CN110195862B

CN110195862B - Small-size diffusion combustor that disconnect-type was preheated

Info

Publication number: CN110195862B
Application number: CN201910302239.7A
Authority: CN
Inventors: 万建龙; 何祚雯; 尚诚
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2019-04-16
Filing date: 2019-04-16
Publication date: 2020-05-19
Anticipated expiration: 2039-04-16
Also published as: CN110195862A

Abstract

The invention belongs to the technical field of micro-scale combustion, and particularly discloses a separated preheating small diffusion combustor. Including the combustor body, the combustor body is including being linked together in proper order and collinear fuel passageway, combustion chamber and exhanst gas outlet of central line, and the lateral wall symmetrical arrangement of combustion chamber has first J type to preheat the passageway and the passageway is preheated to the second J type, the air inlet department of combustion chamber is equipped with the flow distribution plate, the flow distribution plate is kept away from one side of fuel passageway is equipped with and keeps off the class board for carry out the second grade with the gas that lets in among the fuel passageway and shunt in order to realize that the gas mixes with the second level of oxidant. The invention can realize the full preheating of the oxidant, and realize twice shunting and three-stage mixing, can effectively solve the problems of poor flame stability, low combustion efficiency, easy tempering, complex structure and the like, and has the characteristics of simple structure, good mixing effect, wide combustible range, high combustion efficiency, safety and reliability.

Description

Small-size diffusion combustor that disconnect-type was preheated

Technical Field

The invention belongs to the technical field of micro-scale combustion, and particularly relates to a separated preheating small diffusion combustor.

Background

The rapid development of microelectromechanical devices technology has led to the emergence of numerous small power devices or systems, such as small probes, small robots, small satellites, and small propulsion systems. At present, most of the devices are driven by batteries, however, the batteries have the defects of small energy density, large weight and volume, long charging time and the like, and the energy density of hydrogen and hydrocarbon fuel is dozens of times higher than that of the traditional batteries. Thus, combustion-based small power plants have a great potential to replace traditional batteries. Researchers at home and abroad have successfully manufactured small gas turbines, small rotary engines, small rockets, small array propulsion systems, and the like. The burner is a key component of a small power device or system, and the design and development of the stable, efficient and safe small burner has important significance for the application of MEMS devices.

Premixed combustion and diffusion combustion can be classified according to whether the fuel and the oxidant are premixed before entering the combustion chamber. Since compact burners are used primarily to provide a direct power or heat source for various MEMS devices, safety is an important factor to consider first. Since the premixed combustion is easy to generate dangerous combustion phenomena such as backfire and the like, diffusion combustion modes of fuel and oxidant are more and more concerned, but two key problems need to be solved for realizing efficient and stable diffusion combustion.

The first problem is how to mix the fuel and oxidant sufficiently in a very short time, and poor mixing can lead to poor flame stability and combustion efficiency. For example, the prior art has found a "flame street" phenomenon in conventional small diffusion burners, which is caused by inadequate mixing of the fuel and oxidant. To this end, researchers have proposed a variety of ways to solve the mixing problem. For example, researchers at the university of Maryland, USA, have designed a perpendicular arrangement of J-shaped oxidant preheating channels and fuel channels, which results in a stronger injection of fuel as oxidant enters the combustion chamber at a faster rate along the horizontal channels, thereby enhancing the mixing of the two different gases. However, this method requires a large velocity difference between the two flows, otherwise it is difficult to obtain a good mixing effect, and it is difficult to obtain a stable and symmetrical flow field in the vertical ejection manner. The prior art also teaches a Y-shaped diffusion burner with porous media, which, although the mixing of fuel and oxidant is improved, the degree of improvement is limited and the method increases the flow resistance.

