JP7328911B2 - Mixed state analysis method of mixed gas in engine - Google Patents

Description

The present invention relates to a mixture state analysis method of a gas mixture (air-fuel mixture) using a laser-induced fluorescence method (LIF method), which is used, for example, for analysis of an air-fuel mixture in an engine cylinder.

In an internal combustion engine, the state of mixture of fuel and air in the cylinder is an important factor that is directly linked to combustibility. Visually grasping the state of mixture is useful in improving the intake structure and ignition control. is. Therefore, the laser-induced fluorescence method (LIF method) is used to visually analyze the state of the air-fuel mixture in the cylinder.

That is, in this method, a test cylinder made of a transparent body such as glass is used, and a fluorescent agent that emits light when irradiated with a laser beam is added to the fuel, and the cylinder is irradiated with the laser beam. A fluorescent agent is made to emit light, and this is photographed by a CCD camera, and the mixing state of the fuel is visually grasped from the luminance (illuminance) of the fluorescent agent (for example, Patent Document 1, Non-Patent Document 1).

JP-A-11-94828 R&D Review of Toyota CRDL Vol. 36 No. 4 pp. 27-34 "Analysis of Combustion Variation in Direct Injection Gasoline Engine by LIF (Laser Induced Fluorescence)"

By the way, the combustion of fuel in the cylinder is closely related to the air-fuel ratio, and when performing flame propagation analysis, knocking analysis, cylinder cooling performance analysis by fuel vaporization latent heat, etc., the throttle opening and fuel It is important to know the air-fuel ratio distribution in the cylinder in relation to the injection amount, crank angle, and the like.

However, with the conventional analysis method using the LIF method, although it is possible to compare which part of the cylinder has more fuel and which part has less fuel, it is not possible to grasp the distribution of the absolute value of the air-fuel ratio. It is difficult to predict what kind of combustion will occur in each part, and for this reason, there has been an aspect of insufficient contribution to improving the structure and control mode of the engine.

The present invention has been made against such a background, and aims to realize a method that can provide valuable analysis results while using the LIF method.

The present invention is a method for analyzing the state of mixture of fuel and air in an engine by a laser-induced fluorescence method.
"As a preliminary measurement, a mixed gas with a known mixture ratio of fuel and air is used as a reference mixed gas, and a fluorescent agent that emits light when irradiated with a laser beam is homogeneously mixed with the mixed gas. and set the luminance at this time as the reference luminance,
Next, as the main measurement for measuring the mixing state of the measurement gas, which is a mixture of the fuel injected from the main injector and the air that has passed through the throttle valve, the measurement gas mixed with the fluorescent agent is flowed over the object and the camera and measuring the actual measured brightness of the required site, and comparing the actual measured brightness with the reference brightness to grasp the mixing ratio of the required site in the object ,
In said preliminary measurement, fuel injection is carried out using an auxiliary injector that allows an accurate measurement of the amount of fuel to be injected."
It is configured.

The invention of the present application is preferably applied to analysis of air-fuel mixture in a cylinder, as in Patent Document 1 and Non-Patent Documents. In this case, preliminary measurement is performed with air-fuel ratios of a plurality of values (for example, three or more air-fuel ratios of the stoichiometric air-fuel ratio and the appropriately set rich air-fuel ratio and lean air-fuel ratio). By grasping reference luminances corresponding to a plurality of air-fuel ratios and comparing the actual measured luminance of each part of the object with each reference luminance, the absolute value of the air-fuel ratio at each part in the cylinder can be grasped.

The concentration distribution of the air-fuel mixture in the cylinder changes depending on the opening of the intake valve and the movement of the piston. Therefore, by recording the brightness corresponding to the change in the crank angle both in the preliminary measurement and the main measurement, it is possible to grasp how the air-fuel ratio changes at each part in the cylinder.

In the present invention, the numerical values of the reference luminance and the actual measured luminance do not necessarily need to be displayed as numbers such as the air-fuel ratio, and may be displayed as indices (the absolute value of the mixture ratio such as the air-fuel ratio). It is sufficient if the corresponding relationship can be accurately grasped.). Also, in the present invention, a plurality of cameras with different photographing directions can be used. As a result, it is possible to three-dimensionally grasp the mode and movement of the mixed gas.

