Fuel gas ignition gun and premixing flame stabilizing structure thereof

By adopting a premixed flame stabilization structure in the gas ignition gun, including a mixing disk, a flame stabilization disk, a front-delay gas pipe and a combustion-assisted secondary air duct, the existing gas ignition gun is solved incomplete functions and flame instability in a narrow space, and the stable establishment and continuous combustion of the flame are achieved.

CN222560069UActive Publication Date: 2025-03-04ANDERSON THERMAL SOLUTION SUZHOU CO LTD
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Patent Information

Application Number
CN202421900749.7
Authority / Receiving Office
CN · China
Patent Type
Utility models(China)
Current Assignee / Owner
Filing Date
2024-08-07
Publication Date
2025-03-04
Estimated Expiration
2034-08-07

AI Technical Summary

Technical Problem

When existing gas ignition guns are installed in a small space, they usually need to omit the fire viewing mirror or flame monitoring unit, resulting in incomplete functions and difficulty in stably establishing the flame.

Method used

A premixed flame stabilization structure of a gas ignition gun is adopted, including a mixing disk, a flame stabilizing disk, a front-delay gas pipe and a combustion-assisted air secondary air duct. Through the design of these components, a ignition-induced mixing space and a flame stabilizing space are formed to improve the stability of the flame.

Benefits of technology

It realizes the stable establishment of flames in a narrow space, ensuring the continuous combustion of flames, not easy to defire and extinguish, and provides complete functions, including flame monitoring and stable combustion.

✦ Generated by Eureka AI based on patent content.

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Abstract

The utility model provides a fuel gas ignition gun and a premixing flame stabilizing structure thereof. The premixing flame stabilizing structure comprises a mixing disc, a flame stabilizing disc, a front extending gas pipe and a combustion-supporting air secondary air pipe. An ignition mixing space is formed between the mixing disc and the flame stabilizing disc, a part of air and a part of fuel gas are changed into mixed gas after passing through the mixing disc, and ignition is formed by spark ignition generated by a spark plug after speed reduction and flow stabilization of the flame stabilizing disc; and the other part of air is continuously conveyed forwards through the combustion-supporting air secondary air pipe, and the other part of fuel gas is conveyed forwards through the forward extending fuel gas pipe and is mixed at the foremost end of the ignition gun to form main fire. The ignition stability can be improved through pre-mixing in the ignition mixing space, the opening of the flame stabilizing disc is larger than that of the mixing disc, the flow speed of mixed gas is reduced, and therefore it is guaranteed that flames of the gas ignition gun can be stably combusted, and blow-off and extinguishment are avoided.
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Description

Technical Field

[0001] The utility model relates to the technical field of gas ignition guns, in particular to a gas ignition gun and a premixed flame stabilizing structure thereof. Background Art

[0002] The burner ignition gun is a key device for starting and maintaining the combustion process during the operation of the burner. The space for installing the ignition gun on a general burner is relatively small. Since the air-fuel ratio of a gas ignition gun is usually around 10:1, in order to keep the ignition gun small, the gas is introduced from the center tube of the ignition gun. The center tube diameter is generally 0.5 inches. The air is introduced between the outer tube and the center tube, mixed at the nozzle, and ignited by the spark plug to produce a flame. The ignition gun of this structure is limited by the small space, and either the fire viewing mirror or the flame monitoring unit is omitted. Such an ignition gun obviously does not have complete functions, so it is necessary to propose a gas ignition gun with a compact structure and full functions. At the same time, the ability to stably establish a flame should also be a basic performance. Utility Model Content

[0003] In order to overcome the above-mentioned deficiencies of the prior art, the purpose of the utility model is to provide a gas ignition gun and a premixed flame stabilizing structure thereof.

