A method for evaluating the energy-saving effect of energy-saving devices in waves

Abstract

The present invention discloses a method for evaluating the energy-saving effect of an energy-saving device in waves. The method uses a ship model and an energy-saving device for test evaluation. The ship model is equipped with a self-propulsion power system. The load-assisted self-propulsion method in still water replaces the currently used self-propulsion method in waves. This method solves the problems of high uncertainty and high test costs associated with conducting self-propulsion model tests directly in waves. The load-assisted self-propulsion method enables a more accurate and efficient evaluation of the energy-saving effect of the energy-saving device in waves under more controllable test conditions. The proposed method helps reflect the energy-saving effect of the energy-saving device under real-world sailing conditions at sea. Furthermore, through design optimization, the energy-saving device can achieve optimal performance under different sea conditions. This method not only helps ships meet strict environmental regulations but also significantly reduces fuel costs in operating costs, bringing long-term economic benefits to shipowners.

Description

Technical Field

[0001] The invention relates to a method for evaluating the energy-saving effect of an energy-saving device in waves, and belongs to the technical field of ship performance evaluation. Background Art

[0002] With the International Maritime Organization (IMO) continuously tightening its standards for ship energy efficiency and carbon emissions, the shipping industry faces the significant challenge of reducing greenhouse gas emissions and improving energy efficiency. Consequently, ship energy-saving devices have emerged and have become increasingly widely used in recent years. Energy-saving devices achieve energy conservation and emission reduction goals by improving a ship's hydrodynamic performance and enhancing the efficiency of its propulsion system. These devices not only help ships meet stringent environmental regulations but also significantly reduce fuel costs, thereby generating long-term economic benefits for shipowners.

[0003] At present, the design and effect verification of energy-saving devices are usually carried out in a still water environment. This is because the still water environment provides a relatively stable and easy-to-control basic condition, which is convenient for evaluating the basic performance of energy-saving devices. However, the energy-saving effect evaluation based on still water has certain limitations, which are mainly reflected in the complex and changeable marine environment. During actual navigation, ships will inevitably encounter the impact of wind and waves. Testing in still water cannot fully simulate the dynamic environment under these real conditions, resulting in the actual performance of energy-saving devices may be significantly different from the model test results. Therefore, it is of great significance to verify the effect of energy-saving devices in a wave environment. It can more accurately evaluate the performance of energy-saving devices under real navigation conditions, and then through design optimization, the energy-saving devices can achieve the best effect under different sea conditions.

[0004] There are two main existing methods for evaluating the energy-saving effect of energy-saving devices in waves:

[0005] (1) Computational fluid dynamics (CFD) methods are used to numerically simulate the self-propulsion of a ship in waves. The power required for propulsion with and without an energy-saving device is obtained, and the effect of the energy-saving device is determined by the difference between the two.

[0006] Disadvantages: CFD numerical simulation methods for self-propulsion in waves are immature. Results are significantly affected by factors such as mesh quality, turbulence patterns, and time steps. Without model testing, conclusions are less reliable. Furthermore, CFD simulations are computationally intensive, typically requiring several days to perform a single calculation. A comprehensive assessment of the performance of energy-saving devices in waves can take months, resulting in prohibitively high time costs. Consequently, CFD numerical simulation methods are currently limited to research applications.

[0007] (2) Evaluation is conducted by conducting a self-propulsion model test of a ship model in waves. This method is to simulate the wave environment directly in a wave-making pool and conduct a self-propulsion test of a ship model in waves. The propeller speed and torque with and without energy-saving devices are obtained, thereby obtaining the power required for propulsion. The effect of the energy-saving device is judged by the power difference.

