Four-paddle forced self-propulsion test and self-propulsion factor analysis method for conventional drainage type ship

Abstract

The invention discloses a four-paddle forced self-propulsion test and self-propulsion factor analysis method for a conventional drainage type ship, and the method comprises the steps: firstly carrying out the four-paddle forced self-propulsion test for the conventional drainage type ship, and then carrying out the four-paddle forced self-propulsion factor analysis. A four-paddle forced self-propulsion test, a double-paddle forced self-propulsion test, a double-inner-paddle forced self-propulsion test and paddle unloading idling are carried out in a conventional drainage type ship four-paddle forced self-propulsion test. And then four-propeller forced self-propulsion factor analysis is carried out on the test. The four-paddle forced self-propulsion test method is reasonable in process, and necessary test data can be provided for subsequent self-propulsion factor analysis.

Description

Technical Field

[0001] The invention belongs to the technical field of ship model tests, and in particular relates to a four-propeller forced self-propulsion test of a conventional displacement ship and a self-propulsion factor analysis method. Background Art

[0002] The forced self-propulsion test of conventional displacement ship models mainly studies two aspects of influence: one is the influence of the ship on the propeller, that is, the wake fraction; the other is the influence of the propeller on the ship, that is, the thrust reduction fraction. Compared with a single propeller, in a four-propeller propulsion system, as the number of propellers increases, the influence between the propellers becomes more obvious, and the propulsion efficiency of the propellers will also differ.

[0003] Currently, there are two main common forced self-propulsion test methods for conventional displacement ship models: the first is the ship industry standard [CB / Z 818-2019] general displacement ship model single-propeller self-propulsion test method; the second is the ship industry standard [CB / Z239-2008] conventional displacement ship model double-propeller self-propulsion test method.

[0004] For method one, the single-propeller self-propulsion test method is applied to the four-propeller self-propulsion test, and the four propellers are uniformly installed behind the ship for a forced self-propulsion test. Because the four propellers interfere with each other, and the flow fields of the inner propeller and the outer propeller are different, and the resistance increase of the inner propeller and the outer propeller are different, when performing thrust deduction analysis, the resistance increase of each propeller cannot be extracted separately, and the thrust deduction of each propeller cannot be obtained.

[0005] Regarding method 2: applying the two-propeller self-propulsion test method to the four-propeller self-propulsion test, there are several inappropriate points. First, which two propellers should be used each time among the four propellers, the two on the left, the two in the middle, or the two in between? Second, for the two propellers selected for the test, should the other two propellers be retained or removed? If retained, should they be kept stationary like an attached body, or should they rotate with the water flow?

[0006] In summary, a four-propeller forced self-propulsion test method is urgently needed to solve the above problems. Summary of the invention

[0007] Purpose of the Invention

[0008] Aiming at the problems of common forced self-propulsion test methods for conventional displacement ship models, the present invention provides a conventional displacement ship four-propeller forced self-propulsion test and a self-propulsion factor analysis method.

[0009] Inventing technical solutions

[0010] The four-propeller forced self-propulsion test method and self-propulsion factor analysis method of conventional displacement ship include two parts: test method and self-propulsion factor analysis.

[0011] Part 1, the conventional displacement ship four-propeller forced self-propulsion test method, comprises the following steps:

[0012] Step (1): Follow Figure 1 As shown, four sets of propellers 5, shaft brackets 6, propeller shafts 7, shaft sleeves 8, dynamometers 9, positioning frames 10, and motors 11 are sequentially installed on a ship model 12; the double-sided propellers and double inner propellers are simultaneously inwardly or outwardly rotated.

[0013] Step (2): Determine the ship model test speed;

[0014] Step (3): Follow Figure 2 As shown, first do a four-propeller forced self-propulsion test. Install the left propeller 1, the left inner propeller 2, the right inner propeller 3, and the right propeller 4. Select a ship model test speed, generally select 4 to 5 speeds for the test, the speed should be less than the rated speed of the motor and can provide sufficient thrust for the ship model to move forward; get a linear curve of the forced force and the speed at the same speed; the speed adjustment during the test is based on the change in the forced force; on the linear fitting curve of the forced force and the speed, find the speed at which the forced force is equal to the correction value of the friction resistance by interpolation (at this speed, there is no need to conduct a four-propeller forced self-propulsion test), this speed is the speed of the actual ship self-propulsion point.

