Quick calculation method and system for vibration response of shaft system of diesel engine

Abstract

The invention provides a quick calculation method and system for vibration response of a shaft system of a diesel engine, and the method comprises the steps: simplifying a crankshaft system and stress of the diesel engine, and obtaining a simplified model of the diesel engine; on the basis of a straight beam unit, a transverse vibration transfer matrix, a longitudinal vibration transfer matrix and a torsional vibration transfer matrix of a straight beam are established respectively, and a spatial continuum transfer matrix of the straight beam is calculated; establishing a point transfer matrix of coordinate transformation at each section of straight beam connection point through a force balance condition and a displacement coordination condition; lapping a transfer matrix from a single crank to the whole crankshaft system according to the spatial continuum transfer matrix of the straight beam and the point transfer matrix of coordinate transformation; constructing a kinetic equation according to a transfer matrix from a single crank to the whole crankshaft system; calculating the inherent frequency of the crankshaft system according to the kinetic equation; the method comprises the following steps: loading an exciting force map on a crank pin of a crankshaft system, and solving forced vibration response of any point on a crankshaft by using a Newmark-beta method.

Description

Technical Field

[0001] The invention relates to the technical field of diesel engine shaft system vibration response calculation and design, and in particular to a fast calculation method and system for diesel engine shaft system vibration response. Background Art

[0002] The ship power plant (diesel engine, gas engine, steam turbine and electric motor) refers to the entire device that transfers the energy of the prime mover to the load. It is the entire transmission and support system starting from the prime mover through the gearbox, transmission shaft section and other devices to the load. The composition of ship power plants is becoming increasingly complex, the structure and layout are more compact, the power density is constantly increasing, the operating environment is becoming more severe, and the operating conditions change frequently. These characteristics have relatively high requirements for the quietness, safety, reliability and intelligent control of ship power plants.

[0003] In actual engineering, diesel engines are the main excitation source of vibration and noise in the hull, and their vibration directly affects the smooth operation of the ship. The diesel engine shaft system is prone to breakage due to time-varying excitation. Once the shaft system breaks, the ship loses power, which will cause unbearable losses. Most existing theories discretize the shaft system for calculation, which is difficult to meet the calculation accuracy of complex and large-sized shaft systems.

[0004] The crankshaft system in a diesel engine is a spatial structure with a three-dimensional vibration form. The current shaft system calculation method is mainly based on existing empirical formulas and finite element methods to perform shaft system calculation and design.

[0005] Most of the research based on empirical formulas is based on a large amount of experimental data from mature models that have already been built. This method is suitable for specific types of diesel engines and cannot be used as a general calculation method. The finite element method requires a relatively complex and time-consuming diesel engine three-dimensional finite element model construction and simulation calculation, and does not truly understand the three-dimensional coupled vibration mechanism of the diesel engine crankshaft in the lateral (bending), longitudinal, and torsional directions. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a fast calculation method and system for the vibration response of a diesel engine shaft system, which increases the simulation calculation accuracy by assuming that the shaft vibration actually exists in three-dimensional coupled vibration; based on the continuum vibration theory, the time domain signal of the forced vibration response of any part of the crankshaft can be extracted to ensure the integrity of the calculation; the state parameters such as the crankshaft geometric dimensions are directly simplified, the calculation time is short, the calculation accuracy is controllable, and it has good versatility and engineering applicability.

[0007] In a first aspect, an embodiment of the present invention provides a method for quickly calculating the vibration response of a diesel engine shaft system, the method comprising:

[0008] Simplifying the crankshaft system and the forces of the diesel engine to obtain a simplified model of the diesel engine; wherein the simplified model of the diesel engine includes an excitation force;

[0009] Based on the straight beam unit, the lateral vibration transfer matrix, longitudinal vibration transfer matrix and torsional vibration transfer matrix of the straight beam are established respectively;

[0010] Calculating the space continuum transfer matrix of the straight beam according to the lateral vibration transfer matrix, the longitudinal vibration transfer matrix and the torsional vibration transfer matrix;

[0011] A point transfer matrix for coordinate transformation at the connection points of the straight beams of each section is established through force balance conditions and displacement coordination conditions;

[0012] A transfer matrix of a single crank to the entire crankshaft system is overlapped according to the spatial continuum transfer matrix of the straight beam and the point transfer matrix of the coordinate transformation;

[0013] Constructing dynamic equations based on the transfer matrix from the single crank to the entire crankshaft system;

[0014] Calculating the natural frequency of the crankshaft system according to the dynamic equation;

[0015] The spectrum of the excitation force is loaded on the crank pin of the crankshaft system, and the forced vibration response of any point on the crankshaft is solved using the Newmark-β method.

[0016] In a second aspect, an embodiment of the present invention provides a fast calculation system for diesel engine shaft system vibration response, the system comprising:

[0017] A simplification module, used for simplifying the crankshaft system and the forces of the diesel engine to obtain a simplified model of the diesel engine; wherein the simplified model of the diesel engine includes an excitation force;

[0018] The first establishment module is used to establish the lateral vibration transfer matrix, the longitudinal vibration transfer matrix and the torsional vibration transfer matrix of the straight beam based on the straight beam unit;

[0019] A first calculation module, used for calculating the space continuum transfer matrix of the straight beam according to the lateral vibration transfer matrix, the longitudinal vibration transfer matrix and the torsional vibration transfer matrix;

[0020] The second establishment module is used to establish a point transfer matrix of coordinate transformation at the connection points of each section of the straight beam through force balance conditions and displacement coordination conditions;

[0021] A connection module, used for connecting a single crank to the transfer matrix of the entire crankshaft system according to the spatial continuum transfer matrix of the straight beam and the point transfer matrix of the coordinate transformation;

[0022] A construction module, for constructing a dynamic equation according to a transfer matrix from the single crank to the entire crankshaft system;

[0023] A second calculation module, used for calculating the natural frequency of the crankshaft system according to the dynamic equation;

[0024] A solution module is used to load the spectrum of the excitation force on the crank pin of the crankshaft system and solve the forced vibration response of any point on the crankshaft by using the Newmark-β method.

[0025] In a third aspect, an embodiment of the present invention provides an electronic device, including a memory and a processor, wherein the memory stores a computer program executable on the processor, and the processor implements the method described above when executing the computer program.

