecutively, with or without a defined order.

[0062] These measurement steps 10 therefore provide a value (Te, T, P) for each measured parameter. Then, the method 100 includes a step 20 to determine, from each of these three values ​​(Te, T, P) and the electronic unit 9, more precisely from a pre-recorded database or a predefined mathematical function, a maximum tank emptying flow rate setpoint and a step 30 to provide this value (Qmax) of the maximum tank emptying flow rate setpoint to the control system 4.

[0063] Thus, it is understood that in step 20, to determine the maximum flow rate setpoint, advantageously sent to the control system 4, a pre-recorded database in unit 9 is consulted and / or this setpoint is calculated from the predefined mathematical function in unit 9.

[0064] According to one embodiment, step 20 for determining the maximum flow rate setpoint involves consulting a database. Preferably, the database contains data relating to the three parameters. In particular, it includes a plurality of pre-recorded input data, notably the temperature outside the tank T'e, the temperature inside the tank T'i, and the pressure inside the tank P'i. For the three types of pre-recorded values ​​(T'e, T'i, P'i), the term "triplet" is used in the following description. The database also includes output data corresponding to a maximum flow rate value (Qmax) for each pre-recorded triplet.

[0065] The following tables 1 to 4 present examples of tables illustrating a database that can be considered for step 20 to determine the maximum flow rate setpoint.

[0066] [Tables 1] T’ A e -20°C Q max T’j (°C) P’i (ba r) -20 0 20 40 60 80 50 1,98 2,70 2,70 2,70 2,70 2,70 150 0,36 2,34 2,70 2,70 2,70 2,70 250 0,36 0,54 2,70 2,70 2,70 2,70 350 0,36 0,36 0,54 2,70 2,70 2,70

[0067] [Tableaux2] T’ A e o°c Q max T’i (°C) P’i (ba r) -20 0 20 40 60 80 50 2,16 2,70 2,70 2,70 2,70 2,70 150 1,08 2,70 2,70 2,70 2,70 2,70 250 0,90 1,44 2,70 2,70 2,70 2,70 350 0,72 0,90 1,98 2,70 2,70 2,70

[0068] [Tableaux3] T’ A e 20°C Q max T’j (°C) P’i (ba r) -20 0 20 40 60 80 50 2,34 2,70 2,70 2,70 2,70 2,70 150 1,44 2,70 2,70 2,70 2,70 2,70 250 1,26 2,16 2,70 2,70 2,70 2,70 350 1,26 1,62 2,70 2,70 2,70 2,70

[0069] [Tableaux4] T’ A e 40°C Q max T’i (°C) P’i (ba r) -20 0 20 40 60 80 50 2,52 2,70 2,70 2,70 2,70 2,70 150 1,98 2,70 2,70 2,70 2,70 2,70 250 1,80 2,70 2,70 2,70 2,70 2,70 350 1,80 2,34 2,70 2,70 2,70 2,70

[0070] As shown in Tables 1 to 4, each table in the database includes pre-recorded input data (T'e, T'i, P'i), which allow for the definition of a large number of different triplets. For example, referring to Table 1, it allows for the definition of triplets all comprising an outside temperature T'e of -20°C, an inside temperature T'i, and an inside pressure P'i. The database also includes pre-recorded output data corresponding to a maximum flow rate value (Qmax) for each pre-recorded triplet. The database includes at least two values ​​(Qmax), preferably at least five values ​​(Qmax), and preferably at least ten values ​​(Qmax). Advantageously, the database can include as many values ​​as there are different triplets for the parameters.

[0071] In particular, in the example here, each table in the database contains pre-recorded discrete values ​​for the temperature values ​​(T'e) outside the tank. Thus, for example, when the temperature value (Te) measured outside the tank is -20°C, the database in Table 1 is consulted. in order to perform step 20 to determine the maximum flow rate setpoint. Similarly, if the value (Te) of the temperature measured outside the tank is 20°C, the database in Table 3 is consulted.

