JP2015099055A - Combustion analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problem: the amount of soot generated and the amount of soot oxidized cannot be measured separately in conventional two-color method.SOLUTION: A combustion analyzer includes: a light intensity measurement unit 20 which detects light intensities of light emitted from flame and having different two wavelengths λ, λat a predetermined interval; a flame temperature calculation section 31 which determines a flame temperature T from a ratio of the detected light intensities of the two wavelengths; a KL value calculation section 32 which calculates a KL value by use of the determined flame temperature; a soot-generation/oxidization determination section 33 which compares a current flame temperature Twith a previous flame temperature T, and a current KL value KLwith a previous KL value KL; an oxidized soot calculation section 34 which calculates a reduction between the previous KL value and the current KL value, as the amount of soot oxidized, when the current flame temperature is higher than the previous one and the current KL value is smaller than the previous one; and a generated soot calculation section 35 which calculates an increase between the previous KL value and the current KL value, as the amount of soot generated, when the current flame temperature is lower than the previous one and the current KL value is larger than the previous one.

Description

  The present invention relates to an apparatus for analyzing a combustion state in a combustion engine or the like.

  In a combustion engine such as a compression ignition engine, the combustion of fuel in the combustion chamber is performed in order to optimize the shape of the combustion chamber and the intake / exhaust port communicating with the combustion chamber, and the injection timing and pressure of the fuel supplied to the combustion chamber. It is effective to be able to grasp the state in real time. For this purpose, Patent Document 1 proposes a technique for measuring the temperature and KL value of a flame generated in a combustion chamber using a two-color method and acquiring the soot concentration.

  The two-color method described above can calculate the flame temperature and the KL value by measuring the flame brightness at two different wavelengths simultaneously, as is well known in Patent Document 1 and Non-Patent Document 1. is there. Since the KL value is proportional to the flame temperature and the soot concentration, the soot concentration can be determined if the flame temperature and the KL value are known.

JP 2008-144673 A

Japan Society of Mechanical Engineers, Proceedings B, 47, 417

  A flame is generated by the ignition of fuel in the combustion chamber, and the generation of soot and its oxidation occur continuously in the combustion chamber. In this case, the conventional two-color method disclosed in Patent Document 1 cannot essentially grasp the degree of oxidation of soot generated in the combustion chamber. In other words, in the conventional two-color method, only the final soot concentration obtained by subtracting the oxidation amount from the soot production amount can be grasped, and the degree of soot oxidation produced cannot be measured separately. There was a problem.

  An object of the present invention is to provide a method capable of continuously measuring in real time the oxidation state of soot generated as fuel is burned in a combustion engine, and an apparatus capable of implementing this method. It is in.

  The first aspect of the present invention relates to light emitted from a flame, a light intensity measuring device that detects light intensities of two different wavelengths at regular intervals, and a ratio of the detected light intensities of two wavelengths in a reference object. A flame temperature calculation unit for calculating a flame temperature by comparing with the ratio of the light intensity of the same two wavelengths, a KL value calculation unit for calculating a KL value using the flame temperature obtained by the flame temperature calculation unit, and this time A soot generation / oxidation determination unit that determines whether or not the calculated flame temperature is lower than the previously calculated flame temperature and at the same time whether or not the currently calculated KL value is greater than the previously calculated KL value; Based on the determination result in the soot generation / oxidation determination unit that the flame temperature is higher than the flame temperature obtained last time and the KL value calculated this time is smaller than the previously calculated KL value, the previously calculated KL value is KL value calculated for this time The soot oxidation amount calculation unit that calculates the reduction amount as the amount of soot oxidation, and the flame temperature calculated this time is lower than the flame temperature calculated last time and the KL value calculated this time is larger than the KL value calculated last time And a soot generation amount calculation unit that calculates an increment of the KL value calculated this time as a generation amount of soot based on a determination result in the soot generation / oxidation determination unit. It is in the combustion analyzer.