[0004] In order to achieve the above-mentioned purpose, the technical solution adopted by the utility model to solve its technical problems is: a premixed flame stabilizing structure of a gas ignition gun, comprising a mixing disk, a flame stabilizing disk, a forward gas pipe and a secondary air pipe for combustion-supporting air, the outer circumference of the mixing disk and the outer circumference of the flame stabilizing disk are both in contact with the inner wall of the front end of the outer tube of the gas ignition gun, the flame stabilizing disk is located at the axial front end of the mixing disk, the rear end of the forward gas pipe is connected to the mixing disk and communicated with the inner cavity of the outer tube, the forward gas pipe runs through the flame stabilizing disk and extends to the front of the flame stabilizing disk, the rear end of the secondary air pipe for combustion-supporting air is connected to the mixing disk and communicates with the inner cavity of the outer tube, the forward gas pipe runs through the flame stabilizing disk and extends to the front of the flame stabilizing disk, and the rear end of the secondary air pipe for combustion-supporting air is connected to the mixing disk and communicates with the inner cavity of the outer tube. The end is connected to the mixing disk and is coaxially connected with the air delivery pipe in the outer tube of the gas ignition gun, the secondary air duct of the combustion-supporting air passes through the flame-stabilizing disk and extends to the front of the flame-stabilizing disk, the mixing disk is provided with an ignition gas hole that passes through from front to back, the rear end of the ignition gas hole is connected to the inner cavity of the outer tube, the mixing disk is also provided with an oblique through hole for combustion-supporting air, the rear end of the oblique through hole for combustion-supporting air is connected to the air delivery pipe, the flame-stabilizing disk is provided with a flame-stabilizing hole that passes through from front to back, the opening area of ​​the flame-stabilizing hole is larger than the sum of the opening areas of the ignition gas hole and the oblique through hole for combustion-supporting air on the mixing disk.

[0005] By adopting the technical solution of the utility model, an ignition mixing space is formed between the mixing disk and the flame stabilizing disk. A part of the air and a part of the gas become a mixed gas after passing through the mixing disk. After being decelerated and stabilized by the flame stabilizing disk, they encounter the spark generated by the spark plug to ignite and form the ignition; the other part of the air continues to be transported forward through the secondary air duct of the combustion-supporting air, and the other part of the gas is transported forward through the front extended gas pipe, and mixed at the front end of the ignition gun to form the main fire. Premixing in the ignition mixing space can improve the stability of the ignition establishment. The opening of the flame stabilizing disk is larger than that of the mixing disk, and the flow rate of the mixed gas is slowed down, which ensures that the flame can burn stably and will not be extinguished.

[0006] Furthermore, the front end face of the mixing disk is provided with an eccentrically arranged outwardly convex cone portion, the axis of the cone portion is coaxial with the secondary air duct of the combustion-supporting air, and the number of the combustion-supporting air oblique through holes is multiple, and the combustion-supporting air oblique through holes penetrate the cone portion obliquely at an angle to the axis of the cone portion.

[0007] By adopting the above preferred solution, the oblique air flow flowing out from the combustion-supporting air oblique holes and the parallel gas flow flowing out from the ignition gas holes are staggered and mixed, thereby improving the mixing uniformity.

[0008] Furthermore, a plurality of premixed air holes distributed along the axial direction are provided on the air delivery pipe behind the mixing disk.

[0009] By adopting the above preferred solution, premixing is performed in advance to improve the uniformity of premixing.

[0010] Furthermore, the front end of the front-extended gas pipe is in front of the front end of the combustion-supporting air secondary air duct.

[0011] By adopting the above preferred scheme, the gas in the front extended gas pipe and the air in the secondary air duct of the combustion-supporting air are finally mixed. Due to the existence of a relatively stable pilot fire, these two parts of gas burn again to become the main fire. Since the pilot fire is stable, the main fire is also relatively stable.

[0012] Furthermore, a pressure relief hole is opened on the outer pipe located in front of the front extended gas pipe.

[0013] The above preferred solution can prevent flameout caused by too high air pressure causing too fast mixed flow rate. The pressure relief hole can relieve part of the pressure, and the mixed flow rate is reduced to within the flame propagation speed, thereby ensuring the stable existence of the flame.

[0014] A gas ignition gun comprises an outer tube and an air delivery tube, wherein the air delivery tube is located inside the outer tube, and a gas channel is formed between the outer tube and the air delivery tube; the premixing flame stabilizing structure of the gas ignition gun is arranged at the front end of the outer tube.

[0015] Furthermore, in the cross section, the air delivery pipe is eccentrically arranged with respect to the outer pipe.

