Plateau type fuel oil burner with high injection smoke and design method
阅读说明：本技术 一种具有高引射烟气的高原型燃油燃烧器及设计方法 (Plateau type fuel oil burner with high injection smoke and design method ) 是由 崔运静 仇性启 谢凯 王建新 邱洪波 王洪珍 毛育文 于 2019-10-11 设计创作，主要内容包括：本发明涉及燃烧设备技术领域,具体涉及一种具有高引射烟气的高原型燃油燃烧器及设计方法。具有高引射烟气的高原型燃油燃烧器包括：雾化喷嘴、稳焰盘、燃烧筒和燃烧腔,所述雾化喷嘴位于稳焰盘中部,所述燃烧筒套装于稳焰盘外侧,所述燃烧筒设置于燃烧腔中,所述燃烧腔内侧铺设有蓄热材料。它具有低压空气辅助雾化喷嘴,改善高原高寒环境下机械式雾化喷嘴雾化效果差的问题；采用高温烟气自循环技术设计燃烧筒结构实现燃烧室的烟气高循环率,解决燃烧污染排放较高的问题；采用流动阻力较小的叶片式旋流稳焰盘稳定火焰；采用蓄热材料强化燃油燃烧,提高燃烧效率。(The invention relates to the technical field of combustion equipment, in particular to a plateau type fuel oil burner with high injection smoke and a design method. High prototype fuel oil burner with high drawing flue gas includes: the combustion device comprises an atomizing nozzle, a flame stabilizing disc, a combustion barrel and a combustion cavity, wherein the atomizing nozzle is positioned in the middle of the flame stabilizing disc, the combustion barrel is sleeved on the outer side of the flame stabilizing disc, the combustion barrel is arranged in the combustion cavity, and a heat storage material is laid on the inner side of the combustion cavity. The mechanical atomizing nozzle is provided with the low-pressure air auxiliary atomizing nozzle, so that the problem of poor atomizing effect of the mechanical atomizing nozzle in a highland and high-cold environment is solved; the high-temperature flue gas self-circulation technology is adopted to design a combustion cylinder structure so as to realize high flue gas circulation rate of the combustion chamber and solve the problem of high combustion pollution emission; stabilizing flame by adopting a blade type rotational flow flame stabilizing disc with smaller flow resistance; the heat storage material is adopted to strengthen the fuel oil combustion and improve the combustion efficiency.)
1. The utility model provides a plateau type fuel oil burner with high flue gas that draws, its characterized in that includes: atomizing nozzle (100), steady flame dish (200), a combustion section of thick bamboo (300) and combustion chamber (400), atomizing nozzle (100) are located steady flame dish (200) middle part, a combustion section of thick bamboo (300) suit is in steady flame dish (200) outside, a combustion section of thick bamboo (300) set up in combustion chamber (400), heat accumulation material (500) have been laid to combustion chamber (400) inboard.
2. The high altitude type fuel oil burner with high ejection smoke of claim 1, characterized in that: the atomizing nozzle (100) comprises an oil core (1), a rotational flow core (3) and a shell (2), the oil core (1) is in threaded connection with the shell (2), an oil through cavity (8a) is formed in the center of the oil core (1), an air inlet hole (9) is formed in the shell (2), the oil core (1) is located in the shell (2), a ventilation cavity (9a) is formed between the outer wall of the oil core (1) and the inner wall of the shell (2) in a surrounding mode, the rotational flow core (3) is connected to the right end of the oil core (1) and located in the shell (2), a pressurizing oil through cavity (8b) communicated with the oil through cavity (8a) of the oil core (1) is formed in the center of the rotational flow core (3), the right end face of the rotational flow core (3) is a conical face, a plurality of rotational flow grooves (5) communicated with the ventilation cavity (9a) are formed in the right end face of the rotational flow core (, the right end of the rotational flow core (3) is provided with a conical oil hole (8c) communicated with the pressurizing oil through cavity (8b), the right end of the shell (2) is provided with a conical spray hole (2a), the right end of the conical oil hole (8c), the rotational flow groove (5) and the left end of the conical spray hole (2a) are mutually converged, the conical oil hole (8c) and the conical spray hole (2a) form a Laval spray pipe, and a conical hole bus of the conical oil hole (8c) is a Wittonsisky curve.