[0026] The embodiment of the present invention provides a fast calculation method and system for the vibration response of a diesel engine shaft system, comprising: simplifying the crankshaft system and the forces of the diesel engine to obtain a simplified model of the diesel engine; wherein the simplified model of the diesel engine includes an excitation force; based on a straight beam unit, establishing a lateral vibration transfer matrix, a longitudinal vibration transfer matrix and a torsional vibration transfer matrix of the straight beam respectively; calculating a spatial continuum transfer matrix of the straight beam according to the lateral vibration transfer matrix, the longitudinal vibration transfer matrix and the torsional vibration transfer matrix; establishing a point transfer matrix of coordinate transformation at the connection points of each section of the straight beam through force balance conditions and displacement coordination conditions; according to the spatial continuum transfer matrix of the straight beam and the point transfer matrix of coordinate transformation Overlap the transfer matrix from a single crank to the entire crankshaft system; construct the dynamic equation based on the transfer matrix from a single crank to the entire crankshaft system; calculate the natural frequency of the crankshaft system based on the dynamic equation; load the spectrum of the excitation force on the crankpin of the crankshaft system, and use the Newmark-β method to solve the forced vibration response of any point on the crankshaft; the three-dimensional coupled vibration actually exists through shaft vibration, which increases the accuracy of simulation calculation; based on the continuum vibration theory, the time domain signal of the forced vibration response of any part of the crankshaft can be extracted to ensure the integrity of the calculation; use the state parameters such as the crankshaft geometric dimensions to directly simplify, the calculation time is short, the calculation accuracy is controllable, and it has good versatility and engineering applicability.

[0027] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 A flow chart of a method for quickly calculating the vibration response of a diesel engine shaft system provided in the first embodiment of the present invention;

[0031] FIG2( a ) is a schematic diagram of a crank model provided in Embodiment 1 of the present invention;

[0032] FIG2( b ) is a schematic diagram of a simplified model of a single crank provided in Embodiment 1 of the present invention;

[0033] FIG2( c ) is a simplified schematic diagram of the crankshaft provided in the first embodiment of the present invention;

[0034] Figure 3 A schematic diagram of a crank-connecting rod mechanism and its force characteristics provided in the first embodiment of the present invention;

[0035] Figure 4 A time domain diagram of a decomposed pressure curve provided in the first embodiment of the present invention;

[0036] FIG5(a) is a schematic diagram of the force and deformation of the xoy surface of a Timoshenko beam microelement provided in the first embodiment of the present invention;

[0037] FIG5( b ) is a schematic diagram of the force and deformation of the xoz surface of a Timoshenko beam microelement provided in the first embodiment of the present invention;

[0038] Figure 6 A schematic diagram of the longitudinal force and deformation of a Timoshenko beam provided in the first embodiment of the present invention;

[0039] Figure 7 A schematic diagram of torsional force and deformation of a Timoshenko beam provided in Embodiment 1 of the present invention;

[0040] Figure 8 A schematic diagram of a spring support provided in Embodiment 1 of the present invention;

[0041] Fig. 9 A schematic diagram of a concentrated mass element provided in Embodiment 1 of the present invention;

[0042] Fig.10 A schematic diagram of the local coordinates of a crank provided in the first embodiment of the present invention;

[0043] Fig.11A schematic diagram of adjacent crank phases provided in Embodiment 1 of the present invention;

[0044] Fig.12 A schematic diagram of a coordinate transformation around the x-axis provided in the first embodiment of the present invention;

[0045] Fig.13 A schematic diagram of local coordinates of a crank at a general position provided in the first embodiment of the present invention;

[0046] Fig.14 A schematic diagram of a double crank model provided in Embodiment 1 of the present invention;

[0047] FIG. 15( a ) is a schematic diagram of the locations of response points provided in Embodiment 1 of the present invention;

[0048] FIG15( b ) is a schematic diagram of a time domain curve of the axial displacement of a response point provided in Embodiment 1 of the present invention;

[0049] Fig.16 A schematic diagram of a fast calculation system for diesel engine shaft system vibration response provided in the second embodiment of the present invention. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] To facilitate understanding of this embodiment, the embodiment of the present invention is described in detail below.

[0052] Embodiment 1:

[0053] Figure 1 A flow chart of a method for quickly calculating the vibration response of a diesel engine shaft system provided in Embodiment 1 of the present invention.

[0054] Reference Figure 1 , the method comprises the following steps:

[0055] Step S101, simplifying the crankshaft system and the forces of the diesel engine to obtain a simplified model of the diesel engine; wherein the simplified model of the diesel engine includes an excitation force;

[0056] Step S102, based on the straight beam unit, respectively establish the lateral vibration transfer matrix, longitudinal vibration transfer matrix and torsional vibration transfer matrix of the straight beam;

[0057] Step S103, calculating the space continuum transfer matrix of the straight beam according to the lateral vibration transfer matrix, the longitudinal vibration transfer matrix and the torsional vibration transfer matrix;

[0058] Step S104, establishing a point transfer matrix for coordinate transformation at the connection points of each straight beam section through force balance conditions and displacement coordination conditions;

[0059] Step S105, overlapping the transfer matrix of a single crank to the entire crankshaft system according to the spatial continuum transfer matrix of the straight beam and the point transfer matrix of the coordinate transformation;

[0060] Step S106, constructing a dynamic equation according to the transfer matrix from a single crank to the entire crankshaft system;

[0061] Step S107, calculating the natural frequency of the crankshaft system according to the dynamic equation;

[0062] Step S108, loading a spectrum of the excitation force on the crank pin of the crankshaft system, and solving the forced vibration response of any point on the crankshaft using the Newmark-β method.

[0063] Further, referring to the crank model schematic diagram shown in FIG2(a); FIG2(b) is a schematic diagram of a simplified single crank model; FIG2(c) is a simplified schematic diagram of the crankshaft as a whole; step S101 includes the following steps:

[0064] Step S201, simplifying the crankshaft into a spatial structure in which multiple straight beams are overlapped with each other;

[0065] Step S202, simplify the crank connecting rod and the piston into the excitation force:

[0066] Step S203, simplifying the crank arm, crank pin and main journal into a uniform beam structure with equal cross-section;

[0067] Here, based on the crankshaft drawing of a five-cylinder diesel engine, the crank arm, crank pin and main journal are simplified into a uniform beam structure with equal cross-section.

[0068] Step S204, simplifying the bearing into a three-way spring structure;

[0069] Step S205, simplifying the flywheel into a concentrated mass structure;

[0070] The excitation force includes: the force F generated by the gas pressure generated by the cylinder ignition acting on the upper surface of the piston 气 , the reciprocating inertia force F generated by the reciprocating motion of the piston group 往 And acts on the piston, and when the piston moves, it is given a lateral thrust F by the inner wall of the cylinder 侧 , and the centrifugal inertia force F generated when the crankshaft rotates 离 And acts on the crank pin.

[0071] Specifically, the state parameter table of the simplified diesel engine model is shown in Table 1.

[0072] Table 1

[0073]

[0074]

[0075] Identify the various sources of excitation forces in diesel engines. Figure 3 The crank-connecting rod mechanism shown is a framework for analyzing the excitation of the crankshaft when the diesel engine is running.

