A method for determining the overall scheme of independent storage tanks for methanol-fueled ships.

Abstract

A method for determining the overall scheme of an independent storage tank for methanol-fueled ships is disclosed. Based on the ship's route, the methanol consumption for one voyage is calculated to determine the required volume of methanol fuel. Multiple N-variable schemes for the independent methanol storage tank are designed. The tank capacity is calculated, and the length, width, and height of the independent methanol storage tank are limited. The tank capacity is compared with the length, width, and height to select a suitable scheme. The 4, 6, and 8-sided structures, which are closest to a circle, are used as the cross-sectional areas of the storage tanks. This approach maximizes the volumetric efficiency and pressure distribution characteristics of circular tanks while possessing the installation flexibility of polygonal structures. It can effectively adapt to the spatial layout requirements of different scenarios, resolving the contradiction between the large volume of methanol fuel and limited installation space. Its structural rationality and application value are significantly superior to other polygonal designs.

Description

Technical Field

[0001] This invention belongs to the field of marine shipbuilding and design, and specifically relates to a method for determining the overall scheme of independent storage tanks for methanol fuel ships. Background Technology

[0002] With the widespread application of clean energy in transportation, industrial power, and other fields, methanol fuel, with its significant environmental advantages and resource availability, is gradually becoming an important alternative to traditional fossil fuels. Methanol fuel has core characteristics such as complete combustion, low pollutant emissions, and wide availability (it can be prepared from various raw materials such as coal, natural gas, and biomass). Furthermore, its physicochemical properties are stable, and its safety during storage and transportation has been verified through long-term practice. The demand for its application in scenarios such as marine power and heavy machinery continues to grow. However, the large-scale application of methanol fuel currently faces technical bottlenecks due to insufficient adaptability of storage and transportation equipment. Among existing fuel storage equipment, C-type tanks, designed for high-pressure gaseous fuels or high-density liquid fuels, are frequently used for methanol fuel storage. However, the manufacture of C-type tanks requires special materials and high-precision molding processes, resulting in high raw material costs, long processing cycles, and high production difficulty, significantly increasing the application cost of methanol fuel and limiting its market promotion efficiency. In fact, the working pressure and physical properties of methanol fuel determine that its storage does not rely on the high-strength structure of C-type tanks. Conventional structural welding methods can meet the mechanical requirements for safe storage and use. The current technology blindly adopts the design scheme of C-type tanks, which has obvious cost redundancy and design irrationality.

[0003] Meanwhile, methanol fuel has a significantly lower density than traditional liquid fuels (methanol density is approximately 0.79 g / cm³, far lower than diesel and gasoline). Therefore, the same mass of methanol fuel requires a larger storage volume, placing higher demands on the space utilization and structural rationality of fuel tanks. While a circular structure is the optimal form for liquid storage tanks (it can evenly distribute internal pressure and maximize volume utilization), purely circular tanks suffer from poor spatial adaptability and difficulty in coordinating with surrounding components during actual installation. Therefore, a polygonal design that combines the advantages of a circular structure with practical installation becomes the preferred choice. Among these, 4, 6, and 8-sided structures, being closest to a circular shape, can retain the volumetric efficiency and pressure distribution characteristics of a circular tank to the greatest extent while possessing the installation flexibility of a polygonal structure. This effectively adapts to the spatial layout requirements of different scenarios, resolving the contradiction between the large volume of methanol fuel and limited installation space. Their structural rationality and application value are significantly superior to other polygonal designs.

[0004] In summary, existing methanol fuel storage equipment suffers from technical defects such as excessive cost and mismatch between structural design and methanol fuel characteristics. There is an urgent need for a storage tank design scheme that is adapted to the physicochemical characteristics of methanol fuel, has controllable cost, and has a reasonable structure, in order to promote the large-scale and low-cost application of methanol fuel. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a method for determining the overall scheme of independent storage tanks for methanol-fueled ships. The aim is to maximize the preservation of the volumetric efficiency and pressure dispersion characteristics of circular tanks, effectively adapt to the spatial layout requirements of different scenarios, and solve the problem of large methanol fuel volume and limited installation space. The technical solution adopted is as follows: A method for determining the overall scheme of independent storage tanks for methanol-fueled ships, the specific process of which is as follows: Step 1: Determine the capacity C of the independent methanol storage tank based on the flight route. C={(Ms / Vs / d+ns)·(P1 +P2)+P3} / (ρ·Rs).

