Modelica-based modeling method for FPSO propulsion

Abstract

This invention belongs to the field of electronic digital data processing and discloses a propulsion modeling method for FPSOs based on Modelica, comprising the following steps: S1: Modeling the propulsion coefficient model of the propeller, including calculating the following parameters: thrust coefficient, thrust torque coefficient, thrust gain coefficient, and thrust torque gain coefficient; S2: Modeling the propeller performance model, including calculating the following parameters: wake coefficient, advance number, thrust loss coefficient, and relative rotational efficiency; S3: Based on the results of steps S1 and S2, outputting the thrust and thrust torque of the propeller, thereby obtaining the propulsion efficiency of the propeller. This method can comprehensively simulate the thrust and torque variation characteristics of the propeller under different operating conditions through a discrete dynamic modeling approach, thus providing accurate simulation support for the dynamic response of FPSO systems in complex marine environments.

Description

Technical Field

[0001] This invention belongs to the field of electronic digital data processing, and specifically relates to an FPSO advancement modeling method based on Modelica. Background Technology

[0002] Floating Production Storage and Offloading (FPSO) vessels are key facilities for offshore oil and gas development, primarily used for the extraction, processing, storage, and transportation of offshore oil, natural gas, and other energy resources. FPSO systems typically rely on propeller propulsion systems for positioning, navigation, and stability control. As the core propulsion unit of the FPSO, the propeller's performance directly impacts its operational efficiency and safety in complex marine environments. FPSO propeller propulsion systems must cope with complex environmental conditions, such as the combined effects of waves, wind, and ocean currents, resulting in highly nonlinear and time-varying dynamic responses from the propeller. Therefore, establishing an accurate dynamic model of the propeller propulsion system is crucial for analyzing and optimizing the propulsion efficiency and operational stability of the FPSO.

[0003] The Modelica language unifies various multi-domain unified modeling mechanisms in principle, directly supporting block diagram-based modeling, object-oriented and component-oriented modeling. Through the generalized Kirchhoff network mechanism based on ports and connections, it can simultaneously describe mechanical, hydraulic and control systems, providing an ideal platform for multi-domain coupled modeling of propulsion systems. Summary of the Invention

[0004] This invention provides a propulsion modeling method for FPSO based on Modelica. This method can comprehensively simulate the thrust and torque variation characteristics of the propeller under different operating conditions through discrete dynamic modeling, thereby providing accurate simulation support for the dynamic response of FPSO systems in complex marine environments.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a Modelica-based FPSO propulsion modeling method, wherein the modeling method includes modeling the propulsion coefficient model and the propulsion performance model of the propeller using the Modelica language, and simulating the propeller propulsion system by modeling the propulsion coefficient model and the propeller performance model; the propulsion modeling method includes the following steps:

[0006] S1: Model the propeller's thrust coefficient, including calculating the following parameters: thrust coefficient, thrust torque coefficient, thrust gain coefficient, and thrust torque gain coefficient;

[0007] S2: Model the propeller performance, including calculating the following parameters: wake coefficient, advance number, thrust loss coefficient, and relative rotational efficiency;

[0008] S3: Based on the results of steps S1 and S2, output the propeller's thrust and thrust torque, and thus obtain the propeller's propulsion efficiency.

[0009] Preferably, the formulas for calculating the thrust coefficient and thrust moment coefficient in step S1 are as follows:

[0010] (1)

[0011] (2)

[0012] in, It is the thrust coefficient, is the thrust torque coefficient, Interp is the interpolation function, J is the forward number, P / D is the propeller pitch ratio, z is the number of propeller blades, and D is the propeller diameter.

[0013] Preferably, the calculation formulas for the thrust gain coefficient and thrust torque gain coefficient in step S1 are as follows:

[0014] (3)

[0015] (4)

[0016] (5)

[0017] (6)

[0018] in, It is the thrust gain coefficient. is the thrust gain coefficient, Interp is the interpolation function, J is the forward velocity, P / D is the propeller pitch ratio, z is the number of propeller blades, D is the propeller diameter, and Re is the Reynolds number. It is an intermediate coefficient based on propeller geometry parameters, V a is the propeller's forward speed, n is the propeller's rotational speed, U is the blade area ratio, and v is the fluid's dynamic viscosity.

[0019] Preferably, the formula for calculating the wake coefficient in step S2 is:

[0020] (7)

[0021] (8)

[0022] (9)

[0023] (10)

[0024] (11)

[0025] Where w is the wake coefficient, He is the captain. Is it the width of the boat? It is the stern draft, It is the longitudinal center of buoyancy position. It is the drag correction factor. It is the ship type factor, It is the coefficient of frictional resistance. It is the shape of a single-propeller stern. It is the rhombus coefficient. It is the midship section coefficient, It is the square coefficient. It is the wetted surface area, It is the propeller diameter, and and and It is an intermediate coefficient.

