Patent Publication Number: US-2023132502-A1

Title: Atomizer with multiple pressure swirl nozzles

Description:
TECHNICAL FIELD 
     This disclosure relates generally to an atomizer with multiple swirl nozzles for a vehicle exhaust system. 
     BACKGROUND 
     An exhaust system includes catalyst components to reduce emissions. The exhaust system includes an injection system that injects a diesel exhaust fluid (DEF), or a reducing agent such as a solution of urea and water for example, upstream of an exhaust gas aftertreatment component, such as, for example, a selective catalytic reduction (SCR) catalyst which is used to reduce NOx emissions. The injection system includes an atomizer or a doser that sprays the fluid into the exhaust stream via an injector or doser. Low temperature and low load conditions make it difficult to achieve optimum spray characteristics. 
     SUMMARY 
     An aftertreatment atomizer, according to an exemplary aspect of the present disclosure includes, among other things, a valve body providing a valve seat and including a plurality of feeding channels, a pintle configured to move between open and closed positions relative to the valve seat, and a nozzle plate including a plurality of swirling grooves Each swirling groove has a pressure swirl nozzle opening configured to eject fluid exiting a respective feeding channel into an exhaust pipe. 
     In a further non-limiting embodiment of the foregoing atomizer, the pintle defines a center axis, and wherein the valve body includes a main feeding hole that is concentric with the center axis. 
     In a further non-limiting embodiment of any of the foregoing atomizers, the main feeding hole is separate from the plurality of feeding channels. 
     In a further non-limiting embodiment of any of the foregoing atomizers, the valve seat has a tapered surface that tapers radially inwardly in a direction toward the main feeding hole, and wherein each feeding channel has an inlet at the tapered surface and an outlet to one swirling groove of the plurality of swirling grooves. 
     In a further non-limiting embodiment of any of the foregoing atomizers, each swirling groove has a first inlet port that receives fluid from the outlet of a respective feeding channel and a second inlet port that receives fluid from the main feeding hole, and wherein fluid from the first and second inlet ports is ejected into the exhaust pipe via a respective pressure swirl nozzle opening. 
     In a further non-limiting embodiment of any of the foregoing atomizers, the nozzle plate includes a recessed area that receives fluid from the main feeding hole and simultaneously directs fluid into each second inlet port of the plurality of swirling grooves. 
     In a further non-limiting embodiment of any of the foregoing atomizers, each swirling groove includes an enlarged recess forming a swirl chamber that is at least partially defined by curved wall portions, each enlarged recess being located radially inward of a respective first inlet port and radially outward of a respective second inlet port. 
     In a further non-limiting embodiment of any of the foregoing atomizers, the first inlet port feeds into a first linear passage portion that is tangential to one curved wall portion, and wherein the second inlet port feeds into a second linear passage portion that is tangential to another curved wall portion opposite the one curved wall portion. 
     In a further non-limiting embodiment of any of the foregoing atomizers, the plurality of feeding channels comprise four feeding channels, and wherein the plurality of swirling grooves comprises four swirling grooves. 
     In a further non-limiting embodiment of any of the foregoing atomizers, when in the closed position, the pintle engages the valve seat to block the inlets to the plurality of feeding channels while also blocking the main feeding hole, and when in the open position, the pintle moves out of engagement with the valve seat to open the inlets to the plurality of feeding channels while also opening the main feeding hole. 
     In a further non-limiting embodiment of any of the foregoing atomizers, a heating element heats the fluid before entering the plurality of feeding channels, and including a controller to control the heating element and movement of the pintle. 
     An aftertreatment atomizer, according to yet another exemplary aspect of the present disclosure includes, among other things, a valve body providing a valve seat and including a plurality of feeding channels, wherein each feeding channel extends from an inlet at the valve seat to an outlet, a main feeding hole formed in the valve body downstream of the valve seat, and a pintle defining a center axis and configured to move between open and closed positions relative to the valve seat. A nozzle plate includes a plurality of swirling grooves, wherein each swirling groove has a pressure swirl nozzle opening for feeding fluid to an exhaust pipe. When the pintle is in the open position, fluid flows into the plurality of feeding channels and the main feeding hole, exits into plurality of swirling grooves, and is then ejected from each pressure swirl nozzle opening into the exhaust pipe. 
     In a further non-limiting embodiment of any of the foregoing atomizers, the main feeding hole is separate from the plurality of feeding channels which are circumferentially spaced apart from each other about the center axis, and wherein each feeding channel extends from a respective inlet in a radially outward direction to a respective outlet. 
     In a further non-limiting embodiment of any of the foregoing atomizers, the valve seat has a tapered surface that tapers radially inwardly in a direction toward the main feeding hole, and wherein the inlet of each feeding channel is at the tapered surface and the outlet of each feeding channel is open to one swirling groove of the plurality of swirling grooves. 
