JPH1194654A - Calorimetry for fuel gas, and air-fuel ratio control system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and inexpensively grasp calorific value of a fuel gas before preparing a gas miture, and to set the air-fuel ratio to a prescribed value before combustion, by inserting a light emitting material into the flame of fuel gas and by measuring a radiation energy quantity obtained by its light emission. SOLUTION: A mixed gas is prepared by operating regulating valves 2a, 2b for respective gases filled in a methane gas cylinder 1a and propane gas cylinder 1b while confirming respective flow rates by gas flow meters 3a, 3b to be supplied a burner 5 through a flow regulating valve 4. The flame of the fuel gas is injected from a mixed gas injection port 5c by an ignition device 6 to heat a light emitting material 7. Radiation energy of the resuling emission is converted into an electric signal by a light receiver 8, and its emission intensity is converted into a clorific value by a converter 9 to be stored by a recorder 10. A small temperature change of the flame by combustion is magnified as a large difference in the radiation energy to allow measurement of high resolution. An inexpensive small detector such as a photodiode is used for the detection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to thermal management of an industrial combustor, which significantly deteriorates control characteristics due to a change in calorific value of fuel gas, air-fuel ratio control of CNG and LPG vehicles, and control of fuel gas at the time of designing combustion equipment. It relates to calorimetry and the like.

[0002]

2. Description of the Related Art City gas (12A, 13A gas), LP gas, and the like, which are also used in the present invention and are used as fuel gas, have different calorific values depending on the gas used, and the required amount of air at the stoichiometric air-fuel ratio is different ( 1 and 2). For this reason,
In a combustion device using these gases as fuel, it is necessary to adjust the amount of fuel in accordance with changes in gas properties and gas temperature to keep the air-fuel ratio constant. In addition, since the LP gas is supplied with its properties changed in summer and winter, the same control is required.

Therefore, various calorimeters, such as a combustion method, a density method, and a thermal conductivity method, have been proposed and put into practical use as methods for measuring the calorific value of a fuel gas. There are disadvantages such as limited. Also,
There are also problems such as high accuracy with high price. In addition, any of these methods has a problem in that the external environment greatly affects the measurement, and the change is corrected by a complicated operation.

Further, in a combustion apparatus (engine or the like) which needs to maintain a constant air-fuel ratio (weight ratio of air to fuel), if the calorific value of fuel changes for some reason, for example, city gas is used as fuel. A natural gas engine that moves from 12A to 13A,
In the case of P gas fuel, the required amount of air differs depending on the calorific value, such as when the calorific value supplied between winter and summer differs. As a result, the initially set air-fuel ratio is shifted, and as a result, abnormal combustion occurs This may cause deterioration of components of the exhaust gas.

Therefore, it is necessary to detect a change in the calorific value of the fuel in advance and feed it back to the air-fuel ratio control. For that purpose, a simple and accurate calorimetric method capable of measuring the calorific value of the fuel under the operating state of the combustion device is required.

[0006]

However, the calorific value of the fuel gas can be obtained by measuring the temperature of the gas during combustion and converting the value. However, in the method of directly measuring the gas temperature, since accurate measurement is difficult due to fluctuations of the flame or the like, a large error may occur in the estimation of the calorific value. That is, in the conventional method of directly measuring the temperature of the fuel gas, the change in the temperature of the fuel gas due to the change in the calorific value of the fuel gas is small, the resolution is poor, and the temperature of the fuel gas changes due to the fluctuation of the flame. Problems such as difficulty in accurate temperature measurement have been pointed out. For the above reasons, some method for accurately measuring such a small temperature difference has been required.

[0007]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned conventional disadvantages, and includes a method of inserting a luminous material whose radiant energy varies according to a combustion temperature of a fuel gas into a flame of the fuel gas. Another object of the present invention is to provide a method for measuring the calorific value of the fuel gas by measuring the calorific value of the fuel gas by measuring the radiant energy amount obtained by the light emission of the luminescent material.

