CN111678702B - Method for obtaining overturning moment of reciprocating internal combustion engine under starting condition - Google Patents
Method for obtaining overturning moment of reciprocating internal combustion engine under starting condition Download PDFInfo
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- CN111678702B CN111678702B CN202010461142.3A CN202010461142A CN111678702B CN 111678702 B CN111678702 B CN 111678702B CN 202010461142 A CN202010461142 A CN 202010461142A CN 111678702 B CN111678702 B CN 111678702B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M15/00—Testing of engines
- G01M15/04—Testing internal-combustion engines
- G01M15/042—Testing internal-combustion engines by monitoring a single specific parameter not covered by groups G01M15/06 - G01M15/12
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- G—PHYSICS
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- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
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Abstract
The invention discloses a method for obtaining the overturning moment of a reciprocating internal combustion engine under the starting condition, which comprises the following steps: s1, determining a coupler matched with the internal combustion power assembly shaft system according to the torsional mode natural frequency of the internal combustion power assembly shaft system and the main simple harmonic excitation frequency of the internal combustion power assembly shaft system in the starting and stopping working conditions; s2, acquiring a shafting angular acceleration signal in the starting acceleration process of the internal combustion engine through a sensor; s3, calculating the shafting inertia moment according to the shafting angular acceleration and the shafting total inertia; and S4, calculating the shafting overturning moment according to the shafting inertia moment. The invention has simple process for obtaining the overturning moment, can be applied to obtaining the overturning moment under the starting working condition of the internal combustion engine, has accurate measurement result and meets the requirement of forced vibration calculation of the whole machine.
Description
Technical Field
The invention relates to the technical field of vibration control of internal combustion engines, in particular to a method for obtaining overturning moment of a reciprocating internal combustion engine under a starting condition.
Background
The vibration control of the whole internal combustion engine is a key and difficult problem in the design and application of the internal combustion engine. And determining the excitation source thereof is the basis of vibration control of the internal combustion engine. The main excitation sources of the internal combustion engine are inertia force (moment) generated by each crank link mechanism and dumping moment caused by reciprocating inertia force and gas force. The inertia force (moment) can be determined by the structural parameters and the working speed of the internal combustion engine, and the difficulty is how to accurately obtain the overturning moment caused by the gas force. The gas overturning moment is mainly obtained by two methods at present, namely, the gas overturning moment is directly or indirectly obtained by calculation based on an indicator diagram of the internal combustion engine, and the gas overturning moment is obtained by adopting an experimental method, namely, the vibration acceleration of the whole internal combustion engine is measured, and then each harmonic overturning moment is separately calculated by solving a rigid body motion equation according to a relevant dynamics principle.
The method is generally applied to the stable operation condition of the internal combustion power unit, but the two methods are not applicable to the starting time-varying process of the unit. Firstly, in the starting process of the internal combustion engine, the work of each cylinder is unstable, the work is not uniform, the indicator diagram of each cylinder of the internal combustion engine is difficult to accurately simulate, and the indicator diagram test cost for opening each cylinder of the multi-cylinder internal combustion engine is too high; secondly, the vibration measurement experimental method has considerable difficulty and error even if being used for testing the excitation force (moment) under the steady-state working condition, and is difficult to be used for testing the excitation force (moment) in the transient starting process of the internal combustion engine at present.
Disclosure of Invention
The invention aims to provide a method for obtaining the overturning moment of the starting working condition of a reciprocating internal combustion engine, and aims to solve the problems of high difficulty, high cost and low precision in the conventional method for obtaining the overturning moment of the starting working condition of the internal combustion engine.
In order to achieve the purpose, the invention provides the following technical scheme: a method of deriving a starting condition overturning moment for a reciprocating internal combustion engine, comprising the steps of:
s1, determining a coupler matched with the internal combustion power assembly shaft system according to the torsional mode natural frequency of the internal combustion power assembly shaft system and the main simple harmonic excitation frequency of the internal combustion power assembly shaft system in the starting and stopping working conditions;
s2, acquiring a shafting angular acceleration signal in the starting acceleration process of the internal combustion engine through a sensor;
s3, calculating the shafting inertia moment according to the shafting angular acceleration and the shafting total inertia;
and S4, calculating the shafting overturning moment according to the shafting inertia moment.