     In a further non-limiting embodiment of any of the foregoing atomizers, each swirling groove has a first inlet port that receives fluid from the outlet of a respective feeding channel and a second inlet port that receives fluid from the main feeding hole, and wherein fluid from the first and second inlet ports is ejected into the exhaust pipe via a respective pressure swirl nozzle opening. 
     In a further non-limiting embodiment of any of the foregoing atomizers, the nozzle plate includes a recessed area that receives fluid from the main feeding hole and simultaneously directs fluid into each second inlet port of the plurality of swirling grooves, and wherein each swirling groove includes an enlarged recess forming a swirl chamber that is at least partially defined by curved wall portions, each enlarged recess being located radially inward of a respective first inlet port and radially outward of a respective second inlet port. 
     In a further non-limiting embodiment of any of the foregoing atomizers, the first inlet port feeds into a first linear passage portion that is tangential to one curved wall portion, and wherein the second inlet port feeds into a second linear passage portion that is tangential to another curved wall portion opposite the one curved wall portion. 
     A method according to still another exemplary aspect of the present disclosure includes, among other things: providing a valve body with a valve seat and a plurality of feeding channels; configuring a pintle to move between open and closed positions relative to the valve seat; positioning a nozzle plate with a plurality of swirling grooves downstream of the pintle; feeding fluid from the plurality of feeding channels into the plurality of swirling grooves when the pintle is in the open position; and ejecting fluid into an exhaust pipe from a pressure swirl nozzle opening associated with each swirling groove. 
     In a further non-limiting embodiment of the foregoing method, the method further includes: providing a main feeding hole that is downstream of the valve seat and concentric with a center axis defined by the pintle, wherein the main feeding hole is separate from the plurality of feeding channels; tapering the valve seat radially inwardly in a direction toward an upstream end of the main feeding hole; and extending each feeding channel from an inlet at a tapered surface of the valve seat to an outlet to one swirling groove of the plurality of swirling grooves. 
     In a further non-limiting embodiment of any of the foregoing methods, the method further includes: forming a first inlet port for each swirl chamber of each swirling groove that receives fluid from the outlet of a respective feeding channel; forming a second inlet port for each swirl chamber of each swirling groove that receives fluid from the main feeding hole; forming a recessed area in the nozzle plate that receives fluid from the main feeding hole and simultaneously directs fluid into each second inlet port of the plurality of swirling grooves; and ejecting the fluid received from the first and second inlet ports into the exhaust pipe via the pressure swirl nozzle openings. 
     The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the detailed description. The figures that accompany the detailed description can be briefly described as follows: 
         FIG.  1    schematically illustrates one example of an exhaust system with an injection system according to the subject disclosure. 
         FIG.  2    is a section view of one example of an atomizer as used in the injection system of  FIG.  1   . 
         FIG.  3    is a perspective view of an upstream side of a nozzle plate from the atomizer of  FIG.  2   . 
         FIG.  4    is a view similar to  FIG.  3    but showing spray patterns for the nozzle plate. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure relates generally to fluid atomizers, and more specifically to a dosing module that sprays reductant into an exhaust gas flow path of a vehicle exhaust gas aftertreatment system upstream of an aftertreatment catalyst component. This disclosure details an exemplary atomizer with multiple pressure swirl nozzles that achieve a very small spray droplet size while also increasing the total mass flow rate for injection purposes. 
       FIG.  1    shows a vehicle exhaust system  10  that conducts hot exhaust gases generated by an engine  12  through various upstream exhaust components  14  to reduce emission and control noise as known. In one example configuration, the upstream exhaust component  14  comprises at least one pipe that directs engine exhaust gases into one or more exhaust gas aftertreatment components. In one example, the exhaust gas aftertreatment components include a diesel oxidation catalyst (DOC)  16  having an inlet  18  and an outlet  20 , and an optional diesel particulate filter (DPF) that is used to remove contaminants from the exhaust gas as known. Downstream of the DOC  16  and optional DPF is a selective catalytic reduction (SCR) catalyst  22  having an inlet  24  and an outlet  26 . The outlet  26  communicates exhaust gases to downstream exhaust components  28  and then to an external environment. Optionally, component  22  can comprise a catalyst that is configured to perform a selective catalytic reduction function and a particulate filter function. The various downstream exhaust components  28  can include one or more of the following: pipes, filters, valves, catalysts, mufflers etc. These upstream  14  and downstream  28  components can be mounted in various different configurations and combinations dependent upon vehicle application and available packaging space. It should be understood that  FIG.  1    is merely one example configuration and that other system architectures and other combinations of exhaust system components could be utilized. 
