DE102018121267A1 - Method for operating a motor vehicle and motor vehicle - Google Patents

Abstract

Technology disclosed here relates in particular to a method for operating a motor vehicle with at least one pressure vessel. The method comprises the steps: i) creating a map, the map describing the temperature behavior of the medium in the pressure vessel at various locations within the pressure vessel as a function of the pressure change; ii) measuring the temperature at a location within the pressure vessel; and iii) calculation of at least one extreme value of the temperature and / or of at least one average value of the temperature based on the measured temperature and the characteristic diagram.

Description

The technology disclosed here relates to a method for operating a motor vehicle with a pressure container system. Furthermore, the technology disclosed here comprises a motor vehicle which is set up to carry out at least one method of the methods disclosed here. Motor vehicles with a pressure container system are known as such.

During the filling of a pressure vessel of the pressure vessel system, heat is generated by the compression of the fuel. This warms up the pressure tank during refueling. If an upper limit temperature for the pressure vessel is exceeded, the likelihood that the pressure vessel will be damaged increases. Expansion cold, which cools the pressure vessel, also arises during the removal of fuel from the pressure vessel. If the temperature falls below a lower limit for the pressure vessel, the likelihood that the pressure vessel will be damaged also increases. The risk of inadmissibly high heating or cooling of the pressure vessel can be reduced by slowly filling or removing. In practice, however, a vehicle user would like to refuel the pressure container as quickly as possible and draw comparatively large amounts of fuel in the high-load range. There is therefore a need to fill an otherwise known pressure vessel with fuel as quickly as possible or to remove fuel from the pressure vessel as quickly as possible. Furthermore, an uneven temperature field forms in the pressure vessel during filling or removal and due to stratification. If the temperature is only determined at one point or at a few points in the pressure vessel, the total fuel density or the total fuel mass can only be determined inaccurately.

It is a preferred object of the technology disclosed herein to reduce or remedy at least one disadvantage of a previously known solution or to propose an alternative solution. It is in particular a preferred object of the technology disclosed here to improve the filling with or removal of fuel, this preferably having no or only an insignificant effect on installation space, weight, manufacturing costs and / or vehicle safety. It is also a task to determine the density or mass of the stored fuel more precisely. Further preferred tasks can result from the advantageous effects of the technology disclosed here. The object (s) is / are achieved by the subject matter of the independent claims. The dependent claims represent preferred configurations.

The technology disclosed here relates to a motor vehicle with a pressure container system (e.g. passenger cars, motorcycles, commercial vehicles). Such a vehicle can be, for example, a vehicle that is equipped with a fuel cell system as an energy converter.

The pressure vessel system is used to store fuel which is gaseous under ambient conditions. The pressure container system can be used, for example, in a motor vehicle that is operated with compressed ("compressed natural gas" = CNG) or liquefied (LNG) natural gas or with hydrogen. The pressure vessel system is fluidly connected to at least one energy converter, which is set up to convert the chemical energy of the fuel into other forms of energy.

Such a pressure vessel system comprises at least one pressure vessel, in particular a composite overwrapped pressure vessel (= COPV). The pressure vessel can be, for example, a cryogenic pressure vessel (= CcH2 or COP) or a high pressure gas vessel (= CGH2).

High-pressure gas containers are designed to store fuel permanently at ambient temperatures at a nominal operating pressure (also called nominal working pressure or NWP) of approx. 350 barü (= overpressure compared to atmospheric pressure), and preferably preferably of approx. 700 barü or more. A cryogenic pressure vessel is suitable for storing the fuel at the aforementioned operating pressures even at temperatures that are significantly below the operating temperature of the motor vehicle.

The system disclosed here further comprises at least one control unit. The control unit is among others set up to carry out the procedural steps disclosed here. For this purpose, the control unit can regulate the actuators of the system at least partially and preferably completely (closed loop control) or control (open loop control) based on the signals provided. The control unit can at least influence the pressure container system. Alternatively or additionally, the control device can also be integrated in another control device, e.g. in a higher-level control unit. The control device can interact with other control devices of the motor vehicle.