3. The high altitude type fuel oil burner with high ejection smoke of claim 2, characterized in that: the right end of the oil core (1) is provided with a protruding part (1a), the left end face of the rotational flow core (3) is recessed rightwards to form an accommodating part, the protruding part (1a) penetrates into the accommodating part, and a sealing ring (4) is arranged between the protruding part (1a) and the accommodating part.
4. The high altitude type fuel oil burner with high ejection smoke of claim 1, characterized in that: the combustion cylinder (300) is mainly formed by sequentially integrating a first cylindrical cylinder part (3-1), an inwards concave curve-shaped cylinder part (3-2), a conical cylinder part (3-3) and a second cylindrical cylinder part (3-4) from left to right, and a plurality of injection grooves are formed in the conical cylinder part (3-3).
5. The high altitude type fuel oil burner with high ejection smoke of claim 1, characterized in that: the external diameter of the lower end of the flame stabilizing disc (200) is 97mm, the external diameter of the upper end is 110mm, the thickness is 3.5mm, the external diameter of the central hole of the flame stabilizing disc is 29mm, the thickness is 1.5mm, the blades of the flame stabilizing disc (200) are straight blades with equal width, the thickness of each blade is 1mm, the diameter of the root circle is 29mm, the diameter of the top circle is 90mm, the number of the blades is 12, the width of the top of each blade is 9mm, the width of the root of each blade is 2.5mm, and the height of the central hole of the flame stabilizing disc (200) is 3.5 mm.
6. The high altitude type fuel oil burner with high ejection smoke of claim 1 or 5, characterized in that: the blade inclination angle of the flame stabilizing disc (200) is 35 degrees.
7. The high altitude type fuel oil burner with high ejection smoke of claim 6, characterized in that: the width of the injection groove is 11.5mm, and the height of the injection groove is 17 mm.
8. A method for manufacturing the high altitude type fuel burner as claimed in any one of claims 1 to 4, comprising:
a1, designing a flame stabilizing disc, wherein the designing of the flame stabilizing disc comprises the following steps:
s1) disc sizing
Determining the size range of the flame stabilizing disc according to the power of the combustor and the size of the combustion cylinder; performing tests to determine the optimal size;
s2) blade design
The arc length S of the blade covered on the root circle on the expansion diagram of the outer circle of the impellerxLength S between outlets of arc length between two adjacent blade rootsjThe ratio, defined as the degree of coverage k of the axial blades, i.e. having
The covering degree is 1.1-1.5, the larger the covering degree is, the stronger the swirling action of the airflow field is, but after the covering degree exceeds a certain limit, the flow resistance of the swirling vanes is too large, and the swirling strength is not changed obviously;
s3) center hole design
S4) calculating the swirl strength of the flame stabilizing disc
The following formula is used for calculation:
in the formula: r isoIs the outer diameter of the blade, riIs the inner diameter of the blade, beta is the blade angle, Z is the number of blades, eta is the phaseThe distance between the outlets of two adjacent blades is as follows:
in the formula: delta is the blade thickness;
the swirl strength S is gradually reduced along with the increase of the inclination angle of the blade;
s5) calculating the resistance of flame stabilizing disc
As can be seen from the formula (3), the swirl strength S increases with the decrease of the blade inclination angle beta, but when the blade angle beta is less than or equal to 45 degrees, the flow resistance increases, so the influence of the flow resistance is considered in the design calculation;
for axial vane cyclones in which the vane type is straight, at Re>1×105Under the conditions, the drag coefficient ξ may be calculated as:
ξ＝2.5S (4)
therefore, for the structure of the swirl vane type flame stabilizing disc, the resistance coefficient and the swirl strength are in direct proportion;
performing cold state research on airflow fields of flame stabilizing disks with different blade inclination angles by adopting a numerical simulation method, and selecting the blade inclination angle;
a2, designing a combustion can, the designing the combustion can comprising:
carrying out improved design on the basis of the reducing sectional type combustion cylinder, taking injection performance and an airflow flow field structure into consideration, improving the structure size of an injection groove by using a numerical calculation method, determining the relation between the opening width w of the injection groove and injection quantity, and selecting the opening width w of the injection groove; determining the relation between the height h of the injection groove and the injection amount, and selecting the height h of the injection groove; in order to enhance the injection effect, the Venturi type and jar type combustion cylinder structures are designed on the basis of the reducing sectional type combustion cylinder according to the principle that the diagonal of the groove is equal to the original structure, and the type of the combustion cylinder is selected according to the reflux quantity and the flame stabilizing effect.