Further, in the step S1: the natural frequency of the torsional vibration mode of the shafting of the internal combustion power assembly is more than 4.0 times greater than the first-order primary and secondary harmonic excitation frequency of the start-stop working condition.
Further, in the step S2: the sensor is a magnetoelectric sensor.
Further, the step S2 includes:
s21, acquiring a voltage pulse signal of the shaft system through a measuring fluted disc and a magnetoelectric sensor which are arranged on the shaft system;
s22, calculating the time corresponding to each pulse in the voltage pulse signals of the shafting, and calculating to obtain an angular velocity signal;
and S23, preprocessing the angular velocity signal, and then obtaining an angular acceleration signal of the shafting through differentiation.
Further, the preprocessing process comprises distortion point filtering, abnormal data elimination and low-pass filtering.
Further, in step S3, the expression for calculating the shafting inertia moment is:
T＝I·a (1)
wherein T represents shafting inertia moment, I represents shafting total inertia, and a represents shafting acceleration.
Further, in step S4, the expression for calculating the shafting overturning moment is:
M＝T (2)
wherein M represents shafting overturning moment, and T represents shafting inertia moment.
By adopting the technical scheme, the invention has the following beneficial effects:
the invention provides a method for obtaining the overturning moment of the starting condition of a reciprocating internal combustion engine, which obtains the angular velocity signal of a shaft system through a magnetoelectric sensor, obtains the angular acceleration signal of the shaft system through pretreatment and differentiation, and ensures that the inherent frequency of the torsional vibration mode of an internal combustion power shaft system is far higher than the main simple harmonic excitation frequency of the starting and stopping condition, so that the shaft system approximately moves in a rolling vibration mode under the starting and stopping condition, the total tangential moment of a crankshaft can be obtained by the angular acceleration of the shaft system and the total inertia of the shaft system, and the overturning moment and the total tangential moment of the crankshaft are the relation of acting force and reacting force, so the overturning moment is equal to the total tangential moment of the crankshaft, namely the overturning moment. The method for obtaining the overturning moment under the starting condition of the reciprocating internal combustion engine, which is provided by the invention, has the advantages of simplicity, convenience, accuracy and no damage to the internal combustion engine: the flywheel fluted disc of the internal combustion engine can be utilized, and the sensor is arranged near the fluted disc to carry out measurement, so that the measurement is simple and convenient; the measurement principle is clear, the calculation process is precise, and the accuracy of the measurement result can be ensured; the measuring mode does not need to perform destructive modification on the internal combustion engine, nondestructive testing is realized, and the cost is low.
Drawings
FIG. 1 is a flow chart of a method for obtaining an overturning moment under a starting condition of a reciprocating internal combustion engine according to the present invention;
FIG. 2 is a graph showing the variation of the natural frequency of the front 3 th order torsional mode of the shafting of the 6159Z diesel engine with the rigidity of the coupling;
FIG. 3 is a diagram of the resonance speed of a 6159Z diesel engine during starting;
FIG. 4 is a schematic diagram of a voltage pulse signal;
FIG. 5 is a schematic diagram of an original voltage pulse signal at a flywheel end of a crankshaft in a start-steady-stop process of a shafting of a 6159Z diesel engine;
FIG. 6 is a schematic diagram of signals of angular velocity at a flywheel end of a crankshaft during start-up acceleration to a steady state of a 6159Z diesel engine;
FIG. 7 is an enlarged partial view of the startup acceleration phase of FIG. 6;
FIG. 8 is a schematic diagram of an angular acceleration signal at a flywheel end of a crankshaft in a starting acceleration process of a 6159Z diesel engine;
FIG. 9 is a diagram of an n-mass shafting equivalent system;
FIG. 10 is a schematic diagram of total tangential torque of a crankshaft during starting acceleration of a 6159Z diesel engine.