[0076] After comprehensively considering and synthesizing the above exciting forces, they are decomposed along the tangential and normal directions to obtain the tangential and normal pressure curves of the first cylinder under the rated working condition (74rpm) (the pressure curves of the other cylinders are recursively obtained by the ignition sequence 1-4-3-2-5 and the ignition interval angle 0.0-216.0-144.0-72.0-288.0) as shown in the figure. Figure 4 shown.

[0077] Further, step S102 includes the following steps:

[0078] Step S301, obtaining the inertial force and inertial moment acting on the beam microelement;

[0079] Step S302, obtaining the dynamic equilibrium equation of the beam microelement according to theoretical mechanics;

[0080] Step S303, obtaining the bending moment and shear force on the beam microelement according to material mechanics;

[0081] Step S304, substituting the bending moment and the shear force on the beam microelement into the dynamic equilibrium equation to obtain the lateral vibration differential equation of the beam;

[0082] Step S305, separating the variables in the differential equation of the lateral vibration of the beam to obtain a first set of equations; wherein the variables include the rotation angle generated when the beam is bent and the lateral deformation of the beam microelement;

[0083] Step S306, substituting the excitation into the first set of equations for calculation to obtain a general solution; wherein the general solution includes a plurality of first undetermined constants;

[0084] Step S307, obtaining a solution of the cross-sectional rotation angle; wherein the solution of the cross-sectional rotation angle includes a plurality of second undetermined constants;

[0085] Step S308, substituting the general solution and the solution of the cross-sectional rotation angle into the lateral vibration differential equation of the beam to obtain the relationship between the plurality of first undetermined constants and the plurality of second undetermined constants;

[0086] Step S309, obtaining a bending moment formula and a shear force formula according to material mechanics;

[0087] Step S310, substituting the general solution and the solution of the cross-sectional rotation into the bending moment formula and the shear force formula respectively to obtain an expression between the shear force and the bending moment;

[0088] Step S311, establishing a second set of equations according to the general solution, the solution of the cross-sectional rotation angle, and the expression between the shear force and the bending moment;

[0089] Step S312, converting the second set of equations into a first matrix according to the relationship between the plurality of first undetermined constants and the plurality of second undetermined constants;

[0090] Step S313, calculating a first transfer relationship of state quantities at both ends of the straight beam according to the first matrix;

[0091] Step S314, calculating the lateral vibration transfer matrix of the straight beam in the xoy plane according to the first transfer relationship of the state quantities at both ends of the straight beam.

[0092] Specifically, Figure 5(a) shows the stress and deformation state of the beam element dx when it vibrates laterally in the xoy plane, where Q y is the shear force on the beam element, M z is the bending moment on the beam element, I q is the inertia force on the beam element, I0 is the inertia moment on the beam element, γ is the shear angle caused by shear deformation on the neutral axis of the beam, φ represents the rotation angle when the beam is bent, and y is the lateral deformation of the beam element.

[0093] In order to unify the direction of physical quantities, the positive direction of general mechanics is defined as follows: when the section whose external normal is in the same direction as the x-axis of the infinitesimal element produces a deformation in the same direction as the y-axis and the section whose external normal is opposite to the x-axis produces a deformation in the opposite direction to the y-axis, the shear force Q y is a positive value, otherwise it is a negative value; when the cross section of the infinitesimal element with the same normal direction as the x-axis produces a rotation angle in the same direction as the z-axis, and the cross section with the opposite normal direction to the x-axis produces a rotation angle in the opposite direction to the z-axis, the bending moment M z is positive, otherwise it is negative; the sign of the angle φ produced by the bend is related to the slope Consistent.

[0094] According to Newtonian mechanics, the inertial force I on the beam element is q and the moment of inertia I0 are respectively expressed by formulas (1) and (2):

[0095]

[0096] From the above, we can see that μ s represents the linear density of the beam, I zrepresents the moment of inertia of the microelement cross section of the beam, and ρ represents the volume density of the beam itself.

[0097] According to theoretical mechanics knowledge, the dynamic equilibrium equation of the beam element is shown in formulas (3) and (4):

[0098]

[0099] From material mechanics, we know that:

[0100]

[0101] Substituting formula (5) (6) into formula (3) (4), the differential equation of the lateral vibration of the beam can be obtained after rearrangement:

[0102]

[0103] In the above formula, E represents the Young's modulus of the beam, G represents the shear Young's modulus of the beam, A represents the cross-sectional area of ​​the beam, and k represents the shear correction coefficient. Separating the variables y and φ in formulas (7) and (8) yields the first set of equations.

[0104]

[0105] Assuming that the system is in the same frequency resonance, let y(x, t) = y(x) sinωt, where the symbol ω represents the free vibration circular frequency of the entire beam structure. Next, substitute the excitation y(x, t) into equation (9) to obtain:

[0106] y IV (x)+g 2 y″(x)-a 4 y(x)=0 (11)

[0107] In the formula, g and a are intermediate variables:

[0108]

[0109] Assume y(x) = Ce Sx , substituting into formula (11) we can get:

[0110] S 4 +g 2 S 2 -a 4 =0 (14)

[0111] Solving equation (14), the roots are For convenience, they are represented by λ1 / l and λ2 / l respectively, where l represents the total length of the beam.

[0112]

[0113] To be consistent with the following text, λ1 and λ2 are simplified as follows:

[0114]

[0115] Where:

[0116]

[0117] Substituting the solution obtained by the combined equation into formula (14), the general solution is:

[0118]

[0119] Where C1~C4 are unknown constants. The differential equation (10) satisfied by the cross-sectional rotation angle φ(x, t) is completely consistent with the differential equation (9) satisfied by the lateral displacement form and the lateral displacement y(x, t). Therefore, the solution of the cross-sectional rotation angle φ(x, t) can be set as shown in the following form (23):

[0120]

[0121] In formula (23), B1~B4 represent unknown constants. Formula (22) and formula (23) are not completely independent. Substituting formula (22) and formula (23) into formula (8), using the condition that the coefficients on both sides of the equation are equal, it can be obtained that the coefficients B1~B4 in the solution of the cross-sectional rotation angle φ(x, t) depend on the coefficients C1~C4 in the solution of the lateral displacement φ(x, t). The relationship is shown in formulas (24)~(27).

