A small burner with four inlets partially filled with porous media and its application

Abstract

The present invention discloses a small burner with four inlets partially filled with porous media and its application. The burner includes a main body, a premixed gas inlet, and a smoke exhaust outlet. The main body is a rectangular cavity structure with a combustion chamber inside. The premixed gas inlet and the smoke exhaust outlet are arranged on the left and right side walls of the main body. A premixed gas inlet is provided at the upper and lower parts of each side wall, and a smoke exhaust outlet is provided between the two premixed gas inlets. The premixed gas inlets and the smoke exhaust outlet on the two side walls are symmetrically arranged. The top and bottom surfaces of the main body are configured as radiant plates. The combustion chamber consists of a porous medium zone, a free combustion zone, and a secondary collision zone. The free combustion zone is located between two opposing premixed gas inlets. The secondary collision zone is located in the middle between the two free combustion zones and is vertically connected to the two free combustion zones. The porous medium zone is located between the secondary collision zone and the smoke exhaust outlet, and the porous medium zone is filled with porous media. This device can effectively improve the temperature of the radiant plate and the uniformity of the temperature distribution.

Description

Technical Field

[0001] The invention relates to the technical field of small burners, and in particular to a four-inlet small burner partially filled with porous media and application thereof. Background Art

[0002] In the development of micro-electromechanical systems (MEMS), the shortcomings of its power supply components, such as low energy density, large mass, and short battery life, have become increasingly prominent, limiting the miniaturization and portability of electronic equipment and mechanical products. Micro-thermophotovoltaic systems based on microscale combustion have significant advantages such as no moving parts, high energy density, small size, light mass, and long and stable energy supply time. They are micro-power systems with good application prospects. The working principle of the micro-thermophotovoltaic system is to use photoelectric elements to convert the high-temperature wall radiation energy of the micro-burner into electrical energy. Therefore, in the design process of the micro-burner, it is usually necessary to increase the wall temperature level and wall temperature uniformity of the micro-burner as much as possible, so as to improve the energy conversion efficiency of the system. In addition, micro-burners with uniform external surface high temperature distribution also have important applications in the fields of industrial heating and drying. For example, radiant heaters mainly use infrared radiation energy emitted outward from the high-temperature surface of the heater to heat and dry objects. During radiation heating, a higher burner wall temperature level is conducive to improving radiation intensity, thereby improving heating efficiency; in addition, large wall temperature differences can also lead to uneven radiation heating, affecting product quality. Therefore, the burners required for radiation heating have high requirements for the uniformity of the burner outer surface temperature distribution. Summary of the Invention

[0003] The purpose of the present invention is to provide a four-inlet small burner partially filled with porous media and its application, which can effectively improve the wall temperature level and wall temperature uniformity of the micro burner, thereby improving the energy conversion efficiency of the system.

[0004] To achieve the above-mentioned purpose, the present invention protects, on the one hand, a four-inlet small burner partially filled with porous medium, including a main body, a premixed gas inlet, and a smoke exhaust outlet. The main body is a rectangular cavity structure with a combustion chamber inside. The premixed gas inlet and the smoke exhaust outlet are arranged on the left and right side walls of the main body, and a premixed gas inlet is respectively provided on the upper and lower parts of each side wall, and a smoke exhaust outlet is provided in the middle of the two premixed gas inlets; the premixed gas inlet and the smoke exhaust outlet on the two side walls are symmetrically arranged on the left and right; the top and bottom surfaces of the main body are set as radiation plates; the combustion chamber is composed of a porous medium zone, a free combustion zone, and a secondary collision zone, the free combustion zone is located between the two opposite premixed gas inlets, and the secondary collision zone is located in the middle between the two free combustion zones and is vertically connected to the two free combustion zones; the porous medium zone is located between the secondary collision zone and the smoke exhaust outlet.

[0005] Furthermore, the upper and lower side walls of the body are configured as inlet side walls, and an inlet step is provided between the inlet side walls and the premixed gas inlet.

[0006] Furthermore, the outer surface of the radiation plate is coated with a wavelength selective radiation coating.

[0007] Furthermore, the porous medium zone is filled with porous medium I, and the porosity of the porous media is the same.

