Method for determining overall scheme of C-shaped independent storage tank

Abstract

A method for determining an overall scheme of a C-shaped independent storage cabin comprises the steps of firstly determining load distribution characteristics of the storage cabin in the length direction according to the cabin wall material density and the internal liquid cargo density of the storage cabin, determining a saddle arrangement position calculation scheme based on the load distribution characteristics, and then calculating the overall scheme of the C-shaped independent storage cabin according to ship size characteristics and storage cabin structure stress characteristics. The storage tank radius, the storage tank length and the optimal interval of the saddle arrangement position are preliminarily determined, then the saddle arrangement position, the storage tank length and the storage tank radius are optimized, the evaporation rates of the liquid cargo tank under different schemes are calculated, and a final design scheme is determined. According to the method, the radius, the length and the saddle arrangement position of the C-shaped storage tank can be quickly determined on the basis of the target tank capacity requirement and the basic limiting conditions of the target ship, and a storage tank overall scheme considering structural safety and economical efficiency is obtained.

Description

Technical Field

[0001] The invention belongs to the field of construction and design of marine LNG storage tanks, and in particular relates to a method for determining an overall scheme of a C-type independent storage tank. Background Art

[0002] Affected by international carbon emission restrictions, gas tankers and dual-fuel ships have become popular ship types at present. As a key equipment for liquefied gas tankers and dual-fuel ships, the overall design scheme of C-type tanks must take into account two key factors: safety and economy. When designing C-type tanks, it is necessary to consider the characteristics of the hull structure layout, taking into account structural optimization, reducing heat penetration, and reducing the LNG evaporation rate. At present, gas tankers with multi-size and multi-tank capacity requirements worldwide are in a critical period of ship type development, and there may be multiple different overall design schemes for liquid cargo tanks for the same cargo hold volume requirement. How to achieve fast and efficient design scheme determination among many feasible technical solutions under the background of different ship type requirements is an urgent problem to be solved in response to the current boom in the research and development of liquefied gas ships.

[0003] The present invention provides a standardized method for determining the overall design scheme of a C-type storage tank. Based on the target tank capacity requirements and the basic constraints of the target ship, the radius, length and saddle position of the C-type storage tank can be quickly determined, and an overall storage tank scheme that takes into account both structural safety and economy can be obtained. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for determining the overall scheme of a C-type independent storage tank, aiming to achieve the purpose of quickly determining the structural dimensions of each C-type storage tank based on the target tank capacity requirements and the basic constraints of the target ship. The technical scheme adopted is:

[0005] A method for determining the overall scheme of a C-type independent storage tank, a method for determining the overall scheme of a C-type independent storage tank, characterized in that the C-type storage tank is composed of a straight tube section in the middle and head sections at both ends, the straight tube section is a cylindrical structure with a circular cross section, the head section is in a spherical bowl shape, the two ends of the straight tube section and the head section are butt-jointed and welded into one, and two saddles are symmetrically arranged at the bottom of the straight tube section. The overall determination method of the C-type storage tank is as follows:

[0006] S1: According to the density of the tank bulkhead material and the density of the internal liquid cargo, determine the load distribution characteristics of the tank along the length direction, and calculate the load distribution of the straight section and the load distribution of the head section respectively.

[0007] The length of the straight section is L, and the straight section has a uniformly distributed load q L The calculation formula is as follows:

[0008]

[0009] In the formula,

[0010] t is the average wall thickness of the cylinder, and the initial value is calculated by the following formula. For LNG tanks, t is not less than 0.02m. For CO2 tanks, t is not less than 0.05m.

[0011]

[0012] R i The inner radius of the C-type tank can be obtained from the initial design drawings.

[0013] ρ c It is the density of liquid cargo in type C tank, which is determined according to the type of liquid cargo to be loaded in the tank.

[0014] ρ m It is the material density of type C tank container, which is determined according to the type of material selected for the tank bulkhead.

[0015] R is the average value of the inner and outer radius of the straight tube section, R = R i +t / 2.

[0016] P0 is the design pressure of the tank.

[0017] σ m is the allowable stress corresponding to the tank material.

