CN112465744B

CN112465744B - Digital image measurement method based on local air-fuel ratio of flame in engine cylinder

Info

Publication number: CN112465744B
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: 2023-05-12
Anticipated expiration: 2040-10-23
Also published as: CN112465744A

Abstract

The invention discloses a digital image measurement method based on the local air-fuel ratio of flame in an engine cylinder, which relates to the technical field of engine cylinder combustion diagnosis of automobiles and the like, and aims at a color camera sensor to calibrate CH, CH2 and self-luminescence in flame to obtain corresponding signal intensity, and the corresponding signal intensity is combined with a RGB channel response value of a color camera, and the calibration is carried out by using different air-fuel ratio premixed standard flames, so that the color camera is changed into a device which can measure the CH, the C2 and the self-luminescence flame region of each pixel aiming at the whole image and generates different air-fuel ratios of a region of particulate matters. By implementing the invention, the global 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 invention can be widely applied to various flame testing occasions.

Description

Digital image measurement 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 aeroengine cylinder, in particular to a digital image measurement method based on the local air-fuel ratio of flame in the engine cylinder.

Background

In the design process of a core combustion system of an engine such as an automobile and the like, an advanced image processing method is utilized for capturing and analyzing flame images in a cylinder, so that the design development speed can be effectively improved, and the design of the combustion system is optimized, so that an energy-saving and emission-reducing engine is developed. In the technical field of in-cylinder flame diagnosis systems, the prior art generally utilizes an optical measure to capture and extract in-cylinder flame in combination with a high-speed camera. The international leading practice is generally to perform statistical qualitative analysis on the shape, boundary and intensity of the image, and qualitative analysis of, for example, yellow and blue flames can be performed by using a color camera. In addition, there are also methods for analyzing the composition of an intermediate product of a combustion process by capturing and recording a specific flame product by using different filters in combination with a high-speed camera for an in-cylinder image or by performing spectral analysis of an in-cylinder substance by using a spectrometer. The measurement of flame air-fuel ratio generally requires laser induced fluorescence test of local in-cylinder to obtain accurate local air-fuel ratio through fluorescent calibration of specific tracer substances in the cylinder.

However, flame analysis using a high-speed color camera is currently mainly qualitative analysis, and cannot be quantitatively measured for each pixel (local) air-fuel ratio, losing a lot of information. Although the accurate air-fuel ratio measurement can be performed by using the testing methods such as a laser diagnosis system, a spectrometer and the like, the signal is often received and needs to be matched with an image intensifier and high-speed high-energy laser, so that the obtained image data has low speed, and the flame development process in the engine cylinder cannot be analyzed with the precision of the crank angle. In addition, the method is limited by a complex system, experimental precision, fuel and other factors, and is difficult to be applied to industrialization rapidly and efficiently.

Accordingly, those skilled in the art have been working to develop a digital image measurement method based on the local air-fuel ratio of the flame in the cylinder of an engine, which can calculate the CH self-luminous flame region, the C2 self-luminous flame region, the particulate matter spot generation region, and the in-cylinder flame air-fuel ratio distribution region while obtaining a picture of the 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 above object, the present invention provides a digital image measurement method based on a local air-fuel ratio of flame in an engine cylinder, comprising the steps of:

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

(2) Setting up 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 the test system, and calibrating the standard flame light source as the standard premix flame of the fuel to be tested in different air-fuel ratio states;

(3) Calculating the intensity within the channel;

(4) Establishing a single functional relation between CH and C2 and the air-fuel ratio;

(5) And (5) finishing 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 a CH channel and an original channel.

Further, the CH-channel is matched with a 430nm bandpass filter, and the original channel is not added with any filter.

Further, the image multiplier has a CH channel, a C2 channel, and an original channel.

Further, the CH-channel is equipped with a 430nm bandpass filter, the C2-channel is equipped with a 516nm bandpass filter, and the original channel is not added with any filter.

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

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

Further, in the step (3), the intensity distribution of the particulate matters boot is calculated by using the red (R) channel.

Further, in the step (4), a single functional relationship between CH/C2 and the air-fuel ratio is established by using the intensity distribution ratio of CH and C2 in combination with the air-fuel ratio of the standard flame

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

according to the digital image measurement method based on the local air-fuel ratio of the flame in the engine cylinder, the CH self-luminous flame area, the C2 self-luminous flame area, the particulate matter spot generation area and the air-fuel ratio distribution area of the flame in the cylinder are calculated when the color flame picture in the cylinder 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, the test targets are wide, and various test objects such as an optical engine, an endoscope real engine and other heat engines can be carried on, and even other types of flames can be measured.

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

Drawings

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

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

Detailed Description

The following description of the preferred embodiments of the present invention refers to the accompanying drawings, which make the technical contents thereof more clear and easy to understand. The present invention may be embodied in many different forms of embodiments and the scope of the present invention is not limited to only the embodiments described herein.

In the drawings, like structural elements are referred to by like reference numerals and components having similar structure or function are referred to by like reference numerals. The dimensions and thickness of each component shown in the drawings are arbitrarily shown, and the present invention is not limited to the dimensions and thickness of each component. The thickness of the components is exaggerated in some places in the drawings for clarity of illustration.

