A thrust measurement system for a ship shafting system and a method for eliminating thermal deformation

Abstract

The present invention discloses a thrust measurement system for a ship shafting and a method for eliminating thermal deformation, comprising: a measuring device, the measuring device includes a first fixed ring and a second fixed ring fixedly installed on a propeller rotating shaft, at least one measuring arm is fixedly arranged on the first fixed ring, the measuring arm is located between the first fixed ring and the second fixed ring, and a laser displacement sensor and a first temperature sensor are arranged on the measuring arm; further comprising a slip ring, a data acquisition system and a test computer. The present invention establishes a thermal-mechanical coupling finite element model of the local shafting-measuring device, simulates and studies the temperature field distribution and deformation law of the local shafting-measuring device, respectively selects a plurality of temperature compensation reference points on the rotating shaft and the measuring device, and uses a pseudo-inverse matrix to fit the functional relationship between these temperature reference points and the deformation of the measuring device, so as to eliminate the influence of thermal deformation with high precision.

Description

Technical Field

[0001] The present invention relates to the technical field of thrust measurement of ship propulsion shafting, and in particular to a ship shafting thrust measurement system and a method for eliminating thermal deformation. Background Technique

[0002] For the ship propulsion shafting, high-precision measurement of the shafting thrust can provide data support for the assessment of the shafting operating state. However, for the vast majority of rotors, their working environment temperature is often in dynamic change, and the temperature change will cause axial deformation of the rotor, which is mixed with the axial deformation caused by the shafting thrust. Therefore, if the temperature deformation interference is not eliminated, the shafting thrust measurement will be inaccurate.

[0003] When measuring the thrust of a ship propulsion shafting, the shafting thrust is often measured by monitoring the axial displacement or axial strain of the shafting. However, the environmental temperature change in the engine room will also cause axial deformation and strain of the shafting. Moreover, in many cases, the deformation caused by temperature even exceeds the deformation caused by the shafting thrust. Therefore, if these temperature deformation interferences are not eliminated, the measurement accuracy of the shafting thrust will be seriously affected.

[0004] Currently, when measuring the thrust of a ship propeller shafting, the measurement error of the shafting thrust is often too large due to the environmental temperature change. There are thermal compensation methods in the prior art to eliminate the influence of thermal deformation, such as:

[0005] The patent number is CN114660992A, and the patent name is a machine tool thermal error compensation method, device, computer device, system and machine tool, which specifically discloses real-time obtaining the first temperature of each component in the machine tool spindle connection mechanism and the second temperature of the machine tool execution mechanism; based on a preset thermal error calculation model, determining the comprehensive thermal error of the machine tool execution mechanism according to the first temperature and the second temperature; the comprehensive thermal error includes a first thermal error caused by the thermal deformation of the machine tool spindle connection structure and a second thermal error caused by the thermal deformation of the machine tool execution mechanism; according to the comprehensive thermal error, feeding back a thermal error compensation amount to the drive mechanism; the thermal error compensation amount is used to instruct the drive mechanism to perform corresponding thermal error compensation.

[0006] The patent number is CN114895627A, and the patent name is a method for compensating thermal errors of a machine tool in sub-regions, which specifically discloses the following steps: First, select multiple position points on the machine tool table, divide the table into multiple regions, and record the two-dimensional coordinates of each position point; Second, select multiple temperature measurement points on the machine tool, and regularly measure the thermal error variable data of each position point and the temperature variable data of each temperature measurement point simultaneously; Third, select a temperature measurement point as the corresponding temperature-sensitive point for each position point respectively, and establish a thermal error prediction model; Fourth, determine the region to which the spindle belongs according to the position of the machine tool spindle; Fifth, call the thermal error prediction models of each position point included in the region to which the spindle belongs, predict the spindle thermal error of each position point according to the temperature variable data of the temperature-sensitive point measured in real time, and take the average value of the thermal error prediction data of each position point to predict and compensate the thermal error of this region; Sixth, when the position of the machine tool spindle changes, repeat steps five and six until the thermal error compensation ends.