[0006] Ms represents the distance traveled by the operating vessel.

[0007] Vs represents the design speed of the operating vessel.

[0008] d is 24 hours.

[0009] P1 represents the daily methanol consumption of the generator.

[0010] P2 represents the daily methanol consumption of the main unit.

[0011] P3 represents the total methanol consumption of the boiler.

[0012] ns represents the reserve of sailing days for operating vessels.

[0013] ρ is the density of methanol.

[0014] Rs represents the fuel fill percentage, which, according to IGF, is 95% - 2% = 93% for low flash point fuel.

[0015] Step 2: The length of the independent methanol storage tank is Lg, the width is Bg, and the overall height is Dg. Lg is less than 0.7 times the length of the cargo hold where the independent methanol storage tank is located, and the width of Bg is less than 0.3 times the width of the ship where the independent methanol storage tank is located.

[0016] Dg = Tg + base height, where Tg is the height of the methanol independent storage tank.

[0017] Step 3: Define six N-gon schemes: Scheme 1 - cylinder, Scheme 2 - square, Scheme 3 - inverted trapezoid, Scheme 4 - regular hexagon, Scheme 5 - non-regular hexagon, and Scheme 6 - octagon. For Schemes 3 through 6, the following conditions must be met: 0.4Bg≤M1≤Bg, 45°≤A1≤90°, M4=sin(A1)·M2.

[0018] Option 3: Inverted trapezoid: N=4, M3=0, M5=0, A2=0, M1>0.6Bg.

[0019] Option 4: Regular hexagon: N=6, M5=0, M1=M2=M3, A1=A2=60°.

[0020] Option 5: Non-regular hexagon: N=6, M3=0, A2=0.

[0021] Scheme 6: Octagonal: N=8, 0.45Tg≤M5≤Tg, 0≤M3≤M4.

[0022] Where M1 is the length of the bottom edge of the independent methanol storage tank, M2 is the length of the bottom slope, M3 is the length of the top slope, M4 is the distance from the bottom edge to the sidewall, and M5 is the sidewall length. A1 is the angle formed by the bottom edge and the bottom slope of the independent methanol storage tank. A2 is the angle formed by the top slope and the sidewall. Based on the density of the bulkhead material of the methanol independent storage tank and the density of the internal liquid cargo, the load distribution characteristics along the length of the methanol independent storage tank are determined: The central part of the polygonal storage tank has an N-sided cross-section. The uniformly distributed load P in schemes three and four is calculated using the following formulas: Ac=Tg·Bg-M4 2 arctan(A1)-0.5·M3 2 ·sin(A2)·cos(A2).

[0023] Gg=ρm ·{M1·t1+2·M2·t2+2·M3·t3+2·t5·M5 +(Bg-2·M3·sin(A2))·t6+n·Astii}.

[0024] P = Ac·ρc + Gg.

[0025] In the formula, t1, t2, t3, t5, and t6 are the wall thicknesses of the cylinder.

[0026] c represents the density of the liquid cargo in the storage tank.

[0027] m is the density of the storage tank container material.

[0028] Astii stiffener cross-sectional area.

[0029] n represents the number of reinforcing ribs.

[0030] Ac represents the cross-sectional area of ​​the storage tank.

[0031] ρc is the density of the liquid cargo in the storage tank.

[0032] ρm is the density of the storage tank container material.

[0033] Gg represents the weight per meter of the cargo tank.

[0034] Step 4: Determine saddle arrangement and strong frame design Two saddles are arranged along the length direction of the polygonal cargo tank, the two saddles are arranged centrosymmetrically along the lower side of the tank body, and the distance from the saddle to the end of the polygon is one strong frame spacing.

[0035] Step 5: Determine the N-sided cargo tank scheme Rc is the cargo capacity restriction coefficient, and Rm is the process restriction coefficient.

[0036] Rc=1.1C / (Lg·Bg·Tg).

[0037] When Rc>Rs, cargo capacity becomes the limiting condition, and Scheme 6 is preferred.

[0038] When Rc=Rs, cargo capacity and process are equally balanced, and Schemes 4 and 5 are preferred.

