Diesel generating set coupling matching method based on closed-loop crankshaft kinetic model

Abstract

The invention discloses a diesel generating set coupling matching method based on a closed-loop crankshaft dynamical model, and the method comprises the steps: firstly building a flexible shaft system model, a cylinder excitation model and a load excitation model of a diesel generating set, and combining the three models to form a shaft system torsional vibration closed-loop dynamical model; then establishing a mapping relation between the cylinder excitation torque and the crankshaft torsion angle, correcting the cylinder excitation torque in real time by using the crankshaft torsion angle, and finally simulating the closed-loop dynamical model under different rigidity conditions to obtain an instantaneous rotating speed fluctuation and additional torque change rule of the diesel generating set. Optimal selection of the rigidity of the elastic coupling is realized; according to the technical scheme, the relation between the cylinder excitation and the crankshaft torsion angle is fully considered, the dynamic change process of the cylinder excitation in the crankshaft rotation process can be accurately reflected, the torsional vibration characteristic analysis precision is remarkably improved, and a reliable basis is provided for coupling rigidity parameter optimization.

Description

Technical Field

[0001] This application relates to the technical field of diesel generator sets, and more specifically, to a method for matching couplings of diesel generator sets based on a closed-loop crankshaft dynamics model. Background Technology

[0002] Flexible couplings play an indispensable role in diesel generator sets. Located between the diesel engine and the generator, they transmit the diesel engine's output torque to the generator's input shaft, absorb and dampen vibrations generated during engine operation, ensuring smooth operation of the generator set. This effectively reduces stress and wear in the transmission system, thereby improving the overall performance and extending the generator set's service life.

[0003] However, the stiffness and damping characteristics of flexible couplings can change due to the influence of the external environment. This change can affect the torsional vibration characteristics of the shaft system, leading to deviations in the analysis of the operating status of the diesel generator set.

[0004] Currently, most technologies use the lumped parameter method to simplify the shaft system model and apply excitation to each part of the shaft system to form an open-loop dynamic model of shaft torsional vibration. This model is then used for simulation and to verify the correctness of the stiffness selection of the flexible coupling. This method can reflect the torsional vibration characteristics of the shaft system to a certain extent and support the selection of the stiffness of the flexible coupling. However, this method cannot accurately reflect the real-time changes in the cylinder excitation torque, does not consider the relationship between the excitation of each cylinder and the crankshaft torsional angle, and cannot obtain the accurate excitation torque acting on the shaft system at each moment. Therefore, it cannot reflect the true torsional vibration characteristics of the diesel generator set shaft system. Using this method to simulate and verify the correctness of the stiffness selection of the flexible coupling will yield inaccurate results, which will affect the overall performance and service life of the diesel generator set. Summary of the Invention

[0005] The purpose of this application is to provide a matching method for diesel generator set couplings based on a closed-loop crankshaft dynamics model. First, a closed-loop dynamics model of the torsional vibration of the diesel generator set shaft system is built to more accurately reflect the torsional vibration characteristics of the diesel generator set. Then, the closed-loop coupling characteristics of the diesel generator set are obtained based on the closed-loop dynamics model. Finally, the influence of the stiffness parameter variation of the flexible coupling on the torsional vibration characteristics of the diesel generator set is analyzed, providing a new method for selecting the stiffness of the flexible coupling.

[0006] The technical solution of this application is: a method for matching couplings of a diesel generator set based on a closed-loop crankshaft dynamics model is provided. The diesel generator set includes a diesel engine, a flexible coupling, and a generator. The diesel engine contains a cylinder and a crankshaft. The method includes:

[0007] S1. The lumped parameter method is used to simplify the shaft system of the diesel generator set, forming a lumped parameter model of the shaft system with multiple inertia. Based on the lumped parameter model of the shaft system with multiple inertia and the differential equation of shaft system torsional vibration, a flexible shaft system model of the diesel generator set is built.

[0008] S2, Build a cylinder excitation model for the diesel generator set. The cylinder excitation model includes two parts: gas excitation torque and reciprocating inertial torque. Based on the mapping relationship between the cylinder excitation torque and the crankshaft torsional angular displacement, the gas excitation torque and reciprocating inertial torque are corrected in real time using the actual crankshaft torsional angular displacement to accurately reflect the torsional vibration characteristics of the diesel generator set.

[0009] S3. Based on the rated power, rated speed and rotor speed of the load, build a load excitation model for the diesel generator set.

[0010] S4. Based on the input-output correspondence between the established models, the flexible shaft system model, cylinder excitation model and load excitation model are combined to form a closed-loop dynamic model of torsional vibration of the diesel generator set shaft system.

[0011] S5 sets different stiffness parameters for the flexible coupling and simulates the closed-loop dynamic model of the torsional vibration of the diesel generator set shaft system to obtain the simulation results of the instantaneous speed fluctuation and additional torque of the diesel generator set under different stiffness parameters.

[0012] S6. Determine the optimal matching stiffness parameters of the elastic coupling based on the simulation results.

