A design method for bench test spectrum of automotive diesel engines

Abstract

A method for designing a bench test spectrum of a vehicle diesel engine in the technical field of internal combustion engines comprises the following steps: establishing a wear analysis model for key components of a vehicle diesel engine, establishing a multivariate damage relationship model, performing damage accumulation calculation, performing damage error calculation, and performing bench test spectrum optimization. The wear analysis model for key components of a vehicle diesel engine can obtain the wear conditions of key components under different working conditions, the multivariate damage relationship model can realize the mapping of the bench working condition parameters and the wear relationship of key components, the damage accumulation calculation can obtain the accumulated wear of key components under the actual vehicle road spectrum and the bench spectrum, the damage error calculation can obtain the damage calculation error between the accumulated wear under the actual vehicle road spectrum and the accumulated wear under the bench test spectrum, and the bench test spectrum optimization model can obtain the optimal bench test spectrum with the smallest accumulated damage error under the actual vehicle road spectrum. The present invention can achieve the design of the optimal bench spectrum by optimizing the key parameters of the bench spectrum.

Description

Technical Field

[0001] The present invention relates to a test spectrum design method in the technical field of internal combustion engines, and in particular to a test spectrum design method for a vehicle diesel engine bench, which can save a lot of diesel engine test time and reduce the development cost and cycle of the diesel engine. Background Art

[0002] There is a large gap in the reliability of diesel engines at home and abroad, and the overhaul cycle is even only half of that of foreign products. Therefore, improving the reliability of diesel engines has become one of the important research contents. Conducting reliability tests on an engine to understand the damage and reliability of parts, subsystems, complete machines and vehicles often requires a lot of manpower, financial resources and time investment. If a diesel engine bench test spectrum method that accurately reflects the use of the engine can be developed, it will save a lot of iterative development time and reduce development costs and cycles.

[0003] At present, the design of bench test spectrum mainly relies on experience summary and cannot be accurately designed. This also leads to the low correlation between the test condition spectrum and the actual vehicle condition spectrum, and the inability to accurately simulate and reproduce the failure phenomenon in actual use. The test time and cost are high. Therefore, it is necessary to propose a design method for diesel engine bench test spectrum for the reasonable conduct of diesel engine system reliability test. At the same time, in order to verify the reliability of the improved design scheme of components and the whole system under the actual condition spectrum, a more reasonable bench test spectrum is needed to provide a scientific test evaluation method for the whole machine design. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention proposes a design method for a bench test spectrum for a vehicle diesel engine, which can save a lot of diesel engine test time to reduce the development cost and cycle of the diesel engine. At the same time, it can be expanded to the diesel engine development process in various fields, providing useful technical support for the development process of various diesel engines.

[0005] The present invention is achieved by the following technical solution, which comprises the following steps:

[0006] S1. Establish a wear analysis model for key components of automotive diesel engines: obtain operating parameters and corresponding wear data of key components;

[0007] S2. Establish a multivariate damage relationship model: obtain the mapping relationship between the wear and operating parameters of the main bearing, connecting rod bearing, cylinder liner, piston ring and main journal of the automotive diesel engine, and use the generalized Eyring model to characterize this mapping relationship:

[0008] w(x,y)=A+Bx+Cy+Dxy

[0009] Among them, w(x,y) is the wear amount of key components, in mm; A, B, C, D are parameters to be determined; x is the load rate, in %; y is the speed, in r / min;

[0010] S3. Calculate the cumulative damage: by inputting the bench spectrum and the actual vehicle road spectrum, and based on the cumulative damage theory, the cumulative wear of key components under the actual vehicle road spectrum and the bench spectrum is obtained;

[0011] S4. Calculate the damage error: Calculate the accumulated wear of key components under the bench spectrum and compare it with the accumulated wear of components under the actual vehicle road spectrum to obtain the wear damage error f of each component. i (x), which is used as the objective function of the bench test spectrum optimization model;

[0012] S5. Optimize the bench test spectrum: Take the damage error f i (x) is the objective function, the optimization design of the test bench spectrum is transformed into a multi-objective optimization problem, and the optimal solution is obtained through genetic algorithm; the constraints of torque, speed and time are lb i ≤x i ≤ub i (i=1,2,3),lb i andub i are the upper and lower limits of the variable, respectively, i represents the three variables of speed, load and time; by comparing the average error of the optimal solution, the solution with the smallest error among the optimal solutions is obtained;

[0013] The operating parameters in step S1 are load and rotation speed, and the key components are main bearings, connecting rod bearings, cylinder liners, piston rings, and main journals.