[0039] When Rc<Rs, process becomes the limiting condition, and Scheme 5 is preferred.

[0040] When Rc is much smaller than Rs, process becomes the limiting condition, and Scheme 3 is preferred.

[0041] In the above method for determining the overall scheme of the independent cargo tank of a methanol-fueled ship, further, in step 2, the cross-sectional area of the independent methanol cargo tank Sg=C / Lg.

[0042] In the above method for determining the overall scheme of the independent cargo tank of a methanol-fueled ship, further, in step 2, Tg is selected according to the blind area, and Dg does not exceed the upper limit height of the connecting line between the highest point of the ship's superstructure at the corresponding position and the farthest end of the ship's bow.

[0043] In the above method for determining the overall scheme of the independent cargo tank of a methanol-fueled ship, further, in step 2, the ratio of Bg to Tg is between 0.8 and 1.2.

[0044] In the above method for determining the overall scheme of the independent cargo tank of a methanol-fueled ship, further, for Scheme 1 (cylindrical shape), Rm=0.9~1; For Scheme 2 (square shape), Rm=0~0.65; For Scheme 3 (inverted trapezoid shape), Rm=0.65~0.7; For Scheme 4 (regular hexagon shape), Rm=0.75~0.8; For Scheme 5 (irregular hexagon shape), Rm=0.7~0.75; For Scheme 6 (octagon shape), Rm=0.8~0.9.

[0045] Furthermore, in the above-mentioned method for determining the overall scheme of independent storage tanks for methanol-fueled ships, the independent methanol storage tanks are located vertically on the main deck and longitudinally in the middle of the cargo oil tanks, with one independent methanol storage tank on each of the port and starboard sides.

[0046] This invention calculates the methanol consumption for a single voyage based on the ship's route, thus determining the required volume of methanol fuel. An N-sided polygon, the closest to a circle, is chosen as the tank's cross-sectional area. This design maximizes the volumetric efficiency and pressure distribution characteristics of a circular tank while offering the installation flexibility of a polygonal structure. It effectively adapts to the spatial layout requirements of different scenarios, resolving the contradiction between the large volume of methanol fuel and limited installation space. Its structural rationality and application value are significantly superior to other polygonal designs.

[0047] The independent storage tanks are located vertically on the main deck and longitudinally between the cargo oil tanks, one on each side. The advantage of this independent tank design is that it does not occupy cargo oil tank capacity and requires fewer modifications compared to conventional designs. Therefore, it is more suitable for designs that only require methanol readiness, resulting in less increase in empty ship weight. The independent tank design needs to consider structural alignment, longitudinal bending moment, blind spots in the wheelhouse, and limitations imposed by deck-mounted outfitting equipment and access routes. When the methanol fuel storage tank is longitudinally located precisely in the center of the cargo oil tanks, the requirements are generally met. Attached Figure Description

[0048] Figure 1 This is a blind spot view diagram.

[0049] Figure 2 This is a schematic diagram of the cross-sectional area of ​​a polygonal storage tank.

[0050] Figure 3 It is a side view of a polygonal storage tank and a saddle arrangement scheme.

[0051] Figure 4 yes Figure 3 A schematic diagram of a typical cross-section A.

[0052] Figure 5 yes Figure 3 A schematic diagram of a typical cross-section C.

[0053] Figure 6 yes Figure 3 Schematic diagrams of typical cross-sections B and D. Detailed Implementation

[0054] The invention will be further described with reference to the accompanying drawings.

[0055] A method for determining the overall design of independent storage tanks for methanol-fueled ships is presented. Since methanol fuel is stored under normal temperature and pressure, cryogenic tanks are not required. In existing technologies, most independent deck tanks are Type C tanks, which have long ordering cycles and cost 20 times more than custom-made tanks made of ordinary steel plates. Cryogenic Type C tanks for methanol fuel are expensive and uneconomical. For self-made tanks, there are typically six options: Option 1: cylindrical; Option 2: square; Option 3: inverted trapezoidal; Option 4: regular hexagonal; Option 5: non-regular hexagonal; and Option 6: octagonal. The difficulty of plate processing, welding, cutting, and precision control is shown in the table below.