[0016] Furthermore, it also includes a gun base unit installed at the rear end of the outer tube, the gun base unit is provided with a gas inlet and a gas pressure monitoring port, the rear end of the air delivery pipe runs through the gun base unit, a flame monitoring device is installed at the tail end of the air delivery pipe, the tail end of the air delivery pipe is also connected to the air inlet and the air pressure monitoring port via a bypass, a spark plug and a fire viewing mirror are also installed on the gun base unit, and the spark plug is extended forward through the space between the outer tube and the air delivery pipe.

[0017] The above preferred solution is adopted, which is contrary to the conventional gas circuit design idea of ​​the ignition gun. The air is input from the middle, and the gas is transported in the air delivery pipe. The flame monitoring device at the rear end of the ignition gun obtains a better flame signal through the air delivery pipe with a relatively large cross-sectional area in the middle, thereby realizing reliable detection of the flame. The air delivery pipe is eccentrically arranged in the outer tube, providing sufficient space for the installation of the spark plug in a compact structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 The utility model is a structural schematic diagram of a gas ignition gun.

[0020] Figure 2 The utility model is a structural schematic diagram of a gas ignition gun with a hidden outer tube and a gun base body.

[0021] Figure 3 It is a sectional view of a gas ignition gun of the utility model.

[0022] Figure 4 yes Figure 1 A partial enlarged view of point A in the middle.

[0023] Figure 5 yes Figure 2 A partial enlarged view of point B in the middle.

[0024] Figure 6 yes Figure 2 A partial enlarged view of point C in the middle.

[0025] Figure 7 yes Figure 3 A partial enlarged view of point D in the middle.

[0026] Figure 8 yes Figure 3 A partial enlarged view of point E in the middle.

[0027] Fig. 9 yes Figure 3 A partial enlarged view of point F in the middle.

[0028] Fig.10 It is a schematic diagram of the structure of the rear end face of the hybrid disk.

[0029] Fig.11 It is a structural schematic diagram of the front end surface of the mixing disk.

[0030] Fig.12 It is a cross-sectional view showing the location of the cone portion of the mixing disk.

[0031] The numbers and letters in the figure represent the names of the corresponding parts:

[0032] 10-gun base unit; 11-gun base body; 111-gas inlet; 112-gas pressure monitoring; 12-front cover; 13-rear cover; 20-outer tube; 21-pressure relief hole; 30-air delivery pipe; 31-air delivery joint; 32-air inlet; 33-air pressure monitoring port; 34-premixed air hole; 40-spark plug; 41-oblique bending section; 42-8-shaped fixing card; 43-ceramic sleeve; 51-flame monitoring device; 52-fire viewing mirror; 61-mixing disk; 611-ignition gas hole; 612-combustion air oblique through hole; 613-first connecting port; 614-second connecting port; 615-third connecting port; 616-spark plug through hole; 617-cone; 62-flame stabilizing disk; 621-flame stabilizing hole; 63-forward gas pipe; 64-combustion air secondary air duct. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0034] In order to facilitate the description of technical features, the directional descriptions of "front" and "rear" in the present invention are based on the direction in which the flame of the ignition gun is ejected as the front.

