CN215213650U - Urea supersonic jet ejector structure and SCR tail gas emission post-treatment system - Google Patents
Urea supersonic jet ejector structure and SCR tail gas emission post-treatment system Download PDFInfo
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- CN215213650U CN215213650U CN202120886727.XU CN202120886727U CN215213650U CN 215213650 U CN215213650 U CN 215213650U CN 202120886727 U CN202120886727 U CN 202120886727U CN 215213650 U CN215213650 U CN 215213650U
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Abstract
The utility model discloses a urea supersonic speed efflux sprayer structure and engine SCR exhaust emissions after-treatment system, include: a first-stage injection mechanism for metering and injecting urea; a secondary injection mechanism for atomizing the metered urea; and a closed mixing cavity is formed between the first-stage injection mechanism and the second-stage injection mechanism, and the mixing cavity is arranged to be capable of additionally introducing fluid to be mixed with the injected urea to form mixed fluid and immediately sprayed out by the second-stage injection mechanism. The utility model discloses a system comprises above-mentioned structure, can atomize into the very little liquid drop of particle diameter with urea under the low pressure, can reduce urea pump delivery pressure in using to reduce system cost and improve system reliability, shorten urea gasification stroke, reduce urea crystallization on the blast pipe, the unreacted urea of lowering system discharges, improves catalyst converter conversion efficiency simultaneously, solves the problem that urea atomization difficulty causes the NOx oxynitrides conversion rate to hang down.
Description
Technical Field
The utility model relates to a tail gas after treatment system technical field, more specifically say, the utility model relates to a urea supersonic speed efflux sprayer structure and SCR exhaust-gas emission after treatment system.
Background
The implementation of the national six puts forward higher requirements on the treatment effect of the engine tail gas treatment system.
In the engine tail gas treatment system, the engine tail gas is discharged into an exhaust pipe, a urea pump provides urea solution, an electronic control unit controls an injection mechanism to mix metered urea and gas to form mixed fluid based on signals of a sensor, the mixed fluid is sprayed and atomized and injected into the exhaust pipe, the urea is decomposed into ammonia gas under high temperature, the ammonia gas and the tail gas are fully mixed and then enter a catalytic converter to carry out catalytic reduction reaction, and finally NOx compounds in the tail gas are reduced into nitrogen and water to be discharged.
The NOx compound in the tail gas is dynamically changed in real time, the urea correspondingly metered is also dynamically changed, and after an injection signal is sent out, the higher the injection speed of an injection mechanism is, the higher the response speed is, the lower the time delay is, and the better the tail gas treatment effect is.
However, in the conventional engine exhaust gas treatment system, the urea has a very large stroke from mixing with the gas to injection, and the delayed injection is very serious, thereby affecting the exhaust gas treatment effect.
SUMMERY OF THE UTILITY MODEL
It is an object of the present invention to address at least the above-mentioned deficiencies and to provide at least the advantages which will be explained later.
Another object of the utility model is to provide a urea supersonic speed efflux sprayer structure of compriseing urea sprayer and atomizing sprayer, this structure has the mixing chamber that urea and air current mix coarsely, and atomizing sprayer utilizes the pipeline structure of ultrasonic wave or earlier shrink back expansion to make the urea atomizing simultaneously, still can be with the urea atomizing very little liquid drop of particle diameter under the low pressure output condition, improves the tail gas treatment effect, improves urea injection response speed and injection accuracy.
Another object of the present invention is to provide a back pressure adjusting structure, which can stabilize the back pressure of the urea solution supply side and the compressed gas supply side.
Another object of the utility model is to provide a urea solution feed system, compressed gas feed system, electrical unit, catalyst converter and urea supersonic speed efflux sprayer form a novel SCR tail gas aftertreatment system, atomize into the little liquid drop of particle diameter with urea under the low pressure, reduce system cost and improvement system reliability shorten urea gasification stroke, reduce urea crystallization on the blast pipe, the unreacted urea of reducing system discharges, improves catalyst converter conversion efficiency simultaneously.
In order to solve the technical problem, the utility model provides a following technical scheme:
a urea supersonic jet injector arrangement comprising:
a first-stage injection mechanism for metering and injecting urea;
a secondary injection mechanism for atomizing the metered urea;
an airtight mixing cavity is formed between the first-stage injection mechanism and the second-stage injection mechanism, and an inlet of the mixing cavity is provided with a mixed fluid which can be formed by additionally introducing fluid and urea injected by the first-stage injection mechanism and then is directly injected by the second-stage injection mechanism.
