A method for calculating the transport work of a tug

Abstract

The present application aims to provide a towing vessel transport work calculation method, comprising the following steps: using the method of mooring column towing force test to calibrate the pushing force of the towing vessel; using the collected towing vessel speed, propeller speed and rudder angle, using numerical integration method to calculate the actual transport work of the towing vessel. The present application considers the operation characteristics of the specific type of ship, and proposes to use the towing vessel pushing force as a parameter to replace the total tonnage and deadweight tonnage of the conventional ship, multiply by the speed and integrate to calculate the transport work of the towing vessel, which can accurately and effectively describe the operation capacity of the towing vessel. The present application proposes to use the method of mooring column towing force test to calibrate the effective towing force of the towing vessel, and then calculate the effective pushing force of the towing vessel using the propeller speed and rudder angle.

Description

TECHNICAL FIELD

[0001] The present application relates to a ship transportation calculation method. BACKGROUND

[0002] The shipping industry is an important support for global trade and world economic development, and is also the most economical and energy-saving transportation mode, but at the same time, it also produces a large amount of CO2 emissions. In response to the call for energy saving and emission reduction, the International Maritime Organization has developed a series of mandatory rules and guiding documents to promote the improvement of ship energy efficiency from the aspects of technology and operation, including developing a series of energy efficiency (EEOI, EEDI, EEXI, etc.), energy consumption (unit transportation work fuel consumption, etc.), emission (CII, etc.) indicators to supervise ships to implement various energy saving and emission reduction measures. In order to define the operation capacity of the ship and evaluate its energy efficiency, energy consumption and emission level, the transportation work of the ship needs to be defined and calculated.

[0003] Currently, the transportation work is usually calculated by the product of the sailing distance and the transportation cargo quantity. In the absence of actual transportation work data, the supplied transportation work (W s ) is taken as the basis, which is defined as the product of the carrying capacity of the ship and the sailing distance in a given calendar year, as shown in the following formula:

[0004] W s =C×D t (1)

[0005] In the formula:

[0006] C represents the carrying capacity of the ship, and for bulk carriers, liquid cargo ships, container ships, gas transport ships, LNG ships, ro-ro cargo ships, general cargo ships, refrigerated cargo ships and dual-purpose ships, the deadweight tonnage (DWT) should be used as the carrying capacity; for luxury cruise ships, ro-ro cargo ships (vehicle transport ships) and ro-ro passenger ships, the gross tonnage (GT) should be used as the carrying capacity;

[0007] D t represents the total sailing distance (nautical miles) reported in the IMO DCS.

[0008] The current transportation work calculation method only considers 12 types of ships, including bulk carriers, liquid cargo ships, container ships, gas transport ships, LNG ships, ro-ro cargo ships, general cargo ships, refrigerated cargo ships, dual-purpose ships, luxury cruise ships, ro-ro cargo ships (vehicle transport ships) and ro-ro passenger ships, without considering some specific types of ships. The calculation formula does not take into account the differences caused by different operating characteristics of the ship, and only uses gross tonnage or deadweight tonnage as the transportation work calculation parameter, which cannot accurately represent the operating capacity of different ships, especially for tugboats, using gross tonnage or deadweight tonnage to calculate the transportation work is meaningless. SUMMARY

[0009] The purpose of this invention is to provide a method for calculating the transport capacity of tugboats, which can effectively calculate the carrying capacity of tugboats and lay the foundation for the assessment of the operational capacity, energy efficiency and emissions of tugboats.

[0010] The objective of this invention is achieved as follows:

[0011] This invention provides a method for calculating the transport work of tugboats, characterized by:

[0012] Step 1: The jacking force of the tugboat is calibrated using the bollard towing force test method;

[0013] Step 2: Using the collected data on tugboat speed, propeller speed, and rudder angle, calculate the actual transport work of the tugboat using numerical integration.

[0014] The present invention may also include:

[0015] 1. After the ship is built, passes sea trials, and all instruments used for testing are installed, a bollard towing force test will be conducted. During the test, a steel cable with a tension sensor in the middle will be used, with one end tied to a bollard on the dock and the other end tied to the drum on the tugboat's main towing cable winch. At the start of the test, the main engine power output will be stably set at 100%, and the stable tension will be maintained for 10 minutes. With the tugboat moving straight forward without any deviation, the towing force readings will be recorded 10 times. The average towing force reading is the bollard towing force at 100% main engine power. The main engine power was successively reduced, and towing tests were conducted at 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, and 10% of the main engine power. The stable towing force at each level was maintained for 10 minutes, and the towing gauge readings, main engine power, and propeller speed were recorded 10 times. A propeller speed versus towing force curve was plotted to obtain the tugboat towing force curve corresponding to different propeller speeds. The effective jacking force of the tugboat during towing operations can be calculated using the propeller speed and propeller rudder angle, as shown in the following formula:

[0016] F = T·cosθ

[0017] In the formula: T is the tractor's traction force, which can be obtained by using the propeller speed through the above calibration method; θ is the propeller rudder angle. When multiple tugboats work together, the effective thrust takes into account the angle between the propulsion direction and the actual navigation direction, i.e., the propeller rudder angle.

[0018] 2. The specific method for calculating the actual transport work of the tugboat in step two is as follows: the trapezoidal complex quadrature method is used:

[0019]

[0020] In the formula, t1, t2: the start and end times of the extracted tugboat pushing force and speed data; W: the tugboat's transport work during the period from t1 to t2; vk : the kth extracted speed data, f k : the kth calculated instantaneous pushing force based on the propeller speed and the rudder angle, n: the number of extracted data; T: the time step of data collection.

