Claims:1. A static mixer unit (100) for mixing exhaust gas and Diesel Exhaust Fluid (DEF) in an exhaust system (101) of a vehicle, the static mixer unit (100) comprising:
a housing (102) receivable by an exhaust pipe (103);
a chamber (104) disposed in the housing (102);
a plurality of blades (105) mounted on the chamber (104), wherein the plurality of blades (105) abuts an inner surface (102a) of the housing (102) and are configured to guide a mixture of the exhaust gas and the DEF; and
a hub (106) supported in the chamber (104), wherein at least a portion of the hub (106) protrudes outwardly from an outlet portion (104d) of the chamber (104),
wherein, an annular passage (110) is defined between an inner surface (104a) of the chamber (104) and an outer surface (106b) of the hub (106) to allow at least a portion of the mixture of the exhaust gas and the DEF to flow from an inlet portion (104c) of the chamber (104) to the outlet portion (104d) of the chamber (104).

2. The static mixer unit (100) as claimed in claim 1, wherein the (DEF) is injected upstream of the inlet portion (104c) of the chamber (104) in a direction of a longitudinal axis (A-A) of the hub (106).

3. The static mixer unit (100) as claimed in claim 1, wherein the hub (106) is configured to break, evaporate and decompose the DEF.

4. The static mixer unit (100) as claimed in claim 1, wherein each of the plurality of blades (105) is inclined at an angle ranging from about 55º to about 65º with respect to the longitudinal axis of the hub (106).

5. The static mixer unit (100) as claimed in claim 1, wherein the plurality of blades (105) are configured to impart spiral flow to the mixture of exhaust gas and the DEF.

6. The static mixer unit (100) as claimed in claim 1, wherein the portion of the hub (106) protruding outwardly from the chamber (104) is defined with a tapered profile (106d).

7. The static mixer unit (100) as claimed in claim 6, wherein an angle of tapered profile (106e) ranges from about 15º to about 25º with respect to the longitudinal axis (A-A) of the hub (106).
8. The static mixer unit (100) as claimed in claim 1, wherein a portion of the hub (106) residing in the chamber (104) is defined with a uniform cross-section (106c).

9. The static mixer unit (100) as claimed in claim 1, wherein an end of the hub (106) towards the inlet portion (104c) of the chamber (104) is defined with a fillet (106b).

10. An exhaust system (101) of a vehicle comprising a static mixer unit (100) as claimed in claim 1. , Description:
TECHNICAL FIELD

The present disclosure generally relates to the field of automobiles. Particularly, but not exclusively, the present disclosure relates to an exhaust system of a vehicle. Further embodiments of the present disclosure disclose a static mixer unit for mixing exhaust gas and Diesel Exhaust Fluid (DEF) in the exhaust system of the vehicle.

BACKGROUND

Vehicles are employed with an exhaust system for routing exhaust gases emitted by an Internal Combustion (IC) engine to the atmosphere. Exhaust systems in general may include an exhaust pipe connected to an exhaust outlet of the IC engine, muffler to attenuate combustion noise. The exhaust gas emitted by the IC engines, particularly diesel engine, may contain components which are harmful to living beings and the environment. As a consequence, emission levels of these exhaust gas components are regulated and there arises a need for the exhaust gas to be treated after it leaves the engine. Thus, exhaust system may be provided with various units for catalytic decomposition of harmful exhaust gases. Such units may be collectively referred to as exhaust after treatment unit.

The exhaust after treatment unit may employ one or more sub-units which converts harmful exhaust gases into less harmful gases. Generally, the exhaust after treatment units used for catalytic decomposition to reduce emissions may include three-way catalyst (catalytic converter). The catalytic converter has the ability to convert toxic gases produced such as carbon monoxide (CO), oxides of nitrogen (NOx) and hydrocarbons (HC) produced by the combustion in the engine to less harmful, non-poisonous fluids like carbon dioxide (CO2), water (H2O) and nitrogen (N2). The exhaust after treatment unit may also include particulate filter unit to remove particulate matter and soot from the exhaust emissions before letting the exhaust into atmosphere.