[0014] Furthermore, in the present invention, the establishment of the wear analysis model of key components of a diesel engine for a vehicle in step S1 comprises the following steps:

[0015] S11. Based on the volumetric method, a diesel engine working process analysis model was established to obtain the comprehensive performance parameters of the diesel engine;

[0016] S12, establish the whole machine dynamics model, and based on the cylinder pressure P g To calculate the loads of each key component;

[0017] S13. Based on Archard's wear calculation theory formula, a wear prediction model for key components is established, and the wear of key components is calculated according to the load and wear prediction model of key components, so as to realize the wear calculation of key components of automotive diesel engines.

[0018] Furthermore, in the present invention, the load of the key component in step S12 includes the connecting rod bearing load F P, Main bearing load F K , Piston ring-cylinder liner contact load F H , and its calculation formula is as follows:

[0019]

[0020]

[0021] Where, the connecting rod bearing load F P , Main bearing load F K , Piston ring-cylinder liner contact load F H The unit of F is N; ∑ It is the sum of the periodically changing gas force in the cylinder and the reciprocating inertia force generated by the total mass of the reciprocating motion along the center line of the cylinder. The unit is N; m p is the mass of the piston group, in kg; m r is the unbalanced mass of the crank, in kg; m c is the mass of the connecting rod, in kg; m cb is the mass of the connecting rod small end and the connecting rod big end, in kg; L cb is the distance from the center of mass of the connecting rod to the center of the big end of the connecting rod, in mm; L is the distance from the center of the big end of the connecting rod to the center of the small end of the connecting rod, in mm; ω is the angular velocity, in rad / s; R is the crank radius, in mm; β is the swing angle of the connecting rod, in degrees; is the crank angle, in degrees; λ is the ratio of crank radius to connecting rod length; P g is the gas pressure, in Pa; D is the piston diameter, in mm; F R is the friction force of the piston ring, in N; F e is the piston ring elastic force, unit is N; F g is the gas load on the piston ring, in N.

[0022] Furthermore, in the present invention, the Archard wear calculation theoretical formula in step S13 is:

[0023]

[0024] Where V is the wear volume in mm 3 ; F N is the load applied to the surface, F N =(F P 、F K 、F H ), unit is N; S is the sliding distance between the two surfaces, unit is mm; H is the material hardness, and K represents the wear coefficient.

[0025] Compared with the prior art, the present invention has the following beneficial effects: the present invention can save a lot of diesel engine test time by obtaining an effective bench test spectrum with a new idea, and has a good acceleration effect, thereby reducing the development cost and cycle of the diesel engine. In addition, the present invention can be applied to the bench spectrum design of various automotive diesel engines, and can be extended to the diesel engine development process in various fields, providing useful technical support for the development of various diesel engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a flow chart of the present invention;

[0027] Figure 2 The calculation flow chart of the wear analysis model of key components of a diesel engine for a vehicle of the present invention;

[0028] Figure 3 A schematic diagram of the speed of a real vehicle road spectrum in an embodiment of the present invention;

[0029] Figure 4 A load diagram of a real vehicle road spectrum in an embodiment of the present invention;

[0030] Figure 5 is a comparison diagram of the optimal solution in the embodiment of the present invention;

[0031] Figure 6 Schematic diagram of average error of optimal solution in an embodiment of the present invention;

[0032] Figure 7 Schematic diagram of cumulative wear depth comparison in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the content of the present invention easier to understand, the technical scheme of the present invention is further explained below in conjunction with specific embodiments. The examples are only used to illustrate the present invention, but the present invention is not limited to this content. The operating methods without specifying specific conditions in the following examples are usually carried out under conventional conditions or according to the product instructions.

