JP6199400B2 - Air-fuel ratio measurement system including optical sensor - Google Patents

Description

  The present invention relates to a measurement system, and more specifically, after detecting only an ultraviolet wavelength region generated in a process in which a fuel in a combustor is burned by a flame provided from the combustor, it is optimized through an analysis and calculation process. The present invention relates to an air-fuel ratio measurement system including an optical sensor that maintains an air-fuel ratio.

  In a general combustion system, the air-fuel ratio of the flame part is a parameter directly related to fuel consumption and energy efficiency, but it is very difficult to measure this. Most large combustion systems infer the air / fuel ratio of the flame by measuring the oxygen concentration at the exhaust end, and some engine premix combustors optically measure the light reflections from the chemiluminescence of the flame Thus, the air-fuel ratio may be determined.

For example, the method of installing a wavelength filter in front of an optical detector basically identifies the partial contribution of total light reflection from each species in a particular excited state such as OH, CH, C ₂ and CO _2. Used to do.

  This allows the signal ratio of one or more such chemical species to be associated with various combustor parameters, such as air-fuel ratio, heat rate, gas temperature, and conventional methods.

  That is, the measurement technique related to the above uses a simple optical sensor mechanism and camera device, and therefore, when the combustion flow is complicated in spatial resolution, the measurement is performed so as to have three-dimensional spatial resolution performance. There is a problem that it is difficult to optimize the system performance.

  Therefore, improving the control of the combustion process and optimizing the system performance as described above is very important in the field, and a measurement method inside the combustor for the optimization of the air-fuel ratio is required. It is the actual situation.

JP 2010-101615 A

  An object of the present invention to solve the above problems is to detect and analyze only the ultraviolet wavelength region generated in the process of burning the fuel in the combustor by the flame provided from the combustor. An air-fuel ratio measurement system including an optical sensor that maintains an optimized air-fuel ratio through a process is provided.

  Further, the object of the present invention is to accurately recognize the state of the combustion chamber by sensing only the wavelength region corresponding to 250 to 600 nm in the ultraviolet wavelength region and distinguishing the actual flame from noise. It is an object to provide an air-fuel ratio measurement system including an optical sensor that can be used.

  Another object of the present invention is to include an optical sensor that controls and controls the air control device to adjust the air amount for the optimized air-fuel ratio after analyzing and calculating based on the optical signal sensed by the optical sensor. It is to provide a fuel ratio measurement system.

  An air-fuel ratio measurement system including an optical sensor according to the present invention for solving the above-described problems includes a combustion chamber to which fuel is supplied; a combustor that provides a flame in communication with the combustion chamber; An optical sensor for generating an electrical signal after receiving an optical signal generated as it is burned by a flame; a fuel measuring sensor for measuring an amount of fuel supplied to the combustor; and electrically connected to the optical sensor An analysis module for converting an electrical signal into a convertible signal; and analyzing the conversion signal received from the analysis module and the fuel measurement signal received from the fuel measurement sensor to determine an air-fuel ratio and a thermal load. And an arithmetic module for calculating.

  Preferably, the optical sensor is a photodiode (Photodiode, PD) or a photomultiplier tube (PMT), and the optical signal is in an ultraviolet wavelength region of 250 to 600 nm.

  Preferably, the air-fuel ratio measurement system further includes an air control device that is connected to the calculation module and controls an amount of air supplied to the combustor.

  Preferably, the arithmetic module adjusts the air control device based on the calculated air-fuel ratio to maintain an optimized air-fuel ratio region by controlling the amount of air supplied to the combustor. It is characterized by that.

  Preferably, the arithmetic module controls the amount of air supplied from the air control device based on an analysis device that receives and analyzes the conversion signal and the fuel measurement signal; and data analyzed by the analysis device And a controller.

  In the present invention as described above, the air-fuel ratio optimized through the analysis and calculation process after detecting only the ultraviolet wavelength region generated in the process of burning the fuel inside the combustor by the flame provided from the combustor. Can be maintained.

  Further, the present invention accurately recognizes the state of the combustion chamber by sensing only the wavelength region corresponding to 250 to 600 nm in the ultraviolet wavelength region and distinguishing the actual flame from noise, so that it is visible. There is an effect that the influence of noise is less than when receiving the wavelength region of light rays or infrared rays.

  In addition, the present invention optimizes by controlling the air control device to adjust the air amount for the optimized air-fuel ratio after analyzing and calculating based on the optical signal sensed by the optical sensor. This has the effect of maintaining the air / fuel ratio.

