CN112465744A

CN112465744A - Digital image measuring method based on local air-fuel ratio of flame in engine cylinder

Info

Publication number: CN112465744A
Application number: CN202011145994.8A
Authority: CN
Inventors: 许敏; 孙哲; 马臻
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2020-10-23
Filing date: 2020-10-23
Publication date: 2021-03-09
Anticipated expiration: 2040-10-23
Also published as: CN112465744B

Abstract

The invention discloses a digital image measuring method based on local air-fuel ratio of flame in an engine cylinder, which relates to the technical field of combustion diagnosis in engine cylinders of automobiles and the like, and aims at calibrating CH, CH2 self-luminescence in flame by a color camera sensor to obtain corresponding signal intensity, and combines RGB channel response values of the color camera, and calibrating by using premixed standard flames with different air-fuel ratios, so that the color camera is transformed into equipment capable of measuring the CH self-luminescence flame area, C2 self-luminescence flame area and different air-fuel ratios of particle generating areas of each pixel aiming at the whole image. By implementing the method, the overall flame air-fuel ratio can be obtained on the premise of not losing the original color image, the cost is greatly reduced compared with other measuring methods, and the method can be widely applied to various flame testing occasions.

Description

Digital image measuring method based on local air-fuel ratio of flame in engine cylinder

Technical Field

The invention relates to the technical field of combustion diagnosis in an aircraft engine cylinder, in particular to a digital image measuring method based on local air-fuel ratio of flame in the engine cylinder.

Background

In the design process of core combustion systems of engines such as automobiles and the like, the in-cylinder flame images are captured and analyzed by using an advanced image processing method, so that the design and development speed can be effectively increased, and the design of the combustion system is optimized, thereby developing the engines with energy conservation and emission reduction. In the technical field of in-cylinder flame diagnosis systems, in the prior art, optical measures are generally combined with a high-speed camera to capture and extract in-cylinder flames. The internationally leading practice is to perform statistical qualitative analysis of the shape, boundary, and intensity of an image, and to perform qualitative analysis of, for example, yellow and blue flames with a color camera. In addition, the components of the intermediate products in the combustion process can be analyzed by capturing and recording specific flame products by using different filters and a high-speed camera for in-cylinder images or performing spectral analysis on in-cylinder substances by using a spectrometer. The measurement of the flame air-fuel ratio usually needs to be calibrated by the fluorescence of a specific tracer substance in a cylinder, and the laser-induced fluorescence test is carried out on the local part in the cylinder, so as to obtain the accurate local air-fuel ratio.

However, flame analysis using high-speed color cameras currently mainly involves qualitative analysis, and cannot perform quantitative measurement for each pixel (local) air-fuel ratio, losing a large amount of information. Although accurate air-fuel ratio measurement can be performed by using test methods such as a laser diagnosis system and a spectrometer, an image intensifier and high-low-speed and high-energy laser are required to be matched for receiving the signal, so that the speed of the obtained image data is low, and the flame development process in an engine cylinder cannot be analyzed with the precision of the crank angle. In addition, due to the restriction of a complex system, experiment precision, fuel and other factors, the rapid and efficient industrial application is difficult.

Therefore, those skilled in the art have made an effort to develop a digital image measuring method based on the local air-fuel ratio of flame in an engine cylinder, which can calculate CH self-luminous flame region, C2 self-luminous flame region, particulate matter soot generation region, and in-cylinder flame air-fuel ratio distribution region while obtaining a picture of color flame in the cylinder.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, the technical problems to be solved by the present invention are: how to obtain the global flame air-fuel ratio without losing the original color image.

In order to achieve the aim, the invention provides a digital image measuring method based on the local air-fuel ratio of flame in an engine cylinder, which comprises the following steps:

(1) building a test system, wherein the test system is formed by assembling an image multiplier and a high-speed color camera;

(2) building a standard flame light source, generating fuel flames to be tested with different air-fuel ratios by using a premix burner, recording and shooting by using the test system, and calibrating the flames to be standard premix flames of the fuel to be tested under different air-fuel ratio states;

(3) calculating the intensity in the channel;

(4) establishing a single functional relationship between CH/C2 and air-fuel ratio;

(5) and completing the calibration process of the air-fuel ratio prediction calculation.