The present invention provides a method for measuring the calorific value of a fuel gas whose radiant energy is mainly selective radiation.

The present invention provides a method for measuring the calorific value of a fuel gas provided with a fuel gas flow control valve which varies the supply amount of the fuel gas according to the temperature of the fuel gas before combustion.

In the present invention, the fuel gas is a city gas 12A.
13A and LP gas (JIS K2240) Nos. 1 to 4 provide a method for measuring the calorific value of fuel gas.

The present invention also provides an air-fuel ratio control system using a method for measuring the calorific value of a fuel gas, wherein the mixer includes a fuel flow rate adjusting device for supplying the fuel gas and air to a combustor. It is an object of the present invention to provide an air-fuel ratio control system provided with air-fuel ratio control means for controlling the flow rate of gas based on the calorific value of the fuel gas which has already been measured.

The present invention provides an air-fuel ratio control system in which the combustor is an engine.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In general, the relation between the radiant energy generated from a black body and the temperature is Eb = δT ⁴ ,
By measuring the amount of radiant energy, temperature measurement with high resolution becomes possible. However, a detector for detecting the energy content of the whole spectrum of a black body is very expensive, and furthermore, it is necessary to improve the environment of the detector, so that it cannot be used easily.

For this reason, a method is employed in which a material that selectively emits a spectrum in the visible light range in a temperature range in which fuel gas is burned is placed in a combustion flame, the spectrum energy is measured, and the amount of heat is converted from the output of the detector into a calorific value. did. Further, the heat generation amount change flow control valve is provided near the gas injection port (supply port), and operates so as to decrease the gas flow rate when the heat generation amount is high and to increase the gas flow amount when the heat generation amount is low.

In the present invention, as a method of improving the resolution, the above-mentioned principle that the radiant energy changes with the fourth power of the temperature is used, the gas temperature is estimated from the radiant energy amount, and the calorific value of the fuel gas is measured based on the value. We propose a method to do this. However, since the radiation energy of the black body is unevenly distributed in the longer wavelength, it is necessary to measure the energy amount in a wide wavelength range in order to measure the radiation energy. Since the premixed flame of the gas is so transparent that a bright flame from free carbon cannot be expected, the measurement of radiant energy is also difficult in this case.

In view of the above-mentioned reasons, in the present invention, a luminous material which emits selective heat in a temperature range in which the fuel gas burns is inserted into the fuel gas flame, and the amount of radiant energy from the luminous material is measured. The principle of measuring the fuel gas temperature, that is, the calorific value of the fuel gas, has been found. Note that, as shown in FIG. 3, since the emission intensity becomes maximum when the equivalent ratio is around 1.2,
The basis for the experiment was set at an equivalence ratio of 1.2.

FIG. 4 shows a first embodiment of a combustion calorie measuring apparatus based on the principle of the present invention. The methane gas and propane gas packed in the methane gas cylinder 1a and the propane gas cylinder 1b are supplied to the gas flow meters 3a and 3b.
By operating the regulating valves 2a and 2b while checking the respective flow rates, a mixed gas is obtained, and the burner 5
To supply. The burner 5 has an air inlet 5a, a fuel gas outlet 5b, and a mixed gas outlet 5c, and the igniter 6 emits a fuel gas flame from the mixed gas outlet 5c to heat the luminescent material 7. .

As the light-emitting material 7, a material of a mantle (a woven fabric of cotton, ramie, human silk or the like impregnated with thorium nitrate or cerium nitrate) used in a gas lamp is used. That is, thorium oxide or cerium oxide in thorium nitrate or cerium nitrate selectively emits light in a flame and emits light with high luminance in a visible light range of about 0.45 to 0.65 μm. Therefore, any other luminescent material 7 in the present invention can be used as long as it has a high luminance in the visible light range. Then, the radiant energy by the light emission is converted into an electric signal by the light receiver 8,
Further, the luminous intensity is converted into a calorific value by the converter 9 and the recorder 1
Record at 0. The relationship between the light emission intensity and the calorific value is shown in FIG.
become that way.