[0013] Furthermore, S1 specifically includes:

[0014] The differential equation for torsional vibration is expressed as:

[0015] ;

[0016] In the formula, [J] is the moment of inertia matrix, [C] is the damping matrix, and [K] is the stiffness matrix. It is a column vector of angular displacements. This is the column vector of angular velocities. Let {M} be the column vector of angular accelerations, and {M} be the column vector of excitation torques on the axis system.

[0017] The torsional vibration differential equations corresponding to each inertia are established, and each torsional vibration differential equation corresponds to a flexible shaft system module. The flexible shaft system modules are coupled through the relative damping and torsional stiffness parameters of the shaft segments between adjacent inertia to form the flexible shaft system model corresponding to the entire shaft system. The torsional vibration differential equation corresponding to the nth inertia on the shaft system is expressed as:

[0018] ;

[0019] Among them, Mn J is the excitation torque for the nth inertia. n Let C be the rotational inertia of the nth inertia. n For the absolute damping of the nth inertia, C n-1,n For the relative damping of the (n-1)th shaft segment, C n,n+1 K represents the relative damping of the nth shaft segment. n-1,n K is the torsional stiffness of the (n-1)th shaft segment. n,n+1 Let n be the torsional stiffness of the nth shaft segment. Let n be the torsional angular displacement of the nth moment of inertia. angular velocity of the nth inertia Let be the angular acceleration of the nth inertia.

[0020] Furthermore, S2 specifically includes the following steps:

[0021] S201. Based on the tangential force borne by the crank pin in the crankshaft, the expression for the gas excitation torque is derived. The expression for the gas excitation torque is then expanded using Fourier transform, and the known gas harmonic coefficients are substituted to calculate the gas excitation torque.

[0022] S202, the reciprocating inertial torque generated by the reciprocating motion components in the diesel engine is calculated based on the reciprocating mass of the cylinder and the piston acceleration;

[0023] S203, based on the actual crank angle displacement corresponding to each cylinder, corrects the gas excitation torque and reciprocating inertial excitation torque in real time;

[0024] S204 combines the gas excitation torque and reciprocating inertial torque corresponding to each cylinder to obtain the excitation torque of each cylinder of the diesel engine. The excitation torque expressions of each cylinder are combined to form the cylinder excitation model.

[0025] Furthermore, in S201, the tangential force p T Represented as:

[0026] ;

[0027] In the formula, p g The gas pressure acting on the piston is given by α, the crank angular displacement is given by β, and the connecting rod angular displacement is given by β; the tangential force p T The expression, represented using angle α, yields:

[0028] ;

[0029] In the formula, R is the crank radius and L is the connecting rod length;

[0030] The excitation torque generated by the gas is expressed as:

[0031] ;

[0032] In the formula, D is the cylinder diameter; for the tangential force p T The Fourier expansion yields the following expression for the gas excitation torque:

[0033] ;

[0034] In the formula, v is the simple harmonic order, a v b is the cosine component of the tangential force. v C is the sinusoidal component of the tangential force. v Let ψ be the amplitude of the v-th harmonic tangential force. v Let ω be the initial phase angle of the v-th harmonic tangential force, ω be the angular frequency, and t be time; a v With b v Let a be the gas harmonic coefficient, v = 1, 2, ..., 12. Given the known gas harmonic coefficients a... v and b v Substituting this into the expansion of the gas excitation torque, we obtain the gas excitation torque.

[0035] Furthermore, S202 specifically includes: the reciprocating inertial force acting on the crank pin via the connecting rod will cause the crankshaft to undergo torsional vibration, and the reciprocating inertial force is expressed as:

[0036] ;

[0037] In the formula, m is the reciprocating mass of the cylinder. Let be the piston acceleration; where the piston acceleration is approximately expressed as:

[0038] ;

[0039] The reciprocating inertial torque is expressed as:

[0040] ;

[0041] In the formula, λ is the ratio of crank radius to connecting rod length.

[0042] Furthermore, S203 specifically includes:

[0043] For a single flexible shaft system module, the magnitudes of the gas excitation torque and reciprocating inertial torque corresponding to the cylinder when the crank rotates through different angles are first calculated based on the expressions for gas excitation torque and reciprocating inertial torque. Then, the crank rotation angle displacement α corresponding to each flexible shaft system module is obtained in real time. Finally, the actual gas excitation torque and reciprocating inertial torque are corrected in real time based on the calculated gas excitation torque and reciprocating inertial torque.

[0044] Furthermore, the load excitation model in S3 is expressed as:

[0045] ;

[0046] In the formula, M0 is the load excitation torque, N p n is the rated power of the generator. p n is the rated speed of the generator. e This represents the rotor speed of the generator.

[0047] Furthermore, S5 specifically includes:

[0048] The initial stiffness parameters of the flexible coupling are set, and the parameters are adjusted according to a predetermined set of proportions to obtain a set of different stiffness parameters. The different stiffness parameters of the flexible coupling are then substituted into the simulation, and the closed-loop dynamic model of the torsional vibration of the diesel generator set shaft system is simulated to obtain the instantaneous speed fluctuation and additional torque change curves of the diesel generator set shaft system under different stiffness conditions.

[0049] Furthermore, S6 specifically includes: calculating the comprehensive evaluation value corresponding to different stiffness parameters according to preset weights, and selecting the stiffness parameter with the smallest comprehensive evaluation value as the optimal matching stiffness parameter.