[0035] like Figure 1-12As shown, in one embodiment of the present invention, a premixing flame stabilizing structure of a gas ignition gun, the premixing flame stabilizing structure includes a mixing disk 61, a flame stabilizing disk 62, a forward gas pipe 63 and a combustion-supporting air secondary air pipe 64, the outer circumference of the mixing disk 61 and the outer circumference of the flame stabilizing disk 62 are both in contact with the inner wall of the outer tube 20, the flame stabilizing disk 62 is located at the axial front end of the mixing disk 61, the rear end of the forward gas pipe 63 is connected to the mixing disk 61 and is communicated with the inner cavity of the outer tube 20, the forward gas pipe 63 runs through the flame stabilizing disk 62 and extends to the front of the flame stabilizing disk 62, the rear end of the combustion-supporting air secondary air pipe 64 is connected to the mixing disk 61 is connected and coaxially connected with the air delivery pipe 30, the secondary air duct 64 for combustion-supporting air passes through the flame-stabilizing disk 62 and extends to the front of the flame-stabilizing disk 62, the mixing disk 61 is provided with an ignition gas hole 611 which passes through from front to back, the rear end of the ignition gas hole 611 is connected with the inner cavity of the outer tube 20, the mixing disk 61 is also provided with an oblique combustion-supporting air through hole 612, the rear end of the oblique combustion-supporting air through hole 612 is connected with the air delivery pipe 30, the flame-stabilizing disk 62 is provided with a flame-stabilizing hole 621 which passes through from front to back, the opening area of ​​the flame-stabilizing hole 621 is larger than the sum of the opening areas of the ignition gas hole 611 and the oblique combustion-supporting air through hole 612 on the mixing disk. The beneficial effect of adopting the above technical solution is: an ignition mixing space is formed between the mixing disk and the flame stabilizing disk, and a part of the air and a part of the gas become a mixed gas after passing through the mixing disk, and after being decelerated and stabilized by the flame stabilizing disk, they encounter the spark generated by the spark plug to ignite and form the ignition; the other part of the air continues to be transported forward through the secondary air duct of the combustion-supporting air, and the other part of the gas is transported forward through the front extension gas pipe, and mixed at the front end of the ignition gun to become the main fire. Premixing in the ignition mixing space can improve the stability of the ignition establishment. The opening of the flame stabilizing disk is larger than that of the mixing disk, and the flow rate of the mixed gas is slowed down to ensure that it is below 4m / s. Because the upper limit of the flame propagation speed is 4m / s, this ensures that the flame can burn stably and will not be extinguished.

[0036] like Figure 1-9As shown, an embodiment of the utility model is: a gas ignition gun, including a gun base unit 10, an outer tube 20, an air delivery pipe 30, a spark plug 40, a flame monitoring device 51 and a fire viewing mirror 52, the gun base unit 10 includes a gun base body 11, a front cover plate 12 installed on the front side of the gun base body and a rear cover plate 13 installed on the rear side of the gun base body; a gas channel is between the outer tube 20 and the air delivery pipe 30; a gas inlet 111 and a gas pressure monitoring port 112 are provided on the gun base body 11, and the gas inlet 111 and the gas pressure monitoring port 112 are connected to the gas channel in the outer tube 20 through the inner cavity of the gun base body 11; the rear end of the outer tube 20 is connected to the front cover plate 12 and is connected to the inner cavity of the gun base body 11; the air delivery pipe 30 is located on the inner side of the outer tube 20, and in the cross section, the air delivery pipe 30 is eccentrically arranged with the outer tube 20, and the rear end of the air delivery pipe 30 penetrates The front cover plate 12 and the gun seat body 11 are connected to the rear cover plate 13. The rear end of the rear cover plate 13 is provided with an air delivery connector 31 connected to the air delivery pipe 30. The air delivery connector 31 includes a front interface, a rear interface and a side interface. The front interface and the rear interface are coaxially arranged with the air delivery pipe 30, and the side interface is arranged at an angle to the axial direction of the air delivery pipe 30. A flame monitoring device 51 is installed on the rear interface. The flame monitoring device 51 can be a UV flame detector or an ion flame detector. The side interface is connected to the air inlet 32 ​​and the air pressure monitoring port 33; the rear end of the spark plug 40 is installed on the rear cover plate 13, and the spark plug 40 extends forward through the space between the outer tube 20 and the air delivery pipe 30; the fire viewing mirror 52 is installed on the rear cover plate 13, and the flame state of the front end is observed through the fire viewing mirror 52 and through the space between the outer tube 20 and the air delivery pipe 30.

[0037] The beneficial effect of adopting the above technical solution is: contrary to the conventional ignition gun gas circuit design concept, air is input from the middle, and the gas is transported in the air delivery pipe. The flame monitoring device at the rear end of the ignition gun obtains a better flame signal through the air delivery pipe with a relatively large cross-sectional area in the middle, thereby realizing reliable detection of the flame. The air delivery pipe is eccentrically arranged in the outer tube, providing sufficient space for the installation of the spark plug in a compact structure.

[0038] In other embodiments of the present invention, the inner diameter of the air delivery pipe 30 is greater than 8 mm. The beneficial effect of adopting the above technical solution is: ensuring that the rear flame monitoring device can stably detect the front flame signal of the ignition gun up to 1 meter long.

