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WO2020019463A1 - Structure de spoiler appliquée à un traitement de gaz de queue et mélangeur scr composite - Google Patents

Structure de spoiler appliquée à un traitement de gaz de queue et mélangeur scr composite Download PDF

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Publication number
WO2020019463A1
WO2020019463A1 PCT/CN2018/106921 CN2018106921W WO2020019463A1 WO 2020019463 A1 WO2020019463 A1 WO 2020019463A1 CN 2018106921 W CN2018106921 W CN 2018106921W WO 2020019463 A1 WO2020019463 A1 WO 2020019463A1
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WIPO (PCT)
Prior art keywords
spoiler
peripheral wall
spoiler structure
wall
gas treatment
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/CN2018/106921
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English (en)
Chinese (zh)
Inventor
张超锋
孙川
候晓澄
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Jiangnan University
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Jiangnan University
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Publication date
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Publication of WO2020019463A1 publication Critical patent/WO2020019463A1/fr
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion
    • F01N3/206—Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2892—Exhaust flow directors or the like, e.g. upstream of catalytic device
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • the invention relates to the technical field of exhaust aftertreatment of diesel engines, in particular to a spoiler structure and a composite SCR mixer applied to exhaust gas treatment.
  • the mixer can fully mix the vapor phase and the liquid phase, accelerate the pyrolysis of the urea aqueous solution, thereby improving the conversion efficiency of the catalyst and reducing the risk of crystallization on the wall.
  • the indicators for measuring the mixer mainly include: carrier velocity uniformity, ammonia uniformity, back pressure loss and anti-crystallization performance under low temperature operation of the engine.
  • the static mixing unit fixed in the pipe is used to change the flow state of the exhaust gas, so that the fluid is in the pipeline. The flow impacts various types of plate elements, thereby breaking the spray droplets.
  • Existing mixers are divided into two categories: grid baffle structure and spiral leaf structure.
  • the grid baffle structure mixer uses grid-shaped blades staggered up and down as a mixing unit, and the inclination angle of each blade is generally 45 degrees.
  • Rotary blade structure mixers usually use several blades with a certain angle with the horizontal plane, which are divided into single-layer arrangement type and double-layer arrangement type.
  • the former mixer structure can get better velocity uniformity of the front end of the carrier, but the ammonia uniformity is relatively low, and the latter is just the opposite.
  • the grid baffle structure can effectively prevent the formation of block crystals in the middle of the mixer, while the rotary leaf structure mixer can effectively suppress the formation of crystals on the tube wall of the catalyst.
  • the object of the present invention is to provide a spoiler structure and a compound SCR mixer for tail gas treatment, and the rotary blade of the second spoiler can effectively increase the gas flow velocity near the tube wall and improve the component homogenization effect.
  • the temperature of the pipe wall is increased to reduce the risk of crystal formation on the pipe wall; and the grids and baffles of the first spoiler are densely arranged, which can improve the uniformity of the speed of the airflow; the structure of each part of the first spoiler and the second spoiler
  • the functions can be mutually promoted to achieve the effect of maximizing the functions of the hybrid accessories in a limited space.
  • a spoiler structure applied to exhaust gas treatment includes a first spoiler, including a grille, a baffle, and a first peripheral wall;
  • the baffle is disposed on the grille, and the first peripheral wall is disposed on the periphery of the grille;
  • a second spoiler the second spoiler includes a rotary blade and a second peripheral wall, The second peripheral wall is disposed on the periphery of the first peripheral wall, and the spiral leaf is interposed between the second peripheral wall and the first peripheral wall.
  • the grid includes a horizontal substrate and a vertical substrate, and the horizontal substrate and the vertical substrate are intersected.
  • the plane N formed by the horizontal substrate and the vertical substrate is arranged at a certain angle with the baffle.
  • the baffle is divided into a first facing body and a second facing body, and the first facing body and The second facing bodies are arranged adjacently, and the adjacent first facing bodies and the second facing bodies are staggered in opposite directions.
  • the first facing body and the second facing body are both disposed on the vertical substrate.
  • the first peripheral wall and the second peripheral wall are both annular structures.
  • the spiral blade includes a first end surface, a second end surface, a third end surface, and a fourth end surface.