[0015] Step (4): Follow Figure 3 As shown, a forced self-propulsion test with double-sided propellers is performed. When performing the double-sided propeller test, the left propeller 1 and the right propeller 4 are retained, and the double inner propellers are removed. The speed at this time is equal to the speed when there are four propellers, and the speed adopts the speed of the actual ship's self-propulsion point; that is, for 1 speed, only 1 speed is selected.

[0016] Step (5): Follow Figure 4 As shown, a forced self-propulsion test of the double inner propeller is performed. When performing the double inner propeller test, the left inner propeller 2 and the right inner propeller 3 are retained, and the double-sided propellers are removed. The speed at this time is equal to the speed when there are four propellers, and the speed adopts the speed of the actual ship's self-propulsion point; that is, for 1 speed, only 1 speed is selected. Steps (4) and (5) can be interchanged.

[0017] Step (6): repeat steps (3) to (5) until all the ship model test speeds in step 2 have completed the tests of steps 3 to 5;

[0018] Step (7): Follow Figure 5 As shown, the propellers are removed and the model is idle. In the dock, when the model is stationary, the four propellers are removed and the model is idle at each speed according to the speed of the real ship's self-propulsion point, and the torque is collected; because the speed difference is almost the same at the same speed, only one self-propulsion point speed is selected for idling at each speed.

[0019] The second part, the four-propeller forced self-propulsion factor analysis, includes the following steps:

[0020] Step 1: Thrust Derating Analysis

[0021] according to Figure 6 As shown, the model speed V1 is taken as an example for analysis. At this speed, the model resistance is R m1 , the friction resistance correction value is F d1 .

[0022] In the four-propeller forced self-propulsion test, 4 to 5 speeds are selected. During each test, when the speed and speed are stable, the forced force F of the ship model and the thrust T of the four propellers can be monitored. During the test, according to the change of the forced force, the speed n of the actual ship self-propulsion point is interpolated. 10 .

[0023] In the forced self-propulsion test of double-blade propeller or double-inner-blade propeller, the given speed n 10 Get the forced force and the thrust of the paddle.

[0024] Step 1.1 Dynamic balance of four propellers

[0025] according to Figure 2 As shown in the figure, during the four-propeller self-propulsion test, the ship model speed V1 and one of the speeds n are selected. 11 Take the time as an example, the speed n 11 Then, the dynamic balance of the four propellers at each rotation speed in the forced self-propulsion test of the four propellers at all ship model speeds determined in step (2) is analyzed.

[0026] The dynamic equilibrium equation satisfied is:

[0027]

[0028] in:

[0029] R m1 ---Still water resistance of the ship model at speed V1;

[0030] △R 111 --Speed ​​V1, rotation speed n 11 When , the resistance of propeller model 1 increases;

[0031] △R 211 --Speed ​​V1, rotation speed n 11 When , the resistance of propeller model 2 increases;

[0032] △R 311 --Speed ​​V1, rotation speed n 11 When , the resistance of propeller model 3 increases;

[0033] △R 411 --Speed ​​V1, rotation speed n 11 When , the resistance of propeller model 4 increases;

[0034] T 111----Speed ​​V1, rotation speed n 11 When , the thrust generated by propeller model 1;

[0035] T 211 ----Speed ​​V1, rotation speed n 11 When , the thrust generated by propeller model 2;

[0036] T 311 ----Speed ​​V1, rotation speed n 11 When , the thrust generated by propeller model 3;

[0037] T 411 ----Speed ​​V1, rotation speed n 11 When , the thrust generated by the propeller model 4;

[0038] F 11 ----Speed ​​V1, rotation speed n 11 When, force.

[0039] The four propellers are installed symmetrically.

