CN-122014992-A - LNG filling control strategy, system and LNG filling station for gas station

CN122014992ACN 122014992 ACN122014992 ACN 122014992ACN-122014992-A

Abstract

The invention discloses an intelligent filling control strategy and system for an LNG (liquefied Natural gas) filling station and the LNG filling station, comprising the following steps of obtaining the actual temperature T of LNG in a liquid outlet pipeline from a storage tank to a pump pool and the actual pressure P of a gas phase space in the storage tank; inquiring a built-in LNG saturation characteristic curve according to the actual pressure P to obtain a corresponding saturation temperature Ts (P), comparing the actual temperature T with the saturation temperature Ts (P), judging whether the thermodynamic state of the LNG is an undersaturated state, a saturated state or a supersaturated state, and executing a corresponding filling control strategy according to the thermodynamic state. The invention realizes intelligent protection of the immersed pump and dynamic optimization of the filling process.

Inventors

Quan bing
ZHAO YU
HU MENGHAN
ZHANG JINGXING
LUO YANG

Assignees

中石化石油机械股份有限公司
中石化氢能机械(武汉)有限公司

Dates

Publication Date: 20260512
Application Date: 20260130

Claims (10)

1. An intelligent filling control strategy for an LNG filling station is characterized by comprising the following steps: Acquiring the actual temperature T of LNG in a liquid outlet pipeline from a storage tank to a pump pool and the actual pressure P of a gas phase space in the storage tank; Inquiring a built-in LNG saturation characteristic curve according to the actual pressure P to obtain a corresponding saturation temperature T s (P); comparing the actual temperature T with the saturation temperature T s (P), and judging the thermodynamic state of the LNG to be an undersaturated state, a saturated state or a supersaturated state; executing a corresponding filling control strategy according to the thermodynamic state: If the state is in an undersaturated state, controlling filling by adopting a mode of starting a immersed pump in a frequency-reducing way or starting a self-pressurization system of the storage tank; if the state is saturated, adopting a constant pressure filling mode; And if the filling rate is in the supersaturation state, dynamically increasing the output pressure on the basis of the constant pressure mode so as to increase the filling rate.
2. An intelligent fill control strategy for LNG fueling stations as set forth in claim 1, wherein said determining the thermodynamic state comprises: If T > T s (P), judging that the state is in an undersaturated state; If t=t s (P), determining that the vehicle is in a saturated state; If T < T s (P), it is determined that the supersaturation state is established.
3. An intelligent fill control strategy for an LNG fueling station as set forth in claim 1, wherein said undersaturated fill control strategy comprises any of the following: Starting filling by 50% -80% of rated frequency of the immersed pump, monitoring the flow and pressure of the pump outlet in real time, stopping the pump and alarming if the flow is reduced to less than 10% of rated flow or the pressure is zero; And starting a storage tank self-pressurization system, lifting the pressure in the storage tank to saturation pressure P s (T) corresponding to the current temperature T, and switching to a constant pressure mode for filling after the LNG is converted into a saturated state.
4. An intelligent fill control strategy for an LNG fueling station as set forth in claim 1, wherein said fill control strategy in a supersaturated state comprises: Starting constant pressure filling at a preset initial output pressure; and monitoring the muzzle pressure of the gas filling machine in real time, and if the muzzle pressure is lower than a set lower limit, gradually increasing the output pressure of the immersed pump until the muzzle pressure reaches a set upper limit.
5. An intelligent filling control strategy for LNG fueling stations as set forth in claim 4, wherein said set lower limit is 1.3MPa, said set upper limit is 1.6MPa, and said initial output pressure is 1.4MPa.
6. An intelligent filling control system for an LNG gas station, comprising: The temperature sensor is arranged on a liquid outlet pipeline from the storage tank to the pump pool and is used for collecting the actual temperature T of LNG; the pressure sensor is arranged in the gas phase space at the top of the storage tank and is used for collecting the actual pressure P in the storage tank; The controller is internally provided with an LNG saturation characteristic curve and is used for judging the thermodynamic state of LNG according to T and P and outputting corresponding control instructions; The immersed pump is controlled by the controller and is used for executing filling operation; and the storage tank self-pressurization system is connected with the controller and is used for increasing the pressure of the storage tank in an undersaturated state.
7. The system of claim 6, further comprising a dispenser data acquisition module for acquiring in real time a fill pressure at the dispenser and feeding back to the controller.
8. The system of claim 6, wherein the controller is further configured to control the immersed pump to operate at 50% -80% of the nominal frequency in an undersaturated condition and monitor pump outlet flow and pressure and trigger an alarm in the event of an anomaly.
9. The system of claim 6, wherein the controller controls the immersed pump in the supersaturated state to gradually increase the output pressure on a constant pressure mode basis until the dispenser nozzle pressure reaches a set upper limit.
10. An LNG fueling station comprising the intelligent fueling control system of any one of claims 6-9.