The exhaust after treatment unit may further include a Selective Catalytic Reduction (SCR) system.. The SCR converts NOx emissions of the exhaust stream into N2 and H2O using a catalysts. The SCR system may contain Diesel Exhaust Fluid (DEF) which is typically aqueous solution of urea or ammonia gas and an injector for injecting DEF into the exhaust stream. The DEF may be injected into an exhaust pipe, where it mixes with the exhaust gas and consequently evaporation, decomposition and hydrolysis takes place. After hydrolysis, the DEF changes to ammonia which then reacts with the NOx emission to reduce it to N2 and H2O.
Conventionally it is known to provide a mixer unit upstream of the SCR system for mixing the DEF with the exhaust gas. Such a mixer unit may consist of a vessel, and a number of blades mounted on the vessel. The DEF may be impinged on the vessel to decompose and evaporate the DEF, the DEF may then mix with the exhaust gas and the mixture driven further through the blades.

However, such a conventional mixer unit is known leave depositions of DEF on some portions of the mixer unit, thus leaving a portion of the DEF unutilized in its application. Also, deposition of the DEF may accumulate over time, and may result in obstruction to the flow of exhaust fluid in the exhaust pipe.

The present disclosure is directed to overcome the above stated problems or any other similar problems associated with the conventional arts.

SUMMARY OF THE DISCLOSURE

One or more shortcomings of conventional devices or systems are overcome and additional advantages are provided through the device and the system as claimed in the present disclosure. Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed disclosure.

In one non-limiting embodiment of the disclosure, a static mixer unit for mixing exhaust gas and Diesel Exhaust Fluid (DEF) in an exhaust system of a vehicle is disclosed. The static mixer unit comprises a housing receivable by an exhaust pipe, a chamber disposed in the housing, a plurality of blades mounted on the chamber. The plurality of blades abuts an inner surface of the housing and are configured to guide a mixture of the exhaust gas and the DEF. The static mixer unit further comprises a hub supported in the chamber, at least a portion of the hub protrudes outwardly from an outlet portion of the chamber. An annular passage is defined between an inner surface of the chamber and an outer surface of the hub to allow at least a portion of the mixture of the exhaust gas and the DEF to flow from an inlet portion of the chamber to the outlet portion of the chamber.

In an embodiment of the disclosure, the DEF is injected upstream of the inlet portion of the chamber in a direction of a longitudinal axis (A-A) of the hub. The hub is configured to break, evaporate and decompose the DEF.
In an embodiment of the disclosure, each of the plurality of blades is inclined at angle ranging from about 55º to about 65º with respect to the longitudinal axis of the hub. The plurality of blades are configured to impart spiral flow to the mixture of exhaust gas and the DEF.

In an embodiment of the disclosure, the portion of the hub protruding outwardly from the chamber is defined with a tapered profile. Angle of tapered profile ranges from about 15º to about 25º with respect to the longitudinal axis of the hub.

In an embodiment of the disclosure, a portion of the hub residing in the chamber is defined with a uniform cross-section.

In an embodiment of the disclosure, an end of the hub towards the inlet portion of the chamber is defined with a fillet.

It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the disclosure.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The novel features and characteristic of the disclosure are set forth in the appended claims. The disclosure itself, however, and further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings. One or more embodiments are now described, by way of example only, with reference to the accompanying drawings wherein like reference numerals represent like elements and in which:

FIG.1 is a schematic representation of an exhaust system of a vehicle employed with a static mixer unit, in accordance with an embodiment of the present disclosure.

FIG.2 illustrates perspective view of the static mixer unit, in accordance with an embodiment of the disclosure.
FIG.3 illustrates schematic side view of the static mixer unit of FIG.2.

FIG.4 illustrates side view of a hub of the static mixer unit of FIG.2.

FIG.5 is a schematic representation of the static mixer unit provisioned upstream of a Selective Catalytic Reduction (SCR) unit of the exhaust system, in accordance with an embodiment of the disclosure.

FIG.6 is a schematic representation of CFD results showing state of flow of exhaust gas and the DEF in an exhaust pipe employed with the static mixer unit, in accordance with an embodiment of the disclosure.

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION

While the embodiments in the disclosure are subject to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

It is to be noted that a person skilled in the art would be motivated from the present disclosure and would modify various constructions of static mixer unit, which may vary from one vehicle to other. However, such modifications should be considered to be within the scope of the disclosure. Accordingly, the drawings show only those specific details that are pertinent to understand the embodiments of the present disclosure, so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein. Also, the static mixer unit of the present disclosure may be employed in any kind of vehicle ranging from passenger vehicles to commercial vehicles.