[0040] △R1=△R4,△R2=△R 3。

[0041] Step 1.2 Dynamic balance with double-sided paddles

[0042] according to Figure 3 As shown in the figure, during the double-sided propeller self-propulsion test, the ship model speed V1 and the actual ship self-propulsion point speed n 10 When , the dynamic equilibrium equation satisfied is:

[0043]

[0044] in:

[0045] R m1 ------Still water resistance of the ship model at speed V1;

[0046] △R 110 --Speed ​​V1, rotation speed n 10 When , the resistance of propeller model 1 increases;

[0047] △R 410 --Speed ​​V1, rotation speed n 10 When , the resistance of propeller model 4 increases;

[0048] T 110 ----Speed ​​V1, rotation speed n 10 When , the thrust generated by propeller model 1;

[0049] T 410 ----Speed ​​V1, rotation speed n 10 When , the thrust generated by the propeller model 4;

[0050] F 101 ----Speed ​​V1, rotation speed n 10 When, force.

[0051] The double-sided propeller is installed symmetrically.

[0052] △R 110 =△R 410。

[0053] According to formula (2), the thrust reduction of the two side propellers at speed V1 can be calculated:

[0054]

[0055] Then we can get the thrust reduction fraction of the two side propellers,

[0056]

[0057] Then, the dynamic balance of the double-sided propeller at the rotation speed of the real ship's self-propulsion point at all ship model speeds determined in step (2) is analyzed.

[0058] Step 1.3 Dynamic balance of double inner propellers

[0059] according to Figure 4 As shown in the figure, the dynamic balance equation satisfied during the double inner propeller self-propulsion test is:

[0060]

[0061] in:

[0062] R m1 ---Still water resistance of the ship model at speed V1;

[0063] △R 210 --Speed ​​V1, rotation speed n 10 When , the resistance of propeller model 2 increases;

[0064] △R 310 --Speed ​​V1, rotation speed n 10 When , the resistance of propeller model 3 increases;

[0065] T 210 ----Speed ​​V1, rotation speed n 10 When , the thrust generated by propeller model 2;

[0066] T 310 ----Speed ​​V1, rotation speed n 10 When , the thrust generated by propeller model 3;

[0067] F 102 -----Speed ​​V1, rotation speed n 10 When, force.

[0068] The double inner propellers are installed symmetrically.

[0069] △R 210 =△R 310。

[0070] According to formula (3), the thrust reduction of the two inner propellers at speed V1 can be calculated:

[0071]

[0072] Then we can get the thrust reduction fraction of the two side propellers,

[0073]

[0074] Then, the dynamic balance of the twin inner propellers at the rotational speed of the actual ship's self-propulsion point at all ship model speeds determined in step (2) is analyzed.

[0075] Step 2: Wake Fraction Analysis

[0076] according to Figure 7 As shown, the model speed V1 is taken as an example for analysis. At this speed, the model resistance is R m1 , the friction resistance correction value is F d1 .

[0077] In the four-propeller forced self-propulsion test, 4 to 5 speeds are selected. During each test, when the speed and speed are stable, the forced force F of the ship model and the thrust T of the four propellers can be monitored. During the test, according to the change of the forced force, the speed n of the actual ship self-propulsion point is interpolated. 10 .

[0078] In the forced self-propulsion test of double-blade propeller or double-inner-blade propeller, the given speed n 10 Get the forced force and the thrust of the paddle.

[0079] Step 2.1 Thrust coefficient

[0080] At speed V1, the thrust coefficients of the four propellers are calculated using the thrust of the double-sided propeller and the double inner propeller at the actual ship's self-propulsion point speed.

[0081]

[0082] in:

[0083] ρ---density of fresh water at 14℃, 999.1kg / m^3;

[0084] n---propeller speed, r / s;

[0085] D---propeller diameter, m.

[0086] Step 2.2 Open water data

[0087] According to the equal thrust method, The corresponding advance coefficient (J) can be read from the open water curve of the propeller. 110 , J 210 , J 310 , J 410 ).

[0088] Step 2.3 Wake fraction

[0089] According to the obtained advance speed coefficient, the advance speed and wake fraction of the four propeller modes at speed V1 can be obtained respectively using the empirical formula.

[0090] V Ai10 =J i10 n 10 D m， (9)

[0091]

[0092] Then calculate the thrust coefficients of the four propellers at the rotational speed of the real ship's self-propulsion point at all ship model speeds determined in step (2).

[0093] Step 3: Analyze the efficiency of the process

[0094] according to Figure 8 As shown, the model speed V1 is taken as an example for analysis. At this speed, the model resistance is R m1 , the friction resistance correction value is F d1 .