  In the present invention, unburned fuel in a flame exposed to high temperature and oxygen shortage generates a soot precursor through a dehydrogenation reaction by pyrolysis, that is, carbonization, and this soot precursor aggregates and coalesces. Become a trap. Since this reaction is an endothermic reaction, the flame temperature at the location where the soot precursor is generated will decrease. When oxygen is introduced into the flame generated by soot, the soot burns and oxidizes, increasing the flame temperature. That is, in the place where soot is generated, the flame temperature is lowered and the KL value is increased due to the generation of soot, whereas in the place where the soot is oxidized, the flame temperature is increased and the KL value is also lowered due to the reduction of soot.

  The second aspect of the present invention relates to the radiation light from the flame, the step of detecting the light intensities of two different wavelengths at regular intervals, and the ratio of the detected light intensities of the two wavelengths to the same two in the reference object The step of obtaining the flame temperature by comparing with the ratio of the light intensity of the wavelength, the step of calculating the KL value using the obtained flame temperature, and whether or not the flame temperature obtained this time is lower than the flame temperature obtained last time. A step of determining, a step of determining whether or not the KL value calculated this time is larger than the KL value calculated last time, the flame temperature calculated this time is lower than the flame temperature calculated last time, and the KL value calculated this time is When it is determined that the KL value is larger than the previously calculated KL value, a step of determining that soot is generated by an increment of the KL value calculated this time with respect to the KL value calculated last time, and the flame temperature calculated this time were previously determined. When it is determined that the KL value calculated above is higher than the flame temperature and the KL value calculated this time is smaller than the KL value calculated last time, the soot is oxidized by the decrease of the KL value calculated this time with respect to the KL value calculated last time. A combustion analysis method characterized by comprising the step of determining.

  According to the present invention, it is possible to continuously acquire not only the amount of soot generation but also the amount of soot oxidation by acquiring time-series changes in flame temperature and KL value.

It is a block diagram showing typically one embodiment of a combustion analysis device by the present invention. It is a conceptual diagram of the part of the light intensity measuring device in the embodiment shown in FIG. It is a flowchart showing the flame analysis procedure in embodiment shown in FIG. It is a schematic diagram of the flame which becomes a swirl in the combustion chamber of a compression spark ignition engine. In the embodiment shown in FIG. 1, it is a graph showing the relationship between the value which subtracted the soot oxidation amount from the soot production amount, and soot discharge amount. It is a conceptual diagram of other embodiment of a light intensity measuring device. It is a conceptual diagram of another embodiment of a light intensity measuring device.

  An embodiment in which a combustion analysis apparatus according to the present invention is applied to a compression ignition internal combustion engine will be described in detail with reference to FIGS. However, the present invention is not limited to such an embodiment, but can be applied to other combustion engines such as a spark ignition type internal combustion engine.

A combustion analysis apparatus according to this embodiment is schematically shown in FIG. 1, and a schematic configuration of the light intensity measuring instrument is schematically shown in FIG. That is, the combustion analysis apparatus 10 in the present embodiment is based on the light intensity measuring device 20 that detects the light intensities of two different wavelengths λ ₁ and λ ₂ at regular intervals, and information from the light intensity measuring device 20. And an analysis unit 30 for continuously calculating the amount of soot produced and the amount of oxidation.

The light intensity measuring device 20 in the present embodiment is set so that the beam splitter 21 that divides the emitted light from the flame F into two directions, the pair of interference filters 22 ₁ and 22 _2, and the imaging region for the flame F are the same. And a pair of high-speed monochrome video cameras 23 ₁ and 23 ₂ . First interference filter 22 ₁ is one of a pair of interference filters 22 _1, 22 _2, of the one of the radiation derived from the beam splitter 21, which transmits only the first radiation at a wavelength lambda _1. One first monochrome video camera 23 ₁ is a pair of monochrome video camera 23 _1, 23 _2, and the light intensity of the first wavelength lambda ₁ of the emitted light which has passed through the first interference filter 22 ₁ is measured This is output to the flame temperature calculation unit 31 of the analysis unit 30. The second interference filter 22 ₂ , which is the other of the pair of interference filters 22 ₁ and 22 ₂ , transmits only the radiation light having the second wavelength λ ₂ among the other radiation light guided from the beam splitter 21. The second monochrome video camera 23 ₂ , which is the other of the pair of monochrome video cameras 23 ₁ and 23 ₂ , measures the light intensity of the emitted light having the second wavelength λ ₂ that has passed through the second interference filter 22 _2. This is output to the flame temperature calculation unit 31 of the analysis unit 30.

