CN114623443B - Sectional type porous medium burner and working method thereof - Google Patents
Sectional type porous medium burner and working method thereof Download PDFInfo
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- CN114623443B CN114623443B CN202210375431.0A CN202210375431A CN114623443B CN 114623443 B CN114623443 B CN 114623443B CN 202210375431 A CN202210375431 A CN 202210375431A CN 114623443 B CN114623443 B CN 114623443B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/02—Premix gas burners, i.e. in which gaseous fuel is mixed with combustion air upstream of the combustion zone
- F23D14/04—Premix gas burners, i.e. in which gaseous fuel is mixed with combustion air upstream of the combustion zone induction type, e.g. Bunsen burner
- F23D14/08—Premix gas burners, i.e. in which gaseous fuel is mixed with combustion air upstream of the combustion zone induction type, e.g. Bunsen burner with axial outlets at the burner head
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D11/00—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space
- F23D11/10—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space the spraying being induced by a gaseous medium, e.g. water vapour
- F23D11/22—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space the spraying being induced by a gaseous medium, e.g. water vapour the gaseous medium being vaporised fuel, e.g. for a soldering lamp, or other gaseous fuel
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D11/00—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space
- F23D11/36—Details, e.g. burner cooling means, noise reduction means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D11/00—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space
- F23D11/36—Details, e.g. burner cooling means, noise reduction means
- F23D11/40—Mixing tubes or chambers; Burner heads
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D11/00—Burners using a direct spraying action of liquid droplets or vaporised liquid into the combustion space
- F23D11/36—Details, e.g. burner cooling means, noise reduction means
- F23D11/44—Preheating devices; Vaporising devices
- F23D11/441—Vaporising devices incorporated with burners
- F23D11/443—Vaporising devices incorporated with burners heated by the main burner flame
- F23D11/445—Vaporising devices incorporated with burners heated by the main burner flame the flame and the vaporiser not coming into direct contact
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/12—Radiant burners
- F23D14/14—Radiant burners using screens or perforated plates
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/46—Details, e.g. noise reduction means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/46—Details, e.g. noise reduction means
- F23D14/62—Mixing devices; Mixing tubes
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/46—Details, e.g. noise reduction means
- F23D14/66—Preheating the combustion air or gas
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/46—Details, e.g. noise reduction means
- F23D14/70—Baffles or like flow-disturbing devices
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D17/00—Burners for combustion conjointly or alternatively of gaseous or liquid or pulverulent fuel
- F23D17/002—Burners for combustion conjointly or alternatively of gaseous or liquid or pulverulent fuel gaseous or liquid fuel
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D2203/00—Gaseous fuel burners
- F23D2203/002—Radiant burner mixing tubes
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D2203/00—Gaseous fuel burners
- F23D2203/10—Flame diffusing means
- F23D2203/105—Porous plates
- F23D2203/1055—Porous plates with a specific void range
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
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Abstract
The invention discloses a sectional type porous medium burner and a working method thereof, belonging to the technical field of household burners. The burner comprises a burner shell, wherein a premixing cavity and a contraction section are respectively arranged at two ends of the burner shell, the premixing cavity is connected with an air inlet pipe, and the contraction section is connected with an air outlet pipe; a tubular heat exchanger group is arranged in the combustor shell close to the contraction section, and a plurality of sections of porous media are filled in the combustor shell close to the premixing cavity in a segmented manner; the pore diameter and the thermal conductivity of a plurality of sections of porous media increase progressively along the direction from the premixing cavity to the contraction section, and no gap exists between adjacent sections of porous media. The invention has compact structure, wide working load adjusting range, low pollutant discharge amount, stable flame surface and difficult backfire and fire dropping, can be applied to a household water heater without limitation, meets the pollutant discharge index of the water heater specified by the state, and particularly meets the NO (NO) discharge index x And CO emission indexes, and realizes high-efficiency and clean utilization of energy.
Description
Technical Field
The invention belongs to the technical field of household burners, and particularly relates to a sectional type porous medium burner and a working method thereof.
Background
At present, a household generally adopts a gas quick water heater, and the water heater adopts a fin structure for heat exchange, and is large in size and heavy. The porous medium combustion technology has the advantages of high combustion rate, low pollutant discharge in flue gas, wide combustion limit, combustible low-heat-value fuel gas and the like, and can obviously reduce NO when being applied to fuel gas equipment x CO emission and widened load regulation range.