[0095] In the four-propeller forced self-propulsion test, 4 to 5 speeds are selected. During each test, when the speed and speed are stable, the forced force F of the ship model, the thrust T of the four propellers, and the torque Q of the four propellers can be monitored. During the test, according to the change of the forced force, the speed n of the actual ship self-propulsion point is interpolated. 10 .

[0096] In the forced self-propulsion test of double-blade propeller or double-inner-blade propeller, the given speed n 10 Get the propeller torque, Q 110 , Q 210 , Q 310 , Q 410 .

[0097] In the dock, when the model is stationary, remove the four propellers and rotate at a speed n. 10 Run idle, collect torque, and get the torque of the four shafts, △Q 110 , △Q 210 , △Q 310 , △Q 410 .

[0098] Step 3.1 Paddle power

[0099] At speed V1, the double-sided propeller and the double inner propeller are used to rotate at the actual ship self-propulsion point. 10 Self-propulsion data; when the model is stationary, according to the speed n 10 Unload the propellers and run them idle to get the torque of the shaft. At this time, the power received by each propeller is:

[0100] P Di0 =2×π×n 10 ×(Q i10 -ΔQ i10 ), i=1,2,3,4 (11)

[0101] Step 3.2 Effective power of the boat

[0102] At speed V1, the model resistance is R m1 , the actual ship self-propulsion point speed is n 10 At this time, the four-propeller self-propulsion force is approximately equal to the friction resistance correction value F d1 At this time, the effective power of the ship is:

[0103] P E =(R m1 -F d1 )×V1 (12)

[0104] Step 3.3 Overall propulsion efficiency

[0105] At speed V1, the total propulsion efficiency of the transmission system can be obtained based on the power received by the propeller and the effective power of the ship.

[0106] η D =P E / (P D110 +P D210 +P D310 +P D410 ) (13)

[0107] Then, the propulsion efficiency at the rotational speed of the actual ship's self-propulsion point at all ship model speeds determined in step (2) is analyzed.

[0108] The advantages of the present invention are as follows: 1) The four-propeller forced self-propulsion test method has reasonable procedures and can provide necessary test data for subsequent self-propulsion factor analysis; 2) The four-propeller forced self-propulsion factor analysis process is simple and easy to understand, and through the analysis process, the thrust reduction, wake fraction and propulsion efficiency can be quickly obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0109] Attached Figure 1 It is a schematic diagram of the internal instruments and accessories of the ship model.

[0110] Figure 2This is a schematic diagram of a four-propeller self-propelled craft.

[0111] Figure 3 This is a schematic diagram of double-sided propeller self-propulsion.

[0112] Figure 4 This is a schematic diagram of a dual inner propeller self-propulsion.

[0113] Figure 5 This is a schematic diagram of idling with unloaded propellers.

[0114] Figure 6 This is a diagram showing thrust reduction data at speed V1.

[0115] Figure 7 It is a schematic diagram of wake fraction data at speed V1.

[0116] Figure 8 This is a diagram of propulsion efficiency data at speed V1.

[0117] Fig. 9 This is the relationship between the coercive force and the rotation speed when the speed is 1.1m / s. DETAILED DESCRIPTION

[0118] The present invention is achieved through the following technical solutions.

[0119] Conventional displacement ship four-propeller forced self-propulsion test and self-propulsion factor analysis method, including conventional displacement ship four-propeller forced self-propulsion test and four-propeller forced self-propulsion factor analysis.

[0120] Preparation before the test. Attention should be paid to the following points during the test preparation stage:

[0121] 1) The direction of propeller rotation. Generally, the four propellers rotate symmetrically and are outward-rotating propellers; 2) Install a dynamometer. Generally, one propeller is installed with a dynamometer. When selecting a dynamometer, its range should take into account the propeller thrust and propeller torque; 3) Install the motor. The motor mainly provides rotational power to the propeller. When selecting a motor, the main consideration is whether its maximum speed meets the test requirements; 4) The internal friction of the propeller shaft. Before the ship model test, the propeller shaft is powered on for debugging. The internal friction of the propeller shaft should preferably be within 100g.

