CN110909420B - Ship propulsion shafting alignment iterative calculation method considering bearing factors - Google Patents
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Abstract
The invention discloses a ship propulsion shafting alignment iterative calculation method considering bearing factors, which comprises the following steps: s1, discretizing the shaft section and giving an initial position value Z of the equivalent fulcrum of the tail bearing (0) (ii) a S2, centering and calculating a shaft system by using a three-bending moment method to obtain a journal corner at the tail bearing; s3, substituting a journal rotation angle into a calculation formula by using a tail bearing equivalent fulcrum calculation formula to obtain a new equivalent fulcrum position value; s4, when the new equivalent fulcrum position value does not meet the convergence condition, the Z is set (k) And Z (k‑1) The average value of the two is used as a new equivalent fulcrum position value, the basis of calculating the journal rotation angle at the tail bearing in the next time is used, and the step S2 is executed again; s5, when the new equivalent fulcrum position value meets the convergence condition, connecting Z (k) And substituting the three moments of bending method to calculate to obtain a final centering calculation result. The ship propulsion shafting alignment iterative calculation method provided by the invention can accurately determine the equivalent fulcrum position value of the tail bearing.
Description
Technical Field
The invention relates to the technical field of shafting alignment, in particular to a ship propulsion shafting alignment iterative calculation method considering bearing factors.
Background
The centering of the propulsion shafting is an important component for shafting design and installation, the quality of shafting centering is good and bad, and the centering has important influence on guaranteeing the normal operation of the shafting and a main machine and reducing the vibration of a ship body. Production practices prove that shaft systems with poor centering quality can cause rapid wear and even burnout of a tail shaft tube bearing when in operation, abnormal wear of a tail pipe sealing element causes leakage, arm distance difference of a main engine crankshaft exceeds an allowable range, normal meshing of a reduction gear and normal operation of the bearing are damaged, and hull vibration is caused.
The liner bearing support model is a focus of attention because of the large loads borne by the liner bearing near the propeller due to the cantilever action of the propeller. In the centering calculation, the equivalent fulcrum position of the water lubrication type tail pipe rear bearing is generally selected by referring to the regulations of the iron-pear-wood bearing, the fulcrum position of the tail pipe front bearing is generally taken as the midpoint, and the processing method is reasonable or not and deserves deep analysis.
Three methods are commonly used for shafting alignment calculation: finite element method, transfer matrix method, and triple moment method. With the application of a plurality of new materials, the elastic modulus of the lining of the bearing is changed, and meanwhile, the aspect ratio of the bearing is continuously increased and the like due to the trend that modern ships continuously develop towards large tonnage, so that the school environment is more complicated. However, the existing shafting alignment method such as the triple bending moment method does not take the development changes of the ship bearing into account, while the ANSYS finite element method takes the changes of the factors into account, but the calculation process is complex, and the modeling, grid dividing and other processes depend on the experience of a user, so that the repeatability of the method is poor, and whether the existing alignment result is accurate or not is questionable. It is therefore necessary to find new pivot point calculation methods.
Disclosure of Invention
The invention mainly aims to provide a ship propulsion shafting alignment iterative calculation method considering bearing factors, and aims to accurately determine an equivalent fulcrum position value of a tail bearing.
In order to achieve the aim, the invention provides a ship propulsion shafting alignment iterative calculation method considering bearing factors, which comprises the following steps:
s1, discretizing the shaft section and giving an initial position value Z of the equivalent fulcrum of the tail bearing (0) ；
S2, performing centering calculation on the shafting by using a three-bending moment method to obtain a journal rotation angle at the tail bearing;
s3, substituting the journal rotation angle obtained in the previous step by using a tail bearing equivalent fulcrum calculation formula to calculate and obtain a new equivalent fulcrum position value Z (k) K is the number of iterations;
s4, when calculating to obtain a new equivalent fulcrum position value Z (k) Equivalent fulcrum position value Z before iteration (k-1) Large difference value betweenWhen the difference is preset, Z is set (k) And Z (k-1) The average value of the two is used as a new equivalent fulcrum position value, the basis of calculating the journal rotation angle at the tail bearing in the next time is used, and the step S2 is executed again;
s5, when calculating to obtain a new equivalent fulcrum position value Z (k) Equivalent fulcrum position value Z before iteration (k-1) When the difference between Z and Z is less than or equal to the preset difference, namely the iteration convergence meets the preset condition, Z is adjusted (k) And substituting the three moments of bending method to calculate to obtain a final centering calculation result.
Preferably, in step S1, Z (0) The value range of (1/4-1/3) L, wherein L is the length of the tail bearing.