The technical scheme is designed aiming at the problems of overlong urea injection stroke and poor urea atomization effect of the injection mechanism in the prior art, and comprises a primary injection mechanism for urea metering and a secondary injection mechanism for urea atomization metering, wherein the metered urea is firstly injected into a mixing cavity to be mixed with fluid to form primary atomization, and then is sprayed into external environments such as an exhaust pipe and the like through the secondary injection mechanism to form secondary atomization; meanwhile, the mixing cavity can be filled with fluid to be mixed with urea, the formed mixed fluid is directly sprayed out by the secondary mechanism, the atomization effect is good, the spraying stroke of the urea is shortened, the metered urea is rapidly sprayed and combined with tail gas, the response speed is improved, and the tail gas treatment effect is better.
Preferably, in the structure of the urea supersonic jet injector, the distance between the end face of the jet orifice of the primary injection mechanism and the end face of the inlet of the secondary injection mechanism is-50 mm.
In the technical scheme, the distance between the jet orifice and the inlet is extremely short, the sprayed metered urea enters the secondary injection mechanism immediately after being atomized for a short time and is sprayed out by the secondary injection mechanism, the process is very quick, the corresponding spraying speed is effectively improved, and the response time of the urea supersonic jet injector structure is less than 1 ms.
Preferably, in the structure of the urea supersonic jet injector, the arrangement of the primary injection mechanism and the secondary injection mechanism is as follows: the coaxial arrangement, the axial parallel arrangement, the axial cross arrangement or the axial space cross arrangement.
In the above technical solution, the specific arrangement of the first-stage injection mechanism and the second-stage injection mechanism may be set according to requirements, such as the size and shape of the installation space, the installation position, and the like, as long as a closed mixing chamber can be formed. The preferred arrangement mode is coaxial arrangement or crossed shaft arrangement, and the crossed angle is set according to requirements.
Preferably, in the structure of the urea supersonic jet injector, the two-stage injection mechanism is:
a: atomizing by accelerating the ejection of the fluid through at least one segment of a first constricted and then expanded conduit structure: or
B: promoting fluid atomization through an ultrasonic reaction unit; or
And (3) the combination of A and B.
In the prior art, the output pressure of a urea pump is set to be very high, and under a high-pressure condition, parts of an engine tail gas treatment system bear great pressure, so that the reliability is greatly reduced; and to match such high pressure conditions, engine exhaust treatment systems typically require intensive treatment, which undoubtedly increases production costs.
Above-mentioned technical scheme utilizes the one-level injection mechanism with the accurate measurement of urea and is used for the atomizing second grade injection mechanism combination of measurement urea, can guarantee that the urea measurement is accurate atomization effect good simultaneously, and under the lower backpressure condition, injection mechanism still can receive the atomization effect of ideal like this, solves the simple a series of problems that utilize the high pressure to improve atomization effect production of prior art.
Preferably, in the urea supersonic jet injector structure, the fluid ejected by the secondary injection mechanism reaches supersonic speed or approaches supersonic speed by controlling the pressure of the additional fluid introduced into the mixing cavity or the number of the contraction-expansion ratio of the first-contraction-later-expansion pipeline structure or the combination of the contraction-expansion ratio of the first-contraction-later-expansion pipeline structure and the third-contraction-later-expansion pipeline structure.
According to the technical scheme, the purpose of improving the fluid injection speed is achieved by utilizing the input pressure or the pipe diameter expansion and contraction diameter ratio or the number of expansion and contraction pipelines, the supersonic urea mixture jet flow comes into the external tail gas air to form huge speed difference and pressure difference with the external tail gas air, the high-speed gas can form shearing force on the liquid surface, the liquid can be broken and decomposed into countless small droplets, finally spray with very small particle size is formed, the urea solution with very good atomization can be more quickly decomposed into ammonia gas in the exhaust pipe, meanwhile, the urea solution is more fully mixed with the tail gas, and the conversion rate of the tail gas NOx oxynitride is greatly improved.
Preferably, the urea supersonic jet injector structure further comprises a pressure regulating unit connected to a urea input end of the primary injection mechanism and a fluid inlet end of the mixing cavity, and the pressure regulating unit is used for stabilizing the pressure of the introduced urea and the pressure of the introduced fluid respectively;
wherein:
the pressure regulating unit is a single pressure regulating valve which uses the pressure at the fluid inlet end of the mixing cavity to balance the pressure at the urea input end of the primary injection mechanism so as to form a stable back pressure regulating structure;
or the pressure regulating unit is a plurality of pressure regulating valves which respectively regulate the pressure of the fluid inlet end of the mixing cavity and the pressure of the urea input end of the primary injection mechanism.
Among the above-mentioned technical scheme, set up the air-vent valve at urea input and fluid input end, the stable backpressure of urea input and fluid input end is established to the air-vent valve for one-level injection mechanism can the accurate measurement urea, and under the hybrid chamber kept the steady pressure state, second grade injection mechanism can improve atomization effect with measuring the high-speed blowout of urea.
