DESC:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

COMPLETE SPECIFICATION

(See Section 10 and Rule 13)

Title of invention:
AN EXHAUST AFTER TREATMENT SYSTEM FOR AN ENGINE

Applicant:
BEML Limited
A company Incorporated in India under the Companies Act, 1956
Having address:
BEML Soudha, 23/1, 4th Main,
Sampangirama Nagar, Bengaluru - 560 027,
Karnataka, India

The following specification particularly describes the invention and the manner in which it is to be performed.

CROSS-REFERENCE TO RELATED APPLICATION AND PRIORITY
[001] The present application claims priority from Indian Patent application no. (202041003351) filed on 24th January, 2020.

TECHNICAL FIELD
[002] The present subject matter described herein, in general, relates to an exhaust after treatment system for an engine and more specifically to an exhaust gas bypass system.
BACKGROUND
[003] The exhaust gas emitted from an internal combustion engine such as but not limiting to diesel engines and some configurations of gasoline engines, is a heterogeneous mixture that may contain gaseous emissions such as carbon monoxide (“CO”), unburned hydrocarbons (“HC”) and oxides of nitrogen (“NOx”) as well as condensed phase materials (liquids and solids) that constitute particulate matter. If the particulate matter is passed to the surroundings directly, there is a high risk of environmental and health problems.
[004] Stringent regulatory requirements and increasing environmental concerns are driving new technological developments in exhaust after treatment systems. A Diesel Oxidation Catalyst (DOC), a Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR) are the exhaust after treatment system catalysts to reduce emission from Diesel engines to achieve regulatory requirements. Similarly a three way catalyst and gasoline particulate filters are primarily being used for this purpose in gasoline engines. The DPF effectively removes the particulate matter in the exhaust gas before passing it into the surroundings. However, the DPF is a physical structure for removing particulates from exhaust gas and, it results in the accumulation of filtered particulates. Further, accumulation of particulate matter after a certain level will have the effect of increasing the exhaust system backpressure experienced by the engine. This is due to the clogging of the filters by accumulation of particulate matter. To address backpressure caused by the accumulation of exhaust gas particulates, the DPF should be periodically cleaned or burnt by passing exhaust gas. The process of cleaning or burning of the accumulated particulate matter on the DPF is called regeneration. The optimum temperature for regeneration of non-catalyzed DPF is above 550 °C for burning of carbon (soot) loaded in the DPF and around 350 °C for the DPF loaded with catalyst. The working temperature for DOC is 200 to 450 °C and the maximum efficiency will be at around 350 °C. But in conventional Diesel engines, during low load conditions, the exhaust gas temperature after turbocharger is less than 300 °C and the air fuel ratio will be very high then the ideal stoichiometric ratio.
[005] In order to increase the temperature of exhaust gas for after-treatment, different methodologies has been carried out like, late injection, post injection, intake air flow reduction (before turbocharger by throttle), intake air flow reduction after turbocharger and exhaust throttling. These methodologies have some disadvantages as below.
[006] Intake throttling of compressor inlet- To increase the exhaust temperature, the air flow which is entering the turbocharger compressor is restricted by throttle valve, through electronic control based on input from the required sensors or data from engine ECU. If there is more restriction in the intake air to the compressor of the turbocharger, it leads to oil entry in to the compressor from bearing housing. This leads to bearing or oil seal failure of the turbocharger and also due to the oil entry, the engine exhaust emission will increase.
[007] Intake throttling of compressor outlet- To increase the exhaust temperature, the air flow which is going out from the turbocharger compressor is restricted by throttle valve, through electronic control based on input from the required sensors or data from engine ECU. If there is more restriction after the compressor of the turbocharger and due to mismatch in controlling of throttle valve, surging of the turbocharger takes place. This leads to the failure of bearing or compressor rotor of the turbocharger.
[008] Exhaust throttling in the tail pipe- To increase the exhaust temperature, exhaust flow is restricted in the tail pipe by throttle valve. Due to this, engine back pressure get increased and hence the pumping losses get increased.
[009] Late injection or post injection- This is possible only with help of electronic control injection system like CRDI (Common Rail Direct Injection System). This leads to engine oil deterioration and is not fuel efficient.
[0010] The present subject matter discloses a novel exhaust system to overcome the limitations stated above.
OBJECT OF THE INVENTION
[0011] It is an object of the present invention to increase exhaust gas temperature for efficient after treatment process.
[0012] It is another object of the present invention to enable bypassing the exhaust gases to the exhaust after treatment system before entry to the turbocharger.
[0013] It is another object of the present invention to achieve passive regeneration in the DPF completely or up to some extent.
SUMMARY
[0014] Before the present system and method are described, it is to be understood that this application is not limited to the particular machine or an apparatus, and methodologies described, as there can be multiple possible embodiments that are not expressly illustrated in the present disclosures. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope of the present application. This summary is provided to introduce aspects related to an exhaust after treatment system for an engine, and the aspects are further elaborated below in the detailed description. This summary is not intended to identify essential features of the proposed subject matter nor is it intended for use in determining or limiting the scope of the proposed subject matter.
