Capacitive liquid level meter calibration device and method for cryogenic propellant

Abstract

The invention relates to the technical field of calibration of capacitive liquid level meters for low-temperature propellants, in particular to a calibration device and method for a capacitive liquid level sensor for a low-temperature propellant. The invention relates to a capacitive liquid level sensor calibration device for a low-temperature propellant, which comprises a test container, a liquid inlet and outlet pipeline, a liquid inlet and outlet low-temperature stop valve, a capacitive liquid level meter, an upper liquid level temperature sensor, a lower liquid level temperature sensor and an upper and lower limit pressure sensor, the liquid level sensor is installed in the storage box, and the liquid level transmitter is in signal connection with the liquid level meter through a special cabin-passing plug.

Description

Technical Field

[0001] The invention relates to the technical field of calibration of a capacitive liquid level gauge for cryogenic propellants, and in particular to a device and method for calibrating a capacitive liquid level gauge for cryogenic propellants. Background Art

[0002] In ground tests of space launch vehicle engines that commonly use cryogenic propellants (liquid hydrogen, liquid oxygen, liquid nitrogen and liquid methane, etc.), the liquid level measurement data of the cryogenic container obtained by the capacitive level gauge is one of the important judgment bases for whether the test can be carried out normally. The capacitive level gauge calibration device for cryogenic propellants is a strong guarantee to ensure the accuracy and effectiveness of the liquid level sensor data.

[0003] Due to the low temperature characteristics and operational safety of liquid oxygen at -183℃, liquid nitrogen at -196℃, and liquid hydrogen at -253℃, the existing domestic measurement and calibration devices are unable to calibrate the capacitive level gauge with real media, and are also unable to accurately provide the measurement accuracy of the capacitive level gauge in a cryogenic propellant environment, and cannot be regularly calibrated. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect in the prior art that real cryogenic propellant cannot be used to safely and effectively calibrate a capacitive liquid level gauge, thereby providing a capacitive liquid level gauge calibration device and method for cryogenic propellant.

[0005] In order to solve the above technical problems, the present invention provides a capacitive liquid level gauge calibration device for cryogenic propellants, which comprises a test container, liquid inlet and outlet pipelines, liquid inlet and outlet cryogenic stop valves, a capacitive liquid level gauge, an upper liquid level temperature sensor, a lower liquid level temperature sensor, and upper and lower limit pressure sensors. The temperature sensor and the pressure sensor are installed on the bottom and outer wall of the test container, the liquid level sensor is installed in the storage tank, and the liquid level transmitter and the liquid level gauge are connected by a special through-tank plug to realize signal connection.

[0006] The device is mainly composed of a container for containing cryogenic propellant. The inlet and outlet interfaces are set at the bottom of the container. The upper end of the container adopts a detachable flange connection form, which can be replaced with connection interfaces with different functions. The device is equipped with a liquid level gauge installation interface, a discharge interface, and a window interface. The discharge interface is equipped with a cryogenic valve. The outside of this device is insulated.

[0007] The installation interface of the level gauge includes:

[0008] The installation interface specification of the level meter is 80mm inner diameter, which meets the maximum outer diameter requirement of the level meter installation. The connection form of the level meter is RFBL flange blind plate connection form, and a special terminal is set on the blind plate to lead out the measurement signal of the level meter. The terminal is insulated from the measuring container and connected to the level meter.

[0009] Optionally, the blind plate can be processed according to the connection size of the level gauge to ensure that the interface fits and the connection is reliable.

[0010] Optionally, the dedicated wiring terminals on the blind plate can be high-voltage wiring terminals according to different test pressures.

[0011] Optionally, the window interface includes:

[0012] The window interface is an interface set up for observing and verifying the liquid level using an optical sensor. Its specification is an inner diameter of 40mm, and it is composed of two metal flanges clamping high-strength glass.

[0013] The high-strength glass in the window interface can also be replaced with a metal blind plate or other sensors.

