The mixing arrangement of a kind of automobile-used urea SCR system
Technical field
Patent of the present invention relates to diesel exhaust aftertreatment system field, relates to the mixing arrangement of a kind of automobile-used urea SCR system in particular.
Background technique
Selective catalytic reduction (SCR) is one of the most effective post-processing technology of the minimizing Diesel NOx discharging of generally acknowledging at present, also is considered to meet most one of post-processing technology China's actual conditions, that can satisfy state IV emission request.Urea SCR is by spraying into the certain amount of urea aqueous solution in outlet pipe, aqueous solution of urea obtains reducing agent NH through pervaporation, pyrolysis and hydrolytic process again
3, NH
3Under the effect of catalyzer, optionally NOx is reduced into N
2Thereby realization reduces the content of NOx in the exhaust.The urea SCR post-processing technology is used the several years in Europe, is the mainstream technology route that Europe solves Europe IV/V emission request; In order to satisfy strict more EPA2010, most manufacturers of engines have been brought into use the SCR post-processing technology in the U.S.; Finished the urea SCR system that satisfies state IV Abgasgesetz in China main motor enterprise, and had increasing lift-launch SCR after-treatment system to satisfy the bus of state IV on Beijing, Shanghai and other places.
The urea SCR system of extensive use at present mainly is divided into two classes: air-assisted injection system and no air-assisted injection system.The general nozzle of the auxiliary SCR system of air is installed in the outlet pipe center, aqueous solution of urea vertically sprays around exhaust wall compressed-air actuated assisting down, and it is better relatively to atomize under the air booster action, is difficult for forming crystallization, but many one road pressurized air, the system architecture complexity; The electromagnetic valve type nozzle is generally installed at tube wall by the auxiliary SCR system of no air, sprays from exhaust wall one end along several angle towards the outlet pipe the other end, and this system global structure is simple, but atomizing and mixed effect are relatively poor, form urea crystals easily.
Studies show that in a large number mixer can make the urea spray droplet mix with exhaust more fully, improve mixing uniformity, accelerate the evaporation of urea droplets, promote the decomposition of urea, forming uniform ammonia distributes, thereby improve the transformation efficiency of NOx, reduce the growing amount of urea deposits thing under the low temperature, reduce ammonia and leak.Mixer design should be considered the characteristics of aqueous solution of urea spray discharge pattern, if mixer design can form strong flow-disturbing in spray effect the poorest jet expansion zone and the easy spraying that crystallization takes place over against the wall place according to the characteristics of spray discharge pattern, the mixed effect of mixer will be better so.
Summary of the invention
What the present invention will solve is the above-mentioned defective that prior art exists, its objective is: at the auxiliary SCR system of no air, spraying sprays to the form of the other end along exhaust wall one end, characteristic according to spraying, by air motion in the mixer rationalization outlet pipe, place and the easy spraying that crystallization take place the poorest in the jet expansion spraying form strong flow-disturbing over against the wall place, promote the mixed effect of reducing agent ammonia, the transformation efficiency of raising NOx, and reduce sedimental growing amount and ammonia leakage.
For realizing above purpose, the technological scheme that this patent adopts is:
The mixing arrangement of a kind of automobile-used urea SCR system, comprise body, mixer tab arrangement and nozzle, it is characterized in that described nozzle is tilting on the body wall, described mixer tab arrangement is near nozzle and be installed in spray nozzle front end, described mixer tab arrangement comprises 4 fins, wherein: constituted and the similar fluid passage of spray discharge pattern in the middle of first and second fins, described first fin and second fin have certain inclination and reverse towards the center region; The 3rd fin is a baffle plate shape structure, and near the tube wall setting, the direction of installation is vertical with spray axis, reverses towards wall simultaneously; The 4th fin is placed along the spray axis direction, by about one group of blade alternately reversing constitute.
Mixing arrangement of the present invention, because described first fin and second fin have certain inclination and reverse towards the center region, the fluid conduction in the zone that can arrive not spraying is in the fluid passage, strengthen the flow strength of spraying place, especially form strong flow-disturbing at nozzle exit, promote the even distribution of urea droplets.The 3rd fin of baffle plate shape, the wall direction that the past spraying of bootable segment fluid flow faces flows, and strengthens mobile distribution with promotion wall urea droplets herein, can reduce the wall crystalline polamer simultaneously.By about the 4th fin that constitutes of one group of blade alternately reversing, be used for further mixed atomizing drop.