Engine SCR exhaust emission after-treatment system includes:
at least one said urea supersonic jet injector arrangement;
a urea solution supply system that feeds urea to the urea supersonic jet injector structure;
a compressed gas supply system that feeds fluid into a mixing chamber of a urea supersonic jet injector arrangement;
and the catalyst is used for providing a reaction space for the tail gas and the fluid sprayed by the urea supersonic jet injector structure.
The technical scheme can atomize the urea into liquid drops with very small particle size under low pressure, and can reduce the output pressure of the urea pump in application, thereby reducing the system cost and improving the system reliability, simultaneously shortening the urea gasification stroke, reducing the crystallization of the urea on an exhaust pipe, reducing the unreacted urea emission of the system, improving the conversion efficiency of a catalyst, solving the problem of low conversion rate of NOx nitrogen oxides caused by difficult urea atomization, and providing a brand new and reliable technical idea and solution for meeting strict emission regulations by the system.
Preferably, the engine SCR tail gas emission aftertreatment system further comprises an electric control unit electrically connected with the urea supersonic jet injector structure, and the electric control unit receives an operation condition signal of the diesel engine and controls the urea injection amount of the primary injection mechanism according to the operation condition signal.
Preferably, in the SCR exhaust emission aftertreatment system of an engine, the pressure regulating unit in the urea supersonic jet injector structure is a single pressure regulating valve, the pressure regulating valve is connected to the fluid inlet of the mixing chamber and the urea inlet of the primary injection mechanism, and the pressure regulating valve is configured to balance the pressure at the fluid inlet by using the pressure at the fluid inlet.
Preferably, in the SCR exhaust emission aftertreatment system of an engine, the fluid ejected by the secondary injection mechanism reaches supersonic speed or approaches supersonic speed by controlling the additional fluid pressure introduced into the mixing cavity of the urea supersonic jet injector structure, or the contraction/expansion ratio of the first-contraction and then-expansion pipe structures, or the number of the first-contraction and then-expansion pipe structures, or the combination of the three.
The purpose of improving the fluid injection speed is achieved by utilizing the input pressure or the pipe diameter expansion and contraction diameter ratio or the number of expansion and contraction pipelines, the supersonic urea mixture jet flow comes into the external tail gas air to form huge speed difference and pressure difference with the external tail gas air, the high-speed gas can form shearing force on the liquid surface, the liquid can be broken and decomposed into a plurality of small droplets, finally spray with very small particle size is formed, the urea solution with very good atomization can be quickly decomposed into ammonia gas in the exhaust pipe, meanwhile, the urea solution is mixed with the tail gas more fully, and the conversion rate of the tail gas NOx oxynitride is greatly improved.
Preferably, in the engine SCR exhaust emission aftertreatment system, the pressure regulating unit is communicated to a urea solution supply system to discharge the urea solution overflowing under pressure back.
The engine SCR tail gas emission after-treatment method comprises the following steps:
the urea solution with stable pressure is metered by the primary injection mechanism and then injected into the mixing cavity;
introducing air flow into the mixing cavity and establishing certain pressure;
accelerating and/or applying ultrasonic action to the mixed fluid in the mixing cavity through a secondary spraying mechanism to form spray;
the spray is mixed and reacted with tail gas generated by an engine;
the mixing cavity is constructed in a mode that the primary injection mechanism and the secondary injection mechanism are coaxially connected in an end mode or are not coaxially connected in a cross mode so as to reduce the volume of the mixing cavity and the stroke of the urea solution, and the metered urea solution is rapidly sprayed out to be mixed with tail gas.
Or the first-stage injection mechanism and the second-stage injection mechanism are coaxially arranged or axially arranged in parallel or axially crossed or axially arranged in a spatial crossed manner, and the distance between the end face of the injection port of the first-stage injection mechanism and the end face of the inlet of the second-stage injection mechanism is limited to be-50 mm, so that the stroke of the urea solution is shortened, and the metered urea is rapidly sprayed out and mixed with tail gas.
In the technical scheme, the urea solution with stable pressure enables urea to be accurately metered by the primary injection mechanism, the metered urea is injected into the mixing cavity to form primary atomization, and then the primary atomization is injected from the secondary injection mechanism under certain pressure, so that a better atomization effect is achieved; meanwhile, the mixing cavity is very small due to the butt joint mode of the primary injection mechanism and the secondary injection mechanism, the metering urea and the air flow are quickly sprayed out by the secondary injection mechanism after being mixed and are mixed with the tail gas, the response speed is improved, and the tail gas treatment effect is good.
And the distance between the jet orifice and the inlet of the first-stage jet mechanism and the second-stage jet mechanism is extremely short, the jet is correspondingly fast, the response time can reach below 1 ms, and the effect is good.
Furthermore, the venturi structure pipeline is arranged in the secondary injection mechanism, so that the mixed fluid is sprayed out at supersonic speed, and the atomization effect is improved.