[0122] The conventional displacement ship four-propeller forced self-propulsion test method comprises the following steps:

[0123] Step 1: Follow Figure 1 As shown, four sets of propellers 5, shaft brackets 6, propeller shafts 7, shaft sleeves 8, dynamometers 9, positioning brackets 10, and motors 11 are sequentially installed on the ship model 12;

[0124] Step 2: Follow Figure 2As shown, first do a forced self-propulsion test of four propellers. Install the left propeller 1, the left inner propeller 2, the right inner propeller 3, and the right propeller 4. The ship model test speed selected for the first time is 1.1m / s. The corresponding full appendage resistance of the ship model at this speed is 38N, and the friction resistance correction value is 0.404kg. As shown in Table 1, the thrust and torque of the propellers monitored in the four-propeller self-propulsion test. Four speeds were selected, 483r / min, 496r / min, 510r / min, and 523r / min, and the corresponding forced forces of these four speeds are 1.225kg, 0.891kg, 0.546kg, and 0.193kg, respectively.

[0125] like Fig. 9 As shown in the figure, on the linear fitting curve of the forced force and the speed, the speed of 515r / min when the forced force is equal to the correction value of the friction resistance is found by interpolation. This speed is the speed of the actual ship's self-propulsion point.

[0126] Table 1 Four-propeller test data

[0127]

[0128] Step 3: Follow Figure 3 As shown, a forced self-propulsion test of double-sided propellers is performed. When performing the double-sided propeller test, the left propeller 1 and the right propeller 4 are retained, and the double inner propellers are removed. The speed at this time is 1.1m / s and the rotation speed is 515r / min.

[0129] Table 2 Double-sided paddle test data

[0130]

[0131] Step 4: Follow Figure 4 As shown, a forced self-propulsion test of double inner propellers is performed. When performing the double inner propeller test, the left inner propeller 2 and the right inner propeller 3 are retained, and the double-sided propellers are removed. The speed at this time is 1.1m / s and the rotation speed is 515r / min.

[0132] Table 3 Double inner propeller test data

[0133]

[0134]

[0135] Step 5: Follow Figure 5 As shown, the propeller is unloaded and idling. The speed at this time is 0m / s and the rotation speed is 515r / min.

[0136] Table 4 Unloading idling test data

[0137]

[0138] The four-propeller self-propulsion factor analysis method comprises the following steps:

[0139] Step 1: Thrust Derating Analysis

[0140] As shown in Table 1, taking the ship model speed of 1.1 m / s as an example, the total appendage resistance of the ship model is 38.4 N and the friction resistance correction value is 0.404 kg.

[0141] In the four-propeller forced self-propulsion test, four speeds were selected, namely 483r / min, 496r / min, 510r / min, and 523r / min. According to the change of the forced force, the speed of the actual ship self-propulsion point was interpolated to be 515r / min.

[0142] In the forced self-propulsion test of double-sided propellers or double inner-sided propellers, the given speed is 515r / min to obtain the forced force and the propeller thrust and torque.

[0143] Step 1.1 Dynamic balance with double-sided paddles

[0144] As shown in Table 2, during the double-sided propeller self-propulsion test, when the ship model speed is 1.1m / s and the rotation speed is 515r / min, the dynamic balance equation satisfied is:

[0145]

[0146] in:

[0147] △R 110 --When the speed is 1.1m / s and the rotation speed is 515r / min, the resistance increase of propeller model 1;

[0148] △R 410 --When the speed is 1.1m / s and the rotation speed is 515r / min, the resistance increase of propeller model 4;

[0149] The double-sided propellers are installed symmetrically, so the thrust of the two side propellers is reduced.

[0150] △R 110 =△R 410 =0.439N.

[0151] The thrust reduction fractions of the two side propellers at a speed of 1.1m / s can be calculated.

[0152]

[0153] Step 1.2 Dynamic balance of double inner propellers

[0154] As shown in Table 3, the dynamic balance equation satisfied during the double inner propeller self-propulsion test is:

[0155]

[0156] in:

[0157] △R 210 --When the speed is 1.1m / s and the rotation speed is 515r / min, the resistance increase of propeller model 2;

[0158] △R 310 —The resistance increase of propeller model 3 at speed 1.1m / s and rotation speed 515r / min;

[0159] The double inner propellers are installed symmetrically.