• - Erstellen eines Kennfeldes, wobei das Kennfeld das Temperaturverhalten des Mediums im Druckbehälter an verschiedenen Orten innerhalb des Druckbehälters in Abhängigkeit der Druckänderung beschreibt;
• - Messen der Temperatur an einem Ort innerhalb des Druckbehälters; und
• - basierend auf der gemessenen Temperatur und dem Kennfeld berechnen
  1. i) von mindestens einem Extremwert der Temperatur des Mediums im Druckbehälter, und/oder
  2. ii) von mindestens einem Durchschnittwert der Temperatur des Mediums im Druckbehälter.

The technology disclosed here relates in particular to a method for operating a motor vehicle with at least one pressure vessel. The process includes the steps:

• - Creation of a map, the map describing the temperature behavior of the medium in the pressure vessel at different locations within the pressure vessel as a function of the pressure change;
• Measuring the temperature at a location within the pressure vessel; and
• - Calculate based on the measured temperature and the map
  1. i) at least one extreme value of the temperature of the medium in the pressure vessel, and / or
  2. ii) at least an average of the temperature of the medium in the pressure vessel.

The characteristic diagram disclosed here can be created in particular during the securing of the storage system or the testing of the motor vehicle for a series of a motor vehicle with the same pressure container system. The map characterizes the thermal behavior of the medium in the pressure vessel and describes this temperature behavior at various locations within the pressure vessel as a function of the change in pressure of the stored fuel. In particular, the map can be obtained through various test series and / or through simulations. Such a map can be a multidimensional lookup table, for example.

1. i) vom Ort innerhalb des Druckbehälters;
2. ii) von der Druckänderungsgeschwindigkeit; und
3. iii) von der Umgebungstemperatur.

The characteristic diagram can expediently characterize the temperature behavior of the medium in the pressure vessel depending on

1. i) the location within the pressure vessel;
2. ii) the rate of pressure change; and
3. iii) the ambient temperature.

The location within the pressure vessel is the point within the pressure vessel (usually near the pressure vessel wall), the temperature of which is to be calculated or approximated by the map taking into account a real measured value. For example, it is known that during the refueling, due to the compression heat, the pressure container heats up more at the end that lies opposite the on-tank valve.

The pressure change rate or pressure change rate is the rate of change of the storage pressure of the fuel in the pressure vessel. In the event of removal, the rate of change in pressure is influenced by the operating strategy of the fuel cell system. During refueling, the rate of pressure change is usually specified by the filling station's fueling process. For example, the refueling can be done according to a standard, e.g. the SAE J2601 standard from 2016 The pressure change rate can be recorded particularly preferably by directly or indirectly recording refueling parameters of the refueling. For example, the communication interface can be used to inform the motor vehicle of the pressure profile or pressure ramp with which the refueling will take place. In addition to this direct detection, the control unit of the vehicle can also be set up to infer the refueling or refueling parameters based on secondary facts.

The motor vehicle can be set up to detect the ambient temperature directly or indirectly. Such a detection of the ambient temperature can be detected, for example, via a temperature sensor of the motor vehicle and / or communicated wirelessly to the motor vehicle.

According to the technology disclosed here, the method includes the step of measuring the temperature at a location of the pressure vessel. The real temperature is thus measured during the operation of the motor vehicle, in particular during the filling with fuel and / or the removal of fuel from the pressure vessel. The measurement can be carried out with at least one temperature sensor. One or more temperature sensors are advantageously used. For example, a temperature sensor can be provided on the pressure vessel wall. Alternatively or additionally, a temperature sensor can be provided in the on-tank valve and / or in a line that is fluidly connected to the interior of the pressure vessel. With the technology disclosed here, it is advantageously possible to achieve maximum filling and removal rates without a large number of temperature sensors simultaneously monitoring the temperature at different locations on the pressure vessel.