The analysis unit 30 in the present embodiment includes a flame temperature calculation unit 31, a KL value calculation unit 32, a soot generation / oxidation determination unit 33, a soot oxidation amount calculation unit 34, and a soot generation amount calculation unit 35.
The flame temperature calculation unit 31 compares the detected light intensity ratio of the _two wavelengths λ ₁ and λ _{2 with} the light intensity ratio of the same two wavelengths λ ₁ and λ _{2 in} the reference object to obtain the flame temperature T. This is output to the KL value calculation unit 32 and the soot generation / oxidation determination unit 33. Therefore, the flame temperature calculation unit 31 stores a map indicating the relationship between the temperature and the ratio of the light intensity of the same two wavelengths λ ₁ and λ _{2 in} the reference object, that is, the black body.

In the two-color method, when attention is paid to the luminance of two wavelengths among the spectral radiation of a black body and other general objects, and two appropriate wavelengths that are close to each other are selected, the emissivities of the two are almost the same. When the premise that the emissivity of two wavelengths is equal in a general object holds, the ratio of the luminance is equal to the ratio of the luminance of the two wavelengths in the black body. Therefore, the ratio of the luminance of the measurement object is obtained and compared with the luminance ratio of the black body measured in advance, and the temperature of the black body having the same luminance ratio can be regarded as the temperature of the measurement object. Become. The flame temperature calculation unit 31 in the present embodiment calculates the ratio of the luminance of two different wavelengths λ ₁ and λ ₂ measured by the light intensity measuring device 20 with respect to the flame F to be measured. Then, the calculated ratio is compared with the luminance ratio data at the same wavelength λ ₁ and λ ₂ in the black body stored in advance, and the temperature of the black body having the same luminance ratio is read as the flame temperature T. Yes. For this reason, the emitted light from the standard light source is imaged in advance using the same optical system as the light intensity measuring instrument 20 used in flame imaging under the same imaging conditions. The two wavelengths lambda _1, the brightness value of an image for lambda _2, respectively wavelengths lambda _1, corresponding to lambda ₂ (4) expression of A, and calculates the B, should be stored in the flame temperature calculation section 31 .

The KL value calculation unit 32 calculates the KL value using the flame temperature T obtained by the flame temperature calculation unit 31. In general, the intensity E _{0 (λ, T)} of the radiant light from a black body such as a kite has a wavelength λ, a flame temperature T, and a black body radiation first constant (3.74 × 10 ⁻¹⁶ ) c ₁ When the black body radiation second constant (1.44 × 10 ⁻² ) is represented by c ₂ , it can be described as follows from the Wien approximation.
E _{0 (λ, T)} = c ₁ λ ⁻⁵ · exp (−c ₂ / λT) (1)

Here, when the emissivity of a flame that is not a black body is represented by ε _λ , the intensity E _{(λ, T)} of the radiant light of the flame is expressed by the following equation (2).
E _{(λ, T)} = ε _λ E _{0 (λ, T)} = ε _λ c ₁ λ ⁻⁵ · exp (−c ₂ / λT) (2)

Further, the brightness temperature of the black body that correspond to the brightness of the flame at the wavelength λ is represented by T _a, (1) formula can be modified as the following equation (3).
E _{(λ, T)} = ε _λ E _{0 (λ, Ta)} = c ₁ λ ⁻⁵ · exp (−c ₂ / λT _a ) (3)
Here, when a proportional relationship is established between the luminance value X of an image taken by a high-speed video camera or the like and the intensity E _{(λ, T)} of the flame radiation, that is, E _{(λ, T)} = k · X is established. Assume. In this case, when represented by −λ / c ₂ = A and (λ / c ₂ ) · ln (c ₁ / λ ⁵ k) = B, the equation (3) is transformed into the following equation (4): Can do.
1 / T _a = A · ln (E _{(λ, T)} ) + B (4)