  • the first end face, the second end face, the third end face, and the fourth end face are connected end to end in sequence;
  • the second end surface and the fourth end surface are both arc-shaped structures, and the second end surface is disposed on the periphery of the fourth end surface.
  • connection points of the first end face, the second end face, the third end face, and the fourth end face are sequentially One intersection n, second intersection n, third intersection n and fourth intersection n;
  • first intersection edge n and the second intersection edge n are respectively connected to both ends of the first peripheral wall
  • the third intersection n and the fourth intersection n are respectively connected to both ends of the second peripheral wall.
  • a compound CSR mixer is based on the compound according to claims 1 to 8 Application of spoiler structure
  • the mixer further includes a mixing accessory, and the spoiler structure is disposed in the mixing accessory.
  • the mixing accessories include a carrier and a spraying member, and the spraying member is embedded in and arranged at a certain angle. Inside the carrier
  • the nozzle of the spraying member faces the grille of the spoiler structure.
  • the present invention has reasonable design, compact spoiler structure, and the rotating blades of the second spoiler can effectively increase the gas flow velocity near the tube wall, increase the component homogenization effect, and simultaneously increase the tube wall temperature and reduce the tube.
  • the risk of wall crystal formation; and the dense arrangement of the grille and baffle of the first spoiler can improve the uniformity of the velocity of the airflow; the structural functions of the first spoiler and the second spoiler can promote each other, achieving In the limited space, the effect of the maximum function of the hybrid accessories is exerted; at the same time, under the premise of ensuring high mixing uniformity, the back pressure loss is the lowest compared to traditional hybrid accessories, which meets the needs of use.
  • FIG. 1 is a schematic structural view of the spoiler structure applied to the exhaust gas treatment of the present invention and the front view of the spoiler structure of the first embodiment of the composite SCR mixer.
  • FIG. 2 is a schematic view of a rear view of a spoiler structure applied to exhaust gas treatment according to the present invention and a spoiler structure according to the first embodiment of the composite SCR mixer.
  • FIG. 3 is a schematic view of a spoiler structure applied to exhaust gas treatment according to the present invention and the structure of a rotary blade according to the first embodiment of the composite SCR mixer.
  • FIG. 4 is a schematic diagram of the structure of a spoiler structure applied to exhaust gas treatment according to the present invention and a compound SCR mixer according to a second embodiment of the compound SCR mixer.
  • FIG. 5 is a spoiler structure applied to exhaust gas treatment according to the present invention and a, b, c, and d of a third embodiment of the composite SCR mixer, which respectively represent four types of grid plate type, baffle type, rotary blade type, and composite type. Schematic diagram of the spoiler structure.
  • FIG. 6 is a velocity field cloud diagram of four spoiler structures a, b, c, and d of the third embodiment of the composite SCR mixer according to the spoiler structure applied to the exhaust gas treatment of the present invention.
  • FIG. 7 is a schematic diagram of the velocity distribution within 10 cm of the front surface of the four spoiler structures a, b, c, and d of the third embodiment of the composite SCR mixer according to the spoiler structure applied to the exhaust gas treatment of the present invention.
  • FIG. 8 is a schematic diagram of the front-end surface velocity distribution cloud diagram of the four spoiler structures a, b, c, and d of the third embodiment of the composite SCR mixer according to the spoiler structure applied to the exhaust gas treatment of the present invention.
  • FIG. 9 is a schematic diagram of the ammonia distribution within 10 cm of the front end surface of the four spoiler structures a, b, c, and d of the third embodiment of the composite SCR mixer according to the spoiler structure applied to the exhaust gas treatment of the present invention.
  • FIG. 10 is a schematic diagram of an ammonia distribution cloud at the front end surface of the four spoiler structures a, b, c, and d of the third embodiment of the composite SCR mixer according to the spoiler structure applied to the exhaust gas treatment of the present invention.
  • FIG. 11 is a schematic diagram of the liquid film temperature distribution of the agitator structure of four types of agitator structure a, b, c, and d of the composite SCR mixer according to the third embodiment of the present invention applied to exhaust gas treatment.
  • FIG. 12 is a liquid film thickness distribution diagram of a turbulent structure applied to exhaust gas treatment according to the present invention, and a, b, c, and d four turbulent structure mixers of the third embodiment of the composite SCR mixer.
