Ship bottom ventilation air layer drag reduction system

Abstract

The invention discloses a ship bottom ventilation air layer drag reduction system which comprises a high-pressure ventilation system and an intelligent monitoring control system. The high-pressure ventilation system is composed of an air supply system, a pressure stabilizing system and an air injection system. The high-pressure ventilation system is arranged on the ship body and used for forming a spreading air layer on the ship bottom face. The intelligent monitoring control system comprises a preorder flow field monitoring system and an intelligent control management system. The preorder flow field monitoring system is arranged on a ship body and used for capturing the real flow speed change of the upstream ship bottom face of the air injection system. And the intelligent control management system is in signal connection with the preorder flow field monitoring system and is used for receiving the flow velocity change captured by the preorder flow field monitoring system and feeding back the flow velocity change to the high-pressure ventilation system in real time so as to regulate and control the ventilation rate to enable the air layer to be stably spread. According to the invention, the flow velocity of the preorder flow field can be accurately captured in real time and fed back, so that self-adaptive fine adjustment can be performed according to the flow velocity change of the external flow field, the air cavity can continuously cover the ship bottom in a large area, and the air layer spreading efficiency is improved.

Description

Technical Field

[0001] The invention relates to a ship bottom ventilation air layer drag reduction system, belonging to the technical field of ship ventilation. Background Art

[0002] In today's global environment of energy conservation and emission reduction, based on the energy development and use policy strategy, the country has carried out structural upgrading and reform for the shipbuilding industry and international shipping, which has also put forward new requirements for the shipbuilding and shipping industries. The International Maritime Organization has formulated a relatively detailed phased policy plan for energy conservation and emission reduction in international shipping. Based on the carbon emissions in 2008, it is expected that the total intensity of global shipping carbon emissions will be reduced by 40% in 2030 and 70% in 2050. In addition, starting from January 1, 2023, the "Marlano Convention" in its amendments requires all ships to calculate their existing ship energy efficiency index (EEXI) to measure their energy efficiency. my country has about 125,900 water transport ships, of which more than 1,000 international ships with a gross tonnage of more than 5,000 will fully implement the rules. However, the energy efficiency management of domestic civil ships is still in its infancy. In order to actively respond to international shipping emission reduction regulations and the country's "carbon peak and carbon neutrality" goals, research on green shipping transformation and ship energy conservation and drag reduction technology has important practical significance.

[0003] As we all know, the resistance encountered by ships during navigation can be divided into three categories according to their causes: the first is the wave resistance caused by the wave motion of the surrounding flow field caused by the forward propulsion of the ship; the second is the pressure difference resistance between the bow and stern caused by the difference in the longitudinal lines of the hull; the third is the friction resistance between the hull and the surrounding fluid below the waterline. Among them, the friction resistance can account for 60-80% of the total resistance when the ship moves at low speed, and the friction resistance can account for 30-50% of the total resistance when the ship moves at high speed. The study of flow control technology is a major research hotspot in the field of high-speed navigation body hydrodynamics, and the active ventilation technology is well known to researchers as an easy-to-implement and efficient way. This technology uses the high-pressure air chamber built into the bottom of the ship to pass non-condensable gas to cover the lower surface of the bottom of the ship, and uses the interaction between the air layer and the surrounding liquid phase flow field to control the complex external flow field. Due to the large difference in the inherent properties of the air layer and the external flow field, the air layer can greatly reduce the direct contact area between the hull and the external flow field after it is fully spread, making it an effective means to reduce navigation friction.

[0004] At present, the typical control method of active ventilation technology is relatively simple: by operating the air compressor through the pipeline system, high-pressure gas is allowed to pass into the external flow field from the preset holes on the hull surface at a given ventilation rate under the action of the internal and external pressure difference to produce air layer attachment, and the hole layout scheme is changed to maximize the spread of the air layer. The density of the air layer is much smaller than the external flow field, so the solid-liquid non-slip boundary can be converted into a shear-free slip boundary by changing the boundary flow form. However, the ship's sailing speed and the velocity distribution of the external flow field at the bottom of the ship are not constant. The existing gas flow control system has very limited development and cannot make adaptive fine adjustments to the changes in the velocity of the external flow field, resulting in unsatisfactory actual drag reduction performance. Therefore, it is very necessary to propose a new bottom ventilation system that can achieve stable spreading. Summary of the invention

[0005] The technical problem to be solved by the present invention is that the control means of the current typical active ventilation technology are relatively simple. However, for complex navigation conditions, the development of the existing ventilation system is very limited, and it is impossible to make adaptive and fine adjustments to the changes in the flow velocity of the external flow field, resulting in the problem that the actual drag reduction performance is not ideal.