[0007] The patent number is CN113297761A, and the patent name is a method for testing and compensating thermal deformation of a numerically controlled machine tool, which specifically discloses the following steps: S1. Establish an initial three-dimensional model of the machine tool; S2. Start at least one first inductor group and a second inductor group to monitor the data field of the machine tool in real time; S3. The control terminal receives the monitored data field in real time and establishes a real-time three-dimensional model; S4. Compare the initial three-dimensional model with the real-time three-dimensional model to determine the real-time amount of thermal deformation; S5. Conduct finite element analysis verification, use ANSYS software for simulation analysis, and judge whether the deviation between the real-time monitored data and the predicted data meets the requirements; S6. Control the thermal compensation control device to achieve thermal deformation compensation of the machine tool. The technical solution of the present invention can more realistically reflect the actual situation of the thermal deformation of the machine tool, reduce the number of monitoring inductors, reduce costs, and improve the compensation accuracy and stability.

[0008] However, due to the difference in the heat transfer speed of the ship shafting and the influence of the complex geometry of the measuring device, the temperature distribution on the measuring device and the rotating shaft is uneven, and both lag behind the ambient temperature. Therefore, it is difficult to appropriately select the temperature compensation reference when using temperature compensation, resulting in difficulty in effectively eliminating the influence of thermal deformation. Summary of the Invention

[0009] In order to solve the problem that the thrust measurement of the ship propeller shafting in the prior art is greatly affected by changes in the ambient temperature and it is impossible to achieve accurate measurement using a simple thermal compensation method, the present invention provides a ship shafting thrust measurement system and a method for eliminating thermal deformation.

[0010] The technical solution of the present invention is: A ship shafting thrust measurement system includes:

[0011] Measuring device, the measuring device includes a first fixed ring and a second fixed ring fixedly installed on the propeller shaft. At least one measuring arm is fixedly arranged on the first fixed ring. The measuring arm is located between the first fixed ring and the second fixed ring. A laser displacement sensor and a first temperature sensor are arranged on the measuring arm;

[0012] Slip ring, the slip ring is fixed on the propeller shaft, used to provide working voltage for the laser displacement sensor and the temperature sensor, and transmit the displacement signal and the temperature signal to the data acquisition system;

[0013] Data acquisition system, the data acquisition system transmits the test data to the test computer;

[0014] Test computer, the test computer analyzes the relevant data, and processes the data through the established function relationship between the shafting thrust and the longitudinal displacement between the two fixed rings to obtain the shafting thrust.

[0015] Preferably, the number of measuring arms is 2, and they are symmetrically arranged about the center line of the propeller shaft.

[0016] Preferably, the function of the shafting thrust and the longitudinal displacement between the two fixed rings is:

[0017]

[0018] Where F T is the shafting thrust, E is the elastic modulus of the shaft section; A is the cross-sectional area of the shaft section; L is the distance between the opposite faces of the first fixed ring and the second fixed ring; is the longitudinal average displacement, d1 and d2 are the longitudinal displacements measured by the two laser displacement sensors respectively; d F is the displacement generated by the pure shafting thrust; d ΔT is the longitudinal displacement caused by the temperature change; ΔT i is the temperature rise of different parts of the shafting-measuring device; k i is the proportionality coefficient; n is the number of selected temperature monitoring points.

[0019] Preferably, the longitudinal displacement d ΔT caused by the temperature change is d ΔT = k1·ΔT s - k2·ΔT b where k1 = α s ·L s and k2 = α b ·L b ΔT s is the temperature rise of the propeller shaft, obtained by the first temperature sensor; ΔT b is the temperature rise of the measuring arm, obtained by the second temperature sensor arranged on the propeller shaft; α sis the coefficient of thermal expansion of the propeller shaft; α b is the coefficient of thermal expansion of the measuring arm; L s is the equivalent distance between the end faces of the two fixed rings; L b is the equivalent length of the measuring arm.

[0020] Preferably, the formula for the shafting thrust under the influence of temperature is:

[0021]

[0022] A method for eliminating thermal deformation in ship shafting thrust measurement includes the following steps:

[0023] Step1. Select a measuring point position on the propeller shaft, and then measure the shaft diameter at the selected measuring point.

[0024] Step2. Machine a measuring device according to the shaft diameter and install it on the propeller shaft.

