A hull vented air layer drag reduction system

Abstract

The application discloses a ship bottom air layer drag reduction system, which comprises a high-pressure air supply system and an intelligent monitoring and control system; the high-pressure air supply system is composed of a gas supply system, a pressure stabilizing system and a jet system, and is arranged on a ship body to form a spread air layer on a ship bottom surface; the intelligent monitoring and control system comprises a pre-flow field monitoring system and an intelligent control and management system; the pre-flow field monitoring system is arranged on the ship body to capture real flow velocity changes of the ship bottom surface upstream of the jet system; the intelligent control and management system is signal-connected with the pre-flow field monitoring system, receives the flow velocity changes captured by the pre-flow field monitoring system, and feeds back to the high-pressure air supply system in real time to regulate and control the air supply rate, so that the air layer is stably spread. The application can accurately capture the pre-flow field flow velocity in real time and feed back, and then finely adjusts the flow velocity changes of an outflow field in self-adaption, so that the air cavity can continuously and extensively cover the ship bottom, and the air layer spread efficiency is improved.

Description

Technical Field

[0001] This invention relates to a drag reduction system for a ship bottom ventilation layer, belonging to the field of marine ventilation technology. Background Technology

[0002] In today's global context of energy conservation and emission reduction, and based on national energy development and utilization strategies, the country is undertaking structural upgrading and reforms for the shipbuilding industry and international shipping, which also poses new requirements for the shipbuilding and shipping sectors. The International Maritime Organization (IMO) has formulated a detailed phased policy plan for energy conservation and emission reduction in international shipping, using 2008 carbon emissions as a baseline, projecting a 40% reduction in global shipping carbon intensity by 2030 and a 70% reduction by 2050. Furthermore, starting January 1, 2023, the Convention on the Prevention of Pollution from Air Pollution (CPA) will mandate in its amendments that all ships calculate their existing Energy Efficiency Index (EEXI) to measure their energy efficiency. my country has approximately 125,900 water transport vessels, of which over 1,000 international vessels of 5,000 gross tons or more will fully implement this rule; however, energy efficiency management for domestic civilian vessels is still in its initial stages. In order to actively respond to international shipping emission reduction standards and the national goal of "carbon peaking and carbon neutrality", the research on green shipping transformation and ship energy-saving and drag reduction technologies has important practical significance.

[0003] As is well known, the resistance experienced by ships during navigation can be classified into three categories based on their causes: first, wave-making resistance caused by the wave motion of the surrounding flow field resulting from the ship's forward propulsion; second, pressure difference resistance caused by the difference in the longitudinal lines of the hull; and third, frictional resistance between the hull below the waterline and the surrounding fluid. Among these, frictional resistance can account for 60-80% of the total resistance at low speeds and 30-50% at high speeds. Flow control technology is a major research hotspot in the field of hydrodynamics for high-speed vessels, and active ventilation technology is well-known among researchers as an easy-to-implement and efficient method. This technology uses a high-pressure chamber built into the hull to release non-condensable gas to cover the lower surface of the hull, utilizing the interaction between the gas layer and the surrounding liquid flow field to regulate the complex external flow field. Due to the significant difference in inherent properties between the gas layer and the external flow field, the complete spread of the gas layer can greatly reduce the direct contact area between the hull and the external flow field, making it an effective means of reducing navigation friction.

[0004] Currently, typical active ventilation technology uses relatively simple control methods: high-pressure gas is introduced into the external flow field through pre-set holes on the hull surface at a given ventilation rate via a pipeline system using an air compressor, creating an air layer. The hole layout is then adjusted to maximize air layer spread. Since the air layer density is much lower than the external flow field, the boundary flow pattern can be altered to transform a solid-liquid non-slip boundary into a shear-free slip boundary. However, the ship's speed and the velocity distribution of the external flow field at the hull are not constant. Existing gas flow control systems have limited development and cannot make adaptive, fine adjustments to adapt to changes in the external flow field velocity, resulting in less than ideal drag reduction performance. Therefore, it is essential to propose a novel hull ventilation system capable of stable air layer spread. Summary of the Invention

[0005] The technical problem that this invention aims to solve is that the control methods of typical active ventilation technologies are relatively simple. However, for complex navigation conditions, the development of existing ventilation systems is very limited, and they cannot make adaptive and fine adjustments to changes in the external flow velocity, resulting in unsatisfactory actual drag reduction performance.