A second challenge is how to ensure that the flame remains stable over a wide operating range. Since the ratio of the surface area to the volume of the small combustion chamber is increased by 2 orders of magnitude compared to the conventional dimensions, the heat dissipation loss through the solid wall surface is greatly increased, which leads to poor flame stability and easy occurrence of flameout. To this end, various researchers have employed ways to improve flame stability in small burners. For example, the prior art proposes a so-called "swiss roll" configuration. Although the combustible range of the flame in the combustor with the special structure is wider, the combustor can only be used for premixed combustion at present and has the defects of easy occurrence of backfire, complex structure, larger processing difficulty and the like.

Based on the defects and shortcomings, the field needs to further improve the existing small diffusion burner, construct a separate preheating small diffusion burner with simple structure, good mixing effect, wide combustible range, high combustion efficiency, safety and reliability, and solve the problems of the existing small diffusion burner.

Disclosure of Invention

Aiming at the defects or the improvement requirements of the prior art, the invention provides a separated preheating small diffusion burner, wherein the characteristics of the small diffusion burner and the characteristics of combustion premixing and safe process are combined, and key components of the small diffusion burner, such as a preheating channel, a combustion chamber, a premixing structure and a specific arrangement mode of the preheating channel, the combustion chamber and the premixing structure, are researched and designed, so that twice shunting and three-stage mixing can be correspondingly realized, and the problems of poor flame stability, low combustion efficiency, easiness in tempering, complex structure and the like can be effectively solved.

In order to achieve the purpose, the invention provides a separated preheating small diffusion burner which is characterized by comprising a burner body, wherein the burner body comprises a fuel channel, a combustion chamber and a flue gas outlet which are communicated in sequence and have collinear central lines, wherein,

a first J-shaped preheating channel and a second J-shaped preheating channel are symmetrically arranged on the outer side wall of the combustion chamber, air inlets of the first J-shaped preheating channel and the second J-shaped preheating channel are arranged at one end of the flue gas outlet, and air outlets of the first J-shaped preheating channel and the second J-shaped preheating channel are converged with an air outlet of the fuel channel at the air inlet of the combustion chamber;

the fuel gas inlet of the combustion chamber is provided with a splitter plate, and the splitter plate comprises an upper splitter plate and a lower splitter plate which are symmetrically arranged and is used for splitting the fuel gas introduced into the fuel channel for the first time so as to realize the first-stage mixing of the fuel gas and the oxidant; and one side of the splitter plate, which is far away from the fuel channel, is provided with a flow baffle plate for secondarily splitting the fuel gas introduced into the fuel channel so as to realize secondary mixing of the fuel gas and the oxidant, and the secondary mixed gas is subjected to tertiary mixing and combustion in the combustion chamber.

Further, the first and second J-shaped preheating passages are arranged in parallel with the combustion chamber.

Further, the width of the air inlet of the first J-shaped preheating channel is larger than that of the air outlet of the first J-shaped preheating channel, and the width of the air inlet of the second J-shaped preheating channel is larger than that of the air outlet of the second J-shaped preheating channel.

Furthermore, the central line of the flow dividing plate and the central line of the flow baffle are collinear with the central line of the fuel channel.

Further, the blockage ratio of the flow distribution plate is 0.4-0.8, and the distance between the upper flow distribution plate and the lower flow distribution plate is smaller than the width of the fuel channel; preferably, the blockage ratio of the flow distribution plate is 0.6, and preferably, the distance between the upper flow distribution plate and the lower flow distribution plate is 1-5 mm.

Further, the blockage ratio of the flow baffle is 0.2-0.7, and preferably, the blockage ratio of the flow baffle is 0.5.

Furthermore, the upper splitter plate and the lower splitter plate are triangular or trapezoidal in shape; the flow baffle is in any one shape of a triangle, a semicircle or a trapezoid.

Further, the surface of the baffle plate is coated with a catalyst.

Further, the catalyst is any one or more of platinum, nickel and rhodium.