The present invention not only can be so that the aqueous solution of urea of nozzle ejection and tail gas be mixed before entering the SCR catalyst converter fully, reduce the crystallization of urea at wall, compact structure is easy to processing and installation simultaneously, and its effect is verified through the computational analysis of special designs software.
According to the present invention, described body one end links to each other with exhaust duct by adpting flange, and the other end links to each other with rear end pipeline or catalyst converter.Thereby the present invention can link to each other with exhaust duct by dismountable mode.
According to the present invention, mixer is arranged on spray nozzle front end, has avoided deposition, crystallization on mixer, stops up the problem of exhaust duct.Nozzle location is located at the flow-disturbing active region, can allow aqueous solution of urea and tail gas mix fully.
The body of the mixing arrangement of automobile-used urea SCR of the present invention system adopts 304 or 304 above stainless steel materials making.
Description of drawings
Fig. 1 is the auxiliary urea SCR system schematic of no air.
Fig. 2 is a diesel exhaust gas pipeline system construction drawing.
Fig. 3 is the front view of mixer of the present invention.
Fig. 4 is the plan view of mixer of the present invention.
Fig. 5 is the structural representation of mixer tab arrangement of the present invention.
Fig. 6 is spray orifice spray discharge pattern figure.
Among the figure: 1, adpting flange; 2, body; 3, mixer tab arrangement; 4, nozzle; 5, mixer rear end pipeline; 6, catalyst converter; 7, catalyst carrier; 8, pipeline behind the catalyst converter; 9, adpting flange; 10, adpting flange; 11, spray axis; 12, spray discharge pattern; 13, fluid passage.
Embodiment
Contrast accompanying drawing below, by description to embodiment, to the specific embodiment of the present invention, for example: the effect of mutual alignment relation between the shape of each structure, structure and the each several part and annexation, each several part and working principle etc. are done further detailed explanation:
A kind of mixing arrangement that is used for diesel urea SCR system of the present invention, utilize mixer to gas flow channeling conduct in the automobile exhaust pipe, on nozzle exit, spray axis direction, spraying over against the strong flow-disturbing of the place of avoiding formation, impel aqueous solution of urea to mix with vehicle exhaust better, improve ammonia distributes in the outlet pipe uniformity and NO
XTransformation efficiency, thereby further reduce the content of NOx in the exhaust, can reduce the formation of urea crystals simultaneously.
With reference to Fig. 2, Fig. 3, the static mixer of diesel urea selective catalytic reduction device of the present invention, comprise body 2, mixer tab arrangement 3 and nozzle 4, described nozzle 4 is arranged on body 2 tube walls, spraying sprays to downstream along the upstream extremity of exhaust wall, and described mixer tab arrangement is near nozzle and be installed in spray nozzle front end.Described body 2 two ends link to each other with rear end pipeline 5 with exhaust duct by adpting flange 1,9 respectively.Described nozzle 4 is arranged on the downstream of body 3.
With reference to Fig. 4, Fig. 5, described mixer tab arrangement 3 mainly is made up of 4 fins, wherein constituted and the similar fluid passage of spray discharge pattern in the middle of the first fin 3-1 and the second fin 3-2, the fluid conduction that each fin 3-1,3-2 have certain inclination and reverse the zone that spraying is not arrived towards the center region is in the fluid passage, strengthen the flow strength of spraying place, especially form strong flow-disturbing at nozzle exit, promote the even distribution of urea droplets; The 3rd fin 3-3 is a baffle plate shape structure, be arranged near the tube wall place, the direction of installing is vertical with spray axis 11, reverse towards wall simultaneously, the guide portion fluid flows toward the wall direction that spraying faces, strengthen mobile distribution herein, can reduce the wall crystalline polamer simultaneously with promotion wall urea droplets; The 4th fin 3-4 places along spray axis 11 directions, by about one group of blade alternately reversing constitute, be used for further mixed atomizing drop.
Described mixer tab arrangement 3 is welded on the body 2.Described fluid passage is consistent with the spray axis direction.
Described body 2 adopts 304 stainless steel materials to make.
Above-mentionedly in conjunction with the accompanying drawings the present invention has been carried out exemplary description, but specific implementation of the present invention is not subjected to the restriction of aforesaid way.As long as adopted the improvement of the various unsubstantialities that design of the present invention and technological scheme carry out, or design of the present invention and technological scheme are directly applied to other occasion, all within protection scope of the present invention without improving.
Adopt technological scheme of the present invention, not only can improve the transformation efficiency of SCR, reduced the formation of urea crystals, can not produce very big pressure drop again so that the aqueous solution of urea of nozzle ejection and vehicle exhaust are mixed fully.