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

Abstract

The invention relates to a method for determining a maximum flow rate setpoint for emptying a pressurised gas tank for a mobile or stationary apparatus with a view to controlling the temperature of the tank during the emptying thereof, the determination method comprising the following steps: - measuring the temperature outside the tank and providing a value (Te) for the temperature measured outside the tank, - measuring the temperature inside the tank and providing a value (Ti) for the temperature measured inside the tank, - measuring the pressure inside the tank and providing a value (Pi) for the pressure measured inside the tank.

Description

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 machinery (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 into one of the following five types: a type I pressurized gas tank with an all-metal construction; a type II pressurized gas tank with a metal construction including a fiber winding for reinforcement of its cylindrical part; a type III pressurized gas tank with a metal liner with a composite reinforcement structure; a type IV pressurized gas tank with a plastic liner with a composite reinforcement structure; and a type V pressurized gas tank with a composite reinforcement structure and no liner.

[0003] The existing technology already exists for 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). This pressurized gas tank is configured for use by a vehicle equipped with a 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, for example, consists of an external composite reinforcement structure to increase the tank's rigidity and an internal liner, which provides a seal against the gas inside. The liner is typically made of plastic in the case of a Type IV tank, chosen for its lightness and low manufacturing cost. Alternatively, the liner can be made of metal 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 internal combustion engine, the temperature inside the tank tends to drop due to adiabatic expansion. More specifically, for example in a hydrogen tank, when the tank valve is opened to release the gas, its pressure decreases.As a result, 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 seals inside the tank to degrade. The liner and seals are each made of a polymer material that can degrade at very low temperatures. Their degradation can compromise the tank's seal and therefore cause a leak. Furthermore, safety inside the vehicle is also at risk because 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 discharge rate in order to protect the liner and seals of a hydrogen tank. Documents DE102018121267 and JP5804751B2 describe, in a relatively similar manner, determining a temperature inside the tank in order to compare it to a threshold temperature and reduce or not the release of fluid.

[0007] It is also known from document EP4159995 that a control system is provided to manage the emptying of a hydrogen tank in a way that protects the liner. This system is configured to control the emptying rate by estimating, during the operation of an accelerator, the temperature reached in the tank after a certain time has elapsed with maximum acceleration. Once this temperature is estimated, the control system can limit the emptying rate to maintain it below a predetermined maximum flow rate. For this estimation, the temperature measured inside the tank is considered, generally near the tank's central axis. However, this measurement is known to have a number of inaccuracies.Indeed, in addition to the temperature drop due to pressure reduction within the tank, the temperature outside the tank (or ambient temperature) can significantly impact the temperature inside the tank, primarily due to the natural heat exchange that occurs 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 cooler gas tends to settle at the bottom of the tank, while the warmer gas rises.Thus, depending on its placement within the tank, the temperature sensor may not accurately measure the internal temperature, resulting in a relatively rough estimate of the temperature drop. As a precaution, the tank emptying rate may be unduly limited 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. Therefore, the flow rate may be limited even if the acceleration was not as significant, and consequently, the temperature did not decrease as much as estimated.

[0008] 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 seal without unnecessarily reducing the vehicle's performance.

[0009] 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:

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

[0011] - measure the temperature inside the tank and provide a value (T i) of temperature measured inside the tank,

[0012] - measure the pressure inside the tank and provide a value (P i ) of pressure measured inside the tank,

[0013] - determine, from each of these three values ​​(T e , T i , P i ) eti) from a pre-recorded database and / or ii) from a predefined mathematical function, a maximum flow rate setpoint (Q max ) of emptying the tank and provide this maximum flow rate setpoint (Q max ) of emptying the tank.

[0014] Thus, the invention proposes to consider three distinct parameters to determine a maximum emptying flow rate setpoint 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 being the temperature measured outside (T e) of the tank, the temperature measured inside (T i ) of the tank and the pressure measured inside (P i ) of the reservoir. The term "triplet" will be used in the following to refer to these three parameters or values.

