Description:Complete Specification:
The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed
Field of the invention
[0001] The present disclosure relates to the field of exhaust gas treatment, and more particularly a diesel particulate filter incorporating a metal sintered shape memory alloy for efficient filtration of particulate matter from exhaust gas flowing through the diesel particulate filter.

Background of the invention
[0002] The exhaust aftertreatment systems for internal combustion engines employ oxidation catalysts (OC), selective catalytic reduction (SCR) catalysts, particulate filters (PF) and other exhaust aftertreatment devices. Diesel engines produce particulate particles during combustion of the fuel/air mixture due to incomplete combustion of fuel. This is known as particulate matter. Particulate matter results from the incomplete combustion of diesel fuel that produces soot particles. Soot particles from the diesel engines worsen the particulate matter pollution in the air and are harmful for health. Diesel particulate filters are exhaust gas treatment devices designed to trap this soot and prevent its release into the environment.

[0003] With the implementation of BS-VI norms from April 1st 2020, all on-road vehicles must comply with particulate matter emission targets of less than 4.5 mg/km. Hence new legislation norms such as the Bharat Stage VI have made mandatory Diesel Particulate Filter (DPF) to meet the particulate matter emission targets. Particulate Number refers to
soot particles in exhaust gas whose diameter is of the range 20 nm – 2.5 micrometer. These particles are mainly emitted during the cold phase of the engine (cold-start), and are very hazardous as it can cause lung infections when inhaled. Since the diameter of the soot particles are very small, they cannot be efficiently filtered by the conventional ceramic based DPF. This is because the pore diameter in the porous media of the diesel particulate filter is of the order of microns, but the diameter of the Particulate Number emission particles are much lower than the diameter of the porous media, thereby making it difficult to entrap.

[0004] Patent Application US2011258983AA titled “Reconfigurable mixer for an exhaust aftertreatment system and method of using the same” discloses reconfigurable mixers for exhaust aftertreatment systems. The mixer includes a body portion that is configured to be disposed in an exhaust conduit upstream of an exhaust aftertreatment device and an airfoil portion that is disposed on the body portion and reversibly movable between a deployed position and a retracted position, wherein in the deployed position the airfoil portion provides a deployed resistance to an exhaust gas flow and in the retracted position provides a retracted resistance, and the deployed resistance is greater than the retracted resistance. The mixer preferably comprises a two-way shape memory alloy, particularly a high temperature oxidation resistant shape memory alloy. An exhaust aftertreatment system employing the mixer is also disclosed, as well as a method of using the same.

Brief description of the accompanying drawings
[0005] An embodiment of the invention is described with reference to the following accompanying drawings:
[0006] Figure 1 depicts a section of the exhaust gas treatment system (100);
[0007] Figure 2 depicts a horizontal cut-section view of a diesel particulate filter (106).

Detailed description of the drawings
[0008] Figure 1 depicts a section of an exhaust gas treatment system 100 for the internal combustion engine. The exhaust gas after-treatment system 100 comprises a diesel oxidation catalyst 104, a diesel particulate filter 106, an inlet temperature sensor 102, and at least a diesel particulate filter 106 inlet temperature sensor 105 among other components such as a delta pressure sensor 107 connected across the diesel particulate filter 106 of the exhaust gas system known to a person skilled in the art. The components are mounted inside the exhaust gas pipe (101) downstream of an exhaust manifold of the internal combustion engine. The sensors are in communication with an engine control unit (103).

[0009] In different embodiments of the exhaust gas treatment system (100), the type of catalyst may vary according to the requirement of the system. The catalyst is either one of a diesel oxidation catalyst or a NOx storage catalyst (depending upon the type of exhaust gas system used in the vehicle). The oxidation catalyst or diesel oxidation catalyst 104 are catalytic converters that consist of a monolith honeycomb substrate coated with platinum group metal catalyst. The honeycomb structure comprises small parallel channels that provide a high catalytic contact area to exhaust gases. The oxidation catalyst is designed to oxidize the hydrocarbons in this case the fuel through the exothermic reactions. The oxidation reactions occur only when the temperature inside the diesel oxidation catalyst reaches a pre-defined threshold (the light-off temperature of 300 degrees centigrade in some cases). The diesel oxidation catalyst 104 inlet temperature sensor helps measure this temperature and transmits a signal corresponding to this temperature to the engine control unit 103.

[0010] The diesel particulate filter 106 is positioned downstream from the diesel oxidation catalyst 104 in the exhaust gas system. The diesel particulate filter 106 is a device that physically captures diesel particulates to prevent their release to the atmosphere. Due to the soot particulate matter deposition, diesel particulate filters 106 are most effective in controlling the solid fraction of diesel particulates which are an outcome of incomplete combustion in the combustion engine and are commonly known as black carbon. The diesel particulate filter 106 also incorporate additional functional components targeting sulfate particulates. A pressure sensor is connected across the ends of the diesel particulate filter. The pressure sensor measures the differential pressure across the ends of the diesel particulate filter 106 that increases with an increase in the accumulation of soot within the diesel particulate filter.

[0011] It is required to clean the DPF 106 in a process called regeneration. Collected carbon or soot particulates are removed from the filter, continuously or periodically, through thermal regeneration. This regeneration of the diesel particulate filter 106 is accomplished by programming the engine to run (when the filter is full) in a manner that it elevates the exhaust temperature, in conjunction with an extra fuel injected in the exhaust gas stream. During diesel particulate filter 106 regeneration, upstream of the diesel particulate filter 106, high temperature is required around 600 degrees centigrade for efficient regeneration of the diesel particulate filter. To raise these temperatures late post fuel injections are injected, which is oxidized by the diesel oxidation catalyst that will help to raise the temperature. The diesel particulate filter 106 inlet temperature sensor measures this temperature value at the inlet of the diesel particulate filter 106.