FIG. 1 is a schematic diagram showing an air-fuel ratio measurement system including an optical sensor according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating the mechanism between the components of FIG. FIG. 3 is a graph of excess air ratio showing sensitivity according to the wavelength for selecting a specific wavelength (250 to 600 nm) region. FIG. 4 is a graph showing a change in logarithmic spectrum response according to the wavelength for air-fuel ratio measurement and calculation. FIG. 5A is a graph showing changes in the photodiode signal according to the oxygen concentration (O ₂ ) in the exhaust gas after combustion. FIG. 5B is a graph obtained by linearly fitting FIG. 5A. FIG. 6 is a graph showing the fuel amount (heat load) according to the pressure for the measurement and calculation of the air-fuel ratio. FIG. 7 is a graph showing a change in sensitivity of the photodiode in accordance with the temperature of the combustion chamber wall surface. FIG. 8A is a graph showing changes in the output signal (mV) of the photodiode according to the excess air ratio. FIG. 8 (b) is a graph obtained by linearly fitting FIG. 8 (a).

  The components constituting the air-fuel ratio measurement system including the optical sensor of the present invention may be used in an integrated form as necessary, or may be used separately. Depending on the usage pattern, some components may be omitted.

  A preferred embodiment of an air-fuel ratio measurement system 100 including an optical sensor according to the present invention will be described with reference to FIGS. In this process, the thickness of lines and the size of components shown in the drawings are exaggerated for the sake of clarity and convenience. Moreover, the term mentioned later is a term defined in consideration of the function in this invention, and this differs with the intention or practice of a user and an operator. Accordingly, definitions for these terms should be written based on the content throughout this specification.

  Hereinafter, an air-fuel ratio measurement system 100 including an optical sensor according to an embodiment of the present invention will be described with reference to FIGS.

  An air-fuel ratio measurement system 100 including an optical sensor according to an embodiment of the present invention includes a combustion chamber 110 to which fuel is supplied, a combustor 120 that provides a flame to the combustion chamber 110, and a fuel that is inserted into the combustion chamber 110 by the flame. After receiving the optical signal generated as it burns, the optical sensor 130 that generates an electrical signal, the fuel measurement sensor 140 that measures the amount of fuel supplied to the combustor 120, and the combustor 120 are arranged to face each other. An air control device 150 that controls the amount of air supplied to the combustor 120, an analysis module 160 that is electrically connected to the optical sensor 130 to convert the electrical signal into a conversion signal in an analyzable form, and the analysis module 160 And an arithmetic module 170 for calculating the air-fuel ratio and the thermal load by analyzing the conversion signal received from the fuel measurement signal received from the fuel measurement sensor 140.

  The combustion chamber 110 is a place where fuel is supplied and combusts, and has a hollow shape. Since the combustion chamber 110 corresponds to a known technique, a detailed description thereof will be omitted.

  Combustor 120 is arranged to communicate with combustion chamber 110. At this time, the intensity of the flame is adjustable, and the combustor 120 serves to provide a flame for burning the fuel inside the combustion chamber 110.

  As the optical sensor 130, either a photodiode (PD) 131 or a photomultiplier tube (PMT) 132 is applied.

  In the photodiode 131, when light touches the diode, electrons and holes that are positive charges are generated, current flows, and the magnitude of the voltage is substantially proportional to the light intensity. Thus, a phenomenon in which a voltage appears at a semiconductor junction as a result of the photoelectric effect is referred to as a photovoltaic effect.

  Such a photodiode 131 is characterized in that the response speed is fast, the sensitivity wavelength is wide, and the straightness of the photocurrent is good. It is mainly used for elements of electronic devices such as CD players, fire alarms, and remote control receivers for televisions, and is also used to accurately measure the intensity of light.

  The photomultiplier tube 132 is generally composed of a photocathode, a dynode, and an anode. A photocathode emits electrons when it receives light of a certain frequency or more due to a photoelectric effect. The electrons are amplified while passing through the dynodes, and the principle is that a current signal is generated that reaches the anode and can be read by external equipment. Since the signal is amplified immediately without passing through an external device, it is widely used for sensing very weak optical signals. Usually, the photoelectric effect occurs for frequencies above visible light, so it cannot be used for light below that frequency.