[0015] In particular, by considering the temperature outside the tank, the process takes into account the influence of ambient temperature on the internal temperature of the tank during emptying. This allows for more precise estimates of the temperature reached at the liner or tank seals, thus enabling a more accurate determination of the maximum flow rate setpoint (Q). max ) of emptying the tank. By "maximum flow rate setpoint (Q maxThe term "maximum flow rate setpoint" refers both to a mathematical value (i.e., a number) corresponding to the determined maximum flow rate and / or to a computer data point representing this mathematical value, the computer data being provided at the end of the process, typically to a control system for the device. In this description, the terms "maximum flow rate setpoint," "maximum flow rate setpoint value," and "maximum flow rate value" are used interchangeably.

[0016] It is understood that the maximum flow rate setting can subsequently be taken into account by a control system of the device in order to reduce, if necessary, the gas injection into a component of the device, and therefore the discharge rate. By "mobile devices," we mean, for example, 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.) and by "stationary devices," we mean, for example, power plants or generator sets.

[0017] 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.

[0018] Advantageously, the maximum flow rate setpoint (Q max ) is a mass flow rate value expressed in g / s (grams per second). Furthermore, preferably, the maximum flow rate setpoint (Q max ) corresponds to an average flow rate, not an instantaneous flow rate. By "average flow rate," we mean a flow rate at which the tank can be emptied to a predetermined pressure without exceeding a predetermined temperature threshold (T min ) inside the tank.

[0019] Considering the three parameters (T e , T i , P i ), a maximum flow rate setpoint (Q max) is determined in order to provide this value to a control system of the device. Advantageously, this value corresponds to a flow rate limit value so that the temperature inside the tank at the level of a liner or seals always remains above a predetermined threshold (T min This threshold temperature corresponds to the temperature limit that a liner and / or seals can withstand without suffering damage. By controlling the maximum drainage flow rate (Q max Therefore, it is possible to control the temperature inside the tank, which varies. This allows for a particularly advantageous determination of the maximum flow rate, thus better controlling the temperature inside the tank and preventing damage to the liner and / or seals.

[0020] A "tank" is defined as a fluid storage volume that can be divided into several sub-volumes, which may be identical or different. Each fluid storage sub-volume can be stored in a separate container. The proposed process is particularly advantageous for a Type IV tank, which includes a liner and seals made of polymer materials. However, this process is not limited to Type IV tanks and may also be suitable for other tank types, such as Type I, II, III, and V tanks, which include seals made of materials that may not withstand very low temperatures, for example, temperatures between -35°C and -65°C.

[0021] Furthermore, by more accurately determining the maximum flow rate, it is also possible to better manage the amount of gas exiting the tank, thus avoiding unnecessary reductions in the device's performance. In particular, unlike the prior art, the maximum flow rate setpoint here is not determined by assuming the device is under maximum load for a specified period. On the contrary, according to the invention, the estimates are based primarily on measurements taken inside and around the tank to best estimate the temperature within the tank at the level of the liner or seals, and to allow, as far as possible, a discharge rate that matches the actual demand of the device operator.It is clear that defining a maximum flow rate target to be subsequently supplied to the device's control system is particularly advantageous, unlike existing methods that reduce the fluid extraction rate after the tank temperature exceeds a certain threshold. Indeed, a simple instruction to reduce the flow rate does not specify by what percentage, nor when and to what extent it can be increased again. In contrast, indicating a maximum flow rate allows the tank to be emptied under the most efficient conditions possible and avoids unnecessarily reducing emptying performance.

[0022] To determine the maximum flow rate setpoint, the process initially involves consulting a pre-recorded database. Preferably, the database contains multiple possible data points for each of the three measured parameters. Once each parameter is measured, that is, once each of the three T values ​​is determined, the process is performed. e , T i , P i is known, the database is consulted to determine an optimal maximum flow rate value with regard to the three measured values ​​T e , T i , P iIn other words, the pre-recorded database is constructed using 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.

