JPH05248629A - Forced draft type combustion apparatus - Google Patents

Abstract

PURPOSE:To provide a forced draft type combustion apparatus having a blower with a bypass which ensures satisfactory combustion in the full range of combustion rate, enabling a decrease in the noise level during highly loaded combustion and improvement in stability of the combustion during lightly loaded combustion. CONSTITUTION:A forced draft type combustion apparatus is equipped with a burner 1 for combustion at varied rates, a solenoid proportional valve 24 for controlling the supply of fuel of the burner 1, a blower 3 for supplying the burner 1 with an in proportion to the rate of combustion, and a bypass duct 4 for bypassing part of the air from the blower 3. In this apparatus the ratio of the air passed into the bypass to the air used for the combustion is set in the range from 0.5 to 1.0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of combustibility of a combustion device using a burner of a forced air type whose combustion amount is variable.

[0002]

2. Description of the Related Art In recent years, combustion equipment is required to be compact in size in order to improve wearability, and it is also required to expand the range of increase / decrease in combustion amount (heat generation amount) in order to improve function. Therefore, the amount of combustion (combustion load) per unit volume is increasing, and a forced air blower burner that performs forced air supply or exhaust by a blower fan is adopted. Along with this, the ratio between the maximum load combustion amount and the minimum load combustion amount tends to be set to a large value of 10 times or more.

This forced air blower burner has a narrower range of stable air-fuel ratio than the conventional burner. Especially at low load combustion, the rotation speed of the blower fan is low,
Since the amount of blown air and the pressure of blown air are at low levels, fluctuations in the power supply voltage and the effects of gusts tend to cause combustion instability. In order to prevent such combustion instability, the rotation speed of the blower fan is kept high, and a bypass passage is provided in the blower passage to bypass excess air to improve the stability of combustion including low-load combustion. Various combustion devices have been proposed.

[0004]

In the conventional bypass type combustion equipment, since consideration has not been given to adopting the optimum bypass ratio in the combustion equipment that changes greatly from high load combustion to low load combustion, When the ratio of bypass air is high, the noise level of the blower fan greatly increases during high load combustion, and when the ratio of bypass air is low, it is difficult to sufficiently improve combustion stability during low load combustion. I understood. An object of the present invention is to have a blower fan with a bypass, and a burner in which the combustion amount changes in a wide range, a reduction in noise level during high load combustion and an improvement in combustion stability during low load combustion can be achieved, (EN) It is an object to provide a compulsory blow type combustion device that can obtain good combustion over the entire combustion range.

[0005]

A compulsory blower type combustion apparatus according to the present invention includes a burner having a variable combustion amount, a proportional solenoid valve for adjusting fuel supplied to the burner, and a combustion amount for the burner. In a forced ventilation type combustion device including a blower fan that supplies a corresponding amount of air and a bypass path that bypasses a part of the blown air by the blower fan, the ratio of bypass air to combustion air is 0.5 or more, It is characterized by being set to 1.0 or less.

[0006]

The inventors of the present invention set the ratio of the bypass air to the combustion air to 1.0 or less by the experiment and suppress the increase of the noise of the blower fan at the time of high load combustion to be relatively low. I found that I can do it.
Further, by setting the ratio to 0.5 or more, the rotation speed of the blower fan can be maintained in a highly stable range even at the time of low load combustion, and combustion against a disturbance factor of the air-fuel ratio such as fluctuation of power supply voltage or gust of wind. It turned out that the improvement of stability can be secured. Therefore, by setting the ratio of the bypass air to the combustion air to 0.5 or more and 1.0 or less, it is possible to reduce the noise level during high load combustion and improve the stability of combustion during low load combustion. Therefore, good combustion can be obtained over the entire combustion range.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A gas water heater 100, which is an embodiment of the forced air blowing type combustion apparatus of the present invention, will be described with reference to the drawings. This gas water heater 100 has a vertically long flat box-shaped water heater case 10.
Combustion cylinder 20 having a combustion chamber 200 inside
1 and an exhaust collecting cylinder 30 connected to the upper end of the combustion cylinder 201
0, and a forced air blowing type total premixing (all primary air combustion) burner 1 mounted on the lower portion of the combustion cylinder 201. The burner 1 changes its combustion amount (heat generation amount) according to the set hot water temperature, the feed water temperature, and the incoming water temperature.
No. 2.4 has a hot water discharge capacity of 2.4 at the lowest load combustion.

The gas water heater 100 has a fuel gas supply means 2
And a blower fan 3 for supplying combustion air to the burner 1.
A bypass passage 4 for bypassing a part of the air blown by the air blower fan 3; Further, the gas water heater 100 has a water supply pipe 61 connected to the water supply, a combustion chamber 2
Heat exchanger 63 and tap pipe 64 installed at the upper part of 00
The hot water supply means 6 is attached.