The temperature is preferably measured at one end of the pressure vessel, for example at the end at which the on-tank valve is provided.

1. i) mindestens ein Extremwert der Temperatur und/oder
2. ii) mindestens einem Durchschnittwert der Temperatur.

The method disclosed here comprises the step, after which the calculation is based on the measured temperature and the map:

1. i) at least one extreme value of the temperature and / or
2. ii) at least one average temperature.

1. i) der indikativ für eine untere Grenztemperatur ist, die der Druckbehälter während der Entnahme von Brennstoff aus dem Druckbehälter nicht unterscheiten darf; oder
2. ii) der indikativ für eine obere Grenztemperatur ist, die der Druckbehälter während der Befüllung mit Brennstoff nicht überschreiten darf.

The at least one extreme value can be a value

1. i) which is indicative of a lower limit temperature which the pressure vessel must not fall below during the removal of fuel from the pressure vessel; or
2. ii) is indicative of an upper limit temperature that the pressure vessel must not exceed during the filling with fuel.

Such limit temperatures can be specified, for example, in order to reduce the probability of thermal failure of the material of the pressure container system.

The average value can be, for example, the average temperature of the stored fuel, which would result during the filling or during the withdrawal, if there were no temperature differences. This arithmetically resulting average temperature can be used, for example, to calculate the fuel density or fuel mass that is located in the pressure vessel. The correct display value of a tank level indicator can thus be determined more precisely. Measurement inaccuracies due to the very different heating of the fuel or the pressure vessel can thus be reduced.

In other words, the technology disclosed here is based on the idea of removing the fuel in such a way that the pressure vessel temperature approaches the respective limit value as closely as possible, without, however, falling below it. At the same time, the pressure vessel temperature should, if possible, approach the limit temperature during filling without exceeding it. The technology disclosed here takes into account the temperature distribution of the medium in the pressure vessel during filling or removal. According to the technology disclosed here, it is advantageous not to install a large number of temperature sensors at different locations in each pressure vessel, but rather to use a pressure vessel map which is obtained by measurements and / or simulations. Measurements on experimental set-ups can be used to record a specific temperature behavior of the medium in the pressure vessel for different operating modes (e.g. refueling, removal) that circumscribes the temperatures in the entire pressure vessel sufficiently precisely to identify relevant limit value violations. By linking the measurement results for the entire pressure vessel from the tests with the measurement point or the measurement points in real operation (including the ambient temperature), a correction value table (also called a map) can be created that, depending on the operating mode, realizes the values for the measurement value in real operation determined the remaining pressure vessel. As an alternative or in addition to measurements on experimental set-ups, the map can also be obtained by simulations. The highest or lowest temperatures of the medium in the pressure vessel can thus advantageously be determined. In particular, so-called cold spots and / or hot spots can be determined in which the wall of the pressure vessel becomes particularly cold or particularly hot. If such temperature extremes and their locations are known, a safety-oriented operating strategy can be better implemented.

A comparatively high level of security can thus be achieved at comparatively low costs. In particular, the likelihood of material damage due to thermal effects can be further reduced. The display accuracy of a fuel display can also be advantageously improved.

The pressure vessel system disclosed here advantageously comprises at least one pressure sensor which is set up to directly or indirectly detect a value which is indicative of the pressure or the change in pressure in the pressure vessel.

Test setups and statistical methods that are known per se can be used when creating the map. Furthermore, simulation models for deriving the map are known as such.

• 1 eine schematische Querschnittsansicht eines Druckbehälters
• 2 eine schematische Darstellung des Druckverlaufs und des Temperaturverlaufs an zwei verschiedenen Orten des Druckbehälters.

The technology disclosed here will now be explained with reference to the figures. Show it:

• 1 is a schematic cross-sectional view of a pressure vessel
• 2 a schematic representation of the pressure curve and the temperature curve at two different locations of the pressure vessel.