Detailed Description
The invention is described in further detail below with reference to the following figures and embodiments:
referring to fig. 1, a method of obtaining a starting condition overturning moment of a reciprocating internal combustion engine, comprising the steps of:
and S1, determining a coupler matched with the internal combustion power assembly shaft system according to the torsional mode natural frequency of the internal combustion power assembly shaft system and the main simple harmonic excitation frequency of the internal combustion power assembly shaft system in the starting and stopping working conditions.
Further, in the step S1: the natural frequency of the torsional vibration mode of the shafting of the internal combustion power assembly is more than 4.0 times greater than the first-order primary and secondary harmonic excitation frequency of the start-stop working condition.
Specifically, the 6159Z diesel engine is used as a test object, an internal combustion power assembly shafting comprises an internal combustion engine crankshaft, a coupler and a driven shafting, wherein the rigidity of the coupler plays a decisive role in the natural frequency of a shafting torsional vibration low-order mode, the coupler with different rigidities can be matched with the shafting for calculation, the change rule of the shafting torsional vibration mode natural frequency along with the rigidity of the coupler is analyzed, as shown in fig. 2, until the natural frequency of the internal combustion power shafting torsional vibration mode is far higher than the main simple harmonic excitation frequency of the start-stop working condition, as shown in fig. 3. Or a rigid coupling is directly adopted, and then the inherent frequency of the torsional vibration mode of the internal combustion power shaft system is verified to be far higher than the main simple harmonic excitation frequency of the start-stop working condition. The method can be obtained that when the natural frequency of the torsional vibration mode of the internal combustion power assembly shafting is far higher than the main simple harmonic excitation frequency under the start-stop working condition, the shafting can move approximately in a rolling vibration mode under the start-stop working condition. When the shafting is approximate to a rigid body and moves in a rolling vibration mode, the total tangential moment of the crankshaft can be obtained by the angular acceleration of the shafting and the total inertia of the shafting, and the overturning moment and the total tangential moment of the crankshaft are in the relation of acting force and reacting force, so that the overturning moment is equal to the total tangential moment of the crankshaft.
And S2, acquiring a shafting angular acceleration signal in the starting acceleration process of the internal combustion engine through a sensor.
Further, in the step S2: the sensor is a magnetoelectric sensor.
Further, the step S2 includes:
s21, acquiring a voltage pulse signal of the shaft system through a measuring fluted disc and a magnetoelectric sensor which are arranged on the shaft system;
s22, calculating the time corresponding to each pulse in the voltage pulse signals of the shafting, and calculating to obtain an angular velocity signal;
and S23, preprocessing the angular velocity signal, and then obtaining an angular acceleration signal of the shafting through differentiation.
Further, the preprocessing process comprises distortion point filtering, abnormal data elimination and low-pass filtering.
Specifically, a sensor is installed on a shafting, and shafting angular vibration in the starting process of a unit is tested, and original voltage pulse signals with uniform angular intervals are generally measured through a magnetoelectric sensor and the like. The sensors for current angular vibration measurement generally employ non-contact sensors, most commonly magnetoelectric sensors. The sensor is arranged beside a measuring fluted disc on a shaft system and has the function of converting the rotation speed change of the shaft system into the periodic change of an electric signal, and each time the sensor rotates by one tooth (the angle theta)0) The voltage signal output by the sensor changes to output one voltage pulse signal at a time, as shown in fig. 4.
Determining the corresponding time delta t of each pulse in the voltage pulse signaliThen, the curve of the angular velocity with time can be calculated, and the expression is as follows:
fig. 5 shows an original voltage pulse signal at a flywheel end of a crankshaft of an internal combustion powertrain shafting adopting a high-rigidity coupling, and it can be seen that the original voltage pulse signal does not generate obvious voltage fluctuation. The angular velocity curves of the crankshaft flywheel end in the starting process of the shafting are shown in fig. 6 and 7, and it can be seen that the angular velocity signals do not generate obvious fluctuation in the process, which indicates that the shafting does not generate torsional vibration resonance in the starting process. In the low-speed section of the starting process, regular speed fluctuation generated by the shafting is generated by a rolling vibration mode (rigid body mode) of a 3.0 main simple harmonic equal-torque excitation shafting of the 6-cylinder internal combustion engine.