[0160] △R 210 =△R 310 =0.638N

[0161] The thrust reduction fraction of the two inner propellers at a speed of 1.1m / s can be calculated.

[0162]

[0163] Step 2: Wake Fraction Analysis

[0164] According to the test data in Tables 2 and 3, taking the ship model speed of 1.1 m / s as an example, the total appendage resistance of the ship model is 38.4 N and the friction resistance correction value is 0.404 kg.

[0165] In the four-propeller forced self-propulsion test, four speeds were selected, namely 483r / min, 496r / min, 510r / min, and 523r / min. According to the change of the forced force, the speed of the actual ship self-propulsion point was interpolated to be 515r / min.

[0166] The ship model speed was selected as 1.1 m / s. In the forced self-propulsion test with double-sided propellers or double inner-sided propellers, the rotation speed was given as 515 r / min to obtain the forced force and propeller thrust.

[0167] Step 2.1 Thrust coefficient

[0168] At a speed of 1.1 m / s, the thrust coefficients of the four propellers were calculated using the thrust of the double-sided propellers and the double inner propellers at a speed of 515 r / min.

[0169]

[0170] Step 2.2 Open water data

[0171] According to the equal thrust method, The corresponding advance coefficient (J) can be read from the open water curve of the propeller. 110 , J 210 , J 310 , J 410 )=(1.004, 1.010, 1.008, 1.006).

[0172] Step 2.3 Wake fraction

[0173] According to the found advance speed coefficient, the advance speed and wake fraction of the four propeller modes at a speed of 1.1m / s can be obtained respectively using the empirical formula.

[0174] V A110 =J 110 n 10 D m =1.004×(515 / 60)×0.12=1.035,

[0175] V A210 =J 210 n 10 D m =1.010×(515 / 60)×0.12=1.041,

[0176] V A310 =J 310 n 10 D m =1.008×(515 / 60)×0.12=1.039,

[0177] V A410 =J 410 n 10 D m =1.006×(515 / 60)×0.12=1.037,

[0178]

[0179] Step 3: Analyze the efficiency of the process

[0180] According to the test data in Tables 2 to 4, taking the ship model speed of 1.1 m / s as an example, the total appendage resistance of the ship model is 38.4 N and the friction resistance correction value is 0.404 kg.

[0181] In the four-propeller forced self-propulsion test, four speeds were selected, namely 483r / min, 496r / min, 510r / min, and 523r / min. According to the change of the forced force, the speed of the actual ship self-propulsion point was interpolated to be 515r / min.

[0182] The ship model speed was selected as 1.1 m / s. In the forced self-propulsion test with double-sided propellers or double inner-sided propellers, the propeller torque was obtained at a given speed of 515 r / min, which were 0.025 kg.m, 0.026 kg.m, 0.028 kg.m, and 0.027 kg.m.

[0183] In the dock, when the model is stationary, the four propellers are removed and the model is allowed to idle at a speed of 515 r / min. The torque is collected to obtain the torques of the four shafts: 0.000 kg.m, 0.001 kg.m, 0.001 kg.m, and 0.002 kg.m.

[0184] Step 3.1 Paddle power

[0185] At this time, the power received by each propeller is:

[0186] P D10 =2×π×n 10 ×(Q 110 -ΔQ 110 )

[0187] =2×3.14×(515 / 60)×(0.025-0.000)×9.81

[0188] =13.248w

[0189] P D20 =2×π×n 10 ×(Q 210 -ΔQ 210 )

[0190] =2×3.14×(515 / 60)×(0.026-0.001)×9.81

[0191] =13.429w

[0192] P D30 =2×π×n 10 ×(Q 310 -ΔQ 310 )

[0193] =2×3.14×(515 / 60)×(0.028-0.001)×9.81

[0194] =14.375w

[0195] P D40 =2×π×n 10 ×(Q 410 -ΔQ 410 )

[0196] =2×3.14×(515 / 60)×(0.027-0.002)×9.81

[0197] =13.373w

[0198] Step 3.2 Effective power of the boat

[0199] At a speed of 1.1m / s, the model resistance is 38.4N, and the actual ship self-propulsion point speed is 515r / min. At this time, the four-propeller self-propulsion force is approximately equal to the friction resistance correction value of 0.404kg. At this time, the effective power of the ship is:

[0200] P E =(R m1 -F d1 )×V1

[0201] =(38.4-0.404×9.81)×1.1

[0202] =38.5w

[0203] Step 3.3 Overall propulsion efficiency

[0204] At a speed of 1.1 m / s, the total propulsion efficiency of the transmission system can be obtained based on the power received by the propeller and the effective power of the ship.