[0018] The length of the head section is H, and the total load of the head section is Q H It can be calculated by the following formula:

[0019]

[0020] The head section is equivalent to a straight tube section with the same diameter as the straight tube section, and the uniformly distributed load is q L , then the equivalent length L0 of the head section length H is calculated as follows:

[0021]

[0022] S2: Determine the saddle setting position based on the load distribution characteristics.

[0023] S2.1: First, select two saddles at any position and set them symmetrically. Calculate the support reaction force of the saddle at this time. The distance between the saddle and the end of the straight tube section is A. According to the load distribution of the head section and the straight tube section, the support reaction force Q at the saddle is calculated as:

[0024]

[0025] S2.2: Secondly, calculate the bending moment at the saddle and the mid-span of the tank. Combined with the load distribution along the length of the tank in S1 and the support reaction at the saddle in step S2.1, the bending moment at the saddle is calculated as:

[0026]

[0027] The bending moment at the mid-span of the tank is:

[0028]

[0029] S2.3: The final calculation of the saddle position for the tank size shows that the bending moment at the mid-span of the tank is equal to the bending moment at the saddle according to static equilibrium:

[0030] |M a |=|M b |

[0031] That is:

[0032]

[0033] The distance A between the saddle and the end of the straight section is calculated as follows:

[0034]

[0035] Further calculation is performed to obtain the distance X between the two saddles:

[0036]

[0037] S3: Based on the ship size characteristics and the stress characteristics of the tank structure, preliminarily determine the optimal range of the tank radius, tank length and saddle location.

[0038] S3.1 Determine the constraints for optimizing the tank size.

[0039] The constraints for tank size optimization include those provided by the ship layout, such as ship width, tank length, cabin height, blind area, deck equipment layout, and the constraints provided by the force angle of the tank structure.

[0040] 1) The constraints provided by the ship type layout need to be determined at the initial stage of determining the overall layout plan of the storage tanks based on the actual ship design characteristics.

[0041] If the above-mentioned storage tank is arranged in the cargo hold area under the hull deck, it must meet the following requirements:

[0042] - The range of tank diameter determined by the ship's tank length: the tank outer diameter in the length direction is not less than 700mm from the structural member at the transverse bulkhead.

[0043] - Tank diameter range determined by ship width: the outer diameter of the tank is not less than 700mm from the nearby hull structure in the ship width direction.

[0044] - The range of tank diameter determined by the height of the ship's cabin: the minimum distance of the tank's outer diameter from the bottom hull continuous longitudinal member in the height direction is not less than 920mm, and the minimum distance from the top hull strong transverse beam panel in the height direction is not less than half the width of the strong transverse beam panel.

[0045] If the storage tank is arranged above the hull deck, the storage tank layout position must be considered based on the existing ship deck equipment and must not affect the ship's blind area.

[0046] 2) Considering the structural stress characteristics of the tank, the tank length-to-diameter ratio γ of the C-type tank arranged above the deck is usually limited. The preferred range of γ is 3 to 6. γ is calculated by the following formula:

[0047]

[0048] That is, the length of the straight section L and R i The functional relationship between them.

[0049] L=2γR i

[0050] S3.2: Based on the tank size constraints, obtain the tank inner radius R i and the optimal interval of the length L of the tank straight section, and further determine the saddle setting position.

[0051] 1) Calculate the internal radius R of the tank i Optimized interval and straight section length L:

[0052] According to the target tank capacity demand V, the relationship between the tank capacity and the tank size can be expressed as:

[0053]

[0054] According to the expression of aspect ratio γ, the relationship between aspect ratio γ and target tank capacity V is calculated:

[0055]

[0056] Then get

[0057]

[0058] According to S3.1, the preferred range of the aspect ratio γ is 3 to 6, and the tank inner diameter R is obtained. i The preferred interval of: R imin ~R imax ,in

[0059]

[0060] 2) Calculate the length L of the straight section of the tank:

[0061] According to the expression of target tank capacity V, the length L of the tank straight section can be expressed as:

[0062]

[0063]

[0064] That is, according to R i , V calculates the corresponding L value and its optimal interval L min ~L max .

[0065] 3) Calculate the wall thickness t of the tank straight section according to the formula in S1, and obtain the optimal interval L of the equivalent length L0 of the head section 0min ~L 0max .