[0006] To address the aforementioned technical problems, this invention provides a drag reduction system for a ship bottom ventilation air layer. Based on a conventional constant flow rate ventilation device, a preceding flow field velocity measurement system is coupled to capture the flow velocity changes on the ship bottom surface upstream of the ventilation hole and adjust the ventilation rate in real time to achieve stable air layer spreading.

[0007] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0008] This invention provides a drag reduction system for a ship's bottom ventilation layer, 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 stabilization system, and an air jet system, and is arranged on the hull to form a uniformly spread air layer on the bottom surface. The intelligent monitoring and control system includes a preceding flow field monitoring system and an intelligent control and management system. The preceding flow field monitoring system is installed on the hull to capture the actual flow velocity changes on the bottom surface upstream of the air jet system. The intelligent control and management system is signal-connected to the preceding flow field monitoring system to receive the flow velocity changes captured by the preceding flow field monitoring system and feed them back to the high-pressure ventilation system in real time to adjust the ventilation rate so that the air layer can achieve stable spread.

[0009] Preferably, the air supply system includes an air supply device, the pressure stabilizing system includes an air venting pipeline and an air venting controller, the jet system includes a jet nozzle and air cavities, the air supply device is installed in the hull and is connected to the air venting controller through the air venting pipeline, multiple air cavities are provided and evenly distributed at intervals on the bottom of the hull, multiple air cavities are connected to the air venting controller through the air venting pipeline, and multiple jet nozzles are correspondingly connected to multiple air cavities.

[0010] Furthermore, the gas supply system also includes vibration damping and noise reduction accessories, which are disposed between the gas supply equipment and the gas flow controller.

[0011] Furthermore, the jet nozzle includes a diffusion-contraction section for controlling the outflow attitude of the high-pressure gas, and a backflow prevention device is provided between the cavitation and the ventilation controller.

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

[0013] Furthermore, the preceding flow field monitoring system includes velocity sensors, a data acquisition unit, and a centralized control device. Multiple velocity sensors are arranged upstream of the jet nozzles on the hull bottom to monitor the near-wall velocity distribution of the preceding flow field on the hull bottom in real time. The data acquisition unit and centralized control device are both located inside the hull. The data acquisition unit is connected to both the velocity sensors and the centralized control device. The data acquisition unit filters the flow field data it collects and feeds it back to the centralized control device. The centralized control device analyzes the flow pattern distribution in the air chamber and obtains the optimal ventilation parameters. The centralized control device is connected to the ventilation controller.

[0014] Furthermore, the intelligent control and management system includes a gas flow meter, a flow control gate valve, and a control unit. The control unit is installed inside the ship's cabin and electrically connected to the centralized control equipment. The control unit is signal-connected to the ventilation controller. The flow control gate valve is installed between the gas pressure stabilizing chamber and the cavitation chamber and is signal-connected to the control unit. The gas flow meter is installed between the flow control gate valve and the cavitation chamber and is signal-connected to both the control unit and the data acquisition instrument.

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

[0016] Furthermore, the speed sensor is mounted on the flat bottom of the boat.

[0017] Furthermore, the gas supply device is connected to an oil-gas separator at its air inlet.

[0018] The drag reduction system for the hull ventilation layer provided by this invention has the following advantages:

[0019] Compared with existing hull ventilation systems, the drag reduction system for hull bottom ventilation of this invention, due to the inclusion of a preceding flow field monitoring system and an intelligent control and management system, can accurately capture and provide feedback on the preceding flow field velocity in real time, ensuring that the air cavity can continuously and extensively cover the hull bottom. Model tests show that, under normal circumstances, it can improve the spreading efficiency of the air cavity by 5-20%. Attached Figure Description

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

[0021] Figure 2 This is a schematic diagram of a drag reduction system for a hull ventilation layer provided in an embodiment of the present invention;

[0022] Figure 3 The existing distribution patterns and classification groups of air chamber flow regimes. Figure 1 ;

[0023] Figure 4 The existing distribution patterns and classification groups of air chamber flow regimes. Figure 2 ;

[0024] In the picture:

[0025] 1-Gas supply equipment; 2-Gas pipeline; 3-Gas controller; 4-Air nozzle; 5-Gas 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 Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Reference Figure 1 and Figure 2 This application provides a drag reduction system for a ship's bottom ventilation layer, comprising 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 a jet injection system. The high-pressure ventilation system is installed on the hull to form a spreading air layer on the ship's bottom surface. The intelligent monitoring and control system consists of two secondary systems: a preceding flow field monitoring system and an intelligent control and management system. The preceding flow field monitoring system is installed on the hull to capture the actual flow velocity changes on the ship's bottom surface upstream of the jet injection system. The intelligent control and management system is signal-connected to the preceding flow field monitoring system to receive the flow velocity changes captured by the preceding flow field monitoring system and feed them back to the high-pressure ventilation system in real time to adjust the ventilation rate to ensure stable air layer spreading.