[0050] The technical solution of this application also provides a diesel generator set coupling matching system based on a closed-loop crankshaft dynamics model. This system is used to execute the above method and includes:

[0051] The excitation module is used to build the cylinder excitation model and load excitation model of the diesel generator set.

[0052] Flexible shaft system module, used to build a flexible shaft system model of diesel generator set;

[0053] The coupling module is used to combine the models according to the input-output correspondence between the established flexible shaft system model, cylinder excitation model and load excitation model to form a closed-loop dynamic model of torsional vibration of the diesel generator set shaft system.

[0054] The variable parameter analysis module is used to simulate and analyze the closed-loop dynamic model of torsional vibration using the controlled variable method, and obtain the simulation results of instantaneous speed fluctuation and additional torque of diesel generator set under different stiffness parameters.

[0055] The optimization module is used to optimize the selection scheme of the stiffness of the elastic coupling based on the simulation results.

[0056] The beneficial effects of this application are:

[0057] The technical solution in this application first establishes a flexible shaft system model, a cylinder excitation model, and a load excitation model for the diesel generator set. These three models are then combined to form a closed-loop dynamic model of the shaft system torsional vibration of the diesel generator set. In this model, the instantaneous crankshaft torsion angle corresponding to each cylinder is used as a link to establish a mapping relationship between the cylinder excitation torque and the crankshaft torsion angle. The cylinder excitation torque and reciprocating inertial torque are corrected in real time to form a closed-loop feedback between the cylinder excitation characteristics and the crankshaft torsional response. Finally, the closed-loop dynamic model is simulated to obtain the instantaneous speed fluctuation and additional torque variation curves of the diesel generator set under different stiffness conditions. These curves are used to analyze the influence of the stiffness variation of the flexible coupling on the shaft system torsional vibration, thereby achieving the optimized selection of the stiffness parameters of the flexible coupling.

[0058] Existing methods for optimizing stiffness parameters using open-loop dynamics models neglect the relationship between cylinder excitation torque and crankshaft torsion angle, failing to accurately reflect the torsional vibration characteristics of the diesel generator set shaft system and also failing to guarantee the rationality of the stiffness selection for the flexible coupling. Compared to existing methods, the technical solution in this application fully considers the relationship between cylinder excitation and the corresponding crankshaft torsion angle. By correcting the cylinder excitation and coupling it with the flexible shaft system, it can accurately reflect the actual changes in cylinder excitation during crankshaft rotation, significantly improving the accuracy and accuracy of the analysis of torsional vibration characteristics of the diesel generator set. This provides a reliable basis for optimizing coupling stiffness parameters, resulting in more reasonable coupling stiffness matching, effectively suppressing torsional resonance, and improving the operating stability of the shaft system. Attached Figure Description

[0059] The advantages of the above and / or additional aspects of this application will become apparent and readily understood in the description of the embodiments in conjunction with the following drawings, wherein:

[0060] Figure 1 This is a schematic flowchart of a diesel generator set coupling matching method based on a closed-loop crankshaft dynamics model provided in Embodiment 1 of this application;

[0061] Figure 2 This is a structural diagram of the closed-loop dynamic model of the torsional vibration of the shaft system of a diesel generator set according to Embodiment 1 of this application;

[0062] Figure 3 This is a schematic diagram of the simulation value of the total excitation torque (uncorrected) of the cylinder under the initial stiffness parameters of the flexible coupling provided in the example of this application;

[0063] Figure 4 This is a schematic diagram of the simulation value of the total excitation torque of the cylinder (after correction) under the initial stiffness parameters of the elastic coupling provided in Embodiment 1 of this application;

[0064] Figure 5This is a schematic diagram of the simulation value of the additional torque of the coupling under the initial stiffness parameters of the elastic coupling provided in the example of this application.

[0065] Figure 6 This is a schematic diagram of the rotational speed simulation value under the initial stiffness parameters of the flexible coupling provided in the example of this application.

[0066] Figure 7 This is a schematic diagram of the simulation values ​​of the peak-to-peak value relationship curve between the typical stiffness and rotational speed fluctuation of the flexible coupling provided in the example of this application;

[0067] Figure 8 This is a schematic diagram of the simulation value of the relationship curve between the typical stiffness of the flexible coupling and the maximum value of the additional torque of the coupling, based on the example provided in this application.

[0068] Figure 9 This is a schematic diagram of the simulation value of the additional torque of the coupling under the preferred stiffness parameters of the elastic coupling provided in the example of this application;

[0069] Figure 10 This is a schematic diagram of the rotational speed simulation value under the preferred stiffness parameters of the elastic coupling provided in the example of this application.

[0070] Figure 11 This is a schematic diagram of the structure of a diesel generator set coupling matching system based on a closed-loop crankshaft dynamics model, according to Embodiment 2 of this application. Detailed Implementation

[0071] To better understand the above-mentioned objectives, features, and advantages of this application, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

[0072] In the following description, many specific details are set forth in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below.