[0066] 4) Then, the distance A from the end of the saddle to the straight section and the optimal interval A can be calculated according to formula S2.3: min ~A max , the distance between the two saddles X and the optimal interval X min ~X max .

[0067] S4: According to the arrangement of the hull strong support structure, determine the feasible arrangement of the tank saddle. According to the feasible arrangement of the saddle and the load distribution characteristics of the tank obtained in S2, the optimization design of the tank length and tank radius is carried out to obtain multiple solutions.

[0068] The hull strong support structure arrangement scheme is obtained from the hull design drawings, and refers to the arrangement position of the hull transverse strong frame structure.

[0069] The storage tank saddle should be arranged at the same position as the strong support structure of the hull, so as to make full use of the structural features of the hull and reduce the additional structural reinforcement design brought by the storage tank.

[0070] 1) Based on the optimal interval X of the distance between the two saddles of the tank min ~X max And the span of the hull frame support structure X S , and the feasible tank saddle distance and feasible setting scheme are calculated.

[0071] In the feasible saddle arrangement scheme, the tank saddle distance is calculated by the following formula:

[0072] X=n×X S

[0073] n is the number of spans of the hull frame.

[0074] 2) According to the determined tank saddle distance X, combined with the tank distribution characteristics in step S2, the corresponding A, L0, and L are calculated in sequence.

[0075] 3) According to the relevant formula in step S3.2, calculate the corresponding tank inner diameter R i .

[0076] S5: Calculate the evaporation rate of the liquid cargo tank under each scheme in S4 and determine the final design scheme.

[0077] S5.1: Calculate the heat flux density q at different insulation materials of the tank wall.

[0078]

[0079] In the formula,

[0080] T1, T2 are the inner and outer surface temperatures of the cylinder wall, in K.

[0081] λ is the thermal conductivity of the material, which is determined by the specific material parameters.

[0082] R o is the outer radius of the tank, R o =R i +t.

[0083] S5.2 Calculation of cargo tank evaporation rate

[0084] A simplified method is used to calculate the evaporation rate (BOR) of liquid cargo tanks. The evaporation rate (BOR) of liquid cargo tanks can be calculated using the following formula:

[0085]

[0086] In the formula,

[0087] Q is the total heat entering the cargo tank, Q = ∑q × S, which is the sum of the product of the heat flux density q of different materials in different areas on the outer surface of the tank and the corresponding area S.

[0088] r is the latent heat of vaporization of the liquid cargo in the storage tank, which is a parameter that matches the liquid cargo.

[0089] The calculated evaporation rates of the cargo tanks of various schemes are compared and the final optimal scheme is selected, that is, the scheme with the smallest evaporation rate of the cargo tanks.

[0090] The above-mentioned method for determining the overall scheme of a C-type independent tank, further, the saddle setting position A should make the stress of the C-type tank uniform, and each stress does not exceed the allowable stress of the material, so as to improve the safety of the C-type tank structure design. At the same time, the saddle position should be consistent with the position of the hull structure strong frame, so as to make full use of the hull structure characteristics and reduce the impact of the installation of the tank.

[0091] The beneficial effects of the invention are:

[0092] 1. The key parameters of the C-type tank length and tank radius are determined and considered in a coordinated manner with the saddle layout position, so that the saddle layout position fully meets the stress characteristics of the tank structure, avoids additional bending moment loads in the length direction of the tank, makes the tank stress uniform, and lays the foundation for the optimal design of the tank.

[0093] 2. For large marine pressure vessel tanks, the tank aspect ratio is used as a limiting condition for the optimization design of tank length and tank radius, which can reduce the storage and transportation costs while meeting the large volume requirements. At the same time, it avoids the tank strength risk caused by unconventional design and improves the safety of tank structure design.

[0094] 3. During the tank design process, the main parameters of the hull, such as ship width, tank length and tank depth, are used as key parameter constraints of the tank, making the tank-ship design interface more user-friendly and avoiding major adjustments to the entire ship design plan due to the optimization of a single element of the tank.

[0095] 4. The layout of the storage tank saddle fully considers the layout characteristics of the hull support structure, and the saddle position is kept consistent with the position of the hull structure strong frame, which can fully utilize the hull structure characteristics and reduce the impact of adding storage tanks.

