Method for judging combustion uniformity of cylinders of engine

Abstract

The invention relates to a method for judging combustion uniformity of each cylinder of an engine, which belongs to the technical field of engines and comprises the following steps of: acquiring near-field noise data of an air inlet side of a to-be-detected engine, acquiring 20cm near-field noise time domain data of an air inlet manifold side of an envelope surface of the engine, calculating frequency noise data of each cylinder at 100-8000Hz, and identifying and judging the uniformity of noise of each cylinder. According to the near-field noise online monitoring and recording method, engine near-field noise data under different calibration data are monitored at any time through near-field noise online monitoring and recording, an engine performance engineer is prompted to carry out calibration optimization in time, combustion of all cylinders of an engine is more uniform, and better engine sound quality is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of monitoring the combustion uniformity of each cylinder of an engine, and relates to a method for determining the combustion uniformity of each cylinder of an engine by measuring the near-field noise of the engine, and in particular to a control device module system for monitoring the near-field noise of the engine for determining the combustion uniformity of each cylinder. Background Art

[0002] Currently, the requirements for the NVH performance of engines are getting higher and higher, especially the sound quality is the key concern of the engine customer group. The engine combustion noise is the key factor affecting the engine sound quality. Uneven combustion in each cylinder will cause large vibration and noise problems. In order to improve the sound quality, the combustion uniformity of each cylinder must be monitored when optimizing the engine calibration data. Therefore, monitoring the combustion uniformity of each cylinder during the engine optimization and calibration process has become a must-test content for manufacturers when developing products.

[0003] At present, engine companies all use cylinder pressure monitoring to monitor engine uniformity. The pain point is that the cylinder pressure sensor has a high cost, is installed multiple times and is used frequently, and the sensor is easily damaged, which will greatly increase the monitoring cost, and thus the entire engine sales cost will also increase. In order to improve work efficiency and perform non-contact monitoring of the combustion uniformity of each cylinder of the engine, there is an urgent need for a set of portable mobile monitoring equipment and methods for the combustion uniformity of each cylinder. Summary of the invention

[0004] The purpose of the present invention is to provide a portable and mobile device and method for monitoring the combustion uniformity of each cylinder.

[0005] In order to achieve the above object, the technical solution of the present invention provides a method for judging the combustion uniformity of each cylinder of an engine, comprising the following steps:

[0006] Step 1, using an acoustic microphone to collect near-field noise data of the engine intake side of the engine under test under a stable speed condition;

[0007] Step 2, at a stable speed, use an acoustic microphone to collect time domain data of near-field noise at a distance of 20 cm from the intake manifold side of the envelope surface of the engine to be tested;

[0008] Step 3: The main frequency range of engine combustion noise is 100-8000 Hz. Perform continuous wavelet analysis on the time domain data according to the following continuous wavelet formula to obtain the frequency noise data of each cylinder at 100-8000 Hz:

[0009]

[0010] Among them, W f (a, b) is the wavelet signal processing formula for near-field noise time domain signal, where f(t) is the noise time domain signal, for The complex conjugate function of a is the expansion scale and b is the translation parameter. In this way, the time-frequency domain data of each cylinder noise of the engine near-field noise are obtained.

[0011] Step 4: Begin to identify and judge the uniformity of the noise of each cylinder, and calculate the ignition time of each cylinder according to the speed under stable working conditions. (Z is 1 / 2 times the number of engine cylinders, N is the engine speed under stable working conditions), according to the above calculation, determine the starting time T of one cylinder Q ;

[0012] Step 5: Calculate the frequency of the first cylinder in the range of 100 to 8000 Hz at T according to the wavelet number. Q +T 每缸 The corresponding noise in the time range is calculated by the same method for the second cylinder at T Q +2*T 每缸 The corresponding noise within the time range is calculated by analogy for the nth cylinder within the time interval T Q +n*T 每缸 Corresponding noise;

[0013] Step 6, calculating the noise difference of each cylinder according to step 5;

[0014] Step 7: If the difference in the working noise of different cylinders of the engine within the frequency range of 100 to 8000 Hz is greater than the threshold, the test instrument issues an alarm indication, and the engine needs to be calibrated and optimized for this working condition;

[0015] Step 8: If the difference in the working noise of different cylinders of the engine within the frequency range of 100 to 8000 Hz is less than the threshold, the test software issues a green light PASS indication, and the calibration data can be solidified without optimization.

[0016] Preferably, in step 1, the acquisition time is 10 s and the sampling frequency is 20000 Hz.

[0017] Preferably, in step 2, the height of the acoustic microphone is consistent with the center height of the intake manifold.

[0018] In summary, the present invention includes the following beneficial technical effects:

[0019] 1. The method of the present invention can monitor and record the near-field noise online, and constantly monitor the engine near-field noise data under different calibration data, and timely prompt the engine performance engineer to perform calibration optimization to make the combustion of each cylinder of the engine more uniform, so as to achieve better engine sound quality.

[0020] 2. The method of the present invention can realize long-term, high-frequency, and high-resolution online signal acquisition and recording, thereby improving the safety and accuracy of the acquired signals.

[0021] 3. The present invention replaces the pressure sensor to check the engine combustion uniformity, which will greatly reduce the cost of tooling and pressure sensor damage, and monitors the combustion uniformity of each cylinder of the engine in a non-contact manner. It is a very convenient portable mobile device and method for monitoring the combustion uniformity of each cylinder. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The figure is a schematic diagram of a method for judging the combustion uniformity of each cylinder of an engine according to the present invention.

