LNG ship liquid cargo hold based on large intestine structure

Abstract

The application discloses an LNG ship liquid cargo tank based on a large intestine structure, wherein a spherical main screen wall comprises a main screen wall body and a heat insulation material layer. A wall surface of the main screen wall body is in a large intestine wall structure, and an outer surface of the main screen wall body is coated with the heat insulation material layer. A hemispherical secondary screen wall covers an upper hemisphere of the spherical main screen wall. A pipe tower vertically penetrates from a top of the hemispherical secondary screen wall to an inside of the spherical main screen wall. The spherical main screen wall is embedded in a groove of a circular opening of a ship body. A drip receiving tray is connected with a bottom of the groove. An equator edge of the hemispherical secondary screen wall is connected with the ship body at the circular opening of the groove through a skirt support structure. A hatch cover covers a part of the hemispherical secondary screen wall exposed to the ship body. The application improves a deformation capacity of the liquid cargo tank, i.e. an expansion and contraction deformation capacity caused by temperature change, and effectively reduces thermal stress. The inner screen wall structure in the bionic large intestine wall has the effects of reducing a liquid free surface area, slowing down liquid sloshing and improving ship body stability, and enhances safety of the LNG ship liquid cargo tank.

Description

Technical Field

[0001] This invention relates to the field of marine technology, and in particular to an LNG carrier cargo tank based on a large intestine structure. Background Technology

[0002] The continued increase in global demand for liquefied natural gas (LNG) has stimulated demand for LNG carriers. LNG carriers are high-tech, high-value-added vessels whose cargo tanks primarily hold liquefied petroleum gas, which carries inherent risks; therefore, ensuring the safety of these cargo tanks is of paramount importance.

[0003] Liquefied petroleum gas (LPG) requires storage in ultra-low temperatures, typically below -160 degrees Celsius. This results in temperature differences between the inside and outside of the cargo tank often exceeding 200 degrees Celsius. These drastic temperature changes generate significant thermal stress on the main shielding walls of the cargo tank, placing higher demands on the structure's load-bearing capacity. Furthermore, these drastic temperature variations also cause substantial expansion or contraction deformation of the main shielding walls, requiring the structure to possess strong deformation and insulation capabilities. Summary of the Invention

[0004] Purpose of the invention: To address the above-mentioned problems, the purpose of this invention is to provide an LNG carrier cargo tank based on a large intestine structure, which solves the problems of poor deformation capacity and high thermal stress in traditional cargo tanks, thereby improving the safety of LNG carriers.

[0005] Technical Solution: An LNG carrier cargo tank based on a colonic structure includes a spherical main wall, a hemispherical secondary wall, a hatch cover, a skirt support structure, a hull, a drip tray, and a pipe tower. The spherical main wall includes a main wall body and an insulation material layer. The wall surface of the main wall body has a colonic structure, and the outer surface of the main wall body is covered with an insulation material layer. The hemispherical secondary wall covers the upper hemisphere of the spherical main wall. The pipe tower extends vertically from the top of the hemispherical secondary wall to the interior of the spherical main wall. The drip tray is installed in the center of the bottom of the lower hemisphere of the spherical main wall. The spherical main wall is embedded in a groove with a circular opening in the hull. The drip tray is connected to the bottom of the groove. The equatorial edge of the hemispherical secondary wall is connected to the hull through the skirt support structure at the circular opening of the groove. The hatch cover covers the portion of the hemispherical secondary wall exposed on the hull.

[0006] The drip tray provides lower support for the spherical main screen wall. Meanwhile, the hemispherical secondary screen wall is connected to the hull through the skirt support structure, which restricts the spherical main screen wall to the lower part of the hemispherical secondary screen wall. This restricts the position and provides support, allowing the spherical main screen wall to be stably placed between the hemispherical secondary screen wall and the drip tray.

[0007] The groove design prevents the lower hemisphere of the spherical main screen wall from directly contacting the hull, with air between them, thus reducing heat conduction.

[0008] The spherical main shield wall holds liquid cargo. If the liquid cargo leaks, it will first flow through the insulation material layer and into the drip tray below. The pipe tower running through the entire interior of the spherical main shield wall can be used to handle the liquid cargo via pumps.

[0009] Furthermore, multiple protrusions are evenly distributed on both the outer and inner surfaces of the main screen wall, giving the cross-section of the main screen wall a wavy ring structure.