[0008] Furthermore, the porosity of the porous medium is 40% to 90%, and the pore size is 30PPI to 100PPI.

[0009] Preferably, the porosity of the porous medium is 85%, and the pore size of the porous medium is 60 PPI.

[0010] Furthermore, the porous medium zone is filled with porous medium II and porous medium III, the porous medium II is close to the free combustion zone, the porous medium III is located between two porous media II, and the porosity of the porous medium II is different from that of the porous medium III.

[0011] Furthermore, the porosity of the porous medium II is less than 60%, and the porosity of the porous medium III is greater than 60%.

[0012] On the other hand, the present invention protects two applications of the above-mentioned burner. One is when it is used in the field of micro-thermophotovoltaic systems, the radiation plate is facing the photovoltaic cell module in the micro-thermophotovoltaic device; the other is when it is used in the field of radiation heating, the radiation plate is facing the object to be heated or dried.

[0013] The beneficial effects of the present invention are as follows: first, the present invention adopts a four-corner collision jet layout air intake method, which can form a uniformly distributed flame high-temperature zone in the combustion chamber, avoiding the problem of local high temperature in the single-sided air intake of the traditional flat burner, and the present invention can achieve a higher uniformity of the radiation wall temperature; second, the present invention adopts a form of partially filling porous media at the smoke exhaust outlet, firstly partially filling the porous medium in the combustion channel, strengthening the heat transfer between the high-temperature zone upstream of the inlet and the low-temperature zone downstream of the outlet, thereby effectively improving the uniformity of the wall temperature; at the same time, a secondary collision zone that is not filled with porous media is left between the two smoke exhaust outlets, and the two relative inlet air flows first collide once in the free combustion zone, and then The two air flows generate collision flow again in the secondary collision area in the middle of the smoke exhaust outlet. The multiple collisions of the air flows are conducive to the formation of a high-intensity turbulent field, thereby enhancing the heat transfer between the gas and the wall and increasing the temperature level of the radiation plate; thirdly, the porous medium area in the present invention adopts a step-type filling method. The porous medium is divided into two layers. The porosity of the porous medium layer downstream of the inlet is smaller than the porosity of the porous medium layer near the outlet. This distribution method suppresses the problem of direct discharge of part of the inlet gas after flowing through the porous medium area, enhances the proportion of gas in the inlet gas flowing to the free combustion area to produce collision jets, and prolongs the residence time of the smoke in the combustion chamber, thereby enhancing heat transfer and increasing the wall temperature level. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the three-dimensional structure of a small burner;

[0015] Figure 2 for Figure 1 sectional view of

[0016] Figure 3 for Figure 2 The porous medium area contains a front view of a small porous medium burner;

[0017] Figure 4 for Figure 3 AA view in the;

[0018] Figure 5 for Figure 2 Front view of a small burner with two porous media filled in the porous media area;

[0019] Figure 6 This is a comparison chart of the radiation plate temperature of a small burner at different inlet velocities;

[0020] Figure 7 This is the distribution diagram of the temperature uniformity index of the radiation plate of a small burner at different inlet velocities;

[0021] In the figure, 1-main body, 2-premixed gas inlet, 3-smoke exhaust outlet, 4-radiation plate, 5-porous medium area, 51-porous medium I, 52-porous medium II, 53-porous medium III, 6-free combustion zone, 7-secondary collision zone, 8-inlet side wall, 9-inlet step. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1