[0073] Example 1:

[0074] like Figure 1 As shown, this embodiment provides a diesel generator set coupling matching method based on a closed-loop crankshaft dynamics model, including:

[0075] S1. Construct a flexible shaft system model for the diesel generator set. Specifically, the shaft system of the diesel generator set is simplified using the lumped parameter method to form a lumped parameter model of the shaft system with multiple inertia. Based on the lumped parameter model of the shaft system with multiple inertia and the differential equation of torsional vibration of the shaft system, a flexible shaft system model of the diesel generator set is constructed.

[0076] It should be noted that the lumped parameter method is a commonly used engineering analysis method. By simplifying a complex continuous system into a discrete lumped parameter system, it can greatly simplify the calculation process. In this embodiment, the shaft system is divided into multiple inertia, which may include cylinder inertia, flywheel and coupling inertia, and generator rotor inertia. These inertia can accurately reflect the interaction and torque transmission process between the various inertia of each shaft system.

[0077] Based on the lumped parameter model of the shaft system with multiple inertia and the differential equation of shaft system torsional vibration, a flexible shaft system model of the diesel generator set is constructed, specifically including:

[0078] The differential equation for torsional vibration is expressed as:

[0079] ;

[0080] In the formula, [J] is the moment of inertia matrix, [C] is the damping matrix, and [K] is the stiffness matrix. It is a column vector of angular displacements. This is the column vector of angular velocities. Let {M} be the column vector of angular accelerations, and {M} be the column vector of excitation torques on the axis system.

[0081] Torsional vibration differential equations are established for each inertia in the lumped parameter model of the multi-inertia shaft system. Each torsional vibration differential equation corresponds to a flexible shaft system module. The flexible shaft system modules are coupled (i.e., mathematically coupled) through the relative damping and torsional stiffness parameters of the shaft segments between adjacent inertia to form the flexible shaft system model corresponding to the entire shaft system. The torsional vibration differential equation corresponding to the nth inertia in the shaft system is expressed as:

[0082] ;

[0083] Among them, M n J is the excitation torque for the nth inertia. n Let C be the rotational inertia of the nth inertia. n For the absolute damping of the nth inertia, C n-1,n For the relative damping of the (n-1)th shaft segment (i.e., the connection between the (n-1)th and nth moments of inertia), C n,n+1 K represents the relative damping of the nth shaft segment. n-1,n K is the torsional stiffness of the (n-1)th shaft segment. n,n+1 Let n be the torsional stiffness of the nth shaft segment. Let n be the torsional angular displacement of the nth moment of inertia. angular velocity of the nth inertia Let be the angular acceleration of the nth inertia.

[0084] It should be noted that the input to this flexible shaft system model is the excitation torque on the shaft system, including cylinder excitation torque and load excitation torque, and the output is the angular displacement, angular velocity, and angular acceleration corresponding to each moment of inertia. Specifically, the cylinder excitation torque is applied through the inertia of the diesel engine cylinder bank to reflect the power input generated by combustion; the load excitation torque is applied through the inertia of the generator rotor to reflect the electromagnetic resistance or mechanical load at the load end. Each excitation torque acts on its corresponding moment node in the model and is transmitted between the moments of inertia through the torsional stiffness and relative damping parameters of the flexible shaft system, forming the dynamic response of the entire shaft system.

[0085] In this embodiment, inertia refers to a rigid body unit with mass / rotational inertia (such as a flywheel, coupling, generator rotor, etc.), which can be regarded as a node or concentrated mass point in the model and is used to store kinetic energy; shaft segment refers to an elastic element (the material has torsional stiffness and damping) that connects two adjacent inertia, which can be regarded as a connector in the model and is used to transmit torque and provide elasticity and damping, such as the shaft segment between the (n-1)th and the nth inertia.

[0086] S2. Construct a cylinder excitation model for the diesel generator set. This model includes two parts: gas excitation torque and reciprocating inertial torque. Based on the mapping relationship between the cylinder excitation torque and the crankshaft torsional angular displacement, the actual crankshaft torsional angular displacement is used to correct the gas excitation torque and reciprocating inertial torque in real time, accurately reflecting the torsional vibration characteristics of the diesel generator set. Specifically, the steps are as follows:

[0087] S201. Based on the tangential force borne by the crank pin in the crankshaft, the expression for the gas excitation torque is derived. The expression for the gas excitation torque is then expanded using Fourier transform, and the known gas harmonic coefficients are substituted to calculate the gas excitation torque.

[0088] The excitation torque generated by the gas inside the diesel engine cylinder is manifested through the tangential force p borne by the crankpin. T Represented as:

[0089] ;

[0090] In the formula, p g The gas pressure acting on the piston is given by α, the crank angular displacement is given by β, and the connecting rod angular displacement is given by β; the tangential force p T The expression, represented using angle α, yields:

[0091] ;

[0092] In the formula, R is the crank radius and L is the connecting rod length;

[0093] The excitation torque generated by the gas is expressed as:

[0094] ;

[0095] In the formula, D is the cylinder diameter; for the tangential force p T The Fourier expansion yields the following expression for the gas excitation torque:

[0096] ;

[0097] In the formula, v is the simple harmonic order, a v b is the cosine component of the tangential force. v C is the sinusoidal component of the tangential force. v Let ψ be the amplitude of the v-th harmonic tangential force. v Let ω be the initial phase angle of the v-th harmonic tangential force, ω be the angular frequency, and t be time; a v With b v Let v be the gas harmonic coefficients, v = 1, 2, ..., 12 (the gas excitation torque is usually calculated up to the 12th harmonic). Given the known gas harmonic coefficients a... v and b v Substituting this into the expansion of the gas excitation torque, we obtain the gas excitation torque.