[0096] 5. For the preliminary design, the hull strong frame layout can be adjusted according to the optimized design parameters of the storage tank to avoid adding strong structures at the storage tank saddle, which will lead to structural design redundancy. In the case where the installation of storage tanks has a greater impact on the overall performance of the hull, adjustment targets can be proposed according to the actual ship's needs to adjust the parameter range of the storage tank design, thereby optimizing the storage tank design and avoiding a significant impact on the actual ship.

[0097] 6. Based on the design process of the present invention, it can be applied to both the fuel tank installed on the deck and the liquid cargo tank located under the deck, and can realize rapid determination of storage tank solutions for different tank capacity solutions and different ship types, thereby improving efficiency and ensuring the feasibility of the solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0098] Figure 1 It is a schematic diagram of the C-type tank structure;

[0099] Figure 2 This is a schematic diagram of the C-type tank head section being equivalent to a straight cylinder section;

[0100] Figure 3 It is a schematic diagram of load distribution in a C-type tank;

[0101] Figure 4 This is a schematic diagram of the limitation of the inner diameter of the tank by the blind area of ​​the ship;

[0102] Figure 5 It is a schematic diagram of the radius and length ratio of the C-type tank;

[0103] Figure 6 It is a schematic diagram of the spacing limit of the saddle arrangement of the tank tank;

[0104] Figure 7 It is a tank saddle arrangement scheme that takes into account the strong frame arrangement characteristics of the hull. DETAILED DESCRIPTION

[0105] The present invention will be further described in conjunction with the accompanying drawings.

[0106] A method for determining the overall scheme of a C-type independent storage tank, such as Figure 1 As shown, the C-type tank is composed of a straight section in the middle and head sections at both ends. The straight section is a cylindrical structure with a circular cross section, and the head section is in a bowl shape. The two ends of the straight section and the head section are butt-jointed and welded together. Two saddles are symmetrically arranged at the bottom of the straight section. The overall determination method of the C-type tank is as follows:

[0107] S1: According to the density of the tank bulkhead material and the density of the internal liquid cargo, determine the load distribution characteristics of the tank along the length direction, and calculate the load distribution of the straight section and the load distribution of the head section respectively.

[0108] The length of the straight section is L, and the straight section has a uniformly distributed load q L The calculation formula is as follows:

[0109]

[0110] In the formula,

[0111] t is the average wall thickness of the cylinder, and the initial value is calculated by the following formula. For LNG tanks, t is not less than 0.02m. For CO2 tanks, t is not less than 0.05m. 。

[0112]

[0113] R i The inner radius of the C-type tank can be obtained from the initial design drawings.

[0114] ρ c It is the density of liquid cargo in type C tank, which is determined according to the type of liquid cargo to be loaded in the tank.

[0115] ρ m It is the material density of type C tank container, which is determined according to the type of material selected for the tank bulkhead.

[0116] R is the average value of the inner and outer radius of the straight tube section, R = R i +t / 2.

[0117] P0 is the design pressure of the tank.

[0118] σ m is the allowable stress corresponding to the tank material.

[0119] The length of the head section is H, and the total load of the head section is Q H It can be calculated by the following formula:

[0120]

[0121] The head section is equivalent to a straight tube section with the same diameter as the straight tube section, and the uniformly distributed load is q L , then the equivalent length L0 of the head section length H is calculated as follows:

[0122]

[0123] S2: Determine the saddle setting position based on the load distribution characteristics.

[0124] S2.1: First, select two saddles at any position and set them symmetrically. Calculate the support reaction force of the saddle at this time. The distance between the saddle and the end of the straight tube section is A. According to the load distribution of the head section and the straight tube section, the support reaction force Q at the saddle is calculated as:

[0125]

[0126] S2.2: Secondly, calculate the bending moment at the saddle and the mid-span of the tank. Combined with the load distribution along the length of the tank in S1 and the support reaction at the saddle in step S2.1, the bending moment at the saddle is calculated as:

[0127]

[0128] The bending moment at the mid-span of the tank is:

[0129]

[0130] S2.3: The final calculation of the saddle position for the tank size shows that the bending moment at the mid-span of the tank is equal to the bending moment at the saddle according to static equilibrium:

[0131] |M a |=|M b |

[0132] That is:

[0133]

[0134] The distance A between the saddle and the end of the straight section is calculated as follows:

[0135]

[0136] Further calculation is performed to obtain the distance X between the two saddles:

[0137]

[0138] S3: Based on the ship size characteristics and the stress characteristics of the tank structure, preliminarily determine the optimal range of the tank radius, tank length and saddle location.