[0008] Disadvantages: Due to the influence of wave quality and ship model motion on force measurement accuracy, the uncertainty of evaluating the effectiveness of energy-saving devices directly in waves is large, often exceeding 10%. While the energy-saving effect of existing energy-saving devices is typically around 5%, highly detailed and repetitive testing is required to reliably determine the true energy-saving effect of energy-saving devices in waves. Furthermore, conducting self-propelled model tests directly in waves with energy-saving devices is expensive, requiring a series of self-propelled model tests in different regular waves. Each wave test requires a considerable wait time for the water to calm before the next test can be conducted. Therefore, while the self-propelled model test method in waves is more reliable than CFD numerical simulation and is the only publicly available method for evaluating the energy-saving effect of energy-saving devices in waves with engineering feasibility, it is still limited by low test accuracy, poor result reliability, and long test cycles, and requires further refinement and improvement. Summary of the Invention

[0009] In order to solve the above technical problems, the present invention provides a method for evaluating the energy-saving effect of an energy-saving device in waves. The method replaces the currently commonly used self-propulsion method in waves with a load self-propulsion method in still water. Under more controllable test conditions, the energy-saving effect of the energy-saving device in waves can be evaluated more accurately and efficiently.

[0010] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0011] The present invention provides a method for evaluating the energy-saving effect of an energy-saving device in waves, wherein a test evaluation is performed using a ship model and the energy-saving device, wherein the ship model is equipped with a self-propulsion power system, and the method comprises the following steps:

[0012] Determine the speed V to be evaluated s and sea conditions to be assessed;

[0013] Speed ​​to be evaluated V s Under these conditions, the resistance of the ship model in still water was measured with and without the energy-saving device.

[0014] The rapid self-propulsion test in still water was carried out on ships with and without energy-saving devices to obtain the speed V to be evaluated. s The following two correspond to the propeller speed and propeller torque of the actual ship's self-propulsion point;

[0015] Conduct wave resistance increase model tests on ships with and without energy-saving devices to obtain the average wave resistance increase of the two under the sea conditions to be evaluated;

[0016] Speed ​​to be evaluated V s Under the conditions of wave resistance increase, the corresponding average wave resistance load is applied to the ship model with and without energy-saving devices, and a rapid self-propulsion test in still water is carried out to obtain the propeller speed and propeller torque corresponding to the real ship's self-propulsion point under the wave resistance increase effect.

[0017] Based on the above experimental results, the power difference between the ship model with and without energy-saving devices was calculated to obtain an evaluation of the energy-saving effect.

[0018] Preferably, the wave resistance increase model test includes the following steps: simulating irregular waves under the sea conditions to be evaluated in a water tank; measuring the forces acting on the ship model during the process of moving at the speed to be evaluated; and taking the difference between the average value of the forces when acting and the resistance of the ship model in still water as the average wave resistance increase of the ship in the sea conditions to be evaluated.

[0019] Preferably, the sea condition to be assessed is determined by the significant wave height Hs and the wave average zero-crossing period Tz.

[0020] Preferably, the load is applied via a trailer and a pulley mechanism fixed to the trailer.

[0021] Furthermore, the trailer is connected to the ship model via an airworthiness instrument mechanism.

[0022] Furthermore, the airworthiness instrument mechanism is a four-degree-of-freedom airworthiness instrument, and the ship model can move freely in four degrees of freedom: surge, heave, pitch, and roll through the airworthiness instrument mechanism.

[0023] Furthermore, the airworthiness instrument mechanism is connected to the ship model via a single-component force balance.

[0024] Preferably, the self-propulsion power system includes a servo motor, a propeller and a self-propulsion power meter. The servo motor drives the propeller to rotate at a specified speed. The self-propulsion power is arranged between the servo motor and the propeller to measure the propeller torque.

[0025] Preferably, the ship model with the energy-saving device is at a speed V to be evaluated. s The expression of power during sailing is:

[0026] P W1 =2πλ 3 (n W1 Q W1 -n SW1 Q SW1 );

[0027] Ship model without energy-saving device to be evaluated for speed V s The expression of power during sailing is:

[0028] P W0 =2πλ 3 (n W0 Q W0 -n SW0 Q SW0 );

[0029] Where λ is the scale ratio selected for the model test, that is, the ratio of the length of the actual ship to the length of the ship model; n w1 n is the propeller speed of the ship model with energy-saving device when it is self-propelled when load is applied; sw1 n is the propeller speed of the ship model with energy-saving device in still water when it is self-propelled; w0 n is the propeller speed of the ship model without energy-saving device when the load is applied; sw0 Q is the propeller speed of the ship model without energy-saving device when it is self-propelled in still water; w1 Q is the propeller torque of the ship model with energy-saving device when the load is applied; sw1 Q is the propeller torque of the ship model with energy-saving device in still water when it is self-propelled; w0 Q is the propeller torque of the ship model without energy-saving device when the load is applied; sw0 It is the propeller torque of the ship model without energy-saving device when it is self-propelled in still water.