On the other hand, Hottel and Broughton have proposed the following equation (5) for flame radiation.
ε _λ = 1−exp (−KL / λα) (5)

Here, K is an absorption coefficient proportional to the concentration of soot in the flame, L is the thickness of the flame with respect to the direction in which the radiant light is detected, α is an index representing the wavelength dependence of the emissivity, and visible range Then it becomes 1.38. That is, the KL value is an integral value of the soot concentration in the depth direction of the flame for detecting the radiation light. Solving for KL using Equation (5) and Equations (2) and (3), the following Equation (6) is obtained.
KL = −λα · ln [1-exp [− (c ₂ / λ) · {(1 / T _a ) − (1 / T)}]] (6)

  Therefore, the KL value can be calculated from the flame temperature T obtained for a flame that is not a black body, using the above equation (6).

The soot production / oxidation determination unit 33 determines whether or not the flame temperature T _n obtained this time is lower than the flame temperature T _n−1 obtained last time, and at the same time the KL value KL _n calculated this time is the KL value KL calculated last time. _It is determined whether it is larger than _n-1 .

The soot oxidation amount calculation unit 34 generates soot when the current flame temperature T _n is higher than the previous flame temperature T _n−1 and the current KL value KL _n is smaller than the previous KL value KL _n−1. - based on the determination result in the oxidation determination unit 33 calculates the decrease in the current KL value KL _n as oxidation of soot.

The soot generation amount calculation unit 35 generates soot when the current flame temperature T _n is lower than the previous flame temperature T _n−1 and the current KL value KL _n is greater than the previous KL value KL _n−1. - based on the determination result in the oxidation determination unit 33 calculates the increment of the current KL value KL _n as the amount of soot.

More specifically, the flame image taken by the optical intensity measurement device 20 at a constant shooting period t _n set in advance, the flame temperature for each pixel of the captured image at the flame temperature calculation unit 31 and the KL value calculating section 32 seek and T _n and the KL value KL _n. Next, the flame temperatures T _n and T _n−1 and the KL values KL _n and KL _n−1 at the time t _n and the time t _n−1 are compared with the same coordinates on the image. When the KL value increases and the flame temperature decreases, it is determined that an endothermic reaction has occurred due to the generation of soot, and the increase in the KL value is taken as the amount of soot generation. If the KL value decreases and the flame temperature increases, it is determined that an exothermic reaction has occurred due to soot oxidation (reburning), and the decrease in the KL value is taken as the amount of soot oxidation. Note that a change in the KL value other than the above condition can be regarded as a change due to the entry of the heel to the same coordinate or the movement of the heel from the same coordinate. By performing the above routine between each pixel and each time on the image, it is possible to measure the spatial distribution and time-series data for the amount of soot produced and the amount of oxidation.

In this embodiment, a pair of high-speed monochrome video cameras 23 ₁ and 23 ₂ is used, but a high-speed color video camera can also be used. In this case, the beam splitter 21 and the pair of interference filters 22 ₁ and 22 ₂ are not required, and the light intensity measuring device 20 can be configured with only one color video camera. When using a color video camera, the brightness value of the flame image for light of two different wavelengths by using at least two of the RGB signals (for example, R and G, R and B, or G and B), That is, the light intensity may be detected. Usually, the center wavelength of the R signal of the color video camera is 700 nm, the G signal is 546 nm, and the B signal is set around 435 nm. Therefore, for example, by extracting the luminance of the R signal and the G signal, it is possible to detect the light intensities of two different wavelengths.

The flame analysis procedure in the present embodiment will be described with reference to the flowchart shown in FIG. 3. First, in step S11, the light intensity of the flame F is detected at two different wavelengths λ ₁ and λ ₂ , and in step S12. The flame temperature T _n and the KL value KL _n are calculated. Then, it is determined whether or not the flame temperature T _n and KL value KL _n the calculated time is the first time in S13 step determines that here now calculated flame temperature T _n and KL value KL _n is the first time If so, the process returns to step S11 to repeat the above-described processing. The calculation of the flame temperature _{T n} and KL value KL _n at step S12, the flame temperature calculation section 31, KL value calculating section 32, soot generation and oxidation determining unit 33, soot oxidation amount calculating section 34, the soot generation amount The calculation is performed continuously at a predetermined cycle t _n according to the calculation cycle in the calculation unit 35.