CN2484481 discloses a graded porous medium burner, a heat dissipation ring is arranged at one end of a burner shell and a heat insulation layer thereof, and graded porosity non-uniform porous media are arranged in a secondary air peclet ring. CN102937292 discloses a periodically reversing immersion flame porous medium burner, which adopts different porous media to periodically combine, so that the burner can work in a very large power range and a half period. However, the porous materials of the existing porous medium burner have the safety problems of no high temperature resistance, poor thermal shock resistance, low strength, easy adhesion, unstable flame surface and easy occurrence of backfire and deflagration. In addition, the two types of combustors only have one combustion area, and have the defects of unsegmented combustion process, incomplete combustion and the like.
Disclosure of Invention
In order to solve the above problems, the present invention aims to provide a sectional porous medium burner and a working method thereof, which have the advantages of compact structure, wide adjustment range of working load, low pollutant discharge amount, stable flame surface, difficult backfire and misfire, and realization of efficient and clean utilization of energy.
The invention is realized by the following technical scheme:
the invention discloses a sectional type porous medium burner which comprises a burner shell, wherein a premixing cavity and a contraction section are respectively arranged at two ends of the burner shell, the premixing cavity is connected with an air inlet pipe, and the contraction section is connected with an air outlet pipe; a tubular heat exchanger group is arranged in the combustor shell close to the contraction section, and a plurality of sections of porous media are filled in sections close to the premixing cavity; the pore diameter and the thermal conductivity of a plurality of sections of porous media are gradually increased along the direction from the premixing cavity to the contraction section, and no gap exists between adjacent sections of porous media.
Preferably, the porous medium comprises a first section of porous medium, a second section of porous medium and a third section of porous medium with the thickness ratio of (1-2): 0-2, the pore density of the first section of porous medium is 40-100 PPI, the pore density of the second section of porous medium is 20-70 PPI, and the pore density of the third section of porous medium is 5-40 PPI.
Further preferably, the first section of porous medium, the second section of porous medium and the third section of porous medium each comprise a plurality of layers having different pore densities and thermal conductivities.
Further preferably, when the flame propagation speed of the fuel is lower than 0.3m/s, the thickness ratio of the first-stage porous medium, the second-stage porous medium and the third-stage porous medium is 2; when the flame propagation speed of the fuel is 0.3-0.5 m/s, the thickness ratio of the first section of porous medium, the second section of porous medium and the third section of porous medium is 1; when the flame propagation speed of the fuel is more than 0.5m/s, the thickness ratio of the first section of porous medium, the second section of porous medium and the third section of porous medium is 2.
Further preferably, when the fuel is liquid fuel or gas-liquid mixed fuel, an atomizing nozzle is arranged in the air inlet pipe.
Further preferably, the thermal conductivity of the first-stage porous medium is 0.6-2.2W/(m.K), the thermal conductivity of the second-stage porous medium is 5.2-12W/(m.K), and the thermal conductivity of the third-stage porous medium is 20-50W/(m.K).
Further preferably, the material of the section of porous medium is alumina, aluminum titanate, cordierite or quartz ceramic; the second-stage porous medium is made of mullite, nickel-based alloy, nickel-chromium-iron alloy or porous tungsten; the three sections of porous media are made of silicon carbide, silicon nitride or zirconium oxide.
Preferably, the total thickness of the porous medium is 0.3 to 0.6 times the height of the combustion chamber.
Preferably, along the direction from the air inlet pipe to the air outlet pipe, the sectional area of the premixing cavity is gradually expanded, and the sectional area of the contraction section is gradually reduced.