[0023] Figure numerals: 1. engine to be tested; 2. acoustic microphone; 3. data acquisition and control module; 4. PC computer. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The embodiment of the present invention discloses a method for judging the combustion uniformity of each cylinder of an engine, which mainly includes a data acquisition and control module, an acoustic microphone, test software, a microphone data acquisition line, a Lan network cable and a PC computer. The acoustic microphone is connected to the data acquisition and control module, and the data acquisition and control module is connected to the PC computer.

[0026] The specific steps are as follows:

[0027] Step 1: Use a microphone to collect the near-field noise data of the engine intake side under the condition of stable speed, with a collection time of 10s and a sampling frequency of 20000Hz;

[0028] Step 2: At a stable speed, use an acoustic microphone to collect time domain data of near-field noise 20 cm from the intake manifold side of the engine envelope surface (the height of the acoustic microphone is consistent with the center height of the intake manifold).

[0029] Step 3: The main frequency range of the engine combustion noise is 100-8000 Hz. The time domain data is subjected to continuous wavelet analysis according to the following continuous wavelet formula to obtain the frequency noise data of each cylinder at 100-8000 Hz;

[0030]

[0031] W f (a, b) is the wavelet signal processing formula for near-field noise time domain signal, where f(t) is the noise time domain signal, for The complex conjugate function of a is the expansion scale and b is the translation parameter. In this way, the time-frequency domain data of each cylinder noise of the engine near-field noise are obtained.

[0032] Step 4: Begin to identify and judge the uniformity of the noise of each cylinder, and calculate the ignition time of each cylinder according to the speed under stable working conditions. (Z is 1 / 2 times the number of engine cylinders, N is the engine speed under stable working conditions), according to the above calculation, determine the starting time T of one cylinder Q .

[0033] Step 5: Calculate the frequency of the first cylinder in the range of 100 to 8000 Hz at T according to the wavelet number. Q +T 每缸 The corresponding noise in the time range is calculated by the same method for the second cylinder at T Q +2*T 每缸 The corresponding noise within the time range is calculated by analogy for the nth cylinder within the time interval T Q +n*T 每缸 Corresponding noise.

[0034] Step 6: Calculate the noise difference of each cylinder according to step 5. The ratio of this difference to the average noise value of different cylinders of all engines during the acquisition time cannot be greater than the limit threshold (unit %), otherwise it will affect the engine sound quality; this threshold must be defined in combination with subjective feelings and measured values.

[0035] Step 7: When the difference in the working noise of different cylinders of the engine within the frequency range of 100 to 8000 Hz is greater than the threshold, the test instrument issues an alarm indication and the engine needs to be calibrated and optimized for this working condition.

[0036] Step 8: If the difference in the working noise of different cylinders of the engine within the frequency range of 100 to 8000 Hz is less than the threshold, the test software issues a green light PASS indication, and the calibration data can be solidified without optimization.

[0037] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for judging the combustion uniformity of each cylinder of an engine, characterized in that: The following steps are involved: Step 1, using an acoustic microphone to collect near-field noise data of the engine intake side of the engine under test under a stable speed condition; Step 2, at a stable speed, use an acoustic microphone to collect time domain data of near-field noise at a distance of 20 cm from the intake manifold side of the envelope surface of the engine to be tested; Step 3: The main frequency range of engine combustion noise is 100-8000 Hz. Perform continuous wavelet analysis on the time domain data according to the following continuous wavelet formula to obtain the frequency noise data of each cylinder at 100-8000 Hz: Among them, W f (a, b) is the wavelet signal processing formula for the near-field noise time domain signal, f(t) is the noise time domain signal, for The complex conjugate function of a is the expansion scale and b is the translation parameter. In this way, the time-frequency domain data of each cylinder noise of the engine near-field noise are obtained. Step 4: Begin to identify and judge the uniformity of the noise of each cylinder, and calculate the ignition time of each cylinder according to the speed under stable working conditions. Where Z is 1 / 2 times the number of engine cylinders, N is the engine speed under stable working conditions, and the starting time T of one cylinder is determined according to the above calculation. Q ; Step 5: Calculate the frequency of the first cylinder in the range of 100 to 8000 Hz at T according to the wavelet number. Q +T 每缸 The corresponding noise in the time range is calculated by the same method for the second cylinder at T Q +2*T 每缸 The corresponding noise within the time range is calculated by analogy for the nth cylinder within the time interval T Q +n*T 每缸 Corresponding noise; Step 6, calculating the noise difference of each cylinder according to step 5; Step 7: If the difference in the working noise of different cylinders of the engine within the frequency range of 100 to 8000 Hz is greater than the threshold, the test instrument issues an alarm indication, and the engine needs to be calibrated and optimized for this working condition; Step 8: If the difference in the working noise of different cylinders of the engine within the frequency range of 100 to 8000 Hz is less than the threshold, the test software issues a green light PASS indication, and the calibration data can be solidified without optimization.

2. A method for judging combustion uniformity of each cylinder of an engine according to claim 1, characterized in that: In step 1, the acquisition time is 10s and the sampling frequency is 20000Hz.

3. A method for judging combustion uniformity of each cylinder of an engine according to claim 2, characterized in that: In step 2, the acoustic microphone height is consistent with the center height of the intake manifold.

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