Preferably, in step S3, a new equivalent fulcrum position value Z is calculated (k) And then, calculating according to the rotation angle, the elastic modulus and the length-diameter ratio of the shaft neck.
Preferably, in the calculation formula of the equivalent fulcrum of the tail bearing, the equivalent fulcrum position of the tail bearing when the length-diameter ratio of the bearing, the journal rotation angle and the elastic modulus of the lining are different is calculated by using a finite element method, and then, a fulcrum coefficient is obtained by fitting by using a linear regression analysis method.
Preferably, in step S3, the relationship between the elastic modulus, the aspect ratio and the corner of the tail bearing and the equivalent fulcrum position is as follows:
Z (k) ＝a(L/D) b (θ (k) ) c E d ；
in the formula: z (k) Calculating the equivalent fulcrum position of the tail bearing for the kth iteration; L/D is the length-diameter ratio of the tail bearing; theta (k) Calculating the journal rotation angle for the kth iteration; e is the elastic modulus of the liner of the tail bearing; a. b, c and d are fulcrum coefficients, and the fulcrum coefficients are obtained through a linear regression analysis method and simulation data fitting calculation.
Preferably, in step S5, the criterion of iterative convergence is:
in the formula: and b is an iteration convergence coefficient.
Preferably, in step S5, the final centering calculation result includes: corner, deflection, bending moment, bending stress, corner and bearing reaction force.
Compared with the prior art, the ship propulsion shafting alignment iterative calculation method considering the bearing factors has the following advantages:
1. by adopting a loop iteration centering method, the problem that the position of a subjectively assumed tail bearing fulcrum is inconsistent with the state of an actual shafting during centering calculation is solved in an iteration calculation mode;
2. the method comprises the steps of providing an equivalent fulcrum model considering bearing factors and a calculation method thereof, considering the bearing factors on the basis of the traditional equivalent fulcrum model, analyzing the relation between the length-diameter ratio of a bearing, the elastic modulus of a lining and the position of an axis corner at the bearing and the position of the equivalent fulcrum, and giving a derivation process of a calculation formula of the equivalent fulcrum model;
3. by adopting the cyclic iterative alignment method, the defects of the finite element method and the traditional three bending moment method in the shafting alignment calculation are considered, the tail bearing fulcrum position value can be accurately obtained, the problem that the subjectively assumed tail bearing fulcrum position is not consistent with the actual shafting state in the alignment calculation is solved, and the alignment calculation result can be accurately obtained.
Drawings
Fig. 1 is a schematic flow diagram of an iterative calculation method for centering a ship propulsion shafting considering bearing factors in the invention.
The implementation, functional features and advantages of the present invention will be further described with reference to the accompanying drawings.
Detailed Description
It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1, a ship propulsion shafting alignment iterative calculation method considering bearing factors includes the following steps:
s1, discretizing the shaft section and giving an initial position value Z of the equivalent fulcrum of the tail bearing (0) ；
S2, centering and calculating a shaft system by using a three-bending moment method to obtain a journal corner at the tail bearing;
s3, substituting the journal rotation angle obtained in the previous step by using a tail bearing equivalent fulcrum calculation formula to calculate and obtain a new equivalent fulcrum position value Z (k) K is the number of iterations;
s4, when calculating to obtain a new equivalent fulcrum position value Z (k) Equivalent fulcrum position value Z before iteration (k-1) When the difference value is larger than the preset difference value (namely the new equivalent fulcrum position value does not meet the convergence condition), the Z value is determined (k) And Z (k-1) The average value of the two is used as a new equivalent fulcrum position value, the basis of calculating the journal rotation angle at the tail bearing in the next time is used, and the step S2 is executed again;
s5, when calculating to obtain a new equivalent fulcrum position value Z (k) Equivalent fulcrum position value Z before iteration (k-1) When the difference between Z and Z is less than or equal to the preset difference, namely the iteration convergence meets the preset condition, Z is adjusted (k) Substituting the three-bending moment method to calculate to obtain a final centering calculation result.
Specifically, in step S1, Z (0) The value range of (1/4-1/3) L, wherein L is the length of the tail bearing. Z is a linear or branched member (0) The value ranges of (a) are selected with reference to the specifications for the rosewood bearing. Referring to the CB/Z388-2005 standard, the distance from the equivalent fulcrum of the iron-pear-wood bearing bush to the rear end face of the bearing bush is in the range of (1/4-1/3) L, and L is the length of a tail bearing.
In step S2, the centering calculation is calculated by utilizing a three-bending moment method under an MATLAB program, input parameters such as the length-diameter ratio of the tail bearing, the lining elastic modulus and the like are given, and the initial equivalent fulcrum position Z is calculated (0) And substituting the three bending moments together to perform centering calculation to obtain the journal rotation angle at the tail bearing.