[0030] Furthermore, the ship model with the energy-saving device and without the energy-saving device at the speed to be evaluated V s The power difference during down sailing is obtained from the following formula:

[0031] P ES =P W0 -P W1 .

[0032] The present invention provides a method for evaluating the energy-saving effect of an energy-saving device in waves, which has the following advantages:

[0033] The proposed method for evaluating the energy-saving effect of energy-saving devices in waves addresses the high uncertainty and high cost associated with current self-propulsion model tests conducted directly in waves. By utilizing a load-bearing self-propulsion method, the energy-saving effect of energy-saving devices in waves can be more accurately and efficiently evaluated under more controllable test conditions. This method helps demonstrate the energy-saving effect of energy-saving devices under real-world maritime navigation conditions. Furthermore, through design optimization, the device can be optimized for different sea conditions. This not only helps ships meet stringent environmental regulations but also significantly reduces fuel costs, resulting in long-term economic benefits for shipowners. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flow chart of a method for evaluating the energy-saving effect of an energy-saving device in waves according to the present invention;

[0035] Figure 2 A schematic diagram of a load self-propulsion test method for evaluating the energy-saving effect of an energy-saving device in waves according to the present invention;

[0036] Figure 3 Schematic diagram of the load self-propulsion test data analysis method Figure 1 ;

[0037] Figure 4 Schematic diagram of the load self-propulsion test data analysis method Figure 2 ;

[0038] In the picture:

[0039] 1-Ship model; 2-Self-propulsion power system; 21-Servo motor; 22-Propeller; 23-Self-propulsion dynamometer; 3-Trailer; 4-Pulley mechanism; 5-Load counterweight; 6-Airworthiness instrument mechanism; 7-Single-component force balance. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0041] The energy-saving device of the present invention is used to evaluate the energy-saving effect in a water pool by cooperating with a ship model 1 equipped with a self-propelled power system 2. The self-propelled power system 2 includes a servo motor 21, a propeller 22 and a self-propelled power meter 23. The servo motor 21 is installed on the ship model 1 to drive the propeller 22 to rotate at a specified speed. The self-propelled power is installed between the servo motor 21 and the propeller 22 to measure the thrust and torque of the propeller 22. In this embodiment, the use of the self-propelled power system 2 is existing technology and will not be described in detail.

[0042] Reference Figure 1 , a method for evaluating the energy-saving effect of an energy-saving device in waves designed by the present invention comprises the following steps;

[0043] S1, determine the ship speed and sea conditions to be evaluated, where the sea conditions to be evaluated are determined by two parameters: significant wave height Hs and wave average zero-crossing period Tz.

[0044] S2, speed to be evaluated V sUnder the condition of the above, a resistance test in still water is carried out to obtain the resistance of the ship model 1 in still water when the ship model 1 is with and without the energy-saving device.

[0045] S3, a rapid self-propulsion test in still water is carried out on ships with and without energy-saving devices, and the speed V to be evaluated is measured by the self-propulsion power meter 23. s The following two correspond to the propeller 22 speed and propeller 22 torque at the actual ship's self-propulsion point.

[0046] S4, wave resistance increase model tests are carried out on ships with and without energy-saving devices, simulating irregular waves under the sea conditions to be evaluated in the water tank, and measuring the speed V of the ship model 1 to be evaluated. s The force during the forward movement, take the average value of the force R w The difference between the resistance of the ship model 1 in still water obtained in step S1 is used as the average wave resistance increase of the ship in the sea condition to be evaluated.

[0047] S5, speed to be evaluated V s Under the conditions of wave resistance increase effect, the corresponding average wave resistance increase load is applied to the ship model 1 with and without the energy-saving device, and a rapid self-propulsion test in still water is carried out. The propeller 22 speed and propeller 22 torque corresponding to the real ship self-propulsion point under the wave resistance increase effect are measured by the self-propulsion dynamometer 23.