Technical Field
The invention relates to the technical field of combustion equipment, in particular to a plateau type fuel oil burner with high injection smoke and a design method.
Background
The environmental parameters of plateau alpine regions are changed greatly, the oxygen content is low, the temperature is low, the air pressure is low, and the air supply quantity of a fan is not enough, so that the problems of difficult ignition, reduced combustion power and efficiency, high pollution emission and the like of a common burner can be caused. Even if the air quantity can meet the air-fuel ratio requirement, most plain burners cannot realize high-efficiency clean combustion in the plateau environment in view of the increasingly severe environmental protection requirement of China at present.
Most of the existing commercial burner nozzles are pure pressure atomization type or double-fluid nozzles, good atomization of oil products cannot be guaranteed by adopting the pure pressure atomization nozzles in plateau alpine environments, most of the existing double-fluid nozzles promote fuel atomization through high-pressure gas, but sometimes the plateau alpine environments are not easy to have high-pressure conditions, the auxiliary atomization gas pressure in the scheme is far lower than the fuel pressure, and therefore a new two-phase flow nozzle needs to be designed for enhancing the atomization effect.
The combustion cylinder of the existing burner is in a short cylindrical shape, the wall surface is not provided with holes (except a plurality of mounting hole grooves), the effects of mounting a flame stabilizing disc and guiding flow are achieved, and high-temperature flue gas backflow cannot be ejected structurally.
Disclosure of Invention
The invention aims to solve the problems and provides a high-altitude fuel oil burner with high injection smoke and a design method thereof, wherein the high-altitude fuel oil burner is provided with a low-pressure air auxiliary atomizing nozzle, so that the problem of poor atomizing effect of a mechanical atomizing nozzle in a high and cold plateau environment is solved; the high-temperature flue gas self-circulation technology is adopted to design a combustion cylinder structure so as to realize high flue gas circulation rate of the combustion chamber and solve the problem of high combustion pollution emission; stabilizing flame by adopting a blade type rotational flow flame stabilizing disc with smaller flow resistance; the heat storage material is adopted to strengthen the fuel oil combustion, so that the combustion efficiency is improved; the technical scheme is as follows:
the utility model provides a plateau type fuel oil burner with high flue gas that draws, its characterized in that includes: the combustion device comprises an atomizing nozzle, a flame stabilizing disc, a combustion barrel and a combustion cavity, wherein the atomizing nozzle is positioned in the middle of the flame stabilizing disc, the combustion barrel is sleeved on the outer side of the flame stabilizing disc, the combustion barrel is arranged in the combustion cavity, and a heat storage material is laid on the inner side of the combustion cavity.
On the basis of the technical scheme, the atomizing nozzle comprises an oil core, a rotational flow core and a shell, wherein the oil core is in threaded connection with the shell, an oil through cavity is formed in the center of the oil core, an air inlet hole is formed in the shell, the oil core is positioned in the shell, an air vent cavity is formed between the outer wall of the oil core and the inner wall of the shell in a surrounding manner, the rotational flow core is connected to the right end of the oil core and positioned in the shell, a pressurizing oil through cavity communicated with the oil through cavity of the oil core is formed in the center of the rotational flow core, the right end face of the rotational flow core is a conical surface, a plurality of rotational flow grooves communicated with the air vent cavity are formed in the right end face of the rotational flow core, a conical oil hole communicated with the pressurizing oil through cavity is formed in the right end of the rotational flow core, a conical spray hole is formed in the right end of the shell, the rotational flow groove and the left end of the conical, and a taper hole bus of the taper oil hole is a Wittonsisky curve.