Further, the high-speed color camera has a red (R) channel, a green (G) channel, and a blue (B) channel.

Further, the image multiplier has CH channels and original channels.

Further, the channels with the CH are matched with and provided with 430nm band-pass filters, and no filter is added to the original channels.

Further, the image multiplier has CH channels, C2 channels, and original channels.

Further, 430nm band-pass filters are installed in the CH channels in a matching mode, 516nm band-pass filters are installed in the C2 channels in a matching mode, and no filter is added to the original channels.

Further, in the step (3), the CH channel directly extracts the flame CH intensity distribution, the intensity in the blue (B) channel is calculated by using an image processing process, the intensity in the blue (B) channel is calculated by C2, and the flame C2 intensity distribution is extracted.

Further, in the step (3), the CH channel directly extracts the intensity distribution of the flame CH, and the C2 channel extracts the intensity distribution of the flame C2.

Further, in the step (3), the intensity distribution of the particulate matter root is calculated using the red (R) channel.

Further, the step (4) is characterized in that the single functional relation between CH/C2 and the air-fuel ratio is established by using the strength distribution ratio of CH and C2 and combining the air-fuel ratio of the standard flame

Compared with the prior art, the invention at least has the following beneficial technical effects:

the digital image measuring method based on the local air-fuel ratio of the flame in the engine cylinder, provided by the invention, can be used for calculating a CH self-luminous flame region, a C2 self-luminous flame region, a particulate matter root generation region and an in-cylinder flame air-fuel ratio distribution region while obtaining an in-cylinder color flame picture, and is quick and efficient; the method obtains the global flame air-fuel ratio on the premise of not losing the original color image, greatly reduces the cost compared with other measuring methods, has wide test targets, and can carry various test objects such as optical engines, endoscope real engines and other heat engines, even other types of flames for measurement.

The conception, the specific structure and the technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, the features and the effects of the present invention.

Drawings

FIG. 1 is a schematic illustration of the calibration process of the present invention;

fig. 2 is a graph of the response of the camera of the present invention at different wavelengths.

Detailed Description

The technical contents of the preferred embodiments of the present invention will be more clearly and easily understood by referring to the drawings attached to the specification. The present invention may be embodied in many different forms of embodiments and the scope of the invention is not limited to the embodiments set forth herein.

In the drawings, structurally identical elements are represented by like reference numerals, and structurally or functionally similar elements are represented by like reference numerals throughout the several views. The size and thickness of each component shown in the drawings are arbitrarily illustrated, and the present invention is not limited to the size and thickness of each component. The thickness of the components may be exaggerated where appropriate in the figures to improve clarity.

Example 1

As shown in fig. 2, the response of the camera at different wavelengths is different for different cameras with different sensor filter responses. The visible and self-luminous main sources of the premixed hydrocarbon fuel flame are C2 and CH, the RGB (red, green and blue) filter of the color camera receives corresponding efficiency, and the response value alpha and the intensity I of each channel of RGB are in relation to the light with specific wavelength:

the intensity values entering each channel are:

for premixed flames, the assumption is made that the light intensities of only 430nm and 516nm make up, and the intensities of the three channels are:

as shown in fig. 1, the test system constructed in this embodiment is assembled by a high-speed color camera and a 2-fold image multiplier (Doubler), the camera image copies the same image for about 2 times, i.e., the images of the object to be tested in two channels of the multiplier are recorded at one time, one of the channels is provided with a 430nm band-pass filter in a matching manner, the 430nm band-pass filter only allows light of 430nm (i.e., CH × wavelength) and its nearby spectrum to pass through, and the other channel is not added with any filter to record the original flame color image.

And (3) building a standard flame light source, generating flames of the fuel to be tested with different air-fuel ratios by using the premix burner, recording and shooting by using a test system, and calibrating the flames into standard premix flames of the fuel to be tested under different air-fuel ratio states.

The multiplier is carried by the high-speed camera, and the distribution, the intensity and the original flame color image of the object CH to be measured can be obtained simultaneously. C2 and CH are recorded simultaneously in the B channel and combined into B channel intensity values. The CH channel may directly extract the flame CH intensity distribution, and the intensity in the blue (B) channel is calculated using an image processing process, thereby calculating the intensity of C2 in the blue (B) channel to extract the intensity distribution of C2.