[0056]

[0057] Therefore, N-sided methanol fuel storage tanks are the most suitable alternative to circular storage tanks.

[0058] Option 1 (cylindrical) and Option 2 (square) have obvious flaws and will no longer be considered.

[0059] Step 1: Calculate the tank capacity C based on the route.

[0060] C={(Ms / Vs / d+ns)·(P1 +P2)+P3} / (ρ·Rs); Ms represents the distance traveled by the operating vessel; Vs is the design speed of the operating vessel; d is 24 hours; P1 represents the daily methanol consumption of the generator; P2 represents the daily methanol consumption of the main unit; P3 represents the total methanol consumption of the boiler; ns represents the reserve of sailing days for operating vessels; ρ is the density of methanol; Rs represents the fuel fill percentage, which, according to IGF, is 95% - 2% = 93% for low flash point fuel. Step 2: Confirm the dimensions of the independent tank: Lg for width, Bg for width, and Dg for height.

[0061] The length of the independent tank is Lg, the width is Bg, and the height is Tg. Lg is less than 0.7 times the length of the cargo hold where the independent tank is placed, Bg is less than 0.3 times the width of the ship at the location where the deck tank is placed, and Tg is selected based on the blind spot. Dg = Tg + base height, and cannot exceed the upper limit of the line connecting the highest point of the ship's superstructure to the farthest point of the bow at the location. Figure 1 As shown.

[0062] The cross-sectional area of ​​an independent tank is Sg = C / Lg. The ratio of width Bg to height Tg is between 0.8 and 1.2.

[0063] Step 3: Based on the density of the tank bulkhead material and the density of the internal liquid cargo, determine the load distribution characteristics along the length of the tank (e.g., ...). Figure 2 As shown): Six N-gon designs are defined: Design 1 - cylinder; Design 2 - square; Design 3 - inverted trapezoid; Design 4 - regular hexagon; Design 5 - non-regular hexagon; and Design 6 - octagon. Designs 3 through 6 must satisfy the following conditions: 0.4Bg≤M1≤Bg, 45°≤A1≤90°, M4=sin(A1)·M2.

[0064] Option 3: Inverted trapezoid: N=4, M3=0, M5=0, A2=0, M1>0.6Bg.

[0065] Option 4: Regular hexagon: N=6, M5=0, M1=M2=M3, A1=A2=60°.

[0066] Option 5: Non-regular hexagon: N=6, M3=0, A2=0.

[0067] Scheme 6: Octagonal: N=8, 0.45Tg≤M5≤Tg, 0≤M3≤M4.

[0068] Where M1 is the length of the bottom edge of the independent methanol storage tank, M2 is the length of the bottom slope, M3 is the length of the top slope, M4 is the distance from the bottom edge to the sidewall, and M5 is the sidewall length. A1 is the angle formed by the bottom edge and the bottom slope of the independent methanol storage tank. A2 is the angle formed by the top slope and the sidewall.

[0069] The central part of the polygonal storage tank has an N-sided cross-section, and the formula for calculating the uniformly distributed load P is as follows: Ac=Tg·Bg-M4 2 arctan(A1)-0.5·M3 2 ·sin(A2)·cos(A2).

[0070] Gg=ρm ·{M1·t1+2·M2·t2+2·M3·t3+2·t5·M5 +(Bg-2·M3·sin(A2))·t6+n·Astii}.

[0071] P = Ac·ρc + Gg.

[0072] In the formula, t1, t2, t3, t5, and t6 are the wall thicknesses of the cylinder.

[0073] c represents the density of the liquid cargo in the storage tank.

[0074] m is the density of the storage tank container material.

[0075] Astii stiffener cross-sectional area.

[0076] Number of stiffeners.

[0077] Ac is the cross-sectional area of the cargo tank.

[0078] ρc is the density of the liquid cargo in the cargo tank.

[0079] ρm is the density of the material of the cargo tank container.

[0080] Gg is the weight per meter of the cargo tank.

[0081] Step 4: Determine saddle arrangement and strong frame design based on load distribution characteristics Two saddles are arranged along the length direction of the polygonal cargo tank, the two saddles are arranged symmetrically along the center at the lower side of the tank body, and the distance from the saddle to the end of the polygon is one strong frame spacing; Section B is the sliding end (dashed line), and Section D is the fixed end (solid line). A, B, C, D are typical sections corresponding to different positions, as Figure 3 shown.

