JPH053882Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field This invention is a booster for compensating for the pressure loss of mixed gas when the piping distance from the gas mixer to the burner is long in a combustion circuit using a gas burner. It is related to circuits. In particular, the invention relates to a gas combustion circuit using a burner which is particularly suitable for mold making.

Conventional technology (1) In general, gas mixers are designed to keep the pressure loss to the burner low in order to stabilize the mixture of gas and air, and to minimize the flashback path between the gas mixer and the burner. Configure the circuit by shortening the distance.

(2) The gas mixer is equipped with a gas volume control valve and an air volume control valve, and the gas burner flame is controlled by the gas mixer.

Problems that the invention aims to solve (1) When it comes to large machines and equipment, it is necessary to centrally place the gas mixer in a place where it can be easily adjusted to improve operability. From the viewpoint of performance, it is not always easy to arrange the gas mixer near the burner. It is conceivable to automate the control valve and remotely control it electrically, but it is obvious that this would be expensive.

(2) Since the amount of combustion air required is large compared to the amount of combustion gas, if the number of burner holes (number of burner chips) changes, it is necessary not only to change the diameter of the gas mixer but also to change the size of the mixed gas piping and air piping. It was also necessary to change. (In many cases, there is a relatively large margin in the diameter of the gas pipe.) (3) The longer the distance between the gas mixer and the burner and the thicker the mixed gas pipe, the more the pressure loss in the pipe will be alleviated, but the responsiveness of the flame strength will be reduced. This is bad, and gas is wasted when extinguishing a fire.

(4) In combustion, it is generally easy to obtain sufficient margin for the gas supply amount by only slightly changing the pipe diameter, but the amount of combustion air, the pipe diameter, and the mixed gas pipe diameter need to be changed significantly. (5) If the pipe resistance (pressure loss) is large in mixed gas piping, if the gas pressure is higher than the air pressure, the air amount will fluctuate depending on the gas pressure and gas flow rate, and conversely, the air If the pressure is higher than the gas pressure, the gas amount will fluctuate (for example, if you increase the air flow rate, the gas will be pushed in and the flow rate will decrease, and if you increase the gas flow rate, the air flow rate will decrease), so stable combustion is maintained. I can't do it.

For this reason, strong combustion cannot be achieved,
There may be an insufficient amount of heat for the object to be heated, or furthermore, a reduction in flashback may occur due to the low internal pressure of the mixed gas in the burner section. Flashback phenomena are particularly likely to occur when the burner is mounted downward.

(6) The above problem often becomes an obstacle, especially when the pressure and type of gas to be supplied are changed after the fact.
In particular, mold manufacturing technology often employs a mechanism that heats the mold with a gas burner. That is, (7) The sand for the mold is coated with a thermosetting resin, and this sand is filled into the cavity of the heated mold.
When held for a certain period of time, the sand in the cavity hardens due to the heat of the mold, forming a mold.

In order to stabilize the curing conditions of the mold, the mold must be kept at a constant temperature at all times.

(8) In a mold making machine, the gas burner section is assembled into the device and moves up and down/transversely repeatedly.
Furthermore, the thermal power adjustment section (gas/air amount adjustment section) is often placed near the machine operator for ease of operation, and therefore the thermal power adjustment section and gas mixer are placed far away from the burner section. will be established.

(9) Particularly in the case of large molding machines, from the viewpoint of workability, the mixed gas piping between the gas mixer and the burner is long and has many bends, resulting in the following inconveniences.

a) Because the internal resistance of the mixed gas pipe increases, the flow rate of the mixed gas becomes insufficient and the firepower of the burner becomes weak.

b Due to the large internal resistance of the mixed gas piping, the internal pressure near the gas mixer outlet is high, and due to the relationship between the supply pressure of air and gas, when the amount of air is increased, the increased pressure will reduce the amount of gas, increasing the amount of gas. This makes it difficult to control the flame, as the amount of air decreases, and the flame may go out due to an inappropriate mixing ratio.

c. Due to the large resistance in the mixed gas piping, the pressure of the mixed gas becomes low near the burner due to pressure loss, resulting in weak flame strength and firepower, and flashback often occurs.

Particularly in the case of a burner that heats from top to bottom (Figure 7), the burner section tends to heat up, and even the slightest external shock can cause backfires frequently.

d. In order to reduce the internal resistance of mixed gas piping, it is necessary to avoid bent piping and to use large diameter piping, but this is not always possible from the viewpoints of machine structure/space and workability.

e Flashback is a phenomenon in which flame flows back into the gas burner and mixed gas piping, causing the mixed gas passage to heat up and abnormally increase pressure. This may lead to a risk of rupture of the pipes, which have poor heat resistance and pressure resistance.

f It is customary to install a valve body in the middle of the mixed gas piping to detect backfire (not shown), and the danger can be avoided by automatically shutting off the gas circuit. It is not practical if the circuit is interrupted.

(10) The type of gas and supply pressure may change after operation, and the number of burner chips often differs depending on the mold to which it is attached, even if the molding machine is the same, which may result in poor combustion. It was hot. Therefore, in such a case, it was necessary to change the entire gas mixer or a part of it.

FIG. 7 shows a conventional gas combustion circuit, in which weak combustion is performed by controlling the force of the flame 15 by the gas flow rate control valve 2 and the air flow rate control valve 7 so that the object to be heated (the mold 20) is kept warm. When the mold cools down due to an external factor (the cooling effect of the sand filled into the mold cavity), the gas cutoff valve 3 and automatic air cutoff valve 8 of the strong combustion circuit are switched to the temperature control electric circuit. The mold is twisted open and the flame is made stronger, raising the temperature of the mold to a predetermined temperature. The intensity of the strong combustion is adjusted in advance by the gas flow rate control valve 4 and the air flow rate control valve 9.