[0025] Step3. Select a local shaft section - measuring device, establish a finite element model for its thermal - force analysis, use the transient analysis method to analyze the variation law of the temperature of the shaft section - measuring device with time after the environmental temperature changes, select two points at the middle of the measuring arm and the middle of the shaft, and save their temperature data.

[0026] Step4. Use the calculated temperature field data as the load for structural deformation analysis, and use the transient analysis method to analyze the variation law of the deformation of the shaft section - measuring device with time; select three points at the right end face of the first fixed ring, the right end face of the measuring arm, and the left end face of the second fixed ring, and save their longitudinal deformation data.

[0027] Step5. Denote the temperature rise at the measuring point in the middle of the shaft as ΔT s and the temperature rise at the measuring point in the middle of the measuring arm as ΔT b the displacement at the right end face of the first fixed ring as d s1 the displacement at the left end face of the second fixed ring as d s2 the displacement at the right end face of the measuring arm as d b1 , then there are the following relationships:

[0028] α s ·L s ·ΔT s =d s1 -d s2

[0029] α b ·L b ·ΔT b =d s1 -d b1

[0030] α s ·L s·ΔT s -α b ·L b ·ΔT b =d b1 -d s2 ;

[0031] The first formula represents the thermal deformation of the rotating shaft; the second formula represents the thermal deformation of the measuring arm relative to the first fixed ring; the third formula represents the thermal deformation between the front end of the measuring arm and the second fixed ring, and this deformation is directly reflected in the laser measurement signal. L s and L b respectively represent the equivalent distance between the end faces of the two fixed rings and the equivalent length of the measuring arm.

[0032] Step6. Due to the complex geometric shape of the measuring device, L s is not the distance between the two fixed rings, and L b is also not the length of the measuring arm. It needs to be fitted through simulation data. Write the formula in Step5 in matrix form:

[0033]

[0034] In the formula, O is a zero matrix. When performing transient calculations in Step3, a total of N time steps are calculated. Therefore, the above formula represents a system of equations with 2 unknowns and 3N equations, and the pseudo-inverse method can be used to solve it:

[0035]

[0036] In the formula,

[0037] Step7. After obtaining the equivalent lengths L s and L b in Step6, combined with the functional relationship between the thrust of the shafting and the longitudinal displacement between the two fixed rings, the shafting thrust can be obtained as:

[0038]

[0039] In the formula, E is the elastic modulus of the shaft segment; A is the cross-sectional area of the shaft segment; L is the distance between the opposite faces of the first fixed ring (1) and the second fixed ring (2); is the longitudinal average displacement, where d1 and d2 are the longitudinal displacements measured by the two laser displacement sensors (4) respectively; d F is the displacement caused by the pure shafting thrust; d ΔT is the longitudinal displacement caused by the temperature change.

[0040] Preferably, in Step1, the test point is selected near the propeller side of the shafting thrust bearing.

[0041] Preferably, in the Step 5, multiple temperature detection points are added, including one or more of the first fixed ring and the second fixed ring, and the steps of Step 5 to Step 7 are carried out.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] By establishing a thermal-mechanical coupling finite element model of the local shafting-measuring device, the present invention simulates and studies the temperature field distribution and deformation law of the local shafting-measuring device, selects multiple temperature compensation reference points on the rotating shaft and the measuring device respectively, and uses the pseudo-inverse matrix to fit the functional relationship between these temperature reference points and the deformation of the measuring device, so as to eliminate the influence of thermal deformation with high precision. Description of the Drawings

[0044] Figure 1 is a schematic three-dimensional structure diagram of the measuring device of the present invention;

[0045] Figure 2 is a schematic three-dimensional (4 measuring arms) structure diagram of the measuring device of the present invention;

[0046] Figure 3 is a flowchart of thermal deformation elimination of the present invention;

[0047] Figure 4 is a schematic diagram of the dimensions of the measuring device-shafting in Embodiment 1 of the present invention;

[0048] Figure 5 is a schematic diagram of the temperature field simulation result in Embodiment 1 of the present invention;

[0049] Figure 6 is a schematic diagram of the comparison of the ambient temperature, the temperature at the monitoring point in the middle of the rotating shaft and the temperature at the monitoring point in the middle of the measuring arm in Embodiment 1 of the present invention;