The utility model discloses at least, include following beneficial effect:
the utility model discloses to the problem that the urea injection stroke of prior art injection mechanism is overlength, urea atomization effect is not good, designed the one-level injection mechanism that is used for carrying on the urea measurement and be used for the second grade injection mechanism that will measure the urea atomizing, the urea that measures is sprayed into the mixing chamber at first and is mixed with the fluid and form preliminary atomization, then spout in external environment such as blast pipe through second grade injection mechanism and form the secondary atomization again, such structure makes the urea measurement accurate, and atomization effect is good; meanwhile, the mixing cavity is limited to be capable of introducing fluid to mix with urea and is sprayed out by the secondary mechanism immediately, the spraying stroke of the urea is shortened, the metered urea is sprayed rapidly and is combined with tail gas, the response speed is improved, and the tail gas treatment effect is better. The utility model discloses the utilization is with the one-level injection mechanism of urea accurate measurement and is used for measuring the atomizing second grade injection mechanism combination of urea, can guarantee that the accurate atomization effect is good simultaneously of urea measurement, and under lower backpressure condition, injection mechanism still can receive the atomization effect of ideal like this, solves a series of problems that prior art simply utilized high pressure to improve atomization effect and produce.
The utility model discloses a system can atomize into the very little liquid drop of particle size with urea under the low pressure, can reduce urea pump delivery pressure in using, thereby reduce system cost and improve system reliability, shorten urea gasification stroke simultaneously, reduce urea crystallization on the blast pipe, the unreacted urea of lowering system discharges, improve catalyst converter conversion efficiency, solve urea atomizing difficulty and cause the problem that NOx oxynitrides conversion rate is low, this system provides brand-new reliable technical thought and solution for satisfying harsh emission regulations.
The utility model provides an utilize one-level injection mechanism and second grade injection mechanism to found and form narrow hybrid chamber, improve atomization effect and spray response speed's conception.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Drawings
FIG. 1 is a schematic structural view of a urea supersonic jet ejector structure according to the present invention;
FIG. 2 is the structure schematic diagram of the engine SCR tail gas emission after-treatment system of the utility model:
fig. 3-9 are the arrangement mode illustration of the first-level injection mechanism and the second-level injection mechanism of the present invention.
In the figure: the system comprises an engine 1, a urea tank 2, a filter screen 3, a urea pump 4, a pressure regulating valve 5, a compressed air supply tank 6, an air switch valve 7, an electronic control unit 8, a urea injector 9, an atomizing injector 10, an injector cooling water jacket 11, a catalyst 12, an exhaust pipe 13, an air delivery pipe 14, a urea delivery pipe 15, a urea injector circuit 16, an atomizing injector circuit 17, an air switch valve driving circuit 18, a urea pump driving circuit 19, a urea supersonic jet atomizing injector 20, a mixing cavity 201, a primary injection mechanism 202, a secondary injection mechanism 203, an inlet 204 of the primary injection mechanism, an outlet 205 of the secondary injection mechanism, a urea input end 206, a fluid inlet 207, a pressure regulating unit 208, a fluid input end 209, an overflow port 2010, an injection port of the primary injection mechanism 2021 and an inlet of the secondary injection mechanism 2031.
Detailed Description
The present invention is further described in detail below with reference to examples so that those skilled in the art can implement the invention with reference to the description. It is to be understood that the embodiments described are only some embodiments of the invention, and not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.
Example 1
Fig. 1 shows an embodiment of the present invention, a urea supersonic jet injector structure, comprising:
a primary injection mechanism 202 that performs metered injection of urea;
a secondary injection mechanism 203 for atomizing the metered urea;
a closed mixing cavity 201 is formed between the first-stage injection mechanism 202 and the second-stage injection mechanism 203, and the mixing cavity 201 is set to be capable of introducing fluid additionally to be mixed with urea injected by the first-stage injection mechanism to form mixed fluid and then directly injected by the second-stage injection mechanism.
In order to realize that the mixing chamber can be filled with fluid, the mixing chamber is generally provided with a fluid inlet 207, and the function of the mixing chamber is mainly to provide a space for metering the mixing of urea and fluid, so that on the premise of ensuring the mixing, the jet orifice of the first-stage injection mechanism and the inlet of the second-stage injection mechanism are as close as possible, and the shape and the structure of the mixing chamber 201 can be set according to requirements, such as a flat structure, a long and narrow structure and a multi-stage stepped structure, fig. 1 shows an implementation structure of the present case, wherein the jet orifice of the first-stage injection mechanism 202 is coaxially butted with the inlet of the second-stage injection mechanism 203, and the mixing chamber 201 is formed at the butted position, and certainly, on the premise of ensuring the jet orifice of the first-stage injection mechanism 202 and the inlet butted structure of the second-stage injection mechanism 203, the shape of the mixing chamber is randomly changed. 3-9 show other arrangement modes of the primary injection mechanism and the secondary injection mechanism, and the primary injection mechanism and the secondary injection mechanism are arranged in a vertical and crossed mode in the axial direction in the figure 3; FIG. 4 is an axial cross but not perpendicular angular arrangement; FIG. 5 is axially spatially vertical; FIG. 6 is an axial parallel; FIG. 7 is axially parallel but in the opposite direction; FIG. 8 is a view showing the coaxial arrangement but with the inlet of the secondary injection mechanism recessed and the injection port of the primary injection mechanism inserted therein; in fig. 9, the ejection port is sunk inside the inlet of the secondary ejection mechanism, and the distance to the inlet of the secondary ejection mechanism is negative. Of course, there are other arrangements, which are not listed in this document.