As described above, a small change in the temperature of the flame due to combustion results in a large difference in the irradiation energy, so that high-resolution measurement can be performed. And a small detector can be used.

In order to compensate for the increase or decrease in the calorific value of the fuel gas used, a flow rate control valve 4 provided with a bimetal or the like which expands and contracts at the temperature of the gaseous fuel is provided in the fuel gas flow path system. When the gas temperature is low, the flow rate is reduced, and when the gas temperature is high, a large amount of fuel gas is made to flow.

That is, when the temperature of the supply gas and the air changes, that is, when both temperatures change and the temperature rises, the same amount of gas and air having a low density is supplied, and the mixing of air and fuel gas is performed. Although the ratio is constant, the amount of heat supplied per unit time decreases, and the luminance temperature decreases.

In the gas burner 5, air is drawn in from the air inlet 5a by gas ejection from the fuel gas outlet 5b, and primary mixing is performed. Therefore, if the gas flow rate is determined, the air amount is naturally determined. Note that the calorific value of the gas having different properties differs as the temperature increases, even if the gas has the same volume. That is, in order to secure the same amount of heat, the amount of gas must be increased by a reduced amount.

When the flow rate of air taken in by gases having different properties is constant and only the calorific value of the fuel gas is low, the amount of gas is insufficient and the mixture ratio shifts to the lean side. Optimal air
In order to maintain the mixing ratio of the fuel gas, the flow rate of the fuel gas must be increased by an amount corresponding to the decrease in the amount of heat. The amount of heat of the fuel gas changes depending on the property and temperature. This is because when the gas properties (calorific value) are different, the mixing ratio changes, and when the gas temperature increases, the gas density decreases and the calorific value decreases accordingly. Also, the lower the temperature, the higher the gas density,
The amount of heat per unit volume increases.

FIG. 6 shows an air-fuel ratio control system according to a second embodiment of the present invention. In this embodiment, the air-fuel ratio control system will be described using a combustor and an automobile engine as examples.

First, a conventional example of this embodiment will be described with reference to FIG. The fuel gas is mixed with the intake air through a mixer 12 via a fuel flow rate adjusting device 11 having a fixed flow rate, and further mixed with the fuel gas from a fuel flow rate fine adjusting device 13 to be sucked into a combustor or an engine 14. Burn. At this time 1
When 4 is a combustor, the temperature inside the combustor 14 is measured by a temperature sensor 15, while when 14 is an engine, the air-fuel ratio of exhaust gas is detected by an O ₂ sensor 16 and input to an air-fuel ratio determination circuit 17. Then, while controlling the fuel flow rate fine adjustment device 13, the exhaust gas is processed by the three-way catalyst 18 and exhausted. Although the air-fuel ratio of the combustor or the engine 14 has been controlled in this manner, the three-way catalyst 18 operates only when the air-fuel ratio is optimal. The fuel ratio could not be obtained.

Therefore, in this embodiment, the best air-fuel ratio is obtained by measuring the temperature of the fuel gas in advance using the calorimeter 19 and controlling the fuel flow rate adjusting device 11 'by the air-fuel ratio discriminating circuit 17'. Then, the three-way catalyst 18 is configured to function effectively.

As described above, the present invention has been described based on the embodiments described in the drawings. However, the present invention is not limited to the above-described embodiments, but may be implemented in any manner unless the structure described in the claims is changed. can do. For example, in the above embodiment, the light receiving element targets visible light, but the light intensity may be measured for near infrared light or the like.

[0028]

In summary, according to the present invention, the luminous energy of the luminescent material placed in the combustion flame of the fuel gas is measured, and the calorific value of the fuel gas is measured based on the luminous energy. Since the calorific value of the fuel gas can be known easily, compactly, and inexpensively before the mixture is produced, it is possible to set a predetermined air-fuel ratio before combustion.