[0122]

[0123] For simplicity, we assume that the coefficients α and β are:

[0124]

[0125] Then the relationship between B1~B4 and C1~C4 can be simplified as formula (30):

[0126] B1=-αC1, B2=αC2, B3=βC3, B4=βC4 (30)

[0127] According to the calculation formula of bending moment and shear force in material mechanics:

[0128]

[0129] Substituting (22) and (23) into the bending moment formula (31) and shear force formula (32) of material mechanics, we can obtain the shear force M z and bending moment Q y The expressions of are shown in (33) and (34):

[0130]

[0131] Combining equations (22), (23), (33) and (34), we can establish the second set of equations (35):

[0132]

[0133] By using the relationship (30) between coefficients B1~B4 and C1~C4, coefficients B1~B4 can be eliminated, and equation group (35) can be written into the first matrix form shown in (36) below:

[0134]

[0135] in:

[0136]

[0137] For a straight beam with a length of l, after substituting the coordinates of its left and right ends (x = 0 and x = l) into formula (36) respectively and eliminating the unknown constants C1~C4, the transfer relationship of the state quantities at both ends of the straight beam can be obtained as shown in formula (37):

[0138]

[0139] Take T xoy =M xoy (l)M xoy (0) -1 , which is the lateral vibration transfer matrix of the straight beam in the xoy plane.

[0140] Further, step S102 includes the following steps:

[0141] Step S401, constructing a third program group;

[0142] Step S402, converting the third equation group into a second matrix according to the relationship between the plurality of first undetermined constants and the plurality of second undetermined constants;

[0143] Step S403, calculating a second transfer relationship of state quantities at both ends of the straight beam according to the second matrix;

[0144] Step S404, calculating the lateral vibration transfer matrix of the straight beam in the xoz plane according to the second transfer relationship of the state quantities at both ends of the straight beam.

[0145] Specifically, Figure 5(b) shows the stress and deformation state of the beam element dx when it vibrates laterally in the xoz plane, where Q z is the shear force on the beam element, M y is the bending moment on the beam element, I qis the inertial force on the beam microelement, I0 is the inertial moment on the beam microelement, β is the shear angle caused by shear deformation on the neutral axis of the beam, represents the rotation angle produced when the beam is bent, and z is the lateral deformation of the beam element.

[0146] In order to unify the direction of physical quantities, the positive direction of the straight beam in the xoz plane is still defined by general mechanics: when the section whose external normal is in the same direction as the x-axis of the infinitesimal element is deformed in the same direction as the z-axis and the section whose external normal is opposite to the x-axis is deformed in the opposite direction to the z-axis, the shear force Q z is a positive value, otherwise it is a negative value; when the cross section of the infinitesimal element with the same external normal as the x-axis produces a rotation angle in the same direction as the y-axis, and the cross section with the opposite external normal to the x-axis produces a rotation angle in the opposite direction to the y-axis, the bending moment M y is a positive value, otherwise it is a negative value; the angle produced by the bend The sign of It should be noted that according to Figure 5(b), due to the rotation angle The direction is opposite to the y-axis, and the bending moment M y The angle generated when the will be a negative value. Therefore, when considering the lateral vibration of the Timoshenko beam in the xoz plane, the relationship between the rotation angle and the bending moment is different from the formula (5) for the lateral vibration in the xoy plane, and should be as shown in formula (38):

[0147]

[0148] Where I y is the moment of inertia of the cross section of the straight beam about the y-axis.

[0149] Based on the Timoshenko beam theory and its related assumptions, the third equation group similar to formula (35) can be obtained according to the same derivation method as the in-plane lateral vibration of xoy, as shown in formula (39):

[0150]

[0151] According to the relationship (30), the equation group (39) can be written into the second matrix form shown in (40):

[0152]

[0153] in:

[0154]

[0155] For a straight beam with a length of l, the coordinates of its two ends (x = 0 and x = l) can be substituted into (41) respectively, and the unknown constants C1~C4 can be eliminated to obtain the relationship between the state quantities at both ends of the straight beam, as shown in formula (42):

[0156]

[0157] Let T xoz =M xoz (l)M xoz (0) -1 , which is the transfer matrix of the lateral vibration of the straight beam in the xoz plane.

[0158] Further, step S102 includes the following steps:

[0159] Step S501, obtaining the longitudinal vibration equation of the straight beam unit;

[0160] Step S502, using the separation of variables method to separate the variables of the longitudinal vibration equation and calculate the expression of the axial force;

[0161] Step S503, converting the expression of the axial force into a third matrix;

[0162] Step S504, calculating the longitudinal vibration transfer matrix of the straight beam according to the third matrix.

[0163] Specifically, according to Figure 6 The longitudinal force and deformation diagram of the Timoshenko beam shown in the figure is to take a microelement with a length of dx from the distance x from the coordinate origin of the straight axis, and analyze the force state of the microelement: let the unit volume mass of the straight axis be ρ, the cross-sectional area be Α, the longitudinal displacement (displacement along the x direction) at the cross section be u, and the axial force be N. According to the positive and negative regulations of the axial force direction in general mechanics: let the axial force on the microelement be positive when it is in the same direction as the normal line outside the cross section.

[0164] The longitudinal vibration equation of the straight beam element is:

[0165]

[0166] Where E is the elastic modulus, ρ is the density, and u is the longitudinal displacement. The separation of variables method is used to separate u:

[0167] u(x,t)=U(x)sin(ωt) (44)

[0168] You can get:

[0169] U(x)=Ccos(βx)+Dsin(βx) (45)

[0170]

[0171] Find the expression for the axial force N:

[0172] N(x)=EAU'(x)=EA(-βsin(βx)+βcos(βx)) (47)

[0173] Expressed in the third matrix form:

[0174]

[0175] For the left end point of a straight beam when x=0:

[0176]

[0177] For the right end point of a straight beam when x=l:

[0178]

[0179] According to formula (49), (50), eliminating constants C and D, we can obtain:

[0180]

[0181] The longitudinal vibration transfer matrix is ​​obtained as:

[0182]

[0183] Further, step S102 includes the following steps:

[0184] Step S601, obtaining a torsional vibration equation of a straight beam unit;

[0185] Step S602, using the separation of variables method to separate the variables of the torsional vibration equation and calculate the torque of the torsional vibration;

[0186] Step S603, converting the torque of the torsional vibration into a fourth matrix;

[0187] Step S604: Calculate the torsional vibration transfer matrix of the straight beam according to the fourth matrix.

[0188] Specifically, according to Figure 7 The torsional force and deformation diagram of the Timoshenko beam is shown in Figure 1. Assume that the polar moment of inertia of the cross section of the shaft segment is I p , the symbols of other material and size parameters are the same as those in the longitudinal vibration section. The torsion angle around the axis of the axis, that is, the x-direction, at the cross section is θ, and the torque is T. According to the symbol regulations of general mechanics: According to the right-hand screw rule, when the torque vector and the outer normal of the cross section are in the same direction, the sign is positive.

