CN111780866A - Method and device for testing natural frequency of diesel engine test base in installed state - Google Patents

Abstract

In order to solve the problem of inaccurate test result of the natural frequency of the diesel engine test base in the prior art, the invention provides a method and a device for testing the natural frequency of the installation state of the diesel engine test base, which are characterized in that: the method comprises the following steps: s1, collecting a vibration time domain signal of a test base and the rotating speed of a diesel engine; s2, carrying out Fourier transform on the vibration time domain signal in the step S1, and converting the vibration time domain signal into a vibration frequency domain signal; s3, obtaining a frequency spectrum curve with the abscissa as frequency and the ordinate as vibration amplitude; and S4, sequentially analyzing the frequency spectrum curves obtained in the step S3 according to a spectrogram analysis method and an order slice image analysis method to obtain a certain order natural frequency of the test base. The natural frequency of the test base is measured in the installation state, the natural frequency of the diesel engine base is collected and analyzed through excitation generated by the diesel engine, and a certain order of natural frequency of the test base can be quickly and accurately obtained.

Description

Method and device for testing natural frequency of diesel engine test base in installed state

technical field

The invention relates to the field of high-speed diesel engine testing, in particular to a method and device for testing the natural frequency of a diesel engine test base in an installed state.

Background technique

The traditional method of testing the natural frequency of the oil engine test base in the installed state, such as the hammer method, is almost difficult to arouse an effective frequency response curve because the base is too solid in the installed state, and the natural frequency is difficult to separate and capture.

The conventional process for the natural frequency test of the existing diesel engine test base is as follows: first, the free state modal test is carried out, and the natural frequency and mode shape of the base are obtained through the test method; then the test results are compared with the simulation calculation results, and the model is adjusted to make the The model state is close to the measured state; finally, the boundary constraint state is established in the simulation software, the test installation state is simulated, and the simulation calculation in the installation state is carried out. However, the simulation model often cannot achieve the same boundary state as the actual installation, and the accuracy of the simulation results is not high.

SUMMARY OF THE INVENTION

In order to solve the problem of inaccurate test results of the natural frequency of the diesel engine test base in the prior art, the present invention provides a natural frequency test method and device for the installation state of the diesel engine test base, which utilizes the excitation generated by the operation of the diesel engine to collect and analyze the natural frequency of the base , which can effectively solve the above technical problems.

The method for testing the natural frequency of a diesel engine test base in an installed state is characterized in that it comprises the following steps:

S1. Install the diesel engine on the test base, and collect the vibration time domain signal of the test base and the rotational speed of the diesel engine;

S2. Set different rotational speed gradings according to the rotational speed of the diesel engine, and take the rotational speed grading as the calculation period, perform Fourier transform on the vibration time domain signal described in step S1, and convert it into a vibration frequency domain signal;

S3. Put the vibration frequency domain signal corresponding to each rotational speed gear in step S2 into a coordinate system, and obtain the frequency spectrum curve with the abscissa as the frequency and the ordinate as the vibration amplitude;

S4. Analyze the spectrum curves described in step S3 sequentially according to the spectrogram analysis method and the order slice diagram analysis method, and average the results obtained by the above two to obtain a certain order natural frequency of the test base.

A device for testing the natural frequency of a diesel engine test base installed state, characterized in that it includes a PC terminal, a signal collector, a vibration acceleration sensor arranged on the diesel engine test base, and a rotational speed sensor for detecting the rotational speed of the diesel engine; wherein, the PC terminal It is electrically connected with the signal acquisition instrument for collecting the data of the signal acquisition instrument; the signal acquisition instrument is electrically connected with the vibration acceleration sensor and the rotational speed sensor respectively, and is used for acquiring the vibration of the diesel engine test base Acceleration and RPM of the diesel engine.

Beneficial effects: The present invention excites the test base by using the excitation force of the diesel engine itself in a wide frequency range. When the excitation force frequency is close to the natural frequency of a certain order in the installation state of the base, the base There will be a large vibration on the vibration signal, and a large amplitude will appear somewhere in the vibration signal, so as to obtain a certain order natural frequency of the test base.

The invention measures the natural frequency of the test base in the installed state, collects and analyzes the natural frequency of the diesel engine base through the excitation generated by the operation of the diesel engine, and can quickly and accurately obtain the natural frequency of a certain order of the test base.

Description of drawings

Figure 1 is a flow chart of the method of the present invention.

Fig. 2 is a test system diagram of the present invention.

Figure 3 is a spectrum diagram of the natural frequency test.

Figure 4 is a slice diagram of order 1.5.

Figure 5 is a slice diagram of order 2.0.

Figure 6 is a slice diagram of order 2.5.

Figure 7 is a slice diagram of order 3.5.

Among them, 1 is the PC terminal, 2 is the communication network cable, 3 is the signal acquisition instrument, 4 is a set of vibration acceleration sensor, 5 is the test base, 6 is the rotational speed sensor, and 7 is the signal line.

Detailed ways

The present invention will be described in further detail below with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are intended to illustrate the invention, but not to limit the scope of the invention.

Specific embodiment I: The PC terminal 1 may be a notebook computer.