In the present invention, by comparing the reference luminance and the measured luminance, the absolute value of the mixture ratio can be grasped from the luminance of each part of the non-uniformly mixed mixed gas (air mixture) . This makes it possible to accurately predict or grasp the behavior of the air-fuel mixture. As a result, more realistic designs can be realized in improving the structure and control of objects.

For example, by applying it to the analysis of the air-fuel mixture in the cylinder, it is possible to grasp the air-fuel ratio in which part of the cylinder, so it is possible to improve the opening and closing control of the intake valve and promote the generation of tumble flow. This can greatly contribute to the formulation of improvements to the intake port and piston structure, injector placement and injection timing, ignition timing adjustment control to prevent knocking, and changes to the shape of the piston. Further, since the conventional LIF device can be used as it is, the increase in cost can be suppressed.

It is a diagram showing the apparatus of the embodiment, (A) is a schematic plan view, (B) is a schematic front view of (A) as seen from BB. Schematic diagrams showing preliminary measurement results, (A) is an imaging diagram in the lean state, (B) is a graph showing the relationship between the air-fuel ratio and the crank angle in the lean state, and (C) is an imaging diagram in the stoichiometric state. , (D) is a graph showing the relationship between the air-fuel ratio and the crank angle in the stoichiometric state, (E) is an imaging diagram in the rich state, and (F) shows the relationship between the air-fuel ratio and the crank angle in the rich state. Graph, R0 is a captured view of a reference image in a stoichiometric state, R1 is a captured view of a reference image in a lean state, and R2 is a captured view of a reference image in a rich state. It is the graph which corrected and superimposed the preliminary measurement result of each state. (A) is a schematic imaging diagram in the main measurement, R0 is an imaging diagram of a reference image in a stoichiometric state, and R3 is an imaging diagram of a reference member in the main measurement. 4 is a graph showing the relationship between air-fuel ratio and crank angle in this measurement. FIG. 6 is a comparison graph in which FIG. 3 and FIG. 5 are superimposed;

Next, embodiments of the present invention will be described based on the drawings. This embodiment is applied to a method of analyzing an air-fuel mixture in a cylinder of a port injection type internal combustion engine.

(1) Description of Analysis Device As shown in FIG. 2 and a camera (CCD camera) 3 for photographing the engine 1 for measurement. The laser emitter 2 is, for example, Nd. A YAG laser emitter is used, but a _CO2 laser emitter, a semiconductor laser emitter, or the like can also be used.

The measuring engine 1 includes a cylinder 4 having a cylinder bore 4a and a piston 4b, and an intake port 5 and an exhaust port 6 integrated therein. is opened and closed by an exhaust valve 8. Since this embodiment analyzes the state of the air-fuel mixture inside the cylinder 4, at least the cylinder bore 4a is made of a transparent material such as glass. An intake manifold 10 having a surge tank 9 is connected to the intake port 5 , and a throttle valve 11 is fixed to the surge tank 9 . An intake pipe 12 is connected to the throttle valve 11, and intake air is sent to the intake pipe 12 from an air cleaner (not shown).

A main injector 13 for fuel injection faces the intake port 5. A delivery pipe 13a is connected to the main injector 13, and a fuel tank 14 is connected thereto by a hose. An auxiliary injector 15 for injecting fuel is connected to the intake pipe 12, and the auxiliary injector 15 is also connected to the fuel tank 14 by a hose.

A laser beam is incident on the cylinder 4 from a horizontal direction perpendicular to the bore axis. The cylinder 4 is irradiated from the horizontal direction orthogonal to the bore axis through the bore. Therefore, the attitude of the laser emitter 2 can be set arbitrarily. The camera 3 is arranged so as to photograph the cylinder 4 from a horizontal direction substantially perpendicular to the irradiation direction of the laser light. Incidentally, the incident direction of the laser beam and the arrangement position of the camera 3 can be changed according to the purpose.

