FR3042268A1 - SYSTEM AND METHOD FOR DETERMINING THE FLUID LEVEL IN A RESERVOIR - Google Patents

Abstract

System for measuring the level of fluid in a tank (1) of spacecraft, said tank (1) extending along a vertical axis (Z), said tank (1), characterized in that said measuring system comprises a computer (3), a system for determining the acceleration vector (4) of said reservoir and one or more identical level probes (2) regularly arranged on the internal walls of the reservoir (1), at the same height measured along the axis vertical (Z), the calculator being configured to determine the level of fluid in the reservoir (1) by means of the acceleration to which the reservoir (1) measured by the acceleration vector determination system (4) is subjected , and by the level measurement performed by at least one of the level probes (2).

Description

GENERAL TECHNICAL FIELD

The present invention relates to the field of fluid level sensors in a tank, and finds a particular application in the field of spacecraft for level measurement in propellant tanks.

STATE OF THE ART

The determination of the propellant level in the tanks of a launcher is carried out according to the objectives of said launcher by a sensor covering the height of the tank or segmented, since the implementation of a launcher until the operation of its flight .

Such a determination is necessary in order to guarantee a given level of propellant in the tanks during the filling or emptying of the tanks on the ground, and to detect at the end of the flight a level of emptying of the tanks.

Level probes to perform such measurements can also be used to evaluate the rate of tank emptying during operation. In addition, they are essential to ensure active management propellant, especially to adapt the flight parameters based on levels in tanks. By active management of the propellant is meant a function to identify the current amount of propellant, and to define the necessary corrections to the operation of the launcher to achieve a desired consumption.

The level measurements in the tanks during the flight of a launcher are however disturbed by several phenomena which can hinder their accuracy, in particular the sloshing in the tanks, the contractions and thermal expansions of the tanks and the gauges, the errors of placement of the gauges , or the inclination of the free propellant surface due to the trajectory of the launcher and its acceleration.

In addition, the level measurements are used to know the residual masses of propellant in the tanks. The reconstitution of these masses is disturbed by the thermodynamic conditions of propellant (density) and by the volume occupied by this residual propellant.

In the current state, the usual means implemented to overcome the attitude of the spacecraft on the free surface is the consideration of a flat margin supposed to cover the worst case of the orientation of the vector launcher acceleration. The reconstitution of the residual mass of propellant in the tank is then biased.

The present invention aims at remedying at least partially these problems, using the inclination of the free surface of the propellant in the tanks.

PRESENTATION OF THE INVENTION To this end, the present invention proposes a system for measuring the level of fluid in a spacecraft reservoir, said reservoir extending along a vertical axis, said reservoir, characterized in that said measuring system comprises a calculator, a system for determining the acceleration vector of said reservoir, and one or more identical level probes, arranged regularly on the internal walls of the reservoir, at the same height measured along the vertical axis, the computer being configured so as to determining the fluid level in the reservoir by means of the acceleration to which the reservoir measured by the acceleration vector determination system is subjected, and by the level measurement made by at least one of the level probes.

For example, the computer is configured so that, depending on the orientation of the acceleration measured with respect to the vertical axis, the level of fluid in the reservoir is determined by means of a single level probe of the said probes. level.

The calculator may also be configured to determine an equivalent fluid height in the reservoir, said equivalent fluid height in the reservoir corresponding to the fluid height in the reservoir for an acceleration parallel to the vertical axis of the reservoir.

The computer is typically configured to perform a filter function of the measurements made by the level probes. Said filtering function is then typically performed so as to rule out the level variations due to one or more modes of fluid sloshing in the tank.

The measurement system comprises for example three identical level probes, each disposed in the reservoir at the same height measured along the vertical axis, and disposed spaced 120 ° around the vertical axis in the reservoir. The invention also relates to a tank provided with such a measurement system, and a spacecraft equipped with such a tank. The invention further relates to a method for estimating the level of fluid in a tank of a spacecraft, said method comprising steps of: - determination using a set of measurements of the acceleration vector to which the tank is subjected, - measurement a fluid level in the reservoir, - determining a fluid level in the reservoir, as a function of the acceleration and the level of fluid measured.