  • FIG. 13 is a schematic diagram of a radial temperature distribution downstream of the four spoiler structures a, b, c, and d of the third embodiment of the composite SCR mixer according to the spoiler structure applied to the exhaust gas treatment of the present invention.
  • FIG. 14 is a spoiler structure applied to exhaust gas treatment according to the present invention, and a, b, c, and d four types of spoiler structures of the third embodiment of the composite SCR mixer. Distribution diagram.
  • FIG. 15 is a turbulent structure applied to the exhaust gas treatment of the present invention and a liquid film distribution diagram on the side of the tube wall of the four turbulent structures a, b, c, and d of the third embodiment of the composite SCR mixer.
  • FIG. 16 is a liquid film distribution diagram of the bottom surface of the tube wall of the four types of spoiler structures a, b, c, and d of the third embodiment of the composite SCR mixer according to the spoiler structure applied to the exhaust gas treatment of the present invention.
  • FIG. 17 is a schematic view of the turbulent structure applied to the exhaust gas treatment of the present invention and the distribution of crystals upstream of the four turbulent structure a, b, c, and d mixers of the third embodiment of the composite SCR mixer.
  • FIG. 18 is a schematic view of a crystalline structure downstream of four turbulent structures a, b, c, and d of the third embodiment of the composite SCR mixer according to the turbulent structure applied to the exhaust gas treatment of the present invention.
  • FIG. 19 is a schematic diagram showing the weighing quality of the four spoiler structures a, b, c, and d of the third embodiment of the compound SCR mixer according to the present invention, which is used for exhaust gas treatment.
  • FIG. 20 is a schematic diagram of the spoiler structure applied to the exhaust gas treatment of the present invention and the pressure loss of the four spoiler structures a, b, c, and d of the third embodiment of the composite SCR mixer.
  • an embodiment or “an embodiment” referred to herein refers to a particular feature, structure, or characteristic that can be included in at least one implementation of the present invention.
  • the appearances of "in one embodiment” in various places in this specification do not all refer to the same embodiment, nor are they separate or selectively mutually exclusive embodiments.
  • a first embodiment of the present invention provides a turbulent structure applied to exhaust gas treatment and a schematic diagram of the overall structure of a composite SCR mixer.
  • a turbulence applied to exhaust gas treatment is provided.
  • the flow structure and the composite SCR mixer include a spoiler structure 100 including a first spoiler 101 including a grille 101a, a baffle 101b, and a first peripheral wall 101c.
  • the baffle 101b is provided on the grille 101a, and the first periphery
  • the wall 101c is provided on the periphery of the grille 101a; and, the second spoiler 102 includes a spiral blade 102a and a second peripheral wall 102b, and the second peripheral wall 102b is provided on the periphery of the first peripheral wall 101c.
  • the rotary blade 102a is interposed between the second peripheral wall 102b and the first peripheral wall 101c.
  • the main structure of the present invention includes a spoiler structure applied to exhaust gas treatment.
  • the spoiler structure 100 includes a first spoiler 101 and a second spoiler 102.
  • the structural functions of the two components can promote each other to achieve In the limited space, the effect of the maximum function of the mixing accessories is exerted.
  • the back pressure loss is the lowest compared to traditional mixing accessories.
  • the first spoiler 101 includes the grille 101a.
  • the baffle 101b and the first peripheral wall 101c cooperate with each other, so that under forced convection, vortex diffusion and molecular diffusion are achieved, so that the gas and liquid phases are fully mixed, and the speed and the uniformity of ammonia distribution are simultaneously improved.
  • the baffle 101b is disposed on the grille 101a, and the first peripheral wall 101c is wrapped around the periphery of the grille 101a.
  • the grille 101a, the baffle 101b, and the first peripheral wall 101c are integrated structures.
  • the second spoiler 102 divides the airflow into a large-scale vortex, so that the airflow is rotated near the wall surface of the bearing member 201 to generate a vortex, which promotes mass transfer at the bearing member, and includes a rotating blade 102a and a second periphery.