[0139] In this embodiment, the C-type tank is the LNG fuel tank of a very large crude oil carrier (VLCC), and the target tank capacity requirement V is 3500m 2 , filled with LNG liquid cargo at -160℃, liquid cargo density ρ c 0.5t / m 3 , density of the tank bulkhead ρ m 7.85t / m 3 , the storage tank design pressure P0 is 0.45MPa.

[0140] S3.1 Determine the constraints for optimizing the tank size.

[0141] The constraints for tank size optimization include those provided by the ship layout, such as ship width, tank length, cabin height, blind area, deck equipment layout, and the constraints provided by the force angle of the tank structure.

[0142] 1) Constraints provided by ship layout

[0143] In this embodiment, the storage tank is arranged above the hull deck. The storage tank layout position needs to be considered based on the existing ship deck equipment conditions and must not affect the ship's blind area.

[0144] 2) Constraints determined by tank forces

[0145] In this embodiment, the storage tank is arranged above the hull deck, and the preferred range of the aspect ratio γ of the C-type storage tank is 3 to 6, which is calculated by the following formula:

[0146]

[0147] S3.2: Based on the tank size restriction conditions, the optimal range of tank radius and tank length is obtained to further determine the saddle setting position.

[0148] like Figure 4 As shown, combined with S3.1-1), this embodiment is arranged above the deck. First, according to the deck equipment layout, a feasible storage tank layout space is selected. At the same time, the storage tank layout must meet the ship blind area requirements. Therefore, the corresponding storage tank diameter range is R i ≤7.25m;

[0149] Combined with the optimal range of the tank aspect ratio γ determined in S3.1-2), the optimal range of the tank radius and the tank length can be obtained, and further the range of the distance X between the two saddles of the tank can be obtained.

[0150] The optimal range of tank radius is calculated by the following formula:

[0151]

[0152] The optimal interval of the length of the straight section of the tank is calculated by the following formula:

[0153]

[0154] like Figure 5 As shown in the figure, according to the preferred range of the aspect ratio, the relationship between the length L of the straight section and the inner diameter is a curve distribution feature. It is necessary to further combine the characteristics of the hull strong frame layout and the evaporation rate of the tank to determine the optimal size.

[0155] According to the formula in S1, the wall thickness t of the tank straight section is calculated to obtain the optimal interval L of the equivalent length L0 of the head section. 0min ~L 0max , L 0min =3.10m, L 0max =3.63m;

[0156] Then, according to the formula S2.3, the distance A between the saddle and the end of the straight tube section and the optimal interval A are calculated. min ~A max , the distance between the two saddles X and the optimal interval X min ~X max .

[0157] A min =4.50m, A max =9.05m

[0158] X min =22.93m, X max =34.18m

[0159] S4: Optimal interval X based on the distance between the two saddles in the tank min ~X max And the span of the hull frame support structure X S , the feasible tank saddle distance and feasible setting scheme are calculated, such as Figure 6 As shown;

[0160] In this embodiment, the span of the hull strong frame support structure is X S is 5.64m. Based on the range of the distance X between tank saddles determined in S3.2, a feasible arrangement scheme for tank saddles is obtained, that is, the number n of strong frame spans between two saddles can be 4, 5, or 6;

[0161] Under different schemes, the distance between the two corresponding storage tank saddles is X = n × X S , respectively 22.56m, 28.2m, 33.84m, such as Figure 7 shown.

[0162] According to the determined tank saddle setting scheme, combined with the tank distribution characteristics in step S2, the corresponding A, L0, and L are calculated in sequence;

[0163] According to the relevant formula in step S3.2, the corresponding tank inner diameter R is calculated. i A total of three plans were formed, see Table 1 for details.