If it is determined that the flame temperature T _n and the KL value KL _n calculated this time in step S13 are the second and subsequent times after starting this process, the process proceeds to step S14 and the flame temperature T calculated this time is determined. _n is equal to or the same as the flame temperature T _n-1 previously obtained. Here, it is determined that the present flame temperature T _n is the same as the previous flame temperature T _n−1 , that is, the flame temperature is not changed, so that neither generation of soot nor oxidation of soot has occurred substantially. In that case, the process returns to step S11 and the above-described processing is repeated again.

On the other hand, if it is determined in step S14 that the current flame temperature T _n is different from the previous flame temperature T _n−1 , the process proceeds to step S15 and the flame temperature T _n obtained this time is determined. It is determined whether or not it is lower than the flame temperature _Tn-1 obtained last time. Here, lower than the flame temperature T _n-1 of this flame temperature T _n is the last, that is, when the flame temperature T _n is determined to be decreased, in turn calculated this time and proceeds to S16 in step the KL value KL _n determines whether larger or not than the KL value _{KL n-1} previously calculated. Here, when it is determined that the current KL value KL _n is larger than the previous KL value KL _n−1 , that is, soot is generated as the flame temperature decreases, the process proceeds to step S17. Then, the amount of decrease in the current KL value KL _n with respect to the previous KL value KL _n−1 is calculated as the amount of soot oxidation.

This flame temperature T _n in the previously described step S15 is higher than the flame temperature T _n-1 of the previous, that is, when the flame temperature T _n is determined to have risen, the process proceeds to S18 in step. In step S18, it is determined whether or not the KL value KL _n calculated this time is smaller than the previously calculated KL value KL _n-1 . Here, when it is determined that the current KL value KL _n is smaller than the previous KL value KL _n−1 , that is, the soot is oxidized as the flame temperature T _n increases, the process proceeds to step S19. Then, the amount of decrease in the current KL value KL _n with respect to the previous KL value KL _n−1 is calculated as the amount of soot oxidation.

_{If it} is determined in step S16 that the current KL value KLn is less than or _equal to the previous KL value KLn _-1 , that is, neither soot generation nor soot oxidation occurs substantially, the process proceeds to step S11. Return and repeat the process described above. Similarly, if it is determined in step S18 that the current KL value KLn is _equal to or greater than the previous KL value KLn _-1 , that is, neither generation of soot nor oxidation of soot has occurred. The process described above is repeated again.

  In addition, after executing the steps of S17 and S19, the steps after S11 are repeated again, and the amount of soot generated and the amount of soot oxidation are calculated cumulatively in the steps of S17 and S19, respectively. The

By the way, in the combustion chamber of the internal combustion engine, the flame moves due to the swirl flow generated in the combustion chamber. Therefore, when this flame is analyzed using the combustion analysis device 10 of the present invention, an image obtained by the light intensity measuring device 20 is obtained. It is necessary to correct for the above. That is, when comparing the flame temperatures T _n and T _n−1 and the KL values KL _n and KL _n−1 at the current calculation time t _n and the previous calculation time t _n−1, the flame moves by the swirl flow. It is necessary to correct the position of the comparison coordinates by the amount, and this will be schematically described with reference to FIG. The image of the flame F at the previous calculation time t _n-1 indicated by the two-dot chain line, the moving direction of the image swirl flow S of the flame F in the current calculation time t _n indicated by the solid line after moving by the swirl flow S The images of the two flames F may be overlapped by moving in the opposite direction.