     In one example, a mixer  30  is positioned downstream from the outlet  20  of the DOC  16  or DPF and upstream of the inlet  24  of the SCR catalyst  22 . The upstream catalyst and downstream catalyst can be in-line or in parallel, for example. The mixer  30  is used to facilitate mixing of the exhaust gas; however, in some configurations a mixer is not utilized. 
     An injection system  32  is used to inject a reducing agent, such as diesel exhaust fluid (DEF), for example, into the exhaust gas stream upstream from the SCR catalyst  22  such that the mixer  30  can mix the DEF and exhaust gas thoroughly together. Optionally, the injection system  32  can inject the DEF into the exhaust gas stream directly upstream of an exhaust gas after-treatment component, such as the SCR catalyst  22 , for example. The injection system  32  includes a fluid supply tank  34 , an injector/doser  36 , and a controller  38  that controls injection of the fluid as known. In one example, the doser  36  injects the DEF into the mixer  30  as shown in  FIG.  1   . In other examples, the doser  36  can inject the DEF into the exhaust system at other locations such as upstream or downstream of the mixer  30  as schematically indicated at  36 ′. 
     Providing ultra-low NOx emissions requires dosing at low temperatures to address de-nox at cold start and low load cycles. Dosing DEF at low temperatures raises thermolysis and deposit issues as there is usually insufficient heat from the exhaust gas to manage deposits. To address these issues, under certain operating conditions, the injection system  32  heats the DEF prior to entering the exhaust gas stream, which provides for faster atomization and better mixing. 
     A heating source  40  is associated with the injection system  32  and is used to selectively pre-heat the DEF prior to mixing with exhaust gas. Any type of heating element suitable for heating DEF can be used to provide the heating source  40 . For example, the heat source  40  can comprise a heat exchanger assembly with a helical sleeve carrying the DEF, surrounded by heated element on the outside, or electrodes, or other type of heating elements could also be used. Preheating of the DEF occurs in the doser  36  before the DEF is introduced into the exhaust gas stream and the heated DEF can be in the form of a liquid, gas, or a mixture of both. Under certain operating conditions, non-heated DEF is also injected into the exhaust gas stream. The controller  38  is used to control operation of the heating element. 
     A control system includes the controller  38  that controls heating of the DEF and/or injection of the DEF based on one or more of exhaust gas temperature, exhaust gas flow rate, backpressure, time, wear, etc. Additionally, there are a plurality of sensors  42  that can be used to determine temperatures through the system, flow rates, rate of deposit formation, and wear, for example. The sensors  42  communicate data to the controller  38  such that the controller  38  can determine when to generate a control signal that is communicated to the injection system  32  to control when DEF is to be injected in a heated or non-heated applications. 
     The controller  38  can be a dedicated electronic control unit or can be an electronic control unit associated with a vehicle system control unit or sub-system control unit. The controller  38  can include a processor, memory, and one or more input and/or output (I/O) device interface(s) that are communicatively coupled via a local interface. The controller  38  may be a hardware device for executing algorithms in software, particularly software stored in memory. The controller  38  can be a custom made or commercially available processor, or generally any device for executing software instructions. 
       FIG.  2    schematically shows one example of an atomizer  50  for the injector/doser  36  of the injection system  32 . In one example, the atomizer  50  includes a pintle seat/valve body  52  having a valve seat  54  and including a plurality of feeding channels  56 . A pintle  58  is configured to move within a fluid chamber  48  formed within the valve body  52  between open and closed positions relative to the valve seat  54 . Any type of actuator for a dosing system can be used to control movement of the pintle  58 . For example, electric actuators or electromagnetic actuators in combination with compression springs could be used to control movement of the pintle. Additionally, the controller  38 , for example, can also be used in conjunction with the actuator to control pintle movement. 
     A nozzle plate  60  is directly fixed to the valve body  52  and is positioned downstream of the pintle  58 . The nozzle plate  60  includes a plurality of swirling grooves  62 . Each swirling groove  62  comprises a swirl chamber  64  and has a pressure swirl nozzle opening  66  ( FIG.  3   ) for feeding fluid to an exhaust pipe  68 . Optionally, the fluid can be fed into the mixer  30 . The fluid chamber  48  that receives the pintle  58  and the nozzle plate  60  are in fluid communication with each other via the plurality of feeding channels  56  such that the plurality of feeding channels  56  direct the fluid into the plurality of swirling grooves  62  where the fluid is then ejected from the pressure swirl nozzle openings  66  into the exhaust pipe  68 . 
     The pintle  58  defines a center axis A. In one example, the valve body  52  includes a main feeding channel or hole  70  that is concentric with the center axis A. The main feeding hole  70  is separate from the plurality of feeding channels  56  and is downstream of the pintle  58  and the valve seat  54 . The main feeding hole  70  receives fluid from the fluid chamber  48  when the pintle  58  is in the open position. The plurality of feeding channels  56  are circumferentially spaced apart from each other about the center axis A, and each feeding channel  56  extends from a respective inlet  72  in a radially outward direction to a respective outlet  74 . In one example, the channels  56  extend at an obtuse angle relative to the center axis A. 