On the basis of the technical scheme, the right end of the oil core is provided with a protruding part, the left end face of the rotational flow core is recessed rightwards to form an accommodating part, the protruding part penetrates into the accommodating part, and a sealing ring is arranged between the protruding part and the accommodating part.
On the basis of the technical scheme, the combustion cylinder mainly comprises a first cylindrical cylinder part, an inwards concave curve cylinder part, a conical cylinder part and a second cylindrical cylinder part which are sequentially and integrally formed from left to right, and the conical cylinder part is provided with a plurality of injection grooves.
On the basis of the technical scheme, the blade inclination angle of the blades of the flame stabilizing disc is 35 degrees.
On the basis of the technical scheme, the width of the injection groove is 11.5mm, and the height of the injection groove is 17 mm.
A method of manufacturing the above-described high-altitude type fuel burner, comprising:
a1, designing a flame stabilizing disc, wherein the designing of the flame stabilizing disc comprises the following steps:
s1) disc sizing
Determining the size range of the flame stabilizing disc according to the power of the combustor and the size of the combustion cylinder; performing tests to determine the optimal size;
s2) blade design
The arc length S of the blade covered on the root circle on the expansion diagram of the outer circle of the impellerxLength S between outlets of arc length between two adjacent blade rootsjThe ratio, defined as the degree of coverage k of the axial blades, i.e. having
The covering degree is 1.1-1.5, the larger the covering degree is, the stronger the swirling action of the airflow field is, but after the covering degree exceeds a certain limit, the flow resistance of the swirling vanes is too large, and the swirling strength is not changed obviously;
s3) center hole design
S4) calculating the swirl strength of the flame stabilizing disc
The following formula is used for calculation:
in the formula: r isoIs the outer diameter of the blade, riThe inner diameter of each blade, beta is the inclination angle of each blade, Z is the number of the blades, and eta is the distance between the outlets of the two adjacent blades:
in formula (3): delta is the blade thickness;
the swirl strength S is gradually reduced along with the increase of the inclination angle of the blade;
s5) calculating the resistance of flame stabilizing disc
As can be seen from the formula (3), the swirl strength S increases with the decrease of the blade inclination angle beta, but when the blade angle beta is less than or equal to 45 degrees, the flow resistance increases, so the influence of the flow resistance is considered in the design calculation;
for axial vane cyclones in which the vane type is straight, at Re>1×105Under the conditions, the drag coefficient ξ may be calculated as:
ξ＝2.5S (4)
therefore, for the structure of the swirl vane type flame stabilizing disc, the resistance coefficient and the swirl strength are in direct proportion;
performing cold state research on air flow fields of flame stabilizing disks with different blade inclination angles by adopting a numerical simulation method, and selecting the blade inclination angles;
a2, designing a combustion can, the designing the combustion can comprising:
the method comprises the steps of performing improved design on the basis of the reducing sectional type combustion cylinder, considering injection performance and an air flow field structure, improving the structure size of an injection groove by using a numerical calculation method, and selecting the opening width w of the injection groove by determining the relation between the opening width w of the injection groove and injection quantity; selecting the height h of the injection groove by determining the relation between the height h of the injection groove and the injection amount; in order to enhance the injection effect, the Venturi type and jar type combustion cylinder structures are designed on the basis of the reducing sectional type combustion cylinder according to the principle that the diagonal of the groove is equal to the original structure, and the type of the combustion cylinder is selected according to the reflux quantity and the flame stabilizing effect.
The invention has the beneficial effects that:
energy conservation and emission reduction beneficial to realizing plateau environment
And secondly, the fuel atomization quality in the alpine environment in the plateau is improved by adopting air-assisted atomization, and the fuel is fully contacted with the air, so that ignition and full combustion are facilitated.
Thirdly, flue gas recirculation technology is adopted to realize flue gas circulation of a combustion space, high-temperature flue gas is mixed with fresh fuel and combustion air to bring heat, local reaction speed is reduced, combustion temperature peak value is reduced, and thermal NO is reducedxIs generated in large quantities.
