Engine vibration coordination evaluation method

Abstract

This invention relates to a method for evaluating engine vibration coordination. It considers the three-dimensional vibration characteristics of the crankshaft, the vibration intensity of the engine block, and the natural frequency values ​​of each component. These three aspects are used to jointly describe and evaluate the engine's vibration coordination, resulting in a calculated vibration coordination factor. The closer this value is to 1, the better the vibration coordination; the closer it is to 0, the worse the vibration coordination. This invention considers the displacement and velocity of the crankshaft's three-dimensional vibration, the vibration velocity and acceleration intensity of the engine block, and combines these with the natural frequency values ​​of the components. Using these three aspects to jointly describe and evaluate the engine's vibration coordination can accurately reflect the overall engine vibration situation and provide direction for engine improvement design.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of engine, and particularly relates to an engine vibration coordination evaluation method, in particular to a crankshaft and engine block combined structure vibration coordination evaluation method. BACKGROUND

[0002] Continuously improving power density is an inevitable trend of military engine power development. The increase of engine power density brings three changes: the maximum combustion pressure is greatly improved, the rotating speed is greatly improved, and the supercharging pressure ratio is greatly improved, which will lead to a significant increase in the vibration level of the whole machine. The traditional vibration evaluation method cannot evaluate the vibration of the engine in multiple dimensions, cannot provide support for the vibration control improvement design of the engine, and has been difficult to meet the requirements of vibration evaluation.

[0003] The evaluation method of the traditional vibration evaluation application standard GB / T7184-2008 "Vibration Measurement and Rating of Small and Medium Power Engines" sets six vibration collection points on the engine whole machine, including four elastic supports of the engine and the front and rear ends of the V-shaped angle at the top of the cylinder block.

[0004] The vibration data of the six vibration measurement points on the whole machine vibration mathematical model are collected, and the equivalent of the comprehensive vibration intensity is used for evaluation.

[0005] The traditional vibration evaluation mainly has two defects:

[0006] 1. The position of the vibration collection point is not accurately defined, especially the two measurement points at the front and rear ends of the engine. The position deviation leads to a large vibration evaluation deviation.

[0007] 2. The vibration intensity can only reflect the comprehensive vibration of the whole machine, and cannot provide an improvement direction for the vibration control design of the engine. SUMMARY

[0008] The present application provides an engine vibration coordination evaluation method to solve the above problems.

[0009] In order to solve the above technical problems, the present application provides an engine vibration coordination evaluation method, characterized by: considering the three-dimensional vibration characteristics of the crankshaft, the vibration intensity of the engine block, and combining the natural frequency values of each component, the vibration coordination of the engine is evaluated by using the above three indicators, and the vibration coordination factor value is calculated. The closer the value is to 1, the better the vibration coordination is, and the closer the value is to 0, the worse the vibration coordination is.

[0010] Beneficial effects: The present application considers the displacement and speed of the three-dimensional vibration of the crankshaft, the vibration speed and acceleration vibration intensity of the engine block, and combines the natural frequency values of each component. The vibration coordination of the engine is evaluated by using the above three indicators, which can accurately reflect the vibration of the whole machine and provide a direction for the improvement design of the engine. Attached Figure Description

[0011] Figure 1 Schematic diagram of the principle of engine vibration coordination evaluation in this invention. Detailed Implementation

[0012] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below.

[0013] The present invention proposes an engine vibration coordination evaluation method, characterized by: considering the three-dimensional vibration characteristics of the crankshaft, the vibration intensity of the engine body, and the natural frequency values ​​of each component, using the above three aspects of indicators to describe and evaluate the vibration coordination of the engine, and calculating the vibration coordination factor value. The closer the value is to 1, the better the vibration coordination; the closer it is to 0, the worse the vibration coordination.