[0082] as Figure 4 , 5 and 6 show, taking the octagonal scheme as an example, the ABCD sections are展示.

[0083] Section A is a watertight bulkhead, with the stiffener direction facing the interior of the liquid tank; Sections B and D have the same structure, and annular stiffeners are arranged inside, the height of the stiffener is F, 500mm<F<1500mm. Section B corresponds to a sliding support, which is lapped with the structure, and Section D corresponds to a fixed base, which is welded to the structure. Section C is a swash bulkhead, arranged to avoid excessive sloshing inside the liquid tank.

[0084] Step 5: Determine the N-sided polygonal cargo tank scheme.

[0085] Cargo capacity limiting coefficient Rc, process limiting coefficient Rm.

[0086] Rc=1.1C / (Lg·Bg·Tg).

[0087] Scheme 1 (cylindrical): Rm=0.9~1; Scheme 2 (square): Rm=0~0.65; Scheme 3 (inverted trapezoidal): Rm=0.65~0.7; Scheme 4 (regular hexagonal): Rm=0.75~0.8; Scheme 5 (irregular hexagonal): Rm=0.7~0.75; Scheme 6 (octagonal): Rm=0.8~0.9.

[0088] When Rc>Rs, cargo capacity becomes the limiting condition, and Scheme 6 is preferred.

[0089] When Rc=Rs, cargo capacity and process are equally balanced, and Schemes 4 and 5 are preferred.

[0090] When Rc<Rs, the process becomes a limiting condition, and Option 5 is preferred.

[0091] When Rc is much smaller than Rs, the process becomes a limiting condition, and Option 3 is preferred.

[0092] Cargo capacity limiting coefficient Rc, 0<Rc<1. The larger Rc is, the more likely cargo capacity becomes a limiting condition.

[0093] Process limiting coefficient Rs, 0<Rs<1. The larger Rs is, the more likely the process becomes a limiting condition.

[0094] Take a ship as an example: Voyage → Speed → Reserve → Methanol consumption of main engine → Methanol consumption of generator → Methanol consumption of boiler → Ignition oil → Availability → Methanol fuel tank capacity.

[0095] 6000n. mile → 15kn → 3 days → 125.3t / day → 13.3t / day → 350t → 180t → 93% → 7329m 3 .

[0096] C=((6000 / 15 / 24+3 )(13.3+125.3)+350 ) / (0.79·93%)=4186m 3 .

[0097] Lg=30m, Bg=22m, Tg=8m.

[0098] Rc=1.1·4186 / (30·22·8)=0.87, and the octagonal scheme is selected.