Fourthly, the heat accumulation combustion technology is adopted to strengthen the combustion reaction and convert the incomplete combustion component CO into CO2The combustion can be stably and completely carried out under different regional conditions, and the combustion efficiency is improved.
Drawings
FIG. 1 is a schematic sectional view of a plateau type oil burner with high injection smoke according to the present invention;
FIG. 2 is a schematic cross-sectional view of an atomizing nozzle according to the present invention;
FIG. 3 is a schematic cross-sectional structure diagram of a flame stabilizing disc according to the present invention;
FIG. 4 is a schematic view of the configuration of the combustion can of the present invention (with airflow direction);
FIG. 5 is a schematic structural view of a variable diameter segmented combustor can;
FIG. 6 is a drawing of a jet nozzle;
FIG. 7 is a 35 blade pitch axial velocity cloud;
FIG. 8 is a relationship between the width of the injection groove and the injection coefficient;
FIG. 9 is a relationship between the height of the injection groove and the injection coefficient
FIG. 10(a, b, c) is a schematic structural diagram of three types of combustion cylinders, namely a curved type combustion cylinder, a straight conical type combustion cylinder and a jar type combustion cylinder, which are sequentially arranged;
FIG. 11(a, b, c) is a velocity vector diagram of symmetrical planes of the structure of three types of combustion cylinders, namely a curved type combustion cylinder, a straight cone type combustion cylinder and a jar type combustion cylinder in sequence;
FIG. 12(a, b, c) is a pressure distribution cloud chart sequentially showing symmetrical planes of three types of combustion cylinders, namely a curved type combustion cylinder, a straight conical type combustion cylinder and a jar type combustion cylinder;
Detailed Description
The invention is further illustrated by the following examples in conjunction with the accompanying drawings:
in the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the description of the present invention, it is to be understood that the terms "left", "right", "front", "back", "top", "bottom", "inner", "outer", etc., indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.
As shown in fig. 1 to 4, a high altitude type fuel oil burner with high injection smoke is characterized by comprising: the atomizing nozzle 100 is positioned in the middle of the flame stabilizing disc 200, the combustion cylinder 300 is sleeved outside the flame stabilizing disc 200, the combustion cylinder 300 is arranged in the combustion chamber 400, and the heat storage material 500 is paved on the inner side of the combustion chamber 400.
Preferably, the atomizing nozzle 100 includes an oil core 1, a rotational flow core 3 and a housing 2, the oil core 1 is in threaded connection with the housing 2, an oil through cavity 8a is formed in the center of the oil core 1, an air inlet hole 9 is formed in the housing 2, the oil core 1 is located in the housing 2, an air through cavity 9a is enclosed between the outer wall of the oil core 1 and the inner wall of the housing 2, the rotational flow core 3 is connected to the right end of the oil core 1 and located in the housing 2, a pressurizing oil through cavity 8b communicated with the oil through cavity 8a of the oil core 1 is formed in the center of the rotational flow core 3, the right end surface of the rotational flow core 3 is a conical surface, a plurality of rotational flow grooves 5 communicated with the air through cavity 9a are formed in the right end surface of the rotational flow core 3, a conical oil hole 8c communicated with the pressurizing oil through cavity 8b is formed in the right end of the rotational flow core 3, a conical spray hole, the right end of the conical oil hole 8c, the swirl groove 5 and the left end of the conical spray hole 2a are mutually converged, the conical oil hole 8c and the conical spray hole 2a form a Laval spray pipe, and a generatrix of the conical oil hole 8c is a Wittonsisky curve. The whole Laval nozzle is depressurized and accelerated, the atomization effect of fuel oil is enhanced, and high-temperature flue gas circulation is easily injected in a low-pressure area. As shown in figure 2, the atomizing nozzle 100 adopts partial combustion air to assist fuel atomization, the oil communicating cavity 8a is used for conveying fuel oil, the air inlet hole 9 is used for air inlet, the air communicating cavity 9a is used for conveying air, the air is provided by a low-pressure air pump, the total amount is small, then the air flows through the rotary flow groove 5 to reach the conical oil hole 8c and is merged with the fuel oil sprayed out of the conical oil hole 8c, and then the air is sprayed out from the conical spray hole 2a together, so that the mixing of oil mist and air is enhanced, and the fuel oil atomizing effect.
