METHOD FOR THREE-DIMENSIONAL TEMPERATURE MEASUREMENT AND APPARATUS

Abstract

A method for measuring a three-dimensional temperature field of a liquid in a receptacle, in particular of cryogenic liquids, wherein a local liquid density is determined by means of electrical capacitance tomography and the local temperature is derived based on the local liquid density and a local liquid pressure, and an apparatus for carrying out such a method.

Claims

1. A method for measuring a three-dimensional temperature field of a liquid in a receptacle, comprising: determining a local liquid density of the liquid via electrical capacitance tomography, and deriving a local temperature of the liquid based on the local liquid density and a local liquid pressure.

2. The method according to claim 1, wherein the liquid is a cyrogenic liquid.

3. The method according to claim 1, wherein the liquid density is determined from a dielectric constant for a saturated state of the liquid.

4. The method according to claim 1, wherein a plurality of individual pressure measurement values are captured in the receptacle and the local pressure is determined from the individual pressure measurement values.

5. The method according to claim 1, wherein a pressure measurement is carried out by just one pressure sensor and the local pressure is determined via electrical capacitance tomography.

6. The method according to claim 1, wherein the local temperature is ascertained from a materials database of the liquid.

7. An apparatus for carrying out the method according to claim 1, comprising: an electrical capacitance tomography device, a pressure measurement device configured to measure the local liquid pressure, and a device configured to ascertain the local temperature of the liquid from the local liquid density and the local liquid pressure.

8. The apparatus according to claim 7, wherein the pressure measurement device comprises a plurality of pressure sensors.

9. The apparatus according to claim 7, wherein the pressure measurement device comprises exactly one pressure sensor.

10. The apparatus according to claim 7, wherein the device configured to ascertain the local temperature of the liquid from the local liquid density and the local liquid pressure is a materials database.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Preferred example embodiments of the invention are explained in greater detail in the following by means of highly simplified schematic illustrations.

[0017] FIG. 1 shows a method according to the invention for measuring a three-dimensional temperature field of a liquid, and

[0018] FIG. 2 shows an apparatus according to the invention for carrying out the method shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] FIG. 1 schematically shows a method or measurement principle 1 according to the invention for determining a local liquid temperature T for the measurement of a three-dimensional temperature field of a liquid in a receptacle. An example of a liquid is cryogenic rocket fuel such as liquid hydrogen in a fuel tank of a space rocket engine.

[0020] In a first step 2, a local dielectric constant is measured by means of electrical capacitance tomography.

[0021] Subsequently, in a next step 4, a local density p of the liquid is determined for the saturated state (saturation temperature Tsat), i.e., assuming that the liquid temperature T is at the boiling point, while taking into account the local dielectric constant. In the saturation state, the dielectric constant and the density p form a (linear) functional relationship.

[0022] A pressure p of the liquid is additionally calculated in a step 6.

[0023] In a next step 8, the local temperature T is ascertained from the previously determined density ? and the pressure p by means of a materials database.

[0024] The local hydrostatic forces can often be neglected, which is usually justifiable at least in the case of liquid hydrogen due to its low density (?70 kg/m.sup.3). The expected error in the temperature measurement is then small or negligible.

[0025] It is further noted that liquids can occur in either a supercooled or saturated state. Superheated liquids, which occur e.g., in the case of liquid hydrogen in the order of about 0.1 K, can be neglected before they enter the boiling state.

[0026] FIG. 2 schematically illustrates an apparatus 10 according to the invention. The apparatus 10 is associated with a liquid receptacle 12 and has an electrical capacitance tomography device 14 for determining a liquid density ?, a pressure measurement device 16 for measuring a local liquid pressure p in the receptacle 12 and a device 18 for ascertaining the local temperature T of the liquid from the local liquid density ? and the local liquid pressure p.

[0027] The electrical capacitance tomography device 14 has a plurality of ECT sensors arranged (preferably evenly) on the inside of the receptacle, for example in the form of plate-shaped electrodes 20.

[0028] The pressure measurement device 16 preferably comprises a plurality of pressure sensors 22 (pressure sensor array) distributed (preferably evenly) on the inside of the receptacle 12.

[0029] In the example embodiment shown, the device 18 for ascertaining the local temperature T of the liquid is a materials database from which a temperature T at a given density ? and given pressure p can be read out for a particular liquid.

[0030] A control and monitoring device of the apparatus 10 is not shown, as these are known to a person of skill in the art. The systems and devices described herein may include a controller, control unit, control device, controlling means, system control, processor, computing unit or a computing device comprising a processing unit and a memory which has stored therein computer-executable instructions for implementing the processes described herein. The processing unit may comprise any suitable devices configured to cause a series of steps to be performed so as to implement the method such that instructions, when executed by the computing device or other programmable apparatus, may cause the functions/acts/steps specified in the methods described herein to be executed. The processing unit may comprise, for example, any type of general-purpose microprocessor or microcontroller, a digital signal processing (DSP) processor, a central processing unit (CPU), an integrated circuit, a field programmable gate array (FPGA), a reconfigurable processor, other suitably programmed or programmable logic circuits, or any combination thereof.

[0031] The memory may be any suitable known or other machine-readable storage medium. The memory may comprise non-transitory computer readable storage medium such as, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. The memory may include a suitable combination of any type of computer memory that is located either internally or externally to the device such as, for example, random-access memory (RAM), read-only memory (ROM), compact disc read-only memory (CDROM), electro-optical memory, magneto-optical memory, erasable programmable read-only memory (EPROM), and electrically-erasable programmable read-only memory (EEPROM), Ferroelectric RAM (FRAM) or the like. The memory may comprise any storage means (e.g., devices) suitable for retrievably storing the computer-executable instructions executable by processing unit.

[0032] The methods and systems described herein may be implemented in a high-level procedural or object-oriented programming or scripting language, or a combination thereof, to communicate with or assist in the operation of the controller or computing device. Alternatively, the methods and systems described herein may be implemented in assembly or machine language. The language may be a compiled or interpreted language. Program code for implementing the methods and systems described herein may be stored on the storage media or the device, for example a ROM, a magnetic disk, an optical disc, a flash drive, or any other suitable storage media or device. The program code may be readable by a general or special-purpose programmable computer for configuring and operating the computer when the storage media or device is read by the computer to perform the procedures described herein.

[0033] Computer-executable instructions may be in many forms, including program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types. Typically, the functionality of the program modules may be combined or distributed as desired in various embodiments.

[0034] In a first alternative (not shown) to the pressure sensor array, only one pressure sensor 22 is provided for measuring pressure, by means of which the pressure p is then calculated during ballistic flight phases. During such flight phases, the hydrostatic forces are low or negligible.

[0035] A second alternative (not shown) to the pressure sensor array requires just one pressure sensor, namely when the local pressure is estimated from the electrical capacitance tomography itself.

[0036] Disclosed are a method for measuring a three-dimensional temperature field of a liquid in a receptacle, in particular of cryogenic liquids, wherein a local liquid density is determined by means of electrical capacitance tomography and the local temperature is derived based on the local liquid density and a local liquid pressure, and an apparatus for carrying out such a method.

[0037] While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.