[0010] Ideally, the height of the protrusion on the outer surface of the main screen wall should be greater than the height of the protrusion on its inner surface.

[0011] Ideally, the overall shape of the spherical main screen wall should resemble a peristaltic large intestine, thick in the middle and narrow at both ends.

[0012] When the large intestine is peristaltic, the long, thin intestine will deform. The part of the large intestine that transports food will be filled with food and become thicker in the middle and narrower at both ends. At this time, the shape of the large intestine is similar to that of the main wall.

[0013] Furthermore, the gap between the main screen wall and the insulation material layer is filled with inert gas.

[0014] Furthermore, the inert gas is either nitrogen or carbon dioxide.

[0015] Inert gases serve two purposes: firstly, they prevent direct contact between the main shield wall and the insulation material layer, thus avoiding their expansion, contraction, and deformation; secondly, inert gases are denser than air, providing better insulation and resisting atmospheric pressure. LNG ships typically have inert gas generators that use liquid nitrogen or liquid carbon dioxide vaporization to produce inert gases, therefore this structural feature does not increase the construction cost of the storage tank.

[0016] Furthermore, the main screen wall is made of stainless steel or Invar alloy.

[0017] Furthermore, the material of the hemispherical secondary screen is stainless steel or Invar alloy.

[0018] Ideally, the insulation layer should be made of expanded perlite or polyurethane foam.

[0019] The large intestine, as an internal organ, is mainly used for transporting and digesting food. It is relatively thin and has strong toughness. Under a microscope, the cross-section of the large intestine wall shows an irregular wavy distribution, with numerous protrusions and folds on the surface. It has good expansion, contraction, and deformation capabilities, and can hold a large amount of food residue, which is then transported by intestinal peristalsis.

[0020] This invention utilizes a spherical main shield wall with a structure resembling the wall of an intestinal intestine. The surface of this spherical main shield wall is covered with square protrusions, allowing for relatively independent expansion and contraction deformation. This structure enhances the deformation capacity of the cargo tank, specifically its ability to expand and contract due to temperature changes, thereby effectively reducing thermal stress. The biomimetic inner shield wall structure also reduces the free surface area of ​​the liquid, mitigating sloshing and improving hull stability, significantly enhancing the safety of the LNG carrier's cargo tank. Furthermore, based on the structural characteristics of the spherical main shield wall, filling its outer surface with an inert gas provides thermal insulation and explosion protection. In summary, this cargo tank offers advantages such as low thermal stress, strong deformation capacity, high stability, and high safety performance.

[0021] Beneficial effects: Compared with the prior art, the advantages of the present invention are:

[0022] Based on the structural features of the large intestine wall, this invention proposes a specially shaped spherical main shield wall for LNG carrier cargo tanks. Its main characteristic is that the inner surface of the main shield wall is uniformly covered with numerous square protrusions, resembling the structure of a large intestine, with an irregularly wavy cross-section. This main shield wall possesses excellent expansion and contraction deformation capabilities, effectively reducing thermal stress caused by temperature changes. The biomimetic large intestine structure also reduces the free surface area of ​​the liquid, minimizing liquid sloshing, improving ship stability, and significantly enhancing the safety of LNG carrier cargo tanks.

[0023] Another feature of this invention is that the gap between the insulation material and the main shield wall is filled with an inert gas. This avoids direct contact between the main shield wall and the insulation material, preventing it from expanding, contracting, and deforming. Furthermore, the inert gas has a higher density than air, resulting in better insulation performance and more effective resistance to atmospheric pressure. The inert gas used can be nitrogen or carbon dioxide, etc. LNG ships typically have inert gas generating devices that use the vaporization of liquid nitrogen or liquid carbon dioxide to produce the inert gas. Therefore, this structural feature does not increase the construction cost of the storage tank, but it improves the tank's fire resistance, explosion protection, and insulation capabilities.