[0072] Each table further includes pre-recorded discrete values ​​for the temperature values ​​(T'i) inside the tank, the discrete values ​​being spaced 20°C apart. As can be seen in the tables, the database includes the following discrete values ​​for the internal temperature: -20°C, 0°C, 20°C, 40°C, 60°C, 80°C. Of course, the tables represent an example of a database; it is possible to provide a database in which the discrete values ​​are spaced differently from each other, for example, 10°C apart, or even 5°C apart.

[0073] In addition, each table includes pre-recorded discrete values ​​for the pressure values ​​(P';) inside the tank, the discrete values ​​being spaced 50 bar apart, preferably 25 bar, and even more preferably 10 bar apart. In the examples in Tables 1 to 4, the tables include the following discrete values ​​for the internal pressure: 50, 150, 250, 350.

[0074] Therefore, after the measurement steps 10, the method 100 allows a database to be consulted according to the input data, i.e. according to the three measured values ​​(Te, T;, P;).

[0075] Alternatively, according to another embodiment, the process may not consult the database and perform a mathematical calculation based on the predefined mathematical function in the electronic unit 9, after the measurement steps 10. Preferably, the mathematical function is of the type f(Te, T, P). In one embodiment, f is a polynomial function, for example f(Te, Ti, Pi) = aT + bTe + cPi, where a, b, and c are three real numbers depending on parameters of the tank 2, for example, the tank volume, the tank wall thickness, or the tank operating pressure.

[0076] The maximum flow rate values ​​(Qmax) indicated in the database can be obtained beforehand from limit flow rates identified experimentally, or can be obtained by numerical simulation.

[0077] Advantageously, step 20 for determining the maximum tank emptying flow rate setpoint is performed periodically, preferably every 10 seconds, or even more preferably every second. This periodic determination allows the maximum flow rate setpoint to be adjusted regularly to prevent the temperature inside the tank from becoming too low without unduly limiting vehicle performance.

[0078] Figure 3 illustrates a diagram of process 100 according to another embodiment. Process 100 here also includes measurement steps 10, step 20 for determining the maximum flow rate setpoint, and step 30 for providing a maximum flow rate setpoint value (Qmax). Furthermore, process 100 here includes a correction step 40 to obtain a corrected internal temperature value (Tic), such that step 20 for determining the maximum tank emptying flow rate setpoint is based on: - the corrected indoor temperature value (Tic), - the temperature value (Te) measured outside the tank, and - the pressure value (P;) measured inside the tank.

[0079] The invention proposes a correction step 40 to correct the temperature measured inside the tank. Indeed, within the tank, the temperature may be distributed unevenly, such that the temperature measured by the temperature sensor 5 does not correspond to the actual temperature at the liner or the tank seals. Therefore, this correction step 40 is intended to estimate a temperature that more closely matches the actual temperature at the liner or the tank seals, or at least to estimate a minimum temperature inside the tank, that is, a minimum temperature at which a portion of the liner or the seals can actually be found.

[0080] Preferably, the correction step 40 is carried out before the step 20 to determine the maximum flow setpoint, i.e. before consulting the database or before performing the mathematical calculation to obtain the value of the setpoint (Qmax) of the maximum flow.

[0081] The correction step 40 preferably includes taking into account a correction margin, the correction margin being variable depending on the measured internal temperature (T;), the measured external temperature (Te) and / or the measured internal pressure (P;). Preferably, the correction margin is variable depending on the measured internal temperature (T;), the correction margin varying, for example, between 0 and 30°C.

[0082] According to a first example, for correction step 40, a correction margin is applied, corresponding to a fixed value that is systematically subtracted from the measured indoor temperature (Tj). For example, the fixed value is between 15°C and 25°C, preferably close to 20°C. According to a second example, the correction margin varies according to the measured indoor temperature (Tj) and is predefined; that is, the pre-recorded database includes pre-corrected indoor temperature values. According to this second For example, we can consider that there is no specific correction step 40 and that the process in [Fig.2] applies. According to a third example, after the measurement 10 of the internal temperature (TO) and before the determination 20 of the maximum emptying flow rate setpoint, another database is consulted, grouping as input possible temperature values ​​(T;) measurable inside the tank and as output, corresponding corrected temperature values ​​(Tic).