Preferably, the right end of the oil core 1 has a protrusion 1a, the left end surface of the cyclone core 3 is recessed rightward to form an accommodating portion, the protrusion 1a penetrates into the accommodating portion, and a sealing ring 4 is disposed between the protrusion 1a and the accommodating portion. The oil core 1 and the rotational flow core 3 are convenient to be installed in a centering mode through a concave-convex ring groove structure, and the sealing ring 4 can prevent oil and gas from being mixed in advance to cause oil to flow back into the gas.
Preferably, the combustion cylinder 300 is mainly formed by sequentially integrating a first cylindrical cylinder part 3-1, an inwards concave curve-shaped cylinder part 3-2, a conical cylinder part 3-3 and a second cylindrical cylinder part 3-4 from left to right, and the conical cylinder part 3-3 is provided with a plurality of injection grooves.
Optionally, the outer diameter of the lower end of the flame stabilizing disc 200 is 97mm, the outer diameter of the upper end is 110mm, the thickness is 3.5mm, the outer diameter of the central hole of the flame stabilizing disc is 29mm, the thickness is 1.5mm, the blades of the flame stabilizing disc 200 are straight blades with equal width, the thickness of each blade is 1mm, the diameter of the root circle is 29mm, the diameter of the top circle is 90mm, the number of the blades is 12, the width of the top of each blade is 9mm, the width of the root of each blade is 2.5mm, and the height of the central hole of the flame stabilizing disc 200 is 3.5 mm.
Optionally, the blade angle of the blades of the flame stabilizing disc 200 is 35 °.
Optionally, the width of the injection groove is 11.5mm, and the height of the injection groove is 17 mm.
A method of manufacturing the above-described high-altitude type fuel burner, comprising:
a1, designing a flame stabilizing disc, wherein the designing of the flame stabilizing disc comprises the following steps:
s1) disc sizing
Determining the size range of the flame stabilizing disc according to the power of the combustor and the size of the combustion cylinder; designing a test, and researching how changes of key sizes and structures affect an airflow field and a combustion condition; determining the optimal size and structure;
s2) blade design
The arc length S of the blade covered on the root circle on the expansion diagram of the outer circle of the impellerxLength S between outlets of arc length between two adjacent blade rootsjThe ratio, defined as the degree of coverage k of the axial blades, i.e. having
The coverage is usually 1.1-1.5. The larger the covering degree is, the stronger the swirling action of the airflow field is. When the covering degree exceeds a certain limit, the flow resistance of the swirl blades is overlarge, the swirl strength is not obviously changed, and the number of the blades is not less than 4, generally 6-12 according to the related requirements of the covering degree;
for the straight blade with the same width, the thickness of the blade is 1mm, the diameter of the root circle is 29mm, the diameter of the top circle is 90mm, and then the diameter d of the root circleiDiameter d of the tip circleoThe ratio of (A) to (B) is 0.31. In order to obtain larger swirl strength, the number of the blades is 12. The covering degree k of the blades is 1.1-1.5.
Sj＝(π*d-12*3)÷12＝(3.14*29-12*3)÷12＝4.33
Namely, the projection arc length range of the blade on the root circle is 4.76-6.5 mm.
For the blades with the same width, because the inner and outer circumferences of the impeller are different, the distance between adjacent blades is larger along the height of the blades, and the distance between blade roots is smaller than the blade tops, so that the gas flow resistance root is larger than the top, the flow distribution top is larger than the root, and the flow distribution is extremely uneven. The condition is improved by adopting the blades with different widths, so that the outlet flow velocity is uniform, and the airflow resistance is small.
And carrying out design calculation on the unequal-width blades based on a structural design method of the equal-width blades.
