JP2016217743A - Heat flux measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve measurement accuracy of a heat flux in a combustion chamber of an internal combustion engine.SOLUTION: A heat flux measuring device comprises: imaging means of imaging flames in a combustion chamber of an internal combustion engine; first calculating means of calculating flame moving speed information as information associated with a moving speed of the flames and flame temperature information as information associated with temperature of the flames based upon a flame image captured by the imaging means; pressure information acquiring means of acquiring pressure information associated with pressure in the combustion chamber; second calculating means of calculating predetermined parameters including a Prandtl number, kinematic viscosity and thermal conductivity of a combustion gas in the combustion chamber based upon the flame temperature information and pressure information, and also calculating heat transfer coefficient associated with heat transfer from the flames to an internal wall surface of the combustion chamber based upon the flame moving speed information and the predetermined parameters; and third calculating means of calculating a heat flux at a predetermined deep part in the wall surface of the combustion chamber according to a predetermined heat equation generated including the heat transfer coefficient.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an apparatus for measuring a heat flux in a combustion chamber of an internal combustion engine.

  For example, in order to grasp the strength of an object exposed to a harsh thermal environment such as a rocket or an aircraft, a temperature-sensitive paint is applied to the surface of the object and the heat flux distribution is measured there. However, since the heat flux distribution in the unsteady state where the thermal conditions fluctuate changes from moment to moment, the conventional method using thermosensitive paint does not have sufficient follow-up to the heat change, and the heat flux in the object There was a need for improved distribution measurement accuracy. Therefore, in the technique disclosed in Patent Document 1, excitation light is applied to an object surface made of an arbitrary material to which a temperature-sensitive paint is applied, and the emission intensity of the temperature-sensitive paint that changes in accordance with the object surface temperature is expressed by image information. Are acquired and detected in time series at a high rate. Based on the image information, a temperature distribution image of the material surface is obtained from the light intensity-temperature calibration characteristics, and the heat flux distribution is calculated based on the image. As a result, the heat flux distribution in the object can be measured even if the heat flux is an unsteady phenomenon or a short-time phenomenon.

JP 2004-212193 A

  An example of a severe thermal environment field is the inside of a combustion chamber of an internal combustion engine. In the combustion chamber, since the mixed gas of fuel and air is burned, the combustion chamber is placed in a high temperature and high pressure environment. Further, the combustion of the mixed gas does not occur constantly but occurs intermittently. Therefore, the wall surface of the combustion chamber is exposed to an unsteady thermal environment. Here, all of the combustion energy generated in the combustion chamber is ideally transmitted to the piston, so that it functions as a high-efficiency internal combustion engine. In other words, a loss of combustion energy occurs, and the efficiency of the internal combustion engine is reduced. Thus, from the viewpoint of improving the efficiency of the internal combustion engine, it is important to accurately grasp the thermal behavior in the combustion chamber, and one example is the use of heat flux in the combustion chamber.

  Here, in the above-described conventional technique, heat flux measurement using a temperature-sensitive paint is performed. However, since the mixed gas burns in the combustion chamber of the internal combustion engine and there is a flame, it is difficult to accurately obtain the image information of the emission intensity of the temperature-sensitive paint as shown in the prior art. In addition, when indirectly measuring the heat flux using the light emission of the temperature-sensitive paint, it is extremely difficult to avoid a decrease in measurement accuracy due to a shift in the followability of the temperature-sensitive paint to heat. . In particular, in an internal combustion engine, an unsteady thermal environment in which the combustion of a mixed gas is repeated in a combustion chamber for a very short time is formed. There is a limit.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a technique for improving the accuracy of measurement of heat flux in a combustion chamber of an internal combustion engine.

In the present invention, in order to solve the above-mentioned problems, attention was focused on the flame in the combustion chamber, that is, the flame formed by the combustion of the mixed gas, which determines the heat flux inside the wall surface of the combustion chamber of the internal combustion engine. Then, the flame is imaged, flame speed information and flame temperature information are calculated based on the image data, and the pressure information in the combustion chamber is used together with the flame information on the wall of the combustion chamber. By calculating the heat energy to be conducted according to a predetermined heat conduction equation, the heat flux inside the wall surface can be calculated.