[0006] In order to solve the above technical problems, the present invention provides a ship bottom ventilation air layer drag reduction system, which is coupled with a set of preceding flow field velocity measurement system on the basis of a conventional constant flow rate ventilation device, so as to capture the flow velocity changes on the bottom surface of the ship upstream of the vent and adjust the ventilation rate in real time to achieve stable spreading of the air layer.

[0007] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0008] The present invention provides a ship bottom ventilation air layer drag reduction system, comprising a high-pressure ventilation system and an intelligent monitoring and control system; the high-pressure ventilation system consists of an air supply system, a pressure stabilizing system and an injection system, and the high-pressure ventilation system is arranged on the hull to form a uniformly spread air layer on the bottom surface of the ship; the intelligent monitoring and control system comprises a preceding flow field monitoring system and an intelligent control management system, and the preceding flow field monitoring system is arranged on the hull to capture the actual flow velocity changes on the bottom surface of the ship upstream of the injection system; the intelligent control management system is connected with the preceding flow field monitoring system signal, and is used to receive the flow velocity changes captured by the preceding flow field monitoring system, and to feed back to the high-pressure ventilation system in real time to adjust the ventilation rate so that the air layer can be stably spread.

[0009] Preferably, the air supply system includes an air supply device, the pressure stabilizing system includes a ventilation pipeline and a ventilation controller, the jet system includes a jet nozzle and an air cavity, the air supply device is arranged in the hull and is connected to the ventilation controller through the ventilation pipeline, a plurality of air cavities are provided and are evenly spaced on the bottom of the ship, a plurality of air cavities are connected to the ventilation controller through the ventilation pipeline, and a plurality of jet nozzles are connected to the air cavities correspondingly.

[0010] Furthermore, the air supply system also includes a vibration reduction and noise reduction accessory, and the vibration reduction and noise reduction accessory is arranged between the air supply equipment and the ventilation controller.

[0011] Furthermore, the gas nozzle includes a diffusion-contraction section for controlling the outflow posture of the high-pressure gas, and a non-return device is provided between the air cavity and the ventilation controller.

[0012] Furthermore, a gas pressure stabilizing chamber is connected between the ventilation controller and the air cavity.

[0013] Furthermore, the preceding flow field monitoring system includes a velocity sensor, a data acquisition instrument and a centralized control device. The velocity sensor is provided in multiple numbers and arranged upstream of the jet nozzle on the bottom of the ship, and is used for real-time monitoring of the near-wall flow velocity distribution of the preceding flow field on the bottom of the ship; the data acquisition instrument and the centralized control device are both arranged in the cabin, and the data acquisition instrument is respectively connected to the velocity sensor and the centralized control device by signal. The data acquisition instrument is used to filter the flow field data collected by the data acquisition instrument and feed it back to the centralized control device. The centralized control device is used to analyze the distribution law of the air cavity flow state and obtain the optimal ventilation parameters. The centralized control device is connected to the ventilation controller by signal.

[0014] Furthermore, the intelligent control management system includes a gas flow meter, a flow control gate valve and a control unit. The control unit is arranged in the cabin and electrically connected to the centralized control equipment. The control unit is connected to the ventilation controller signal. The flow control gate valve is arranged between the gas pressure stabilizing chamber and the cavitation and is connected to the control unit signal. The gas flow meter is arranged between the flow control gate valve and the cavitation and is respectively connected to the control unit and the data acquisition instrument signal.

[0015] Furthermore, the gas pressure stabilizing chamber is provided with an early warning device for monitoring the pressure in the gas pressure stabilizing chamber, and the early warning device is connected to the centralized control equipment by signal.

[0016] Furthermore, the speed sensor is installed on the bottom of the ship with a flat surface.

[0017] Furthermore, the air inlet end of the air supply equipment is connected to an oil-gas separator.