[0039] In other embodiments of the present invention, the inner hole cross-sectional area of ​​the air delivery pipe 30 accounts for 10%-35% of the inner hole cross-sectional area of ​​the outer pipe 20. The beneficial effects of adopting the above technical solution are: a large proportion helps the flame monitoring device to monitor reliably, a small proportion helps the front end of the ignition gun to stabilize the flame, and a reasonable proportion can take into account both reliable flame monitoring and stable flame establishment.

[0040] like Figure 5 As shown, in some other embodiments of the present invention, the spark plug 40 is provided with an oblique bending section 41 at the position section of the gun holder body 11. The beneficial effect of adopting the above technical solution is: fully utilizing the gun holder body structure to realize compact installation of the spark plug tail end.

[0041] like Figure 6 As shown, in some other embodiments of the present invention, the spark plug 40 is connected to the outer wall of the air delivery pipe 30 through an 8-shaped fixing clip 42, and a ceramic sleeve 43 is sleeved at the engagement between the spark plug 40 and the 8-shaped fixing clip 42. The beneficial effect of adopting the above technical solution is that the spark plug is fixed to the side of the air delivery pipe with relatively high strength and kept at an appropriate distance from the surroundings, which can prevent the spark plug from igniting in the wrong position during operation and causing ignition failure.

[0042] like Figure 9-12 As shown, in some other embodiments of the utility model, the rear end face of the mixing disc 61 is provided with a first connection port 613 for docking with the front end face of the air delivery pipe 30, and the front end face of the mixing disc 61 is provided with a second connection port 614 for docking with the combustion-supporting air secondary air pipe 64 and a third connection port 615 for docking with the front extension gas pipe. The front end face of the mixing disc 61 is provided with an eccentrically arranged outwardly convex cone portion 617, the axis of the cone portion 617 is coaxial with the combustion-supporting air secondary air pipe 64, and there are a plurality of combustion-supporting air oblique perforations 612, which obliquely penetrate the cone portion 617 at an angle to the axis of the cone portion. The mixing disc 61 is also provided with a spark plug perforation 616 for the spark plug to penetrate. The beneficial effect of adopting the above technical solution is that the oblique air flow flowing out of the combustion-supporting air oblique perforation and the parallel gas flow flowing out of the ignition gas hole form an interlaced mixture, thereby improving the mixing uniformity.

[0043] like Figure 6 , 8 As shown, in other embodiments of the utility model, a plurality of premixed air holes 34 distributed along the axial direction are provided on the air delivery pipe 30 behind the mixing disc 61. The amount of air flowing from the premixed air holes 34 into the gas delivery space in the inner cavity of the outer tube 20 accounts for 10%-20% of the total air volume, the amount of air flowing from the combustion-supporting air oblique perforations 612 into the ignition mixing space in front of the mixing disc 61 accounts for 10%-20% of the total air volume, and the amount of gas flowing from the ignition gas holes 611 into the ignition mixing space in front of the mixing disc accounts for 40%-60% of the total gas volume. Reasonable premixing and ignition mixing ratios are conducive to the stable establishment of ignition and main fire, ensuring the success rate of ignition.

[0044] like Fig. 9As shown, in some other embodiments of the utility model, the combustion-supporting air secondary air duct 64 has a forward extension section in front of the flame-stabilizing disk 62, the front end of the forward extension gas pipe 63 is in front of the front end of the combustion-supporting air secondary air duct 64, and a pressure relief hole 21 is opened on the outer tube 20 located in front of the forward extension gas pipe. The beneficial effect of adopting the above technical scheme is that the combustion-supporting air secondary air duct has a forward extension section in front of the flame-stabilizing disk, which can prevent the wind of the combustion-supporting air secondary air duct from being released in large quantities in the surrounding space of the flame-stabilizing disk, thereby increasing the speed of the mixed gas and causing the flame to go out, which indirectly plays a role in protecting the ignition. The gas in the forward extension gas pipe and the wind in the combustion-supporting air secondary air duct are finally mixed. Since there is a relatively stable ignition, these two parts of gas burn again to become the main fire. Since the ignition is stable, the main fire is also relatively stable. The pressure relief hole at the front end of the outer tube can prevent the mixture from falling out due to excessive air pressure causing the mixture flow rate to be too fast. The pressure relief hole can relieve part of the pressure, reduce the mixture flow rate, and keep it within the flame propagation speed, thereby ensuring the stable existence of the flame.