  • the second peripheral wall 102b is disposed on the periphery of the first peripheral wall 101c, and the two are connected by the rotary blade 102a, so the rotary blade 102a is interposed between the second peripheral wall 102b and the first peripheral wall 101c, and the rotary blade 102a is generated
  • the near-wall surface swirls which creates a surface coupling effect with the middle airflow, improves the wall heat distribution, reduces the risk of liquid film accumulation at the pipe wall, and can effectively reduce the probability of crystal formation.
  • the first spoiler 101 and the second The spoiler 102 is an integrated structure and is made of cast iron or stainless steel.
  • the grid 101a includes a horizontal substrate 101a-1 and a vertical substrate 101a-2, and the horizontal substrate 101a-1 and the vertical substrate 101a-2 are intersected, wherein the number of the horizontal substrate 101a-1 and the vertical substrate 101a-2 is at least There are two (the number in the figure is for reference only), where the plane N formed by the horizontal substrate 101a-1 and the vertical substrate 101a-2 and the baffle 101b are arranged at a certain angle, and the angle and Yes, in this embodiment, the plane N formed by the horizontal substrate 101a-1 and the vertical substrate 101a-2 is arranged at an angle of 45 ° with the baffle plate 101b; and the horizontal substrate 101a-1 and the vertical substrate 101a-2 are perpendicular to each other. Settings.
  • the baffle 101b is divided into a first facing body 101b-1 and a second facing body 101b-2, and the first facing body 101b-1 and the second facing body 101b-2 are disposed adjacent to each other, and adjacent to the first facing body 101b-1 and second orientation body 101b-2 are staggered in reverse, which can create turbulence on the exhaust gas and promote rapid pyrolysis of droplets.
  • the first orientation body 101b-1 and the second orientation body 101b-2 Both are trapezoidal structures; it should be noted that the first facing body 101b-1 and the second facing body 101b-2 are both disposed on the vertical substrate 101a-2.
  • first peripheral wall 101c and the second peripheral wall 102b are both annular structures, and the two are concentric rings; the first peripheral wall 101c is disposed inside the second peripheral wall 102b.
  • the rotary blade 102a includes a first end surface 102a-1 and a second end surface 102a.
  • Both the second end surface 102a-2 and the fourth end surface 102a-4 are arc-shaped structures, and the second end surface 102a-2 is disposed on the periphery of the fourth end surface 102a-4; it should be noted that the first end surface 102a-1, the second end surface The junctions of the end faces 102a-2, the third end face 102a-3, and the fourth end face 102a-4 are, in order, the first intersection n1, the second intersection n2, the third intersection n3, and the fourth intersection n4; A cross edge n1 and a second cross edge n2 are connected to both ends of the first peripheral wall 101c; wherein a third cross edge n3 and a fourth cross edge n4 are connected to both ends of the second
  • a second embodiment of the present invention is different from the first embodiment in that the composite SCR mixer includes a spoiler structure 100, and further includes a mixing accessory 200, a spoiler structure 100 and a hybrid
  • the fittings 200 cooperate with each other to achieve the maximum function of the mixed fittings 200 in a limited space and the process of discharging.
  • the back pressure loss is the lowest compared to the traditional mixing fittings 200, which meets Usage requirements.
  • the main structure includes a spoiler structure 100 including a first spoiler 101 and a second spoiler 102, and the structural functions of the two components can promote each other to achieve the maximum performance of the hybrid accessories in a limited space.
  • the first spoiler 101 includes a grille 101a, a baffle 101b, and a first periphery.
  • the wall 101c and the three cooperate with each other, so that they can be fully mixed by the vortex diffusion and molecular diffusion under forced convection, and the purpose of simultaneously improving the speed and the uniformity of ammonia distribution is achieved.
  • the baffle 101b It is arranged on the grille 101a, and the first peripheral wall 101c is wrapped around the periphery of the grille 101a.
  • the grille 101a, the baffle 101b, and the first peripheral wall 101c are an integrated structure; the second spoiler 102,
  • the airflow is divided into large-scale vortices, so that the airflow rotating near the wall surface of the carrier 201 generates vortices, which promotes mass transfer at the carrier, and includes a rotating blade 102a and a second peripheral wall 102b.
  • the second peripheral wall 102b is provided at The periphery of a peripheral wall 101c, the two are connected by a rotating blade 102a, so the rotating blade 102a is located between the second peripheral wall 102b and the first peripheral wall 101c.