[0012] For the purposes of this disclosure, components having no bearing on the working of the disclosed component have not been elucidated. Their exclusion or inclusion in the exhaust gas treatment system (100) don’t alter the working of the component disclosed in the present disclosure. It should be understood at the outset that, although exemplary embodiments are illustrated in the figures and described below, the present disclosure should in no way be limited to the exemplary implementations and techniques illustrated in the drawings and described below.

[0013] Figure 2 depicts a horizontal cut-section view of an exemplary embodiment of the diesel particulate filter 106. The diesel particulate filter 106 comprises a substrate assembly disposed within a housing. The substrate assembly comprises a longitudinal array of a substrate 1061. The substrate 1061 is affixed along the walls of the housing proximate to the inlet of the diesel particulate filter. The substrate 1061 comprises a honeycomb structure. A guide 1063 is positioned along the longitudinal axis of the diesel particulate filter 106, the guide 1063 positioned within a cavity that is defined within the substrate assembly.

[0014] The length of the substrate 1061 is dependent on the type of vehicle. The length of the substrate 1061 is kept larger in vehicles prone to start-stop or city/off-highway driving conditions. This is because the soot particles emitted in start-stop or city/off-highway driving conditions are larger in size and entrapped by the substrate 1061 with pores of a larger diameter. Similarly, the length of the substrate 1061 is kept smaller in vehicles prone to highway driving conditions as the diameter of the soot emitted in these conditions is smaller, thereby entrapped by the substrate 1061 with smaller pores.

[0015] The guide 1063 comprises a plurality of blades extending radially from the guide 1063 along the longitudinal axis of the guide 1063. Another important non-limiting feature of the present invention is the composition of the plurality of blades. The plurality of blades are made of a shape-memory alloy. Shape-memory alloys are smart materials that can remember their original shapes, and can toggle between the original shape and the deformed shape based on the magnitude of the stimulus applied. There are various stimuli by virtue of which shape-memory alloys work. Some common stimuli include temperature, mechanical load, and chemical load.

[0016] Here a temperature triggered shape-memory alloy is used, wherein the degree of deformation of the shape memory alloy is proportional to the temperature stimulus to which it is subjected. Shape memory alloys mostly prevail in the martensite phase, when they are at low temperatures. When the temperature increases greater than the austenite start temperature also known as critical temperature, the shape memory alloy changes its phase from the martensite phase to the austenite phase. Martensite and austenite each have different lattice sized and crystal structures. When a phase change occurs because of temperature due to internal strain energy that is developed, the crystal structure of the shape-memory alloy alters, thereby altering the shape of the shape-memory alloy. This alteration in the shape of the crystal structure is not a plastic deformation and is a property of the material called “super elasticity” or “pseudo-elasticity”. “Pseudo-elasticity” means that the change in the shape of the shape memory alloy is not a plastic deformation but an elastic deformation, because of the change in the crystal structure (lattice size) and can be recovered to its original shape when the stimulus temperature is withdrawn.

[0017] The plurality of blades extending radially from the guide 1063 are inclined with the longitudinal axis so as to direct the exhaust gas.. At lower temperatures or cold start conditions corresponding to the martensite phase of the shape memory alloy, the plurality of guides 1063 are in the original undeformed state to deflect the exhaust gases towards the substrate 1061 comprising pores to trap soot. At higher temperatures or a highway drive condition corresponding to the austenite phase of the shape memory alloy, the plurality of guides 1063 are deformed to deflect the exhaust gases towards the exhaust gas flow path without passing through the substrate mesh 1061.

[0018] This idea to develop a diesel particulate filter 106 with a substrate 1061, a plurality of shape memory alloy-based blades to guide the exhaust gases not only ensures higher particulate filtration efficiencies at lower temperatures but also provides lower back pressure at high temperature and mass flow rates. The identified shape memory alloy to be used for this purpose is a high-temperature shape memory alloy. These materials exhibit the shape-memory effect at high temperatures of the order of 300 degrees centigrade which is the temperature of the exhaust gas. when it moves into high flow regions.

[0019] It must be understood that the embodiments explained in the above detailed description are only illustrative and do not limit the scope of this invention. Any modification and adaptation to the dimensions and design of the diesel particulate filter are envisaged and form a part of this invention. The scope of this invention is limited only by the claims
, Claims:We Claim:
1. A diesel particulate filter (106) comprising a substrate assembly disposed within a housing, characterized in that device:
the substrate assembly comprising a longitudinal array of a substrate (1061), the substrate mesh (1061) affixed along walls of the housing proximate to an inlet of the diesel particulate filter (106);
a guide (1063) positioned along the longitudinal axis of the diesel particulate filter (106), said guide (1063) positioned within a cavity that is defined within the substrate assembly.

2. The diesel particulate filter (106) as claimed in Claim 1, wherein the substate (1061) comprises a honeycomb structure.

3. The diesel particulate filter (106) as claimed in Claim 1, wherein the guide (1063) comprises a plurality of blades (1064) extending radially from the guide (1063) along the longitudinal axis of the guide (1063).

4. The diesel particulate filter (106) as claimed in Claim 3, wherein the plurality of blades (1064) are made of a shape-memory alloy.

5. The diesel particulate filter (106) as claimed in Claim 3, wherein the plurality of blades (1064) extending radially from the guide 1063 are inclined with respect to a longitudinal axis so as to direct the exhaust gas towards the mesh, behaving like a partial-flow filter.

6. The diesel particulate filter (106) as claimed in Claim 3, wherein the plurality of blades (1064) extending radially from the guide 1063 are undeflected with respect to a longitudinal axis so as to allow the exhaust gas to pass through behaving like a open-flow filter