[0098] Wherein, the gas harmonic coefficient a v and b v It can be calculated in advance through experiments or simulations, or it can be given from existing diesel engine data sheets (gas harmonic characteristic curves), such as by obtaining the cylinder gas pressure p through actual measurement. g Converted to crank pin tangential force p T Then, the harmonic coefficients α are extracted through Fourier expansion. v and b v .

[0099] It should be noted that the diesel engine and the flexible crankshaft are connected by a piston and a connecting rod. The piston is located in the diesel engine cylinder and is connected to the crankshaft by a crank pin through the connecting rod. The crank pin is usually located between the cranks and is connected to the connecting rod through a pin hole, so that the cranks can rotate or swing around the pin. The crank pin plays a supporting and connecting role, and can also withstand the rotational force from the cranks.

[0100] S202, the reciprocating inertial torque generated by the reciprocating motion component (i.e., piston) of the diesel engine is calculated based on the basic parameters of the diesel engine. The basic parameters include the reciprocating mass of the cylinder and the piston acceleration.

[0101] Specifically, the reciprocating inertial force acts on the crank pin via the connecting rod, causing the crankshaft to torsional vibration. The formula for calculating the reciprocating inertial force generated by the reciprocating moving parts is as follows:

[0102] ;

[0103] In the formula, m is the reciprocating mass of the cylinder. Let be the piston acceleration; where the piston acceleration is approximately expressed as:

[0104] ;

[0105] In the formula, λ is the ratio of crank radius to connecting rod length;

[0106] The reciprocating inertial torque is expressed as:

[0107] ;

[0108] As can be seen from the above expression for the reciprocating inertial torque, the reciprocating inertial torque can be approximated as being composed of four simple harmonic sinusoidal components.

[0109] Step S203: Based on the actual crank angle displacement corresponding to each cylinder, the gas excitation torque and reciprocating inertial excitation torque are corrected in real time.

[0110] Specifically, for a single flexible shaft system module, the magnitudes of the gas excitation torque and reciprocating inertial torque corresponding to the cylinder when the crankshaft rotates through different angles are first calculated based on the gas excitation torque expression and the reciprocating inertial torque expression. Then, the signal of the crank rotation angle displacement α corresponding to each flexible shaft system module is acquired in real time. Finally, the actual gas excitation torque and reciprocating inertial torque are corrected in real time based on the calculated gas excitation torque and reciprocating inertial torque.

[0111] It should be noted that, as can be seen from the expressions for gas excitation torque and reciprocating inertial torque, both cylinder excitation and reciprocating inertial excitation are related to the crankshaft angular displacement α. During crankshaft motion, the angular displacement signals output by each cylinder's single-inertia flexible shaft system module can be received, and the periods of gas excitation and reciprocating inertial excitation can be corrected in real time according to the gas excitation torque and reciprocating inertial torque corresponding to the angular displacement, so as to obtain more accurate real-time cylinder excitation when matching coupling stiffness in the future, thereby improving the coupling stiffness matching accuracy.

[0112] Step S204: Combine the gas excitation torque and reciprocating inertial torque corresponding to each cylinder to obtain the excitation torque of each cylinder of the diesel engine. The excitation force expressions of each cylinder are combined to form the cylinder excitation model.

[0113] The excitation torque of each cylinder in a torque-driven diesel engine is expressed as:

[0114] M k =M g +M I ;

[0115] In the formula, M k M is the excitation torque of a single cylinder.g M is the gas excitation torque. I This is the reciprocating inertial torque.

[0116] S3. Construct a load excitation model for the diesel generator set. Specifically, the load excitation is calculated based on the rated power, rated speed, and rotor speed of the load, and is expressed as follows:

[0117] ;

[0118] In the formula, M0 is the load excitation torque, N p n represents the rated power of the generator in the diesel generator set. p n is the rated speed of the generator. e This represents the rotor speed of the generator.

[0119] S4. Based on the input-output correspondence between the established models, the flexible shaft system model, cylinder excitation model, and load excitation model are combined to form a closed-loop dynamic model of torsional vibration of the diesel generator set shaft system.

[0120] The torsional vibration differential equation corresponding to the nth moment of inertia in the shaft system is expressed as:

[0121] ;

[0122] M n The excitation torque M is the excitation torque for the nth inertia. n Including cylinder excitation torque M k And the load excitation torque M0, the cylinder excitation torque M k The load excitation torque M0 is applied through the inertia of the diesel engine cylinder assembly and through the inertia of the generator rotor (i.e., the load excitation is input through the generator rotor inertia and the cylinder excitation is input through the cylinder inertia).