[0023] Alternatively, the process could 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 form f(T e , T i , P i ) and f is a polynomial function. According to a relatively simple example, the function f is an affine function of the form f(T e , T i , P i ) = aT i + bT e + cP i where a, b, and c are three real numbers dependent on parameters of the tank, such as the tank volume, the tank wall thickness, or the tank's operating pressure. In more complex examples, the function f is a polynomial function of higher degrees.

[0024] It is also understood that the process 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.

[0025] 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.

[0026] 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:

[0027] – The database can contain discrete or continuous data. Discrete data refers to data that can only take certain values; it includes 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 can 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.

[0028] - When the maximum flow rate setpoint (Q max The tank emptying point is determined from each of the three values ​​(T e , T i , P i ) and a pre-recorded database, and when at least one of the three values ​​(T e , T i , P iIf the value is absent from the pre-recorded database, the maximum flow rate setpoint (Q) is determined. max ) of emptying the tank by interpolating data present in the pre-recorded database.

[0029] Interpolation is a mathematical method used to estimate values ​​from known data. It involves estimating an intermediate value between two discrete values ​​using a mathematical model. The goal of interpolation is to find an approximation for data that is not explicitly present in the database but lies between known values. Typically, interpolation is well-suited to databases containing discrete data. Thus, thanks to interpolation, even if a measured value is not explicitly recorded in the database, it is still possible to provide a maximum flow rate target. Examples of interpolation include linear interpolation. Polynomial and other types of interpolation are also possible.The approximate value obtained by interpolation is certainly not a value present in the database, but it allows us to maintain a temperature above the threshold temperature (T. min ) to prevent the tank from reaching a temperature that is too low and could damage the liner and / or the tank seals.

[0030] - When the maximum flow rate setpoint (Q max The tank emptying point is determined from each of the three values ​​(T e , T i , P i ) and a pre-recorded database having pre-recorded data as input (T' e , T' i , P' i ) temperature outside the tank, temperature inside the tank and pressure inside the tank, and, at the outlet, the corresponding maximum flow setpoint data (Q max ) of emptying the tank, and that at least one of the three values ​​(T e , Ti , P i If the value is absent from the pre-recorded database, the maximum flow rate setpoint (Q) is determined. max ) of emptying the tank by selecting from the pre-recorded database an output data corresponding to input data equal to or less than the temperature values ​​(T e , T i ) or input data equal to or greater than the pressure value (P i ).

[0031] Thus, when a measured value is not present in the database, instead of performing interpolation to find an approximation of the missing data, the process selects a maximum flow rate value that corresponds to input data in the database that are equal to or directly less than the values ​​(T e , T i), regarding 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 process provides for selecting a maximum flow rate value that corresponds to input data in the database that are equal to or directly greater than the value (P i ), regarding 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 (T minConsidering 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 (T). min ) in order to protect the liner and / or the tank seals against damage caused by excessively low temperatures.

[0032] - The step of measuring the temperature inside the tank is followed by a correction step to obtain a value (T ic ) of corrected indoor temperature, so that the step of determining the maximum flow rate setpoint (Q max The tank emptying rate is calculated from: * the value (T ic ) of corrected indoor temperature,* the value (T e) of temperature measured outside the tank, and* the value (P i ) of pressure measured inside the tank.

[0033] 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 or homogeneously, such that the temperature reading taken by a temperature sensor may be inaccurate. 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 relevant in the case of a hydrogen tank. In fact, cold gas tends to stagnate at the bottom of the tank, while warmer gas tends to rise, primarily due to a phenomenon called gas stratification, or in the case of a hydrogen tank, hydrogen stratification. Therefore, the temperature measured at the center of the tank does not allow for the determination of the lowest temperature within the tank.Due to this uncertainty, the temperature is advantageously corrected to account for this local temperature variation. This correction preferably allows for estimating the minimum temperature inside the tank, based on tests or simulations.