Claims

1. A method for determining the overall scheme of independent storage tanks for methanol-fueled ships, characterized in that, The specific process is as follows: Step 1: Determine the capacity C of the independent methanol storage tank based on the flight route. C={(Ms / Vs / d+ns)·(P1 +P2)+P3} / (ρ·Rs); Ms represents the distance traveled by the operating vessel; Vs is the design speed of the operating vessel; d is 24 hours; P1 represents the daily methanol consumption of the generator; P2 represents the daily methanol consumption of the main unit; P3 represents the total methanol consumption of the boiler; ns represents the reserve of sailing days for operating vessels; ρ is the density of methanol; Rs represents the fuel fill level; Step 2: The length of the independent methanol storage tank is Lg, the width is Bg, and the overall height is Dg. Lg is less than 0.7 times the length of the cargo hold where the independent methanol storage tank is located, and the width of Bg is less than 0.3 times the width of the ship where the independent methanol storage tank is located. Dg = Tg + base height, where Tg is the height of the methanol independent storage tank; Step 3: Define six N-gon schemes: Scheme 1 - cylinder, Scheme 2 - square, Scheme 3 - inverted trapezoid, Scheme 4 - regular hexagon, Scheme 5 - non-regular hexagon, and Scheme 6 - octagon. For Schemes 3 through 6, the following conditions must be met: 0.4Bg≤M1≤Bg, 45°≤A1≤90°, M4=sin(A1)·M2; Option 3: Inverted trapezoid: N=4, M3=0, M5=0, A2=0, M1>0.6Bg; Option 4: Regular hexagon: N=6, M5=0, M1=M2=M3, A1=A2=60°; Option 5: Non-regular hexagon: N=6, M3=0, A2=0; Scheme: Hexagonal shape: N=8, 0.45Tg≤M5≤Tg, 0≤M3≤M4; Where M1 is the length of the bottom edge of the independent methanol storage tank, M2 is the length of the bottom slope, M3 is the length of the top slope, M4 is the distance from the bottom edge to the sidewall, and M5 is the sidewall length; A1 is the angle formed by the bottom edge and the bottom slope of the independent methanol storage tank; A2 is the angle formed by the top slope and the sidewall. Based on the density of the bulkhead material of the methanol independent storage tank and the density of the internal liquid cargo, the load distribution characteristics along the length of the methanol independent storage tank are determined: The central part of the polygonal storage tank has an N-sided cross-section. The uniformly distributed load P in schemes three and four is calculated using the following formulas: Ac=Tg·Bg-M4 2 ·arctan(A1)-0.5·M3 2 ·sin(A2)·cos(A2); Gg=ρm ·{M1·t1+2·M2·t2+2·M3·t3+2·t5·M5 +(Bg-2·M3·sin(A2))·t6+n·Astii}; P = Ac·ρc + Gg; In the formula, t1, t2, t3, t5, t6 are the wall thicknesses of the cylinder; c represents the density of the liquid cargo in the storage tank; m is the density of the storage container material; Astii stiffener cross-sectional area; n is the number of reinforcing ribs; Ac is the cross-sectional area of ​​the storage tank; ρc is the density of the liquid cargo in the storage tank; ρm is the density of the storage tank container material; Gg is the weight per meter of the storage tank; Step 4: Determine the saddle layout and rigid frame design The polygonal storage tank has two saddles along its length. The two saddles are symmetrically arranged along the center on the lower side of the tank. The distance between the saddle and the end of the polygon is one strong frame spacing. Step 5: Determining the N-sided storage tank design Cabin capacity limitation factor Rc, process limitation factor Rm; Rc=1.1C / (Lg·Bg·Tg); When Rc>Rs, cargo tank capacity becomes a limiting condition, and Scheme 6 is preferred; When Rc=Rs, cargo tank capacity and process are equal, and Schemes 4 and 5 are preferred; When Rc<Rs, process becomes a limiting condition, and Scheme 5 is preferred; When Rc is much smaller than Rs, process becomes a limiting condition, and Scheme 3 is preferred.

2. The method for determining the overall scheme of independent storage tanks for methanol-fueled ships according to claim 1, characterized in that, Rs= according to IGF, the filling rate of low-flashpoint fuel is 95%-2%=93%.

3. The method for determining the overall scheme of independent storage tanks for methanol-fueled ships according to claim 1, characterized in that, In step 2, the cross-sectional area Sg of independent methanol storage tank is C / Lg.

4. The method for determining the overall scheme of independent storage tanks for methanol-fueled ships according to claim 1, characterized in that, In step 2, Tg is selected according to the blind area, and Dg does not exceed the upper limit height of the connecting line between the highest point of the ship's superstructure at the corresponding position and the farthest end of the bow of the ship.

5. The method for determining the overall scheme of independent storage tanks for methanol-fueled ships according to claim 1, characterized in that, In step 2, the ratio of Bg to Tg is between 0.8 and 1.

2.

6. The method for determining the overall scheme of independent storage tanks for methanol-fueled ships according to claim 1, characterized in that, In step 5, for Scheme 1 with cylindrical shape, Rm=0.9~1; For Scheme 2 with square shape, Rm=0~0.65; For Scheme 3 with inverted trapezoidal shape, Rm=0.65~0.7; For Scheme 4 with regular hexagonal shape, Rm=0.75~0.8; For Scheme 5 with irregular hexagonal shape, Rm=0.7~0.75; For Scheme 6 with octagonal shape, Rm=0.8~0.

9.

7. The method for determining the overall scheme of independent storage tanks for methanol-fueled ships according to claim 1, characterized in that, The independent methanol storage tanks are vertically arranged on the main deck and longitudinally arranged at the middle position of the cargo oil tanks, and one independent methanol storage tank is arranged on each of the port and starboard sides.

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