JPH05248630A - Forced draft type combustion apparatus - Google Patents

Abstract

PURPOSE:To provide a force draft type combustion apparatus having a blower with a bypass which enables lowering the noise level or cooling the fan motor during highly 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 to the burner 1, a blower 3 for supplying the burner 1 with air 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 air in the bypass is circulated through the inlet of the blower 3 or inside the casing of its motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustor using a forced air type burner 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.

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 device, since the bypass air is guided to the exhaust pipe or is supplied to the outer periphery of the combustion pipe, the noise level of the blower fan during high load combustion is reduced, Not enough attention was paid to the cooling of the fan motor. An object of the present invention is to provide a combustor having a blower fan with a bypass passage, which can reduce the noise level during high-load combustion or cool the fan motor.

[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 equipped with 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 bypass air is circulated to the intake port of the blower fan. Characterize. A compulsory blow type combustor according to a second aspect of the present invention is characterized in that bypass air is circulated in a casing of a blower fan motor.

[0006]

In the forced-blowing combustor according to the first aspect of the present invention, the bypass air is circulated through the intake port of the blower fan, so that the load of the fan during high-speed operation is small, and during high-load combustion. The increase in noise of the blower fan can be reduced. In the forced-blowing combustion device according to the second aspect, the fan motor can be prevented from being heated during high-speed operation, and the durability is improved.

[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 FIGS. This gas water heater 100 includes a vertically elongated flat box-shaped water heater case 101, a combustion cylinder 201 having a combustion chamber 200 inside, and an exhaust collecting cylinder 300 connected to the upper end of the combustion cylinder 201. And a forced-air-type total premixing (total primary air combustion) burner 1 mounted below the combustion cylinder 201. The burner 1 changes its combustion amount (heat generation amount) in accordance with the set hot water temperature, the supplied water amount, and the incoming water temperature, and has a hot water discharge capacity of No. 24 at the time of maximum load combustion and No. 2.4 at the time of minimum 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; In addition, the water heater 100 has a water supply pipe 61 connected to the water supply and a combustion chamber 200.
A hot water supply means 6 including a heat exchanger 63 and a hot water discharge pipe 64 installed at the upper part of the is installed.

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 comprises the housing 10
A fuel gas injection nozzle 21 disposed inside the main valve 2
2. A gas flow path 25 that connects the fuel gas source and the nozzle 21 via a safety valve 23 and a proportional solenoid valve 24. 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 41 of the bypass passage 4 is set at the center of the suction port 35 provided in the central portion of the casing 31, and the bypass air is ejected toward the suction port 35.

As a result, the blowing load of the blower fan 3 during high speed operation can be reduced, and the noise level of the fan during high load operation can be kept low. In this case, it is preferable that the tip of the bypass outlet 41 is set between the outer end and the inner end of the bell mouth 36 of the suction port 35 in order to reduce the noise level. Further, the bypass outlet 41 has a nozzle shape so as not to interfere with the intake air of the fan 3, and the noise prevention effect is improved when it is installed coaxially with the intake port.

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, and processes the input signals from the outlet hot water temperature setting means, 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 rotation 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 R between the amount of combustion air supplied to the burner 1 and the amount of air bypassed from the bypass passage 4 is set to 1: 0.6. The ratio R of the bypass air to the combustion air amount is 0.5 or more.
When set to 0 or less, the maximum load combustion (24
No.) blower fan 3 noise can be prevented from becoming too high. Further, the rotation speed of the blower fan 3 at the time of minimum load combustion (2.4) can be maintained relatively high.
The bypass ratio is set in advance to be an arbitrary ratio by measuring each flow rate by a test.

As a result, the air blown by the blower fan 3 has a high air pressure and can maintain a sufficiently large air volume, and the air-fuel ratio of the burner 1 is increased due to the clogging of the filter, the drop of the power supply voltage, the gust of wind, and other disturbances of the air-fuel ratio. It is possible to prevent a large deviation from the excess air ratio λ = 1.1. At least, there is a high probability that the stable combustion range of the premix burner is maintained in the range of λ = 1.1 to 1.6, and the combustion stability is improved.

3 and 4 show another embodiment. In this embodiment, the bypass passage 4 is connected to the motor 3 of the blower fan 3.
7 is connected to the casing 38 and the electrical component box 20
The bypass air is used to cool the motor 37 and the electronic control circuit in the electric component box 202.

As a result, it is possible to prevent the motor 37 from being heated during high-speed rotation, and prevent the electronic control circuit of the control device 5 from being exposed to high heat due to radiant heat during high-load combustion and degrading its function. As a result, the durability of electric and electronic devices is improved.

The cooling of the motor 37 or the electronic control circuit may be combined with the circulation of the bypass air to the suction port of the blower fan. (In this case, the motor casing 38 or the electrical component box 2 is provided in the middle of the bypass air circulation path.
02 can be incorporated to enhance these cooling effects).
It should be noted that in the above embodiment, the ratio of the bypass air to the combustion air amount is constant, but the bypass passage 4
An electrically-operated bypass valve may be provided at the branch position of (1) to change the ratio according to the combustion amount or the like. Further, in the above-mentioned embodiment, the compulsory air supply type combustor in which the blower fan 3 is provided on the upstream side of the total premixing burner 1 is shown, but the blower fan 3 is provided on the downstream side of the total premixing burner 1 by forced flow. It may be used for exhaust type combustion equipment. In this case, the cooling of the fan motor is not so effective, but the noise of the blower fan during high load combustion can be reduced. In the above embodiment,
Although the full premixed burner is shown as the burner, 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 schematic front sectional view of a water heater according to another embodiment.

FIG. 4 is a side sectional view of FIG.

[Explanation of symbols]

 1 Premix Burner (Burner) 2 Fuel Gas Supply Means 3 Blower Fan 4 Bypass Path 5 Control Device 24 Proportional Solenoid Valve 35 Intake Port 37 Motor 38 Casing 100 Gas Water Heater

Claims (2)

[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. A forced ventilation type combustion device having a bypass passage for bypassing a part of the air blown by a fan, characterized in that bypass air is circulated to the suction port of the ventilation fan. 2. 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 burn amount, and the blower. A forced-blowing combustor equipped with a bypass passage for bypassing a part of the air blown by the fan, characterized in that bypass air is circulated in the casing of the motor of the blowing fan.