  A scintillator is a type of detector used to measure high-energy light, that is, X-rays or gamma rays using a photomultiplier, and is a concept different from a photomultiplier. However, when measuring X-rays or gamma rays, a scintillator is attached to a photomultiplier. As a result, the high energy photons react with the scintillator and change into photon flux in the visible light region, which is measured by the photomultiplier. This method of photon energy measurement is very widely used in particle physics experiments.

  The photodiode 131 and the photomultiplier tube 132 receive and apply only an optical signal in the ultraviolet wavelength region of 250 to 600 nm out of the wavelength of light due to the flame. The reason is that in the case of an optical signal with an infrared wavelength, the wall surface of the combustion chamber 110 may be heated, which is difficult to distinguish between the actual flame signal and ambient noise, which may cause a decrease in accuracy. Because it becomes.

  On the other hand, in the case of an optical signal having a wavelength corresponding to visible light, there is a risk of generating a lot of noise even with general natural light or other artificial light, so a signal similar to the optical signal provided from an actual flame is obtained. For this purpose, it is preferable to selectively receive and use only the ultraviolet wavelength region.

  That is, the photodiode 131 or the photomultiplier tube 132 according to the present invention senses only the optical signal corresponding to the ultraviolet wavelength region and minimizes the risk of noise, and thus senses the optical signal most similar to an actual flame. Is possible.

  The fuel measurement sensor 140 measures the amount of fuel supplied to the combustor 120. It goes without saying that the fuel measuring sensor 140 is not limited as long as it is a sensor capable of measuring a flow rate such as a pressure type or a thermal type.

  The air control device 150 is a device that controls the amount of air supplied to the combustor 120, and can adjust the amount of air supplied to the combustor 120 in the form of a valve or a gate.

  The analysis module 160 is electrically connected to the optical sensor 130 and serves to convert an electrical signal into a conversion signal in a form that can be analyzed. The analysis module 160 includes a signal converter and an amplifier. (Amplifier) may be used.

  In the present invention, both the converter and the amplifier can be used, or one of them can be used, but both the converter and the amplifier may be omitted if necessary.

  The arithmetic module 170 maintains the optimized air-fuel ratio region by adjusting the air control device 150 based on the calculated air-fuel ratio and controlling the amount of air supplied to the combustor 120. The calculation module 170 includes an analysis device (Analyzer) that receives and analyzes the conversion signal and the fuel measurement signal, and a controller (Controller) that controls the amount of air supplied from the air control device 150 based on the data analyzed by the analysis device. ) Can be included.

  Hereinafter, with reference to FIGS. 3 to 8, selection of a measurement wavelength region applied to the air-fuel ratio measurement system including the optical sensor of the present invention, measurement of the air-fuel ratio, calculation method, and photo for each wavelength according to temperature The measured signal value of the diode will be described.

  First, in the selection of the measurement wavelength region, 250 to 650 nm is the region where the main radicals (OH / CH / C2) generated from the flame emit light, and this specific wavelength point is not specified. The reason for designating as a range is as follows.

  First, as shown in FIG. 3, even if not only one wavelength value but also a certain range of wavelength values are integrated, a characteristic that is inversely proportional to the air-fuel ratio can be derived.

  Second, the economical photodiode sensors that can be used, such as most low-cost photodiodes, receive a signal over a specific range and represent the entire number as an electrical signal, so that one wavelength point. In order to select only, rather, more optical devices are needed that serve more filtering.

  Third, the wavelength region above 600nm is in the form of visible light, infrared light, etc., and the light generated by heating the combustion system wall or the tip of the combustor is visible light or infrared light. In addition, these signals may be transmitted to the sensors (PD, PMT) as noise.

  In relation to the above, as shown in FIG. 7, the measured value of each wavelength-specific photodiode signal according to the temperature is determined as a result of measuring the signal value using three photodiodes having different target center wavelengths. The graph shows the signal value of each photodiode measured in the process in which the temperature of the wall surface in the combustion furnace rises after the generation of.

  As shown in FIG. 7, the signal of the photodiode in the ultraviolet region (290 nm) is constant regardless of the temperature of the wall of the combustion furnace, but the signal of the photodiode in the other wavelength region (760 nm, 920 nm) It can be confirmed that the temperature varies depending on the temperature.

  This indicates that the light emitted from the wall corresponds to the wavelength range of 760 mm and 920 mm, and it is difficult to distinguish the intensity of the signal in the wavelength range of 760 mm and 920 mm generated purely from the flame.