[0048] Considering the high cost and low precision of conducting self-propulsion tests directly in waves, the present invention applies a load equal to the wave resistance increase to the ship model 1 through a set of pulley mechanisms 4, and conducts self-propulsion model tests in still water under this state. Figure 2 In this embodiment, the load of the ship model 1 is preferably applied by the trailer 3 and the pulley mechanism 4 fixed on the trailer 3. The ship model 1 and the trailer 3 are connected by the airworthiness instrument mechanism 6. The trailer 3 tows the ship model 1 to be evaluated for the speed V s The seaworthiness instrument mechanism 6 is a four-degree-of-freedom seaworthiness instrument. The ship model 1 is able to move freely in the four degrees of freedom of surge, heave, pitch, and roll through the seaworthiness instrument mechanism 6. The seaworthiness instrument mechanism 6 is connected to the ship model 1 via a single-component force balance 7 to measure the forces acting on the ship model 1. By placing a load counterweight 5 of corresponding weight on the pulley mechanism 4, an additional load equal to the increased wave resistance is generated on the ship model 1. The load can be applied to a specified position on the ship model 1 by externally adjusting the mechanism position.

[0049] Reference Figure 3 and Figure 4When carrying out the load self-propulsion test, it is necessary to carry out multiple tests at the same propeller 22 speed for the same speed. Based on the tests at different propeller 22 speeds n, the corresponding forced force Z measured by the single-component force balance 7 of the airworthiness instrument and the propeller 22 torque Q measured by the self-propulsion dynamometer 23 can be obtained. First, according to the forced force F corresponding to the actual ship self-propulsion point D The propeller 22 speed n corresponding to the actual ship self-propulsion point is obtained by interpolation W Then, according to the speed interpolation, the propeller 22 torque Q corresponding to the actual ship self-propulsion point is obtained. W .

[0050] S5. Based on the above experimental results, the power value increase of the ship model 1 when sailing in the loaded self-propulsion state and the still water self-propulsion state with and without the energy-saving device is predicted respectively. The difference between the two is used as the basis for evaluating the energy-saving effect of the energy-saving device in waves.

[0051] Specifically, the ship model 1 with the energy-saving device is to be evaluated at a speed V s The expression of power during sailing is:

[0052] p W1 =2πλ 3 (n W1 Q W1 -n SW1 Q SW1 );

[0053] Ship model 1 without energy-saving device to be evaluated for speed V s The expression of power during sailing is:

[0054] P W0 =2πλ 3 (n W0 Q W0 -n SW0 Q SW0 );

[0055] Where λ is the scale ratio selected for the model test, that is, the ratio of the length of the actual ship to the length of the ship model 1; n w1 n is the speed of the propeller 22 of the ship model 1 with the energy-saving device when it is self-propelled when the load is applied; sw1 is the speed of the propeller 22 of the ship model 1 with energy-saving device when it is self-propelled in still water; n w0 n is the speed of the propeller 22 of the ship model 1 when it is self-propelled without the energy-saving device when the load is applied; sw0 is the speed of the propeller 22 of the ship model 1 without energy-saving device in still water when it is self-propelled; Q w1 Q is the torque of the propeller 22 of the ship model 1 with energy-saving device when it is self-propelled when load is applied; sw1 Q is the torque of the propeller 22 of the ship model 1 with energy-saving device when it is self-propelled in still water; w0Q is the torque of the propeller 22 of the ship model 1 when it is self-propelled without the energy-saving device when the load is applied; sw0 It is the torque of the propeller 22 when the ship model 1 without energy-saving device is self-propelled in still water.

[0056] Furthermore, the ship model 1 with and without the energy-saving device at the speed to be evaluated V s The power difference during sailing is obtained from the following formula:

[0057] P ES =P W0 -P W1 .