[0026] Preferably, the formula for calculating the forward number in step S2 is:

[0027] (12)

[0028] (13)

[0029] Where J is the forward number, n is the forward speed, D is the propeller speed, V is the propeller diameter, and W is the wake coefficient.

[0030] Preferably, the formula for calculating the thrust loss coefficient in step S2 is:

[0031] (14)

[0032] in, It is the thrust loss coefficient. Captain Is it the width of the boat? It is the propeller diameter, It is the stern draft, It is the rhombus coefficient. It is the longitudinal center of buoyancy position. It has the shape of a single-propeller stern.

[0033] Preferably, the formula for calculating the relative rotational efficiency in step S2 is:

[0034] (15)

[0035] in, It is the relative rotational efficiency, and U is the blade area ratio. It is the rhombus coefficient. It is the longitudinal center of buoyancy position.

[0036] Preferably, the formulas for calculating the thrust and thrust torque of the output propeller in step S3 are as follows:

[0037] (16)

[0038] (17)

[0039] Where Q is the thrust torque, T is the thrust, It is the thrust torque coefficient. Where n is the thrust coefficient, n is the propeller speed, and D is the propeller diameter. It is the density of water. It is the thrust loss coefficient.

[0040] Preferably, the formula for calculating the propeller's propulsion efficiency in step S3 is:

[0041] (18)

[0042] in, Q is the propeller's propulsion efficiency, T is the thrust, and n is the propeller speed. It is relative rotational efficiency, It refers to forward speed.

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] 1. This invention accurately calculates propeller thrust and thrust loss based on input parameters such as propeller structural parameters and speed. By using formulas to model and calculate the thrust loss coefficient, it can better simulate propeller propulsion efficiency, reduce modeling errors, and perform calculations and fitting of various performance parameters. Through the fitting of multiple performance parameters such as thrust coefficient, thrust torque coefficient, and relative rotational efficiency, it provides detailed analytical basis for propeller performance under different speed and load conditions, ensuring optimized design of the propulsion system.

[0045] 2. This invention uses standardized interface input and output parameter definitions to make the model easy to extend, maintain and reuse, thereby reducing the workload and complexity of subsequent development and application;

[0046] 3. This invention constructs a multi-domain coupled model of propeller thrust coefficient model and propeller performance model using Modelica language, realizing dynamic simulation and optimization of propeller propulsion system, comprehensively simulating the thrust and torque variation characteristics of propeller under different operating conditions, thereby providing accurate simulation support for the dynamic response of FPSO system in complex marine environment. Detailed Implementation

[0047] The technical solutions of the present invention will be clearly and completely described below with reference to embodiments thereof. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0048] This invention provides a technical solution: a Modelica-based FPSO propulsion modeling method. The modeling method includes using the Modelica language to model the propulsion coefficient model and the propulsion performance model of the propeller. Simulation of the propeller propulsion system is then performed by modeling the propulsion coefficient model and the propeller performance model. The propeller propulsion modeling method includes the following steps:

[0049] S1: Model the propeller's thrust coefficient, including calculating the following parameters: thrust coefficient, thrust torque coefficient, thrust gain coefficient, and thrust torque gain coefficient;

[0050] In propeller propulsion system modeling, the propulsion coefficient is a key parameter, encompassing thrust coefficient, thrust moment coefficient, thrust gain, and thrust moment gain. These coefficients can be accurately calculated using interpolation methods, taking into account various parameters such as advance rate, pitch ratio, number of blades, and propeller diameter. Furthermore, the thrust gain and thrust moment gain are calculated using Reynolds number interpolation.

[0051] The formulas for calculating the thrust coefficient and thrust moment coefficient are as follows:

[0052] (1)

[0053] (2)

[0054] in, It is the thrust coefficient, is the thrust torque coefficient, Interp is the interpolation function, J is the forward number, P / D is the propeller pitch ratio, z is the number of propeller blades, and D is the propeller diameter.

[0055] Thrust coefficient It is the ratio of the thrust generated by the propeller to its geometric parameters and water flow conditions. Thrust moment coefficient. This is a coefficient relating the torque generated by the propeller to its operating conditions. Interp is the interpolation function; specifically, it's an interpolation table created in the CombiTable1D component of the Modelica standard library, used to store the variables J (forward speed), P / D (pitch ratio), z (number of blades), and D (propeller diameter). and Values. Each row of data represents a unique combination, containing the input values ​​for these variables and their corresponding thrust coefficients. or thrust moment coefficient Finally, the interpolation result output by CombiTable1D is used to obtain the final result. and The value of is determined to meet the requirements of formulas (1) and (2).