  • the near-wall surface swirl generated by the spiral blade 102a and the middle airflow Generate surface coupling effect, improve the wall heat distribution, reduce the risk of liquid film accumulation at the wall of the tube, and effectively reduce the probability of crystal formation.
  • the first spoiler 101 and the second spoiler 102 are integrated structures. Made of cast iron or stainless steel.
  • the composite SCR mixer also includes a mixing part 200.
  • the mixing part 200 includes a carrier 201 and a sprinkler 202.
  • the sprinkler 202 is embedded in the carrier 201 by welding at a certain angle, and the spoiler structure 100 is disposed in the carrier 201
  • the two can be made by bolts or welding.
  • the spraying part 202 uses a three-hole nozzle
  • the carrier 201 is a cylindrical shell and is made of cast iron
  • the nozzle of the spraying part 202 faces the turbulence in the same direction as the exhaust gas flow direction.
  • the grille 101a of the structure 100 provides such a better mixing.
  • both ends of the bearing member 201 are provided with a first connection flange 201a and a second connection flange 201b.
  • the first connection flange 201a is connected to the exhaust exhaust pipe by a bolt
  • the second connection flange 201b is connected to the exhaust pipe by a bolt. Exhaust gas inlet pipe connection.
  • the flow structure 100 is a composite structure.
  • the spoiler structure 100 is installed in a suitable mixing fitting 200, which can make the composite SCR mixer significantly improve the flow field distribution, make the vapor phase meet the liquid phase to be fully mixed, and accelerate the pyrolysis of the urea aqueous solution, thereby improving the composite SCR mixing.
  • the conversion efficiency of the device reduces the risk of crystallization on the wall surface of the carrier 201.
  • the indicators for measuring the compound SCR mixer mainly include: carrier velocity uniformity, ammonia uniformity, back pressure loss and anti-crystallization performance under low temperature operation of the engine.
  • the mixing process generally uses a static mixing unit fixed in the carrier tube to change the flow state of the exhaust gas, so that the fluid flows in the pipeline to impact various types of plate elements, so that the spray droplets are completely broken.
  • (A) of FIG. 5 is a grid plate type spoiler structure, in which each baffle unit is at an angle of 45 ° to the horizontal plane, and 6 rows and 7 rows are staggered.
  • the dead corners of crystals may be generated at the reverse staggering of the blades, and improve the heat transfer efficiency on the wall surface;
  • the large plate structure at 70 ° to the horizontal plane, with the outer blades facing down and the middle part facing up, can create turbulence for the exhaust gas division, and promote rapid pyrolysis of the droplets.
  • the spoiler structure is designed as a double-layered spiral blade structure (Figure 5 (c)), which constitutes a spiral-blade-type spoiler structure.
  • each layer consists of 9 blades. Structure, the first layer is arranged counterclockwise, and the second layer is arranged counterclockwise; the droplets first hit the wall surface of the spoiler structure to complete the crushing, and then the swirl created by the blade is fully mixed with the exhaust gas, so that the droplets quickly Pyrolysis.
  • the traditional spoiler structure usually does not consider the crystallization of the wall surface. Therefore, based on the traditional grid plate spoiler structure (Figure 5 (a)), 8 blades with inclined angles are designed on the outside of the grid plate ( Figure 5 (d) )), Which constitutes the preferred composite spoiler structure, which generates swirling near-wall surface through these blades, and generates a coupling effect with the middle airflow, thereby improving the uniformity of airflow while improving the heat distribution on the wall.
  • the test bench mainly includes a VM28 (97KW) diesel engine (such as Table 1), an SCR aftertreatment system, an electric dynamometer and its control system, a fuel supply and fuel consumption measurement system, an intercooler, and a multi-component gas analyzer.
  • VM28 97KW diesel engine
  • the above-mentioned four spoiler components are respectively welded to the flange, and then installed at a distance of 10 cm from the rear end of the spray member 202.
  • ESC European Steady-State Cycle
  • ETC European Unsteady-State Cycle
  • the uneven flow velocity distribution for a long time will cause excessive air velocity and temperature at the higher flow velocity of the carrier, which will cause the radial temperature gradient of the catalyst to be too large, which will generate thermal stress gradients, cause thermal fatigue damage, accelerate the catalyst's degradation and reduce its Service life.