[0050] Figure 8 is a schematic diagram of the predicted thermal deformation and predicted error curves in Embodiment 1 of the present invention;

[0051] Figure 9 is a schematic diagram of the comparison of the ambient temperature, the temperature at the monitoring point in the middle of the rotating shaft and the temperature at the monitoring point in the middle of the measuring arm in Embodiment 2 of the present invention;

[0052] Figure 10 is the equivalent length L s (787 mm) and L b (573 mm) substituted into the predicted thermal deformation and predicted error curve schematic diagram.

[0053] Reference numerals: 1, first fixed ring; 2, second fixed ring; 3, measuring arm; 4, laser displacement sensor; 5, first temperature sensor; 6, second temperature sensor; 7, propeller rotating shaft. Detailed implementation mode

[0054] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0055] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "front", "rear", "left", "right", "up", "down", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. The technical solutions in the embodiments of the present invention can be combined, and the technical features in the embodiments can also be combined to form a new technical solution.

[0056] The present invention provides the following technical solutions:

[0057] As shown in the attached Figure 1 figure, the propeller shaft thrust measuring device comprises five parts. Among them, the measuring device is fixed on the propeller rotating shaft 7 by bolts and nuts through the first fixing ring 1 and the second fixing ring 2. The measuring arm 3 is fixed on the first fixing ring 1 by bolts and nuts. The first temperature sensor 5 and the laser displacement sensor 4 are fixed on the measuring arm 3. As shown in the attached Figure 1 figure, two measuring arms 3 are symmetrically arranged on the first fixing ring 1, but it is not limited to two. A plurality of measuring arms 3 can be arranged at equal intervals on the first fixing ring 1. For example, in the attached Figure 2 figure, there are 4. The arrangement of a plurality of measuring arms 3 is beneficial to improving the accuracy.

[0058] In addition, it also includes a slip ring, a data acquisition system and a test computer fixed on the rotating shaft. These are all mature products on the market (so they are not shown in the attached drawings). The slip ring has two functions. One is to provide the working voltage for the laser displacement sensor 4, and the other is to transmit the displacement signal to the data acquisition system. Finally, the test data is transmitted to the test computer for processing through the data acquisition system, thus constituting the entire measuring system.

[0059] The working principle of this measuring device is as follows: when the propeller rotating shaft 7 deforms under the action of the propeller shaft thrust, a longitudinal relative displacement will be generated between the two fixing rings. This relative displacement can be sensed by the laser displacement sensor 4. By establishing the functional relationship between the shaft thrust and the longitudinal displacement between the two fixing rings, the propeller shaft thrust can be obtained.

[0060] A laser displacement sensor 4 is symmetrically arranged above and below the measuring device, and the influence of the bending deformation of the shafting is eliminated by adding the signals of the two laser displacement sensors 4. However, when the ambient temperature changes, longitudinal thermal deformations will occur in both the rotating shaft and the measuring arm 3, thus interfering with the measurement accuracy of the shafting thrust.

[0061] When the shafting is under the combined action of the propeller shafting thrust and bending moment, the readings of the two laser displacement sensors 4 are:

[0062] d1 = d F -d M +d ΔT , d2 = d F +d M +d ΔT (1)

[0063] In the formula, d1 and d2 are the longitudinal displacements measured by the two laser displacement sensors 4 respectively; d F is the displacement generated by the pure shafting thrust; d M is the displacement generated by the pure bending moment; d ΔT is the longitudinal displacement caused by the temperature change.

[0064] In the present invention, the temperature rise and the deformation are linearly related, and the thermal deformation between the right end face of the measuring arm 3 and the left end face of the second fixing ring 2 can be expressed as:

[0065]

[0066] In the formula, ΔT i is the temperature rise at different parts of the shafting-measuring device; k i is the proportionality coefficient; n is the number of selected temperature monitoring points. The physical meaning of this formula is that the thermal deformation between the end of the measuring arm 3 and the 2# fixing ring can be expressed as the superposition of the thermal deformations caused by multiple local temperatures. In actual use, the effect is poor when n takes 1, and satisfactory results can be obtained when n takes 2 or more.