While the irradiation range of the laser beam is slightly wider than that of the cylinder 4, the field of view of the camera 3 is also slightly wider than that of the cylinder 4. A reference member 18 that can be photographed by the camera 3 while being incident is arranged. Therefore, the camera 3 can simultaneously photograph an image of the cylinder 4 and an image of the reference member 18 (reference image). The surface of the reference member 18 is coated with a reflecting material (for example, bleaching agent) that emits light with brightness proportional to the intensity of the laser light.

The analysis device includes a personal computer 19 as an example of data processing means for executing image processing and the like. Reference numeral 19a denotes a personal computer main body, reference numeral 19b denotes a monitor, and reference numeral 19c denotes a keyboard. Although not shown, the laser emitter 2, the throttle valve 11, and the control valves of the injectors 13 and 15 are connected to the personal computer main body 19a. By horizontally turning the engine 1 for measurement, it is possible to photograph the cylinder 4 from different arbitrary directions with one camera 3 .

(2) Measurement Mode In this embodiment, the fuel in the fuel tank 14 contains a fluorescent agent that emits light by laser light. It is possible to visually grasp the distribution of fuel concentration in the air-fuel mixture. In FIGS. 2 and 4, captured images are schematically shown by hatching.

In this embodiment, preliminary measurement is first performed as a specific analysis procedure. In this preliminary measurement, by injecting the fluorescent-containing fuel into the intake pipe 12 from the auxiliary injector 15 shown in FIG. to shoot.

In this case, the fuel injection amount can be accurately controlled by the auxiliary injector 15, while the intake air injection amount can be accurately controlled by the throttle valve 11. Therefore, the fuel is in a rich state (e.g., A/ F = 12.0)), a stoichiometric air-fuel ratio state (A/F = 14.7), and a fuel-lean state (for example, A/F = 17.0). Three standard air-fuel mixtures are set as standard air-fuel mixtures, and preliminary measurements are performed for each of the three standard air-fuel mixtures to measure the standard brightness. In FIG. 2, (C) indicates the stoichiometric state, (A) indicates the lean state, and (E) indicates the rich state. It is possible to set a plurality of reference air-fuel mixtures for both the lean state and the rich state.

Since the density of the fuel is different in the three reference states, the luminance (illuminance) of the image appears darker (light is emitted strongly) in the order of the lean state, the stoichiometric state, and the rich state, but since the fuel is evenly mixed, In either state, the image appears at the same brightness throughout. Therefore, the relationship between the crank angle and the reference luminance is graphed by recording the luminance of the image intermittently or continuously while rotating the crankshaft (not shown) and recording the luminance of the image as the reference luminance. ((B), (D) and (F) of FIG. 2).

In this case, the graphs (B), (D), and (F) are displayed so that the luminance increases as the crank angle increases, but this is a display for convenience, and in reality, the piston 4b Depending on the relationship between the movement of the engine and the amount of intake air, the relationship may be non-linear or downward to the right (during the compression stroke, the brightness increases as the crank angle increases). However, since the amount of intake air is the same in any reference state, each graph shows the same trend line. In the graphs (B), (D), and (F), the vertical axis represents luminance, but it is also possible to display it as an air-fuel ratio or simply as a comparison index.

Now, since the pulse fluctuation of the laser light emitter is large and the intensity of the laser light is likely to change, the intensity of the laser light changes each time it is measured, and even if the air-fuel ratio is the same, the amount of light emitted by the fluorescent material changes. There is a risk. As a result, the relationship between image brightness and fuel concentration (air-fuel ratio) may not be constant as images are repeatedly captured, making it difficult to accurately display the fuel concentration as the absolute value of the air-fuel ratio.

Regarding this point, in the present embodiment, for example, the brightness of the reference image in the first measurement of the day is set as the reference brightness, and in subsequent measurements, the actual brightness of the reference image and the reference brightness are compared, and if there is a difference, a correction is made to increase or decrease the brightness of the air-fuel mixture image based on the difference. In the embodiment, the measurement in the stoichiometric state is performed first, and the brightness of the reference image at this time is taken as the reference brightness X0.

