• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
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    • 专利摘要:
    ll Summary Injection system (2) for an internal combustion engine, where the system is adapted to inject a reducing agent (4) into an exhaust fume from the internal combustion engine. The system (2) comprises a single container (6) for the reducing agent (4), a pump (8) intended to pump the reducing agent (4) to an atomizing unit (12), which is adapted to generate an air gap (14) containing droplets of the reducing agent (4). . The system also comprises a sorting and filtering unit (16) adapted to sort the droplets in the liquid and filter out droplets which have a size exceeding an adjustable, predetermined first droplet size limit. the container via a return pipe (24). (Fig. 1)
    公开号:SE1150948A1
    申请号:SE1150948
    申请日:2011-10-13
    公开日:2013-04-14
    发明作者:Daniel Norling；Torbjoern Eliassen
    申请人:Scania Cv Ab；
    IPC主号:
    专利说明:

    To achieve the described NOX reduction, NH 3 must be stored in the SCR catalyst. For the SCR catalyst to work efficiently, the storage level must be at an adequate level. In more detail, the NOX reduction, or conversion efficiency, depends on the storage level. In order to maintain a high conversion efficiency under different operating conditions, the NH 3 layer must be maintained. However, as the temperature of the SCR catalyst increases, the NH 3 level must be reduced in order to avoid NH 2 emissions (ie excess NH 3 is emitted from the SCR catalyst), which may reduce the conversion efficiency of the catalyst.
    In summary, in order to meet stricter environmental requirements, all your vehicle manufacturers use SCR catalytic converter systems to purify diesel exhaust gases from nitrogen oxides (N OX). This is done by injecting ammonia solution into an SCR catalyst that helps convert NOX particles into nitrogen and water. The exhaust gas purification strategy should take into account that sufficient NOX is converted while not wanting to inject too much ammonia, for both the driving economy and the environment.
    The exhaust gas temperature should normally be in the range 400-500 ° C for the reducing agent to evaporate and for the subsequent catalyst to function optimally.
    It has been noted that when injecting a reducing agent at low exhaust fumes and low temperatures, the agent does not have time, e.g. urea, to evaporate but stick to the evaporation wall and begin to grow into the urea. If this growth is allowed to continue, the function will deteriorate because the exhaust gases do not emerge.
    One reason for this is that the injected reducing agent has different droplets. If the urea droplets are too large, this leads to lump formation and that, for example, the urea is formed in connection with the evaporating part, which can cause operational disturbances in the worst case, downtime.
    The desired size of the droplets depends on the temperature of the exhaust gas. In connection with the engine being cold, and the temperature of the exhaust gases being lower, the droplets need to be relatively smaller than when the exhaust gas temperature is higher.
    The size of the droplets is normally in the range of 10-200 μm, and it is desirable that they be 20 μm or less and preferably about 10 μm.
    The exhaust gas velocity can be up to 100 ni / s, and the droplets are added at a rate of about 1-20 ni / s and injected at a pressure of about 10 bar. If the droplets are too small, it is difficult to push them into the exhaust stream.
    The size of the droplets is thus important, and also that they are relatively equal in size, in order to achieve an even distribution of the ammonia cloud which is formed in the exhaust gas stream and which is to hit the catalyst.
    It would be possible to achieve a better control of the droplet size so that only small droplets are generated, but this requires an expensive injection system, and which also requires a high mechanical effect.
    The object of the present invention is to provide an improved injection system for reducing agents with an improved control of the droplet size and which only generates small droplets without using a costly and energy-intensive injection system.
    Summary of the invention The above objects are achieved by the invention defined by the independent claim.
    Preferred embodiments are claimed by the dependent claims.
    The present invention is based on the inventors' insight to solve the problem by sizing and filtering the droplets so that the small droplets are used and the large ones are returned to the container.
    According to various embodiments, the so-called inertial impaction, electrostatic sizing, or centrifugation is used to achieve the sorting and filtering.
    Using the injection system of the present invention, existing atomizing units can be utilized which are supplemented with a sorting and filtering unit.
    This provides a system that is relatively simple and therefore inexpensive to implement.
    Further features and advantages will be apparent from the accompanying description which exemplifies a number of different embodiments of the invention.
    Brief Description of the Drawings Fig. 1 shows a schematic block diagram illustrating the invention.
    Fig. 2 shows a schematic longitudinal section of a sorting and filtering unit according to a first embodiment of the invention.
    Fig. 3 shows a schematic cross-section of the sorting and filtering unit shown in Fig. 2.
    Fig. 4 shows a schematic longitudinal section of a sorting and filtering unit according to a second embodiment of the invention.
    DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION In the accompanying figures, the same or similar parts are shown with the same reference numerals.
    Referring first to Figure 1, there is shown a block diagram illustrating the invention.
    The invention thus relates to an injection system 2 for an internal combustion engine, for example for a vehicle, where the system is adapted to inject a reducing agent 4, for example urea, into an exhaust gas from the internal combustion engine. The vehicle is, for example, a truck, a bus, or a car. However, the injection system may just as well be used in connection with the use of an internal combustion engine in other contexts, for example a ship or for internal combustion engines used in industry.