[0058] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the present invention, and these improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for evaluating the energy-saving effect of an energy-saving device in waves, characterized in that: The test evaluation is carried out using a ship model and energy-saving devices. The ship model is equipped with a self-propulsion power system, including the following steps: Determine the speed V to be evaluated s and sea conditions to be assessed; Speed ​​to be evaluated V s Under these conditions, the resistance of the ship model in still water was measured with and without the energy-saving device. The rapid self-propulsion test in still water was carried out on ships with and without energy-saving devices to obtain the speed V to be evaluated. s The following two correspond to the propeller speed and propeller torque of the actual ship's self-propulsion point; Conduct wave resistance increase model tests on ships with and without energy-saving devices to obtain the average wave resistance increase of the two under the sea conditions to be evaluated; Speed ​​to be evaluated V s Under the conditions of wave resistance increase, the corresponding average wave resistance load is applied to the ship model with and without energy-saving devices, and a rapid self-propulsion test in still water is carried out to obtain the propeller speed and propeller torque corresponding to the real ship's self-propulsion point under the wave resistance increase effect. Based on the experimental results, the power difference between the ship model with and without energy-saving devices was calculated to obtain an evaluation of the energy-saving effect.

2. The method for evaluating the energy-saving effect of an energy-saving device in waves according to claim 1, characterized in that: The wave resistance increase model test comprises the following steps: Simulating irregular waves under the sea conditions to be evaluated in a water tank; Measure the ship model to evaluate the speed V s The forces during the forward movement; Take the average value of force R when the force is applied w The difference between the resistance of the ship model and the resistance of the ship model in still water is taken as the average wave resistance increase of the ship in the sea state to be evaluated.

3. The method for evaluating the energy-saving effect of an energy-saving device in waves according to claim 1, characterized in that: The sea condition to be evaluated is determined by the significant wave height Hs and the wave average zero-crossing period Tz.

4. The method for evaluating the energy-saving effect of an energy-saving device in waves according to claim 1, characterized in that: The load is applied via a trailer and a pulley mechanism fixed to the trailer.

5. The method for evaluating the energy-saving effect of an energy-saving device in waves according to claim 4, characterized in that: The trailer is connected to the ship model via an airworthiness instrument mechanism.

6. The method for evaluating the energy-saving effect of an energy-saving device in waves according to claim 5, characterized in that: The seaworthiness instrument mechanism is a four-degree-of-freedom seaworthiness instrument, and the ship model can freely move in four degrees of freedom: surge, heave, pitch, and roll through the seaworthiness instrument mechanism.

7. The method for evaluating the energy-saving effect of an energy-saving device in waves according to claim 5, characterized in that: The airworthiness instrument mechanism is connected to the ship model via a single-component force balance.

8. The method for evaluating the energy-saving effect of an energy-saving device in waves according to claim 1, characterized in that: The self-propulsion power system includes a servo motor, a propeller and a self-propulsion power meter. The servo motor drives the propeller to rotate at a specified speed. The self-propulsion power is set between the servo motor and the propeller to measure the propeller torque.

9. The method for evaluating the energy-saving effect of an energy-saving device in waves according to claim 1, characterized in that: The ship model with the energy-saving device is at a speed V to be evaluated s The expression of power during sailing is: P W1 =2πλ 3 (n W1 Q W1 -n SW1 Q SW1 ); Ship model without energy-saving device to be evaluated for speed V s The expression of power during sailing is: P W0 =2πλ 3 (n W0 Q W0 -n SW0 Q SW0 ); Where λ is the scale ratio selected for the model test, that is, the ratio of the length of the actual ship to the length of the ship model; n w1 n is the propeller speed of the ship model with energy-saving device when it is self-propelled when load is applied; sw1 n is the propeller speed of the ship model with energy-saving device in still water when it is self-propelled; w0 n is the propeller speed of the ship model without energy-saving device when the load is applied; sw0 Q is the propeller speed of the ship model without energy-saving device when it is self-propelled in still water; w1 Q is the propeller torque of the ship model with energy-saving device when the load is applied; sw1 Q is the propeller torque of the ship model with energy-saving device in still water when it is self-propelled; w0 Q is the propeller torque of the ship model without energy-saving device when the load is applied; sw0 It is the propeller torque of the ship model without energy-saving device when it is self-propelled in still water.

10. The method for evaluating the energy-saving effect of an energy-saving device in waves according to claim 9, characterized in that: The ship model with the energy-saving device and without the energy-saving device at the speed to be evaluated V s The power difference during down sailing is obtained from the following formula: P ES =P W0 -P W1 。

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