The terms “comprises”, “comprising”, or any other variations thereof used in the disclosure, are intended to cover a non-exclusive inclusion, such that a device, system, assembly that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such system, or assembly, or device. In other words, one or more elements in a system or device proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or device.

Embodiments of the present disclosure disclose a static mixer unit for mixing exhaust gas and Diesel Exhaust Fluid (DEF) in an exhaust system of a vehicle. The static mixer unit of the present disclosure is configured such that it reduces deposition of the DEF on various components of the static mixer unit and in the exhaust pipe. Thus, with the reduction of deposition of DEF, it may be ensured that the DEF is effectively utilized in conversion of NOx emissions of the engine of the vehicle.

The static mixer unit is provisioned upstream of an Selective Catalytic Reduction (SCR) unit of the exhaust system in an exhaust pipe. The static mixer unit may be configured to thoroughly mix the DEF and the exhaust gas emitted by the engine before it is let off into the SCR unit for reduction of NOx emissions.

Accordingly, the static mixer unit of the present disclosure comprises a housing in which all the components of the static mixer unit may be housed. The housing is adapted to be receivable by the exhaust pipe and may be provisioned upstream of the SCR unit. Further, a chamber may be disposed in the housing and a plurality of blades is mounted on an outer surface of the chamber. The blades are configured such that they abut to an inner surface of the chamber. Thus, the blades are configured as static members. In an embodiment, the blades are mounted angularly on the chamber such that they may impart spiral flow to the fluid flowing across the plurality of blades. The spiral flow so imparted to the fluid may enhance the mixing of DEF and the exhaust gas.

The static mixer unit further consists of a hub supported in the chamber. The hub may be a substantially conical shaped member with a portion of the hub protruding outwards from an outlet region of the chamber. The portion that protrudes outwards from the outlet portion of the chamber has a gradually tapering cross-section and hence giving the hub its conical shape. The profile of the hub in the chamber may be configured such that an annular passage may be defined between an outer surface of the hub and an inner surface of the chamber. The annular passage acts as a fluid passage as well. Thus, when the DEF is injected through an injector into exhaust stream, it may impinge on the hub to cause the DEF to break, decompose and evaporate and eventually form Ammonia. In an embodiment, since the hub is a solid member, a portion of the DEF may enter the chamber and impinge on the outer surface of the hub, during which the annular passage may act as an exit for the mixture of DEF and exhaust gas. A remaining portion of the mixture of exhaust gas and the DEF may pass through the plurality of blades imparting swirling motion to the fluid. The hub in the present disclosure ensures that a substantial amount of DEF injected into the exhaust stream break down and decompose to form Ammonia which may further react with the exhaust gas in the SCR unit to reduce NOx emissions. Therefore, deposition of DEF on the components of the static mixer unit may be substantially reduced.

The following paragraphs describe the present disclosure with reference to FIGS. 1 to 6. In the figures, the same element or elements which have similar functions are indicated by the same reference signs. In the figures, the door and the vehicles are not illustrated for the purpose of simplicity.

FIG.1 is an exemplary embodiment of the present disclosure, which is a schematic representation of an exhaust system (101) provisioned with a static mixer unit (100) of the present disclosure. The exhaust system (101) as shown in FIG.1, may consist of an exhaust pipe (103) for the flow of exhaust gas after emission from an engine of a vehicle. The exhaust system (101) generally includes an exhaust after treatment unit to treat the exhaust gas to convert harmful emissions of the engine to less harmful gases before letting the exhaust mass into the atmosphere. In an embodiment, the exhaust after treatment unit may include a Selective Catalytic Reduction (SCR) Unit (108) to reduce NOx emissions of the engine. The SCR unit (108) may convert the NOx emissions into less harmful Nitrogen (N2) gas and water vapour (H2O) before letting into the atmosphere. The SCR unit (108) does so with the aid of a Diesel Exhaust Fluid (DEF) injected into the stream of exhaust gas in the exhaust pipe (103). In an embodiment, DEF may be an ad-blue solution which may be typically a solution of Urea wherein Urea may be about 67.5% and water may be about 32.5%. The DEF may be injected through an injector (109) at a pre-defined rate and a pre-defined angle as per the operating conditions of the engine. The DEF injector (109) may be provisioned upstream of the static mixer unit (100) and the DEF is injected into the exhaust pipe (103) to interact with the exhaust gas and may be converted to Ammonia vapour, which then reduces the NOx emissions in the SCR unit (108).