[0189] The torsional vibration equation of the straight beam element is:

[0190]

[0191] Where G is the shear Young's modulus of the material, ρ is the density, θ is the torsion angle, and I p is the equivalent polar moment of inertia of the cross section, I y ,I z are the moments of inertia of the cross section about the y-axis and the z-axis respectively. The separation of variables method is used to separate the variables of θ:

[0192] θ(x,t)=θ(x)sin(ωt) (54)

[0193] You can get:

[0194] Θ(x)=A s cos(αx)+B s sin(αx) (55)

[0195]

[0196] Find the expression for the torque T of torsional vibration:

[0197]

[0198] Expressed in the fourth matrix form:

[0199]

[0200] For the left end point of a straight beam when x=0:

[0201]

[0202] For the right end point of a straight beam when x=l:

[0203]

[0204] According to formulas (60) and (61), the constant A is eliminated. s , B s ,get:

[0205]

[0206] The torsional vibration transfer matrix is ​​obtained as:

[0207]

[0208] It is worth noting that the polar moment of inertia I of the circular cross-section beam is P =π(D 4 -d 4 ) / 32,I y =I z =π(D 4 -d4 ) / 64, satisfying I P =I y +I z For a rectangular cross-section beam, the cross section no longer remains flat after torsion, but warps. The relationship between the polar moment of inertia and the moment of inertia is: P =I y +I z No longer valid, should be corrected to I P =β n hb 3 (h and b represent the long side and short side of the rectangular cross section respectively), coefficient β n It is related to the cross-section side length ratio h / b, and its value is shown in Table 2. The coefficient β of the torsion of the rectangular cross-section rod n .

[0209] Table 2

[0210]

[0211] The motion of the straight beam element includes axial motion, torsional motion, xoz lateral motion and xoy lateral motion. According to the variables set in the above lateral, longitudinal, torsional force and deformation state analysis, the overall state variables of the straight beam element are:

[0212]

[0213] Furthermore, step S103 includes:

[0214] The spatial continuum transfer matrix of the straight beam is calculated according to formula (64):

[0215]

[0216] Where G is the spatial continuum transfer matrix of the straight beam, T xoy is the lateral vibration transfer matrix of the straight beam in the xoy plane, T xoz is the lateral vibration transfer matrix of the straight beam in the xoz plane, T x is the longitudinal vibration transfer matrix of the straight beam, T tor is the torsional vibration transfer matrix of the straight beam.

[0217] The transfer relationship between the left and right sides of the straight beam can be expressed as:

[0218] S i+1 =G i S i (65)

[0219] In the crankshaft system, common components include flywheel, axial vibration damper and bearing support. When the flywheel rotates at high speed, it can store energy and release energy to make the engine run smoothly; the function of the diesel engine axial vibration damper is to reduce the longitudinal movement of the crankshaft; the diesel engine main bearing plays the role of supporting the crankshaft to ensure that the crankshaft operates under normal conditions and outputs power. The axial vibration damper and the bearing support can be equivalent to elastic supports, and the flywheel can be equivalent to a concentrated mass regardless of its shape and motion state. The axial vibration damper is equivalent to a single-degree-of-freedom axial spring, and the bearing support is equivalent to a three-way spring. According to the force balance condition in material mechanics, the transfer matrix of the elastic support and the concentrated mass is obtained.

[0220] The simplified schematic diagram of the elastic support is as follows Figure 8 Assume that the spring stiffness in the x, y, and z directions is k x ,k y ,k z , the force balance equation on the left and right sides of the spring can be expressed as:

[0221] N R -N L -k x u=0 (66)

[0222]

[0223] It is expressed in matrix form as:

[0224]

[0225] Schematic diagram of concentrated mass element Fig. 9 As shown. Assuming the mass of the concentrated mass is m, the force balance equation on the left and right sides of the concentrated mass is expressed as:

[0226] N R -N L +mω 2 u=0 (70)

[0227]

[0228] It can be expressed in matrix form as:

[0229]

[0230] Since the local coordinate system is defined on the straight beam element of the crankshaft, and the transfer matrix of each element is derived based on the local coordinate system, the local coordinates of different beams need to be transformed. This method adopts the more classic Euler angle coordinate transformation method, and the transfer matrix obtained by the coordinate transformation is called the point transfer matrix of the coordinate transformation.

[0231] In each local coordinate system, the x-axis coincides with the centerline of the straight beam. Fig.10 It shows the transformation of the local coordinate system of a crank. A single crank is simplified into a 5-segment beam structure, and the local coordinates of each beam are shown in the figure. In the coordinate transformation of a single crank, the local coordinates are mainly rotated around the z-axis by a specific angle to achieve the transformation effect.

[0232] Fig.10 In cases 1 and 4, the coordinate transformation relationship is:

[0233] x 2(5) →y 1(4) ,y 2(5) →-x 1(4) , z 2(5) →z 1(4) (74)

[0235] The transformation relationship of the state vector is:

[0236]

[0237] N 2(5) →Q y1(4) , Q y2(5) →-N 1(4) , T 2(5) →M z1(4) , M z2(5) →-T 1(4) (76)

[0238] From this, the coordinate transformation transfer matrix in cases 1 and 4 can be derived:

[0239]

[0240] In cases 2 and 3, the coordinate transformation relationship is:

[0241] x 3(4) →-y 2(3) ,y 3(4) →x 2(3) , z 2(3) →z 3(4) (78)

[0242] The transformation relationship of the state vector is:

[0243] u 3(4) →-y 2(3) ,y 3(4) →u 2(3) ,θ 3(4) →φ 2(3) ,φ 3(4) →θ 2(3) (79)

[0244] N3(4) →-Q y2(3) , Q y3(4) →N 2(3) , T 3(4) →-M z2(3) , M z3(4) →T 2(3) (80)

[0245] From this, the point transfer matrix in cases 2 and 3 can be derived:

[0246]

[0247] In the adjacent crank coordinate transformation, the angle between two adjacent cranks is β. Since the center lines of the crankshaft cranks are the same, the x-axis remains unchanged. The local coordinate system of the right crank is formed by rotating the local coordinate system of the left crank around the x-axis by an angle of β. The transformation relationship of the coordinate system is as follows: Fig.11 and Fig.12 shown.

[0248] The coordinate transformation relationship is:

[0249] y′=z·sinβ+y·cosβ (82)

[0251] z′=z·cosβ-y·sinβ

[0252] (83)The transformation relationship of the state vector is:

[0253]

[0254] From this, the point transfer matrix of the phase transformation of adjacent cranks can be derived, also called the coordinate transformation point transfer matrix of the local coordinates rotated around the x-axis by an arbitrary angle β as shown in (86).