The embodiment is designed for solving the problems of long urea injection stroke and poor urea atomization effect of the injection mechanism in the prior art, and comprises a primary injection mechanism 202 for urea metering and a secondary injection mechanism 203 for urea atomization metering, wherein urea supplied by a urea input end is accessed from an inlet 204 of the primary injection mechanism, the primary injection mechanism meters and injects the urea into a mixing cavity 201 to be mixed with fluid to form primary atomization, and then the urea is sprayed into external environments such as an exhaust pipe and the like through an outlet 205 of the secondary injection mechanism to form secondary atomization, so that the urea metering is accurate and the atomization effect is good; meanwhile, the mixing cavity is limited to be capable of introducing fluid to mix with urea and is sprayed out by the secondary mechanism immediately, the spraying stroke of the urea is shortened, the metered urea is sprayed rapidly and is combined with tail gas, the response speed is improved, and the tail gas treatment effect is better.
Example 2
In addition to embodiment 1, as shown in fig. 1 and 3 to 9, in the structure of the urea supersonic jet injector, the distance between the end surface of the jet port 2021 of the primary injection mechanism 202 and the end surface of the inlet 2031 of the secondary injection mechanism 203 is-50 mm to 50 mm, and no matter how the primary injection mechanism and the secondary injection mechanism are spatially arranged, the distance between the end surface of the jet port of the primary injection mechanism and the end surface of the inlet of the secondary injection mechanism can be-50 mm to 50 mm.
Example 3
On the basis of embodiment 1, as shown in fig. 1 and 3 to 9, in the structure of the urea supersonic jet injector, the arrangement mode of the primary injection mechanism and the secondary injection mechanism is as follows: the coaxial arrangement, the axial parallel arrangement, the axial cross arrangement or the axial space cross arrangement. In FIG. 3, the axial direction is arranged perpendicularly and crosswise; FIG. 4 is an axial cross but not perpendicular angular arrangement; FIG. 5 is axially spatially vertical; FIG. 6 is an axial parallel; FIG. 7 is axially parallel but in the opposite direction; FIG. 8 is a view showing the coaxial arrangement but with the inlet of the secondary injection mechanism recessed and the injection port of the primary injection mechanism inserted therein; in fig. 9, the ejection port is sunk inside the inlet of the secondary ejection mechanism, and the distance to the inlet of the secondary ejection mechanism is negative. Of course, there are other arrangements, and the embodiments are not listed.
Example 4
Based on embodiments 2 and 3, as shown in fig. 1 and 3 to 9, the arrangement of the primary injection mechanism and the secondary injection mechanism in embodiment 3 is combined on the basis of ensuring that the distance between the end surface of the injection port 2021 of the primary injection mechanism 202 and the end surface of the inlet 2031 of the secondary injection mechanism 203 is-50 mm to 50 mm.
Example 5
On the basis of embodiment 1, further, in another embodiment, the secondary injection mechanism 203 is configured to:
a: atomizing by accelerating the ejection of the fluid through at least one segment of a first constricted and then expanded conduit structure: or
B: promoting fluid atomization through an ultrasonic reaction unit; or
And (3) the combination of A and B.
More specifically, the atomizing effect that measures the urea is better, and the tail gas treatment effect that brings is better, and for improving the atomizing effect that measures the urea, second grade injection mechanism can design for at least one section earlier the pipeline structure that contracts afterwards to expand, according to the venturi effect, such structure can effectively improve the fluid jet speed, and during high-speed efflux sprayed tail gas air, the urea in the efflux was cut and is formed very little urea granule, and then with tail gas intensive mixing, reaches the purpose that improves tail gas treatment effect.
Meanwhile, the urea can be atomized and metered by ultrasonic waves generated by the ultrasonic reaction unit, the ultrasonic reaction unit can be arranged in the secondary injection mechanism and can also be arranged outside the secondary injection mechanism, and the ultrasonic waves are transmitted along the secondary injection mechanism so as to atomize the passing or sprayed metered urea.
Furthermore, the pipeline structure which is contracted and expanded firstly can be combined with the ultrasonic reaction unit to improve the atomization effect. For example, the secondary injection mechanism is arranged in a pipeline structure which is firstly contracted and then expanded, and the ultrasonic reaction unit is arranged at the front end or the middle end or the rear end of the secondary injection mechanism.