[0018] The present invention provides a ship bottom ventilation air layer drag reduction system, which has the following advantages:

[0019] Compared with the existing ship bottom ventilation system, the ship bottom ventilation air layer drag reduction system of the present invention can accurately capture the flow velocity of the preceding flow field in real time and provide feedback due to the preceding flow field monitoring system and intelligent control management system, ensuring that the air cavity can continuously and widely cover the ship bottom. Model tests show that under normal circumstances, the spreading efficiency of the air cavity can be improved by 5 to 20%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A system composition diagram of a ship bottom ventilation air layer drag reduction system provided by an embodiment of the present invention;

[0021] Figure 2 A schematic diagram of a ship bottom ventilation air layer drag reduction system provided by an embodiment of the present invention;

[0022] Figure 3 The existing ventilation cavity flow pattern distribution law and cavity flow pattern classification group Figure 1 ;

[0023] Figure 4 The existing ventilation cavity flow pattern distribution law and cavity flow pattern classification group Figure 2 ;

[0024] In the figure:

[0025] 1-gas supply equipment; 2-ventilation pipeline; 3-ventilation controller; 4-jet nozzle; 5-cavitation; 6-gas pressure stabilizing chamber; 7-speed sensor; 8-data acquisition instrument; 9-centralized control equipment; 10-gas flow meter; 11-flow control gate valve; 12-control unit. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 technical personnel in this field without creative work are within the scope of protection of the present invention.

[0027] Reference Figure 1 and Figure 2 The present application provides a ship bottom ventilation air layer drag reduction system, including two primary systems: a high-pressure ventilation system and an intelligent monitoring and control system. The high-pressure ventilation system consists of three secondary systems: an air supply system, a pressure stabilization system, and an injection system. The high-pressure ventilation system is arranged on the hull to form a spreading air layer on the bottom surface of the ship; the intelligent monitoring and control system consists of two secondary systems: a preceding flow field monitoring system and an intelligent control management system. The preceding flow field monitoring system is installed on the hull to capture the actual flow velocity changes on the bottom surface of the ship upstream of the injection system; the intelligent control management system is connected to the preceding flow field monitoring system signal, and is used to receive the flow velocity changes captured by the preceding flow field monitoring system, and to provide real-time feedback to the high-pressure ventilation system to adjust the ventilation rate so that the air layer can be stably spread.

[0028] Reference Figure 1 and Figure 2The air supply system includes an air supply device 1, the pressure stabilizing system includes a ventilation pipeline 2 and a ventilation controller 3, the jet system includes an air jet nozzle 4 and an air cavity 5, the air supply device 1 is installed in the hull and is connected to the ventilation controller 3 through the ventilation pipeline 2, a plurality of air pockets 5 are installed through the hull adapter and are evenly spaced on the bottom of the ship, a plurality of air pockets 5 are connected to the ventilation controller 3 through the ventilation pipeline 2, and a plurality of air jet nozzles 4 are correspondingly connected to the air pockets 5. Before the high-pressure air is introduced into the ventilation pipeline 2 from the air supply device 1, an oil-gas separator is required to be connected, and tiny droplets are filtered by gravity sedimentation, collision separation and centrifugal separation to prevent damage to the ventilation pipeline 2 and system equipment.

[0029] Furthermore, the air supply system also includes vibration reduction and noise reduction accessories (not shown in the figure). Since the whole system needs to work with the ship for a long time, the air supply equipment 1 and the ventilation controller 3 and other devices need to be equipped with vibration reduction and noise reduction accessories when connected through the ventilation pipeline 2 to reduce the vibration and noise of the hull, thereby improving the stability of the high-pressure ventilation system during long-term operation.

[0030] Furthermore, the air nozzle 4 includes a diffusion-contraction section for controlling the outflow posture of the high-pressure gas, improving the stability of the air cavity, and reducing gas escape; a non-return device (not shown in the figure) is also installed in the ventilation pipeline 2 between the air cavity 5 and the ventilation controller 3 to prevent the external flow field liquid from entering the pipeline when the system is not in a working state and causing damage to the system equipment and pipeline.

[0031] Furthermore, a gas pressure-stabilizing chamber 6 is installed and connected between the ventilation controller 3 and the air cavity 5. In order to ensure that the flow of high-pressure gas can remain balanced and stable for a long time, the gas must first be introduced into the gas pressure-stabilizing chamber 6 before entering the system. After the pressure in the chamber reaches the rated value, the ventilation controller 3 is operated to pass the gas into the ventilation pipeline 2.