[0255]

[0256] This method uses the transfer matrix of the straight beam unit, the crankshaft basic original and the spatial structure coordinate transformation to overlap into the transfer matrix of the single crankshaft, and then overlaps into the transfer matrix of the entire crankshaft system. The detailed steps are as follows:

[0257] (1) Transfer matrix overlap of single crank

[0258] The local coordinate selection method for a single crank is as follows: the x-axis is always in the length direction of the straight beam unit, the y-axis on the main journal is always vertically upward, and the y-axis on the crank arm and crank pin is along the direction of vibration within the crank plane. Finally, the z-axis direction is selected according to the right-hand rule. The local coordinate system directions on the main journals of cranks in different relative positions are exactly the same, but the local coordinate system directions on the crank arms and crank pins are different.

[0259] Fig.13The local coordinate diagram of the general position of the bend is given, and the selection method of its local coordinate system is given. For the bend in the general position (relative rotation angle is β), if the transfer matrices of the 5 straight beam elements it contains have been calculated, they are T i (i=1,..5) The transfer matrix between the first and last state vectors is:

[0260] T 单曲拐 (β) = T5H x (-β)H S T4H N T3H N T2H S H x (β)T1 (87)

[0261] (2) Transfer matrix overlap of multi-bellows system

[0262] The actual crankshaft system is composed of multiple cranks. The general multi-crankshaft (here double crankshafts are used as an example to show the matrix overlap formula) model is as follows: Fig.14 In the actual crankshaft model, there is often an elastic support at the main journal connecting different cranks. In this case, the elastic support can be used as an example to divide the two sides into different cranks. In the double crank model, if the transfer matrices of the two cranks are known to be T1 and T2 respectively, the transfer matrix of the middle elastic support is T k When , the transfer matrix of the head and tail state vectors of the double crank system should be:

[0263] T 双曲拐 =T2T k T1 (88)

[0264] The above transfer matrix is ​​used to construct the dynamic equation of the system through its continuous multiplication. The spatial transfer matrix of the beam unit is called the field transfer matrix, the coordinate transformation transfer matrix is ​​called the point transfer matrix, the bearing transfer matrix is ​​called the spring point transfer matrix, and the flywheel transfer matrix is ​​called the concentrated mass point transfer matrix. Assume that the overall state variable of the crankshaft is:

[0265]

[0266] Starting from the crank pin, construct the field transfer matrix of the first beam section, then multiply it by the first spring point transfer matrix, and then multiply it by the field transfer matrix of the second beam section, and continue multiplying, so that the state vector transfer equation of the entire crankshaft is constructed, as shown below:

[0267] S 右 =[T] 左-右 S 左 (90)

[0268] The simplified model parameters of the crankshaft system obtained in step 1 are input into the constructed dynamic equations by programming methods for numerical analysis.

[0269] Further, step S107 includes the following steps:

[0270] Step S701, substituting the boundary conditions on the left and the boundary conditions on the right into the dynamic equations, and extracting a homogeneous linear equation system;

[0271] Step S702, obtaining the natural frequency of the crankshaft system based on the necessary and sufficient conditions for non-zero solutions in the homogeneous linear equations;

[0272] Among them, the necessary and sufficient condition for a non-zero solution is that the value of the coefficient determinant is zero.

[0273] Specifically, the boundary conditions at both ends are substituted into the system dynamics equations, and the homogeneous equations are extracted and combined into a new set of equations. Based on the sufficient and necessary condition that the homogeneous linear equations have non-zero solutions, the value of the coefficient determinant is zero, and the natural frequency of the crankshaft system can be obtained:

[0274] For basic boundary conditions on the left and right sides, 6 of the 12 components of the state vectors on both sides will be zero, and the remaining 6 will be non-zero, for example:

[0275]

[0276] F=[NT M y Q z M z Q y ] T = 0, free boundary

[0277] Substitute the boundary conditions at the left and right ends into the system dynamics equation, extract the homogeneous equations and combine them into a new set of equations. From the knowledge of linear algebra, we know that the necessary and sufficient condition for a homogeneous linear equation to have a non-zero solution is that the value of the coefficient determinant is zero. From this, we can get the natural frequency of the system. For example, for the boundary conditions with the left end fixed and the right end free: the left boundary has X=0F≠0 and the right boundary has X≠0F=0, the original equation can be processed to get the following homogeneous linear equation:

[0278] 0 = F 右 =[T] 子式 F 左 (92)

[0279] Among them, [T] 子式It is a sub-formula formed by extracting some rows and columns from the state vector transfer matrix on the left and right sides of the original system. For the boundary conditions of the fixed left end and free right end in this example, it is obvious that the 2nd, 4th, 7th, 8th, 11th, 12th rows and 2nd, 4th, 7th, 8th, 11th, 12th columns should be extracted. According to the knowledge of linear algebra, the necessary and sufficient condition for the homogeneous linear equation system to have a non-zero solution is that the determinant of the coefficient matrix is ​​0, and [T] 子式 The determinant of is a single-valued function of the assumed harmonic vibration frequency ω, so the natural frequency of the system is such that [T] 子式 The value of ω for which the determinant is 0.

[0280] And fill the non-zero solution of the equation into the state vector S on the left 左 In the non-zero terms of , combined with the multiplication of the transfer matrix, the state vector value of any point on the crankshaft can be determined by continuous multiplication of the transfer matrix, and the state vectors of all points on the crankshaft can be extracted. Further, the vibration modes of each order of the system can be obtained. n (x).

[0281] According to the exciting force spectrum loaded on the crank pin, the Newmark-β method is used to solve the forced vibration response of any point on the crankshaft.

[0282] This method uses generalized coordinates to describe the dynamic equation of the crankshaft system by the second-order Lagrangian equation, and decomposes the real displacement of each point into the superposition of each order modal vibration mode, as shown in the following formula:

[0283]

[0284] Among them, q n (t) corresponds to the nth mode X n The generalized coordinates of (x) are also called modal coordinates. Solving the generalized coordinates can obtain the displacement time domain response of any point in the crankshaft system. The Lagrange equation of the crankshaft system in generalized coordinates is as follows:

[0285]

[0286] To solve equation (94), we need to first calculate the kinetic energy T and potential energy V of the system, as well as the generalized forces Q of each order. n expression.