  Eventually, when the wavelength regions of 760 mm and 920 mm are used, noise is generated due to the radiation effect radiated as the wall surface temperature rises.

  Fourth, in order to derive an equation for air-fuel ratio analysis at multiple thermal loads rather than at one thermal load, the slope of the “PD signal versus air-fuel ratio” relationship graph at each thermal load must be constant. However, there is a problem that it is difficult to ensure this at a wavelength of 250 to 650 nm or more.

  In this regard, FIG. 5 shows the relationship between the photodiode sensor signal and the air-fuel ratio.

  That is, the gradient of the amount of change according to the air-fuel ratio for each thermal load is similar, and even if linear fitting is performed with the same gradient, there is little error, and thus the air-fuel ratio can be obtained regardless of the thermal load. It is possible to derive the fuel ratio formula.

  On the other hand, (a) and (b) of FIG. 8 are the results of measurement using photodiode sensors whose main reaction wavelength regions are 650 to 700 nm and 900 nm to 1000 nm, respectively. The slope of “signal to air-fuel ratio” is different, and linear fitting with the same slope makes the error too large, and ultimately it becomes difficult to derive the air-fuel ratio equation.

On the other hand, the air-fuel ratio measurement and calculation method is as follows.
First, as a selection of the photodiode sensor to be used, it is preferable to select a photodiode that mainly responds to light in the wavelength region of 230 to 335 nm, as shown in FIG.

  Next, a signal for each fuel air-fuel ratio and heat load is measured as a database for sensor utilization.

  Next, since the gradient of “air-fuel ratio vs. signal value of photodiode” for each load is similar, linear fitting is performed with an average gradient.

  Next, using the pressure sensor of the fuel supply unit, the relationship between the pressure and the fuel amount (heat load) is measured by experiment, and the result is constructed as a database.

Then, by utilizing the database of FIGS. 5 (a) and (b), the following is derived fuel ratio type, such as [Equation 1], the exhaust gas O ₂ fuel ratio equation of the here It can be derived by a desired method and converted to an air-fuel ratio. In addition, the coefficient of the above equation may vary depending on the position of the sensor and the type of combustor.

[Formula 1]
Oxygen concentration in exhaust gas (O ₂ ) = 9.615384615 × photodiode signal × −7.9409435052E-3 × P ₂ -12.60726623

  Finally, using the above formula, the air-fuel ratio can be obtained if the numerical values of the ultraviolet sensor (here, the photodiode sensor is used) and the pressure sensor of the fuel line are known, and the fuel line is obtained in order to obtain a desired air-fuel ratio. Combustion control such as pressure adjustment is possible.

  The foregoing has been described with reference to the preferred embodiments of the present invention. However, those skilled in the art will not depart from the spirit and scope of the present invention as described in the following claims. It will be understood that various modifications and changes can be made within the scope of the present invention.

Claims (6)

A combustion chamber supplied with fuel;
A combustor in communication with the combustion chamber to provide a flame;
An optical sensor for generating an electrical signal after receiving only the ultraviolet wavelength region of the optical signal generated as the fuel is burned by the flame;
A fuel measurement sensor for measuring the amount of fuel supplied to the combustor;
An analysis module that is electrically connected to the optical sensor to convert the electrical signal into a conversion signal in a form that can be analyzed; and the conversion signal received from the analysis module and the fuel measurement received from the fuel measurement sensor An air-fuel ratio measurement system comprising: an arithmetic module that calculates an air-fuel ratio and a heat load by analyzing a signal and integrating a wavelength value in an ultraviolet wavelength region . The optical signal is in an ultraviolet wavelength region of 250 to 600 nm,
The air-fuel ratio measurement system according to claim 1. The air-fuel ratio measurement system further includes an air control device that is connected to the calculation module and controls the amount of air supplied to the combustor.
The air-fuel ratio measurement system according to claim 1. The arithmetic module adjusts the air control device based on the calculated air-fuel ratio to maintain an optimized air-fuel ratio region by controlling the amount of air supplied to the combustor. And
The air-fuel ratio measurement system according to claim 3. The arithmetic module is
An analysis device that receives and analyzes the conversion signal and the fuel measurement signal, and a controller that controls the amount of air supplied from the air control device based on data analyzed by the analysis device. ,
The air-fuel ratio measurement system according to claim 1. The light sensor is a photodiode (Photodiode, PD) or a photomultiplier tube (PMT),
The air-fuel ratio measurement system according to claim 1.

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