[0028] Reference Figure 1 and Figure 2The air supply system includes an air supply device 1, a pressure stabilizing system includes an air venting pipe 2 and an air venting controller 3, and an air jet system includes an air jet nozzle 4 and air cavities 5. The air supply device 1 is installed in the hull and connected to the air venting controller 3 through the air venting pipe 2. Multiple air cavities 5 are installed on the bottom of the hull through hull adapters and are evenly spaced. Multiple air cavities 5 are connected to the air venting controller 3 through the air venting pipe 2. Multiple air jet nozzles 4 are connected to the corresponding air cavities 5. Before the high-pressure air from the air supply device 1 is introduced into the air venting pipe 2, it needs to be connected to an oil-gas separator to filter out tiny droplets through gravity settling, collision separation and centrifugal separation to prevent damage to the air venting pipe 2 and system equipment.

[0029] Furthermore, the air supply system also includes vibration-damping and noise-reducing accessories (not shown in the figure). Since the entire system needs to operate on board the ship for extended periods, vibration-damping and noise-reducing accessories are required when the air supply equipment 1 and devices such as the ventilation controller 3 are connected via the ventilation pipeline 2 to reduce hull vibration and noise. This, in turn, improves the stability of the high-pressure ventilation system during long-term operation.

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

[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 rate of high-pressure gas can remain balanced and stable for a long time, the gas pressure stabilizing chamber 6 must be introduced before the gas enters the system. After the pressure in the chamber reaches the rated value, the ventilation controller 3 is operated to introduce 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 central control device 9. Multiple velocity sensors 7 are installed on the bottom of the ship, corresponding to the jet nozzles 4, and arranged upstream of the jet nozzles 4. Based on the experience of model tests, in order not to disrupt the streamline trajectory of the original external flow field, it is necessary to ensure that the bottom plane at the installation position of the velocity sensor 7 is as smooth as possible, without protrusions or depressions. The data acquisition instrument 8 and the central control device 9 are both installed in the ship cabin. The data acquisition instrument 8 is connected to the velocity sensor 7 and the central control device 9 respectively, and the central control device 9 is connected to the ventilation controller 3.

[0033] When the ship is sailing normally, the speed sensor 7 transmits the monitored flow field data to the data acquisition instrument 8. The data acquisition instrument 8 filters the flow field data and feeds it back to the central control device 9. The central control device 9 analyzes the flow distribution law of the air cavity and inversely calculates the ventilation parameters corresponding to the optimal air cavity flow state under the current incoming flow state. In this embodiment, the use and control principle of the speed sensor 7, the data acquisition instrument 8 and the central control device 9 are all existing designs and will not be described in detail.

[0034] Reference Figure 1 and Figure 2 The intelligent control and 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 ship's cabin and electrically connected to the central control equipment 9. The control unit 12 is signal-connected to the ventilation controller 3. The flow control gate valve 11 is installed between the gas pressure stabilizing chamber 6 and the cavitation chamber 5 and is signal-connected to the control unit 12. The gas flow meter 10 is installed between the flow control gate valve 11 and the cavitation chamber 5 and is signal-connected to the control unit 12 and the data acquisition instrument 8, respectively.

[0035] When the ship is sailing normally, the centralized control equipment 9 infers the ventilation parameters corresponding to the optimal air chamber flow state under the current incoming flow state, and then the control unit 12 adjusts the flow control gate valve 11 in real time based on the gas flow meter 10 to achieve a large coverage rate and long duration of the artificial ventilation air chamber, 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 inside the gas pressure stabilizing chamber 6. The early warning device is connected to the central control equipment 9. After the pressure inside the chamber reaches the rated value, the central control equipment 9 operates the ventilation controller 3 through the control unit 12 to introduce gas into the ventilation pipeline 2. If the pressure inside the chamber is insufficient due to equipment malfunction, the early warning device will feed back the information to the central control equipment 9 for the operator to handle. In this embodiment, a general pressure early warning device can be used. The use and control principle of the gas flow meter 10, the flow control gate valve 11 and the control unit 12 are all existing technologies and will not be described in detail.