[0024] In summary, the liquid cargo tank proposed in this invention has advantages such as low thermal stress, strong deformation capacity, good stability, and high safety performance. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the present invention;

[0026] Figure 2 This is an exploded structural diagram of the present invention;

[0027] Figure 3 This is a structural cross-sectional view of the present invention;

[0028] Figure 4This is a schematic diagram of the main structure of the main screen wall of the present invention, wherein the left diagram is an inner view and the right diagram is an outer view;

[0029] Figure 5 This is an enlarged view of the main structure of the main screen wall of the present invention, wherein the left image is an enlarged view of the inner side and the right image is an enlarged view of the outer side;

[0030] Figure 6 This is a schematic diagram of the cross-section of the main screen wall of the present invention;

[0031] Figure 7 This is a schematic diagram illustrating the principle of reducing thermal stress in this invention;

[0032] Figure 8 This is a schematic diagram of the main screen wall structure dimensions of the present invention. Detailed Implementation

[0033] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0034] An LNG carrier cargo tank based on a colonic structure, such as Figures 1-6 As shown, it includes a spherical main screen wall, a hemispherical secondary screen wall 2, a hatch cover 4, a skirt support structure 5, a hull 6, a drip tray 7, and a pipe tower 8. The spherical main screen wall includes a main screen wall body 1 and a thermal insulation material layer 3.

[0035] The main wall body 1 has a wall structure resembling the wall of the large intestine, with multiple protrusions evenly distributed on both its outer and inner surfaces, giving the cross-section of the main wall body 1 a wavy, annular structure. The outer surface of the main wall body 1 is covered with a heat-insulating material layer 3. The gap between the main wall body 1 and the heat-insulating material layer 3 is filled with an inert gas 9, which is either nitrogen or carbon dioxide. The main wall body 1 is made of stainless steel or Invar alloy, and the heat-insulating material layer 3 is made of expanded perlite or polyurethane foam.

[0036] A hemispherical secondary screen wall 2 covers the upper hemisphere of the spherical primary screen wall. The material of the hemispherical secondary screen wall 2 is stainless steel or Invar alloy. The pipe tower 8 extends vertically from the top of the hemispherical secondary screen wall 2 into the interior of the spherical primary screen wall. The drip tray 7 is installed in the center of the bottom of the lower hemisphere of the spherical primary screen wall. The spherical primary screen wall is embedded in the groove of the circular opening of the hull 6. The drip tray 7 is connected to the bottom of the groove. The equatorial edge of the hemispherical secondary screen wall 2 is connected to the hull 6 through the skirt support structure 5 at the circular opening of the groove. The hatch cover 4 covers the part of the hemispherical secondary screen wall 2 that is exposed on the hull 6.

[0037] like Figure 7As shown in the upper half, the temperature distribution in the upper and lower hemispheres of the LNG carrier's cargo tank is uneven. The conventional main bulkhead of the cargo tank prevents the upper and lower hemispheres from expanding and contracting freely, resulting in thermal stress. Because the upper hemisphere is typically warmer, its rate and extent of thermal expansion and deformation are greater than that of the lower hemisphere. This eventually leads to a significant accumulation of geometric deformation in a certain area between the upper and lower hemispheres, resulting in substantial stress concentration. For example... Figure 7 As shown in the lower half, the main screen wall with a large intestine structure provides a larger deformation margin when the heating is uneven. The cumulative deformation difference between the upper and lower hemispheres is significantly smaller than that of a conventional spherical main screen wall. The protrusions in the large intestine structure can deform freely to a certain extent, thereby reducing the stress concentration factor.

[0038] The main body of the liquid cargo tank wall of this invention has a square protrusion with a biomimetic large intestine structure, the cross-sectional dimensions of which are as follows: Figure 8 As shown. The radius of the spherical cargo tank is R, the radius of the semi-circular outer bulge is r1, and the radius of the semi-circular inner bulge is r2, where R>r1>r2. Assume that the temperature change at the desired point inside the structure is represented by T, where a positive T indicates a temperature increase, and a negative T indicates a decrease. Due to the temperature change, the lengths of the various infinitesimal elements within the structure undergo thermal expansion and contraction under free variation. Assume the change before and after the change is T, and α is the linear expansion coefficient of the specific material. If the material exhibits the same thermal expansion and contraction in all directions, then the linear expansion coefficient is constant. In this case, the deformation at each point inside the structure can be calculated using the following formula:

[0039] ε x =ε y =ε z =αT,γ yz =γ zx =γ xy =0.