[0014] Optionally, the discharge interface includes: The discharge interface is an interface provided for discharging boiling and vaporized cryogenic propellant. Its specification is an inner diameter of 40mm, connected to a DN40 PN16 cryogenic shut-off valve, and a gas phase pressure gauge and a pressure sensor are provided on the upstream pipeline of the shut-off valve. The discharge port is used to control the pressure in the equipment. If the pressure in the equipment is too high, it is necessary to discharge excess gas or liquid medium through the discharge port.

[0015] Optionally, the inlet and outlet liquid interface includes: the inlet and outlet liquid interface is an interface provided for receiving and discharging cryogenic propellant. Its specification is an inner diameter of 40mm, connected to a DN40 PN16 cryogenic shut-off valve, and a quick connection interface is provided on the upstream pipeline of the shut-off valve, which is connected to a hose of a cryogenic propellant transport vehicle.

[0016] Optionally, the pressure sensor interface includes: setting pressure and temperature sensors at the lowest point and the highest point of the liquid level gauge to be measured. The position of the liquid level is marked, and the pressure difference generated by the liquid level height difference can be used to measure the liquid level height. It can be matched, compared and calibrated with the measurement results of the capacitive liquid level gauge.

[0017] Optionally, the heat preservation treatment includes: the heat preservation treatment uses a polyurethane foaming process to wrap a 100mm polyurethane foam layer on the outer layer of the device, and then wraps a layer of aluminum material skin outside the polyurethane foam layer. The heat preservation treatment can effectively reduce the boiling and loss of low-temperature propellant and reduce heat exchange with the outside.

[0018] The invention provides a method for calibrating a capacitance type liquid level gauge for cryogenic propellant, and a device for calibrating a capacitance type liquid level gauge for cryogenic propellant based on the invention.

[0019] Optionally, the following steps are included:

[0020] Use room temperature dry nitrogen to purge and replace the air in the equipment to reduce the residual air in the test container and the structure of the capacitive level gauge to be tested. When the dew point value measured at the discharge port is no greater than -55.0℃dp time, the nitrogen purge work is completed;

[0021] Optionally include:

[0022] Connect the liquid inlet and outlet to the liquid outlet of the cryogenic propellant filling vehicle, and use the pressure inside the cryogenic propellant filling vehicle to pre-cool and fill the liquid level gauge calibration equipment with cryogenic propellant. At this time, the liquid level of the cryogenic propellant will reduce boiling and the liquid level will rise as the temperature decreases. At this time, the capacitance value of the corresponding liquid level should be measurable on the capacitive liquid level gauge to be calibrated.

[0023] The technical solution of the present invention has the following advantages:

[0024] 1. The capacitance level gauge calibration device for cryogenic propellant provided by the present invention comprises: a container for containing cryogenic propellant, a liquid inlet and outlet interface arranged below the container, and a detachable flange connection form at the upper end of the container, which can be replaced with connection interfaces with different functions. The device is provided with a liquid level gauge installation interface, a discharge interface, and a window interface. The discharge interface is provided with a cryogenic valve. The outside of the device is subjected to heat preservation treatment.

[0025] 2. This device takes into account the boiling of cryogenic propellant at room temperature, and performs heat preservation treatment on the equipment to keep the cryogenic propellant below the boiling point inside the device, ensuring that there is an obvious liquid surface of the cryogenic propellant, providing an ideal measurement environment for calibrating the capacitive level meter.

[0026] 3. Set up an optical sensor interface and observation hole to provide image visual reference for the optical sensor to judge the liquid level online, so as to quickly and accurately calibrate the liquid level meter.

[0027] 4. Set high liquid level and low liquid level pressure measuring points, use the pressure difference to calculate the liquid level height, and measure the liquid level using different means. The measurement results are used to calibrate the capacitive level meter.

[0028] 5. In the dew point monitoring device for the liquid nitrogen supply system of the low-temperature test chamber provided by the present invention, a one-way valve is installed on the measuring pipeline downstream of the dew point monitoring component, which can effectively prevent air backflow from contaminating the dew point monitoring device. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 Schematic diagram of a capacitive level gauge calibration device for cryogenic propellants in an embodiment of the present invention.