[0037] Based on the study of the pulsating morphology of the underwater plate-shaped orifice ventilation chamber, this invention further investigates the relationship between the flow regime and typical flow parameters of the orifice ventilation film air layer on a finite-area plate, referring to... Figure 3 and Figure 4Because the flow pattern and spread rate distribution of the air layer exhibit certain scale effects, a preliminary similarity rate of the air cavity flow pattern can be established through numerical and experimental studies at the ship scale. Achieving stable and continuous spread of the air layer through small orifices on the ship's bottom requires not only consideration of the ship's bottom surface shape but also significant influence from the flow control system. With a fixed inflow velocity and flat plate area, changes in the ventilation rate will alter the morphology of the ventilation cavity. At low ventilation rates, the pulsation phenomenon in the cavity is not obvious, exhibiting a small-area, localized development pattern close to the ship's bottom surface. Increasing the ventilation rate can accelerate gas accumulation at the ship's bottom, but the enhanced pulsation effect of the air jet will also increase the instability of the ventilation cavity and accelerate the gas escape rate. Based on numerical simulation and model experimental research, this invention couples an intelligent monitoring and control system to a conventional constant-flow-rate high-pressure ventilation system. This system captures the actual flow velocity changes on the ship's bottom surface upstream of the jet nozzle 4, providing real-time feedback and adjusting the ventilation rate to achieve stable air layer spread.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A drag reduction system for a ship's bottom ventilation layer, characterized in that, The system 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 stabilization system, and a jetting system. The high-pressure ventilation system is installed 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 and management system. The preceding flow field monitoring system is installed on the hull to capture the actual flow velocity changes on the bottom surface upstream of the jetting system. The intelligent control and management system is signal-connected to the preceding flow field monitoring system to receive the flow velocity changes captured by the preceding flow field monitoring system and feed them back to the high-pressure ventilation system in real time to adjust the ventilation rate so that the air layer spreads stably. The air supply system includes an air supply device, the pressure stabilizing system includes an air venting pipeline and an air venting controller, the jet system includes a jet nozzle and an air cavitation. The air supply device is installed inside the hull and is connected to the air venting controller through the air venting pipeline. Multiple air cavities are provided and evenly distributed at intervals on the bottom of the hull. Multiple air cavities are connected to the air venting controller through the air venting pipeline. Multiple jet nozzles are connected to multiple air cavities. A gas pressure stabilizing chamber is connected between the ventilation controller and the air cavitation. The preceding flow field monitoring system includes velocity sensors, a data acquisition unit, and a centralized control device. Multiple velocity sensors are arranged upstream of the jet nozzles on the hull bottom to monitor the near-wall velocity distribution of the preceding flow field on the hull bottom in real time. The data acquisition unit and centralized control device are both located inside the hull. The data acquisition unit is connected to both the velocity sensors and the centralized control device. The data acquisition unit filters the flow field data it collects and feeds it back to the centralized control device. The centralized control device analyzes the flow pattern distribution in the air chamber and obtains the optimal ventilation parameters. The centralized control device is connected to the ventilation controller. The intelligent control and management system includes a gas flow meter, a flow control gate valve, and a control unit. The control unit is installed in the cabin and electrically connected to the centralized control equipment. The control unit is signal-connected to the ventilation controller. The flow control gate valve is installed between the gas pressure stabilizing chamber and the cavitation chamber and is signal-connected to the control unit. The gas flow meter is installed between the flow control gate valve and the cavitation chamber and is signal-connected to both the control unit and the data acquisition instrument.

2. The drag reduction system for a ship's bottom ventilation layer as described in claim 1, characterized in that, The gas supply system also includes vibration damping and noise reduction accessories, which are disposed between the gas supply equipment and the gas control unit.

3. The drag reduction system for a ship's bottom ventilation layer as described in claim 1, characterized in that, The jet nozzle includes a diffusion and contraction section for controlling the outflow attitude of the high-pressure gas, and a backflow prevention device is provided between the cavitation and the ventilation controller.

4. The drag reduction system for a ship's bottom ventilation layer as described in claim 1, characterized in that, The gas pressure stabilizing chamber is equipped with an early warning device for monitoring the pressure inside the gas pressure stabilizing chamber, and the early warning device is connected to the central control equipment via a signal connection.

5. The drag reduction system for a ship's bottom ventilation layer as described in claim 1, characterized in that, The speed sensor is mounted on the flat bottom of the ship.

6. The drag reduction system for a ship's bottom ventilation layer as described in claim 1, characterized in that, The gas supply equipment is connected to an oil-gas separator at its air inlet.

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