The 1 shows a schematic cross section through a pressure vessel. The pressure vessel comprises a central part here cylindrical and two ends. At one end there is a filling and withdrawal line through which the fuel (here hydrogen H2 ) flows into the pressure vessel. A fuel temperature is here adjacent to this end via a sensor T1 detected. Furthermore, the fuel temperature here T2 recorded at the end opposite the first mentioned end. Furthermore, in the example shown here, the temperature in the component environment Tcomponent environment and the ambient temperature T _environment detected.

The 2 shows a schematic representation of the pressure curve and the temperature curve at the two different locations of the pressure vessel, where previously the temperatures T1 and T2 were recorded. It is noticeable that the temperature T2 during refueling rises more than the temperature T1 adjacent to the on-tank valve. A maximum temperature deviation arises with increasing refueling. After refueling, the temperatures are the same T1 . T2 gradually come back on.

The technology disclosed here can be implemented such that, for example, the temperature sensor for detecting the temperature T1 is installed in the motor vehicle and measures the actual real temperatures. The other temperature profiles for other points, such as for the point at which the temperature T2 is determined, can be stored in a map by means of appropriate tests / simulations for corresponding pressure change scenarios. If, for example, an upper or lower temperature limit is not to be exceeded or undershot, the actual temperature in the hotspot or coldspot can be deduced from the measured temperature and the temperature deviation stored in the map, for example by adding the temperature deviation to the measured real temperature becomes. The sum obtained can be compared, for example, with the upper limit. At the same time, the real value itself can be used for the target / actual comparison with a limit value. In such an embodiment, the map is used to determine an offset value.

In the example shown here, refueling with a constant refueling ramp or constant pressure change rate was assumed. However, this does not have to be the case. At the same time, maps could also be stored for different fueling profiles. Furthermore, only the refueling was explained in FIG. The same applies to the removal of fuel from the pressure vessel, in which case a lower temperature limit is to be used.

The technology disclosed here is not limited to a pressure vessel system with a pressure vessel. At the same time, the pressure vessel system can comprise a plurality of pressure vessels and a map can be stored for each pressure vessel and the methods disclosed here can be applied to each pressure vessel. At the same time it is conceivable that several pressure vessels are constructed identically and the same characteristic diagram characterizes their temperature behavior. In such a case, the same map can be used for both pressure vessels.

The foregoing description of the present invention has been presented for purposes of illustration only and is not intended to limit the invention. Various changes and modifications are possible within the scope of the invention without leaving the scope of the invention and its equivalents.

Claims (8)

Method for operating a motor vehicle with at least one pressure vessel, comprising the steps: - Creation of a map, the map describing the temperature behavior of the medium in the pressure vessel at different locations within the pressure vessel depending on the pressure change; Measuring the temperature at a location within the pressure vessel; and - and based on the measured temperature and the map: calculate iii) at least one extreme value of the temperature and / or iv) at least one average temperature. Procedure according to Claim 1 , the extreme value being a value, iii) which is indicative of a lower limit temperature which the medium in the pressure vessel must not fall below during the removal of fuel from the pressure vessel; or iv) which is indicative of an upper limit temperature which the medium in the pressure vessel may not exceed during the filling with fuel. Procedure according to Claim 1 and 2 , where the average value is the average temperature of the stored fuel during filling or during withdrawal. Procedure according to Claim 3 , further comprising the step: adjusting a tank level indicator based on the calculated average value. Method according to one of the preceding claims, wherein the map characterizes the temperature behavior of the pressure vessel in dependence iv) the location within the pressure vessel; v) the rate of pressure change; and vi) the ambient temperature. Procedure according to Claim 5 , further comprising the step of: - detecting a value indicative of the rate of pressure change; and / or - detecting a value that is indicative of the ambient temperature. Procedure according to Claim 6 , wherein the rate of pressure change is detected by directly or indirectly detecting refueling parameters of a refueling. Motor vehicle with at least one pressure container and at least one controller, the controller being set up to carry out one of the preceding methods.

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