CN115753122A - Engine vibration coordination evaluation method - Google Patents
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- CN115753122A CN115753122A CN202211386958.XA CN202211386958A CN115753122A CN 115753122 A CN115753122 A CN 115753122A CN 202211386958 A CN202211386958 A CN 202211386958A CN 115753122 A CN115753122 A CN 115753122A
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Abstract
The invention relates to an engine vibration coordination evaluation method, which considers the three-dimensional vibration characteristics of a crankshaft and the vibration intensity of an engine body, combines the natural frequency values of all parts, describes and evaluates the vibration coordination of the engine by using the three indexes, and calculates to obtain a vibration coordination factor value, wherein the value is closer to 1, the vibration coordination is better, the value is closer to 0, and the vibration coordination is worse. The invention considers the displacement and speed of the three-dimensional vibration of the crankshaft, the vibration speed and the acceleration vibration intensity of the engine body, simultaneously combines the inherent frequency values of the components, and uses the three indexes to describe and evaluate the vibration coordination of the engine together, thereby accurately reflecting the vibration condition of the whole engine and providing a direction for the improved design of the engine.
Description
Technical Field
The invention belongs to the technical field of engines, particularly relates to an engine vibration coordination evaluation method, and particularly relates to a crankshaft body combined structure vibration coordination evaluation method.
Background
Increasing power density is a necessary trend in the dynamic development of military engines. The increase in engine power density brings about three changes: the maximum combustion pressure is greatly increased, the rotating speed is greatly increased, the supercharging pressure ratio is greatly increased, the vibration level of the whole engine is greatly increased due to the three changes, the vibration of the engine cannot be evaluated in multiple dimensions by the traditional vibration evaluation method, support cannot be provided for the vibration control improvement design of the engine, and the requirement of the vibration evaluation of the engine cannot be met.
According to a traditional evaluation method of a vibration evaluation application standard GB/T7184-2008 'vibration measurement and rating of medium and small power engine', six vibration acquisition points are arranged on the whole engine and comprise four elastic supports of the engine and the front end and the rear end of a V-shaped clamp angle at the top of a cylinder body.
And collecting vibration data of six vibration measuring points on a complete machine vibration mathematical model, and evaluating by using the comprehensive vibration intensity equivalent.
The conventional vibration evaluation has two main defects:
1. the positions of the vibration acquisition points are not accurately defined, and especially the position deviation of two measuring points at the front end and the rear end of the engine causes large vibration estimation deviation.
2. The vibration intensity only reflects the comprehensive vibration of the whole engine and cannot provide an improvement direction for the vibration control design of the engine.
Disclosure of Invention
The invention provides an engine vibration coordination evaluation method, which solves the problems.
In order to solve the technical problems, the invention provides an engine vibration coordination evaluation method, which is characterized by comprising the following steps: considering the three-dimensional vibration characteristics of the crankshaft and the vibration intensity of the engine body, combining the inherent frequency values of all parts, describing and evaluating the vibration coordination of the engine by using the three indexes, and calculating to obtain a vibration coordination factor value, wherein the closer the value is to 1, the better the vibration coordination is, the closer to 0, the worse the vibration coordination is.
Has the beneficial effects that: the invention considers the displacement and speed of the three-dimensional vibration of the crankshaft, the vibration speed and the acceleration vibration intensity of the engine body, simultaneously combines the inherent frequency values of the components, and uses the three indexes to describe and evaluate the vibration coordination of the engine together, thereby accurately reflecting the vibration condition of the whole engine and providing a direction for the improved design of the engine.
Drawings
FIG. 1 is a schematic diagram of the evaluation of the vibration compatibility of an engine according to the present invention.
Detailed Description
In order to make the objects, contents and advantages of the present invention clearer, the following detailed description of the embodiments of the present invention is provided.
The invention provides an engine vibration coordination evaluation method, which is characterized by comprising the following steps: considering the three-dimensional vibration characteristics of the crankshaft and the vibration intensity of the engine body, combining the inherent frequency values of all parts, describing and evaluating the vibration coordination of the engine by using the three indexes, and calculating to obtain a vibration coordination factor value, wherein the closer the value is to 1, the better the vibration coordination is, the closer to 0, the worse the vibration coordination is.