[0287] Assuming that the vibration mode functions of each order of the crankshaft system have been obtained in the free vibration link, the specific expression is: The longitudinal vibration mode function is U n (x), the torsional vibration function is Θ n (x), is the xz lateral vibration displacement mode function is Z n (x), the bending angle vibration mode function is The xy lateral vibration displacement mode function is Y n (x), the bending angle vibration function is φn (x) The kinetic energy T and potential energy V of the entire system can be listed as follows:

[0288]

[0289] Substitute the kinetic energy and potential energy equations of the system into the second-order Lagrange equations, and define the modal mass and modal stiffness of each order as follows:

[0290]

[0291] Substituting the expressions (97) of modal mass and modal stiffness into the Lagrange equation (94), the equation can be simplified to:

[0292]

[0293] According to the knowledge of analytical mechanics, suppose there is a position p in the system i The points are subjected to the spatial forces F ix 、F iy 、F iz and spatial moment M ix 、M iy 、M iz The corresponding generalized coordinate q n The generalized force expression of (t) is shown in (99):

[0294]

[0295] According to the relationship between real displacement and generalized coordinates, we have (100):

[0296]

[0297] Therefore, under the premise of knowing the real external excitation of the system, the generalized force can be expressed as formula (101):

[0298]

[0299] The crankshaft system is a continuous system with infinite natural frequencies and modes. The modal truncation method is used in actual solution. After selecting natural frequencies and modes of sufficient order but finite, the modal mass, modal stiffness and generalized force of each order are calculated in the above way, and the generalized coordinate q is obtained. n The second-order linear differential equation (102) of (t) can be solved using the Newmark-β method.

[0300]

[0301] Where N is the selected natural frequency and the maximum order of the mode.

[0302] The natural frequencies of the longitudinal and torsional vibration modes obtained by the continuum method are compared with those of the concentrated mass method, and the results are shown in Table 3.

[0303] Table 3

[0304]

[0305] The longitudinal-torsional coupling calculation results of the concentrated mass method only calculated the first five natural frequencies including longitudinal vibration and torsional vibration. The first five orders of longitudinal vibration and torsional vibration in the results of this method (the results show 1st, 4th, 7th, 9th, and 10th orders) were compared with them. From the comparison results, it can be seen that the calculation results of the natural frequencies of the continuum method are not much different from those of the concentrated mass method. At the same time, this report calculates the lateral vibration natural frequencies that are not taken into account in the MAN report, which improves the integrity of the free vibration calculation.

[0306] A point at the front end of the crankshaft is taken as the response point to extract the forced vibration response, and the 0-15s time domain signal is obtained as shown in Figure 15.

[0307] Compared with the prior art, this application has the following advantages:

[0308] 1) For the convenience of calculation in engineering, the vibration of the shaft system was previously calculated separately in the form of bending, longitudinal and torsional vibrations without affecting each other. This method takes into account the three-dimensional coupled vibration of the crankshaft vibration, which increases the accuracy of the simulation calculation.

[0309] 2) The discrete method for calculating the overall crankshaft system of a diesel engine simplifies each part of the crankshaft into concentrated mass for calculation, which cannot fully reflect the overall structure of the crankshaft. This method is based on the continuum vibration theory and can extract the time domain signal of the forced vibration response of any part of the crankshaft, emphasizing the calculation integrity.

[0310] 3) The calculation of diesel engine crankshaft vibration using the finite element method requires complex and time-consuming model construction and mesh division. This method directly simplifies the state parameters such as the crankshaft geometric dimensions and inputs them into the program compiled by MATLAB. The calculation time is short, the calculation accuracy is controllable, and it has good versatility and engineering applicability.

[0311] Embodiment 2:

[0312] Fig.16 A schematic diagram of a fast calculation system for diesel engine shaft system vibration response provided in the second embodiment of the present invention.

[0313] Reference Fig.16 The system comprises:

[0314] A simplification module is used to simplify the crankshaft system and the forces of the diesel engine to obtain a simplified model of the diesel engine; wherein the simplified model of the diesel engine includes an excitation force;

[0315] The first establishment module is used to establish the lateral vibration transfer matrix, the longitudinal vibration transfer matrix and the torsional vibration transfer matrix of the straight beam based on the straight beam unit;

[0316] A first calculation module is used to calculate the space continuum transfer matrix of the straight beam according to the lateral vibration transfer matrix, the longitudinal vibration transfer matrix and the torsional vibration transfer matrix;

[0317] The second establishment module is used to establish a point transfer matrix of coordinate transformation at the connection points of each straight beam section through force balance conditions and displacement coordination conditions;

[0318] A connection module, used for connecting a transfer matrix of a single crank to the entire crankshaft system according to the space continuum transfer matrix of the straight beam and the point transfer matrix of the coordinate transformation;

[0319] A building block for constructing the dynamic equations from the transfer matrix of a single crank to the entire crankshaft system;

[0320] A second calculation module is used to calculate the natural frequency of the crankshaft system according to the dynamic equation;

[0321] The solution module is used to load the spectrum of the excitation force on the crankpin of the crankshaft system and solve the forced vibration response of any point on the crankshaft using the Newmark-β method.

[0322] An embodiment of the present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the method for rapidly calculating the vibration response of the diesel engine shaft system provided in the above embodiment are implemented.

[0323] An embodiment of the present invention also provides a computer-readable medium having a non-volatile program code executable by a processor, wherein a computer program is stored on the computer-readable medium, and when the computer program is executed by the processor, the steps of the method for rapidly calculating the vibration response of the diesel engine shaft system of the above embodiment are executed.

[0324] The computer program product provided in the embodiment of the present invention includes a computer-readable storage medium storing program code. The instructions included in the program code can be used to execute the method described in the previous method embodiment. The specific implementation can be found in the method embodiment and will not be repeated here.

[0325] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system and device described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0326] In addition, in the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0327] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.

[0328] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are 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 limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0329] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A fast calculation method for diesel engine shaft vibration response, characterized in that: The method comprises: Simplifying the crankshaft system and the forces of the diesel engine to obtain a simplified model of the diesel engine; wherein the simplified model of the diesel engine includes an excitation force; Based on the straight beam unit, the lateral vibration transfer matrix, longitudinal vibration transfer matrix and torsional vibration transfer matrix of the straight beam are established respectively; Calculating the space continuum transfer matrix of the straight beam according to the lateral vibration transfer matrix, the longitudinal vibration transfer matrix and the torsional vibration transfer matrix; A point transfer matrix for coordinate transformation at the connection points of the straight beams of each section is established through force balance conditions and displacement coordination conditions; A transfer matrix of a single crank to the entire crankshaft system is overlapped according to the spatial continuum transfer matrix of the straight beam and the point transfer matrix of the coordinate transformation; Constructing dynamic equations based on the transfer matrix from the single crank to the entire crankshaft system; Calculating the natural frequency of the crankshaft system according to the dynamic equation; The spectrum of the excitation force is loaded on the crank pin of the crankshaft system, and the forced vibration response of any point on the crankshaft is solved using the Newmark-β method.

2. The fast calculation method of diesel engine shaft vibration response according to claim 1 is characterized in that: The crankshaft system and forces of the diesel engine are simplified to obtain a simplified model of the diesel engine, including: The crankshaft is simplified into a spatial structure with multiple straight beams overlapping each other; Simplify the crankshaft and piston to the excitation force: The crank arm, crank pin and main journal are simplified into uniform beam structures with equal cross-section; Simplify the bearing into a three-way spring structure; Simplify the flywheel into a concentrated mass structure; Among them, the excitation force includes: the force generated by the gas pressure generated by the ignition of the cylinder acting on the upper surface of the piston, the reciprocating inertia force generated by the reciprocating motion of the piston group and acting on the piston, the lateral thrust given by the inner wall of the cylinder when the piston moves, and the centrifugal inertia force generated when the crankshaft rotates and acts on the crank pin.