  Specifically, the present invention is a heat flux measurement device, which is an imaging means for imaging a flame in a combustion chamber of an internal combustion engine, and information on the flame moving speed based on a flame image captured by the imaging means. First flame calculation information that calculates flame speed information, flame temperature information that is information relating to the temperature of the flame, pressure information acquisition means that obtains pressure information relating to pressure in the combustion chamber, flame temperature information, and Based on the pressure information, a predetermined parameter including the Prandtl number, kinematic viscosity coefficient, and thermal conductivity of the combustion gas in the combustion chamber is calculated, and the combustion from the flame is performed based on the flame moving speed information and the predetermined parameter. In accordance with a second calculation means for calculating a heat transfer coefficient related to heat transfer to the inner wall surface of the chamber, and a predetermined heat conduction equation formed including the heat transfer coefficient, And a third calculation means for calculating the heat flux at a given deep within the wall of the combustion chamber, the. According to this configuration, since the flame image data itself is used, it can be avoided that the acquisition of the image information of the emission intensity of the temperature-sensitive paint is inhibited by the flame as in the prior art.

  According to the present invention, it is possible to improve the measurement accuracy of the heat flux in the combustion chamber of the internal combustion engine.

It is a figure showing a schematic structure of a heat flux measuring device concerning the present invention. It is a flowchart regarding the measurement process for measuring the heat flux in the wall surface of the combustion chamber of an internal combustion engine performed in the heat flux measuring device shown in FIG. It is a figure which shows the image of the flame imaged in the measurement process shown in FIG. It is a figure which shows distribution of the moving speed of the flame calculated according to the PIV process in the measurement process shown in FIG. It is a figure which shows distribution of the temperature of the flame calculated according to the two-color method in the measurement process shown in FIG. It is the figure which described notionally the heat transfer from the flame in a combustion chamber to a wall surface inside. It is a figure which shows distribution of the heat flux in the wall surface of the combustion chamber measured by the heat flux measuring apparatus shown in FIG.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

  FIG. 1 is a diagram illustrating a schematic configuration of a heat flux measuring device according to the present embodiment. A fuel injection valve 1 shown in FIG. 1 is an injection valve for a diesel engine. In FIG. 1, the description of the overall configuration of the internal combustion engine on which the fuel injection valve 1 is mounted is omitted, and the fuel injected from the combustion container 2 and the fuel injection valve 1 forming the combustion chamber 9 is self-ignited. The wall surface 3 of the combustion chamber 9 is disposed at a position that is directly exposed to the flame 10 that is formed.

Further, a heat-resistant visualization window 4 is provided in a part of the combustion container 2 so that the inside of the combustion chamber 9 can be confirmed from the outside. By passing through the visualization window 4, it is possible to confirm the part of the flame 10 approaching the wall surface 3 from the outside. Therefore, a color (RGB) high-speed camera 6 is arranged so that the part is in the imaging field of view. Since the high-speed camera 6 is provided with a lens 7 having a shallow depth of field, spot-like imaging of the flame 10 immediately before reaching the wall surface 3 can be suitably performed. A pressure sensor 5 for detecting the pressure in the combustion chamber 9 is arranged in the combustion container 2.

  The heat flux measuring device shown in FIG. The analysis device 8 is a so-called computer and includes an arithmetic processing device, a memory, and the like. The high-speed camera 6 and the pressure sensor 5 are electrically connected to the analysis device 8, and image data captured by the high-speed camera 6 and pressure detection data from the pressure sensor 5 are stored in the analysis device 8. It is handed over and used for the process for heat flux measurement on the wall surface 3 described later.

  A process for measuring heat flux on the wall surface 3 will be described with reference to FIG. The heat flux measurement process is realized by the execution of a predetermined program by the arithmetic processing unit in the analysis device 8. The predetermined program is stored in a memory in the analysis device 8. First, in S101, fuel is injected from the fuel injection valve 1 in a state in which the conditions in which the fuel injected from the fuel injection valve 1 can perform self-ignition combustion is formed in the combustion chamber 9, and the flame 10 formed thereby. Is imaged by the high-speed camera 6. Since this heat flux measurement process measures the heat flux generated when the wall surface 3 receives heat from the flame 10, imaging of the flame 10 immediately before the flame 10 reaches the wall surface 3 is performed in S101. This imaging is performed a plurality of times over a period in which the behavior of the heat flux is grasped. FIG. 3A shows an example of the captured flame 10. The captured image data of the flame 10 is delivered to the analysis device 8. Further, in S <b> 101, the pressure sensor 5 detects the pressure in the combustion chamber 9 when the flame 10 is imaged. When the process of S101 ends, the process proceeds to S102.

  In S102, the moving speed information of the flame 10 is calculated by the PIV process based on the image data of the flame 10 captured a plurality of times. The process of S102 forms part of the process by the first calculation means according to the present invention. In the PIV processing, the distance Δx that the tracer particles used for visualizing the measured flow velocity moves in a minute time Δt is calculated by processing the image data, and the moving distance Δx is divided by Δt, thereby obtaining the flow velocity. This is an indirect calculation method. In the PIV process, two methods of image correlation method and particle tracking method can be exemplified as methods for calculating the movement distance Δx. In this embodiment, in order to calculate the moving speed information of the flame, the moving speed information is calculated according to the image correlation method using the luminance unevenness in the image data of the captured flame 10. Note that since the PIV process itself is a known image processing technique, a detailed description thereof will be omitted.