The width of the top of the blade with different widths is usually (0.2-0.4) do. For the flow field of the coaxial rotating jet flow of the fuel oil burner, the covering degree of the blades is reduced as much as possible to ensure that enough airflow flows through the swirl blades, as shown in fig. 7, the width of the top of the blades is 9mm under the condition of 35-degree blade inclination angle through early-stage numerical calculation, so that enough swirl airflow can be ensured, and the combustion condition is met.
S3) center hole design
For the determination principle of the height of the center ring, consideration needs to be given to avoiding the occurrence of the phenomenon that fuel collides with the wall.
The critical height to avoid fuel impingement on the central orifice of the wall is 5.0mm when considering the maximum spray cone angle of 90. The height of the center hole was designed to be 3.5 mm.
The width of the blade root is taken to be 2.5mm, taking into account the actual height of the central hole.
S4) calculating the swirl strength of the flame stabilizing disc
The following formula is used for calculation:
in the formula: r isoIs the outer diameter of the blade, riThe inner diameter of each blade, beta is the inclination angle of each blade, Z is the number of the blades, and eta is the distance between the outlets of the two adjacent blades:
in the formula: delta is the blade thickness;
the swirl strength S is gradually reduced along with the increase of the inclination angle of the blade;
s5) calculating the resistance of flame stabilizing disc
As can be seen from the formula (3), the swirl strength S increases with the decrease of the blade inclination angle beta, but when the blade angle beta is less than or equal to 45 degrees, the flow resistance increases, so the influence of the flow resistance is considered in the design calculation;
for axial vane cyclones in which the vane type is straight, at Re>1×105Under the conditions, the drag coefficient ξ may be calculated as:
ξ＝2.5S (4)
therefore, for the structure of the swirl vane type flame stabilizing disc, the resistance coefficient and the swirl strength are in direct proportion;
the numerical simulation method is adopted to carry out cold state research on the air flow fields of the flame stabilizing discs with different blade inclination angles, and numerical calculation finds that the cyclone air quantity of the cyclone blade type flame stabilizing disc with the 35-degree blade inclination angle is larger, the proportion of central air to edge air is smaller, the cyclone is favorable for forming a backflow area, a high-temperature ignition source is formed, and the whole combustion field is more stable and uniform.
In order to improve the flow field of the mixing area, promote the circulation of partial flue gas, properly reduce the oxygen concentration in reactants, eliminate a local high-temperature area and reduce NOxThe combustion cylinder is designed into a structural form capable of achieving a smoke self-circulation effect by means of injection, and an injection groove is formed, so that a part of high-temperature smoke flows back to the inside, mixing of fuel oil and air is accelerated, and evaporation rate of the fuel oil is accelerated.
A2, designing a combustion can, the designing the combustion can comprising:
the design principle of the ejector and the actual structures of the combustor and the hearth are referenced to carry out the primary design of the ejection structure, the high-temperature flue gas is sucked by the ejection effect of the edge direct-current wind, the influence of rotational flow air is not considered, and the analysis is carried out according to the one-dimensional control method. As shown in fig. 6, the characteristic equation of the ejector is:
in the formula, pressure p2For mixing tube outlet pressure, psInjecting the pressure of the flue gas; flow rate of fluid
Studies have shown that factors that can affect ejector mixers include:
(1) the effect of primary to secondary stream temperature ratio;
(2) the effect of the area of the cross-section of the mixing tube and the cross-sectional area of the nozzle outlet;
(3) influence of mixing nonuniformity of the primary flow and the secondary flow in the mixing pipe.
The design is mainly performed by considering the (2) th structural factor.
The pumping performance of the injection structure is mainly related to the distribution characteristics of the free mixing layer. While the distribution of the free mixing layer is related to the ratio L/delta between the mixing gap and the mixing tube length. Under the condition that the length of the mixing pipe and the diameter of the main pipe are determined, the influence of the change of the mixing gap delta on the injection performance and the air flow field is researched, and the method has important significance.