[0034] - The correction step includes taking into account a correction margin, the correction margin being variable depending on the indoor temperature (T i measured, of the outside temperature (T e ) measured and / or internal pressure (P i ) measured. Preferably, the correction margin is variable depending on the indoor temperature (T i ) measured, the correction margin varying for example between 0 and 30°C.

[0035] Advantageously, temperature correction is assumed in order to estimate the minimum temperature. Thus, according to a first embodiment, a correction margin corresponding to a fixed value can be applied and systematically subtracted from the measured internal temperature (T). i For example, the fixed value is between 15°C and 25°C, preferably close to 20°C. This fixed value is estimated to account for the temperature difference between the center of the tank and the lower part, which receives the cooler gas. In another embodiment, the correction margin varies depending on the internal temperature (T i ) measured and is predefined, that is, the pre-recorded database includes pre-corrected indoor temperature values. According to yet another embodiment, after the indoor temperature (T) is measured i) and before determining the maximum discharge flow rate setpoint, a database is consulted, generally different from the one containing pre-recorded data, grouping possible temperature values ​​(T) as input data i ) measurable inside the tank and in output data, corresponding corrected temperature values ​​(T ic ).

[0036] - When the maximum flow rate setpoint (Q max The tank emptying point is determined from each of the three values ​​(T e , T i , P i ) and a pre-recorded database, the database includes pre-recorded discrete values ​​for the values ​​(T e ) of temperature measured outside the tank, and pre-recorded discrete values ​​for the (T) values i) of temperature measured inside the tank, the discrete values ​​being spaced 20°C apart, preferably 10°C, and even more preferably 5°C apart. For example, the database includes at least the following discrete values ​​for the internal temperature (T i ): -20°C, 0°C, 20°C, 40°C, 60°C, 80°C.

[0037] - When the maximum flow rate setpoint (Q max The tank emptying point is determined from each of the three values ​​(T e , T i , P i ) and a pre-recorded database, the database includes pre-recorded discrete values ​​for the values ​​(P i ) of pressure measured inside the tank, the discrete values ​​being spaced 50 bar apart, preferably 25 bar, preferably even more 10 bar. For example, the database includes at least the following discrete values ​​for the internal pressure: 50, 150, 250, 350.

[0038] - When the maximum flow rate setpoint (Q max The tank emptying point is determined from each of the three values ​​(T e , T i , P i ) and a pre-recorded database, the database includes at least two maximum flow rate setpoint values ​​(Q max ), preferably at least five values ​​(Q max ), preferably at least ten more values ​​(Q max ). We understand that these values ​​are distinct values.

[0039] Advantageously, the database can include as many maximum discharge flow rate setpoint values ​​as there are different parameter triplets. Preferably, the database includes several distinct values ​​for external tank temperatures, internal tank temperatures, and internal tank pressures, along with a plurality of maximum flow rate values ​​associated with the corresponding triplets. This allows the flow rate to be limited 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 prior art, the equipment's performance is optimized.

[0040] - The maximum flow rate setpoint (Q) max ) of emptying the tank is determined periodically, preferably every 10 seconds, preferably even more so every second.

[0041] In other words, the maximum emptying flow rate setting is adjusted over time, which is particularly useful for optimizing resources. Thanks to this periodic adjustment, the maximum flow rate setting is regularly adapted to prevent the temperature inside the tank from dropping too low without unduly limiting the appliance's performance.

[0042] 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:

[0043] - to implement the determination procedure as presented above,

[0044] - provide the maximum flow rate setpoint (Q) max) to the device's control system in order to control the tank emptying rate according to the maximum flow rate setpoint (Q max ).

[0045] The temperature control method may further include one or more of the following optional features, taken alone or in combination:

[0046] - The control system is a control system for a fuel cell of the device or any other control system integrated into the device.

[0047] - The gas consumption device is a fuel cell or a hydrogen internal combustion engine.

[0048] – The control system regulates the tank emptying rate according to the value (Q max ) by limiting the tank emptying rate so as not to exceed the maximum tank emptying rate setpoint.