  FIG. 5 shows the analysis result of the flame F according to the present embodiment, which is obtained by subtracting the cumulative oxidation amount of soot calculated using the combustion analysis apparatus 10 according to the present embodiment on the horizontal axis. The actual amount of soot discharged is taken on the vertical axis. In FIG. 5, it is clear from the fact that a linear proportional relationship is obtained between the calculated soot generation amount and the actual soot discharge amount. You will be able to confirm that the measurement results are valid.

  Regarding the configuration of the light intensity measuring instrument 20 described above, any configuration other than the present embodiment can be adopted, and examples include those shown in FIGS. 6 and 7.

The light intensity measuring device 20 shown in FIG. 6 includes a single high-speed monochrome video camera 23, a stereo adapter 24 for taking an image by dividing it into the focal plane of the monochrome video camera 23, and a pair of Interference filters 22 ₁ and 22 ₂ are provided. The stereo adapter 24 is a combination of two sets of reflecting mirrors 25 ₁ and 25 ₂ that are symmetrically arranged on one side and the other side about the optical axis of the monochrome video camera 23. In this embodiment, half of the images of the flames F having the _two wavelengths λ ₁ and λ ₂ are formed on the focal plane of one monochrome video camera 23, and the resolution of the flame F is reduced to 1/2. End up. However, even if there is only one monochrome video camera 23, the light intensity measuring device 20 can be configured by combining the interference filters 22 ₁ and 22 ₂ and the stereo adapter 24.

7 includes an imaging optical system 26, an image fiber 27, a beam splitter 21, a pair of interference filters 22 ₁ and 22 _2, and a pair of photomultiplier tubes 28 ₁ and 28 ₂ . Have The luminance information of the flame F having _two different wavelengths λ ₁ and λ ₂ is guided to the pair of photomultiplier tubes 28 ₁ and 28 ₂ , and the light intensity can be obtained without using the high-speed video camera as described above. It will be understood that the measuring instrument 20 is configured.

  It should be noted that the present invention should be construed only from the matters described in the claims, and in the above-described embodiment, all the changes and modifications included in the concept of the present invention are other than those described. Is possible. That is, all matters in the above-described embodiment are not intended to limit the present invention, and include any configuration not directly related to the present invention. To get.

10 Combustion Analysis device 20 optical intensity measurement device 21 the beam splitter 22 _1, 22 ₂ interference filter 23 _1, 23 ₂ high speed monochrome video camera 24 Stereo adapter 25 _1, 25 ₂ reflector 26 imaging optical system 27 images the fiber 28 ₁ , 28 ₂ Photomultiplier tube 30 Analysis unit 31 Flame temperature calculation unit 32 KL value calculation unit 33 Soot generation / oxidation determination unit 34 Soot oxidation amount calculation unit 35 Soot generation amount calculation unit λ ₁ , λ ₂ wavelength F Flame S Swirl flow T _n , T _n-1 Flame temperature KL _n , KL _n-1 KL value

Claims (1)

A light intensity measuring device that detects light intensity of two different wavelengths at regular intervals with respect to the emitted light from the flame;
A flame temperature calculation unit for determining a flame temperature by comparing a ratio of the detected light intensities of the two wavelengths with a ratio of the light intensities of the same two wavelengths in the reference object;
A KL value calculating unit that calculates a KL value using the flame temperature obtained by the flame temperature calculating unit;
A soot generation / oxidation determination unit that determines whether the flame temperature calculated this time is lower than the flame temperature calculated last time, and at the same time, determines whether the KL value calculated this time is larger than the previously calculated KL value;
Based on the determination result in the soot generation / oxidation determination unit that the flame temperature obtained this time is higher than the flame temperature obtained last time and the KL value calculated this time is smaller than the KL value calculated last time, the previously calculated KL A soot oxidation amount calculating unit that calculates a decrease in the KL value calculated this time as the oxidation amount of soot;
Based on the determination result in the soot production / oxidation determination unit that the flame temperature calculated this time is lower than the flame temperature calculated last time and the KL value calculated this time is larger than the KL value calculated last time, the previously calculated KL A combustion analysis apparatus comprising: a soot generation amount calculation unit that calculates, as a soot generation amount, an increment of the KL value calculated this time with respect to a value.

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