The invention discloses a working method of the sectional type porous medium combustor, which comprises the following steps:
combustible gas and air enter from the air inlet pipe and then are fully disturbed and mixed in the premixing cavity, then enter a plurality of sections of porous media, are firstly decelerated by the pore structures in the porous media and are further uniformly mixed, and meanwhile, heat transmitted from the rear section of porous media in radiation and heat conduction modes is absorbed in the front section of porous media to preheat and heat up; after being fully preheated, the mixture continuously flows along the inside of the porous medium to carry out super-enthalpy combustion to form flue gas; the heat of the flue gas is rapidly transferred to the porous medium of the adjacent section through solid heat conduction and radiation, and the combustor maintains thermal NO in the combustion process x Low emission of (2); the smoke and part of residual combustible gas are burnt out in the porous medium at the tail section, part of heat released by the smoke is taken away by the smoke, part of heat is transmitted to the tail flue in a radiation mode, and part of heat is transmitted to the porous medium through heat conduction and radiation; because the pore diameters and the pore numbers of a plurality of sections of porous media are different, the propagation of the flame surface is blocked, and the flame surface can be stabilized between the adjacent sections of porous media; the flue gas flows through the tubular heat exchanger group of the tail flue after passing through the porous medium to carry out convection heat exchange, cold water flows in the tube and absorbs heat to raise the temperature, and the generated hot water is output to the combustor.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention discloses a sectional type porous medium burner, wherein a burning part is filled with a sectional pore size-variable porous medium, fuel is fully preheated and diffused in an upstream area to realize super-enthalpy combustion in a midstream area, and simultaneously heat is rapidly transferred to an upstream preheating area and a downstream burnout area, so that the condition that a large amount of NO is generated due to overhigh temperature is avoided x Finally, the residual CO is fully reacted in the downstream area; meanwhile, the fuel can be preheated, rather than the heat is dissipated to the surrounding wall surface or air, so that the heat storage capacity is high, the combustion temperature can not exceed 1200 ℃, and NO is further added x The total emission is reduced to 30mg (kW.h), and low-nitrogen combustion is really realized. The combustion temperature of the existing rapid gas equipment and single-layer porous medium gas equipment is up to 1600 ℃, a large amount of thermal NOx can be generated, and the thermal NOx can generally reach 150-200 ppm. The prior art also has the defects of uneven diffusion of premixed gas and fuel and O on a free flame surface 2 Insufficient contact and high CO discharge. In the invention, the flow velocity of the premixed gas is reduced in the front-stage porous medium, the premixed gas is fully diffused and mixed, and is preheated by high temperature (compared with cold inlet gas) at the same time, and then the super-enthalpy combustion is realized in the rear-stage porous medium. The premixed gas is fully combusted in the porous medium, so that the total emission of CO can be as low as 0.02 percent (alpha = 1), which is obviously lower than the national pollutant emission standard, and low CO combustion is realized. The current porous medium gas equipment has a single-layer structure, a flame surface is unstable, and tempering and fire dropping phenomena are easy to occur, so that the equipment is very dangerous. In the invention, the front section is made of porous material with small aperture and low thermal conductivity, the holes are densely distributed, the flow resistance is large, and the heat transmitted from the rear section through heat conduction and radiation can be obviously reduced, thereby preventing tempering. The rear section is made of porous material with larger aperture and higher thermal conductivity, and the flame can be stabilized between the two sections of porous media due to the action of a resistance force when the flame is transmitted between the two sections of porous media, so that the occurrence of fire escape can be effectively prevented. Finally, the segmented variable-aperture structure has the characteristic of good organization combustion, and the premixed gas can be stably combusted under the working conditions of lean fuel and rich fuel, so that the working load adjusting range is wide and can reach 1.
Further, when the flame propagation speed of the gas fuel is lower than 0.3m/s, the thickness ratio of the first section of porous medium, the second section of porous medium and the third section of porous medium is 2; when the flame propagation speed of the gas fuel is 0.3-0.5 m/s, the thickness ratio of the first section of porous medium, the second section of porous medium and the third section of porous medium is 1; when the flame propagation speed of gas, liquid and gas-liquid mixed fuel is greater than 0.5m/s, the thickness ratio of the first section of porous medium, the second section of porous medium and the third section of porous medium is 2.
The working method of the sectional type porous medium burner disclosed by the invention has the advantages of wide working load adjusting range, low pollutant discharge amount, stable flame surface and difficulty in tempering and fire dropping, and realizes high-efficiency and clean utilization of energy.
Drawings
FIG. 1 is a schematic view of the overall structure of the present invention;
FIG. 2 is a schematic view of the entire structure of embodiment 1;
FIG. 3 is a schematic view of the entire structure of embodiment 2;
fig. 4 is a schematic view of the entire structure of embodiment 3.
In the figure: the device comprises a gas inlet pipe 1, a premixing cavity 2, a combustor shell 3, a first section of porous medium 4, a second section of porous medium 5, a third section of porous medium 6, a tubular heat exchanger group 7, a contraction section 8 and a gas outlet pipe 9.
Detailed Description
The invention will now be described in further detail with reference to the following figures and examples, which are intended to illustrate and not to limit the invention:
referring to fig. 1, the sectional type porous medium burner of the present invention comprises a burner housing 3, wherein a premixing cavity 2 and a contraction section 8 are respectively arranged at two ends of the burner housing 3, the premixing cavity 2 is connected with an air inlet pipe 1, and the contraction section 8 is connected with an air outlet pipe 9; a tubular heat exchanger group 7 is arranged in the combustor shell 3 close to the contraction section, and a plurality of sections of porous media are filled in sections close to the premixing cavity 2; the pore diameter and the thermal conductivity of a plurality of sections of porous media increase progressively along the direction from the premixing cavity 2 to the contraction section 8, and no gap exists between adjacent sections of porous media.
Preferably, the porous medium includes a first-stage porous medium 4, a second-stage porous medium 5, and a third-stage porous medium 6 having a thickness ratio of (1-2): 0-2, the first-stage porous medium 4 having a pore density of 40-100 PPI, the second-stage porous medium 5 having a pore density of 20-70 PPI, and the third-stage porous medium 6 having a pore density of 5-40 PPI.