[0056] The formulas for calculating the thrust gain coefficient and the thrust torque gain coefficient are as follows:

[0057] (3)

[0058] (4)

[0059] (5)

[0060] (6)

[0061] in, It is the thrust gain coefficient. is the thrust gain coefficient, Interp is the interpolation function, J is the forward velocity, P / D is the propeller pitch ratio, z is the number of propeller blades, D is the propeller diameter, and Re is the Reynolds number. It is an intermediate coefficient based on propeller geometry parameters, V a is the propeller's forward speed, n is the propeller's rotational speed, U is the blade area ratio, and v is the fluid's dynamic viscosity.

[0062] Thrust gain coefficient This is a further correction to the thrust coefficient, reflecting the variation in propeller thrust under specific flow conditions. Thrust torque gain This is a correction to the thrust torque coefficient, taking into account the propeller's torque characteristics under different fluid conditions. The specific interpolation function here creates an interpolation table in the CombiTable1D component of the Modelica standard library to store the variables J (forward number), P / D (pitch ratio), z (number of blades), D (propeller diameter), and Re (Reynolds number). and Values. Each row of data represents a unique combination, containing the input values ​​for these variables and their corresponding thrust coefficients. or thrust moment coefficient Finally, the interpolation result output by CombiTable1D is used to obtain the final result. and The value of is determined to meet the requirements of formulas (3) and (4).

[0063] S2: Model the propeller performance, including calculating the following parameters: wake coefficient, advance number, thrust loss coefficient, and relative rotational efficiency;

[0064] The wake coefficient w is calculated based on the ship's geometric parameters and the propeller's characteristics. The specific formula is as follows:

[0065] (7)

[0066] (8)

[0067] (9)

[0068] (10)

[0069] (11)

[0070] Where w is the wake coefficient, Captain Is it the width of the boat? It is the stern draft, It is the longitudinal center of buoyancy position. It is the drag correction factor. It is the ship type factor, It is the coefficient of frictional resistance. It is the shape of a single-propeller stern. It is the rhombus coefficient. It is the midship section coefficient, It is the square coefficient. It is the wetted surface area, It is the propeller diameter, and and and These are intermediate coefficients. In Modelica, these parameters are defined as input variables. By inputting the geometric parameters of the hull and propeller, the system will automatically calculate the wake coefficient w, which is then used for subsequent propeller thrust and efficiency calculations.

[0071] Forward speed mainly relates to the time and distance required for a ship to reach a stable speed after starting its main engine from a stationary state. These parameters are of great significance to the ship's maneuverability and navigation efficiency. The specific calculation formula is as follows:

[0072] (12)

[0073] (13)

[0074] Where J is the forward number, n is the forward speed, D is the propeller speed, V is the propeller diameter, and W is the wake coefficient.

[0075] The thrust loss coefficient is one of the key parameters describing the propulsion efficiency of a propeller. It mainly reflects the thrust loss caused by drag in water flow. The specific calculation formula is as follows:

[0076] (14)

[0077] in, It is the thrust loss coefficient. Captain Is it the width of the boat? It is the propeller diameter, It is the stern draft, It is the rhombus coefficient. It is the longitudinal center of buoyancy position. This refers to the stern shape of a single-propeller ship. The thrust loss coefficient formula also depends on the ship's geometry and the propeller's characteristics. This formula allows for the accurate calculation of the thrust loss coefficient, which can then be combined with the wake coefficient for evaluating propeller thrust and efficiency.

[0078] Relative rotational efficiency is a crucial parameter affecting the actual working efficiency of a propeller, reflecting the difference between its actual operating state and its design theory. The specific calculation formula is as follows:

[0079] (15)

[0080] in, It is the relative rotational efficiency, and U is the blade area ratio. It is the rhombus coefficient. It is the longitudinal center of buoyancy position.

[0081] S3: Based on the results of steps S1 and S2, output the propeller's thrust and thrust torque, and thus obtain the propeller's propulsion efficiency.

[0082] The formulas for calculating the thrust and thrust torque of the output propeller are as follows:

[0083] (16)

[0084] (17)

[0085] Where Q is the thrust torque, T is the thrust, It is the thrust torque coefficient. Where n is the thrust coefficient, n is the propeller speed, and D is the propeller diameter. It is the density of water. It is the thrust loss coefficient.