The premix burner 1 has a housing 10 having a premix chamber for premixing fuel gas and combustion air, a combustion plate 11 facing the combustion cylinder 201 and closing the upper surface of the housing 10, and the combustion. It has an ignition device 12 mounted on the upper surface of the plate 11, a frame rod 13 for detecting misfire, and a thermocouple 14 for air-fuel ratio control. The fuel gas supply means 2 connects the fuel gas injection nozzle 21 arranged in the housing 10 and the fuel gas source and the nozzle 21 via the main valve 22, the safety valve 23 and the proportional solenoid valve 24. And the flow path 25. The combustion plate 11 is formed by forming a large number of small flame openings in a ceramic plate, and the nozzle 21 is formed by arranging a large number of fuel gas injection holes in a metal pipe.

The blower fan 3 is a scroll casing 3
1, a centrifugal fan 32 is arranged, and a fan rotation speed sensor 33 is attached. The blower fan 3 is provided in the communication passage 34 between the outlet of the casing 31 and the housing 10.
The bypass passage 4 is provided to bypass a part of the blown air. The outlet of the bypass passage 4 is connected to the blower fan 3 and the electrical component box 202 to cool the motor of the blower fan 3 and the control device 5.

The flow rate of the fuel gas is controlled by the proportional solenoid valve 24, and the fuel gas blown out from the nozzle 21 has excess air and combustion air in the housing 10 (of the blown air forced by the blower fan 3 that is not bypassed). Rate λ = 1.1
Premixed with the degree as a target value, supplied from the combustion plate 11 into the combustion cylinder 201 and ignited by the ignition device 12, all primary combustion is performed in the combustion chamber 200 to heat water flowing through the heat exchanger 63, and exhaust The air is exhausted from the collecting cylinder 300.

The control device 5 is installed in the electrical equipment box 202 installed in the case 101, processes input signals from the means for setting the hot water temperature, the water amount sensor 62, and the incoming water temperature sensor (not shown). , The combustion amount is determined based on the control data obtained in advance by measurement or calculation, the blower fan 3 is controlled, and the rotation speed sensor 33 is used by the blower fan 3
Is detected, and a predetermined current is supplied to the proportional solenoid valve 24 based on this rotation speed.

Further, during combustion, the thermocouple 14 detects the air-fuel ratio to correct the rotational speed of the blower fan 3, and the flame rod 13 detects misfire. When this occurs, the safety valve 23 is closed to burn. Stop.

In this embodiment, the bypass ratio between the combustion air amount supplied to the burner 1 and the air amount bypassed from the bypass passage 4 is set to 1: 0.6 in advance by a test or the like. The ratio R of the bypass air to the combustion air amount needs to be set to 0.5 or more and 1.0 or less. By setting the ratio R to 1.0 or less, it is possible to prevent the noise of the blower fan 3 at the time of maximum load combustion (No. 24) from becoming too high (see FIG. 3). Further, by setting the ratio R to 0.5 or more, the rotational speed of the blower fan 3 at the time of minimum load combustion (No. 2.4) can be maintained relatively high (see FIG. 4). As a result, blower fan 3
Due to the high air pressure, the air volume can be maintained relatively large, and the air-fuel ratio of the burner 1 is excessive by the air ratio λ due to filter clogging, power supply voltage drop, gusts, and other causes of air-fuel ratio disturbance.
It is possible to prevent a large deviation from = 1.1. At least the stable combustion range of the premix burner λ = 1.1 to 1.
The probability of being kept in the range of 6 is large, and combustion stability is improved.

Although the blower fan 3 is provided on the upstream side of the total premixing burner 1 in the above embodiment, the compulsory air supply type combustion device is shown. However, the blower fan 3 is provided on the downstream side of the total premixing burner 1. It may be used in a provided forced exhaust combustion device. Further, although the premixed burner is used as the burner in the above embodiment, a Bunsen type burner may be used.

[Brief description of drawings]

FIG. 1 is a schematic front sectional view of a water heater according to an embodiment of the present invention.

FIG. 2 is a side sectional view of FIG.

FIG. 3 is a graph showing the relationship between noise and the ratio R of bypass air to the amount of combustion air.

FIG. 4 is a graph showing the relationship between burner combustion load and fan rotation speed.

[Explanation of symbols]

 1 Premix Burner (Burner) 2 Fuel Gas Supplying Means 3 Blower Fan 4 Bypass Path 5 Control Device 24 Proportional Solenoid Valve 100 Gas Water Heater

Claims (1)

[Claims] 1. A burner whose combustion amount is variable, a proportional solenoid valve which adjusts fuel supplied to the burner, a blower fan which supplies the burner with an amount of air corresponding to the combustion amount, and the blower. In a forced ventilation type combustion device having a bypass passage for bypassing a part of the air blown by a fan, the ratio of bypass air to combustion air is 0.5 or more,
A forced air blowing type combustion device characterized by being set to 1.0 or less.