Therefore, mixing of the DEF with the exhaust gas may be necessary for efficient conversion of DEF into Ammonia vapour. As shown in FIG.1, the present disclosure includes a static mixer unit (100) provisioned in the exhaust pipe (103) of the exhaust system (101) for mixing the DEF with the exhaust gas. The static mixer unit (100) is provisioned in the upstream of the SCR unit (108) so as to supply a homogenous mixture of exhaust gas and the DEF to the SCR unit (108), where NOx emissions are reduced. The components of the static mixer unit (100) which aids in thorough mixing and breakdown of DEF into Ammonia vapour is explained is subsequent paragraphs of the disclosure. In an embodiment, the exhaust system (101) further includes a mixing chamber (107). As the mixture of Ammonia vapour - obtained from the DEF; and the exhaust gas exits the static mixer unit (100), they may be imparted with a circulating or a swirling motion due to the configuration of a plurality of blades (105). This mixture enters the mixing chamber (107), wherein the Ammonia vapour and the exhaust gas are thoroughly mixed before entering the SCR unit (108). Thus, the SCR unit (108) receives a uniform or a homogenous mixture of Ammonia and the exhaust gas.

Referring now to FIG.2 and FIG.3, they illustrate perspective view and a schematic side of view of the static mixer unit (100) respectively. As described previously, the static mixer unit (100) of the present disclosure is adapted to mix the DEF and the exhaust gas and consequently allow breakdown, evaporation and decomposition of the DEF. An efficient decomposition of the DEF or the urea solution facilitates hydrolysis and thus formation of Ammonia vapour.

The static mixer unit (100) comprises a housing (102) in which all the components of the static mixer unit (100) may be housed and supported. There may be a chamber (104) disposed in the housing (102). In an embodiment the chamber (104) may be a hollow cylinder with an inlet portion (104c) and an outlet portion (104d) as shown in FIG.3. The exhaust gas or a mixture of the exhaust gas and the DEF may enter and exit through the said inlet portion (104c) and the outlet portion (104d) of the chamber (104). Further, the static mixer unit (100) includes a hub (106) supported in the chamber (104). The hub (106) may be configured such that a portion of the hub (106) extends outwards from the chamber (104). The hub (106) may be in form of a cone shape as shown in the FIGS.2 and 3. The hub (106) is the component which facilitates breakdown, evaporation and decomposition of the DEF to convert it into Ammonia vapour. In an embodiment, the hub (106) may be supported in the chamber (104) such that there may be formation of an annular passage (110) between an outer surface (106a) of the hub (106) and an inner surface (104a) of the chamber (104). The annular passage (110) so defined may allow flow of fluid along this passage. In an embodiment, when the DEF is injected into the exhaust stream, a portion of the DEF along with the exhaust gas may pass through the annular passage (110). As the DEF passes through the annular passage (110), it may impinge on the walls of the hub (106) and the chamber (104) resulting in decomposition of the DEF or the urea solution. As shown in FIG.2, the DEF may be injected in a substantially central direction of the static mixer unit (100) along longitudinal axis of the hub (106). The DEF may decompose when it is impinged on the hub (106).

In an embodiment of the disclosure, the hub (106) may be thermally joined to the chamber (104) using suitable lugs. As an example, thermal joining such as welding may be performed at two or more locations between the outer surface (106a) of the hub (106) and the inner surface (104a) of the chamber (104) to define the annular passage (110).

The static mixer unit (100) further consists of a plurality of blades (105) mounted on the chamber (104). In an embodiment, the plurality of blades (105) may be spaced apart equidistantly, wherein each of the plurality of blades (105) may be of a pre-defined shape. In an embodiment, each of the plurality of blades (105) may be angularly twisted in a spiral shape. As an example, there may be eight blades (105) mounted on an outer surface (104b) of the chamber (104) and may abut an inner surface (102a) of the housing (102). In an embodiment, the blades (105) may be either integrally formed on the chamber (104) or may be thermally joined to the chamber (104) and the inner surface (102a) of the housing (102). The blades (105) may be configured to impart a spiral or a circulating motion to the fluid that passes through it. In an embodiment, a portion of the DEF injected into the exhaust stream may mix with the exhaust gas and may pass through the plurality of blades (105) and then exit the outlet portion (104d) of the chamber (104). Thus, as this mixture of DEF and exhaust gas pass through the plurality of blades (105), they exit with a spiral or a circulating motion.