The three-dimensional vibration characteristics of the crankshaft comprise a torsional vibration angle of the crankshaft, axial vibration displacement and speed, and bending vibration displacement and speed;
the vibration intensity of the machine body comprises a speed vibration intensity and an acceleration vibration intensity of the machine body;
the engine structure vibration evaluation criterion is that the difference between the inherent frequency values of all the components and the main harmonic frequency value of the internal combustion engine is larger and more optimal. The displacement amplitudes of torsional vibration, shaft vibration and bending vibration of the crankshaft are smaller and more optimal, and the effective values of the shaft vibration and the bending vibration speed are smaller; the smaller the equivalent velocity vibration intensity value and the acceleration vibration intensity value of the body are, the better the vibration intensity value is.
The vibration coordination factor is defined as follows:
wherein, γ 6 Is a vibration co-ordination factor, C f 、C c 、C b Index factors of a natural frequency part, a crankshaft vibration part and a body vibration part respectively, alpha, beta and gamma are corresponding weight coefficients, the sum of the coefficients is 1, and the systemNumbers were obtained by entropy weight method, with weight values as shown in table 1.
TABLE 1 vibration evaluation weights
| Natural frequency partial weight alpha | 0.3613 |
| Crankshaft three-dimensional vibration weight beta | 0.2902 |
| Body vibration weight gamma | 0.3485 |
C f Logarithmic calculation by the ratio of the minimum component natural frequency to the main harmonic frequency of the internal combustion engine, f 1 The first-order non-rigid frequency value of the minimum component is usually the first-order frequency value of the crankshaft in the combined structure of the crankshaft body main The value of c is 1.2, and c is the frequency shift coefficient of the resonance peak.
C c Through weighted calculation of the evaluation index of the vibration of the free end of the crankshaft, a j Respectively representing the torsional vibration displacement amplitude, the longitudinal vibration speed effective value, the bending vibration displacement amplitude and the bending vibration speed effective value as each index; a is j，li An upper limit value corresponding to the index, a j，min For the minimum, i.e. optimum, of each indexCorresponding value, x j Each index corresponds to a weight coefficient obtained by an entropy weighting method, and the weight value is shown in table 2.
TABLE 2 crankshaft vibration evaluation weights
| Three-dimensional vibration index of free end of crankshaft | Weight x j |
| Torsional vibration displacement weight x 1 | 0.2028 |
| Longitudinal vibration displacement weight x 2 | 0.1801 |
| Longitudinal vibration velocity weight x 3 | 0.1561 |
| Bending vibration displacement weight x 4 | 0.2105 |
| Bend velocity weight x 5 | 0.2505 |
C b By weighted calculation of speed and acceleration response at specific points of the body, lambda v And λ a Respectively the body speed and the acceleration vibration intensity, y v And y a To correspond toAnd the weight coefficient is obtained by an entropy weight method, and the weight value is shown in a table 3. Lambda [ alpha ] v，li 、λ a，li To correspond to the upper limit value, λ v，min 、λ a，min For optimum value, lambda in function constraint formula k，li Represents lambda v，li And λ a，li 。
TABLE 3 evaluation weight of body vibration
| Index of vibration of machine body | Index weight |
| Peripheral point velocity vibration weight y v | 0.5298 |
| Weak point acceleration vibration weight y a | 0.4702 |
In summary, the three-dimensional vibration of the crankshaft and the vibration of the engine body are cost-based parameters, i.e., the smaller the vibration is, the better the vibration is, the normalization is performed by using a range transform method, i.e., an upper limit and an optimal value are defined, as shown in the formula.
When the first-order frequency of a component in the combined structure is lower than the product of the main harmonic frequency and the frequency shift coefficient of the resonance peak, or the evaluation sub-index value of the crankshaft and the engine body is larger than the upper limit value, the component is considered to have the risk of resonance or the vibration of one aspect is too large, and the vibration coordination factor is 0. Meanwhile, the higher the lowest frequency of the component is, the lower the vibration amplitude and intensity of the crankshaft and the engine body are, the better the vibration response is, and the closer the coordination factor is to 1.
For the vibration of an engine, partial parts may resonate under the action of external excitation, the inherent frequency of the parts and the assembly is ensured to be higher than the working frequency of the internal combustion engine and the corresponding primary harmonic to prevent the resonance danger, and meanwhile, the poor vibration of some key parts can cause a series of faults such as overlarge noise, pressure oscillation, fatigue failure and the like, thereby affecting the efficiency and the service life of the whole engine. Therefore, the vibration is generally evaluated from the modal frequency, the modal shape, the vibration mode of the specific component of the assembly and the vibration degree.
The crankshaft system is the main factor that induces the vibrations of the structure of the engine block. Unbalanced force and torque of the internal combustion engine are generated by crankshaft motion, and simultaneously vibration of the whole machine and accessories of the internal combustion engine is caused, poor vibration of the crankshaft directly influences stable and good power output and life reliability of the internal combustion engine, poor vibration of the engine directly causes deterioration of working performance of the whole machine, and working reliability of the accessories of the internal combustion engine is reduced, so that vibration performance of a main bearing structure is evaluated through description of a crankshaft system and the vibration of the engine.