     In one example, the valve seat  54  has a tapered surface that tapers radially inwardly in a direction toward the main feeding hole  70 . In one example, the main feeding hole  70  comprises a bore that transitions from a downstream end of the tapered surface of the valve seat  54  and terminates at distal end that is open to the nozzle plate  60 . In one example, the bore has a constant diameter. Each feeding channel  56  has an inlet  72  at the tapered surface of the valve seat  54  and an outlet  74  to one swirling groove  62 . In one example, each swirling groove  62  has a first inlet port  76  that receives fluid from the outlet  74  of a respective feeding channel  56  and a second inlet port  78  that receives fluid from the main feeding hole  70 . Fluid from the first  76  and second  78  inlet ports is ejected as spray into the exhaust pipe  68  via the pressure swirl nozzle openings  66  as shown in  FIG.  4   . 
     In one example, the nozzle plate  60  includes an upstream surface  80  facing the pintle  58  and a downstream surface  82  facing opposite the upstream surface  80 . A thickness of the plate  60  is defined as the distance between the upstream surface  80  and the downstream surface  82 . In one example, the swirling grooves  62  are formed within the upstream surface  80  of the nozzle plate  60 . The grooves  62  form discrete recessed swirl areas that do not extend through the entirety of the thickness of the plate  60 . Each discrete recessed swirl area includes one pressure swirl nozzle opening  66  that does extend through the entirety of the thickness of the plate  60 . 
     In one example, the nozzle plate  60  includes a recessed area  84  that receives fluid from the main feeding hole  70  and simultaneously directs fluid into each second inlet port  78  of the swirling grooves  62 . In one example, the recessed area  84  is formed in the upstream surface  80  of the plate  60  and does not extend through the entire thickness of the plate  60 . In one example, the recessed area  84  is centrally located on the nozzle plate  60  and is directly aligned with the main feeding hole  70  along the center axis A. 
     In one example, each swirling groove  62  includes a discrete enlarged recess  86  that forms the swirl chamber  64  and is at least partially defined by curved wall portions  88 . Each enlarged recess  86  is formed in the upstream surface  80  of the nozzle plate  60  and is located radially inward of a respective first inlet port  76  and radially outward of a respective second inlet port  78 . The enlarged recesses  86  do not extend through an entirety of the thickness of the plate  60 . Additionally, these enlarged recesses  86  are separate from each other and are circumferentially spaced apart from each other about the axis A. 
     In one example shown best in  FIG.  4   , the first inlet port  76  feeds into a first linear passage portion  90  that is tangential to one curved wall portion  88 , and wherein the second inlet port  78  feeds into a second linear passage portion  92  that is tangential to another curved wall portion  88  opposite the one curved wall portion  88 . This is best shown in  FIGS.  3 - 4   . 
     As discussed above, the system includes a heating element from a heat source  40 . The heating element is configured to heat the fluid before entering the plurality of feeding channels  56 . The controller  38  controls the heating element and movement of the pintle  58 . 
     In one example, when moved into the closed position, the pintle  58  engages the valve seat  54  to block the inlets  72  to the plurality of feeding channels  56  while also blocking the main feeding hole  70 . When the pintle  58  is moved into the open position ( FIG.  2   ), the pintle  58  moves out of engagement with the valve seat  54  to open the inlets  72  to the feeding channels  56  while also opening the main feeding hole  70 . 
     In one example, the plurality of feeding channels  56  comprise four feeding channels  56  that feed respectively into four swirling grooves  62   a ,  62   b ,  62   c ,  62   d . This is best shown in  FIG.  4   . Each swirling groove  62   a ,  62   b ,  62   c ,  62   d  has a respective pressure swirl nozzle opening  66   a ,  66   b ,  66   c ,  66   d  at a different location on the nozzle plate  60 . This generates four smaller spray cones  96   a ,  96   b ,  96   c ,  96   d , each being associated with one pressure swirl nozzle opening  66   a ,  66   b ,  66   c ,  66   d . The four smaller cones have sprays with smaller droplet size and a reduced mass flow rate compared to the use of one spray cone from a single larger nozzle opening. As shown in  FIG.  4   , the four spray cones  96   a ,  96   b ,  96   c ,  96   d  are very close to each other and overlap with each other to form a single combined cone  98  with small droplet size but high mass flow rate. Thus, the subject disclosure provides an atomizer that can achieve a very small spray droplet size while also providing for an increase in the total mass flow rate for fluid injection in a heated doser. 
     This result is achieved due to the use of four separate pressure swirl nozzles that are all connected to, and controlled by, a single pintle. The droplet size and the mass flow rate of the pressure swirl atomizer decreases with the reduction in its nozzle diameter. Thus, having four pressure swirl atomizers instead of one allows the nozzle diameter to be reduced, thereby reducing the Sauter Mean Diameter (SMD); however, the mass flow rate is not decreased. 
     For a pressure swirl atomizer (PSA), the SMD of the spray droplets is dependent on the film thickness inside nozzle throat as per the following empirical relationship (Wang and Lefebvre): 
     