[0014] The three-dimensional vibration characteristics of the crankshaft include crankshaft torsional vibration angle, shaft vibration displacement and velocity, and bending vibration displacement and velocity;

[0015] The vibration intensity of an organism includes velocity vibration intensity and acceleration vibration intensity;

[0016] The evaluation criteria for engine structural vibration are as follows: the greater the difference between the natural frequency value of each component and the main harmonic frequency value of the internal combustion engine, the better. The smaller the displacement amplitude of crankshaft torsional vibration, shaft vibration, and bending vibration, and the smaller the effective value of shaft vibration and bending vibration velocity, the better; the smaller the equivalent velocity vibration intensity value and acceleration vibration intensity value of the engine body, the better.

[0017] The vibration coordination factor is defined as follows:

[0018]

[0019] Where γ6 is the vibration coordination factor, C f C c C b These are the index factors for the natural frequency component, crankshaft vibration component, and body vibration component, respectively. α, β, and γ are the corresponding weight coefficients, and the sum of the coefficients is 1. These coefficients are obtained through the entropy weight method, and the weight values ​​are shown in Table 1.

[0020] Table 1 Vibration Evaluation Weights

[0021] Natural frequency partial weight α 0.3613 Crankshaft three-dimensional vibration weight β 0.2902 Engine block vibration weight γ 0.3485

[0022]

[0023] C f Calculated by taking the logarithm of the ratio of the natural frequency of the smallest component to the primary harmonic frequency of the internal combustion engine, f1 is the first-order non-rigid frequency value of the smallest component. Typically, the crankshaft-engine block assembly structure uses the first-order crankshaft frequency value. mainis the main harmonic frequency value of the internal combustion engine, c is the resonance peak frequency shift coefficient, and c = 1.2.

[0024]

[0025] C c is the weighted calculation of the vibration evaluation index of the free end of the crankshaft, a j is each index, respectively, the torsional vibration displacement amplitude, the longitudinal vibration displacement amplitude, the longitudinal vibration velocity effective value, the bending vibration displacement amplitude, and the bending vibration velocity effective value; a j，li is the upper limit value corresponding to the above index, a j，min is the minimum value corresponding to each index, i.e., the optimal value, x j is the weight coefficient corresponding to each index, which is obtained by the entropy weight method, and the weight value is shown in Table 2.

[0026] Table 2: Crankshaft vibration evaluation weight

[0027] Crankshaft free end three-dimensional vibration index Weight x j ]]> torsional displacement weight x1 0.2028 longitudinal vibration displacement weight x2 0.1801 longitudinal vibration velocity weight x3 0.1561 bending displacement weight x4 0.2105 bending velocity weight x5 0.2505

[0028]

[0029] C b is the weighted calculation of the speed and acceleration response of the specific point of the engine block, λ v and λ a are the engine block speed and acceleration vibration intensity, y v and y a are the corresponding weight coefficients, which are obtained by the entropy weight method, and the weight value is shown in Table 3. λ v，li , λ a，li are the corresponding upper limit values, λ v，min , λ a，min are the optimal values, and λ k，li represents λ v，li and λ a，li .

[0030] Table 3: Engine block vibration evaluation weight

[0031] Engine block vibration index Index weight Peripheral point velocity degree vibration weight y v ]]> 0.5298 Weak spot acceleration vibration weight y a ]]> 0.4702

[0032] As described above, both the three-dimensional vibration of the crankshaft and the vibration of the engine block are cost-type parameters, i.e., the smaller the better, and the range transformation method is used for normalization, i.e., the upper limit and optimal value are defined, as shown in the formula.

[0033] When the first-order frequency of a component in the combined structure is lower than the product of the main harmonic frequency and the resonance peak frequency shift coefficient, or the evaluation sub-index value of the crankshaft and the engine block is greater than the upper limit value, it is considered that there is a risk of resonance or excessive vibration in one aspect, and the vibration coordination factor is 0. At the same time, the higher the lowest frequency of the component, the lower the vibration amplitude and intensity of the crankshaft and the engine block, the better the vibration response, and the closer the coordination factor to 1.

