JPS63169422A - Combustion control - Google Patents

Abstract

PURPOSE:To maintain stable combustion condition by adjusting the supply amount of air or fuel in response to the output of a temp. detector installed near a combustion part. CONSTITUTION:A temp. detector 8 measures the temp. caused by radiation from a combustion part 1 and feeds a detected value to a temp. detecting part 10. The amount of fuel supplied by a fuel pump 3 is set in response to a load and an output corresponding to the amount of fuel is sent out to an input part 11 for the amount of combustion. In an operational comparator 12 temp. values when the amount of combustion and an air ratio mu are changed are previously stored and by the input of the amount of combustion from the part 11 and the temp. from the part 10 the air ratio mu is able to be found. When this air ratio is different from a set value mu, the revolving speed of a blower 4 is adjusted by increasing or decreasing it by an air controlling part 13. Consequently, satisfactory combustion condition can be maintained by keeping the air ratio constant (for instance mu=1.5).

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an air-fuel ratio control device for combustion equipment that uses fuel such as gas or oil.

Conventional technology When burning gas or oil as fuel, stable combustion can be maintained by supplying the fuel and air at an optimal ratio to prevent backfires, misfires, or incomplete combustion. This ratio of the amount of fuel and air is called the air-fuel ratio, and conventional methods have been devised to detect the combustion state and control the amount of fuel or air so as to always maintain an optimal air-fuel ratio.

An air-fuel ratio control system for oil-burning equipment is described, for example, in Japanese Patent Laid-Open No. 6.1-24917. This system detects the flame ion current of the flame with a flame rod inserted into the flame, and uses the fact that this ion current changes depending on the air-fuel ratio to adjust the driving frequency of the fuel supply pump to optimize the air-fuel ratio. It is. Third
The figure shows an example of the flame ion current value If. The horizontal axis is the primary air ratio μ, and here the air-fuel ratio will be explained in terms of the primary air ratio μ.

Typical burner input range (3000 to 1000ka
m+/h), the flame ion current value If is approximately μ=0
．． The distribution has a peak at 8-0.9.

Therefore, by adjusting the pump drive frequency, the flame ion current value I
By determining the fuel supply amount so that f becomes the maximum value, air-fuel ratio control is performed to maintain a stable combustion state.

Problems to be Solved by the Invention In the conventional example described above, a burner configured to maintain the most stable combustion state at μ=0.8 to 0.9 was used.
A burner configured to maintain the most stable combustion state near μ=1.5 (hereinafter referred to as a full-primary combustion burner)
There is also. Full combustion burners generally have low flame temperatures;
It is known that the burner configuration has a feature of extremely low levels of nitrogen oxides (NOx), which are harmful components in exhaust gas, and is highly effective for clean combustion.

However, the conventional air-fuel ratio control means as described above determines the fuel supply amount so that the flame ion current value 1f becomes the maximum value, so it is adjusted to μ = 0.8 to 0.9, and μ = 1
．． If a stable combustion state cannot be maintained near 5 and the input to the burner is small and the combustion amount is small, the If
The value was small and the amount of change was even smaller (it had the problem of being difficult to detect).

The present invention aims to solve such conventional problems, and aims to maintain a stable combustion state by adjusting μ to around 1.5 in a full-primary combustion burner.

A means to solve a problem.

In order to solve the above problems, the combustion control device of the present invention includes:
A fuel supplying means for supplying fuel and air, a mixing section connected to the fuel supplying means, a combustion section communicating with the pre-mixing section, and a temperature detection means provided near the combustion section; The combustion control is configured to increase or decrease the amount of air or fuel supplied by the means for supplying air or fuel in accordance with the output.

Effect of the Invention With the above-described configuration, the present invention allows the temperature detection means to measure the temperature due to radiation heat from the combustion section, which is determined by the air-fuel ratio. The air-fuel ratio can be arbitrarily set by increasing or decreasing the amount, and a stable combustion state is maintained at the air-fuel ratio near μ=1.5.

Embodiments Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. In the embodiment, an indoor open combustion hot air heater (fan heater) using an oil vaporization burner will be described as an example. FIG. 1 shows a system block diagram of the present invention. Reference numeral 1 denotes a full-primary combustion burner in which flame holes are formed with a wire mesh on the outside of a punched plate having a large number of small holes in the combustion section, and fuel is supplied from a fuel tank 2 by a fuel pump 3 and by a blower 4. Air is supplied to the vaporizer 5. The vaporizer 5 is maintained at a high temperature by a heater 6, and the supplied fuel is vaporized, mixed with air, and supplied to the combustion section 1 as a mixed gas, passing through the mixing section 7 and combusted in the combustion section 1. Reference numeral 8 denotes a temperature detection means for detecting temperature, which is composed of a thermocouple or a thermistor, has heat receiving fins 9 on the outer periphery, measures the temperature due to radiation heat from the combustion section 1, and outputs it to the temperature detection section 1.0. . The amount of fuel supplied by the fuel pump 3 is set according to the load, and an output corresponding to the supplied amount is output to the combustion amount input section 11.