In step S3, a new equivalent fulcrum position value Z is obtained through calculation (k) And then, calculating according to the rotation angle, the elastic modulus and the length-diameter ratio of the shaft neck.
And calculating the equivalent fulcrum position of the tail bearing when different bearing length-diameter ratios, journal rotation angles and lining elastic moduli are calculated by using a finite element method in the equivalent fulcrum calculation formula of the tail bearing, and then fitting by using a linear regression analysis method to obtain a fulcrum coefficient.
In step S3, the relationship between the elastic modulus, the length-diameter ratio, and the corner of the tail bearing and the equivalent fulcrum position is:
Z (k) ＝a(L/D) b (θ (k) ) c E d ； (1)
in the formula: z (k) Calculating the equivalent fulcrum position of the tail bearing for the kth iteration; L/D is the length-diameter ratio of the tail bearing; theta.theta. (k) Calculating the journal rotation angle for the kth iteration; e is the elastic modulus of the liner of the tail bearing; a. b, c and d are fulcrum coefficients, and the fulcrum coefficients are obtained through a linear regression analysis method and simulation data fitting calculation.
In step S5, the criterion of iterative convergence is:
in the formula: and b is an iteration convergence coefficient. B may be 0.001.
In step S5, the final centering calculation result includes: corner, deflection, bending moment, bending stress, corner and bearing reaction force.
The equivalent pivot point calculation formula in step S3 can be derived by using a regression analysis method, and the specific derivation manner is as follows:
Z＝a(L/D) b θ c E d ； (3)
the formula (3) is linearized, and logarithms are taken at two sides of equal sign to obtain
ln(Z)＝ln(a)+b ln(L/D)+c ln(θ)+d ln(E) (4)
Then the linear regression equation is
y＝m+bx 1 +cx 2 +dx 3 (5)
y＝ln(Z)，m＝ln(a)，x 1 ＝ln(L/D)，x 2 ＝ln(θ)，x 3 ＝ln(E) (6)
And (3) applying a regression analysis method to the formula (5) to obtain the square sum of the position deviation of each fulcrum as follows:
in the formula: n is the sample volume; d i Is the fulcrum position deviation of the ith point; y is i Is the measured value of the fulcrum position of the ith point;
the theoretical value of the fulcrum position of the ith point.
The linear equation set is obtained as
The matrix form of the above equation set is Ab = B
The coefficient matrix to be solved is b = A -1 B。
The coefficient matrix to be solved in the formula is obtained by fitting and calculating simulation data. Inputting the values of L/D, theta and E in simulation software to obtain corresponding Z values, changing different input parameter values to obtain different Z values, thus obtaining a large amount of simulation data, and obtaining undetermined coefficients a, b, c and D through calculation.
Compared with the prior art, the ship propulsion shafting alignment iterative calculation method considering the bearing factors has the following advantages that:
1. by adopting a loop iteration centering method, the problem that the position of a subjectively assumed tail bearing fulcrum is inconsistent with the state of an actual shafting during centering calculation is solved in an iteration calculation mode;
2. the method comprises the steps of providing an equivalent fulcrum model considering bearing factors and a calculation method thereof, considering the bearing factors on the basis of the traditional equivalent fulcrum model, analyzing the relation between the length-diameter ratio of a bearing, the elastic modulus of a lining and the position of an axis corner at the bearing and the position of the equivalent fulcrum, and giving a derivation process of a calculation formula of the equivalent fulcrum model;
3. by adopting the cyclic iterative alignment method, the defects of the finite element method and the traditional three bending moment method in the shafting alignment calculation are considered, the tail bearing fulcrum position value can be accurately obtained, the problem that the subjectively assumed tail bearing fulcrum position is not consistent with the actual shafting state in the alignment calculation is solved, and the alignment calculation result can be accurately obtained.