[0024] like Figures 1-4 As shown, a small burner with four inlets partially filled with porous media includes a main body 1, a premixed gas inlet 2, and a smoke exhaust outlet 3. The main body 1 is a rectangular cavity structure with a combustion chamber inside. The premixed gas inlet 2 and the smoke exhaust outlet 3 are arranged on the left and right side walls of the main body 1. A premixed gas inlet 2 is provided at the upper and lower portions of each side wall, and a smoke exhaust outlet 3 is provided between the two premixed gas inlets 2. The premixed gas inlets 2 and the smoke exhaust outlet 3 on the left and right side walls are arranged symmetrically, that is, the two upper premixed gas inlets 2 are opposite each other, the two lower premixed gas inlets 2 are opposite each other, and the middle smoke exhaust outlets 3 are opposite each other. The upper and lower surfaces of the main body 1 are configured as radiating plates 4. The area of ​​the radiating plates 4 is larger than that of the other side walls, and the outer surface of the radiating plates 4 is coated with a wavelength-selective radiation coating. The combustion chamber consists of a porous medium zone 5, a free combustion zone 6, and a secondary collision zone 7. The free combustion zone 6 is located between two opposing premixed gas inlets 2. The secondary collision zone 7 is located in the middle between the two free combustion zones 6 and is vertically connected to the two free combustion zones 6. The two free combustion zones 6 and the secondary collision zone 7 form an "I"-shaped cavity structure. The four premixed gas inlets 2 are located at the four corners of the "I"-shaped structure, forming a structural layout with two opposing each other. Figure 3 As shown, the inlet airflow first undergoes a collision flow in the free combustion zone 6, and then enters the secondary collision zone 7 for another collision flow. The multiple collisions of the airflow are conducive to the formation of a high-intensity turbulent field, thereby enhancing the heat transfer between the gas and the wall and increasing the temperature level of the radiation plate.

[0025] There are two smoke exhaust outlets, and the direction of the smoke exhaust outlet is parallel to the air intake direction. At the same time, each outlet is located in the middle of the two inlets on the same side, that is, in the middle of the left and right sides of the "I"-shaped structure. The porous medium area is located between the secondary collision area 7 and the smoke exhaust outlet 3. The porous medium area 5 in this embodiment adopts a uniform filling method, that is, there is only one porous medium I51. The porosity of the porous medium I51 is 40% to 90%, and the pore size of the porous medium I51 is 30PPI to 100PPI. Preferably, the porosity is 85% and the pore density is 60PPI.

[0026] The specific dimensions of the burner in this embodiment are: the width of the premixed gas inlet 2 is 1.5 mm, and the height is 2 mm; the width of the flue gas outlet 3 is 1.5 mm, and the height is 2 mm; the thickness of the radiation plate 4 is 0.5 mm; the length of the porous medium zone is 13 mm, the width is 5.5 mm, and the height is 2 mm; the length of the main body 1 is 20 mm, the width is 16 mm, and the height is 3 mm. The burner adopts a premixed combustion mode of hydrogen and air. The materials of the main body 1 and the radiation plate 4 are both 316 stainless steel, and its density, specific heat and thermal conductivity are 8000 kg / m3, 503 J / (kg·K) and 16.3 W / (m·K), respectively. Using the CFD calculation method, a numerical simulation of the combustion characteristics in a small burner was carried out when the hydrogen-air equivalence ratio was 1.0 and the inlet velocity was 3 m / s, 5 m / s, 7 m / s, and 9 m / s. The results are as follows Figure 6 and Figure 7 As shown, control group 1 is a conventional flat-plate burner with the same dimensions as this embodiment; control group 2 is a four-inlet burner of the present invention with the same dimensions as this embodiment, except that the combustion chamber of control group 2 is not filled with porous medium I51.

[0027] Figure 6 The temperature of the radiation plate 4 at different inlet velocities of the present invention is given. Figure 6 It can be clearly seen that under different inlet velocity conditions, the temperature of the radiation plate 4 obtained in the embodiment of the present invention is higher than that of the control group 1 and the control group 2, and the higher the inlet velocity, the more obvious the advantage of this embodiment.

[0028] Figure 7 The temperature uniformity index size distribution of the radiation plate of the present invention at different inlet velocities is given. Figure 7 As can be clearly seen in the graph, the radiant plate temperature uniformity index of the embodiment of the present invention is the highest under different inlet velocity conditions, indicating that this embodiment can achieve a more uniform radiant temperature distribution. When the burner is used in a micro-thermophotovoltaic device, the embodiment of the present invention can achieve higher system output power; when the burner is used for industrial heating or drying, the embodiment of the present invention achieves higher heating speed and drying quality.

[0029] like Figure 2 、 Figure 3 As shown, the upper and lower side walls of the body 1 are configured as inlet side walls 8. An inlet step 9 is provided between the inlet side wall 8 and the premixed gas inlet 2. This step serves to anchor the flame and delay the residence time of the combustion gas in the burner, thereby improving the flame combustion stability and the temperature of the radiation plate 4. The porous medium 151 has the same porosity.