The fluid level in the reservoir is for example determined by means of an equivalent fluid height in the reservoir, said equivalent fluid height in the reservoir corresponding to the fluid height in the reservoir for an acceleration parallel to a vertical axis of the reservoir. tank.

The method typically comprises a step of filtering the fluid level measured in the tank, said filtering step being carried out so as to reject the level variations due to one or more modes of fluid sloshing in the tank.

PRESENTATION OF THE FIGURES Other characteristics, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and nonlimiting, and which should be read with reference to the appended figures, in which: FIGS. 1a and 1b schematically illustrate a propellant reservoir, - Figures 2 and 3 show schematically an example of positioning probes within a propellant reservoir, - Figures 4a and 4b illustrate two examples of propellant level measurements within of tanks, - Figure 5 schematically illustrates the operation of the system according to one aspect of the invention.

In all the figures, the elements in common are identified by identical reference numerals.

DETAILED DESCRIPTION

Figures la and lb schematically illustrate a propellant tank in top view and in side view.

The reservoir 1 is represented as a cylinder of revolution along a vertical axis Z, radius R and height Hres.

A probe positioned on a wall of the tank 1 is considered at a height Hsonde. The launcher acceleration is represented by an arrow A. Thus its inclination y with respect to the vertical axis Z is identified, the angle y being in the plane defined by the longitudinal axis of the launcher and the acceleration vector, and its orientation relative to the position of a probe considered on the walls of the tank 1 by the angle δ.

As described in the diagram, the orientation of the acceleration vector causes the free surface of the propellant to tilt in the tank 1, represented by a line in the tank 1 (the sloshing is not shown). This inclination is an angle y with respect to the horizontal direction, defined as being perpendicular to the vertical axis Z of the tank 1.

It is therefore clear that such an inclination disturbs the ergol level measurements in the tank 1, in that the level measured by a single probe does not correspond to a real level over the entire periphery of the tank 1.

The multiplication of the probes so as to have a continuous measurement on the whole periphery of the tank 1 is not conceivable, both for problems of cost and mass.

The proposed system therefore aims to determine, by means of the data measured by at least one level sensor and data relating to the launcher acceleration including the tank 1, an equivalent level of propellant in the tank 1, this equivalent level of ergol in the tank 1 thus making it possible to determine the quantity and the mass of propellant remaining.

Thus, if we consider the average level of ergol H in the reservoir, corresponding to the intersection between the free surface of the propellant and the vertical axis Z of the reservoir, a distance ΔΗ is defined between the mean level H and the Hsonde level measured by the probe.

Now, the following relationships are deduced from the figures:

Is

AH = R x cos δ x tany

So H = Hsonde - AH = Hsonde - R x cos δ x tany

It is thus possible, using the propellant height measured by a probe, and data concerning the acceleration, to define an equivalent propellant height in the tank 1, this equivalent height defining an equal volume of propellant defined by a cylinder of revolution with a horizontal free surface (ie perpendicular to the vertical axis Z of the tank 1).

The tank 1 is therefore equipped with an acceleration determination system 4 configured to collect the data relating to the acceleration vector, for example a set of accelerometers or calculation means transmitting the acceleration vector, from one or more level 2 probes, and a calculator 3 adapted to determine the equivalent height of propellant in the tank from, in particular, the data provided by the set of accelerometers and the level probe (s).

In order to make the measurements more reliable, several identical level probes are typically arranged in the tank 1. These level probes are arranged regularly along the wall of the tank 1, preferably at the same height along the vertical axis Z.

The reservoir thus comprises, for example, three identical level probes, which makes the measurements more reliable, while being acceptable in terms of cost and mass, depending on the constraints of the project under consideration.

Figures 2 and 3 show an example of implantation of the level 2 probes in the tank 1.

It can be seen from these figures that the three level 2 probes are arranged at the same height Hs, and are distributed at 120 ° to each other around the vertical axis Z.

FIG. 4 represents two examples of curves representing the level of propellant in a tank, respectively for a cryogenic hydrogen tank (FIG. 4a), and a cryogenic oxygen tank (FIG. 4b).

We notice several plots on each of the graphs.

The linear plots M1 represent the theoretical level of propellant in the tanks as a function of time, and thus reflect a regular consumption of propellant.