    The injection system 2 comprises a container 6 intended to contain the reducing agent 4, a pump 8 intended to pump the reducing agent 4 via a supply tube 10 to an atomizing unit 12, which is adapted to generate a solution 14 containing droplets of the reducing agent 4 and deliver air to the outlet via an outlet 15.
    The atomizing unit 12 may, for example, comprise a small opening in a nozzle through which the reducing agent passes and thereby the air flow is achieved with the droplets.
    The air flow with the reducing agent must have a pressure of approx. 10 bar when it is injected into the exhaust flow. The atomization unit 12 can operate according to different techniques, e.g. as a spray or as a nebulizer, which can for instance be realized as a compressed air nebulizer where air is forced through a small hole and entrains the liquid through the hole.
    The system further comprises a sorting and filtering unit 16 adapted to sort the droplets in the air flow received via the discharge tube 15 and filter out droplets having a size exceeding an adjustable, predetermined first droplet size limit. The predetermined first droplet size limit is, for example, in the range 15-25 μm, preferably 20 μm. Of course, this droplet size limit can be set to a much higher value, for example 100 μm or lower, in some operating cases.
    The effluent 18 with the unfiltered droplets is adapted to be supplied to the effluent effluent via an injection tube 20 and the filtered droplets 22 are returned to the container via a recirculation tube 24.
    In the case, the discharge pipe 10, the injection pipe 20 and the return pipe 24 have only been indicated by arrows. The pipes are realized, for example, with fl visible rubber hoses or metal pipes.
    According to one embodiment, the injection system comprises a control unit 26 adapted to generate a size control signal 28 adapted to be applied to the size and filtration unit 16, for setting the predetermined first droplet size limit. In Figure 1, the control unit and the signals generated by it have been dashed to indicate that the control unit is part of an embodiment of the system. It is thus possible to continuously vary the droplet size limit, for example depending on the temperature of the exhaust gases in the exhaust gas flow, which can be advantageous since it is then possible to optimize the effect of the added reducing agent.
    According to another embodiment, the control unit 26 is adapted to generate a pump control signal 30 adapted to be applied to said pump 8 for setting the working level of the pump, for example the pressure of the reducing agent.
    The control unit 26 may also be adapted to generate both a size control signal 28 adapted to be applied to the size and filtration unit 16, for setting the predetermined first droplet size limit and a pump control signal 30 adapted to be applied to said pump 8 for adjusting the working level of the pump.
    The control unit 26 bases its control on information received from other sensors on the vehicle, for example temperature sensors in the exhaust gas, and on information from the vehicle's central control system.
    The injection system comprises a sorting and filtering unit for sorting and filtering the droplets with respect to droplet size. The sorting and filtering can take place in two different steps or substantially simultaneously. To achieve a sizing of droplets of the current size, ie. in the order of less than 100 μm, different techniques can be used.
    For example, one can take advantage of the fact that drops of different sizes have different masses, which means that the so-called inertial impaction can be used. Another sorting method is based on electrically charging the droplets and using the different charge that different large droplets receive. These two methods will now be briefly described with reference to Figures 2-4. There are additional sorting methods, for example so-called centrifugation methods, which will not be described in more detail here.
    According to a first embodiment, the sorting and filtering unit 16 is designed so that it sorts and filters the droplets using the inertial effect. Figure 2 shows a vertical cross-section of a schematic view of sorting and filtering unit 16 which utilizes the inertia effect.
    Figure 3 shows a horizontal cross section at level A-A (see figure 2) of the unit 16.
    The principle takes advantage of the fact that larger particles (droplets) have greater mass inertia than smaller ones, which means that the larger particles continue to move in a largely rectilinear way even though the air flow and the small particles bend to get around. When the particle collides with a wall, it gets stuck and is thus "filtered" away from the air flow.
    The unit 16 comprises a circular-cylindrical chamber with a vertically placed outer wall, with an inlet through the outer wall where the air flow with the droplets is supplied via the above-mentioned outflow pipe 15, positioned so that the air flow 14t11 is carried in a horizontal direction substantially in the tangent direction of the outer wall. The injection tube 20 is arranged vertically along a center axis of the chamber, with a lower orifice arranged in a lower part of the chamber. The return pipe 24 is arranged in the lower part of the chamber with an orifice in the outer wall or in a lower boundary wall.
    Figure 3 illustrates how droplets with a size exceeding said droplet size limit will, due to the inertia effect and velocity of the air flow, collide with the inside of the outer wall and then run down the inside and collect in the bottom of the chamber and be led away via the return pipe 24. This air de fate has been denoted by 32. Air fl fate 34 with the unfiltered droplets of smaller size will be discharged from the chamber via the injection pipe 20 and on to the exhaust fl fate.
    According to a second embodiment of the injection system, the sorting and filtering unit sorts and filters the droplets using electrostatic sorting and filtering.