[0032] Reference Figure 1 and Figure 2 The preceding flow field monitoring system includes a velocity sensor 7, a data acquisition instrument 8 and a centralized control device 9. A plurality of velocity sensors 7 are installed corresponding to the air nozzles 4 and arranged at the upstream position of the air nozzles 4 on the bottom of the ship. According to the experience of the model test, in order not to destroy the streamline trajectory of the original external flow field, it is necessary to ensure that the bottom plane of the ship at the installation position of the velocity sensor 7 is smooth as much as possible without protrusions or depressions; the data acquisition instrument 8 and the centralized control device 9 are both installed in the cabin, and the data acquisition instrument 8 is respectively connected to the velocity sensor 7 and the centralized control device 9 by signal, and the centralized control device 9 is connected to the ventilation controller 3 by signal.

[0033] When the ship is sailing normally, the speed sensor 7 will transmit the monitored flow field data to the data acquisition device 8. The data acquisition device 8 will filter the flow field data and then feed it back to the centralized control device 9. The centralized control device 9 will analyze the distribution law of the air cavity flow state and invert the ventilation parameters corresponding to the optimal air cavity flow state under the current incoming flow state. In this embodiment, the use and control principles of the speed sensor 7, data acquisition device 8 and centralized control device 9 are all existing designs and will not be elaborated on.

[0034] Reference Figure 1 and Figure 2 The intelligent control management system includes a gas flow meter 10, a flow control gate valve 11 and a control unit 12. The control unit 12 is installed in the cabin and electrically connected to the centralized control device 9. The control unit 12 is connected to the ventilation controller 3 by signal. The flow control gate valve 11 is installed between the gas pressure stabilizing chamber 6 and the cavitation 5 and is connected to the control unit 12 by signal. The gas flow meter 10 is installed between the flow control gate valve 11 and the cavitation 5 and is respectively connected to the control unit 12 and the data acquisition instrument 8 by signal.

[0035] When the ship is sailing normally, the centralized control equipment 9 inverts the ventilation parameters corresponding to the optimal air cavity flow state under the current incoming flow state, and then adjusts the flow control gate valve 11 in real time based on the gas flow meter 10 through the control unit 12, so as to achieve a large coverage rate and long duration of the artificial ventilation air cavity, thereby improving the drag reduction effect of the ventilation air layer.

[0036] Furthermore, an early warning device (not shown in the figure) is installed on the gas pressure-stabilizing chamber 6 to monitor the pressure in the gas pressure-stabilizing chamber 6. The early warning device is connected to the signal of the centralized control device 9. After the pressure in the chamber reaches the rated value, the centralized control device 9 controls the ventilation controller 3 through the control unit 12 to pass the gas into the ventilation pipeline 2; if the pressure in the chamber is insufficient due to equipment abnormality, the early warning device will feed back the information to the centralized control device 9 for the operator to handle. In this embodiment, the early warning device can adopt a general pressure early warning device, and the use and control principles of the gas flow meter 10, flow control gate valve 11 and control unit 12 are all existing technologies and will not be elaborated in detail.

[0037] Based on the study of the pulsation morphology of the underwater flat plate small hole ventilation cavity, the present invention further studies the law between the flow pattern and typical flow parameters of the small hole ventilation film air layer on the limited area flat plate. Figure 3 and Figure 4, because there is a certain scale effect between the air layer flow state and the spreading rate distribution law, the similarity of the air cavity flow state can be preliminarily established through the numerical and experimental research correction of the actual ship scale. The small hole ventilation air layer on the bottom of the ship realizes stable and continuous spreading. In addition to the requirements on the shape of the bottom surface of the ship, the flow control system also has a great influence. With a fixed incoming flow velocity and a flat plate area, changes in the ventilation rate will cause changes in the morphology of the ventilation cavity. Under a small ventilation rate, the pulsation phenomenon of the air cavity is not obvious, and it presents a local development mode of a small area and close to the bottom surface of the ship. Increasing the ventilation rate can accelerate the accumulation of gas on the bottom of the ship, but the air jet that strengthens the pulsation effect will also increase the instability of the ventilation cavity and accelerate the gas escape rate. Based on numerical simulation and model test research, the present invention couples a set of intelligent monitoring and control systems on the basis of a conventional constant flow rate high-pressure ventilation system to capture the actual flow velocity changes on the bottom surface of the ship upstream of the jet nozzle 4, and real-time feedback and regulation of the ventilation rate to achieve stable spreading of the air layer.