[0040] Solving its constitutive relation yields the stress-strain equations in Cartesian coordinates:

[0041]

[0042]

[0043]

[0044] Transforming from a rectangular coordinate system to a polar coordinate system, the stress-strain equation for thermal stress can be expressed by the following formula:

[0045]

[0046]

[0047]

[0048] Where a and b represent the inner and outer diameters of the main screen wall, respectively, and ρ is the polar diameter in polar coordinates. It can be seen from the above formula that the larger the value of ρ, the greater the thermal stress under the same temperature change. This invention is based on the structure of the large intestine, with numerous protrusions in the main screen wall having semi-circular cross-sections. During temperature changes, each protrusion can independently undergo thermal expansion and contraction, thereby minimizing the overall cumulative deformation of the main screen wall. Simultaneously, the biomimetic large intestine structure design reduces the range of ρ values, dividing the large-radius main screen wall into multiple small-radius protrusions (R>r1>r2). This structure can both reduce the magnitude of local structural thermal stress and reduce... Figure 7 The magnitude of cumulative deformation caused by uneven temperature distribution in the upper and lower parts of the liquid cargo tank.

[0049] This invention, based on the structural characteristics of the large intestine, designs the spherical main shield wall of the LNG carrier's cargo tank in the shape of a peristaltic large intestine, that is, "thick in the middle and narrow at both ends." This structural feature effectively reduces the free surface area of ​​the liquid, reduces the impact of liquid sloshing, improves hull stability, and greatly enhances the safety of the LNG carrier's cargo tank. Simultaneously, the main shield wall, designed based on the large intestine wall structure, has numerous square protrusions evenly distributed on its surface, with an irregularly wavy cross-section, possessing extremely strong deformation capacity, i.e., expansion or contraction capacity, which can effectively reduce thermal stress caused by temperature changes. The outer side of the main shield wall is in direct contact with the inert gas, which is beneficial for reducing heat exchange and for explosion protection. In summary, the cargo tank proposed in this invention has advantages such as low thermal stress, strong deformation capacity, good stability, and high safety performance.

Claims

1. An LNG carrier cargo tank based on a colonic structure, characterized in that: The system includes a spherical main shield wall, a hemispherical secondary shield wall (2), a hatch cover (4), a skirt support structure (5), a hull (6), a drip tray (7), and a pipe tower (8). The spherical main shield wall includes a main shield wall body (1) and an insulation material layer (3). The wall surface of the main shield wall body (1) has an intestinal wall structure, and the outer surface of the main shield wall body (1) is covered with an insulation material layer (3). The hemispherical secondary shield wall (2) covers the upper hemisphere of the spherical main shield wall. The pipe tower (8) extends from the hemispherical secondary shield wall. The top of the screen wall (2) extends vertically into the interior of the spherical main screen wall. The drip tray (7) is installed in the center of the bottom of the lower hemisphere of the spherical main screen wall. The spherical main screen wall is embedded in the groove of the circular opening of the hull (6). The drip tray (7) is connected to the bottom of the groove. The equatorial edge of the hemispherical secondary screen wall (2) is connected to the hull (6) through the skirt support structure (5) at the circular opening of the groove. The hatch cover (4) covers the part of the hemispherical secondary screen wall (2) exposed on the hull (6). Multiple protrusions are evenly distributed on the outer and inner surfaces of the main screen wall body (1), making the cross-section of the main screen wall body (1) have a wave-shaped ring structure. The overall shape of the spherical main screen wall is that of a large intestine in motion, thick in the middle and narrow at the top and bottom.

2. The LNG carrier cargo tank based on a colonic structure according to claim 1, characterized in that: The height of the protrusion on the outer surface of the main screen wall (1) is greater than the height of the protrusion on its inner surface.

3. An LNG carrier cargo tank based on a large intestine structure according to claim 1 or 2, characterized in that: The gap between the main screen wall body (1) and the insulation material layer (3) is filled with inert gas (9).

4. The LNG carrier cargo tank based on a colonic structure according to claim 3, characterized in that: The inert gas (9) is nitrogen or carbon dioxide.

5. The LNG carrier cargo tank based on a large intestine structure according to claim 1, characterized in that: The main body of the main screen wall (1) is made of stainless steel or Invar alloy.

6. The LNG carrier cargo tank based on a colonic structure according to claim 1, characterized in that: The material of the hemispherical secondary screen (2) is stainless steel or Invar alloy.

7. The LNG carrier cargo tank based on a large intestine structure according to claim 1, characterized in that: The material of the insulation layer (3) is expanded perlite or polyurethane foam.

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