[0205] η D =P E / (P D110 +P D210 +P D310 +P D410 )

[0206] =38.5 / (13.248+13.429+14.375+13.373)

[0207] =0.707

[0208] The protection scope of the present invention is not limited to the above-mentioned embodiments. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the scope of the present invention. If these changes and modifications fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include these changes and modifications.

Claims

1. A four-propeller forced self-propulsion test and self-propulsion factor analysis method for a conventional displacement ship, characterized in that: It includes the four-propeller forced self-propulsion test of conventional displacement ship and the four-propeller forced self-propulsion factor analysis, among which: The four-propeller forced self-propulsion test of a conventional displacement ship includes the following steps: (1) Determine the ship model test speed; (2) selecting a ship model test speed in step (1), and selecting several rotation speeds to perform a forced self-propulsion test of the four-propeller, and obtaining the actual ship self-propulsion point rotation speed under the ship model test speed; (3) Perform a forced self-propulsion test of the double-sided propeller and the double-inner propeller, the speed adopts the ship model test speed selected in step (2), and the rotation speed adopts the rotation speed of the actual ship self-propulsion point under the ship model test speed; (4) Repeat steps (2) to (3) until all ship model test speed tests in step (1) are completed; (5) performing idling operation with the propeller removed according to the actual ship self-propulsion point speed at each ship model test speed determined in step (2) to collect torque; After the four-propeller forced self-propulsion test of conventional displacement ship is completed, the four-propeller forced self-propulsion factor analysis is carried out. The four-propeller forced self-propulsion factor analysis includes thrust reduction analysis, wake fraction analysis and propulsion efficiency analysis.

2. The conventional displacement ship four-propeller forced self-propulsion test and self-propulsion factor analysis method according to claim 1, characterized in that: In step (1), a linear fitting curve of the forced force and the rotational speed at the ship model test speed is obtained through a forced self-propulsion test of four propellers, and then the rotational speed at which the forced force is equal to the friction resistance correction value is found on the linear fitting curve. This rotational speed is the rotational speed of the actual ship self-propulsion point at the ship model test speed.

3. The conventional displacement ship four-propeller forced self-propulsion test and self-propulsion factor analysis method according to claim 1, characterized in that: The thrust derating analysis includes the following steps: Step 1.1 Dynamic balance of four propellers: In the forced self-propulsion test of the four propellers, dynamic balance analysis is performed on each ship model test speed in step (1) and each rotation speed under the corresponding ship model test speed; Step 1.2 Dynamic balance of double-sided propeller: In the forced self-propulsion test of the double-sided propeller, a dynamic balance analysis is performed on each ship model test speed in step (1) and the rotation speed of the actual ship self-propulsion point under the corresponding ship model test speed; Step 1.3 Dynamic balance of twin inner propellers: In the forced self-propulsion test of twin inner propellers, a dynamic balance analysis is performed on each ship model test speed in step (1) and the rotation speed of the actual ship self-propulsion point at the corresponding ship model test speed.

4. The conventional displacement ship four-propeller forced self-propulsion test and self-propulsion factor analysis method according to claim 1, characterized in that: The wake fraction analysis includes the following steps: Step 2.1 Thrust coefficient: Calculate the thrust coefficients of the four propellers by using the thrust of the double propellers and the double inner propellers at the respective ship model test speeds in step (1) and the actual ship self-propulsion point rotation speed under the corresponding ship model test speeds; Step 2.2 Read the corresponding advance coefficient from the open water curve of the propeller; Step 2.3 obtains the advance speed and wake fraction of the four propeller models at each ship model test speed in step (1) according to the advance speed coefficient.