As shown in Figure 2, a natural frequency test device for diesel engine test base installation state, including a notebook computer, communicates with a signal acquisition instrument 3 through a communication network cable 2, and the signal acquisition instrument 3 is connected to a rotational speed sensor 6 through a signal cable 7. And a set of vibration acceleration sensor 4, the rotational speed sensor 6 is installed near the gear plate for measuring the rotational speed of the diesel engine, the vibration acceleration sensor 4 is arranged on the diesel engine test base 5, and the rotational speed and vibration signals are displayed on the notebook computer 1 in real time.

As shown in Figure 1, the method for testing the natural frequency of a diesel engine test base in an installed state is characterized in that it comprises the following steps:

S1. Under the no-load state of the diesel engine, within the working speed range, such as the speed range from the idle speed to the maximum speed, through the continuous up/down speed, the vibration acceleration sensor 4 installed on the test base 5 will pass the vibration state of the test base 5 in real time. Signal acquisition instrument 3, record to the notebook computer.

S2. Use the rotational speed measured by the rotational speed sensor 6 as the trigger signal, set the rotational speed bins, and use the specific rotational speed bins as the calculation period, perform Fourier transform on the vibration time domain signal collected by the vibration acceleration sensor 4, and convert it into The vibration signal in the frequency domain, the time domain signal.

S3. In step S2, within the working speed range, place the vibration frequency domain signals collected by each speed stage and obtained by Fourier transformation into a coordinate system, and display them uniformly. In the spectrum curve, the abscissa is the frequency, the ordinate is the vibration amplitude, the amplitude of the curve represents the magnitude of the vibration speed, the greater the vibration speed, the higher the amplitude.

S4. According to the spectrogram analysis method and the order slice diagram analysis method, analyze the spectrum curves described in step S3 in turn: wherein, there are two methods for analyzing the test data:

The first is the spectrogram analysis method, as shown in Figure 3, when there is a clearly concentrated peak near a certain frequency in the spectrogram, it is considered that a certain order natural frequency of the test base 5 exists here;

The second is the analysis method of order slice graph, as shown in Fig. 4 to Fig. 7, taking multiple order slice graphs, summarizing the peaks, and when the corresponding frequency of the peak is concentrated near a certain frequency, the frequency is considered to be the frequency of the test base 5. A certain order natural frequency, as shown in Table I. By comparing the natural frequencies obtained by the two methods, the natural frequencies of the test base can be obtained more accurately, as shown in Table II. Preferably, a certain order natural frequency of the final test base 5 can be obtained by using an average value algorithm.

Table I: The result table of natural frequency analysis of order slice diagram.

Table II: Comparison table of natural frequencies obtained by spectrogram analysis method and order slice diagram analysis method

Analytical method 1st order natural frequency (Hz) 2nd order natural frequency (Hz) Spectrogram 30 54 order slice 31.5 54

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical scope disclosed by the present invention can easily change or replace them, all belonging to the scope of the present invention. within the protection scope of the present invention. Therefore, the protection scope of the present invention is described in accordance with the protection scope of the claims.

Claims (6)

1. a natural frequency test method for diesel engine test base installation state, is characterized in that: may further comprise the steps: S1. Install the diesel engine on the test base, and collect the vibration time domain signal of the test base and the rotational speed of the diesel engine; S2. Set different rotational speed gradings according to the rotational speed of the diesel engine, and take the rotational speed grading as the calculation period, perform Fourier transform on the vibration time domain signal described in step S1, and convert it into a vibration frequency domain signal; S3. Put the vibration frequency domain signal corresponding to each rotational speed gear in step S2 into a coordinate system, and obtain the frequency spectrum curve with the abscissa as the frequency and the ordinate as the vibration amplitude; S4. Analyze the spectrum curves described in step S3 sequentially according to the spectrogram analysis method and the order slice diagram analysis method, and average the results obtained by the above two to obtain a certain order natural frequency of the test base. 2. a kind of diesel engine test base installation state natural frequency testing method according to claim 1, is characterized in that: described diesel engine in described S1 step is in no-load state, in the working speed range, carries out continuous rising/falling Rotating speed. 3. a kind of diesel engine test base installation state natural frequency testing method according to claim 1, is characterized in that: the frequency spectrum analysis method described in the described S4 step refers to: in the frequency spectrum curve described in the S3 step, a certain frequency When a concentrated peak appears nearby, it is considered that a certain order natural frequency of the test base exists there. 4. a kind of diesel engine test base installation state natural frequency testing method according to claim 1, is characterized in that: the order slice diagram analysis method in described S4 step refers to: in the frequency spectrum curve described in S3 step, take In the multi-order slice graph, the peaks are summarized, and when the corresponding frequency of the peak is concentrated at a certain frequency, the frequency is considered to be a certain order natural frequency of the test base. 5. A natural frequency test device for diesel engine test base installation state, characterized in that: it comprises a PC end, a signal acquisition instrument, a vibration acceleration sensor arranged on the diesel engine test base and a rotational speed sensor for detecting the rotational speed of the diesel engine; Wherein, the PC terminal is electrically connected with the signal acquisition instrument for collecting data of the signal acquisition instrument; the signal acquisition instrument is electrically connected with the vibration acceleration sensor and the rotational speed sensor, respectively, for use in collecting data from the signal acquisition instrument. The vibration acceleration of the diesel engine test bed and the rotational speed of the diesel engine are collected. 6 . The device for testing the natural frequency of a diesel engine test base in an installed state according to claim 5 , wherein the rotational speed sensor is arranged on a toothed plate for measuring rotational speed on the diesel engine. 7 .

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