[0021] The advantages of the present application are:

[0022] 1. The present application considers the operating characteristics of the tugboat, a specific type of ship, and proposes to use the tugboat pushing force as a parameter to replace the total tonnage and deadweight tonnage of conventional ships, multiply by the speed and integrate to calculate the transport work of the tugboat, which can accurately and effectively describe the operating capacity of the tugboat.

[0023] 2. The present application proposes to use the mooring column drag force test method to calibrate the effective drag force of the tugboat, and then use the propeller speed and the rudder angle to calculate the effective pushing force of the tugboat.

[0024] The present application considers the operating characteristics and actual operating conditions of the tugboat, uses the effective pushing force of the tugboat and the speed against water to calculate the transport work of the tugboat, which can more accurately and effectively describe the operating capacity of the tugboat, and lays a foundation for performance evaluation of the tugboat in terms of energy efficiency, energy consumption, emissions and other aspects. BRIEF DESCRIPTION OF DRAWINGS

[0025] Fig. 1 is a layout diagram of the mooring column drag force test of the tugboat.

[0026] Fig. 2 is a flowchart of the transport work calculation of the tugboat. DETAILED DESCRIPTION

[0027] The present application will be described in more detail below with examples combined with the drawings:

[0028] In combination with Figs. 1-2 , the present application includes the following steps:

[0029] Step 1: Calibrate the pushing force of the tugboat using the mooring column drag force test method.

[0030] The bollard towing force test is carried out after the ship is built and qualified by navigation test and the instruments used for the test are installed. In the test process, a steel cable with a tensile sensor in the middle is used, one end of which is tied to the bollard pile (cable pile) on the wharf, and the other end is tied to the reel on the main towing winch of the tugboat. When the test starts, the main engine power is stabilized at 100%, the stable tension is maintained for 10 minutes, and the tugboat is tested to record the towing force reading 10 times in the straight forward direction without any deviation. The average value of the towing force measurement is the bollard towing force under 100% main engine power. The main engine power is gradually reduced, and the towing force test is carried out under 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20% and 10% main engine power. The stable tension of each gear is maintained for 10 minutes, and the tension table reading, main engine power and propeller speed are recorded 10 times, and the propeller speed and towing force curve diagram is drawn, that is, the corresponding towing force curve of different propeller speeds of the tugboat is obtained. The effective pushing operation force of the tugboat during the towing operation can be calculated by the propeller speed and the propeller angle, as shown in formula (2).

[0031] F = T cos θ (2) In the formula:

[0032] T is the towing force of the tugboat, which is obtained by the above calibration method by using the propeller speed;

[0033] θ is the propeller angle. There may be multiple tugboats working together during the operation of the tugboat, so the effective pushing force needs to consider the angle between the propelling direction and the actual sailing direction, that is, the propeller angle.

[0034] Step two: using the collected tugboat speed, propeller speed and angle, the actual transport work of the tugboat is calculated by numerical integration method, formula (3) uses trapezoidal complex integration method as an example.

[0035]

[0036] In the formula, t1, t2: the starting time and the ending time of the extracted tugboat pushing operation force and speed data;

[0037] W: the tugboat transport work in the period from t1 to t2, t·n mile;

[0038] v k : the kth speed data extracted, m / s, the integral of the speed is the navigation mileage;

[0039] f k : the kth instantaneous pushing force calculated based on the propeller speed and the angle according to formula (2), t;

[0040] n: the number of extracted data;

[0041] T: the time step of data collection.

[0042] In the absence of actual pushing force data, the design column drag force of the tugboat is taken as the pushing force of the tugboat, and the distance of the voyage is multiplied to calculate the transport work of the tugboat; the numerical integration method used in the calculation of the transport work of the tugboat can be any numerical integration method, the above-mentioned composite trapezoidal integration method, the composite Simpson integration method, the adaptive integration, the Romberg integration and the Gauss integration and other integration methods can also be used.

Claims

1. A method for calculating the transport work of a tugboat, characterized by the following steps: Step 1: Calibrating the pushing force of the tugboat using a mooring post towing force test; After the ship is built and the test instruments are installed, the mooring post towing force test is performed. During the test, a steel cable with a tension sensor in the middle is used, one end is tied to a mooring post on the wharf, and the other end is tied to the reel of the main towing winch of the tugboat. At the beginning of the test, the engine power is set to 100%, and the steady tension is maintained for 10 minutes. The tugboat is pulled straight forward without any deviation, and the towing force readings are recorded 10 times. The average value of the towing force readings is the mooring post towing force at 100% engine power. The engine power is gradually reduced to 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, and 10%, respectively, and the towing force test is performed at each power level. The steady tension is maintained for 10 minutes, and the tension table readings, engine power, and propeller speed are recorded 10 times. The propeller speed and towing force curve is drawn, and the corresponding towing force curve of the tugboat at different propeller speeds is obtained. The effective pushing force F of the tugboat during towing operation can be calculated using the propeller speed and propeller angle, as follows: F = A cos θ where A is the towing force of the tugboat, which is obtained by the calibration method described above and the propeller speed; θ is the propeller angle, which is the angle between the pushing direction and the actual sailing direction during the operation of the tugboat, i.e. the propeller angle; Step 2: Using the collected tugboat speed, propeller speed, and angle, and using the numerical integration method, the actual transport work of the tugboat is calculated. The specific method for calculating the actual transport work of the tugboat is as follows: using the trapezoidal complex integration method. ​ ​ ​ ​ ​ 2. The method for calculating the transport work of a tugboat according to claim 1, characterized in that: ​ wherein t1 and t2 represent the start time and end time of the extracted tugboat pushing operation force and speed data; W represents the tugboat transportation work during the period from t1 to t2; v k represents the extracted kth speed data; f k represents the kth instantaneous pushing force calculated based on the propeller rotation speed and the rudder angle; n represents the number of extracted data; T represents the time step of data collection.

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