[0045] In other embodiments of the present invention, in the axial projection, the axial projection of the flame viewing mirror 52 and the axial projection of the forward gas pipe 63 have an overlapping portion. The beneficial effect of the above technical solution is to ensure that the flame state of the front end of the ignition gun can be stably observed through the flame viewing mirror.

[0046] The above embodiments are only for illustrating the technical concept and features of the utility model, and their purpose is to enable ordinary technicians in the field to understand the content of the utility model and implement it. They cannot be used to limit the protection scope of the utility model. All equivalent changes or modifications made according to the spirit of the utility model should be included in the protection scope of the utility model.

Claims

1. A premixed flame stabilizing structure for a gas ignition gun, characterized in that: The invention comprises a mixing disk, a flame stabilizing disk, a forward gas pipe and a secondary air pipe for combustion-supporting air. The outer circumference of the mixing disk and the outer circumference of the flame stabilizing disk are both in contact with the inner wall of the front end of the outer tube of the gas ignition gun. The flame stabilizing disk is located at the axial front end of the mixing disk. The tail end of the forward gas pipe is connected to the mixing disk and communicated with the inner cavity of the outer tube. The forward gas pipe runs through the flame stabilizing disk and extends to the front of the flame stabilizing disk. The tail end of the secondary air pipe for combustion-supporting air is connected to the mixing disk and communicated with the air delivery pipe in the outer tube of the gas ignition gun. Coaxially connected, the secondary air duct of the combustion-supporting air passes through the flame-stabilizing disk and extends to the front of the flame-stabilizing disk; the mixing disk is provided with an ignition gas hole that passes through from front to back, and the rear end of the ignition gas hole is connected to the inner cavity of the outer tube; the mixing disk is also provided with an oblique through hole for combustion-supporting air, and the rear end of the oblique through hole for combustion-supporting air is connected to the air delivery pipe; the flame-stabilizing disk is provided with a flame-stabilizing hole that passes through from front to back, and the opening area of ​​the flame-stabilizing hole is larger than the sum of the opening areas of the ignition gas hole and the oblique through hole for combustion-supporting air on the mixing disk.

2. The premixed flame stabilizing structure of the gas ignition gun according to claim 1, characterized in that: The front end surface of the mixing disk is provided with an eccentrically arranged outwardly convex cone portion, the axis of the cone portion is coaxial with the secondary air duct of the combustion-supporting air, and there are multiple oblique through holes for the combustion-supporting air, which penetrate the cone portion obliquely at an angle to the axis of the cone portion.

3. The premixed flame stabilizing structure of the gas ignition gun according to claim 1, characterized in that: A plurality of premixed air holes distributed along the axial direction are arranged on the air delivery pipe behind the mixing disk.

4. The premixed flame stabilizing structure of the gas ignition gun according to claim 1, characterized in that: The front end of the forward extended gas pipe is in front of the front end of the combustion-supporting air secondary air duct.

5. The premixed flame stabilizing structure of the gas ignition gun according to claim 1, characterized in that: A pressure relief hole is provided on the outer pipe located in front of the front extended gas pipe.

6. A gas ignition gun, characterized in that: It comprises an outer tube and an air delivery tube, wherein the air delivery tube is located inside the outer tube, and a gas passage is formed between the outer tube and the air delivery tube; a premixed flame stabilizing structure of the gas ignition gun as claimed in claim 1 is arranged at the front end of the outer tube.

7. The gas ignition gun according to claim 6, characterized in that: In cross section, the air delivery tube is eccentrically arranged with respect to the outer tube.

8. The gas ignition gun according to claim 7, characterized in that: It also includes a gun base unit installed at the rear end of the outer tube, the gun base unit is provided with a gas inlet and a gas pressure monitoring port, the rear end of the air delivery pipe runs through the gun base unit, a flame monitoring device is installed at the tail end of the air delivery pipe, the tail end of the air delivery pipe is also connected to the air inlet and the air pressure monitoring port via a bypass, a spark plug and a fire viewing mirror are also installed on the gun base unit, and the spark plug extends forward through the space between the outer tube and the air delivery pipe.