3. The fast calculation method of diesel engine shaft vibration response according to claim 1 is characterized in that: Based on the straight beam unit, the lateral vibration transfer matrix, longitudinal vibration transfer matrix and torsional vibration transfer matrix of the straight beam are established respectively, including: Obtain the inertial force and inertial moment acting on the microelement of the beam; Obtaining the dynamic equilibrium equation of the beam microelement according to theoretical mechanics; Obtaining the bending moment and shear force of the beam microelement according to material mechanics; Substituting the bending moment and the shear force of the beam microelement into the dynamic equilibrium equation to obtain the lateral vibration differential equation of the beam; Separating the variables in the differential equation of the lateral vibration of the beam to obtain a first set of equations; wherein the variables include the rotation angle generated when the beam is bent and the lateral deformation of the beam microelement; Substituting the excitation into the first set of equations for calculation to obtain a general solution; wherein the general solution includes a plurality of first undetermined constants; Obtaining a solution of a cross-sectional rotation angle; wherein the solution of the cross-sectional rotation angle includes a plurality of second undetermined constants; Substituting the general solution and the solution of the cross-sectional rotation angle into the lateral vibration differential equation of the beam to obtain the relationship between the plurality of the first undetermined constants and the plurality of the second undetermined constants; Obtain the bending moment formula and shear force formula based on material mechanics; Substituting the general solution and the solution of the cross-sectional rotation angle into the bending moment formula and the shear force formula respectively, to obtain an expression between shear force and bending moment; Establishing a second set of equations according to the general solution, the solution of the cross-sectional rotation angle, and the expression between the shear force and the bending moment; According to the relationship between the first undetermined constants and the second undetermined constants, the second set of equations is converted into a first matrix; Calculate a first transfer relationship of state quantities at both ends of the straight beam according to the first matrix; The lateral vibration transfer matrix of the straight beam in the xoy plane is calculated according to the first transfer relationship of the state quantities at both ends of the straight beam.

4. The fast calculation method of diesel engine shaft vibration response according to claim 1 is characterized in that: Based on the straight beam unit, the lateral vibration transfer matrix, longitudinal vibration transfer matrix and torsional vibration transfer matrix of the straight beam are established respectively, including: Build a third-party program group; According to the relationship between the plurality of first undetermined constants and the plurality of second undetermined constants, the third equation group is converted into a second matrix; Calculate the second transfer relationship of the state quantities at both ends of the straight beam according to the second matrix; The lateral vibration transfer matrix of the straight beam in the xoz plane is calculated according to the second transfer relationship of the state quantities at both ends of the straight beam.

5. The fast calculation method of diesel engine shaft vibration response according to claim 1 is characterized in that: Based on the straight beam unit, the lateral vibration transfer matrix, longitudinal vibration transfer matrix and torsional vibration transfer matrix of the straight beam are established respectively, including: Obtaining the longitudinal vibration equation of the straight beam unit; The longitudinal vibration equation is separated by a separation of variables method to calculate the expression of the axial force; Convert the expression of the axial force into a third matrix; The longitudinal vibration transfer matrix of the straight beam is calculated according to the third matrix.

6. The fast calculation method of diesel engine shaft vibration response according to claim 1 is characterized in that: Based on the straight beam unit, the lateral vibration transfer matrix, longitudinal vibration transfer matrix and torsional vibration transfer matrix of the straight beam are established respectively, including: Obtaining a torsional vibration equation of the straight beam element; The torsional vibration equation is separated into variables by using a separation of variables method to calculate the torque of the torsional vibration; converting the torque of the torsional vibration into a fourth matrix; The torsional vibration transfer matrix of the straight beam is calculated according to the fourth matrix.

7. The fast calculation method of diesel engine shaft vibration response according to claim 1 is characterized in that: Calculating the spatial continuum transfer matrix of the straight beam according to the lateral vibration transfer matrix, the longitudinal vibration transfer matrix and the torsional vibration transfer matrix includes: The spatial continuum transfer matrix of the straight beam is calculated according to the following formula: Where G is the spatial continuum transfer matrix of the straight beam, T xoy is the lateral vibration transfer matrix of the straight beam in the xoy plane, T xoz is the lateral vibration transfer matrix of the straight beam in the xoz plane, T x is the longitudinal vibration transfer matrix of the straight beam, T tor is the torsional vibration transfer matrix of the straight beam.

8. The fast calculation method of diesel engine shaft vibration response according to claim 1 is characterized in that: Calculating the natural frequency of the crankshaft system according to the dynamic equation includes: Substituting the boundary conditions on the left and the boundary conditions on the right into the dynamic equations, and extracting a homogeneous linear equation system; Based on the necessary and sufficient conditions for non-zero solutions in the homogeneous linear equations, the natural frequency of the crankshaft system is obtained; The necessary and sufficient condition for the non-zero solution is that the value of the coefficient determinant is zero.

9. A fast calculation system for diesel engine shaft vibration response, characterized in that: The system comprises: A simplification module, used for simplifying the crankshaft system and the forces of the diesel engine to obtain a simplified model of the diesel engine; wherein the simplified model of the diesel engine includes an excitation force; The first establishment module is used to establish the lateral vibration transfer matrix, the longitudinal vibration transfer matrix and the torsional vibration transfer matrix of the straight beam based on the straight beam unit; A first calculation module, used for calculating the space continuum transfer matrix of the straight beam according to the lateral vibration transfer matrix, the longitudinal vibration transfer matrix and the torsional vibration transfer matrix; The second establishment module is used to establish a point transfer matrix of coordinate transformation at the connection points of each section of the straight beam through force balance conditions and displacement coordination conditions; A connection module, used for connecting a single crank to the transfer matrix of the entire crankshaft system according to the spatial continuum transfer matrix of the straight beam and the point transfer matrix of the coordinate transformation; A construction module, for constructing a dynamic equation according to a transfer matrix from the single crank to the entire crankshaft system; A second calculation module, used for calculating the natural frequency of the crankshaft system according to the dynamic equation; A solution module is used to load the spectrum of the excitation force on the crank pin of the crankshaft system and solve the forced vibration response of any point on the crankshaft by using the Newmark-β method.

10. An electronic device comprising a memory and a processor, wherein the memory stores a computer program that can be run on the processor, wherein: When the processor executes the computer program, the method according to any one of claims 1 to 8 is implemented.

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