[0049] - The process is configured so that the temperature measured inside the tank remains above a predetermined threshold (T min ), the predetermined threshold (T min ) being between -35°C and -65°C, preferably close to -40°C.

[0050] 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 the determination process as described above.

[0051] 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

[0052] The invention will be better understood upon reading the following description, given solely by way of example and with reference to the accompanying drawings in which:

[0053] is a schematic view of a pressurized gas tank for the implementation of a method for determining a maximum discharge flow rate setpoint according to an embodiment;

[0054] is a diagram illustrating a method for determining a maximum flow rate setpoint for emptying the tank of the;

[0055] is a diagram similar to that of the latter, according to another embodiment,

[0056] is a diagram similar to that of the latter, yet another embodiment; and

[0057] is a diagram illustrating a variant of the diagram of the. Detailed description

[0058] We have illustrated on the process 100 including the steps to determine a maximum flow rate setpoint for emptying a pressurized gas tank in order to control the temperature of the tank.

[0059] Such a method 100 is suitable for pressure vessels for mobile devices, such as vehicles, particularly electric or internal combustion engine vehicles, such as tank 2 shown schematically in Figure 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.

[0060] 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 vehicle's movement or propulsion. 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 can, 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 and attached to an end 7, which in this example is opposite the end 3 containing 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 storage space for integrating a database and / or computing resources and for transmitting information to the control system 4.

[0061] Process 100 is particularly suitable for providing a maximum flow rate setpoint (Q max) to the control system 4 in order to control the emptying rate of the tank 2 according to this setpoint (Q maxAdvantageously, controlling the discharge flow rate allows for control of the temperature of tank 2, particularly the temperature inside the tank, which tends to drop during discharge. Controlling the internal temperature of the tank ensures its watertightness. Indeed, 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. The liner and the sealing gaskets are each 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. The 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 (T). min The predetermined threshold (T min) 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.

[0062] To do this, and as illustrated in Figure 1, the process 100 comprises 10 measurement steps to: - measure the temperature outside the tank 2, using the sensor 8, and provide the electronic unit 9 with a value (T e ) of temperature measured outside the tank, - measure the temperature inside tank 2, using sensor 5, and provide the electronic unit 9 with a value (T i ) of temperature measured inside the tank, - measure the pressure inside tank 2, using sensor 6, and provide the electronic unit 9 with a value (P i ) of pressure measured inside the tank.

[0063] The 10 measurement steps are represented as a single block on the diagram. These measurements can be carried out simultaneously using sensors 5, 6, and 8. Alternatively, the 10 measurement steps can be carried out consecutively, with or without a defined order.

[0064] These 10 measurement steps therefore plan to provide a value (T e , T i , P i ) for each measured parameter. Then, process 100 includes a step 20 to determine, from each of these three values ​​(T e , T i , P i ) and electronic unit 9, more precisely from a pre-recorded database or a predefined mathematical function, a maximum flow rate setpoint (Q max ) of emptying the tank and a step 30 to provide this instruction (Q max ) of maximum discharge flow rate from tank 2 to control system 4.

[0065] Thus, we understand 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.

[0066] In one embodiment, step 20 for determining the maximum flow rate setpoint includes 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 , of the temperature inside the tank T' i , and the pressure inside the tank P' i For the three types of values ​​(T' e , T' i , P' i), pre-recorded, the term "triplet" is used in the following description. The database also includes output data corresponding to a maximum throughput value (Q max ) for each pre-recorded triplet.

[0067] Tables 1 to 4 below present examples of tables illustrating a database that can be considered for step 20 to determine the maximum flow rate setpoint.