    This embodiment is schematically illustrated in Figure 4 which shows a longitudinal section of the unit 16. The air gap 14 containing droplets of different sizes passes past an electrically charged electrode 36 which in the figure has a negative charge. When the droplets 8 pass the negative charge, a negative charge is transferred to the droplets which are larger the larger the droplet.
    The negatively charged droplets then pass past positively charged electrodes 38, which are arranged, for example, on the inside of the tube and have an elongate extent. As the droplets pass the positively charged electrode or electrodes 38, the droplets are more attracted the greater charge they have, i.e. the larger droplets are attracted to a greater degree than the smaller droplets which have a relatively smaller charge. By changing the magnitude of the positive charge that the electrodes have, one can thereby set a magnitude limit value for the droplets that are allowed to pass. The droplets in excess of this size are drawn in towards the electrode and the liquid is collected and led back to the container 6 (see figure 1) via the return pipe 24 (see figure 1).
    According to a further embodiment, the sorting and filtering unit has an adjustable, predetermined second droplet size limit, and that the unit is adapted to filter out droplets below said second droplet size limit and return the filtered droplets to the container via said return pipe. The second droplet size limit is lower than the first droplet size limit and is preferably in the range 1-5 μm. The purpose of recirculating reducing agents having a droplet size smaller than this limit is mainly to reduce the consumption of reducing agents because the smallest droplets have too little mass to be pushed into the exhaust gas without "bouncing" back.
    The invention also comprises an internal combustion engine comprising an exhaust system comprising an injection system according to any of the embodiments described above.
    The present invention is not limited to the preferred embodiments described above.
    Various alternatives, modifications and equivalents can be used. The above embodiments are, therefore, not to be construed as limiting the scope of the invention as defined by the appended claims.
    权利要求:
    Claims (12)
    [1]
    Injection system (2) for an internal combustion engine, wherein the system is adapted to inject a reducing agent (4) into an exhaust gas fl from the internal combustion engine, the system (2) comprises a container (6) intended to contain the reducing agent (4), a pump (8 ) intended to pump the reducing agent (4) to an atomizing unit (12), which is adapted to generate an air gap (14) containing droplets of the reducing agent (4), characterized in that the system further comprises a sorting and filtering unit (16) adapted to sort the droplets in the air fl outflow from the atomizer (12) and filter out droplets having a size exceeding an adjustable, predetermined first droplet size limit, the air fl outflow (18) with the unfiltered droplets being adapted to be supplied to the exhaust fl outflow via an injection pipe (20) and the droplets (20) 22) are adapted to be returned to the container.
    [2]
    The injection system of claim 1, wherein said predetermined first droplet size limit is in the range of 15-25 μm.
    [3]
    The injection system of claim 2, wherein said predetermined first droplet size limit is 20 μm.
    [4]
    An injection system according to any one of claims 1-3, wherein the system comprises a control unit (26) adapted to generate a size control signal (28) adapted to be applied to the size and filtration unit (16), for setting the predetermined first droplet size limit.
    [5]
    Injection system according to any one of claims 1-3, wherein the system comprises a control unit (26) adapted to generate a pump control signal (30) adapted to be applied to said pump (8) for setting the working level of the pump.
    [6]
    An injection system according to any one of claims 1-3, wherein the system comprises a control unit (26) adapted to generate a size control signal (28) adapted to be applied to the size and filtration unit (16), for setting the predetermined first droplet size limit. and that the control unit (26) is also adapted to generate a pump control signal (30) adapted to be applied to said pump (8) for setting the operating level of the pump.
    [7]
    Injection system according to any one of claims 1-6, wherein said sorting and filtering unit sorts and filters the droplets using the inertial effect.
    [8]
    An injection system according to any one of claims 1-6, wherein said sorting and filtering unit sorts and filters the droplets using electrostatic sorting and filtering.
    [9]
    An injection system according to any one of the preceding claims, wherein the reducing agent is urea.
    [10]
    The injection system of claim 1, wherein said sorting and filtering unit has an adjustable, predetermined second droplet size limit lower than said first droplet size limit, and that the unit is adapted to filter out droplets below said second droplet size limit and return the filtered droplets to the container said return pipe.
    [11]
    An injection system according to claim 10, wherein said second droplet size limit is in the range 1-5 μm.
    [12]
    Internal combustion engine comprising an exhaust system comprising an injection system (2) according to any one of claims 1 to 1 1.
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    同族专利:
    公开号 | 公开日
    SE536126C2|2013-05-21|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    FR3097905A1|2019-06-26|2021-01-01|Faurecia Systemes D'echappement|Exhaust gas aftertreatment device|
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    SE1150948A|SE536126C2|2011-10-13|2011-10-13|Injection system for reducing agent to an exhaust gas flow from an internal combustion engine|SE1150948A| SE536126C2|2011-10-13|2011-10-13|Injection system for reducing agent to an exhaust gas flow from an internal combustion engine|
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