[0034] Example

[0035] like Figure 1 As shown, the present invention is implemented by the following technical solution, and the present invention comprises the following steps:

[0036] First, a wear analysis model for key components of automotive diesel engines is established to obtain operating parameters (load and speed) and wear data of the corresponding key components (main bearing, connecting rod bearing, cylinder liner, piston ring, main journal). The overall calculation process is as follows: Figure 2As shown in the figure, it is mainly divided into three steps: (1) Based on the volumetric method, a diesel engine working process analysis model is established to obtain the comprehensive performance parameters of the diesel engine (such as cylinder pressure data). The volumetric method regards each engine component as a volume, and based on the mass conservation equation, energy conservation equation, ideal gas state equation, etc., the cylinder, exhaust pipe, intake pipe, compressor, turbine and other components of the turbocharged engine are modeled. By establishing the above model, the cylinder pressure P can be obtained. g The law of change with crankshaft angle or time; (2) Establish the whole machine dynamics model and based on the cylinder pressure P g To calculate the load data of each key component. The mass of the piston group is known to be m p (Unit: kg); The unbalanced mass of the crank is concentrated at the center of the crank pin, mainly including the crank pin and the unbalanced parts of the crank arms on both sides, with a mass of m r (unit: kg); connecting rod mass: m c (Unit: kg), according to the equivalent principle of rotational inertia, the connecting rod is converted into a two-mass replacement system, including the connecting rod small end mass and the connecting rod large end mass m cb (Unit: kg). The resultant force F acting along the center line of the cylinder ∑ (Unit: N) is the sum of the periodically changing gas force in the cylinder and the reciprocating inertia force generated by the total mass of the reciprocating motion along the center line of the cylinder, as shown below:

[0037]

[0038] Where, L cb is the distance from the center of mass of the connecting rod to the center of the big end of the connecting rod, in mm; L is the distance from the center of the big end of the connecting rod to the center of the small end of the connecting rod, in mm. ω is the angular velocity, in rad / s; R is the crank radius, in mm; β is the swing angle of the connecting rod, in degrees; is the crank angle, in degrees; λ is the ratio of crank radius to connecting rod length; P g is the gas pressure, in Pa; D is the piston diameter, in mm.

[0039] Connecting rod bearing load F P (Unit: N), main bearing load F K (Unit: N), piston ring-cylinder liner contact load F H (Unit: N) is as follows.

[0040]

[0041] In the formula, F R is the friction force of the piston ring, in N; F e is the piston ring elastic force, unit is N; F gis the gas load on the piston ring, in N.

[0042] (3) Based on Archard wear calculation theory, a wear prediction model for key components is established, and the load of key components (connecting rod bearing load F P , Main bearing load F K and piston ring-cylinder liner contact load F H ) and wear prediction model to calculate the wear of key components, so as to realize the wear calculation of key components of automotive diesel engines. Archard wear calculation theory is as follows:

[0043]

[0044] Where V is the wear volume in mm 3 ; F N is the load applied to the surface, F N =(F P 、F K 、F H ), unit is N; S is the sliding distance between the two surfaces, unit is mm; H is the material hardness, and K represents the wear coefficient.

[0045] Then, a multivariate damage relationship model was established to obtain the mapping relationship between the wear of the main bearing, connecting rod bearing, cylinder liner, piston ring and main journal of the automotive diesel engine and the operating parameters (speed and load). The generalized Eyring model was used to characterize this mapping relationship:

[0046] w(x,y)=A+Bx+Cy+Dxy

[0047] Among them, w(x,y) is the wear amount of key components, in mm; A, B, C, D are parameters to be determined, x is the load rate, in %, y is the speed, in r / min;

[0048] Then, the damage accumulation calculation is performed by combining the bench spectrum and the actual vehicle road spectrum (such as Figure 3 and Figure 4 The cumulative wear of key components under the actual vehicle road spectrum and the test bench spectrum was obtained based on the cumulative damage theory.

[0049] Then, the damage error calculation model is carried out: the accumulated wear of key components under the bench spectrum is calculated, and compared with the accumulated wear of components under the actual vehicle road spectrum to obtain the wear damage error f of each component i (x), which is used as the objective function of the bench test spectrum optimization model;

[0050] Finally, the bench test spectrum is optimized: the damage error f i(x) is the objective function, the optimization design of the test rack spectrum is transformed into a multi-objective optimization problem, and the optimal solution is obtained through the genetic algorithm, such as Figure 5 The torque, speed and time constraints are lb i ≤x i ≤ub i (i=1,2,3),lb i andub i are the upper and lower limits of the variable, respectively, i represents the three variables of speed, load and time. By comparing the average error of the optimal solution, such as Figure 6 As shown in , the solution with the smallest error in the optimal solution can be obtained. The cumulative wear amount calculated by the optimized bench spectrum is compared with the cumulative wear amount calculated by the actual vehicle road spectrum to verify the effectiveness of the method, as shown in Figure 7 And as shown in Table 1.