The machine body vibration description requires that the whole vibration quality of the machine body is reflected, the local vibration quality is not reflected, and the measuring points are selected on structures with important significance, such as suspension points and the like, based on the whole condition. Besides the whole body vibration, part of key main areas vibration is worth paying attention to, such as a middle clapboard and the like. Therefore, in combination with the actual natural vibration mode of the engine body, the vibration of the whole engine and a part of key attention areas, the vibration detection points of the engine body comprise suspension points, top surface points of the engine body, different area points of an outer side plate of a crankcase, and upper points of a partition plate and a bearing cover in the bearing. In summary, the vibration evaluation method of the invention includes the vibration conditions of the crankshaft and the engine body, and also includes vibration points of a part of key attention areas, so that the vibration conditions of the whole engine can be comprehensively reflected.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (9)
1. An engine vibration coordination evaluation method is characterized in that: considering the three-dimensional vibration characteristics of the crankshaft and the vibration intensity of the engine body, combining the inherent frequency values of all parts, describing and evaluating the vibration coordination of the engine by using the three indexes, and calculating to obtain a vibration coordination factor value, wherein the closer the value is to 1, the better the vibration coordination is, the closer to 0, the worse the vibration coordination is.
2. The engine vibration coordination evaluation method according to claim 1, characterized in that:
vibration co-ordination factor gamma 6 Is defined as follows:
wherein: c f 、C c 、C b Index factors of a natural frequency part, a crankshaft vibration part and an engine body vibration part are respectively, alpha, beta and gamma are respectively corresponding weight coefficients, and the sum of the coefficients is 1; f. of 1 Is the smallest component first order non-rigid frequency value, f main The frequency value of the main harmonic of the internal combustion engine is c, and the frequency shift coefficient of the resonance peak is c;
a j respectively representing a torsional vibration displacement amplitude, a longitudinal vibration speed effective value, a bending vibration displacement amplitude and a bending vibration speed effective value for each index; a is j，li An upper limit value, a, for the above index j，min For the minimum, i.e. optimum, value of each index, x j Corresponding weight coefficients to the indexes;
λ v and λ a Respectively the body speed and the acceleration vibration intensity, y v And y a To correspond to the weight coefficient, λ v，li 、λ a，li To correspond to the upper limit value, λ v，min 、λ a，min For optimum value, lambda in function constraint formula k，li Represents lambda v，li And λ a，li 。
3. The engine vibration coordination evaluation method according to claim 2, characterized in that: alpha is 0.3613, beta is 0.2902 and gamma is 0.3485.
4. An engine according to claim 2The method for evaluating the vibration coordination of the machine is characterized by comprising the following steps: c f The logarithm is calculated by taking the ratio of the minimum component natural frequency to the main harmonic frequency of the internal combustion engine as follows:
5. the engine vibration coordination evaluation method according to claim 2, characterized in that: c c The weighting calculation is carried out through the crankshaft free end vibration evaluation indexes as follows:
6. the engine vibration coordination evaluation method according to claim 2, characterized in that: x is a radical of a fluorine atom j The values are as follows:
。
7. The engine vibration coordination evaluation method according to claim 2, characterized in that: c b The speed and acceleration response weighting calculation through the specific points of the body is as follows:
8. the engine vibration coordination evaluation method according to claim 2, characterized in that: y is v Is 0.5298,y a Is 0.4702.
9. The engine vibration coordination evaluation method according to claim 2, characterized in that: when the first-order frequency of a component in the combined structure is lower than the product of the main harmonic frequency and the frequency shift coefficient of the resonance peak, or the evaluation sub-index value of the crankshaft and the engine body is larger than the upper limit value, the component is considered to have the risk of resonance or the vibration of one aspect is too large, and the vibration coordination factor is 0; meanwhile, the higher the lowest frequency of the component is, the lower the vibration amplitude and intensity of the crankshaft and the engine body are, the better the vibration response is, and the closer the coordination factor is to 1.
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| CN118010365A (en) * | 2024-04-08 | 2024-05-10 | 青岛汽车散热器有限公司 | Heat dissipation vibration matching detection system and method for internal combustion engine |
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| CN118010365A (en) * | 2024-04-08 | 2024-05-10 | 青岛汽车散热器有限公司 | Heat dissipation vibration matching detection system and method for internal combustion engine |
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