In the lean state of FIG. 2B, the actual brightness X1 of the reference member 18 is higher than the reference brightness X0 by E1, so correction is performed to shift the graph of the measured brightness of the air-fuel mixture downward by E1. Similarly, in the rich state of FIG. 2(F), the actual luminance X2 of the reference member 18 is lower than the reference luminance X0 by E2, so correction is performed to shift the measured luminance graph upward by E2. . By these corrections, it is possible to obtain the same graph for each reference luminance as measured with laser light of the same intensity, enabling accurate comparison.

In FIG. 3, three graphs after correction of the reference luminance are superimposed on one. (For example, the brightness (vertical axis) of the graph can be converted to the air-fuel ratio, so when the air-fuel mixture in a specific part of the cylinder is at a specific crank angle, It is possible to grasp the degree of air-fuel ratio.).

In this measurement, fuel is injected from the main injector 13 and the air-fuel mixture is photographed by the camera 3 in the same state as the actual inside of the cylinder 4 . In FIG. 3(A), an image is schematically displayed. A portion with a high density of shading is a portion with a high concentration of fuel, and a portion with a low shading density is a portion with a low concentration of fuel.

The brightness of the image can be quantified for any part, and since the brightness can be converted to the air-fuel ratio as described above, the absolute value of the air-fuel ratio for each part with different brightness can be obtained by comparing with the numerical values in the graph of FIG. value can be known.

Even in this actual measurement, the intensity of the laser light may change, so as schematically shown in FIG. and X0, the measured luminance is corrected by the difference E3. Then, by superimposing the value of the measured brightness after correction and the reference value in FIG. 3, the comparison graph shown in FIG. be able to.

As described above, in this embodiment, the air-fuel mixture homogenized to a specific concentration in the preliminary measurement is used and its luminance is set as the reference luminance. Thus, the absolute value of the air-fuel ratio can be known. Therefore, it is possible to accurately estimate or grasp the distribution of the actual amount of fuel, the state of flame propagation, and the like. As a result, improvements such as improvement of tumble flow and prevention of knocking can be accurately performed.

In this embodiment, the reference member 18 is imaged together with the cylinder 4 in each measurement to correct the concentration of the air-fuel mixture. does not require such a response. As means for obtaining a homogeneous air-fuel mixture in the preliminary measurement, an auxiliary injector may be provided in the surge tank, and a stirring means may be provided in the surge tank.

Although the embodiments of the present invention have been described above, the present invention can be embodied in various other ways. For example, by photographing an object such as a cylinder from different locations with a plurality of cameras, it is possible to know the three-dimensional density distribution without moving the object.

Although the above embodiment is applied to the analysis of the concentration distribution of the air-fuel mixture , it is also possible to analyze the flow of the EGR gas or blow-by gas by adding an atomized fluorescent agent to the EGR gas or blow-by gas. is also possible. It can also be applied to the analysis of the air-fuel mixture flow at the intake port.

INDUSTRIAL APPLICABILITY The present invention can be embodied in a method for analyzing a mixed state of mixed gas in an engine. Therefore, it can be used industrially.

1 measurement engine 2 laser emitter 3 camera 4 cylinder 5 intake port 6 exhaust port 9 surge tank 11 throttle valve 12 intake pipe 13 main injector 14 fuel tank 15 auxiliary injector 16 mirror 17 condenser lens 18 reference member 19 data processor Personal computer as an example

Claims (1)

A method for analyzing the state of mixture of fuel and air in an engine by a laser-induced fluorescence method,
As a preliminary measurement, a mixed gas with a known mixture ratio of fuel and air is used as a reference mixed gas, and a fluorescent agent that emits light when irradiated with a laser beam is mixed homogeneously with the mixed gas. Set the luminance at the time of leverage as the reference luminance,
Next, as the main measurement for measuring the mixing state of the measurement gas, which is a mixture of the fuel injected from the main injector and the air that has passed through the throttle valve, the measurement gas mixed with the fluorescent agent is flowed over the object and the camera and measuring the actual measured brightness of the required site, and comparing the actual measured brightness with the reference brightness to grasp the mixing ratio of the required site in the object ,
In said preliminary measurement, fuel injection is performed using an auxiliary injector capable of accurately measuring the amount of fuel to be injected.
A mixed state analysis method for mixed gas in an engine.

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