Further preferably, the first section of porous medium 4, the second section of porous medium 5 and the third section of porous medium 6 each comprise several layers having different pore densities and thermal conductivities.
Further preferably, when the flame propagation speed of the fuel is lower than 0.3m/s, the thickness ratio of the first-stage porous medium 4, the second-stage porous medium 5 and the third-stage porous medium 6 is 2; when the flame propagation speed of the fuel is 0.3-0.5 m/s, the thickness ratio of the first section of porous medium 4, the second section of porous medium 5 and the third section of porous medium 6 is 1; when the flame propagation speed of the fuel is more than 0.5m/s, the thickness ratio of the first section of porous medium 4, the second section of porous medium 5 and the third section of porous medium 6 is 2.
Further preferably, the thermal conductivity of the first-stage porous medium 4 is 0.6-2.2W/(m.K), the thermal conductivity of the second-stage porous medium 5 is 5.2-12W/(m.K), and the thermal conductivity of the third-stage porous medium 6 is 20-50W/(m.K).
Further preferably, the material of the first section of porous medium 4 is alumina, aluminum titanate, cordierite or quartz ceramic; the material of the second-stage porous medium 5 is mullite, nickel-based alloy, nickel-chromium-iron alloy or porous tungsten; the three sections of porous media 6 are made of silicon carbide, silicon nitride or zirconia.
Preferably, the total thickness of the porous medium is 0.3 to 0.6 times the height of the combustion chamber.
Preferably, the cross-sectional area of the premixing chamber 2 is gradually enlarged and the cross-sectional area of the contraction section 8 is gradually reduced along the direction from the inlet pipe 1 to the outlet pipe 9.
Preferably, when the fuel is liquid fuel or gas-liquid mixed fuel, an atomizing nozzle 10 is provided in the intake pipe 1 for atomizing the fuel.
Example 1
The structure of the burner of the present embodiment is shown in fig. 2, natural gas fuel and air enter from the air inlet pipe 1 at the same time, and are fully disturbed and mixed in the premixing cavity 2 after passing through, and then enter into the porous medium of the combustion chamber. The parameters of each section of the porous medium are shown in table 1.
TABLE 1
The pore diameter and the number of pores are expressed as follows.
In the formula (d) m Is the average pore size cm of the porous dielectric material, and the PPI is the number of pores per unit inch of the porous dielectric material/inch;
phi is the porosity of the porous medium material, and the calculation formula is as follows:
φ v ＝V v /V T ×100％
in the formula, V v Is the pore volume, V, in the porous medium material T Is the total volume of the porous medium material.
The first-stage porous medium 4 is made of a porous material with low thermal conductivity and high thermal shock resistance, the second-stage porous medium 5 is made of a porous material with medium thermal conductivity and high temperature resistance, and the third-stage porous medium is designed to be a 0-layer porous medium. The thermal shock resistance and compressive strength are characterized by the following calculation:
R c ＝P/S
σ ft is a porous material with the hard impact strength of MPa and sigma fs The yield strength of the hole wall material is MPa, R c The compressive strength is MPa, P is the breaking load N, and S is the stress area mm of the sample 2 And C is constant and is determined by the density of the hole ribs and the size of the mesh holes.
Specifically, the method comprises the following steps: the section of porous medium 4 is an alumina foam ceramic material with 1 layer, 80PPI hole number, 25W/(m.K) thermal conductivity and 230MPa hard impact strength. The fuel gas is natural gas with flame propagation speed of 0.35-0.5 m/s, the main component is methane (95%), and the fuel gas has the characteristics of high heat value, easy ignition, stable combustion and high flue gas temperature. The gas is decelerated by the pore structure in the section of porous medium 4, is further uniformly mixed, and absorbs heat transferred from the radiation and heat conduction modes of the porous medium to preheat and raise the temperature. After the fuel gas is fully preheated, the fuel gas enters a second-section porous medium 5, the second-section porous medium 5 is a silicon carbide foam ceramic material with 1 layer, 60PPI of pore number, 80W/(m.K) of thermal conductivity and 1600 ℃ of highest available temperature, and the preheated fuel gas realizes super-enthalpy combustion in the second-section porous medium 5 to form flue gas. At the moment, the flame return speed is high, so the first section of the porous medium with the large hole number and the second thermal conductivity can prevent the tempering. The heat of the flue gas is rapidly transferred to the two-section porous medium 5 through solid heat conduction and radiation, and the two-section porous medium is porousThe medium 5 transfers part of heat to the upstream section of porous medium 4 in a solid heat conduction and radiation mode, so that the temperature of a combustion area is reduced, the heat backflow of flue gas is realized, the temperature of a combustor cannot reach very high (obviously lower than 1200 ℃), and the generated thermal NO is x The content is low. Thermal NO x The main component is NO, and according to the quick multi-vitamin reaction mechanism, the reaction formula and the calculation formula are as follows:
wherein [ NO ]]、[N 2 ]、[O 2 ]Are respectively NO and N 2 、O 2 The concentration of (c);
t is the temperature K reached by the reaction.