The embodiment can still obtain good atomization effect under the condition of ensuring lower back pressure. Under the condition of low back pressure, the pressure born by the parts is greatly reduced, the reliability of the system is ensured, the service life is prolonged, and the cost is reduced.
Further, in another embodiment, the fluid ejected from the secondary ejection mechanism 203 can reach supersonic speed or near supersonic speed by controlling the pressure of the additional fluid introduced into the mixing cavity 201 or the contraction-expansion ratio of the first-contraction-later-expansion pipeline structure or the number of the first-contraction-later-expansion pipeline structures or the combination of the three.
The supersonic urea mixture jet flow comes into the external tail gas air to form huge speed difference and pressure difference with the external tail gas air, the high-speed gas can form shearing force on the liquid surface, the liquid can be broken and decomposed into numerous small droplets, finally spray with very small particle size is formed, the urea solution with very good atomization can be decomposed into ammonia gas in the exhaust pipe more quickly, meanwhile, the urea solution is mixed with the tail gas more fully, and the conversion rate of the tail gas NOx nitrogen oxides is greatly improved.
Further, in another embodiment, the device further comprises a pressure regulating unit 208 connected to the urea input end 206 of the primary injection mechanism 202 and the fluid inlet end 209 of the mixing cavity 201, for stabilizing the pressure of the introduced urea and the pressure of the introduced fluid respectively;
wherein:
the pressure regulating unit 208 is a single pressure regulating valve, and the pressure regulating valve uses the pressure at the fluid inlet end of the mixing cavity to balance the pressure at the urea inlet end of the primary injection mechanism so as to form a stable back pressure regulating structure; fig. 1 shows a single pressure regulating valve configuration, where one end of the pressure regulating valve is connected to the fluid input 209 and the other end is connected to the urea input 206, and the pressure regulating valve is provided with an overflow port 2010 to release the overflowing urea, ensuring stable input pressure to the primary injection mechanism.
Or the pressure regulating unit is a plurality of pressure regulating valves which respectively regulate the pressure of the fluid inlet end 209 of the mixing cavity and the pressure of the urea inlet end 206 of the primary injection mechanism.
According to the embodiment, the pressure regulating valve 208 is arranged at the urea input end 206 and the fluid input end 209, stable back pressure is built by the pressure regulating valve, so that the primary injection mechanism can accurately measure urea, and the secondary injection mechanism can spray the measured urea at a high speed under the condition that the mixing cavity keeps a stable pressure state, so that the atomization effect is improved.
Example 6
Fig. 2 shows an embodiment of the SCR exhaust emission after-treatment system of the present invention, comprising:
at least one urea supersonic jet injector configuration of either embodiment 1 or embodiment 2;
a urea solution supply system that feeds urea to the urea supersonic jet injector structure;
a compressed gas supply system that feeds fluid into a mixing chamber of a urea supersonic jet injector arrangement;
and the catalyst is used for providing a reaction space for the tail gas and the fluid sprayed by the urea supersonic jet injector structure.
The embodiment can atomize urea into liquid drops with very small particle sizes under low pressure, can reduce the output pressure of a urea pump in application, thereby reducing the system cost and improving the system reliability, simultaneously shortening the urea gasification stroke, reducing the crystallization of urea on an exhaust pipe, reducing the unreacted urea emission of the system, improving the conversion efficiency of a catalyst, and solving the problem of NO caused by difficult urea atomizationxThe problem of low nitrogen oxide conversion rate, and the system provides a brand new and reliable technical idea and solution for meeting strict emission regulations.
Further, in another embodiment, the device further comprises an electronic control unit electrically connected with the urea supersonic jet injector structure, wherein the electronic control unit receives the operating condition signal of the diesel engine and controls the urea injection amount of the primary injection mechanism according to the operating condition signal.
Further, in another embodiment, the pressure regulating unit in the urea supersonic jet injector structure is a single pressure regulating valve, the pressure regulating valve is connected to the fluid inlet of the mixing chamber and the urea inlet of the primary injection mechanism, and the pressure regulating valve is configured to balance the pressure at the fluid inlet by using the pressure at the fluid inlet.
Further, the pressure regulating unit is communicated to the urea solution supply system and used for discharging the urea solution which overflows after pressure regulation back.
For a better understanding and implementation, the following details are provided: as shown in fig. 2, when the engine 1 normally operates, exhaust gas is generated, the exhaust gas enters the exhaust pipe 13, the pressure regulating valve 5, the urea injector 9 (primary injection mechanism), the atomizing injector 10 (secondary injection mechanism) and the injector cooling water jacket 11 form a urea supersonic jet atomizing injector 20, the urea supersonic jet atomizing injector 20 atomizes the urea solution and injects the urea solution into the exhaust pipe, the urea decomposes into ammonia gas at high temperature, the ammonia gas and the exhaust gas are fully mixed and enter the catalyst 12 together for catalytic reduction reaction, and finally, NOx compounds in the exhaust gas are reduced into nitrogen and water for being discharged.