  • the uneven distribution of reducing agent will cause local excessive or insufficient ammonia distribution, resulting in reduced SCR catalytic efficiency and ammonia gas leakage, uneven catalyst aging, and affecting the overall catalytic performance.
  • the performance of the rate must make the UWS distributed as evenly as possible on the front surface of the carrier. Its uniformity coefficient is expressed as follows:
  • Vi is the normal velocity of the unit carrier
  • Vmean is the normal average velocity of the end face of the carrier air inlet
  • A is the cross-sectional area of the unit
  • Ai is the total number of interface meshes.
  • the velocity field distribution of the four spoiler structures is shown in Figure 6.
  • the airflow in the middle of the downstream of the inlet pipe with the grid channel plate spoiler structure is relatively smooth.
  • the axial speed in the tube 201 is stable and the uniformity of the speed in the tube is better ( Figure 6 (a)).
  • the velocity uniformity of the UWS in the axial distance in front of the spoiler structure carrier is directly related to the utilization of the catalyst.
  • the velocity uniformity of the axial cross sections in the range of 10 cm in length of the front surface of the carrier under different spoiler structures is shown in Figure 7; the velocity uniformity of Case1 and Case2 at 8 cm in the mixing cavity suddenly decreases, and the lowest values are respectively 0.64 and 0.72; the overall velocity uniformity is significantly lower than Case3 and Case4; although Case3 has the highest uniformity index at 0 to 8 cm away from the carrier, there is also a sudden decrease in velocity uniformity in Case 3 at 9 cm Compared with case1 and case2, the minimum value is increased to 0.79; Case4 is the only test piece that does not show a sudden decrease in velocity uniformity, which makes its uniformity index in the area 10cm in front of the carrier reaches more than 8.3, which significantly improves the velocity distribution in the mixing cavity. Uniformity can effectively eliminate dead angles in low-speed flow areas.
  • the reducing agent uniformity index in the mixing chamber is an important index to measure whether the mixer can continuously obtain the maximum denitration rate and the minimum ammonia leakage.
  • Figure 9 shows the uniform exponential distribution of ammonia in the axial section at 10 cm in front of the carrier when different spoiler structures are loaded.
  • the plate-like blade spoiler structure of case1 and case2 can produce axially stable laminar flow, but it cannot overcome the disturbance of the airflow by the mixing plate, which leads to a significant exponential drop near the mixing plate at 8cm in both scenarios. Zone, ammonia uniformity is lowest at 0.53 and 0.57.
  • case3 and case4 spoiler structure with spiral blade structure effectively eliminates the sudden decrease in the ammonia uniformity index caused by the mixing plate by manufacturing a circumferential rotating airflow, and at the same time ensures that the axial ammonia concentration distribution index in the mixing chamber is always Keep above 0.75, which is nearly 1.5 times that of case1 and case2.
  • Table 2 reflects the velocity uniformity and ammonia uniformity index at 1 cm inside the carrier. From the table we can see that traditional case1 has advantages in speed uniformity, while case3 has advantages in ammonia uniformity.
  • the new composite spoiler structure designed in this paper not only combines the advantages of case1 and case3, but also improves the speed uniformity and ammonia uniformity to 0.993 and 0.924, respectively.
  • For component homogenization and mass transfer when the exhaust gas enters the intake pipe, the airflow passing through the outer blades of the spoiler structure is divided into large-scale vortices, so that the near-surface airflow rotates to generate vortices, which promotes mass transfer at the pipe wall.
  • the swirling flow at the wall of the tube drives the airflow stretched and sheared through the middle grid baffle to rotate, so that it can diffuse through the vortex and molecular diffusion under the force of convection, thereby achieving the purpose of sufficient mixing of gas and liquid phases.
  • the purpose of simultaneously improving the speed and the uniformity of ammonia distribution is achieved.
  • the temperature of the wall film is the main factor that determines the chemical properties of the relevant sediments.
  • the temperature of the wall film is between about 160 ° C and 170 ° C. Once crystals are formed in low temperature conditions, not only will the exhaust pipe be blocked and the back pressure will be increased, but the flow field distribution will be changed and the working efficiency of the mixer will be reduced.