The temperature of the mold is stably maintained at a predetermined temperature by opening and closing automatic shutoff valves 3 and 8 in response to a command signal from a temperature regulating electric circuit.

Means for Solving the Problems The present inventors have solved the various deficiencies of the conventional gas combustion circuit as described above, especially by interposing a booster in the mixed gas piping of the gas combustion circuit for mold making. It was extremely successful,
The technical configuration of the present invention is as specified in the claims of the above-mentioned utility model registration, and will be explained in detail based on the attached drawings showing specific examples of the present invention.

FIG. 1 shows the above-mentioned gas combustion circuit as shown in FIG. 7, which alleviates the internal resistance in the mixed gas pipe 12 and compensates for the pressure drop in the burners 13, 14 and the mixed gas pipe 12' in the vicinity. This gas combustion circuit of the present invention is equipped with a booster circuit in order to eliminate the drawbacks of the above.

The booster circuit has a configuration in which a booster pilot air piping 18 connected to a booster pilot air source and having a booster pilot air flow rate control valve 17 is connected to a booster 19, and this booster 19 connects the gas mixer 11 and the burner. It is arranged in the mixed gas pipe 12 between the sections 13 and 14.

The flow rate of the booster pilot air is regulated by a control valve 17. The suction force of the booster 19 increases the flow rate of the mixed gas in the mixed gas pipe 12, and the pressure of the booster pilot air increases the internal pressure of the burner sections 13, 14 and the mixed gas pipe 12'. I can do it. Reference numeral 20 indicates a part of a mold for mold making.

2 and 3 show structural examples of the booster 19, in which the mixed gas in the mixed gas pipe 12 is sucked by the flow rate of pilot air (P, Air), and the mixed gas pipe 12' and the burner section 13, 1
It works to increase the internal pressure of 4. This type of booster has a structure that is generally known for air transportation of powder and granules, and although the essential principle is similar in some parts to a gas mixer, the purpose is different, so the same parts cannot be used. do not have. Also, the pilot air pressure must be greater than the mixed gas pressure.

Figures 4 to 6 show a structure generally known as a gas mixer. Figure 4 shows the mixer structure of a typical household gas appliance, which uses gas jetting force to suck in air and generate a mixed gas, and Figure 5 shows a system which mixes air and gas, each of which has its own pressure. .

Further, FIG. 6 shows a method in which secondary air is sucked in by pilot air and the increased amount is sent into the mixer as combustion air to be mixed with gas.

None of these gas mixers can compensate for the internal resistance of the mixed gas piping, and if the above problem occurs, a booster can be installed in the middle of the mixed gas piping for any of the gas mixers. It can be resolved.

Effects of the invention By adopting the configuration of the invention, the following main effects can be achieved: (1) By alleviating the pressure loss in the mixed gas piping with the booster circuit, even if the mixed gas piping is long, the mixing The ratio is stable, and a good combustion state can be maintained without reducing the amount of mixed gas.

(2) The booster circuit makes it possible to increase the internal pressure of the mixed gas in the burner section, thereby suppressing the flashback phenomenon and achieving powerful combustion.

(3) Even if the internal pressure, type, and number of burner holes (number of burner chips) of the supplied gas change, it can be handled simply by adjusting the booster air.

More specifically, the effects of the present invention are as follows: (1) Even if the mixed gas pipes 12, 12' are long, the pressure loss inside the pipes is alleviated, the amount of gas supplied increases, and both the fire strength and firepower are increased. was completed.

(2) As pressure loss has been reduced, the mixing ratio of gas and air has become more stable and easier to adjust.

(3) The internal pressure near the gas burners 12', 13, and 14 increased and no flashbacks occurred.

(4) The pilot air for booster 19 is also used as combustion air, so there is no wastage of air.

(5) Even if the type of gas (LNG, LPG, LBG, etc.), supply pressure, and air pressure change, or if the number of burner chips 14 increases or decreases, there is no need to replace parts, and the valve group in each circuit can be used. I was able to deal with this problem by simply adjusting the flow rate.

(6) The amount of air can be easily supplemented by the pilot air for booster 19.

[Brief explanation of the drawing]

Fig. 1 shows gas combustion according to the present invention, Figs. 2 and 3 are cross-sectional views showing examples of boosters that can be used in the present invention, Figs. 4 to 6 are cross-sectional views showing examples of gas mixers, and Figs. The figure shows an example of a conventional gas combustion circuit. In the diagram: 1...Gas main valve, 2...Gas flow control valve for weak combustion, 3...Gas automatic shutoff valve for strong combustion, 4...Gas flow control valve for strong combustion, 5...Gas circuit cutoff valve,
6... Main valve for air, 7... Air flow rate adjustment valve for weak combustion, 8... Air automatic cutoff valve for strong combustion, 9...
...Air flow rate control valve for strong combustion, 10...Air circuit cutoff valve, 11...Gas mixer, 12...Mixed gas piping, 12'...Mixed gas piping, 13...Gas manifold, 14...Burner chip, 15
... Flame, 16 ... Pilot air main valve for booster, 17 ... Pilot air flow control valve for booster, 18 ... Pilot air piping for booster, 19 ... Booster, 20 ... Casting mold.

Claims (1)

[Scope of utility model registration request] A booster 19 connected to a booster pilot air source and connected to a booster pilot air piping 18 having a booster pilot air flow control valve 17 is connected to a gas mixer 11.
A gas fuel circuit using a gas burner, characterized in that it is disposed in a mixed gas pipe 12 between the burners 13 and 14.