The uneven distribution of the fuel gas enables the hydrocarbons to generate rapid NO in the over-rich premixed combustion flame x The temperature dependence is low, and the generated intermediate products HCN, NH and N can further react with oxygen to generate NO x Also increase NO in the flue gas x The emission amount and the generation mechanism are as follows:
CH+N 2 ＝HCN+N
CH 2 +N 2 ＝HCN+NH
HCN/N/NH→NOx
the natural gas has good combustion performance, and almost no residual combustible gas passes through the second section, so that the third section adopts a layer 0 (namely, a burnout zone is not arranged) to reduce the size of the combustor as much as possible and reduce the heat dissipation loss of the combustor to the environment.
The heat released by the flue gas is partially taken away by the flue gas, partially transferred to the tail flue in a radiation mode, and partially dissipated to the environment in a heat conduction mode. Because the number of the holes of the first section of porous medium 4 and the second section of porous medium 5 is different, the hole diameter is different, and the flame surface is subjected to resistance in propagation, the flame surface can be stabilized between the two sections of porous media (the first section of porous medium 4 and the second section of porous medium 5). The smoke passes through the porous medium and then flows through the fork tube type heat exchanger group 7 of the tail flue to carry out convection heat exchange, cold water flows in the tubes and absorbs heat to heat, the temperature is raised, and the generated hot water is output to a user. The heat exchange quantity is calculated according to a first law of thermodynamics and a formula of heat transfer as follows:
in the formula, Q total The heat exchange quantity kJ of the flue gas in the combustor is obtained; m is the mass flow kg/s of the premixed gas of methane and air; t is 11 Is the theoretical combustion temperature K; t' 1 The temperature K of the flue gas at the gas outlet pipe; VC (vitamin C) pj The average specific heat capacity of the flue gas between the theoretical combustion temperature and the outlet temperature of the air outlet pipe is obtained;
in the formula, q is the heat dissipation of the wall surface of the combustor, and is 5 percent;
eta is the burner efficiency, and the calculation expression is as follows:
ω CH4 is the mass fraction of methane in the premixed gas; HLV is the low calorific value of methane 35832kJ/kg;
the radiant and convection heat received by the tubular heat exchanger group 7 is equal to the heat exchange quantity of the flue gas in the combustor, and the basic equation of the heat transfer calculation of the tube group is as follows:
in the formula, Q rad The calculation expression is as follows:
in the formula, q r,,out The radiant heat W is radiated by porous medium solid in the combustor through an air outlet pipe; epsilon is the emissivity of the foamed ceramic type porous dielectric material; a is the cross-sectional area m of the foamed ceramic type porous dielectric material 2 (ii) a Sigma is Stefan-Boltzmann constant, and is generally given as sigma = 5.67X 10 -8 W/(m 2 ·K 4 )；T wall The temperature K of the outer wall surface of the fork exhaust pipe group;
Q cv for convective heat transfer, the calculation expression is:
Q cv ＝hA(T 1 ”-T wall ) In the formula (7)
h is convective heat transfer coefficient W/(m) 2 K), the computational expression is:
wherein λ is the heat conductivity W/(m.K) of the fork tube group; d is the pipe diameter m of the fork exhaust pipe group;
nu is Nussel number, and an empirical formula according to three rows of crossed tube bundles swept by flue gas is as follows:
in the formula, re f The Reynolds number of the smoke sweepforward fork exhaust tube group; pr (Pr) w 、Pr f The number is the Plantt number of the smoke sweep-out fork exhaust pipe group; s 1 /S 2 The relative tube spacing between the fork tube groups;
the heat of radiation and convection received by the cross-arrangement tube type heat exchanger group 7 is also equal to the heat absorption capacity of working medium water in the tube group, and the calculation formula is as follows:
Q rad +Q cv ＝C w m w (T w,out -T w,in ) Equation (10)
In the formula, C w The average specific heat capacity kJ/(kg. K) of water before and after heating; m is a unit of w The mass flow rate of water is kg/s; (T) w,out -T w,in ) The temperature rise K of the working medium water after flowing through the fork tube bank is realized.