Similarly, in the G channel, the light emitting area and the intensity value of the particulate matter root can be calculated by subtracting C2 light from the light emitting value of the particulate matter above 550nm and the self-luminous intensity value of C2.

And establishing a single functional relation between CH/C2 and the air-fuel ratio by using the intensity distribution ratios of CH and C2 and standard premixed flames of the fuel to be measured under different air-fuel ratios, wherein the functional relation is a core calculation formula for air-fuel ratio calculation.

And completing the calibration process of the air-fuel ratio prediction calculation. The imaging system can directly perform optical test diagnosis on the optical engine, particularly in the high-speed flame recording process, simultaneously calculate a CH self-luminous flame region, a C2 self-luminous flame region, a particulate matter root generation region and an in-cylinder flame air-fuel ratio distribution region by using an image processing calculation method, and can realize quantitative prediction on a local air-fuel ratio by accurately extracting the intensity.

Example 2

Example 2 differs from the apparatus of example 1 only in that this example uses a 3-pass image multiplier, i.e. a 516nm (C2 × wavelength) band filter and a 430nm (CH × wavelength) band filter are installed simultaneously, and the other channel continues to retain the original image without installation, and can directly capture the intensity distribution of C2 and CH × and perform calibration and calculation of the air-fuel ratio by CH × C2.

Example 3

In this embodiment, the R channel is used for performing the auxiliary calculation, the C2 strength and the area in the G channel of the particulate matter are calculated first, and then the CH strength and the area are calculated, so as to obtain the same-principle test system with reduced accuracy and simplified system. That is, instead of directly capturing CH, the response of the particulate matter soot in the R channel is used to perform calculation correction in the G channel, and the correction coefficient is the R intensity response area ratio. In this case, there is an intensity ratio λ, and by comparing response values of 3 channels at 430nm and 516nm, it is considered that only the B channel response is considered at 430nm, two channels B, G are considered at 516nm, and the root (>550nm) is considered to perform intensity removal correction in the G channel by using an area ratio of 550 to 700 nm.

According to the invention, the built test system is established, and the CH self-luminous flame area, the C2 self-luminous flame area, the particulate matter soot generation area and the in-cylinder flame air-fuel ratio distribution area are calculated while the in-cylinder color flame picture is obtained, so that the method is rapid and efficient; the global flame air-fuel ratio is obtained on the premise of not losing the original color image, the cost is greatly reduced compared with other measuring methods, and the method can be widely applied to various flame testing occasions.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims

1. A digital image measuring method based on local air-fuel ratio of flame in an engine cylinder is characterized by comprising the following steps:

(3) calculating the intensity in the channel;

2. The method of claim 1, wherein the high speed color camera has a red (R) channel, a green (G) channel, and a blue (B) channel.

3. The method of claim 2, wherein the image multiplier has CH channels and original channels.

4. The method of claim 3, wherein the CH channels are collocated with 430nm band pass filters, and the original channels are not added with any filters.

5. The method of claim 2, wherein the image multiplier has CH channels, C2 channels, and original channels.

6. The method of claim 5, wherein the CH channel is configured with a 430nm bandpass filter, the C2 channel is configured with a 516nm bandpass filter, and the original channel is not supplemented with any filters.

7. The method of claim 4, wherein in step (3), the CH channel directly extracts the flame CH intensity distribution, the intensity in the blue (B) channel is calculated using an image processing process, the intensity in the blue (B) channel is calculated C2, and the flame C2 intensity distribution is extracted.

8. The method of claim 6, wherein in step (3), the CH channel directly extracts the intensity distribution of the flame CH, and the C2 channel extracts the intensity distribution of the flame C2.

9. The method according to claim 4, characterized in that in step (3) the intensity distribution of the particles root is calculated using the red (R) channel.

10. The method according to any one of claims 7 to 9, wherein in step (4), the intensity distribution ratios of CH and C2 are used in combination with the air-fuel ratio of the standard flame to establish a single functional relationship between CH/C2 and the air-fuel ratio.