[0034] For engine vibration, some components may resonate under the action of external excitation, firstly, the component and the combination inherent frequency should be higher than the internal combustion engine working frequency and the corresponding main harmonic to prevent resonance danger, at the same time, some key components vibration is poor, which can cause a series of faults such as excessive noise, pressure shock, fatigue failure, etc., affecting the efficiency and life of the whole machine. Therefore, the vibration is evaluated from the combination modal frequency, modal shape, vibration form and vibration degree of the specific components of the combination.

[0035] The crankshaft system is the main factor causing the engine structure vibration. The unbalanced force and torque of the internal combustion engine are generated by the crankshaft movement, which causes the whole machine and its accessories to vibrate, and the poor crankshaft vibration directly affects the stable and good output of power, and affects the service life reliability, and the poor engine vibration directly leads to the poor working performance of the whole machine, and reduces the working reliability of its accessories. Therefore, the vibration performance of the main bearing structure is evaluated by the crankshaft system and the engine vibration.

[0036] The engine vibration description requires to reflect the overall vibration quality of the engine, and does not reflect the local vibration quality, the measuring point is based on the overall condition, and is selected on the structure with important significance, such as the suspension point. In addition to the overall vibration of the engine, the vibration of some key main areas is also worth attention, such as the bulkhead. Therefore, combined with the actual inherent vibration mode of the engine, the vibration of the whole machine, and the vibration of some key concerned areas, the engine vibration measuring points include the suspension point, the top surface point of the engine, the different area points of the outer side plate of the crankcase, and the points on the bearing bulkhead and bearing cover. As described above, the vibration evaluation method of the present application includes the vibration of the crankshaft and the engine, and also includes the vibration points of some key concerned areas, which can comprehensively reflect the vibration condition of the whole machine.

[0037] The above is only the preferred embodiment of the present application, it should be noted that for those skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should be considered as the protection scope of the present application.

Claims

1. An engine vibration coordination evaluation method characterized by comprising: Considering the three-dimensional vibration characteristics of the crankshaft, the vibration intensity of the engine block, and the natural frequency of each component, the vibration coordination factor is calculated by using the above three indicators to evaluate the vibration coordination of the engine. The closer the value is to 1, the better the vibration coordination is, and the closer the value is to 0, the worse the vibration coordination is. ​ Vibration coordination factor is defined as follows: wherein: respectively the natural frequency part, the crankshaft vibration part and the engine block vibration part index factor, respectively the corresponding weight coefficients, the coefficients and are 1; is the smallest component first order non-rigid frequency value, is the internal combustion engine main harmonic frequency value, is the resonance peak frequency shift coefficient; is the torsional vibration displacement amplitude, the longitudinal vibration displacement amplitude, the longitudinal vibration velocity effective value, the bending vibration displacement amplitude, and the bending vibration velocity effective value, respectively; is the upper limit value of the above index, is the minimum value of each index, i.e., the value corresponding to the optimal case, is the weight coefficient corresponding to each index; and are the body velocity and acceleration vibration intensity, respectively, and are the corresponding weight coefficients, , are the corresponding upper limit values, , are the optimal values, and represents and ; By taking the logarithm of the ratio of the minimum component natural frequency to the main order frequency of the internal combustion engine, the following is calculated: ； The crankshaft free end vibration evaluation index is weighted and calculated as follows: The body specific point velocity and acceleration response weighting is calculated as follows: 。 2. The engine vibration concordance evaluation method according to claim 1, characterized by: is 0.3613, is 0.2902, is 0.3485.

3. The engine vibration concordance evaluation method according to claim 2, characterized by: weight corresponding to the three-dimensional vibration index of the free end of the crankshaft is as follows: Torsional displacement weight : 0.2028 longitudinal vibration displacement weight : 0.1801 longitudinal vibration velocity weight : 0.1561 bending vibration displacement weight : 0.2105 bending velocity weight : 0.2505.

4. The engine vibration concordance evaluation method according to claim 2, characterized by: is 0.5298, is 0.4702.

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