After heat exchange, the flue gas enters the contraction section 8, and the flow velocity of the flue gas is increased along with the reduction of the cross section of the flow channel according to a fluid continuity equation, so that the convective heat exchange coefficient is improved, and the heat exchange effect at the position of the cross-exhaust tube type heat exchanger group 7 is enhanced. The contraction section 8 adopts a circular truncated cone structure to accelerate the passing of the flue gas and improve the flowing Reynolds number Re f Thereby increasing the convective heat transfer coefficient h. Reynolds number Re f The following formula is calculated:
Re f ＝ρvd/μ
wherein rho is the density of the flue gas kg/m 3 (ii) a v is the flow velocity m/s of the flue gas; mu is dynamic viscosity of flue gas N.s/m 2 。
Finally, the low-temperature flue gas after sufficient heat exchange is discharged through an air outlet pipe 9. When the work load is low/high, that is, when the gas flow rate is small/large, the load can be adjusted by changing the gas flow rate. The workload is characterized herein by the combustion intensity, calculated as follows:
wherein FR is combustion intensity, i.e., gas discharge power kW/m per unit cross-sectional area of the burner 2 ；q g Is the natural gas flow rate Nm 3 H; a is the cross-sectional area of the burner flow channel, i.e. the cross-sectional area m of the void when no porous medium is filled 2 。
In addition, the preheating and heat storage functions of the porous medium can well maintain the temperature in the combustor, and the segmented pore diameter-variable structure can also increase the flame propagation resistance, enhance the flame stability and prevent backfire and fire escape.
Example 2
The structure of the burner of the present embodiment is shown in fig. 3, and can be applied to, but not limited to, a household gas water heater, and the parameters of each section are shown in table 2. The lower preheating zone (a section of porous medium 4) is divided into 2 layers, the hole number from bottom to top is 100PPI and 80PPI respectively, and the material is an alumina foamed ceramic porous medium material with the thermal conductivity of 35W/(m.K) and the hard impact strength of 150 MPa. The middle section combustion zone (the second section porous medium 5) is divided into 1 layer, the hole number is 60PPI, and the material is a silicon carbide foam ceramic porous medium material with the thermal conductivity of 80W/(m.K) and the maximum available temperature of 1600 ℃. The upper burnout zone (three-section porous medium 6) has 1 layer, the number of pores is 40PPI, and the material is a zirconia foamed ceramic porous medium material with the thermal conductivity of 110W/(m.K) and the hard impact strength of 260 MPa. The fuel is low-heat value gas with flame propagation speed lower than 0.2m/s, such as blast furnace gas, low-concentration coal mine gas, low-heat value tail gas in a chemical process, low-heat value tail gas in a petrochemical industry, biomass pyrolysis gasification gas and the like in the metallurgical industry. The combustible component is mainly 2-10% of CH 4 Small amount of CO, H 2 . The fuel gas has the defects of poor combustibility, unstable combustion and easy fire release, and the ignition point is between 600 and 800 ℃. As shown in FIG. 2, in the lower preheating zone, the low heating value gas first flows through the first 100PPI porous medium material in the preheating zone, the gas flow rate is reduced, the residence time of the fuel gas in the first zone is short, and CO and N are in short range 2 The inert gas absorbs a large amount of heat so that the fuel gas is insufficiently preheated. The combustion gas then passes through the first stage second layer 80PPI porous media material, the number of pores decreases, the pore size increases, and the gas flow rate decreases. The residence time of the low-heat value gas in the whole preheating zone is prolonged, and the low-heat value gas is fully preheated and diffused through the acceleration-deceleration process. In the middle combustion area, the low-calorific-value gas after being fully preheated realizes super-enthalpy combustion in the two layers of porous media, and heat is transmitted back to the preheating area through heat conduction and radiation, so that heat backflow is realized. Because of the existence of a large amount of inert gas, the combustion temperature is low, the flame propagation speed is low, the heat dissipation loss needs to be reduced, and the temperature of the combustion zone needs to be maintained, so that only one layer of the second-stage combustion zone is designed60PPI porous media to stabilize the flame face.
TABLE 2
And then the flue gas enters a layer of 40PPI porous medium in the third burnout zone to prolong a combustion zone, so that a sufficient burnout space is provided for residual gases such as CO and the like, and the function of preventing misfire is achieved. Finally, the travel of the flue gas into the back pass is similar to that described in the first embodiment. The temperature in the whole burner is kept at about 1100 ℃, and NO is added x The discharge amount is less than or equal to 30 mg/(kWh), the CO discharge amount is less than or equal to 0.02% (alpha = 1), and the flame surface is stable.