  • the liquid film temperature distribution of the spoiler structure is shown in Figure 11.
  • case1 there is a large area of low temperature in the lower part of the blade (T ⁇ 133 °C), and the maximum temperature difference of the liquid film of the spoiler structure is 102 ⁇ 110 °C ( Figure 11 (a)).
  • case2 there is a low temperature region (T ⁇ 155 ° C) at the third and third row of baffles ( Figure 11 (b)).
  • the temperature distribution of the other baffles is uniform and the temperature is mostly above 200 ° C. It can be seen that the large blade structure can be used. Improve the temperature of the liquid film on the wall to a certain extent.
  • the spiral leaf-like spoiler structure case3 is located at the tip of the blade where the nozzle is directly sprayed and there is an obvious low-temperature liquid film aggregation area at the second layer of spiral leaves (Figure 11 (c)).
  • the temperature distribution of case4 is better than the other three schemes.
  • the grid plate area in the middle of the spoiler structure is evenly heated.
  • the low temperature area is mainly distributed on the three blades at the junction of the spoiler structure and the bottom of the pipe wall ( Figure 11 (d)). There may be liquid film deposition on the leaves.
  • the liquid film temperature determines the liquid film thickness distribution of the spoiler structure and the location of the sediment to a certain extent.
  • the probability of liquid film accumulation in regions with a temperature below 156 ° C is significantly higher than in other parts.
  • Figure 13 shows the radial temperature distribution in the downstream direction of the turbulent structure perpendicular to the tube wall (tube wall diameter 8cm).
  • the abscissa axis 0 is the upper edge near the nozzle
  • 8 is the contact portion between the lower edge and the bottom of the tube wall
  • the right end is the disturbance.
  • the flow structure contacts the pipe wall. It can be observed from the figure that when the spray particles first came into contact with the wall of the spoiler structure, the temperature of the upper area of case1 was 172 ° C, which was about 30 ° C lower than the other three types, and the difference in the temperature distribution of the grid plate was small. A significant temperature decrease was observed at 6cm in the middle and lower part of case2.
  • FIG 14 shows the temperature distribution at the axial 14cm downstream of the contact point between the spoiler structure and the bottom of the wall.
  • the left end of the abscissa axis is the contact point between the spoiler structure and the pipe wall, and the right end is 14cm away from this point.
  • the temperature range of case1 is 195 ⁇ 207 °C, the fluctuation range is small, and the temperature distribution is ideal.
  • the average temperature of the wall area of case2 is the lowest of the four schemes, and there is a continuous low temperature region at 6-9cm, and the lowest temperature is reduced to 153 ° C, which is relatively easy to form crystals.
  • Case3 Although the wall temperature of Case3 decreased significantly at 5-9 cm, the overall temperature range was 174-214 ° C, and the lowest value was still higher than the high sediment formation risk temperature (T ⁇ 170 ° C).
  • T ⁇ 170 ° C The temperature distribution of Case4 ranges from 189 to 211 ° C, and the overall temperature is maintained at a relatively high level.
  • the heat transfer effect of the composite spoiler structure on the downstream pipe wall is significantly better than that of case2 and case3.
  • Case2 has a small area of liquid film deposition along the circumference of the tube wall ( Figure 15 (a)), and most of the sediment is concentrated at the bottom of the tube wall ( Figure 16 (a)). This part has a great risk of crystallization.
  • the deposition area of case3 is mainly concentrated in the circumferential area ( Figure 15 (c)) where the spoiler structure contacts the bottom of the tube wall, and no obvious liquid film aggregation area is observed at the bottom of the wall ( Figure 16 (c)).
  • Case3 spiral-blade spoiler structure produces severe crystallization at the blade interlayer.
  • Figure 17 (c) The formation of massive crystals is due to the larger liquid film area of the blade under the spoiler structure.
  • Figure 12 (c) resulting in accumulation effects.
  • the uneven heating of the blades at the bottom of the spoiler structure can't make the reducing agent pyrolyze quickly.
  • Case4 has the least crystals on the composite spoiler structure, and the amount of crystals at the tube wall is significantly lower than that of case1. This is mainly because the outer blades make the airflow rotate to increase the airflow velocity near the wall, which improves the heat and mass transfer at the wall. The situation makes the liquid film hard to accumulate here, and effectively reduces the risk of crystallization on the wall surface.