The most irregular plots M2 reflect the ergol levels measured by the level 2 probes arranged in the tanks 1. The irregularity of these plots is due in particular to the variations of the acceleration, to the sloshing of the propellants in the tanks 1, and more generally to the phenomena leading to propellant movement in tanks 1.

The computer 3 is thus configured to perform a filtering of the measurements made by the level 2 probes, so as to obtain a level filtered from the level measured by the level 2 probes, this filtering being configured so as to exclude the level variations due to one or more sloshing modes. The third curve M3 represented on the graphs of FIG. 4 thus reflects the filtered level.

The computer 3 then typically uses the filtered level of propellant in the tank 1 in order to determine the equivalent level of propellant, which makes the reliability and the accuracy of the calculations made more reliable.

Figure 5 schematically illustrates the operation of the system as shown.

Thus, the input data, which are recorded by level probes and by a system for determining the acceleration vector, namely one or more level probes falling within the levels of propellant in a reservoir (in FIG. the occurrence of three level probes thus three levels of propellant NI, N2 and N3), and a system for determining the acceleration vector falling angles δ and y reflecting the orientation of the acceleration of the machine comprising the tank 1 .

The data corresponding to the ergol levels measured by the level probe (s) are then typically filtered so as to rule out the level variations due to one or more sloshing modes.

Once this optional filtering has been performed, the data are then verified and used by the computer 3 to determine an average level of propellant in the tank in question, which then makes it possible to easily determine the mass and the volume of propellant remaining in this tank 1.

The proposed system therefore makes it possible to improve the accuracy of measurements in propellant tanks, by filtering the inclination of the free surface.

In addition, since a probe is sufficient to determine the level of propellant, the proposed system makes it possible to obtain increased reliability, insofar as the failure of one of the level probes does not then impact the measurements.

Claims (10)

claims 1. System for measuring the level of fluid in a tank (1) of spacecraft, said tank (1) extending along a vertical axis (Z), said tank (1), characterized in that said measuring system comprises a calculator (3), a system for determining the acceleration vector (4) of said reservoir (1) and one or more identical level probes (2) arranged regularly on the internal walls of the reservoir (1) at the same height measured along the vertical axis (Z), the computer being configured to determine the level of fluid in the reservoir (1) by means of the acceleration to which the reservoir (1) measured by the system for determining the vector acceleration (4), and by the level measurement performed by at least one of the level probes (2). 2. System according to claim 1, wherein the computer (3) is configured so as, depending on the orientation of the acceleration measured relative to the vertical axis (Z), determine the fluid level in the tank (1) by means of a single level probe (2) among said level probes (2). 3. System according to claim 2, wherein the computer (3) is configured to determine an equivalent fluid height (H) in the reservoir (1), said equivalent fluid height (H) in the reservoir (1). corresponding to the fluid height in the tank (1) for an acceleration parallel to the vertical axis (Z) of the tank (1). 4. System according to one of claims 1 to 3, wherein the computer (3) is configured to perform a filtering function of the measurements made by the level probes (2). The system of claim 4, wherein said filtering function is configured to rule out level variations due to one or more modes of fluid sloshing in the tank (1). 6. System according to one of claims 1 to 5, wherein the measuring system comprises three level probes (3) identical, each disposed in the reservoir (1) at the same height (Hsonde) measured along the vertical axis (Z), and disposed spaced 120 ° about the vertical axis (Z) in the tank (1). 7. propellant tank of a spacecraft, comprising a system according to one of claims 1 to 5. 8. A method for estimating the level of fluid in a tank (1) of a spacecraft, said method comprising steps of: - determination by means of an acceleration determination system (4) which is subjected to reservoir (1), - measurement of a fluid level in the reservoir (1), - determination of a fluid level in the reservoir (1), as a function of the acceleration and the level of fluid measured. 9. The method of claim 8, wherein the fluid level in the reservoir (1) is determined by means of an equivalent fluid height (H) in the reservoir (1), said equivalent fluid height (H) in the reservoir (1) corresponding to the height of fluid in the reservoir (1) for an acceleration parallel to a vertical axis (Z) of the reservoir (1). 10. Method according to one of claims 8 or 9, wherein a step is performed for filtering the fluid level measured in the reservoir (1), said filtering step being performed in such a way as to rule out the level variations due to a or several modes of fluid sloshing in the tank (1).