Example 3
The structure of the burner of the present embodiment is shown in fig. 4, and can be applied to, but not limited to, a household gas water heater, and the parameters of each section are shown in table 3. The lower preheating zone (a section of porous medium 4) is divided into 2 layers, the hole number from bottom to top is respectively 80PPI and 60PPI, and the material is an alumina foamed ceramic porous medium material with the thermal conductivity of 35W/(m.K) and the hard impact strength of 150 MPa. The middle combustion zone (two-section porous medium 5) is divided into 2 layers, the hole number from bottom to top is respectively 50 PPI and 40PPI, and the material is a silicon carbide foamed ceramic porous medium material with the thermal conductivity of 80W/(m.K) and the maximum available temperature of 1600 ℃. The upper-section burnout zone (three-section porous medium 6) has 1 layer, the number of holes is 30PPI, and the material is a silicon nitride foamed ceramic porous medium material with the thermal conductivity of 100W/(m.K) and the hard impact strength of 240 MPa. The burner of the embodiment can still be well applied to liquid fuels or gas-liquid mixed fuels such as kerosene, heptane, decane and the like. The saturated alkane fuel has low ignition point (380 ℃ of kerosene and 204 ℃ of heptane), high flame propagation speed and stability (about 0.7 m/s), and can not be directly introduced into a porous medium burner per se, so that the saturated alkane fuel is required to be matched with an atomizing nozzle for use. Using heptane as an example, as shown in fig. 4, liquid fuel forms small droplets under the atomization action of the atomizing nozzle 10 and enters the air intake pipe 1, and air enters from the periphery of the nozzle in the air intake pipe and carries the fuel liquid. In the lower preheating zone, the mixed fuel first flows through the first 80PPI porous medium material in the first preheating zone, the gas flow rate is reduced, and the liquid drops are attached to the first porous medium to absorb heat and evaporate. The evaporation effect of the liquid drops is a key factor, and considering the atomization effect of the nozzle, the liquid drop particles are not uniform, so that the second layer 60PPI porous medium is designed in the first section to increase the heat absorption time of evaporation, improve the preheating efficiency, and reduce the number of holes to reduce the flow resistance. In the middle section combustion area, the fuel after full evaporation and preheating is stably combusted in the second section combustion area. Because the flame propagation speed is high, the two layers of porous media with different hole numbers of 50 PPI and 40PPI are designed to ensure that a combustion area is long enough to prevent tempering. The heat of the flue gas is transmitted back to the preheating zone through the heat conduction and radiation part to realize heat backflow, and part of the heat is transmitted upwards to the third section to maintain the temperature of the burnout zone.
TABLE 3
The flue gas then enters a layer of 30PPI porous medium in the burnout zone of the third section to be fully burned out, and the third section can also play a role in preventing the deflagration caused by the excessively fast movement of the flame surface. Finally, the travel of the flue gas into the back pass is similar to that described in the first embodiment. The temperature in the whole burner is kept at about 1100 ℃, and NO is added x The emission is less than or equal to 30 mg/(kW.h), the CO emission is less than or equal to 0.02% (alpha = 1), and the flame surface is stable.
The above description is only a part of the embodiments of the present invention, and although some terms are used in the present invention, the possibility of using other terms is not excluded. These terms are used merely for convenience in describing and explaining the nature of the invention and are to be construed as any additional limitation which is not in accordance with the spirit of the invention. The foregoing is merely an illustration of the present invention for the purpose of providing an easy understanding and is not intended to limit the present invention to the particular embodiments disclosed herein, and any technical extensions or innovations made herein are protected by the present invention.
Claims (7)
1. The sectional type porous medium burner is characterized by comprising a burner shell (3), wherein a premixing cavity (2) and a contraction section (8) are respectively arranged at two ends of the burner shell (3), the premixing cavity (2) is connected with an air inlet pipe (1), and the contraction section (8) is connected with an air outlet pipe (9); a tubular heat exchanger group (7) is arranged in the combustor shell (3) close to the contraction section (8), and a plurality of sections of porous media are filled in sections close to the premixing cavity (2); the pore diameter and the heat conductivity of a plurality of sections of porous media are increased progressively along the direction from the premixing cavity (2) to the contraction section (8), and no gap exists between adjacent sections of porous media; the porous medium comprises a first section of porous medium (4), a second section of porous medium (5) and a third section of porous medium (6) with the thickness ratio of (1-2) to (0-2), wherein the pore density of the first section of porous medium (4) is 40-100 PPI, the pore density of the second section of porous medium (5) is 20-70 PPI, and the pore density of the third section of porous medium (6) is 5-40 PPI; the first section of porous medium (4), the second section of porous medium (5) and the third section of porous medium (6) respectively comprise a plurality of layers with different pore density and thermal conductivity; when the flame propagation speed of the fuel is lower than 0.3m/s, the thickness ratio of the first section of porous medium (4), the second section of porous medium (5) and the third section of porous medium (6) is 2; when the flame propagation speed of the fuel is 0.3-0.5 m/s, the thickness ratio of the first section of porous medium (4), the second section of porous medium (5) and the third section of porous medium (6) is 1; when the flame propagation speed of the fuel is more than 0.5m/s, the thickness ratio of the first section of porous medium (4), the second section of porous medium (5) and the third section of porous medium (6) is 2.