After obtaining the crankshaft angular velocity signal in the acceleration starting process, preprocessing the signal, including distortion point filtering, abnormal data elimination and low-pass filtering, and then obtaining the shafting acceleration signal through differentiation, as shown in fig. 8.
And S3, calculating the inertia moment of the shafting according to the angular acceleration of the shafting and the total inertia of the shafting.
Further, in step S3, the expression for calculating the shafting inertia moment is:
T＝I·a (1)
wherein T represents shafting inertia moment, I represents shafting total inertia, and a represents shafting acceleration.
Specifically, through the analysis, in the starting process of the unit, the relative displacement between each component of the shafting is small and can be ignored, and the whole power shafting can be regarded as a rigid body and moves according to the Newton's second theorem. The calculation method of the total inertia I of the shafting is to add inertia algebras of all parts of the shafting as shown in FIG. 9, namely
And calculating the shafting inertia moment T according to the angular acceleration a of the shafting and the total inertia I of the shafting.
In the starting process, the driven machine does not work normally, so that the total tangential moment output by the shafting of the internal combustion engine is equal to the inertia moment of the shafting, and the total tangential moment of the crankshaft in the starting process of the unit is obtained, as shown in fig. 10.
And S4, calculating the shafting overturning moment according to the shafting inertia moment.
Further, in step S4, the expression for calculating the shafting overturning moment is:
M＝T (3)
wherein M represents shafting overturning moment, and T represents shafting inertia moment.
Specifically, the overturning moment M can be obtained from the relation between the acting force and the reaction force between the overturning moment and the total tangential moment of the crankshaft.
The foregoing is merely an example of the present invention and common general knowledge in the art of designing and/or characterizing particular aspects and/or features is not described in any greater detail herein. It should be noted that, for those skilled in the art, without departing from the technical solution of the present invention, several variations and modifications can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicability of the patent. The scope of the claims of the present application shall be determined by the contents of the claims, and the description of the embodiments and the like in the specification shall be used to explain the contents of the claims.
Claims (5)
1. A method of deriving a starting condition overturning moment for a reciprocating internal combustion engine, comprising the steps of:
s1, determining a coupler matched with the internal combustion power assembly shaft system, wherein the coupler can enable the torsional vibration mode natural frequency of the internal combustion power assembly shaft system to be more than 4.0 times larger than the primary simple harmonic excitation frequency of the first-order primary simple harmonic excitation frequency of the internal combustion power assembly shaft system in the start-stop working condition;
s2, acquiring a shafting angular acceleration signal in the starting acceleration process of the internal combustion engine through a sensor;
s3, calculating the shafting inertia moment according to the shafting angular acceleration and the shafting total inertia;
s4, calculating the shafting overturning moment according to the shafting inertia moment, wherein the calculation expression of the shafting overturning moment is as follows:
M＝T (3)
wherein M represents shafting overturning moment, and T represents shafting inertia moment.
2. The method for obtaining the overturning moment of the starting condition of the reciprocating internal combustion engine as claimed in claim 1, wherein in the step S2: the sensor is a magnetoelectric sensor.
3. The method for obtaining the overturning moment under the starting condition of the reciprocating internal combustion engine as claimed in claim 2, wherein the step S2 comprises:
s21, acquiring a voltage pulse signal of the shaft system through a measuring fluted disc and a magnetoelectric sensor which are arranged on the shaft system;
s22, calculating the time corresponding to each pulse in the voltage pulse signals of the shafting, and calculating to obtain an angular velocity signal;
and S23, preprocessing the angular velocity signal, and then obtaining an angular acceleration signal of the shafting through differentiation.
4. The method for obtaining the overturning moment under the starting condition of the reciprocating internal combustion engine as claimed in claim 3, wherein in the step S23: the preprocessing process comprises distortion point filtering, abnormal data elimination and low-pass filtering.
5. The method for obtaining the overturning moment of the starting condition of the reciprocating internal combustion engine as claimed in claim 1, wherein in the step S3, the expression of the shafting inertia moment is calculated as follows:
T＝I·a (1)
wherein T represents shafting inertia moment, I represents shafting total inertia, and a represents shafting acceleration.
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