5. The conventional displacement ship four-propeller forced self-propulsion test and self-propulsion factor analysis method according to claim 1, characterized in that: The propulsion efficiency analysis includes the following steps: Step 3.1 propeller power: Calculate the power received by each propeller according to the ship model test speed in step (1) and the actual ship self-propulsion point speed under the corresponding ship model test speed, and the torque of the shaft obtained when the propeller is unloaded and idling; Step 3.2 Effective power of the ship: Calculate the effective power of the ship according to the ship model test speeds in step (1), the model resistance at the actual ship self-propulsion point speed under the corresponding ship model test speeds, and the correction value of friction resistance. The correction value of friction resistance is approximately equal to the compulsory force of four-propeller self-propulsion; Step 3.3 Total propulsion efficiency: The total propulsion efficiency of the transmission system is obtained based on the power received by the propeller and the effective power of the ship.

6. The conventional displacement ship four-propeller forced self-propulsion test and self-propulsion factor analysis method according to claim 1, characterized in that: Before the forced self-propulsion test of a conventional displacement ship with four propellers, four sets of propellers (5), shaft brackets (6), propeller shafts (7), shaft sleeves (8), dynamometers (9), positioning frames (10), and motors (11) are sequentially installed on a ship model (12); the double-sided propellers and double inner propellers are simultaneously rotated inwardly or outwardly.

7. The conventional displacement ship four-propeller forced self-propulsion test and self-propulsion factor analysis method according to claim 1, characterized in that: The speed selected for the test in step (2) should be less than the rated speed of the motor and be able to provide sufficient thrust for the ship model to move forward.

8. The conventional displacement ship four-propeller forced self-propulsion test and self-propulsion factor analysis method according to claim 1, characterized in that: In step (2), 4 to 5 rotational speeds are selected for each ship model test speed.

9. The conventional displacement ship four-propeller forced self-propulsion test and self-propulsion factor analysis method according to claim 3, characterized in that: The dynamic equilibrium equation satisfied by the four propellers in step 1.1 is: R m1 +ΔR 111 +ΔR 211 +ΔR 311 +ΔR 411 =T 111 +T 211 +T 311 +T 411 +F 11 (1) Where: R m1 is the static water resistance of the ship model when the ship model speed is V1; △R 111 The speed of the ship model is V1 and the rotation speed is n 11 When the resistance of propeller model 1 (1) increases, △R 211 is the ship model speed V1, the rotation speed n 11 When , the resistance of propeller model 2 (2) increases; △R 311 is the ship model speed V1, the rotation speed n 11 When , the resistance increase of propeller model three (3) is: △R 411 is the ship model speed V1, the rotation speed n 11 When the resistance of propeller model 4 (4) increases, T 111 is the speed V1, the rotation speed n 11 The thrust generated by propeller model 1 (1) when T 211 is the ship model speed V1, the rotation speed n 11 The thrust generated by propeller model 2 (2) when T 311 is the ship model speed V1, the rotation speed n 11 The thrust generated by propeller mode three (3) when T 411 is the ship model speed V1, the rotation speed n 11 The thrust generated by propeller model four (4) when 11 is the ship model speed V1, the rotation speed n 11 The coercive force of time; The four propellers are installed symmetrically. △R1=△R4,△R2=△R3.

10. The conventional displacement ship four-propeller forced self-propulsion test and self-propulsion factor analysis method according to claim 3, characterized in that: The dynamic balance equation satisfied by the double-sided propeller in step 1.2 is: Where: R m1 is the static water resistance of the ship model at the ship model speed V1; △R 110 is the ship model speed V1, the actual ship self-propulsion point speed n 10 When the resistance of propeller model 1 (1) increases, △R 410 is the ship model speed V1, the rotation speed n 10 When the resistance of propeller model 4 (4) increases, T 110 is the ship model speed V1, the actual ship self-propulsion point speed n 10 The thrust generated by propeller model 1 (1) when T 410 is the ship model speed V1, the actual ship self-propulsion point speed n 10 The thrust generated by propeller model four (4) when 101 is the ship model speed V1, the actual ship self-propulsion point speed n 10 The coercive force of time; The double-sided propeller is installed symmetrically. △R 110 =△R 410。 According to formula (2), the thrust reduction of the two side propellers at the ship model speed V1 can be calculated: Then we can get the thrust reduction fraction of the two side propellers,

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