Generally, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:

1. the invention combines the characteristics of the small diffusion burner and the characteristics of combustion premixing and safe process thereof, researches and designs key components of the small diffusion burner, such as a preheating channel, a combustion chamber, a premixing structure and a specific arrangement mode thereof, can correspondingly realize the sufficient preheating of an oxidant, and realize twice shunting and three-stage mixing, can effectively solve the problems of poor flame stability, low combustion efficiency, easy tempering, complex structure and the like, and simultaneously has the characteristics of simple structure, good mixing effect, wide combustible range, high combustion efficiency, safety and reliability, thereby being particularly suitable for providing power or heat sources for small power or heating equipment.

2. The first J-shaped preheating channel and the second J-shaped preheating channel are arranged in parallel with the combustion chamber, so that the heat exchange area between the preheating channel and the combustion chamber is increased, the preheating temperature of the oxidant can be obviously increased on one hand, and the flow velocity of the oxidant can be increased by the obvious thermal expansion effect on the other hand, so that the injection mixing effect on the fuel is enhanced.

3. The width of the air inlet of the preheating channel is larger than that of the air outlet of the preheating channel, so that the injection effect of the oxidant can be enhanced, and the mixing effect of the fuel gas and the oxidant is improved.

4. The flow distribution plate, the flow baffle plate, the fuel channel and the central line of the combustion chamber are collinear, and the two J-shaped oxidant preheating channels are symmetrically distributed on two sides of the combustion chamber and the fuel channel and are in parallel structures, so that the symmetry and the stability of a flow field and flame can be ensured.

5. The distance between the upper splitter plate and the lower splitter plate is smaller than the width of the fuel channel, and the fuel gas splitter plate is used for realizing the first splitting of fuel gas, so that the split fuel gas is subjected to collision mixing under the injection action of oxidants on two sides, meanwhile, a small amount of fuel gas passing through the space between the upper splitter plate and the lower splitter plate is subjected to secondary splitting on the flow baffle plate and is subjected to secondary mixing with gas on two sides, and meanwhile, a backflow area and a low-speed area behind the flow baffle plate are used for realizing tertiary mixing, so that the flame anchoring performance is improved.

6. The shapes and sizes of the splitter plate and the flow baffle plate can be optimally designed, so that better mixing effect and stable combustion effect can be obtained.

In a word, the invention overcomes the defects of the prior art, and utilizes a plurality of different physical mechanisms in the three-stage mixing process to achieve the full mixing between the fuel and the oxidant; the J-shaped oxidant preheating channel can obviously improve the preheating temperature of the oxidant and the fuel, thereby realizing the wide flame combustible (operation) range; the flame anchoring performance is improved by utilizing a backflow area and a low-speed area behind the flow baffle. Therefore, the invention can effectively improve the flame stability and the combustion efficiency in the small diffusion burner and is widely suitable for various small power or heating devices.

Drawings

FIG. 1 is a schematic structural diagram of a separate preheating small diffusion burner according to the present invention.

The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein: 1-fuel channel, 2-first outlet, 3-flow dividing plate, 4-second outlet, 5-flow blocking plate, 6-combustion chamber, 7-first J-shaped preheating channel, 8-second J-shaped preheating channel and 9-smoke outlet.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Fig. 1 is a schematic structural diagram of a separate preheating small diffusion burner according to the present invention. The combustor comprises a combustor body, wherein the combustor body comprises a fuel channel 1, a combustion chamber 6 and a flue gas outlet 9 which are sequentially communicated and have collinear central lines, a first J-shaped preheating channel 7 and a second J-shaped preheating channel 8 are symmetrically arranged on the outer side wall of the combustion chamber 6, air inlets of the first J-shaped preheating channel 7 and the second J-shaped preheating channel 8 are arranged at one end of the flue gas outlet 9, and air outlets of the first J-shaped preheating channel 7 and the second J-shaped preheating channel 8 are converged with an air outlet of the fuel channel 1 at the air inlet of the combustion chamber 6; and a first J-shaped preheating passage 7 and a second J-shaped preheating passage 8 are arranged in parallel with the combustion chamber 6. A splitter plate 3 is arranged at an air inlet of the combustion chamber 6, and the splitter plate 3 comprises an upper splitter plate and a lower splitter plate which are symmetrically arranged and used for splitting the fuel gas introduced into the fuel channel 1 for the first time so as to realize the first-stage mixing of the fuel gas and the oxidant; one side of the splitter plate 3, which is far away from the fuel channel 1, is provided with a flow baffle plate 5 for secondarily splitting the fuel gas introduced into the fuel channel 1 to realize secondary mixing of the fuel gas and the oxidant. The gas mixed in the second stage immediately enters the combustion chamber 6, and meanwhile, a backflow area and a low-speed area are formed behind the flow baffle, so that third-stage mixing of the gas can be realized, and the flame anchoring performance is improved.