As shown in FIG. 5, the burner is improved based on a reducing sectional type burner, and the main purpose is to determine the size of an injection slot. The lower section is used for guiding and installing a flame stabilizing disc, the structural size of the flame stabilizing disc is designed according to the structure of the original combustor, the inner diameter is 120mm, and the height is 43 mm. The middle part is provided with an injection groove, the topmost end is provided with a diffusion section with the height of 37mm and the diameter of 168mm at the topmost end. Under the injection and entrainment action of air intermediate flow, especially edge direct flow, in the combustion cylinder, smoke outside the combustion cylinder is entrained and absorbed into the combustion cylinder through the injection groove to be mixed with fuel and air. Through changing the parameter of drawing the groove, can control the backward flow volume of flue gas. Wherein the width w of the injection groove is the mixing gap delta.
1) Determining the relation between the opening width w of the injection groove and the injection amount
The height h of the slot is set to be 15mm, the inclination angle of the cyclone blade of 35 degrees is selected, and the influence condition of the change of the slot width w on the flow field is researched. The calculation results are shown in table 1. Wherein the injection coefficient epsilon is injection air quantity/total air quantity.
TABLE 1 calculation results of different injection groove widths
As shown in fig. 8, the relationship between the width of the injection groove and the injection coefficient is shown, and the injection amount and the injection coefficient tend to increase first and then decrease as w gradually increases.
In the range that the width of the injection groove is small, the injection coefficient can be increased along with the increase of the width of the injection groove. However, because the total air quantity of the inlet is fixed, the ejection power of the edge direct-current air has a certain limit, and when the width of the ejection slot is too large, the ejection power is not enough to match the slot width, so that the ejection coefficient is reduced. Therefore, the injection coefficient has a maximum value along with the change of the groove width. When the width of the injection groove is set, the size of the injection amount is considered, and the groove width with the large injection amount is comprehensively selected. The width of the injection groove is 11.5 mm.
2) Determining the relation between the height h of the injection groove and the injection amount
The width w of the slot is set to be 11.5mm, the inclination angle of the swirl vane of 35 degrees is selected, and the influence of the change of the slot height h on the airflow field is researched. The results of the study are shown in table 2 and fig. 9.
TABLE 2 calculation results of different injection groove heights
According to fig. 9, the injection coefficient shows a tendency of increasing first and then becoming gentle as the height of the injection groove increases. The injection coefficient can be improved by increasing the height of the injection groove.
If peripheral high-temperature oxygen is injected to a position as close to the root of the flame as possible, the high-temperature flue gas, combustion air and fuel oil mist can be well mixed at the initial stage. Therefore, the height of the injection groove is not too high, and the minimum height meeting the injection requirement is required.
According to the calculation, the performance of the combustion cylinder is best when the width of the injection groove is 11.5mm and the height of the injection groove is 17mm under the structural form of the current combustion cylinder.
(2) Improved structure of combustion cylinder
In order to enhance the injection effect, on the basis of the primary improved structure, the Venturi type and jar type combustion cylinder structures are designed according to the principle that the diagonal line of the groove is equal to the original structure, and are respectively divided into conical combustion cylinders and curved combustion cylinders according to the shapes of the contraction sections as shown in fig. 10(a, b and c).
The gas reflux quantity is mainly related to structural parameters and is not greatly related to gas temperature, cold flow analysis is independently carried out on the three combustion cylinder structures to obtain a graph 11, and air supply at the flame stabilizing disc is divided into a central air zone, a rotational flow air zone and an edge air zone according to the inlet conditions. From fig. 11, it can be seen that the air flow passes through the injection groove obviously, and in combination with fig. 12, it can be seen that each structure has a low-pressure area at the downstream of the inner side of the injection groove, which is beneficial to the introduction of the air flow outside the combustion cylinder into the cylinder; and an obvious three-dimensional rotational flow is arranged at the downstream of the flame stabilizing disc.
The high temperature gas reflux for the three configurations were compared and found to be in table 3. Comparing the three groups of data shows that the backflow amount of the curved combustion cylinder is maximum; the temperature has little influence on the injection reflux amount of the high-temperature flue gas. The curved combustion cylinder structure is determined as the most suitable structure.
TABLE 3 gas recirculation data for different combustion can configurations
While there have been shown and described what are at present considered the fundamental principles and essential features of the invention and its advantages, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing exemplary embodiments, but is capable of other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
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