[0083] Figures 4a and 4b each represent an embodiment of process 100 where, in step 20 for determining the maximum flow rate setpoint, the database is consulted and one of the values ​​(Te, T, P) measured in measurement steps 10 is absent from this database. As explained above, particularly in the examples in Tables 1 to 4, the database comprises discrete values ​​that are spaced apart. It is possible, even probable, that during measurement steps 10, one of the parameters includes a decimal value, and therefore this value will not be found in the database. It is also possible that a discrete value is measured, but that this value is not in the database; for example, a temperature value (TO) inside the tank is measured at 13°C, but this value is not in the pre-recorded input data.

[0084] According to an embodiment illustrated in [Fig. 4a], the method 100 includes a test step 50 to determine whether the values ​​(Te, T, P) provided after the measurement steps 10, and optionally the correction step 40 when applicable, are present in the database. If all the values ​​(Te, T, P) are found in the database, then the process proceeds to step 20 to determine the maximum flow rate setpoint. Conversely, if at least one of the values ​​(Te, T, P) is absent from the database, the process proceeds to a step 60 of interpolation of the data present in the pre-recorded database. Interpolation 60 consists of estimating an intermediate value between two discrete data points using a function or a mathematical model. Interpolation 60 allows us to find an approximation for the missing value which is not explicitly provided in the database, and which lies between the known values.Thus, after interpolation 60, a value (Qmax) of the maximum flow rate setpoint is provided.

[0085] According to an alternative embodiment illustrated in [Fig. 4b], when at least one of the three values ​​(Te, Ti, Pi) is absent from the pre-recorded database, test step 50 is followed by a step 70 of selecting, from the pre-recorded database, an output data point corresponding to input data points equal to or less than each of the two values ​​(Te, Ti), with regard to the temperature measured outside and inside the tank, and equal to or greater than the value (Pi), with regard to the pressure measured inside the tank. For example, if the value If the temperature (Ti) inside the tank, or the corrected value (Tic), is 13°C in Table 1, selection 70 considers this value to be 0°C. Considering temperature values ​​equal to or lower than the two measured values ​​(Te, Ti) and pressure values ​​equal to or greater than the measured value (Pi), the tank is considered to be in a "more critical" temperature and pressure state compared to its actual state. This constitutes a safety measure to limit the flow rate and prevent an excessive drop in tank temperature. While this flow rate limitation will be slightly greater than necessary, it will protect the tank liner and seals from damage due to excessively low temperatures, all while using a simple database.

[0086] Finally, the invention also relates to a computer program comprising instructions which, when the program is executed by a computer, lead the computer to implement the steps of a process as described above, as well as a computer-readable recording medium comprising instructions which, when executed by a computer, lead the computer to implement the steps of a process as described above.

[0087] The invention is not limited to the embodiments presented, and other embodiments will be obvious to those skilled in the art. In particular, it is possible to provide databases whose values ​​are continuous and defined by intervals. It is also possible to provide a function other than a polynomial function for determining the maximum flow rate setpoint. List of references

[0088] 2: reservoir 3: gas distribution end 4: Control system 5: Temperature sensor 6: Pressure sensor 7: opposite end to end 3 8: Temperature sensor 9: electronic unit 10: Measurement steps 20: Step to determine the maximum flow rate setpoint 30: Step of providing a maximum flow rate setpoint value (Qmax) 40: Correction step 50: Test step on the presence of the values ​​(Te, T, P) in the database 60: Interpolation step 70: step of selecting from the database an output data corresponding to input data equal to or less than the two values ​​(Te, Ti) for the temperature measured outside and inside the tank, and equal to or greater than the value (P;) for the pressure measured inside the tank 100: Method for determining a maximum flow rate setpoint for emptying a pressurized gas tank

Claims

Demands

1. A method (100) for determining a maximum discharge flow rate setpoint for a pressurized gas tank for a mobile or stationary device for controlling the temperature of the tank during its discharge, the method of determination comprising the following steps: - measuring the temperature outside the tank and providing a value (Te) of the temperature measured outside the tank, - measuring the temperature inside the tank and providing a value (TO) of the temperature measured inside the tank, - measuring the pressure inside the tank and providing a value (Pi) of the pressure measured inside the tank, - determining (20), from each of these three values ​​(Te, 1), P;) and i) from a pre-recorded database and / or ii) from a predefined mathematical function, a maximum discharge flow rate setpoint for the tank and providing (30) a value (Qmax) of the maximum discharge flow rate setpoint for the tank.