In order to enhance the injection effect of the oxidant on the divided fuel gas and improve the mixing effect, in the invention, the width of the gas inlet of the first J-shaped preheating channel 7 is larger than that of the gas outlet thereof, and the width of the gas inlet of the second J-shaped preheating channel 8 is larger than that of the gas outlet thereof, so that the gas flow area is reduced, the gas flow rate is increased, and the static pressure at the gas outlet of the preheating channel is further reduced.

In the present invention, the width of the fuel passage 1, the width of the first J-shaped preheating passage 7 and the width of the second J-shaped preheating passage 8 are all smaller than the width of the combustion chamber 6.

In the invention, the central line of the flow dividing plate 3 and the central line of the flow baffle plate 5 are collinear with the central line of the fuel channel 1, and the symmetrical arrangement structure can ensure the symmetry and stability of a flow field and flame.

In the invention, the blockage ratio of the splitter plate 3 is 0.4-0.8, and the distance between the upper splitter plate and the lower splitter plate is less than the width of the fuel channel 1; preferably, the blocking ratio of the splitter plate 3 is 0.6, and the distance between the upper splitter plate and the lower splitter plate is preferably 1-5 mm.

Specifically, as shown in fig. 1, the first J-shaped preheating channel 7 and the second J-shaped preheating channel 8 of the present invention are symmetrically distributed on both sides of the combustion chamber 6 and the fuel channel 1, and the first outlet 2 and the second outlet 4 are symmetrically configured at the air inlet of the combustion chamber 6, so as to ensure the symmetry of the flow field and the flame. The air outlets of the first J-shaped preheating channel 7 and the second J-shaped preheating channel 8 are converged at the air inlet of the combustion chamber 6, the flow baffle plate 5 is positioned on one side of the flow distribution plate 3, which is far away from the fuel channel 1, and the flow distribution plate 3 is positioned between the combustion channel 1 and the flow baffle plate 5. This configuration facilitates thorough mixing of the two gases and a symmetrically stable flame.

The oxidant is obviously preheated by the combustion chamber through the J-shaped structure, the fuel gas firstly enters the oxidant preheating channel through the first outlet 2 part at the splitter plate 3, and the first-stage mixing is carried out under the injection and collision action of oxidant gas flows at two sides; then the rest of the fuel gas is divided into two parts through a second outlet 4 at the flow baffle 5, and the two parts are subjected to secondary mixing under the injection and collision effects of the first-stage mixed gas at the two sides; and finally, carrying out third-stage mixing at the inlet of the combustion chamber 6, immediately igniting and combusting, and discharging high-temperature flue gas from a flue gas outlet 9 of the combustion chamber 6.

The mixing effect and the flame stabilizing effect between the fuel and the oxidant can be further improved by changing the sizes of the fuel channel and the J-shaped oxidant preheating channel, or by changing the shape and the size of the splitter plate, or by changing the shape and the size of the baffle plate, for example, the baffle plate 5 can be any one of a triangle, a semicircle or a trapezoid, and the blocking ratio (the ratio of the width of the baffle plate 5 to the width of the combustion chamber) can be 0.2-0.7, preferably, the blocking ratio of the baffle plate 5 is 0.5.