[0038] The above is only a preferred embodiment of the present invention, and is not any formal or substantial limitation of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention. Any technician familiar with this profession, without departing from the spirit and scope of the present invention, can make some changes, modifications and equivalent changes made by using the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A ship bottom ventilation air layer drag reduction system, characterized in that: It includes a high-pressure ventilation system and an intelligent monitoring and control system; the high-pressure ventilation system consists of an air supply system, a pressure stabilizing system and an injection system, the high-pressure ventilation system is arranged on the hull to form a spreading air layer on the bottom surface of the ship; the intelligent monitoring and control system includes a preceding flow field monitoring system and an intelligent control management system, the preceding flow field monitoring system is arranged on the hull to capture the actual flow velocity changes on the bottom surface of the ship upstream of the injection system; the intelligent control management system is connected to the signal of the preceding flow field monitoring system, for receiving the flow velocity changes captured by the preceding flow field monitoring system, and feeding back to the high-pressure ventilation system in real time to adjust the ventilation rate so that the air layer can be stably spread.

2. A ship bottom ventilation air layer drag reduction system as claimed in claim 1, characterized in that: The air supply system includes an air supply device, the pressure stabilizing system includes a ventilation pipeline and a ventilation controller, the jet system includes an air jet nozzle and an air cavity, the air supply device is arranged in the hull and is connected to the ventilation controller through the ventilation pipeline, a plurality of air pockets are provided and are evenly spaced on the bottom of the ship, a plurality of air pockets are connected to the ventilation controller through the ventilation pipeline, and a plurality of air jet nozzles are correspondingly connected to the air pockets.

3. A ship bottom ventilation air layer drag reduction system as claimed in claim 2, characterized in that: The air supply system also includes a vibration reduction and noise reduction accessory, which is arranged between the air supply device and the ventilation controller.

4. A ship bottom ventilation air layer drag reduction system as claimed in claim 2, characterized in that: The gas nozzle comprises a diffusion-contraction section for controlling the outflow posture of the high-pressure gas, and a backflow prevention device is arranged between the gas cavity and the ventilation controller.

5. A ship bottom ventilation air layer drag reduction system as claimed in claim 2, characterized in that: A gas pressure stabilizing chamber is connected between the ventilation controller and the air cavity.

6. A ship bottom ventilation air layer drag reduction system as claimed in claim 5, characterized in that: The preceding flow field monitoring system includes a velocity sensor, a data acquisition instrument and a centralized control device. The velocity sensors are provided in multiple numbers and arranged at the upstream position of the jet nozzle on the bottom of the ship, and are used to monitor the near-wall flow velocity distribution of the preceding flow field on the bottom of the ship in real time; the data acquisition instrument and the centralized control device are both arranged in the cabin, and the data acquisition instrument is respectively connected to the velocity sensor and the centralized control device by signal. The data acquisition instrument is used to filter the flow field data collected by the data acquisition instrument and feed it back to the centralized control device. The centralized control device is used to analyze the distribution law of the air cavity flow state and obtain the optimal ventilation parameters. The centralized control device is connected to the ventilation controller by signal.

7. A ship bottom ventilation air layer drag reduction system as claimed in claim 6, characterized in that: The intelligent control management system includes a gas flow meter, a flow control gate valve and a control unit. The control unit is arranged in the cabin and electrically connected to the centralized control equipment. The control unit is connected to the ventilation controller signal. The flow control gate valve is arranged between the gas pressure stabilizing chamber and the cavitation and is connected to the control unit signal. The gas flow meter is arranged between the flow control gate valve and the cavitation and is respectively connected to the control unit and the data acquisition instrument signal.

8. A ship bottom ventilation air layer drag reduction system as claimed in claim 6, characterized in that: The gas pressure stabilizing chamber is provided with an early warning device for monitoring the pressure in the gas pressure stabilizing chamber, and the early warning device is connected to the centralized control equipment by signal.

9. A ship bottom ventilation air layer drag reduction system as claimed in claim 6, characterized in that: The speed sensor is installed on the bottom of the ship with a flat surface.

10. A ship bottom ventilation air layer drag reduction system as claimed in claim 2, characterized in that: The air inlet end of the air supply equipment is connected to an oil-gas separator.

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