2. The segmented porous medium burner according to claim 1, wherein an atomizing nozzle (10) is provided in the inlet pipe (1) when the fuel is liquid fuel or gas-liquid mixed fuel.
3. The segmented porous medium burner according to claim 1, wherein the thermal conductivity of the first porous medium (4) is 0.6-2.2W/(m-K), the thermal conductivity of the second porous medium (5) is 5.2-12W/(m-K), and the thermal conductivity of the third porous medium (6) is 20-50W/(m-K).
4. The segmented porous medium burner of claim 3, wherein the material of the segment of porous medium (4) is alumina, aluminum titanate, cordierite or quartz ceramic; the material of the second-stage porous medium (5) is mullite, nickel-based alloy, nickel-chromium-iron alloy or porous tungsten; the three sections of porous media (6) are made of silicon carbide, silicon nitride or zirconia.
5. The segmented porous media burner of claim 1, wherein the total thickness of porous media is between 0.3 and 0.6 times the height of the combustion chamber.
6. The segmented porous medium burner according to claim 1, characterized in that the cross-sectional area of the premixing chamber (2) is gradually enlarged and the cross-sectional area of the contraction section (8) is gradually reduced in the direction from the inlet pipe (1) to the outlet pipe (9).
7. The method of operating a segmented porous media burner as claimed in any one of claims 1 to 6, comprising:
combustible gas and air enter from the air inlet pipe (1), then are fully disturbed and mixed in the premixing cavity (2), then enter into a plurality of sections of porous media, are decelerated by pore structures in the porous media, are further uniformly mixed, and simultaneously absorb heat transferred from the rear section of porous media in radiation and heat conduction modes in the front section of porous media to preheat and raise the temperature; after being fully preheated, the mixture continuously flows along the inside of the porous medium to carry out super-enthalpy combustion to form flue gas; the heat of the flue gas is rapidly transferred to the porous medium of the adjacent section through solid heat conduction and radiation, and the combustor maintains thermal NO in the combustion process x Low emission of (2); the smoke and part of residual combustible gas are burnt out in the porous medium at the tail section, part of heat released by the smoke is taken away by the smoke, part of heat is transmitted to the tail flue in a radiation mode, and part of heat is transmitted to the porous medium through heat conduction and radiation; because the pore diameters and the pore numbers of a plurality of sections of porous media are different, the propagation of the flame surface is blocked, and the flame surface can be stabilized between the adjacent sections of porous media; the flue gas passes through the porous medium and then flows through a tubular heat exchanger group (7) of the tail flue to carry out convection heat exchange, cold water flows in the tube and absorbs heat to raise the temperature, and the generated hot water is output to the combustor.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201827891U (en) * | 2010-09-26 | 2011-05-11 | 宝山钢铁股份有限公司 | Anti-backfire premixing porous medium burner nozzle |
| CN106642103A (en) * | 2016-10-21 | 2017-05-10 | 浙江大学 | Porous medium burner for gas fuel |
| CN109708299A (en) * | 2017-10-25 | 2019-05-03 | 芜湖美的厨卫电器制造有限公司 | Gas heater |
| CN110425536A (en) * | 2019-08-06 | 2019-11-08 | 东北大学 | A kind of angle-style porous media combustor |
| CN112856406A (en) * | 2021-01-15 | 2021-05-28 | 中国科学院广州能源研究所 | Multilayer porous medium combustor |
-
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201827891U (en) * | 2010-09-26 | 2011-05-11 | 宝山钢铁股份有限公司 | Anti-backfire premixing porous medium burner nozzle |
| CN106642103A (en) * | 2016-10-21 | 2017-05-10 | 浙江大学 | Porous medium burner for gas fuel |
| CN109708299A (en) * | 2017-10-25 | 2019-05-03 | 芜湖美的厨卫电器制造有限公司 | Gas heater |
| CN110425536A (en) * | 2019-08-06 | 2019-11-08 | 东北大学 | A kind of angle-style porous media combustor |
| CN112856406A (en) * | 2021-01-15 | 2021-05-28 | 中国科学院广州能源研究所 | Multilayer porous medium combustor |
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