[0067] The average displacement obtained by the two laser displacement sensors 4 can be expressed as:

[0068]

[0069] The shafting thrust F T and the longitudinal average displacement are related as follows:

[0070]

[0071] In the formula, L is the distance between the right end face of the first fixing ring 1 and the left end face of the second fixing ring 2; E is the elastic modulus of the shaft section; A is the cross-sectional area of the shaft section.

[0072] As can be seen from formula (4), after obtaining the longitudinal displacement After obtaining the temperature rise ΔT of each local monitoring point i and its proportionality coefficient k i , the thrust F of the shafting can be calculated T .

[0073] In this embodiment, two temperature monitoring points are selected in the middle of the propeller shaft 7 and the middle of the measuring arm 3. The method for determining the proportionality coefficient k (i.e., the method for eliminating thermal deformation) is as shown in the appendix Figure 3 as follows:

[0074] 1) First, select the measuring point position on the propeller shaft 7. Usually, the test point is selected on the propeller side near the thrust bearing of the shafting, and then measure the diameter of the shaft section at the selected measuring point;

[0075] 2) Machine the measuring device according to the shaft section diameter and install it on the propeller shaft 7;

[0076] 3) Select the local shaft section - measuring device, establish its thermal - mechanical analysis finite element model, and use the transient analysis method to analyze the variation law of the temperature of the shaft section - measuring device with time after the environmental temperature changes; as shown in Figure 1 , two points are selected in the middle of the measuring arm 3 and the middle of the propeller shaft 7, and the first temperature sensor 5 and the second temperature sensor 6 are respectively set, and their temperature data are saved. Therefore, the second temperature sensor 6 needs to be set on the propeller shaft 7, and the second temperature sensor 6 is connected to the slip ring;

[0077] 4) Take the calculated temperature field data as the load for structural deformation analysis, and use the transient analysis method to analyze the variation law of the deformation of the shaft section - measuring device with time; select three points on the right end face of the first fixing ring 1, the right end face of the measuring arm 3, and the left end face of the second fixing ring 2, and save their longitudinal deformation data;

[0078] 5) Denote the temperature rise of the measuring point in the middle of the propeller shaft 7 as ΔT s , the temperature rise of the measuring point in the middle of the measuring arm 3 as ΔT b , the displacement of the right end face of the first fixing ring 1 as d s1 , the displacement of the left end face of the second fixing ring 2 as d s2 , and the displacement of the right end face of the measuring arm 3 as d b1 , then there are the following relationships:

[0079] α s ·L s ·ΔT s =d s1 -d s2

[0080] α b ·L b ·ΔT b =d s1 -db1

[0081] α s ·L s ·ΔT s -α b ·L b ·ΔT b =d b1 -d s2 (5)

[0082] In the above formula (5), α s and α b are the thermal expansion coefficients of the rotating shaft and the measuring arm 3 respectively; the first formula represents the thermal deformation of the rotating shaft; the second formula represents the thermal deformation of the measuring arm 3 relative to the first fixed ring 1; the third formula represents the thermal deformation between the front end of the measuring arm 3 and the second fixed ring 2, and this deformation is directly reflected in the laser measurement signal, which is exactly the second term in formula (1); L s and L b represent the equivalent distance between the end faces of the two fixed rings and the equivalent length of the measuring arm 3 respectively.

[0083] Considering the complex geometric shape of the measuring device, L s is not the distance between the two fixed rings, and L b is not the length of the measuring arm 3 either, and it needs to be fitted through simulation data. Write formula (5) in matrix form:

[0084]

[0085] In the formula, O is the zero matrix. Assume that during the transient calculation in step (3), a total of N time steps are calculated. Therefore, formula (6) represents a system of equations with 2 unknowns and 3N equations, and the pseudo-inverse method can be used to solve it:

[0086]

[0087] In the formula,

[0088] 6) After obtaining the equivalent lengths L s and L b according to formula (7), combined with formula (4), the shaft system thrust can be obtained as:

[0089]

[0090] In the formula, E is the elastic modulus of the shaft section; A is the cross-sectional area of the shaft section; L is the distance between the opposite faces of the first fixed ring (1) and the second fixed ring (2); is the longitudinal average displacement, where d1 and d2 are the longitudinal displacements measured by the two laser displacement sensors (4) respectively; d F is the displacement generated by the pure shaft system thrust; dΔT is the longitudinal displacement caused by temperature change.