[0164] plan Ri / m L / m X / m Solution 1 5.3 32.59 22.56 Solution 2 4.7 44.17 28.2 Option 3 4.4 51.68 33.84

[0165] Table 1

[0166] S5: For cryogenic pressure tanks, the evaporation rate of cryogenic liquid cargo is not only related to the material and thickness of the insulation layer, but also closely related to the size of the tank. Based on the three schemes determined in S4, the evaporation rates of each scheme are calculated, as shown in Table 2.

[0167]

[0168]

[0169] Table 2 Scheme 1 is the optimal solution.

[0170] plan Ri / m L / m X / m Solution 1 5.3 32.59 22.56

[0171] Table 3.

Claims

1. A method for determining the overall scheme of a C-type independent storage tank, characterized in that: The C-type tank is composed of a straight section in the middle and head sections at both ends. The straight section is a cylindrical structure with a circular cross section, and the head section is spherical. The two ends of the straight section and the head section are butt-jointed and welded together. Two saddles are symmetrically arranged at the bottom of the straight section. The overall determination method of the C-type tank is as follows: S1: According to the density of the tank wall material and the density of the internal liquid cargo, determine the load distribution characteristics of the tank along the length direction, and calculate the load distribution of the straight section and the load distribution of the head section respectively; The length of the straight section is L, and the straight section has a uniformly distributed load q L The calculation formula is as follows: q L =πR i 2 r c +2πRtρ m In the formula, t is the average wall thickness of the cylinder, and the initial value is calculated by the following formula; for LNG tanks, t is not less than 0.02m; for CO2 tanks, t is not less than 0.05m; R i The inner radius of the C-type tank can be obtained from the initial design drawings; ρ c The density of liquid cargo in a type C tank is determined according to the type of liquid cargo to be loaded in the tank; ρ m The material density of the C-type tank container is determined according to the type of material selected for the tank bulkhead; R is the average value of the inner and outer radius of the straight tube section, R = R i +t / 2; P0 is the tank design pressure; σ m is the allowable stress corresponding to the tank material; The length of the head section is H, and the total load of the head section is Q H It can be calculated by the following formula: The head section is equivalent to a straight tube section with the same diameter as the straight tube section, and the uniformly distributed load is q L , then the equivalent length L0 of the head section length H is calculated as follows: S2: Determine the saddle setting position based on the load distribution characteristics; S2.1: First, select two saddles at any position and set them symmetrically. Calculate the support reaction force of the saddle at this time. The distance between the saddle and the end of the straight tube section is A. According to the load distribution of the head section and the straight tube section, the support reaction force Q at the saddle is calculated as: S2.2: Secondly, calculate the bending moment at the saddle and the mid-span of the tank. Combined with the load distribution along the length of the tank in S1 and the support reaction at the saddle in step S2.1, the bending moment at the saddle is calculated as: The bending moment at the mid-span of the tank is: S2.3: The final calculation of the saddle position for the tank size shows that the bending moment at the mid-span of the tank is equal to the bending moment at the saddle according to static equilibrium: |M a |=|M b | That is: The distance A between the saddle and the end of the straight section is calculated as follows: Further calculation is performed to obtain the distance X between the two saddles: S3: Preliminarily determine the optimal interval of tank radius, tank length and saddle location according to the ship size characteristics and tank structure stress characteristics; S3.1 Determine the constraints for optimizing the tank size. The constraints for tank size optimization include those provided by the ship type layout, such as ship width, tank length, cabin height, blind area, deck equipment layout, and those provided by the force angle of the tank structure; 1) The constraints provided by the ship type layout need to be determined at the initial stage of determining the overall layout plan of the storage tanks based on the actual ship design characteristics; If the above-mentioned storage tank is arranged in the cargo hold area under the hull deck, it must meet the following requirements: - Tank diameter range determined by the ship's tank length: the tank's outer diameter in the length direction is not less than 700mm from the structural member at the transverse bulkhead; - Tank diameter range determined by the ship width: the outer diameter of the tank is not less than 700mm from the nearby hull structure in the ship width direction; - The range of tank diameter determined by the height of the ship's cabin: the minimum distance of the tank's outer diameter from the bottom hull continuous longitudinal member in the height direction is not less than 920mm, and the minimum distance from the top hull