       
         
           
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     The film thickness is dependent on the nozzle diameter as per following empirical relation: 
     
       
         
           
             
               
                 
                   
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     The mass flow rate is proportional to the flow number, which is dependent on the nozzle diameter: 
         {dot over (m)} =FN*√{square root over ((Δ P ρ))},FN∝ d   o   2  
 
     Thus, there are two relations for nozzle diameter: 
       SMD∝( d   o ) n  and  {dot over (m)}∝d   o   2  
 
     By having four smaller PSA, for example, each PSA sprays with smaller droplet size and reduced mass flow rate. This generates four spray cones ( FIG.  4   ) which are very close to each other and overlap to form a single cone with small droplet size but high mass flow rate. 
     Because the four holes are at different orientations, the axisymmetric uniformity of the cumulative spray can also be expected to be better than a single spray with two inlet ports, for example. Although four holes are shown as an example, fewer holes or additional holes could also be utilized. For example, three and five hole configurations could also be used. 
     Although a specific component relationship is illustrated in the figures of this disclosure, the illustrations are not intended to limit this disclosure. In other words, the placement and orientation of the various components shown could vary within the scope of this disclosure. In addition, the various figures accompanying this disclosure are not necessarily to scale, and some features may be exaggerated or minimized to show certain details of a particular component. 
     The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. Thus, the scope of legal protection given to this disclosure can only be determined by studying the following claims.