[0123] S5 involves setting different stiffness parameters for the flexible coupling and simulating the closed-loop dynamic model of the torsional vibration of the diesel generator set shaft system. The simulation results of the instantaneous speed fluctuation and additional torque of the diesel generator set under different stiffness parameters are obtained. Specifically, the steps include:

[0124] Set the initial stiffness parameters of the flexible coupling, and adjust the parameters according to a predetermined set of percentages or proportions (such as 55%, 70%, 85%, 100%, 115%, 130%, 145%) to obtain a set of different stiffness parameters. Substitute the different stiffness parameters of the flexible coupling into the simulation, and simulate the closed-loop dynamic model of the torsional vibration of the diesel generator set shaft system to obtain the instantaneous speed fluctuation and additional torque change curves of the diesel generator set shaft system under different stiffness conditions.

[0125] S6. Determine the optimal matching stiffness parameters of the elastic coupling based on the simulation results.

[0126] Specifically, the comprehensive evaluation value corresponding to different stiffness parameters is calculated according to the preset weights, and the stiffness parameter with the smallest comprehensive evaluation value is selected as the optimal matching stiffness parameter.

[0127] It should be noted that the torsional vibration characteristics of diesel generator sets are affected by the change in coupling stiffness. By adjusting the stiffness parameters using the controlled variable method, the change curves of instantaneous speed fluctuation and additional torque can be obtained. Based on these change curves, the trend of change can be analyzed, and the optimal matching stiffness parameters can be selected.

[0128] Example 2:

[0129] like Figure 11 As shown, this embodiment also provides a diesel generator set coupling matching system based on a closed-loop crankshaft dynamics model, including:

[0130] The excitation module is used to build the cylinder excitation model and load excitation model of the diesel generator set.

[0131] Flexible shaft system module, used to build a flexible shaft system model of diesel generator set;

[0132] The coupling module is used to couple the above models according to the input-output correspondence between the established flexible shaft system model, cylinder excitation model and load excitation model to form a closed-loop dynamic model of torsional vibration of the diesel generator set shaft system.

[0133] The variable parameter analysis module is used to perform simulation analysis on the torsional vibration dynamic model using the controlled variable method, to obtain the instantaneous speed fluctuation and additional torque results of the diesel generator set under different stiffness parameters of the elastic coupling, so as to obtain the influence of the torsional vibration characteristics of the diesel generator set on the change of coupling stiffness, and to compare and obtain the analysis results.

[0134] The optimization module is used to optimize the selection scheme of the stiffness of the elastic coupling based on the simulation results.

[0135] Example:

[0136] Taking a common diesel generator set as an example, the accuracy of the method in this application is verified. The diesel generator set consists of a vibration damper, a diesel engine, a flexible coupling and a generator. The rated speed of the set is 1000 r / min. The initial stiffness parameters of the flexible coupling are shown in Table 1.

[0137] Table 1

[0138]

[0139] Using the flexible coupling stiffness selection method for diesel generator sets that considers cylinder excitation cycle correction proposed in this application, the stiffness parameters of the flexible coupling are optimized and matched to obtain the optimal stiffness selection scheme; for example... Figure 3 As shown, under the initial stiffness selection, the uncorrected total cylinder excitation amplitude is smooth, and the peak values ​​are consistent; as Figure 4 As shown, under the initial stiffness, the total excitation amplitude of the cylinder after correction of the cylinder inertia torsion angle has periodic fluctuations, indicating that the diesel generator set is experiencing self-excited oscillation. The method of this application can effectively capture the actual changes in cylinder excitation, effectively suppress the generation of torsional resonance by correcting the cylinder excitation in real time, improve the running stability of the shaft system, and at the same time improve the accuracy of shaft system torsional vibration characteristic analysis and stiffness parameter matching.

[0140] like Figure 5 As shown, under the initially selected stiffness, the maximum additional torque of the flexible coupling reaches 5.122 kN·m; Figure 6 As shown, under the initial stiffness selection, the diesel generator set speed fluctuation reaches ±7.13 r / min; where the total cylinder excitation and speed are obtained through actual measurement, and the additional torque is calculated based on simulation values ​​and engine parameters; it can be seen that under the initial stiffness parameters of the flexible coupling, the peak value of the additional torque of the coupling and the speed fluctuation of the diesel generator set are relatively large.

[0141] To improve the operational stability of the diesel generator set and reduce the additional torque borne by the flexible coupling, the stiffness of the flexible coupling was optimized according to the proposed method. Using the controlled variable method, the torsional vibration characteristics of the diesel generator set were simulated and analyzed at multiple stiffnesses (55%, 70%, 85%, 100%, 115%, 130%, and 145%) of the initially selected flexible coupling. The peak-to-peak value curves of the speed fluctuation under different flexible coupling stiffnesses are shown below. Figure 7 As shown in the figure, and the curve of the maximum additional torque of the coupling as shown in the figure. Figure 8 As shown, the peak-to-peak value of the rotational speed fluctuation and the maximum value of the additional torque of the coupling under various stiffnesses are plotted in Table 2, as follows:

[0142] Table 2

[0143]

[0144] Based on the results in Table 2, it can be seen that the maximum additional torque and the peak-to-peak speed fluctuation of the coupling change with the stiffness of the coupling. The speed fluctuation initially decreases slightly as the coupling stiffness increases, then increases rapidly when approaching the initial selected stiffness, and then continues to decrease after exceeding the initial selected stiffness. The maximum additional torque gradually increases with increasing stiffness, reaching its maximum value at the initial selected stiffness. Further increasing the stiffness causes the maximum additional torque to first decrease, then increase slowly and tend to stabilize. Based on these analysis results, an initial stiffness of 55% is selected as the final preferred option. The optimized parameters of the elastic coupling are: stiffness 0.344 and damping coefficient 0.7.