[0031] Figure 2 It is a schematic structural diagram of a capacitive level gauge calibration device for cryogenic propellants in an embodiment of the present invention.

[0032] Description of reference numerals: 1. Quick connection interface; 2. Low-temperature stop valve for inlet and outlet liquid; 3. Polyurethane insulation; 4. Test container; 5. Container cover; 6. Discharge low-temperature stop valve; 7. Gas phase pressure sensor; 8. Gas phase pressure gauge; 9. Capacitive level gauge interface; 10. Observation window interface; 11. Upper liquid level pressure sensor; 12. Upper liquid level temperature sensor; 13. Capacitive level gauge; 14. Lower liquid level pressure sensor; 15. Lower liquid level temperature sensor; DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0035] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0037] Figure 1 to Figure 2The figure shows a dew point monitoring device for a liquid nitrogen supply system of a low-temperature test chamber provided in this embodiment.

[0038] Install the standard section of the capacitive level gauge to be calibrated at 9, the capacitive level gauge interface; tighten all connecting flanges. Connect the cryogenic propellant tank truck quick connector to 1, the quick connection interface. Open the purge valve of the propellant tank truck, open the device 2, the inlet and outlet cryogenic shut-off valve, allow the gas to enter the test device, and open 6, the discharge cryogenic shut-off valve to replace the gas in the device. After about 5 minutes, close the purge valve of the cryogenic propellant tank truck and stop the replacement. Open the liquid outlet valve of the cryogenic propellant tank truck and fill the device with cryogenic propellant. As the device gradually cools, the propellant level rises slowly. At this time, read the liquid level reading of 13, the capacitive level gauge, and compare it with the liquid level calculated by the difference between the pressure of 11, the upper liquid level pressure sensor; 14, the lower liquid level pressure sensor, and adjust the liquid level corresponding to the capacitance of the capacitive level gauge.

[0039] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

[0040] Due to the low temperature characteristics and operational safety of liquid oxygen at -183℃, liquid nitrogen at -196℃, and liquid hydrogen at -253℃, the existing domestic measurement and calibration devices are unable to calibrate the capacitive level gauge with real media, and are also unable to accurately provide the measurement accuracy of the capacitive level gauge in a cryogenic propellant environment, and cannot be regularly calibrated.

[0041] Therefore, the technical problem to be solved by the present invention is to overcome the defect in the prior art that real cryogenic propellant cannot be used to safely and effectively calibrate a capacitive liquid level gauge, thereby providing a capacitive liquid level gauge calibration device and method for cryogenic propellant.

Claims

1. A capacitive level gauge calibration device for cryogenic propellants, characterized in that: The low temperature test chamber liquid nitrogen supply system comprises a liquid nitrogen storage tank (15), a system pipeline, a supply pipeline, a test chamber body (17) and a supply return pipeline which are cyclically connected, wherein the outlet of the supply return pipeline is connected to the inlet of the liquid nitrogen storage tank (15); The capacitive liquid level gauge calibration device for cryogenic propellant comprises a test container (4), liquid inlet and outlet pipelines, liquid inlet and outlet cryogenic stop valves (2), a capacitive liquid level gauge (13), an upper liquid level temperature sensor (12), a lower liquid level temperature sensor (15), and upper and lower limit pressure sensors. The temperature sensor and the pressure sensor are installed on the bottom and outer wall of the test container, the liquid level sensor is installed in the tank, and the liquid level transmitter and the liquid level gauge are connected to each other through a special through-tank plug. The device is mainly composed of a test container (4) containing cryogenic propellant, a quick liquid inlet and outlet connection port (1) is arranged at the bottom of the container, and a detachable flange connection is adopted at the upper end of the container, which can be replaced with connection interfaces with different functions. The device is provided with a liquid level gauge installation interface, a discharge interface, and a window interface (10). The discharge interface is provided with a cryogenic stop valve (6). The outside of the device is treated with polyurethane insulation (3). The installation interface of the level gauge includes: The installation interface specification of the level meter is 80mm inner diameter, which meets the maximum outer diameter requirement of the level meter installation. The connection form of the level meter is RFBL flange blind plate connection form, and a special terminal is set on the blind plate to lead out the measurement signal of the level meter. The terminal is insulated from the measuring container and connected to the level meter.