[0068] T' e -20°CQ max T' i (°C)P' i (bar)-20020406080501,982,702,702,702,702,701500,362,342,702,70 2,702,702500,360,542,702,702,702,703500,360,360,542,702,702,70

[0069] T' e 0°CQ max T' i (°C)P' i (bar)-20020406080502,162,702,702,702,702,701501,082,702,702,70 2,702,702500,901,442,702,702,702,703500,720,901,982,702,702,70

[0070] T' e 20°CQ max T' i (°C)P' i(bar)-20020406080502,342,702,702,702,702,701501,442,702,702,70 2,702,702501,262,162,702,702,702,703501,261,622,702,702,702,70

[0071] T' e 40°CQ max T' i (°C)P' i (bar)-20020406080502,522,702,702,702,702,701501,982,702,702,70 2,702,702501,802,702,702,702,702,703501,802,342,702,702,702,70

[0072] As can be seen in Tables 1 to 4, each table in the database includes pre-recorded input data (T' e , T' i , P' i ), which allow us to define a large number of different triplets. For example, if we refer to Table 1, it allows us to define triplets all containing an outside temperature T' e of -20°C, an internal temperature T' i and an internal pressure P' i The database also includes pre-recorded output data corresponding to a maximum flow rate value (Q). max) for each pre-recorded triplet. The database includes at least two values ​​(Q max ), preferably at least five values ​​(Q max ), preferably at least ten more values ​​(Q max Advantageously, the database can contain as many values ​​as there are different triplets for the parameters.

[0073] In particular, in this example, each database table includes pre-recorded discrete values ​​for the values ​​(T' e ) of the temperature outside the tank. Thus, for example, when the value (T e If the temperature measured outside the tank is -20°C, the database in Table 1 is consulted to perform step 20 to determine the maximum flow rate setpoint. Similarly, if the value (T e ) of the temperature measured outside the tank is 20°C, the database in table 3 is consulted.

[0074] Each table also includes pre-recorded discrete values ​​for the values ​​(T' i The database contains the following discrete values ​​for the internal temperature of the tank: -20°C, 0°C, 20°C, 40°C, 60°C, and 80°C. Of course, the tables represent an example of a database; it is possible to create a database in which the discrete values ​​are spaced differently, for example, 10°C or 5°C apart.

[0075] In addition, each table includes pre-recorded discrete values ​​for the values ​​(P' i) of pressure 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.

[0076] Therefore, after the 10 measurement steps, process 100 allows consulting a database based on the input data, that is, based on the three values ​​(T e , T i , P i ) measured.

[0077] 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(T e , T i , P iIn one embodiment, f is a polynomial function, for example f(Te, Ti, Pi) = aT i + bT e+ c.Pioù a, b et c sont trois réels dépendants de paramètres du réservoir 2, par exemple du volume du réservoir, de l’épaisseur de la paroi du réservoir, ou encore de la pression de service du réservoir.

[0078] Maximum flow rate values ​​(Q max ) indicated in the database can be obtained beforehand from limit flows identified experimentally, or can be obtained by numerical simulation.

[0079] Advantageously, step 20, which determines 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.

[0080] Laillustrates a diagram of process 100 according to another embodiment. Process 100 here also includes 10 measurement steps, and step 20 to determine the maximum flow rate setpoint (Q max ) and step 30 to provide a maximum flow rate setpoint value (Q max ). Furthermore, here, process 100 includes a correction step 40 to obtain a value (T ic ) of corrected internal temperature, so that step 20 of determining the maximum tank emptying flow rate setpoint is done from: - the value (T ic ) of corrected indoor temperature, - the value (T e ) of temperature measured outside the tank, and the value (P i ) of pressure measured inside the tank.

[0081] 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 designed 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.

[0082] Preferably, correction step 40 is performed before step 20 for determining the maximum flow rate setpoint, i.e., before consulting the database or before performing the mathematical calculation to obtain the value of the maximum flow rate setpoint (Q). max ).

[0083] Correction step 40 preferably includes taking into account a correction margin, the correction margin being variable depending on the indoor temperature (T i measured, of the outside temperature (T e ) measured and / or internal pressure (P i ) measured. Preferably, the correction margin is variable depending on the indoor temperature (T i ) measured, the correction margin varying for example between 0 and 30°C.