Example 1

As shown in fig. 2, the response of the camera at different wavelengths is shown, and the sensor filter response of different cameras is different. The hydrocarbon fuel premixed flame is seen from light sources of C2 and CH, the color camera RGB (red green blue) filter receives corresponding efficiency, and for light with specific wavelength, the relation between the response value alpha and the intensity I of each channel of RGB is as follows:

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the intensity values entering each channel are:

for a premixed flame, the intensity of the three channels is based on the assumption that only light intensity compositions of 430nm and 516nm are assumed:

as shown in fig. 1, the test system built in this embodiment is assembled by a high-speed color camera and a 2-fold image multiplier (Doubler), the camera images are duplicated about 2 times by copying the same image, that is, the image of the object to be tested in two channels of the multiplier is recorded once, one channel is provided with a 430nm band-pass filter in a matching way, the 430nm band-pass filter only allows light of 430nm (i.e. CH wavelength) and the spectrum nearby to pass, and the other channel is not provided with any filter, so that the original flame color image is recorded.

Setting up 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 a test system, and calibrating the standard flame light source as the standard premix flames of the fuel to be tested in different air-fuel ratio states.

The high-speed camera is used for carrying the multiplier, so that CH distribution of the object to be detected, intensity and an original flame color image can be obtained simultaneously. C2 and CH are recorded simultaneously in the B channel, and are combined to a B channel intensity value. 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, so as to calculate the intensity of c2 in the blue (B) channel, to extract the intensity distribution of c2.

Similarly, in the G channel, the particle emission area and the intensity value can be calculated by subtracting the C2 light from the G channel, mainly by using the particle emission value of 550nm or more and the C2 self-luminous intensity value.

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

And (5) finishing the calibration process of the air-fuel ratio prediction calculation. The imaging system can directly carry out optical test diagnosis of the optical engine, and can calculate a CH self-luminous flame area, a C2 self-luminous flame area, a particulate matter spot generation area and an in-cylinder flame air-fuel ratio distribution area by utilizing an image processing calculation method aiming at a particularly high-speed flame recording process, and can realize quantitative prediction of local air-fuel ratio by accurately extracting intensity.

Example 2

The only difference between the apparatus of embodiment 2 and embodiment 1 is that in this embodiment, a 3-pass image multiplier is adopted, that is, a 516nm (c2×wavelength) bandpass filter and a 430nm (ch×wavelength) bandpass filter are simultaneously installed, and the other channel continues to retain the original image without installation, so that the intensity distribution of c2×and ch×can be directly captured, ch×/C2×is calibrated, and the air-fuel ratio is calculated.

Example 3

In this embodiment, the R channel is used to perform auxiliary calculation, and the C2 intensity and the area in the G channel of the particulate matter are calculated first, and then the CH intensity and the area are calculated, so as to obtain the same principle test system with reduced accuracy and simplified system. That is, the response of particulate matters boot in the R channel is calculated and corrected in the G channel without directly capturing CH, and the correction coefficient is the ratio of R intensity to response area. In this case, the intensity ratio λ is calculated by comparing the response values of the 3 channels at 430nm and 516nm, and it is considered that only the B channel response is considered at 430nm, two channels at B, G are considered at 516nm, and the spot (> 550 nm) is considered to perform intensity removal correction in the G channel by using the area ratio of 550 to 700 nm.

According to the invention, a built test system is established, and a CH self-luminous flame area, a C2 self-luminous flame area, a particulate matter spot generation area and an in-cylinder flame air-fuel ratio distribution area are calculated when in obtaining in-cylinder color flame pictures, 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 describes in detail preferred embodiments of the present invention. It should be understood that numerous modifications and variations can be made in accordance with the concepts of the invention without requiring creative effort by one of ordinary skill in the art. Therefore, all technical solutions which can be obtained by logic analysis, reasoning or limited experiments based on the prior art by the person skilled in the art according to the inventive concept shall be within the scope of protection defined by the claims.

Claims

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

step 1, a test system is built, wherein the test system is formed by assembling an image multiplier and a high-speed color camera; the high-speed color camera has a red (R) channel, a green (G) channel, and a blue (B) channel; the image multiplier has an original channel and at least one filter channel, the original channel not adding any filters;

step 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 the test system, and calibrating the standard flame light source as standard premix flames of the fuel to be tested in different air-fuel ratios;

step 3, calculating the intensity in the channel:

when a filter channel of the image multiplier is matched with a 430nm band-pass filter, the filter channel directly extracts the intensity distribution of flame CH, the intensity in the blue (B) channel is obtained by calculation in an image processing process, the intensity of C2 in the blue (B) channel is calculated, and the intensity distribution of flame C2 is extracted; in the green (G) channel, subtracting the intensity of C2 from the intensity of the green (G) channel, and calculating a particulate matter spot light-emitting area and an intensity value;

when a filter channel of the image multiplier is matched and provided with a 430nm band-pass filter and a 516nm band-pass filter, the filter channel directly extracts the intensity distribution of flame CH and the intensity distribution of flame C2;

calculating and correcting in the green (G) channel by using the response of the particulate matters boot in the red (R) channel, wherein the correction coefficient is R intensity;

step 4, establishing a single function relation between CH/C2 and air-fuel ratio;

and 5, finishing the calibration process of the air-fuel ratio prediction calculation.

2. The method for measuring a digital image based on a local air-fuel ratio of a flame in an engine cylinder according to claim 1, wherein in the step 4, a single functional relationship between CH/C2 and the air-fuel ratio is established by using the intensity distribution ratio of CH and C2 in combination with the air-fuel ratio of a standard flame.