[0091] Therefore, the thermal deformation prediction formula is:

[0092] d ΔT = k1·ΔT s - k2·ΔT b (9)

[0093] In the formula, k1 = α s ·L s , k2 = α b ·L b .

[0094] 6) Apply the shaft system thrust, measure the temperature of the support arm with the first temperature sensor 5, measure the shaft system temperature with the second temperature sensor 6, measure the longitudinal displacement with the laser sensor, and solve the shaft system thrust according to Equation 8), thereby reducing the influence of thermal deformation.

[0095] Example 1

[0096] As shown in the Figure 4 attachment, for a certain actual ship propulsion shaft system, the shaft diameter at the shaft system thrust measurement device is 500 mm, the distance between the two fixed rings is 800 mm, the length of the measuring arm 3 is 550 mm, and the shaft system thrust it bears is 200 tons.

[0097] Assume that the ambient temperature changes according to the following formula:

[0098]

[0099] In the formula, T0 is the initial temperature (30 °C); ΔT is the temperature change amplitude (5 °C); t s is the temperature change time (12 hours).

[0100] As shown in the Figure 5 attachment is the temperature field simulation result, and the Figure 6 attachment is the comparison of the ambient temperature, the temperature at the monitoring point in the middle of the rotating shaft, and the temperature at the monitoring point in the middle of the measuring arm 3. It can be seen that the temperatures of the rotating shaft, the fixed ring, and the measuring arm 3 are not the same, and the measuring arm 3 can follow the ambient temperature faster.

[0101] The Figure 7 attachment is the relationship between the thermal deformation measured by the laser (the thermal deformation between the front end of the measuring arm 3 and the left end face of the second fixed ring 2) and the ambient temperature, the rotating shaft temperature, and the temperature of the measuring arm 3 respectively. It can be seen that this deformation is not linearly related to any local temperature. Therefore, it also indirectly shows that the assumption of Equation (2) is correct, that is, the thermal deformation measured by the laser needs to be expressed as a linear function of multiple local temperatures.

[0102] The equivalent length L obtained according to Equation (7) s and Lb They are 787 mm and 573 mm respectively, with a slight difference from the distance of 800 mm from the fixed ring and the length of the measuring arm 3 of 550 mm. Figure 8 They are the thermal deformations and errors predicted by Equation (9). It can be seen that the prediction errors are very small, all within 1.2 μm, indicating the effectiveness of the method proposed by the present invention. For the 200-ton shaft system thrust, the measurement error of the shaft system thrust caused by the compensated thermal deformation error does not exceed 3%.

[0103] Example 2:

[0104] To verify that the equivalent lengths L s (787 mm) and L b (573 mm) obtained in the previous example are also applicable to other temperature changes, this example assumes that the ambient temperature changes according to the following function:

[0105]

[0106] In the formula, the temperature unit is °C and the time unit is hour.

[0107] Figure 9 They are the comparisons of the ambient temperature, the temperature at the monitoring point in the middle of the rotating shaft, and the temperature at the monitoring point in the middle of the measuring arm 3. It can be seen that the temperature changes of the rotating shaft and the measuring arm 3 are not the same, and the measuring arm 3 can follow the ambient temperature faster.

[0108] Figure 10 They are the differences between the thermal deformations predicted by substituting the equivalent lengths L s (787 mm) and L b (573 mm) into Equation (9) and the thermal deformations calculated by the finite element method (i.e., the true deformations). It can be seen that the prediction errors are very small, all within 0.5 μm, indicating the effectiveness of the method proposed by the present invention. For the 200-ton shaft system thrust, the prediction accuracy of the thermal deformation can ensure that the measurement error of the shaft system thrust does not exceed 1.3%. This example shows that the equivalent lengths L s (787 mm) and L b (573 mm) fitted according to the sine temperature change are also applicable to the linearly changing temperature, indicating the universality of the fitted equivalent lengths, and thus applicable to the case where the ambient temperature changes according to any function.