[0084] According to a first example, for correction step 40, a correction margin is applied corresponding to a fixed value which is systematically subtracted from the measured indoor temperature (T i 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 depending on the indoor temperature (T i ) measured and is predefined, meaning that the pre-recorded database includes pre-corrected indoor temperature values. According to this second example, we can consider that there is precisely no correction step 40 and that the process applies. According to a third example, after the measurement 10 of the indoor temperature (T i ) and before determining the maximum discharge flow rate setpoint 20, another database is consulted, grouping possible temperature values ​​(T) as input i) measurable inside the tank and at the outlet, corresponding corrected temperature values ​​(T ic ).

[0085] Figures 4a and 4b each represent an embodiment of process 100 where, in step 20 to determine the maximum flow rate setpoint, the database is consulted and when one of the values ​​(T e , T i , P i The value measured in measurement steps 10 is absent from this database. As explained above, particularly in the examples in Tables 1 to 4, the database contains 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 present in the database, for example, a value (T i) the temperature inside the tank is measured at 13°C, but this value is not included in the pre-recorded input data.

[0086] According to an embodiment illustrated in the figure, the process 100 includes a test step 50 to determine if the values ​​(T e , T i , P i ) provided after measurement step 10, and possibly correction step 40 when applicable, are present in the database. If all values ​​(T e , T i , P i ) are found in the database, then we proceed to step 20 to determine the maximum flow rate setpoint. However, if at least one of the values ​​(T e , T i , P iIf the missing value is absent from the database, we proceed to step 60, which involves interpolating 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 for the maximum flow rate setpoint (Q) is obtained. max ) is provided.

[0087] According to an alternative embodiment illustrated in Figure 1, when at least one of the three values ​​(Te, Ti, Pi) is missing from the pre-recorded database, test step 50 is followed by a selection step 70, which selects an output value from the pre-recorded database. This output value corresponds to input values ​​equal to or less than each of the two values ​​(Te, Ti) for the temperature measured outside and inside the tank, and equal to or greater than the value (Pi) for the pressure measured inside the tank. For example, if the value (Ti) of the temperature inside the tank, or the corrected value (Tic), is 13°C in Table 1, selection step 70 considers this value to be 0°C.By considering temperature values ​​equal to or lower than the two measured values ​​(Te, Ti) and pressure values ​​equal to or higher 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, limiting the flow rate to 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 caused by excessively low temperatures, all while using a simple database.

[0088] Finally, the invention also relates to a computer program comprising instructions which, when the program is executed by a computer, lead the computer to carry out 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 carry out the steps of a process as described above.

[0089] The invention is not limited to the embodiments presented, and other embodiments will be readily apparent 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

[0090] 2: Reservoir 3: Gas dispensing end 4: Control system 5: Temperature sensor 6: Pressure sensor 7: End opposite end 3 8: Temperature sensor 9: Electronic unit 10: Measurement steps 20: Maximum flow setpoint determination step (Q max )30: step of providing the maximum flow rate setpoint 40: correction step 50: step of testing for the presence of the values ​​(T e , T i , P i ) in the database60: interpolation step70: selection step in the database of 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 i ), regarding the pressure measured inside the tank100: method for determining a maximum flow rate setpoint for emptying a pressurized gas tank