strong transverse beam panel in the height direction is not less than half the width of the strong transverse beam panel; If the storage tank is arranged above the hull deck, the storage tank layout position shall be considered based on the existing ship deck equipment and shall not affect the ship's blind area; 2) Considering the structural stress characteristics of the tank, the tank length-to-diameter ratio γ of the C-type tank arranged above the deck is usually limited. The preferred range of γ is 3 to 6. γ is calculated by the following formula: That is, the length of the straight section L and R i The functional relationship between L=2γR i S3.2: Based on the tank size constraints, obtain the tank inner radius R i and the optimal interval of the length L of the tank straight section, and further determine the saddle setting position. 1) Calculate the internal radius R of the tank i Optimized interval and straight section length L: According to the target tank capacity demand V, the relationship between the tank capacity and the tank size can be expressed as: According to the expression of aspect ratio γ, the relationship between aspect ratio γ and target tank capacity V is calculated: Then get According to S3.1, the preferred range of the aspect ratio γ is 3 to 6, and the tank inner diameter R is obtained. i The preferred interval of: R imin ~R imax ,in 2) Calculate the length L of the straight section of the tank: According to the expression of target tank capacity V, the length L of the tank straight section can be expressed as: That is, according to R i , V calculates the corresponding L value and its optimal interval L min ~L max ; 3) Calculate the wall thickness t of the tank straight section according to the formula in S1, and obtain the optimal interval L of the equivalent length L0 of the head section 0min ~L 0max ; 4) Then, the distance A from the end of the saddle to the straight section and the optimal interval A can be calculated according to formula S2.3: min ~A max , the distance between the two saddles X and the optimal interval X min ~X max ; S4: According to the arrangement plan of the hull strong support structure, determine the feasible arrangement plan of the tank saddle; according to the feasible arrangement plan of the saddle and the load distribution characteristics of the tank obtained in S2, carry out the optimization design of the tank length and tank radius to obtain multiple plans; The hull strong support structure arrangement scheme is obtained from the hull design drawings, and refers to the arrangement position of the hull transverse strong frame structure; The storage tank saddle should be set at the same position as the hull strong support structure to make full use of the hull structural characteristics and reduce the additional structural reinforcement design brought by the storage tank; 1) Based on the optimal interval X of the distance between the two saddles of the tank min ~X max And the span of the hull frame support structure X S , calculate the feasible tank saddle distance and feasible setting scheme; In the feasible saddle arrangement scheme, the tank saddle distance is calculated by the following formula: X=n×X S n is the number of spans of the hull frame; 2) According to the determined tank saddle distance X, combined with the tank distribution characteristics in step S2, the corresponding A, L0, and L are calculated in sequence; 3) According to the relevant formula in step S3.2, calculate the corresponding tank inner diameter R i ; S5: Calculate the evaporation rate of the liquid cargo tank under each scheme in S4 and determine the final design scheme; S5.1: Calculate the heat flux density q at different insulation materials of the tank wall. In the formula, T1, T2 are the inner and outer surface temperatures of the cylinder wall, in K; λ is the thermal conductivity of the material, which is determined by the specific material parameters; R o is the outer radius of the tank, R o =R i +t; S5.2 Calculation of cargo tank evaporation rate A simplified method is used to calculate the evaporation rate (BOR) of liquid cargo tanks. The evaporation rate (BOR) of liquid cargo tanks can be calculated using the following formula: In the formula, Q is the total heat entering the cargo tank, Q = ∑q × S, which is the sum of the product of the heat flux density q of different materials in different areas on the outer surface of the tank and the corresponding area S; r is the latent heat of vaporization of the liquid cargo in the tank, which is a parameter that matches the liquid cargo; The calculated evaporation rates of the cargo tanks of various schemes are compared and the final optimal scheme is selected, that is, the scheme with the smallest evaporation rate of the cargo tanks.

2. A method for determining a general scheme of a C-type independent storage tank according to claim 1, characterized in that: The saddle setting position A should make the stress of the C-type tank uniform and each stress does not exceed the allowable stress of the material, so as to improve the design safety of the C-type tank structure; at the same time, the saddle position should be consistent with the position of the hull structure strong frame to make full use of the hull structure characteristics and reduce the impact of the installation of the tank.

Images