[0109] Example 3

[0110] The present invention proposes to use formula (2) to simulate the thermal deformation between the front end of the measuring arm 3 and the fixed ring, and n temperature monitoring points can be set in this formula. However, only two temperature monitoring points are set in the middle of the rotating shaft and the middle of the measuring arm 3 in the above examples. The present invention can also set multiple temperature monitoring points. For example, in addition to monitoring the temperature rise ΔT s in the middle of the rotating shaft, the temperature rise ΔT bIn addition, a temperature monitoring point is added to the first fixing ring 1, and its temperature rise can be expressed as ΔT r . At this time, in the finite element deformation simulation, let the displacement of the right end face of the first fixing ring 1 be d s0 , the displacement of the rear end face of the first fixing ring 1 be d s1 , the displacement of the right end face of the second fixing ring 2 be d s2 , and the displacement of the right end face of the measuring arm 3 be d b1 . Then there are the following relational expressions:

[0111] α r ·L r ·ΔT r = d s0 - d s1

[0112] α s ·L s ·ΔT s = d s0 - d s2

[0113] α b ·L b ·ΔT b = d s1 - d b1

[0114] α s ·L s ·ΔT s - α b ·L b ·ΔT b - α r ·L r ·ΔT r = d b1 - d s2 (12)

[0115] In Equation (5), α s , α b and α r are the thermal expansion coefficients between the rotating shaft, the measuring arm 3 and the first fixing ring 1 respectively; the first equation represents the longitudinal thermal deformation of the first fixing ring 1; the second equation represents the longitudinal thermal deformation of the rotating shaft; the third equation represents the longitudinal thermal deformation of the measuring arm 3 relative to the first fixing ring 1; the fourth equation represents the longitudinal thermal deformation between the front end of the measuring arm 3 and the left end face of the 2# fixing ring; L r represents the equivalent width of the 1# fixing ring; L s represents the equivalent distance from the left end face of the 1# fixing ring to the left end face of the 2# fixing ring; L b represents the equivalent length of the measuring arm 3. The pseudo-inverse solution of Equation (12) is:

[0116]

[0117] In the formula, the shafting thrust can be obtained as:

[0118]

[0119] Therefore, the thermal deformation prediction formula is:

[0120] d ΔT = k1·ΔT s - k2·ΔT b - k3·ΔT r (9)

[0121] In the formula, k1 = α s ·L s ,k2 = α b ·L b ,k3 = α r ·L r 。

[0122] Similarly, a temperature monitoring point can also be additionally provided on the second fixed ring, and even the shaft section can be divided into several sections according to the temperature change law, and a temperature monitoring point is set for each section. For the derivation of the thermal deformation prediction formula with more than 3 temperature monitoring points, the process is similar to the above.

[0123] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A thrust measurement system for a ship shafting, characterized in that, Comprising: A measuring device, the measuring device includes a first fixing ring (1) and a second fixing ring (2) fixedly installed on a propeller shaft (7), a plurality of measuring arms (3) arranged at equal intervals are fixedly provided on the first fixing ring (1), the measuring arms (3) are located between the first fixing ring (1) and the second fixing ring (2), and a laser displacement sensor (4) and a first temperature sensor (5) are provided on the measuring arms (3); A slip ring, the slip ring is fixed on the propeller shaft (7) for providing working voltage to the laser displacement sensor (4) and the temperature sensor, and transmitting displacement signals and temperature signals to a data acquisition system; A data acquisition system, the data acquisition system transmits test data to a test computer; A test computer, the test computer analyzes relevant data, and processes the data through the established function relationship between the shafting thrust and the longitudinal displacement between the two fixing rings to obtain the shafting thrust; The number of the measuring arms (3) is 2, and they are symmetrically arranged about the center line of the propeller shaft (7); The function of the shafting thrust and the longitudinal displacement between the two fixing rings is: Among them, F T is the thrust of the shafting, E is the elastic modulus of the shaft section; A is the cross-sectional area of the shaft section; L is the distance between the opposite faces of the first fixing ring (1) and the second fixing ring (2); is the longitudinal average displacement, d1 and d2 are the longitudinal displacements measured by two laser displacement sensors (4) respectively; d F is the displacement caused by the pure shafting thrust; d ΔT is the longitudinal displacement caused by the temperature change; ΔT i is the temperature rise of different parts of the shafting-measuring device; k i is the proportionality coefficient; n is the number of selected temperature monitoring points; The longitudinal displacement d caused by the temperature change ΔT is d ΔT = k1·ΔT s - k2·ΔT b , where k1 = α s ·L s , k2 = α b ·L b , ΔT s is the temperature rise of the propeller shaft (7), obtained by the first temperature sensor (5); ΔT b is the temperature rise of the measuring arm (3), obtained by the second temperature sensor (6) arranged on the propeller shaft (7); α s is the thermal expansion coefficient of the propeller shaft (7); α b is the thermal expansion coefficient of the measuring arm (3); L s is the equivalent distance between the end faces of the two fixing rings; L b is the equivalent length of the measuring arm (3); The formula of the shafting thrust under the influence of temperature is:

2. A method for eliminating thermal deformation of the thrust measurement system of a ship shafting according to claim 1, characterized in that, Including the following steps: Step1. Select a measuring point position on the propeller shaft (7), and then measure the shaft diameter at the selected measuring point; Step2. Machine the measuring device according to the shaft diameter and install it on the propeller shaft (7); Step3. Select a local shaft section - measuring device, establish a thermal - mechanical analysis finite element model, use the transient analysis method to analyze the temperature change law of the shaft section - measuring device with time after the environmental temperature changes, select two points at the middle of the measuring arm (3) and the middle of the shaft, and save their temperature data; Step4. Take the calculated temperature field data as the load for structural deformation analysis, use the transient analysis method to analyze the deformation change law of the shaft section - measuring device with time; select three points at the right end face of the first fixing ring (1), the right end face of the measuring arm (3) and the left end face of the second fixing ring (2), and save their longitudinal deformation data; Step 5. Record the temperature rise at the measuring point in the middle of the rotating shaft as ΔT s The temperature rise at the measuring point in the middle of the measuring arm (3) is ΔT b The displacement of the right end face of the first fixing ring (1) is d s1 The displacement of the left end face of the second fixing ring (2) is d s2 The displacement of the right end face of the measuring arm (3) is d b1 Then there is the following relational expression: α s ·L s ·ΔT s =d s1 -d s2 α b ·L b ·ΔT b =d s1 -d b1 α s ·L s ·ΔT s -α b ·L b ·ΔT b = d b1 -d s2 The first formula represents the thermal deformation of the rotating shaft; the second formula represents the thermal deformation of the measuring arm (3) relative to the first fixed ring (1); the third formula represents the thermal deformation between the right end of the measuring arm (3) and the second fixed ring (2), and this deformation is directly reflected in the laser measurement signal, L s and L b respectively represent the equivalent distance between the end faces of the two fixed rings and the equivalent length of the measuring arm (3); Step6. Due to the complex geometry of the measuring device, L s is not the distance between the two fixed rings, L b nor is it the length of the measuring arm (3). It is necessary to fit the formula in Step5 into matrix form through simulation data: In the formula, O is a zero matrix. When performing transient calculation in Step3, a total of N time steps are calculated. Therefore, the above formula represents a system of equations with 2 unknowns and 3N equations, and the pseudo - inverse method can be used to solve it: Wherein, Step 7. According to the equivalent length L obtained in Step 6 s and L b After that, combining with the relational expression of the shafting thrust and the longitudinal displacement function between the two fixed rings, the shafting thrust can be obtained as follows: Wherein, E is the elastic modulus of the shaft section; A is the cross-sectional area of the shaft section; L is the distance between the opposite faces of the first fixing ring (1) and the second fixing ring (2); is the longitudinal average displacement, where d1 and d2 are the longitudinal displacements measured by the two laser displacement sensors (4) respectively; d F is the displacement generated by the pure shaft system thrust; d ΔT is the longitudinal displacement caused by the temperature change.

3. The thermal deformation elimination method according to claim 2, wherein: In Step1, the test point is selected on the side of the propeller near the thrust bearing.

Images