Reference numeral 12 denotes an arithmetic comparison section, which compares a comparison value with a previously stored value according to the values input from the temperature detection section 10 and the combustion amount input section 11, and outputs the comparison value to the air amount control section 13. The air amount control section 13 controls the rotation speed of the blower 4 according to the input from the arithmetic comparison section 12 to increase or decrease the air amount.

FIG. 2 shows the temperature characteristics of the temperature detection section, that is, the mixing section 6 in the full combustion burner. The temperature decreases as U increases and as the amount of combustion increases.

Air supplied from the blast air 4 is heated in a vaporizer 5 whose temperature is controlled at a constant temperature, and then sent to the combustion section 1, which has a temperature of 1. The increase in air temperature within the vaporizer 5 is
It depends on the amount of air being sent and the shape of the vaporizer. In the case of the same carburetor, the effects of fuel evaporation and temperature changes in the air are small (determined only by the residence time and flow distribution of air in the vaporizer depending on the amount of air, and the temperature drop on the surface of the vaporizer. The larger the ratio μ and the larger the combustion amount, the larger the amount of air supplied (the lower the temperature 1 becomes).Then, the amount of air supplied from the flame to the temperature detection unit 8 increases rapidly as the air ratio decreases. The ejection speed of fuel gas from the flame hole is determined by its volume according to the increase and decrease of air and the change in combustion amount.The combustion speed is maximum when the air ratio is close to 1 and decreases as the air ratio increases.

This amount changes in correlation with the temperature of the opposing combustion section 1,
The temperature of the combustion section 1 is determined by heat received from the flame. The temperature of the flame decreases as the air ratio increases, and the distance between the flame and the combustion section 1 is determined by the balance between the combustion speed and the jetting speed. Therefore, when the air ratio decreases, the ejection speed decreases and the combustion speed increases (as a result, the flame approaches the combustion section 1,
temperature increases. Therefore, the temperature of the temperature detection section 8 increases. The temperature of the temperature detection section 8 is a value increased by the rise of the mixed gas in the vaporizer 5 and the radiation heat from the combustion section 1.

The arithmetic comparison unit 12 is stored in advance with temperature values when the combustion amount and the air ratio μ are changed. Combustion amount input section 11
By inputting the combustion amount and the temperature from the temperature detection section 8, the air ratio μ can be determined by comparing with the above values. Then, it is compared with the set value μ, and if it is different from the set value μ, the air control unit 13 adjusts the rotation speed of the blower 4 by increasing or decreasing it. Therefore, since the air ratio can be freely set to an optimum value, it can also be set in an all-legal range such as μ=1.5. In addition, flame ion current is affected by the oxygen concentration in the room and gases such as cigarettes, whereas the present invention, which measures the temperature rise of the supplied air, does not have the above effects because the temperature rise is correlated with the mass flow rate of the air. I never receive it. In this example, all
Although we have described the secondary combustion burner, μ can be similarly detected and controlled in the case of a partially premixed combustion burner.

In the above configuration, the blower 4 is adjusted so that the value corresponding to the set air ratio μ and combustion amount is the same as the value of the temperature detection unit 8, and the amount of air supplied is controlled. Good combustion conditions can be maintained by keeping the ratio constant (for example, μ=1.5). In this example, the oil fan heater was explained.
Similar effects can be obtained with combustion devices other than fan heaters or with gas combustion, and the same effect can be obtained even if a heater and means for detecting the heating temperature are provided in place of the vaporizer that maintains a constant temperature.

Effects of the Invention As described above, the combustion control device of the present invention provides the following effects.

(1) Since the air-fuel ratio can be automatically set to the optimal point, a stable combustion state can be maintained at all times without the need for manual adjustment.

(2) Since the air-fuel ratio can be set according to the amount of combustion, it can be varied with good combustion, and the range of variable combustion amount can be expanded, making it possible to control the amount of combustion according to the load.

(3) Since it can be adjusted with μ=1.4 to 1.8, NOx
It can be applied to combustion control in full combustion burners with low combustion.

(4) The room temperature,
Accurate air ratio control is possible without being affected by combustion conditions.

(5) Since the supply air means is controlled according to the temperature difference of the supply air, the response speed is fast, and even if the air filter is partially clogged due to dust or the like, even if the air ratio deviates, it can be adjusted instantly.

[Brief explanation of the drawing]

Fig. 1 is a control block diagram of a combustion control device according to an embodiment of the present invention, Fig. 2 is a characteristic diagram of the primary air ratio and the temperature of the first temperature detection section, and Fig. 3 is a diagram of a conventional air-fuel ratio control system. It is a characteristic diagram. 1... Combustion part, 3... Fuel pump, 4
．．・・・９． Blower, 5... Carburizer, 7...
...Mixing section, 8...Temperature detection means, 10...
... Temperature detection section, 11... Combustion amount input section,
12--Comparison calculation section, 13--.Air amount control section. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 1 Shallow Air Ratio (μ) Moe 3 Figure 1 Doctor! Kishihi)

Claims (1)

[Claims] comprising means for supplying fuel and air, a mixing section connected to the supply means, a combustion section communicating with the pre-mixing section, and a temperature detection means provided near the combustion section; A combustion control device that increases or decreases the supply amount of the means for supplying the fuel or the air accordingly.