2. The capacitive level gauge calibration device for cryogenic propellants according to claim 1, characterized in that: The flange blind plate can be processed according to the connection size of the level gauge to ensure the interface fits and the connection is reliable.

3. The capacitive level gauge calibration device for cryogenic propellants according to claim 1 or 2, characterized in that: The special wiring terminals on the blind plate can select high-voltage wiring terminals according to different test pressures.

4. The capacitive level gauge calibration device for cryogenic propellants according to claim 1 or 2, characterized in that: The window interface (10) is an interface provided for observing and verifying the liquid level using an optical sensor. Its specification is an inner diameter of 40 mm, and the window interface is formed by two metal flanges clamping high-strength glass. The high-strength glass in the window interface (10) can also be replaced with a metal blind plate or other sensors.

5. The capacitive level gauge calibration device for cryogenic propellants according to claim 1, characterized in that: The discharge interface includes: the discharge interface is an interface set up to discharge boiling and vaporized cryogenic propellant. Its specification is an inner diameter of 40mm, connected to a DN40 PN16 cryogenic stop valve (6), and a gas phase pressure gauge and a pressure sensor (7) are set on the upstream pipeline of the stop valve. The discharge port is used to control the pressure in the equipment. If the pressure in the equipment is too high, it is necessary to discharge excess gas or liquid medium through the discharge port.

6. The capacitive level gauge calibration device for cryogenic propellants according to claim 1, characterized in that: The inlet and outlet liquid interfaces include: the inlet and outlet liquid interfaces are interfaces provided for receiving and discharging cryogenic propellants. The specifications are 40 mm in inner diameter, connected to a DN40 PN16 cryogenic shut-off valve (2), and a quick connection interface (1) is provided on the upstream pipeline of the shut-off valve, connected to a hose of a cryogenic propellant transport vehicle.

7. The capacitive level gauge calibration device for cryogenic propellants according to claim 1, characterized in that: The pressure sensor interface comprises: setting pressure (11 and 14) and temperature sensors (12 and 15) at the lowest point and the highest point of the liquid level meter to be measured, marking the position of the liquid level, and using the pressure difference generated by the liquid level height difference to measure the liquid level height, which can be matched, compared and calibrated with the measurement result of the capacitive liquid level meter (13).

8. The capacitive level gauge calibration device for cryogenic propellants according to claim 1, characterized in that: Polyurethane insulation treatment includes: the insulation treatment uses polyurethane foaming technology to wrap a 100mm polyurethane foam layer on the outer layer of the device, and then wraps a layer of aluminum skin outside the polyurethane foam layer. The insulation treatment can effectively reduce the boiling and loss of low-temperature propellants and reduce heat exchange with the outside world.

9. A method for calibrating a capacitive level gauge for cryogenic propellants, characterized in that: The following steps are involved: The air in the equipment is purged and replaced by dry nitrogen at room temperature to reduce the residual air in the test container (4) and the structure of the capacitive level meter (13) to be tested. The nitrogen purging work is completed when the dew point value measured at the discharge port is not greater than -55.0°C dp time.

10. The method for calibrating a capacitive level gauge for cryogenic propellants according to claim 9, characterized in that: include: The liquid inlet and outlet are connected to the liquid outlet of the cryogenic propellant filling vehicle, and the pressure inside the cryogenic propellant filling vehicle is used to pre-cool and fill the liquid level gauge calibration equipment with cryogenic propellant. At this time, the liquid level of the cryogenic propellant will reduce boiling and the liquid level will rise as the temperature decreases. At this time, the capacitance value of the corresponding liquid level should be measured on the capacitive liquid level gauge (13) to be calibrated.

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