2. Method (100) of determination according to claim 1, wherein when the maximum tank emptying flow rate setpoint is determined from each of the three values ​​(Te, T), P;) and a pre-recorded database, and when at least one of the three values ​​(Te, T), P;) is absent from the pre-recorded database, the maximum tank emptying flow rate setpoint is determined by interpolation (60) of data present in the pre-recorded database.

3. A method (100) for determining the maximum tank emptying flow rate setpoint according to claim 1, wherein, when the maximum tank emptying flow rate setpoint is determined from each of the three values ​​(Te, T, P) and a pre-recorded database having, as input, pre-recorded data (T'e, T'i, P'i) for temperature outside the tank, temperature inside the tank, and pressure inside the tank, and, as output, corresponding data for the maximum tank emptying flow rate setpoint, and at least one of the three values ​​(Te, T, P) is absent from the pre-recorded database, the maximum tank emptying flow rate setpoint is determined. reservoir by selection (70) in the pre-recorded database of an output data corresponding to input data equal to or less than the temperature values ​​(Te, T)) or input data equal to or greater than the pressure value (P;).

4. A method (100) for determining according to any one of the preceding claims, wherein the step of measuring the temperature inside the tank is followed by a correction step (40) to obtain a corrected internal temperature value (Tic), such that the step of determining the maximum tank emptying flow rate setpoint is made from: - the corrected internal temperature value (Tic), - the temperature value (Te) measured outside the tank, and - the pressure value (P;) measured inside the tank.

5. Method (100) of determination according to the preceding claim, wherein the correction step (40) includes taking into account a correction margin, the correction margin being variable depending on the measured internal temperature (T;), the measured external temperature (Te) and / or the measured internal pressure (P;).

6. A method (100) for determining according to any one of the preceding claims, wherein when the maximum tank emptying flow rate setpoint is determined from each of the three values ​​(Te, T;, P;) and a pre-recorded database, the database includes pre-recorded discrete values ​​for the (Te) temperature values ​​measured outside the tank, and pre-recorded discrete values ​​for the (TO) temperature values ​​measured inside the tank, the discrete values ​​being spaced from each other by 20°C, preferably by 10°C, preferably even more by 5°C.

7. Method (100) of determination according to any one of the preceding claims, wherein when the maximum tank discharge flow setpoint is determined from each of the three values ​​(Te, T;, P;) and a pre-recorded database, the database includes pre-recorded discrete values ​​for the (P;) pressure values ​​measured inside the tank, the discrete values ​​being spaced 50 bar apart, preferably 25 bar, preferably still 10 bar.

8. Method (100) of determination according to any one of the preceding claims, wherein when the maximum tank emptying flow rate setpoint is determined from each of the three values ​​(Te, 1), P;) and a pre-recorded database, the database includes at least two values ​​(Qmax), preferably at least five values ​​(Qmax), preferably still at least ten values ​​(Qmax).

9. Method (100) of determination according to any one of the preceding claims, wherein the maximum tank emptying flow rate setpoint is determined periodically, preferably every 10 seconds, preferably even more every second.

10. Method for controlling the temperature of a pressurized gas tank for a mobile or stationary apparatus during tank emptying, the tank emptying being controlled by an apparatus control system for the purpose of using the gas by a gas consumption device, the control method comprising the following steps: - implementing the determination method (100) according to any one of the preceding claims, - providing the value (Qmax) to the apparatus control system in order to control the tank emptying rate as a function of the value (Qmax).

11. A control method according to the preceding claim, configured so that the temperature measured inside the tank remains above a predetermined threshold (Tmin), the predetermined threshold (Tmin) being between -35°C and -65°C, preferably close to -40°C.

12. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of a process as claimed in any of the preceding claims.

13. A computer-readable recording medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of a process as claimed in any one of claims 1 to 11.

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