[0086] The formula for calculating the propulsion efficiency of a propeller is:

[0087] (18)

[0088] in, Q is the propeller's propulsion efficiency, T is the thrust, and n is the propeller speed. It is relative rotational efficiency, It refers to forward speed.

[0089] Finally, based on the results of the propeller thrust coefficient model and propeller performance model, the propeller thrust T and thrust torque Q are calculated. The propulsion efficiency is then derived from the propeller thrust and thrust torque. Based on the results, it is determined whether the propeller has good thrust and propulsion efficiency under the current speed and operating conditions. Designers can then further optimize the propeller geometry or adjust the operating conditions based on these data to improve propulsion performance.

[0090] Example:

[0091] This paper presents a detailed simulation of a propeller propulsion system based on a propeller thrust coefficient model and a propeller performance model. By inputting the geometric parameters of the FPSO vessel, propeller design parameters, and operating conditions, the model outputs performance indicators such as propeller thrust, thrust torque, and propulsion efficiency. This implementation case study will detail the steps, data input, model operation, and result interpretation during the simulation process.

[0092] This invention analyzes the propulsion performance of a ship's propeller under specific speed and operating conditions. It uses simulation calculations to determine the thrust coefficient, thrust torque coefficient, thrust gain, thrust torque gain, and the propeller's thrust and torque, ultimately evaluating the propeller's propulsion efficiency.

[0093] In the simulation, the parameters we need to input include:

[0094] Ship geometric parameters ;

[0095] Ship propeller geometry parameters ;

[0096] Ship speed V, propeller speed n;

[0097] Fluid property parameters ;

[0098] These parameters are input into the propeller thrust model, and the parameters are processed according to the following steps, ultimately outputting thrust, thrust torque, and propulsion efficiency.

[0099] 1. Calculate the thrust coefficient using interpolation based on the propeller's forward velocity, pitch ratio, number of blades, and propeller diameter. Similarly, derive the thrust torque coefficient using interpolation.

[0100] 2. Considering the Reynolds number Re, correct the thrust coefficient and thrust moment coefficient, and obtain the thrust and thrust moment gain coefficients based on the Reynolds number and interpolation method;

[0101] 3. Calculate the wake coefficient of the propeller based on the ship's geometric parameters and the propeller's design parameters;

[0102] 4. Calculate the thrust loss coefficient using hull and propeller parameters;

[0103] 5. Calculate the relative rotational efficiency by combining the propeller parameters and the longitudinal center of buoyancy of the ship;

[0104] 6. Based on the results of the propeller thrust coefficient model and the propeller performance model, calculate the propeller thrust and thrust torque Q, and finally derive the propulsion efficiency based on the propeller thrust and thrust torque.

[0105] The specific parameter calculation and modeling process is as follows:

[0106] Ship parameters:

[0107] Length L=100m, beam B=15m, draft at stern T A =7m, ship speed V=12knots (approximately 6.17m / s), longitudinal center of buoyancy position =0.05;

[0108] Propeller parameters:

[0109] The propeller diameter is D=4.5m, the number of blades is z=4, the pitch ratio is P / D=0.85, the rotational speed is n=150RPM, and the blade area ratio is U=0.65.

[0110] Fluid parameters:

[0111] The dynamic viscosity of water is v = 1.14 × 10⁻⁶. -6 m 2 / s, the density of water ρ = 1025 kg / m³ 3 ;

[0112] Thrust coefficient k t Calculation:

[0113] The thrust coefficient k is calculated by interpolation based on the propeller's forward velocity J, pitch ratio P / D, number of blades z, and propeller diameter D. t ;

[0114] ;

[0115] According to the interpolation method, we obtain: k t =0.12

[0116] Thrust moment coefficient k q Calculation:

[0117] Similarly, the thrust torque coefficient, k, is obtained through interpolation. q =0.025

[0118] Thrust gain coefficient and thrust gain coefficient Calculation:

[0119] After considering the Reynolds number Re and other factors, the thrust coefficient and thrust moment coefficient are corrected as follows:

[0120] ;

[0121] The gain coefficient is obtained by interpolation based on the Reynolds number:

[0122] ;

[0123] Calculate the propeller wake coefficient w based on the ship's geometric parameters and propeller design parameters:

[0124] ;

[0125] Thrust loss coefficient Calculation:

[0126] Calculate the thrust loss coefficient using hull and propeller parameters:

[0127] ;

[0128] Relative rotational efficiency Calculation:

[0129] Calculate the relative rotational efficiency by combining propeller parameters and the longitudinal center of buoyancy of the ship:

[0130] ;

[0131] Calculation of the forward number J:

[0132] The forward number is calculated as follows:

[0133] ;

[0134] Based on the results of the propeller thrust coefficient model and the propeller performance model, the propeller thrust and thrust torque are calculated:

[0135] Thrust T:

[0136] ;

[0137] ;

[0138] Thrust torque Q:

[0139] ;

[0140] ;

[0141] Calculation of propulsion efficiency:

[0142] Improve efficiency The calculation is as follows:

[0143] ;

[0144] ;

[0145] Simulation Result Analysis:

[0146] Through the above simulation steps, the following key results were obtained:

[0147] ;

[0148] The results show that the propeller has good thrust and propulsion efficiency under the current speed and operating conditions. Ship designers can use this data to further optimize the propeller geometry or adjust operating conditions to improve propulsion performance.

[0149] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A modelica-based FPSO pusher modeling method, characterized in that: The modeling method includes using the Modelica language to model the propulsion coefficient model and the propulsion performance model of the propeller, and then simulating the propeller propulsion system by modeling the propulsion coefficient model and the propeller performance model; the propulsion modeling method includes the following steps: S1: Model the propeller's thrust coefficient, including calculating the following parameters: thrust coefficient, thrust torque coefficient, thrust gain coefficient, and thrust torque gain coefficient; S2: Model the propeller performance, including calculating the following parameters: wake coefficient, advance number, thrust loss coefficient, and relative rotational efficiency; S3: Based on the results of steps S1 and S2, output the propeller's thrust and thrust torque, and thus obtain the propeller's propulsion efficiency. The formulas for calculating the thrust gain coefficient and thrust torque gain coefficient in step S1 are as follows: （3） （4） （5） （6） in, It is the thrust gain coefficient. is the thrust gain coefficient, Interp is the interpolation function, J is the forward velocity, P / D is the propeller pitch ratio, z is the number of propeller blades, D is the propeller diameter, and Re is the Reynolds number. It is an intermediate coefficient based on propeller geometry parameters, V a is the propeller's forward speed, n is the propeller's rotational speed, U is the blade area ratio, and v is the fluid's dynamic viscosity. The formulas for calculating the thrust and thrust torque of the output propeller in step S3 are as follows: （16） （17） Where Q is the thrust torque, T is the thrust, It is the thrust torque coefficient. Where n is the thrust coefficient, n is the propeller speed, and D is the propeller diameter. It is the density of water. It is the thrust loss coefficient; The formula for calculating the propeller's propulsion efficiency in step S3 is as follows: （18） in, Q is the propeller's propulsion efficiency, T is the thrust, and n is the propeller speed. It is relative rotational efficiency, It is the forward speed; The formula for calculating the tracing coefficient in step S2 is as follows: （7） （8） （9） （10） （11） Where w is the wake coefficient, He is the captain. Is it the width of the boat? It is the stern draft, It is the longitudinal center of buoyancy position. It is the drag correction factor. It is the ship type factor, It is the coefficient of frictional resistance. It is the shape of a single-propeller stern. It is the rhombus coefficient. It is the midship section coefficient, It is the square coefficient. It is the wetted surface area, It is the propeller diameter, and and and It is an intermediate coefficient.

2. The FPSO advancement modeling method based on Modelica according to claim 1, characterized in that: The formulas for calculating the thrust coefficient and thrust moment coefficient in step S1 are as follows: （1） （2） in, It is the thrust coefficient, is the thrust torque coefficient, Interp is the interpolation function, J is the forward number, P / D is the propeller pitch ratio, z is the number of propeller blades, and D is the propeller diameter.

3. The FPSO advancement modeling method based on Modelica according to claim 1, characterized in that: The formula for calculating the forward number in step S2 is as follows: （12） （13） Where J is the forward number, n is the forward speed, D is the propeller speed, V is the propeller diameter, and W is the wake coefficient.

4. The FPSO advancement modeling method based on Modelica according to claim 1, characterized in that: The formula for calculating the thrust loss coefficient in step S2 is as follows: （14） in, It is the thrust loss coefficient. He is the captain. Is it the width of the boat? It is the propeller diameter, It is the stern draft, It is the rhombus coefficient. It is the longitudinal center of buoyancy position. It has the shape of a single-propeller stern.

5. The FPSO advancement modeling method based on Modelica according to claim 1, characterized in that: The formula for calculating the relative rotation efficiency in step S2 is as follows: （15） in, It is the relative rotational efficiency, and U is the blade area ratio. It is the rhombus coefficient. It is the longitudinal center of buoyancy position.

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