  • the spoiler structure only has a small amount of crystals attached in the middle and lower part of the grid baffle, the amount of crystals is significantly less than that of case 1, and no block crystals are generated to block the pipeline.
  • Figure 17 (d) This is because the outer swirling flow causes the airflow at the central grid plate to move in a circumferential direction, reducing the residence time of the droplets on the wall surface, and effectively reducing the risk of forming a liquid film deposition area.
  • the parts loaded with the four spoiler structures were disassembled and weighed, as shown in Figure 19, and the weight of the sediment was obtained by comparing the weight difference of the system before and after the experiment (the measurement accuracy is ⁇ 0.01 g). It is found from the figure that the crystal weight of the spoiler structure gradually increases from case1 to case3, and the minimum crystal weight of case4 is 2.31g, which are respectively 34.7%, 22.6%, and 16.7% of case1, case2, and case3.
  • the experimental data show that although the double-layer spiral leaf structure can obtain better ammonia uniformity, it is very easy to form large crystals at low temperature conditions.
  • the spoiler structure with a grid channel plate can effectively improve the structure. Crystallization performance of the mixer under low temperature conditions.
  • FIG 20 shows the back pressure loss of the four spoiler structures. It can be seen from the figure that the back pressure loss of the case 4 composite spoiler structure is similar to the back pressure loss of case 1, but the ammonia uniformity of the former is 6.7% higher than that of the latter. . At the same time, when the ammonia uniformity of case4 and case3 is close, the pressure loss of the former is effectively reduced by 139Pa compared with the latter. In summary, the spoiler structure of case 4 has better comprehensive performance.
  • this study proposes a new composite spoiler structure in combination with the existing spoiler structure.
  • the new spoiler structure significantly reduces the amount of crystals under low temperature conditions, which significantly improves the mixer's resistance to crystal formation under low temperature conditions.
  • the ammonia uniformity index is increased by 6.7%, 3.1%, and 0.07% compared to case1, case2, and case3, respectively. Moreover, in the case of obtaining the same ammonia uniformity (compared to case 3), the exhaust back pressure is reduced by 7.8%.
  • the installation of a rotating blade structure on the spoiler structure can effectively increase the gas flow velocity near the tube wall, improve the component homogenization effect, increase the tube wall temperature, and reduce the risk of crystal formation on the tube wall.
  • the dense grid baffle structure can improve the velocity uniformity of the airflow.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

La présente invention concerne une structure de spoiler appliquée à un traitement de gaz de queue et un mélangeur SCR composite. La structure de spoiler (100) comprend : un premier élément de spoiler (101) comprenant une grille (101a), une plaque déflectrice (101b) et une première paroi périphérique (101c), la plaque déflectrice (101b) étant disposée sur la grille (101a), et la première paroi périphérique (101c) étant agencée au niveau de la périphérie externe de la grille (101a) ; et un second élément de spoiler (102), le second élément de spoiler (102) comprenant une lame rotative (102a) et une seconde paroi périphérique (102b), la seconde paroi périphérique (102b) étant disposée au niveau de la périphérie externe de la première paroi périphérique (101c), et la lame rotative (102a) étant disposée entre la seconde paroi périphérique (102b) et la première paroi périphérique (101c). La structure de spoiler présente une structure compacte. Avec la lame rotative (102a) du second élément de spoiler (102), la vitesse d'écoulement de gaz à proximité d'une paroi de tuyau peut être efficacement augmentée afin d'améliorer l'effet d'homogénéisation de composant ; et dans le même temps, la température de la paroi de tuyau est augmentée pour réduire le risque de formation de substances cristallines sur la paroi de tuyau. De plus, la grille (101a) et la plaque déflectrice (101b) du premier élément de spoiler (101) sont agencées de manière dense, de telle sorte que l'uniformité de vitesse de l'écoulement de gaz peut être améliorée.
PCT/CN2018/106921 2018-07-27 2018-09-21 Structure de spoiler appliquée à un traitement de gaz de queue et mélangeur scr composite Ceased WO2020019463A1 (fr)

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