Further, the present invention has the advantage that the measurement value can be obtained with high accuracy without being affected by the environmental temperature regardless of the measurement environment and the energy amount in the visible light range is measured. Detectors can be used. Further, since the fuel gas is directly applied to the luminescent material, the measurement time is short, and the consumption of the sample gas is small. Furthermore, since it can be made compact and lightweight, it has many features such as having a function as an auxiliary device of a fuel gas supply system. Therefore, it can be used as a sensor of an air-fuel ratio control device of any gas combustor.

In particular, in the case of a CNG vehicle, when the calorific value of the gas fuel changes, the air-fuel ratio during operation deviates from the stoichiometric air-fuel ratio, and thus deviates from the optimum condition of the three-way catalyst, and the exhaust gas value may deteriorate. According to the operation of the present invention, the operation can be performed while controlling the air-fuel ratio to the optimum value.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a relationship between a total heat generation amount of city gases 12A and 13A and a required air amount.

FIG. 2 is a characteristic diagram showing a relationship between a total heat generation amount of LP gas and a required air amount.

FIG. 3 is a characteristic diagram showing a relationship between an equivalent ratio and a light emission intensity.

FIG. 4 is a block diagram illustrating a configuration of a combustion-type calorimeter according to the first embodiment of the present invention.

FIG. 5 is a characteristic diagram showing a relationship between a calorific value and emission intensity.

FIG. 6 is a block diagram illustrating a configuration of an air-fuel ratio control system according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a conventional air-fuel ratio control system.

[Explanation of symbols]

1a, 1b Gas cylinder 2a, 2b Regulator 3a, 3b Gas flow meter 4 Temperature expansion / contraction regulator 5 Burner 5a Air intake 5b Gas injection 5c Gas flame 6 Ignition device 7 Mantle 8 Visible light receiver 9 Transducer 10 Recorder 11, 11 'fuel flow regulator unit 12 mixer 13 fuel flow fine adjustment device 14 combustor or the engine 15 temperature sensor 16 O ₂ sensors 17, 17' air discriminating circuit 18 the three-way catalyst 19 calorimeter

Continuing from the front page (72) Inventor Hirohide Furuya 1-2-2 Namiki, Tsukuba-shi, Ibaraki Industrial Technology Institute Machinery Research Institute (72) Inventor Akio Fujiwara 1-5-20 Kaigan, Minato-ku, Tokyo Tokyo Gas (72) Inventor Kanji Ohashi 1-5-20 Kaigan, Minato-ku, Tokyo Tokyo Gas Co., Ltd.

Claims (6)

[Claims] A luminous material whose radiant energy varies according to the combustion temperature of the fuel gas is inserted into a flame of the fuel gas, and the radiant energy obtained by the luminescence of the luminous material is measured to measure the amount of the radiant energy. A method for measuring the calorific value of a fuel gas, comprising measuring the calorific value of the gas. 2. The method according to claim 1, wherein the radiant energy is mainly selective radiation. 3. The method for measuring the calorific value of fuel gas according to claim 1, further comprising a fuel gas flow control valve that varies a supply amount of the fuel gas according to a temperature of the fuel gas before combustion. A method for measuring the calorific value of fuel gas. 4. The fuel gas is city gas 12A or 13A.
The method for measuring the calorific value of a fuel gas according to claim 1, wherein the fuel gas is LP gas (JIS K2240) No. 1 to No. 4. 5. An air-fuel ratio control system using the method for measuring calorific value of fuel gas according to claim 2, wherein the mixer includes a fuel flow rate adjusting device for supplying the fuel gas and air to a combustor. An air-fuel ratio control system comprising an air-fuel ratio control means for controlling a flow rate of the fuel gas based on the calorific value of the fuel gas already measured. 6. The air-fuel ratio control system according to claim 4, wherein said combustor is an engine.