In the actual correction of the propulsion shafting, the tail bearing fulcrum position is usually selected by reference to empirical data, but the tail bearing fulcrum position obtained in the method does not necessarily accord with the actual situation, and the circular iteration correction method provided by the invention can well solve the problem and obtain the tail bearing fulcrum position which is more accordant with the actual situation. In addition, with the development of modern ships, the calibration environment is more complicated due to the change of factors such as the length-diameter ratio of the bearing and the like, and for the problem, the influence of the length-diameter ratio of the bearing, the rotation angle of a journal and the elastic modulus of a bearing lining on the position of a bearing fulcrum is comprehensively considered, so that the position of the bearing fulcrum can be more conveniently and accurately selected under the condition of different factors.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the present specification and the drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (6)
1. A ship propulsion shafting alignment iterative computation method is characterized by comprising the following steps:
s1, discretizing a shaft section and giving an initial position value Z of an equivalent fulcrum of a tail bearing (0) ；
S2, centering and calculating a shaft system by using a three-bending moment method to obtain a journal corner at the tail bearing;
s3, substituting the journal rotation angle obtained in the previous step by using a tail bearing equivalent fulcrum calculation formula to calculate and obtain a new equivalent fulcrum position value Z (k) K is the number of iterations;
s4, when calculating to obtain a new equivalent fulcrum position value Z (k) Equivalent fulcrum position value Z before iteration (k-1) When the difference between Z and Z is greater than the preset difference, Z is determined (k) And Z (k-1) The average value of the two is used as a new equivalent fulcrum position value, the basis of the journal rotation angle at the tail bearing is calculated in the next time, and the step S2 is executed again;
s5, when calculating to obtain a new equivalent fulcrum position value Z (k) Equivalent fulcrum position value Z before iteration (k-1) When the difference between Z and Z is less than or equal to the preset difference, namely the iteration convergence meets the preset condition, the step Z is executed (k) Substituting the three-bending moment method to calculate to obtain a final correction calculation result;
and calculating the equivalent fulcrum position of the tail bearing when different bearing length-diameter ratios, journal rotation angles and lining elastic moduli are calculated by using a finite element method in the equivalent fulcrum calculation formula of the tail bearing, and then fitting by using a linear regression analysis method to obtain a fulcrum coefficient.
2. The ship propulsion shafting alignment iterative calculation method of claim 1, wherein in step S1, Z is (0) The value range of (1/4-1/3) L, wherein L is the length of the tail bearing.
3. As claimed inSolving 1 the iterative calculation method for centering the ship propulsion shafting, which is characterized in that in the step S3, a new equivalent fulcrum position value Z is calculated and obtained (k) And then, calculating according to the rotation angle, the elastic modulus and the length-diameter ratio of the shaft neck.
4. The ship propulsion shafting alignment iterative calculation method of claim 1, wherein in the step S3, the relation between the elastic modulus, the length-diameter ratio and the corner of the tail bearing and the equivalent fulcrum position is as follows:
Z (k) ＝a(L/D) b (θ (k) ) c E d ；
in the formula: z (k) Calculating the equivalent fulcrum position of the tail bearing for the kth iteration; L/D is the length-diameter ratio of the tail bearing; theta.theta. (k) Calculating the journal rotation angle for the kth iteration; e is the elastic modulus of the liner of the tail bearing; a. b, c and d are fulcrum coefficients, and the fulcrum coefficients are obtained by combining a linear regression analysis method with simulation data fitting calculation.
5. The iterative computation method for centering a ship propulsion shafting as claimed in claim 1, wherein in step S5, the criterion of iterative convergence is:
in the formula: and b is an iteration convergence coefficient.
6. The iterative computation method for centering a ship propulsion shafting according to any one of claims 1 to 5, wherein in step S5, the final centering computation result comprises: corner, deflection, bending moment, bending stress, corner and bearing reaction force.
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| JP2010143353A (en) * | 2008-12-18 | 2010-07-01 | Hitachi Zosen Corp | Method for evaluating shafting alignment in marine vessel |
| JP2012006596A (en) * | 2011-10-07 | 2012-01-12 | Hitachi Zosen Corp | Method and device for evaluating shaft system alignment in ship |
| CN103810305A (en) * | 2012-11-07 | 2014-05-21 | 中国舰船研究设计中心 | Alignment computing method of propeller shaft system of ship |
| KR20170022095A (en) * | 2015-08-19 | 2017-03-02 | 대우조선해양 주식회사 | Thruster mounting method for ship and jig for determination of alignment thereof |
| CN108920814A (en) * | 2018-06-28 | 2018-11-30 | 武汉理工大学 | Method is determined based on the reamer centering of shafting of marine shafting alignment calculation software |
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| JP2010143353A (en) * | 2008-12-18 | 2010-07-01 | Hitachi Zosen Corp | Method for evaluating shafting alignment in marine vessel |
| JP2012006596A (en) * | 2011-10-07 | 2012-01-12 | Hitachi Zosen Corp | Method and device for evaluating shaft system alignment in ship |
| CN103810305A (en) * | 2012-11-07 | 2014-05-21 | 中国舰船研究设计中心 | Alignment computing method of propeller shaft system of ship |
| KR20170022095A (en) * | 2015-08-19 | 2017-03-02 | 대우조선해양 주식회사 | Thruster mounting method for ship and jig for determination of alignment thereof |
| CN108920814A (en) * | 2018-06-28 | 2018-11-30 | 武汉理工大学 | Method is determined based on the reamer centering of shafting of marine shafting alignment calculation software |
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