Description

LNG filling control strategy, system and LNG filling station for gas station Technical Field The invention relates to the field of filling of an automobile LNG (liquefied Natural gas) filling station. More particularly, the present invention relates to an intelligent filling control strategy for LNG fueling stations. Background With the improvement of environmental protection requirements and the consideration of fuel economy, the market application of LNG heavy trucks is continuously growing, and the demands and the developments of LNG filling stations and related skid-mounted equipment are promoted. The thermodynamic properties of the cryogenic fluid during LNG refueling have a decisive impact on operational safety and efficiency. At present, a filling control strategy commonly adopted in the industry is mainly a single constant pressure mode, namely, a system fills with a fixed or preset pressure target, and the gas-liquid balance state of LNG in a storage tank and a pump pool is not considered in real time. The simple control mode has the obvious defects that when LNG is in an undersaturated state, flash evaporation cavitation is easily caused in a flow channel when the immersed pump runs, the pump speed is increased for maintaining the pressure by the system, a vicious circle for aggravating cavitation is formed, and finally the pump body is damaged and the filling is interrupted, and when LNG is in a supersaturated stable liquid phase state, the characteristics of strong cavitation resistance are not fully utilized by single pressure control, so that the improvement of the filling flow is limited, and the filling efficiency is not optimal. Therefore, a control strategy capable of sensing LNG thermodynamic states and intelligently adjusting is needed to solve the equipment safety and filling efficiency problems at the same time. Disclosure of Invention The invention aims to solve the problems of cavitation risk and low efficiency caused by the adoption of a single constant pressure filling mode in the conventional LNG filling station. The intelligent protection of the immersed pump and the dynamic optimization of the filling process are realized by identifying the saturation state of the LNG in real time and matching with the differentiated filling control strategy according to the saturation state. Therefore, the overall efficiency of the filling operation is obviously improved while the safety of the equipment is ensured and the service life of the equipment is prolonged. The technical scheme adopted by the invention for solving the technical problem is that an intelligent filling control strategy for an LNG gas station comprises the following steps: Acquiring the actual temperature T of LNG in a liquid outlet pipeline from a storage tank to a pump pool and the actual pressure P of a gas phase space in the storage tank; Inquiring a built-in LNG saturation characteristic curve according to the actual pressure P to obtain a corresponding saturation temperature T s (P); comparing the actual temperature T with the saturation temperature T s (P), and judging the thermodynamic state of the LNG to be an undersaturated state, a saturated state or a supersaturated state; executing a corresponding filling control strategy according to the thermodynamic state: If the state is in an undersaturated state, controlling filling by adopting a mode of starting a immersed pump in a frequency-reducing way or starting a self-pressurization system of the storage tank; if the state is saturated, adopting a constant pressure filling mode; And if the filling rate is in the supersaturation state, dynamically increasing the output pressure on the basis of the constant pressure mode so as to increase the filling rate. The invention further provides a method for judging the thermodynamic state, which specifically comprises the following steps: If T > T s (P), judging that the state is in an undersaturated state; If t=t s (P), determining that the vehicle is in a saturated state; if T < T s (P), it is determined that the supersaturation state is established. The filling control strategy in the undersaturation state comprises any one of the following steps: Starting filling by 50% -80% of rated frequency of the immersed pump, monitoring the flow and pressure of the pump outlet in real time, stopping the pump and alarming if the flow is reduced to less than 10% of rated flow or the pressure is zero; and starting a storage tank self-pressurization system, lifting the pressure in the storage tank to saturation pressure P s (T) corresponding to the current temperature T, and switching to a constant pressure mode for filling after the LNG is converted into a saturated state. The filling control strategy in the supersaturation state comprises the following steps: Starting constant pressure filling at a preset initial output pressure; and monitoring the muzzle pressure of the gas filling machine in real time, and if the muzzle pressure i