[0030] The burner adopts the above-mentioned four-inlet small burner partially filled with porous medium. When it is used in the field of micro-thermophotovoltaic system, the radiation plate 4 is facing the photovoltaic cell module in the micro-thermophotovoltaic device; the burner adopts the above-mentioned four-inlet small burner partially filled with porous medium. When it is used in the field of radiation heating, the radiation plate 4 is facing the object to be heated or dried.

[0031] Example 2

[0032] The difference between this embodiment and embodiment 1 is that the filling method of the porous medium area 5 is adjusted from the uniform filling method of embodiment 1 to a step filling method, and the rest is consistent with embodiment 1, such as Figure 5 As shown. The porous medium area adopts a step-type filling method. At this time, the porous medium is divided into two layers, namely porous medium II52 and porous medium III53. Porous medium II52 is close to the free combustion zone 6, and porous medium III53 is located between the two porous media II52. The porosity of porous medium II52 is different from that of porous medium III53. Among them, the porosity of porous medium II52 is less than 60%, and the porosity of porous medium III53 is greater than 60%. Preferably, the porosity of porous medium II52 is 50% and the pore density is 60PPI, and the porosity of porous medium III53 is 85% and the pore density is 60PPI. The effect of this embodiment is as follows Figure 6 and Figure 7 As shown in the figure, after the filling method of the porous medium area is adjusted from uniform filling to step filling, the temperature level of the radiation plate and the temperature uniformity index of the radiation plate are both higher than the calculation results of Example 1. This also shows that compared with the uniform filling method, the step filling method is conducive to further improving the radiation temperature level and uniformity of the burner surface.

[0033] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Various changes that can be made within the scope of knowledge possessed by technicians in the relevant technical field without departing from the spirit of the present invention are all within the scope of protection of the claims of the present invention.

Claims

1. A small burner with four inlets partially filled with porous media, characterized by: The invention comprises a main body (1), a premixed gas inlet (2), and a smoke exhaust outlet (3); the main body (1) is a rectangular parallelepiped cavity structure, the interior of which is a combustion chamber; the premixed gas inlet (2) and the smoke exhaust outlet (3) are arranged on the left and right side walls of the main body (1); one premixed gas inlet (2) is arranged on the upper part and the lower part of each side wall; and one smoke exhaust outlet (3) is arranged between the two premixed gas inlets (2); the premixed gas inlets (2) and the smoke exhaust outlet (3) on the two side walls are both on the left and right sides. Symmetrical arrangement; the top and bottom surfaces of the body (1) are set as radiation flat plates (4); the combustion chamber is composed of a porous medium area (5), a free combustion area (6), and a secondary collision area (7); the free combustion area (6) is located between the two opposite premixed gas inlets (2); the secondary collision area (7) is located in the middle between the two free combustion areas (6) and is vertically connected to the two free combustion areas (6); the porous medium area (5) is located between the secondary collision area (7) and the smoke exhaust outlet (3); The upper and lower side walls of the body (1) are configured as inlet side walls (8), and an inlet step (9) is provided between the inlet side walls (8) and the premixed gas inlet (2); The porous medium zone (5) is filled with a porous medium II (52) and a porous medium III (53), wherein the porous medium II (52) is close to the free combustion zone (6), and the porous medium III (53) is located between the two porous media II (52), and the porosity of the porous medium II (52) and the porous medium III (53) are different; The porosity of the porous medium II (52) is less than 60%, and the porosity of the porous medium III (53) is greater than 60%.

2. A four-inlet small burner partially filled with porous media according to claim 1, characterized in that: The outer surface of the radiation plate (4) is coated with a wavelength selective radiation coating.

3. Application of a small burner, characterized in that, The burner adopts a small burner with four inlets partially filled with porous media as described in any one of claims 1-2. When it is used in the field of micro-thermophotovoltaic system, the radiation plate (4) faces the photovoltaic module in the micro-thermophotovoltaic device.

4. Application of a small burner, characterized in that, The burner adopts a small burner with four inlets partially filled with porous media as described in any one of claims 1-2. When used in the field of radiation heating, the radiation plate (4) faces the object to be heated or dried.

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