The electronic control unit 8 calculates urea injection quantity according to the operating conditions (parameters such as rotating speed, torque, environment, pressure and temperature) of the engine, so as to drive the urea pump 4 to build pressure through a urea pump driving circuit 19, the urea pump 4 filters the urea solution stored in the urea tank 2 through a filter screen 3 and then transports the urea solution to a urea supersonic jet atomizing injector 20 through a urea delivery pipe 15, the urea injector 9 is electrically connected with the electronic control unit 8 through a urea injector circuit 16, the atomizing injector is electrically connected with the electronic control unit through an atomizing injector circuit 17, meanwhile, the electronic control unit 8 drives an air switch valve 7 to open through an air switch valve driving circuit 18, compressed air with certain pressure is transported to the urea supersonic jet atomizing injector 20 through an air delivery pipe 14 from a compressed air supply tank 6, and the urea solution and the compressed air can be adjusted through a pressure adjusting valve 5 to form stable back pressure, the urea solution and the compressed air are fully mixed in the urea supersonic jet atomizing injector 20, and the urea supersonic jet atomizing injector 20 measures and atomizes the urea solution to be injected into the exhaust pipe.
The utility model discloses engine SCR exhaust emission after treatment system's theory of operation does: the engine 1 supplies urea solution and compressed air to the urea supersonic jet atomization injector 20 through a urea supply system and an air supply system, the urea supersonic jet atomization injector 20 measures and atomizes urea and then injects the urea into an exhaust pipe, and tail gas and ammonia gas after urea decomposition are fully mixed and then enter the catalyst 12 to complete catalytic reduction reaction; the urea supersonic jet atomizing injector 20 is composed of a pressure regulating valve 5, a urea injector 9, an atomizing injector 10 and an injector cooling water jacket 11, wherein the urea injector 9 is responsible for metering urea and injecting the urea into a mixing cavity 201, compressed air is fully mixed with urea solution in the mixing cavity 201, the mixture enters the atomizing injector 10 with a pipeline structure which contracts and expands firstly to generate supersonic airflow, the mixed urea solution forms an acceleration effect through a supersonic acceleration structure, the speed can reach a supersonic state, a high-speed urea gas-liquid mixture leaves the urea supersonic jet injector 20 and then comes into the outside air to form huge speed difference and pressure difference with the outside air, the high-speed gas can form shearing force on the surface of the liquid, the liquid can break and decompose into numerous small droplets, and finally spray with a very small particle size is formed, the urea solution with good atomization can be decomposed into ammonia gas in the exhaust pipe more quickly, and simultaneously, the urea solution is mixed with tail gas more fully, so that the conversion rate of NOx nitrogen oxides in the tail gas is greatly improved.
Example 7
The mixing cavity is constructed in a mode that the primary injection mechanism and the secondary injection mechanism are coaxially connected in an end mode or are not coaxially connected in a cross mode so as to reduce the volume of the mixing cavity and the stroke of the urea solution, and the metered urea solution is rapidly sprayed out to be mixed with tail gas.
Or the first-stage injection mechanism and the second-stage injection mechanism are coaxially arranged or axially arranged in parallel or axially crossed or axially arranged in a spatial crossed manner, and the distance between the end face of the injection port of the first-stage injection mechanism and the end face of the inlet of the second-stage injection mechanism is limited to be-50 mm, so that the stroke of the urea solution is shortened, and the metered urea is rapidly sprayed out and mixed with tail gas.
In the technical scheme, the urea solution with stable pressure enables urea to be accurately metered by the primary injection mechanism, the metered urea is injected into the mixing cavity to form primary atomization, and then the primary atomization is injected from the secondary injection mechanism under certain pressure, so that a better atomization effect is achieved; meanwhile, the mixing cavity is very small due to the butt joint mode of the primary injection mechanism and the secondary injection mechanism, the metering urea and the air flow are quickly sprayed out by the secondary injection mechanism after being mixed and are mixed with the tail gas, the response speed is improved, and the tail gas treatment effect is good.
And the distance between the jet orifice and the inlet of the first-stage jet mechanism and the second-stage jet mechanism is extremely short, the jet is correspondingly fast, the response time can reach below 1 ms, and the effect is good.
The urea solution with stable pressure in the implementation can ensure that urea can be accurately metered by the primary injection mechanism, the metered urea is injected into the mixing cavity to form primary atomization, and then the urea is injected from the secondary mechanism under certain pressure to achieve better atomization effect; meanwhile, the mixing cavity is very small due to the butt joint mode of the primary injection mechanism and the secondary injection mechanism, the metering urea and the air flow are quickly sprayed out by the secondary injection after being mixed and are mixed with the tail gas, the response speed is improved, and the tail gas treatment effect is good.