The spiral motion or the circulating motion of the mixture of exhaust gas may be seen in FIG.6, wherein the initial path of the exhaust gas and the DEF in the exhaust pipe (103) is linear, and subsequently, once the mixture exits the static mixer unit (100), they are imparted with a spiral or a circular motion. Such a motion allows better mixing of the DEF or Ammonia vapour with the exhaust gas and therefore a uniform, homogeneous mixture may enter the SCR unit (108) to ensure better reduction of the NOx emissions.

Referring to FIG.3 again, each of the plurality of blades (105) may be defined with a specific angle with respect to the longitudinal axis (A-A) of the hub (106). The blade angle of each of the plurality of blades (105) is shown as A. In an embodiment, the blade angle A may be optimized to obtain required result and may be in the range of about 55° to 65°. As an example, the blade angle may be 60°.

Moving on to FIG.4, it illustrates side view of the hub (106) of the static mixer unit (100). The hub (106) may be configured to decompose and cause evaporation of the DEF or the Urea solution to facilitate its hydrolysis and thus formation of Ammonia vapour. The hub (106) may be of a conical shape, with a portion of the hub (106) defined with a tapered profile (106d). In an embodiment, the portion of the hub (106) which protrudes out of the chamber (104) may be tapered. The taper angle is shown in the FIG.4 as B. The taper angle (B) of the hub (106) may be in the range of about 15° to about 25°. As an example, the taper angle may be 20° with respect to longitudinal axis (A-A) of the hub (106). Further, as shown in FIG.4, a portion of the hub (106) is of uniform cross-section (106c). The uniform cross-section (106c) portion of the hub (106) resides with in the chamber (104) and this uniform cross-section (106c) of the hub (106) may be circular in cross-section, and as an example diameter of the circular cross-section may be 50 millimetres (mm). In an embodiment, one end of the hub (106) that is towards the inlet portion (104c) of the chamber (104) may be defined with a fillet (106b). Such a configuration of the hub (106) facilitates better decomposition of the DEF, and thus reduces deposition of the DEF or Urea.

FIG.5 is an exemplary embodiment of the present disclosure, which is a schematic representation of the exhaust system (101). As shown FIG.5, the static mixer unit (100) may be provisioned in the exhaust pipe (103) upstream of the SCR unit (108). As described previously, the static mixer unit (100) may be provided upstream of the SCR unit (108) to ensure that a uniform and homogeneous mixture of the DEF or Ammonia vapour and the exhaust gas enters the SCR unit (108) for reduction of NOx emissions.

In an embodiment, the static mixture unit (108) is simple in construction and retrofittable.

In an embodiment, the static mixture unit (108) includes a hub (106) which reduces deposition of DEF in the exhaust pipe (103), and thereby improves the performance of the exhaust after treatment unit.

It is to be understood that a person of ordinary skill in the art may develop a mixer unit of similar configuration without deviating from the scope of the present disclosure. Such modifications and variations may be made without departing from the scope of the present invention. Therefore, it is intended that the present disclosure covers such modifications and variations provided they come within the ambit of the appended claims and their equivalents.

Equivalents:

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances, where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.” While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Referral Numerals:

100 Static Mixer Unit
101 Exhaust system of a vehicle
102 Housing
102a Inner surface of the housing
103 Exhaust pipe
104 Chamber
104a Inner surface of the chamber
104b Outer surface of the chamber
104c Inlet portion of the chamber
104d Outlet portion of the chamber
105 Blades
A Blade angle
106 Hub
106a Outer surface of the hub
A-A Longitudinal axis of the hub
B Internal angle of the hub
106b Fillet on the hub
106c Uniform cross-section of the hub
106d Tapered portion of hub
107 Mixing chamber
108 Selective Catalytic Reduction (SCR) unit
109 Injector
110 Annular passage