  Here, FIG. 3B shows an example of the distribution of the moving speed information of the flame 10 calculated based on the flame data shown in FIG. 3A. As can be understood from FIG. 3B, there are regions where the moving speed of the flame 10 is relatively high. When the process of S102 ends, the process proceeds to S103.

  In S103, the temperature information of the flame 10 is calculated by the two-color method based on the image data of the flame 10 captured multiple times. The process of S103 forms a part of the process by the 1st calculation means which concerns on this invention similarly to the process of S102. The two-color method is a conventional technique for measuring the flame temperature from a flame color image, and is disclosed in detail in, for example, Japanese Patent Application Laid-Open No. 01-180430, which is a patent document. In the two-color method, for example, an R signal and a G signal are extracted from the RGB information of the captured flame image data, and R / G which is the output ratio of both is obtained. Then, based on the theoretical curve of black body radiation using the temperature prepared in advance as a parameter, this is a method of calculating the flame temperature from the output ratio R / G. In this embodiment, the flame image data in the imaging range is divided into meshes, and the area average flame temperature for each mesh region is calculated by the two-color method.

  Here, FIG. 3C shows an example of the distribution of the temperature information of the flame 10 calculated based on the flame data shown in FIG. 3A. As can be understood from FIG. 3C, it can be understood that there is a portion (a region surrounded by a circle in the drawing) where the flame temperature is higher than the other regions in the imaging region. When the process of S103 ends, the process proceeds to S104.

  Next, in S104, the Prandtl number of the flame (combustion gas) in the combustion chamber 9 based on the temperature information of the flame 10 calculated in S103 and the pressure in the combustion chamber 9 detected by the pressure sensor 5 in S101. Predetermined parameters including Pr, kinematic viscosity ν, and thermal conductivity λ are calculated. The process of S104 forms part of the process by the second calculation means according to the present invention. These predetermined parameters are parameters necessary for calculation of heat transfer coefficient in S105, which will be described later, and in each process in S106 and S107, and are known to be physical property values that vary depending on the flame temperature and its pressure. . Therefore, a control map for calculating the Prandtl number Pr, the kinematic viscosity coefficient ν, and the thermal conductivity λ using the flame temperature and pressure as arguments is stored in the memory of the analysis device 8. Then, in the process of S104, by using the temperature information of the flame 10 calculated in S103 and the pressure detected in S101, the control map is accessed, whereby the Prandtl number Pr and the kinematic viscosity coefficient which are predetermined parameters are accessed. ν and thermal conductivity λ are calculated. When the process of S104 ends, the process proceeds to S105.

Ｐｒ：プラントル数
Ｖ：火炎の移動速度
Ｌ：代表寸法
ν：火炎の動粘性係数
λｇ：火炎の熱伝導率
複数回にわたって撮像された火炎の画像データに基づいて算出された火炎移動速度情報、火炎温度情報、及び圧力情報を利用することで、Ｓ１０５の処理により熱伝達率αの時系列データが算出されることになる。Ｓ１０５の処理が終了すると、Ｓ１０６へ進む。 In S105, the heat transfer coefficient α related to the heat transfer from the flame 10 to the wall surface 3 is calculated according to the following formula 1. The process of S105 forms a part of the process by the 2nd calculation means which concerns on this invention similarly to the process of S104. When diesel combustion is performed as in the present embodiment, it is generally considered that turbulent heat transfer occurs along the wall surface 3. Based on this point and the fact that the wall surface 3 is generally plate-shaped, Equation 1 is determined. A state in which the correlation between various parameters for calculating the surface temperature Ts of the wall surface 3 calculated in S106, the temperature Tw of the predetermined depth, and the heat flux q calculated in S107, including the heat transfer coefficient α, is modeled. Is shown in FIG. As shown in FIG. 4, the heat transfer coefficient α calculated by Equation 1 is the heat transfer coefficient when heat is transferred from the flame 10 whose temperature is Tg and the moving speed along the wall surface 3 is V to the wall surface 3. It corresponds to. And the surface temperature of the wall surface 3 is Ts, and the temperature of the predetermined deep part which is the position which advanced x from the surface inside is described as Tw. And the heat flux in this wall surface 3 is defined as q.

Pr: Prandtl number V: Flame movement speed L: Typical dimension ν: Flame kinematic viscosity coefficient λg: Flame thermal conductivity Flame movement speed information calculated based on flame image data taken multiple times, flame By using the temperature information and the pressure information, the time series data of the heat transfer coefficient α is calculated by the process of S105. When the process of S105 ends, the process proceeds to S106.