The present invention can also coat a catalyst on the surface of the baffle plate 5, such as: platinum, nickel, rhodium, etc. to improve the combustion stabilizing effect.

Example 1:

the inlet width of the fuel channel is 3mm, and the inlet widths of the two J-shaped oxidant preheating channels are both 3 mm. The sectional area of the fuel passage is smaller than that of the combustion chamber, and the distance between the fuel passage and the wall surface of the combustion chamber is 1 mm. The length and the width of the two rectangular splitter plates are respectively 2mm and 1.5mm, the distance between the two splitter plates is 2mm, and the length and the width of the rectangular baffle plate are respectively 2mm and 5 mm. The distance between the first outlet and the second outlet is 1 mm. The length and width of the combustion chamber were 50mm and 7mm, respectively. The surface of the diverter block is not coated with a platinum catalyst.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A separated preheating small diffusion burner is characterized by comprising a burner body, wherein the burner body comprises a fuel channel (1), a combustion chamber (6) and a flue gas outlet (9) which are communicated in sequence and have collinear central lines, wherein,

a first J-shaped preheating channel (7) and a second J-shaped preheating channel (8) are symmetrically arranged on the outer side wall of the combustion chamber (6), air inlets of the first J-shaped preheating channel (7) and the second J-shaped preheating channel (8) are arranged at one end of the flue gas outlet (9), and air outlets of the first J-shaped preheating channel (7) and the second J-shaped preheating channel (8) are converged with an air outlet of the fuel channel (1) at the air inlet of the combustion chamber (6);

a splitter plate (3) is arranged at an air inlet of the combustion chamber (6), the splitter plate (3) comprises an upper splitter plate and a lower splitter plate which are symmetrically arranged, and the splitter plate is used for splitting the fuel gas introduced into the fuel channel (1) for the first time so as to realize the first-stage mixing of the fuel gas and an oxidant; one side of the splitter plate (3) far away from the fuel channel (1) is provided with a flow baffle plate (5) for secondarily splitting the fuel gas introduced into the fuel channel (1) to realize secondary mixing of the fuel gas and an oxidant, and tertiary mixing and combustion are carried out on the secondary mixed gas in a combustion chamber (6).

2. The compact diffusion burner of claim 1, characterized in that the first and second J-shaped preheating channels (7, 8) are arranged in parallel with the combustion chamber (6).

3. The compact diffusion burner of claim 1, wherein the inlet width of the first J-shaped preheating channel (7) is greater than the outlet width thereof, and the inlet width of the second J-shaped preheating channel (8) is greater than the outlet width thereof.

4. The small diffusion burner according to any one of claims 1 to 3, wherein the center line of the flow dividing plate (3) and the center line of the baffle plate (5) are collinear with the center line of the fuel passage (1).

5. The compact diffusion burner of claim 1 or 2, characterized in that the blocking ratio of the splitter plate (3) is 0.4-0.8 and the distance between the upper and lower splitter plates is smaller than the width of the fuel channel (1).

6. The compact diffusion burner of claim 1 or 2, wherein the flow distribution plate (3) has a blockage ratio of 0.6, and the distance between the upper flow distribution plate and the lower flow distribution plate is 1 to 5 mm.

7. The compact diffusion burner of claim 1, wherein the baffle plate (5) has a blockage ratio of 0.2 to 0.7.

8. The compact diffusion burner of claim 1, characterized in that the choke ratio of the baffle plate (5) is 0.5.

9. The compact diffusion burner of claim 1, wherein the upper and lower splitter plates are triangular or trapezoidal in shape; the flow baffle (5) is in any one shape of a triangle, a semicircle or a trapezoid.

10. The compact diffusion burner of claim 1, characterized in that the surface of the baffle plate (5) is coated with a catalyst.

11. The compact diffusion burner of claim 10, wherein the catalyst is any one or more of platinum, nickel, rhodium.