Further, in another embodiment, a venturi structure pipeline is arranged in the secondary spraying mechanism, so that the mixed fluid is sprayed out at a supersonic speed, and the atomization effect is improved.
Analysis of experiments
Inputting a urea solution into a primary injection mechanism at 750 Kpa pressure and inputting gas into a mixing cavity at 500 Kpa pressure according to the structure of the urea supersonic jet injector shown in the figure 1 in the embodiment 1, and then testing the atomization effect and the response time of injection; the measurement result shows that the atomized particle diameter is 10-20 um (Sortell mean diameter) and the response time is 0.7-1 ms. Under the condition of the same input pressure, the atomization particle size of a traditional urea injection system is 30-50 um, and the response time is 3-5 ms.
The atomization effect is tested by an atomization particle size testing instrument, and the response time is the time from the time when the injector inputs an injection signal to the time when the urea is sprayed out.
While embodiments of the invention have been disclosed above, it is not intended to be limited to the applications listed in the specification and the examples. It can be applicable to various and be fit for the utility model discloses a field completely. Additional modifications will readily occur to those skilled in the art.
Claims (9)
1. Urea supersonic jet ejector structure, characterized by, comprising:
a first-stage injection mechanism for metering and injecting urea;
a secondary injection mechanism for atomizing the metered urea;
an airtight mixing cavity is constructed between the first-stage injection mechanism and the second-stage injection mechanism, and an inlet is formed in the mixing cavity to additionally introduce fluid to be mixed with urea injected by the first-stage injection mechanism to form mixed fluid which is then directly injected by the second-stage injection mechanism.
2. The urea supersonic jet injector structure of claim 1, wherein the distance between the injection port end surface of the primary injection mechanism and the inlet end surface of the secondary injection mechanism is-50 mm.
3. The urea supersonic jet injector structure of claim 1, wherein the arrangement of the primary injection mechanism and the secondary injection mechanism is as follows: the coaxial arrangement, the axial parallel arrangement, the axial cross arrangement or the axial space cross arrangement.
4. The urea supersonic jet injector structure of claim 1, wherein said secondary injection mechanism is provided with:
a: at least one segment of the pipe structure which contracts and expands firstly so as to accelerate the ejection of the fluid for atomization: or
B: the ultrasonic reaction unit promotes fluid atomization; or
And (3) the combination of A and B.
5. The urea supersonic jet injector structure of claim 1, further comprising a pressure regulating unit connected to a urea input of the primary injection mechanism and a fluid inlet of the mixing chamber for stabilizing a pressure of the introduced urea and a pressure of the introduced fluid, respectively;
wherein:
the pressure regulating unit is a single pressure regulating valve which is set to be a structure for balancing the pressure at the urea input end of the primary injection mechanism by using the pressure at the fluid inlet end of the mixing cavity so as to form stable back pressure regulation;
or the pressure regulating unit is a plurality of pressure regulating valves which are respectively used for regulating the pressure of the fluid inlet end of the mixing cavity and the pressure of the urea input end of the primary injection mechanism.
An SCR exhaust emission aftertreatment system, comprising:
a plurality of urea supersonic jet injector structures according to any one of claims 1 to 5;
the urea solution supply system is connected with the urea supersonic jet injector structure to inject urea;
a compressed gas supply system connected to the mixing chamber of the urea supersonic jet injector arrangement for the introduction of fluid;
and the catalyst is used for providing a reaction space for the tail gas and the fluid sprayed by the urea supersonic jet injector structure.
7. The SCR exhaust emission aftertreatment system of claim 6, further comprising an electronic control unit electrically connected to the urea supersonic jet injector structure, the electronic control unit configured to receive an operating condition signal from the diesel engine and control an urea injection amount of the primary injection mechanism according to the operating condition signal.
8. The SCR exhaust emission aftertreatment system of claim 6, wherein the contraction-to-expansion ratio of the first-contraction-to-expansion conduit structure is configured to achieve supersonic or near supersonic velocities based on fluid ejected by the secondary injection mechanism at an input pressure;
or the number of the first-contraction and second-expansion pipeline structures is set to be supersonic or nearly supersonic based on the fluid sprayed out by the secondary spraying mechanism under certain input pressure;
or, the two combine to achieve supersonic or near supersonic velocities based on the fluid ejected from the secondary ejection mechanism at a certain input pressure.
9. The SCR exhaust aftertreatment system of claim 6, wherein the pressure regulating unit is coupled to the urea solution supply system for back-draining the pressure-regulated overflow urea solution.
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| CN113090362B (en) * | 2021-04-27 | 2024-04-16 | 广西沃宾电子科技有限责任公司 | Urea supersonic jet ejector structure and engine SCR exhaust emission aftertreatment system |
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