Claims

Method (100) for determining a maximum discharge rate setpoint for a pressurized gas tank for a mobile or stationary device in order to control the tank temperature during discharge, the determination method comprising the following steps: - measuring the temperature outside the tank and providing a value (T e ) of temperature measured outside the tank, - measure the temperature inside the tank and provide a value (T i ) of temperature measured inside the tank, characterized in that the process further comprises the following steps: - measure the pressure inside the tank and provide a value (P i ) of pressure measured inside the tank, - determine (20), from each of these three values ​​(T e , T i , P i ) eti) from a pre-recorded database and / or ii) from a predefined mathematical function, a maximum flow rate setpoint (Qmax ) of emptying the tank and provide (30) this maximum flow rate setpoint (Q max ) of emptying the tank. Method (100) of determination according to claim 1, wherein when the maximum flow rate setpoint (Q max The tank emptying point is determined from each of the three values ​​(T e , T i , P i ) and a pre-recorded database, and when at least one of the three values ​​(T e , T i , P i If the value is absent from the pre-recorded database, the maximum flow rate setpoint (Q) is determined. max ) emptying of the tank by interpolation (60) of data present in the pre-recorded database. Method (100) of determination according to claim 1, wherein when the maximum flow rate setpoint (Q max The tank emptying point is determined from each of the three values ​​(T e , T i , P i) and a pre-recorded database having pre-recorded data as input (T' e , T' i , P' i ) temperature outside the tank, temperature inside the tank and pressure inside the tank, and, at the outlet, the corresponding maximum flow setpoint data (Q max ) of emptying the tank, and that at least one of the three values ​​(T e , T i , P i If the value is absent from the pre-recorded database, the maximum flow rate setpoint (Q) is determined. max ) of emptying the tank by selecting (70) from the pre-recorded database an output data corresponding to input data equal to or less than the temperature values ​​(T e , T i ) or input data equal to or greater than the pressure value (P i ). A method (100) for determining the temperature 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 value (T ic ) of corrected indoor temperature, so that the step of determining the maximum flow rate setpoint (Q max The tank emptying rate is calculated from: - the value (T ic ) of corrected indoor temperature, - the value (T e ) of temperature measured outside the tank, and the value (P i ) of pressure measured inside the tank. 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 internal temperature (T i measured, of the outside temperature (T e ) measured and / or internal pressure (Pi ) measured. Method (100) of determination according to any one of the preceding claims, wherein when the maximum flow rate setpoint (Q max The tank emptying point is determined from each of the three values ​​(T e , T i , P i ) and a pre-recorded database, the database includes pre-recorded discrete values ​​for the values ​​(T e ) of temperature measured outside the tank, and pre-recorded discrete values ​​for the (T) values i ) of temperature measured inside the tank, the discrete values ​​being spaced 20°C apart, preferably 10°C, preferably even 5°C. Method (100) of determination according to any one of the preceding claims, wherein when the maximum flow rate setpoint (Q max The tank emptying point is determined from each of the three values ​​(Te , T i , P i ) and a pre-recorded database, the database includes pre-recorded discrete values ​​for the values ​​(P i ) of pressure measured inside the tank, the discrete values ​​being spaced 50 bar apart, preferably 25 bar, preferably even more 10 bar. Method (100) of determination according to any one of the preceding claims, wherein when the maximum flow rate setpoint (Q max The tank emptying point is determined from each of the three values ​​(T e , T i , P i ) and a pre-recorded database, the database includes at least two maximum flow rate setpoint values ​​(Q max ), preferably at least five values ​​(Q max ), preferably at least ten more values ​​(Q max ). Method (100) of determination according to any one of the preceding claims, wherein the maximum flow rate setpoint (Q max ) of emptying the tank is determined periodically, preferably every 10 seconds, preferably even more so every second. A 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 use of 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 maximum flow rate setpoint (Q max ) to the device's control system in order to control the tank emptying rate according to the maximum flow rate setpoint (Q max ). A control method according to the preceding claim, configured so that the temperature measured inside the tank remains above a predetermined threshold (T min ), the predetermined threshold (T min ) being between -35°C and -65°C, preferably close to -40°C. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of determining (20) and providing (30) a maximum flow rate setpoint (Q max ) of emptying in a process as claimed in any one of the preceding claims, from the supplied values ​​of temperature (Te) outside the tank, of temperature (T i ) inside the tank and pressure (Pi) inside the tank. A computer-readable recording medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of determining (20) and providing (30) a maximum flow rate setpoint (Q max ) of emptying in a method as claimed in any one of claims 1 to 11, from the supplied values ​​of temperature (Te) outside the tank, of temperature (T i ) inside the tank and pressure (Pi) inside the tank.

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