[0145] Simulation analysis was performed on the diesel generator set with optimized stiffness of the flexible coupling. The simulation results are as follows: Figure 9 and Figure 10 As shown in the table, the maximum additional torque and speed fluctuation of the flexible coupling decreased significantly. The maximum additional torque of the coupling decreased to 1.133 kN·m, and the speed fluctuation decreased to ±5.84 r / min. The rate of decrease of the maximum additional torque and speed fluctuation of the coupling under the initial and optimized stiffness is shown in Table 4.

[0146] Table 4

[0147]

[0148] Therefore, based on the closed-loop dynamic model of the torsional vibration of the diesel generator set shaft system, this application can more accurately analyze the torsional vibration characteristics of the diesel generator set shaft system. Compared with the open-loop model in the prior art, the technical solution of this application can accurately simulate the actual cylinder excitation, significantly improve the accuracy of torsional vibration analysis and stiffness optimization matching, and provide reliable technical support for the resonance prevention of diesel generator sets.

[0149] The steps in this application can be rearranged, combined, or deleted according to actual needs.

[0150] The units in the device of this application can be merged, divided, or deleted according to actual needs.

[0151] Although this application has been disclosed in detail with reference to the accompanying drawings, it should be understood that these descriptions are merely exemplary and not intended to limit the application of this application. The scope of protection of this application is defined by the appended claims and may include various variations, modifications, and equivalents of the invention without departing from the scope and spirit of this application.

Claims

1. A method for matching couplings in a diesel generator set based on a closed-loop crankshaft dynamics model, the diesel generator set comprising a diesel engine, a flexible coupling, and a generator, wherein the diesel engine contains a cylinder and a crankshaft, characterized in that, The method includes: S1. The lumped parameter method is used to simplify the shaft system of the diesel generator set, forming a lumped parameter model of the shaft system with multiple inertia. Based on the lumped parameter model of the shaft system with multiple inertia and the differential equation of shaft system torsional vibration, a flexible shaft system model of the diesel generator set is built. S2, Build a cylinder excitation model for the diesel generator set. The cylinder excitation model includes two parts: gas excitation torque and reciprocating inertial torque. Based on the mapping relationship between the cylinder excitation torque and the crankshaft torsional angular displacement, the gas excitation torque and reciprocating inertial torque are corrected in real time using the actual crankshaft torsional angular displacement to accurately reflect the torsional vibration characteristics of the diesel generator set. S3. Based on the rated power, rated speed and rotor speed of the load, build a load excitation model for the diesel generator set. S4. Based on the input-output correspondence between the established models, the flexible shaft system model, cylinder excitation model and load excitation model are combined to form a closed-loop dynamic model of torsional vibration of the diesel generator set shaft system. S5 sets different stiffness parameters for the flexible coupling and simulates the closed-loop dynamic model of the torsional vibration of the diesel generator set shaft system to obtain the simulation results of the instantaneous speed fluctuation and additional torque of the diesel generator set under different stiffness parameters. S6. Determine the optimal matching stiffness parameters of the elastic coupling based on the simulation results.

2. The diesel generator set coupling matching method based on a closed-loop crankshaft dynamics model as described in claim 1, characterized in that, S1 specifically includes: The differential equation for torsional vibration is expressed as: ； In the formula, [J] is the moment of inertia matrix, [C] is the damping matrix, and [K] is the stiffness matrix. It is a column vector of angular displacements. This is the column vector of angular velocities. Let {M} be the column vector of angular accelerations, and {M} be the column vector of excitation torques on the axis system. The torsional vibration differential equations corresponding to each inertia are established, and each torsional vibration differential equation corresponds to a flexible shaft system module. The flexible shaft system modules are coupled through the relative damping and torsional stiffness parameters of the shaft segments between adjacent inertia to form the flexible shaft system model corresponding to the entire shaft system. The torsional vibration differential equation corresponding to the nth inertia on the shaft system is expressed as: ； Among them, M n J is the excitation torque for the nth inertia. n Let C be the rotational inertia of the nth inertia. n For the absolute damping of the nth inertia, C n-1,n For the relative damping of the (n-1)th shaft segment, C n,n+1 K represents the relative damping of the nth shaft segment. n-1,n K is the torsional stiffness of the (n-1)th shaft segment. n,n+1 Let n be the torsional stiffness of the nth shaft segment. Let n be the torsional angular displacement of the nth moment of inertia. angular velocity of the nth inertia Let be the angular acceleration of the nth inertia.