[0051] Table 1 Optimization effect in the embodiment of the present invention

[0052]

[0053] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for designing a bench test spectrum for a diesel engine for a vehicle, characterized in that: The following steps are involved: S1. Establish a wear analysis model for key components of automotive diesel engines: obtain operating parameters and corresponding wear data of key components; S2. Establish a multivariate damage relationship model: obtain the mapping relationship between the wear and operating parameters of the main bearing, connecting rod bearing, cylinder liner, piston ring and main journal of the automotive diesel engine, and use the generalized Eyring model to characterize this mapping relationship: w(x,y)=A+Bx+Cy+Dxy Among them, w(x,y) is the wear amount of key components, in mm; A, B, C, D are parameters to be determined; x is the load rate, in %; y is the speed, in r / min; S3. Calculate the cumulative damage: by inputting the bench spectrum and the actual vehicle road spectrum, and based on the cumulative damage theory, the cumulative wear of key components under the actual vehicle road spectrum and the bench spectrum is obtained; S4. Calculate the damage error: Calculate the accumulated wear of key components under the bench spectrum and compare it with the accumulated wear of components under the actual vehicle road spectrum to obtain the wear damage error f of each component. i (x), which is used as the objective function of the bench test spectrum optimization model; S5. Optimize the bench test spectrum: Take the damage error f i (x) is the objective function, the optimization design of the test bench spectrum is transformed into a multi-objective optimization problem, and the optimal solution is obtained through genetic algorithm; the constraints of torque, speed and time are lb i ≤x i ≤ub i (i=1,2,3),lb i andub i are the upper and lower limits of the variable, respectively, i represents the three variables of speed, load and time; by comparing the average error of the optimal solution, the solution with the smallest error among the optimal solutions is obtained; The operating parameters in step S1 are load and rotation speed, and the key components are main bearings, connecting rod bearings, cylinder liners, piston rings, and main journals.

2. The method for designing a bench test spectrum for a diesel engine for a vehicle according to claim 1, characterized in that The establishment of the wear analysis model of key components of a diesel engine for a vehicle in step S1 comprises the following steps: S11. Based on the volumetric method, a diesel engine working process analysis model was established to obtain the comprehensive performance parameters of the diesel engine; S12, establish the whole machine dynamics model, and based on the cylinder pressure P g To calculate the loads of each key component; S13. Based on Archard's wear calculation theory formula, a wear prediction model for key components is established, and the wear of key components is calculated according to the load and wear prediction model of key components, so as to realize the wear calculation of key components of automotive diesel engines.

3. The method for designing a bench test spectrum for a diesel engine for a vehicle according to claim 2, characterized in that The loads of the key components in step S12 include the connecting rod bearing load F P , Main bearing load F K , Piston ring-cylinder liner contact load F H , and its calculation formula is as follows: Where, the connecting rod bearing load F P , Main bearing load F K , Piston ring-cylinder liner contact load F H The unit of F is N; ∑ It is the sum of the periodically changing gas force in the cylinder and the reciprocating inertia force generated by the total mass of the reciprocating motion along the center line of the cylinder. The unit is N; m p is the mass of the piston group, in kg; m r is the unbalanced mass of the crank, in kg; m c is the mass of the connecting rod, in kg; m cb is the mass of the connecting rod small end and the connecting rod big end, in kg; L cb is the distance from the center of mass of the connecting rod to the center of the big end of the connecting rod, in mm; L is the distance from the center of the big end of the connecting rod to the center of the small end of the connecting rod, in mm; ω is the angular velocity, in rad / s; R is the crank radius, in mm; β is the swing angle of the connecting rod, in degrees; is the crank angle, in degrees; λ is the ratio of crank radius to connecting rod length; P g is the gas pressure, in Pa; D is the piston diameter, in mm; F R is the friction force of the piston ring, in N; F e is the piston ring elastic force, unit is N; F g is the gas load on the piston ring, in N.

4. The method for designing a bench test spectrum for a diesel engine for a vehicle according to claim 2, characterized in that The Archard wear calculation theoretical formula in step S13 is: Where V is the wear volume in mm 3 ; F N is the load applied to the surface, F N =(F P 、F K 、F H ), in N, obtained from S12; S is the sliding distance between the two surfaces, in mm; H is the material hardness, and K represents the wear coefficient.

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