Ｔｇ：火炎温度
Ｔ_０：壁面３の初期温度
λｗ：壁面３の熱伝導率
ａｗ：壁面３の熱拡散率
erfc(x)：相補誤差関数
Ｓ１０６の処理が終了すると、Ｓ１０７へ進む。 In S106, the surface temperature Ts of the wall surface 3 and the temperature Tw of the predetermined depth are calculated according to the following formula 2. The processing of S106 forms part of the processing by the third calculation means according to the present invention. Since the flame by diesel combustion changes with time like a present Example, it is thought that the heat transfer from the said flame to the wall surface 3 is an unsteady thing. The primary heat conduction equation for calculating the temperature T of the wall surface 3 shown in the following equation 2 is determined in consideration of this point. In Equation 2, the surface temperature Ts may be set to x = 0, and the temperature Tw at the predetermined depth may be set to x = x.

Tg: flame temperature T ₀ : initial temperature λw of wall surface 3: thermal conductivity of wall surface 3 aw: thermal diffusivity of wall surface 3
erfc (x): Complementary error function When the process of S106 ends, the process proceeds to S107.

ρｗ：壁面３の密度
Ｃｗ：壁面３の比熱 In S107, the distribution of the heat flux at the depth x from the surface of the wall surface 3 is calculated in time series by substituting the surface temperature Ts calculated in S106 and the temperature Tw of the predetermined deep portion into the following Equation 3. The The process of S107 forms a part of the process by the 3rd calculation means which concerns on this invention similarly to the process of S106.

ρw: density of wall surface 3 Cw: specific heat of wall surface 3

  Here, FIG. 5 shows the distribution of the heat flux calculated according to Equation 3. As can be understood from FIG. 5, it can be understood that there is a portion in the imaging region that protrudes higher than the other region and has a higher heat flux. 3B, FIG. 3C, and FIG. 5 correspond to the flame image of FIG. 3A captured by the high-speed camera 6. For this reason, in this embodiment, it is possible to grasp the correlation between the heat flux, the moving speed of the flame, and the temperature of the flame on a plane (image plane). Therefore, based on the descriptions in FIGS. 3B, 3C, and 5, the locations corresponding to the locations where the heat flux is large (the locations surrounded by circles in FIG. 5) are shown in FIGS. 3B and 3C. Is also circled. As can be seen from these comparisons, it can be easily understood that the flame temperature is relatively high in the portion where the heat flux is large, although the flame moving speed is not so high. Here, the “heat flux” shown in FIG. 5 means the flow of heat escaping from the combustion chamber 9 to the wall surface 3, so to speak, it represents a loss in diesel combustion in an internal combustion engine (so-called cooling loss). . 3B, FIG. 3C, and FIG. 5, in order to reduce this loss, it is better to reduce the temperature than to suppress the moving speed of the flame 10 due to diesel combustion. It can be inferred that it is useful for reducing the heat flux at the location surrounded by the circles shown in FIG. After the process of S107, this control is terminated.

  According to this control, since the heat flux on the wall surface 3 is measured using imaged image data of the flame 10, the presence of the flame 10 does not get in the way as in the prior art, and the heat flux Measurement accuracy can be improved. Further, since the density and specific heat, which are the thermal property values of the wall surface 3, are used in measuring the heat flux, the measurement is not limited by the material of the wall surface 3.

DESCRIPTION OF SYMBOLS 1 ... Fuel injection valve 2 ... Combustion container 3 ... Wall surface 5 ... Pressure sensor 6 ... High speed camera 8 ... Analysis apparatus 9 ... Combustion chamber 10 ... Flame

Claims (1)

Imaging means for imaging a flame in a combustion chamber of an internal combustion engine;
First calculation means for calculating flame movement speed information, which is information relating to flame movement speed, and flame temperature information, which is information relating to the temperature of the flame, based on the flame image taken by the imaging means;
Pressure information acquisition means for acquiring pressure information relating to the pressure in the combustion chamber;
Based on the flame temperature information and the pressure information, a predetermined parameter including the Prandtl number, kinematic viscosity coefficient, and thermal conductivity of the combustion gas in the combustion chamber is calculated, and on the basis of the flame moving speed information and the predetermined parameter. A second calculating means for calculating a heat transfer coefficient related to heat transfer from the flame to the inner wall surface of the combustion chamber;
A third calculating means for calculating a heat flux at a predetermined depth in the wall surface of the combustion chamber according to a predetermined heat conduction equation formed including the heat transfer coefficient;
A heat flux measuring device comprising:

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