3. The diesel generator set coupling matching method based on a closed-loop crankshaft dynamics model as described in claim 1, characterized in that, S2 specifically includes the following steps: S201. Based on the tangential force borne by the crank pin in the crankshaft, the expression for the gas excitation torque is derived. The expression for the gas excitation torque is then expanded using Fourier transform, and the known gas harmonic coefficients are substituted to calculate the gas excitation torque. S202, the reciprocating inertial torque generated by the reciprocating motion components in the diesel engine is calculated based on the reciprocating mass of the cylinder and the piston acceleration; S203, based on the actual crank angle displacement corresponding to each cylinder, corrects the gas excitation torque and reciprocating inertial excitation torque in real time; S204 combines the gas excitation torque and reciprocating inertial torque corresponding to each cylinder to obtain the excitation torque of each cylinder of the diesel engine. The excitation torque expressions of each cylinder are combined to form the cylinder excitation model.

4. The diesel generator set coupling matching method based on a closed-loop crankshaft dynamics model as described in claim 3, characterized in that, In S201, the tangential force p T Represented as: ； In the formula, p g The gas pressure acting on the piston is given by α, the crank angular displacement is given by β, and the connecting rod angular displacement is given by β; the tangential force p T The expression, represented using angle α, yields: ； In the formula, R is the crank radius and L is the connecting rod length; The excitation torque generated by the gas is expressed as: ； In the formula, D is the cylinder diameter; for the tangential force p T The Fourier expansion yields the following expression for the gas excitation torque: ； In the formula, v is the simple harmonic order, a v b is the cosine component of the tangential force. v C is the sinusoidal component of the tangential force. v Let ψ be the amplitude of the v-th harmonic tangential force. v Let ω be the initial phase angle of the v-th harmonic tangential force, ω be the angular frequency, and t be time; a v With b v Let a be the gas harmonic coefficient, v = 1, 2, ..., 12. Given the known gas harmonic coefficients a... v and b v Substituting this into the expansion of the gas excitation torque, we obtain the gas excitation torque.

5. The diesel generator set coupling matching method based on a closed-loop crankshaft dynamics model as described in claim 4, characterized in that, Specifically, S202 includes: the reciprocating inertial force acting on the crank pin via the connecting rod will cause the crankshaft to undergo torsional vibration, and the reciprocating inertial force is expressed as: ； In the formula, m is the reciprocating mass of the cylinder. Let be the piston acceleration; where the piston acceleration is approximately expressed as: ； The reciprocating inertial torque is expressed as: ； In the formula, λ is the ratio of crank radius to connecting rod length.

6. The diesel generator set coupling matching method based on a closed-loop crankshaft dynamics model as described in claim 5, characterized in that, S203 specifically includes: For a single flexible shaft system module, the magnitudes of the gas excitation torque and reciprocating inertial torque corresponding to the cylinder when the crank rotates through different angles are first calculated based on the expressions for gas excitation torque and reciprocating inertial torque. Then, the crank rotation angle displacement α corresponding to each flexible shaft system module is obtained in real time. Finally, the actual gas excitation torque and reciprocating inertial torque are corrected in real time based on the calculated gas excitation torque and reciprocating inertial torque.

7. The diesel generator set coupling matching method based on a closed-loop crankshaft dynamics model as described in claim 1, characterized in that, The load excitation model in S3 is expressed as follows: ； In the formula, M0 is the load excitation torque, N p n is the rated power of the generator. p n is the rated speed of the generator. e This represents the rotor speed of the generator.

8. The diesel generator set coupling matching method based on a closed-loop crankshaft dynamics model as described in claim 1, characterized in that, S5 specifically includes: The initial stiffness parameters of the flexible coupling are set, and the parameters are adjusted according to a predetermined set of proportions to obtain a set of different stiffness parameters. The different stiffness parameters of the flexible coupling are then substituted into the simulation, and the closed-loop dynamic model of the torsional vibration of the diesel generator set shaft system is simulated to obtain the instantaneous speed fluctuation and additional torque change curves of the diesel generator set shaft system under different stiffness conditions.

9. The diesel generator set coupling matching method based on a closed-loop crankshaft dynamics model as described in claim 8, characterized in that, S6 specifically includes: calculating the comprehensive evaluation value corresponding to different stiffness parameters according to preset weights, and selecting the stiffness parameter with the smallest comprehensive evaluation value as the optimal matching stiffness parameter.

10. A system for performing the diesel generator set coupling matching method based on a closed-loop crankshaft dynamics model as described in any one of claims 1-9, characterized in that, The system includes: The excitation module is used to build the cylinder excitation model and load excitation model of the diesel generator set. Flexible shaft system module, used to build a flexible shaft system model of diesel generator set; The coupling module is used to combine the models according to the input-output correspondence between the established flexible shaft system model, cylinder excitation model and load excitation model to form a closed-loop dynamic model of torsional vibration of the diesel generator set shaft system. The variable parameter analysis module is used to simulate and analyze the closed-loop dynamic model of torsional vibration using the controlled variable method, and obtain the simulation results of instantaneous speed fluctuation and additional torque of diesel generator set under different stiffness parameters. The optimization module is used to optimize the selection scheme of the stiffness of the elastic coupling based on the simulation results.

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