[0015] The present subject matter discloses an exhaust after treatment system for an engine. The exhaust after treatment system is comprises an Oxidation Catalyst, a Particulate Filter, a Selective Catalytic Reduction filter and a passage. The Oxidation Catalyst is configured to receive exhaust gases from an exhaust manifold of the engine through a turbocharger. The Particulate Filter is configured to receive the exhaust gases from the Oxidation Catalyst. The Selective Catalytic Reduction filter is configured to receive the exhaust gases from the Particulate Filter. The passage is configured to allow flow of exhaust gases from the exhaust manifold to the Oxidation Catalyst before entering into turbocharger.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The foregoing summary, as well as the following detailed description of embodiments, is better understood when read in conjunction with the appended drawing. For the purpose of illustrating the disclosure, there is shown in the present document example constructions of the disclosure, however, the disclosure is not limited to the specific methods and apparatus disclosed in the document and the drawing:
[0017] The detailed description is described with reference to the accompanying figure. In the figure, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawing to refer like features and components.
[0018] Figure 1 illustrates an exhaust after treatment system for an engine, in accordance with one embodiment of the present subject matter.
[0019] The figure depicts various embodiments of the present disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following discussion 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
[0020] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "comprising", “having”, and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. Although any systems and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the exemplary, systems and methods are now described. The disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms.
[0021] Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure is not intended to be limited to the embodiments illustrated, but is to be accorded the widest scope consistent with the principles and features described herein.
[0022] An internal combustion engine consumes fuel and air to produce mechanical energy to drive a vehicle or for any other operation. The engine also produces exhaust gases as a result of burning the fuel and air. These exhaust gases comprise harmful gases like NOx, CO, HC and PM. There are various emission norms as per standards of a particular country. Due to stringent emission norms, exhaust after treatment catalysts like Diesel Oxidation Catalyst (OC), Diesel Particulate Filter (PF) and Selective Catalytic Reduction (SCR) is becoming mandatory requirement for diesel engines. The catalysts should be at maximum efficiency during most of the operation time to get the emission result and also for downsizing the catalyst size for better packaging. Due to varying environmental and equipment operating conditions, achieving optimum temperature for the catalysts like DOC, DPF and SCR is difficult. The working temperature for DOC catalyst is 200 to 450 °C and the maximum efficiency will be at around 350 °C. The optimum temperature for non-catalyzed DPF is above 550 °C for burning of carbon (soot) loaded in the DPF and around 350 °C for the DPF loaded with catalyst. In conventional Diesel engines, during low load conditions, the exhaust temperature after turbocharger is less than 300 °C and the air fuel ratio will be very high then the stoichiometric ratio. The present subject matter discloses an effective and innovative system to maintain optimum temperature for exhaust after treatment system of the internal combustion engine.
[0023] Referring to figure 1, in one aspect of the invention, an exhaust after treatment system 100 for an engine 10 is disclosed. The engine 10 comprises an intake manifold 12 and an exhaust manifold 14 to receive intake charge and to release exhaust gases respectively. The exhaust gases are passed to a tail pipe 16 through a turbocharger 18 and the exhaust after treatment system 100. The exhaust after treatment system 100 comprises a Diesel oxidation catalyst (DOC) 110, a Diesel particulate filter (DPF) 120, a selective catalytic reduction (SCR) filter 130, a temperature sensor 140 and an electronic control valve 150. The exhaust gases from the exhaust manifold 14 is passed through the turbocharger 18 to enable compression of intake charge by rotation of turbine in the turbocharger 18. Further the exhaust gases from the turbocharger 18 is supplied to the exhaust after treatment system 100 where the DOC 110 oxidizes the hydrocarbons, carbon monoxide and unburned fuel and oil present in the exhaust gases. The DPF 120 traps any remaining soot that DOC 110 couldn’t oxidize. The soot remains in the DPF 120 until it is regenerated. The SCR 130 introduces Diesel Emissions Fluid (DEF) into the stream of exhaust gases to cause reduction of nitrogen oxides in the exhaust gases that pass through to the SCR filter 130.
[0024] In an embodiment of the present subject matter, a passage 160 is configured between the exhaust manifold 14 and the exhaust after treatment system 100 and thereby the passage 160 is configured for bypassing a specific amount of exhaust gases directly to the DOC 110. The electronic control valve 150 is configured to be installed in the passage 160 to allow flow of exhaust gases to be bypassed to the DOC 110. A control unit 200 is configured to control the electronic control valve 150 based on plurality of engine parameters. The control unit 200 is configured to receive the plurality of engine parameters like exhaust temperature, engine speed, fuel flow and mass air flow or lambda (stoichiometric ratio) from respective sensors. In an embodiment, the control unit 200 may be an engine control unit. The exhaust temperature is detected by the temperature sensor 140 installed at upstream of the DOC 110 to detect the temperature of exhaust gases entering into the DOC 110.
[0025] A total amount of exhaust gases from the exhaust manifold 14 is divided into two streams; one passing through the turbocharger 18 and one passing through the passage 160 directly supplied to the exhaust after treatment system 100. The exhaust gases passing through the turbocharger 18 loses some of the heat in the process of rotating the turbine of the turbocharger 18. Therefore the exhaust gas supplied to the DOC 110 through the passage 160, bypassing the turbocharger 18, has a higher temperature than that through the turbocharger 18 which results into improved efficiency of the exhaust after treatment system 100.
[0026] The temperature of the bypassed exhaust gas is around 100 °C higher at maximum load condition and around 30 °C higher at low load conditions than the exhaust gas passed through the turbocharger 18. During low temperature conditions, the electronic control valve is configured to allow more amount of exhaust gases through the passage 160 to ensure an optimum temperature of exhaust gases required for the exhaust after treatment system is maintained. Similarly during high temperature conditions the electronic control valve is configured to close the passage 160 to allow passage of whole exhaust gas through the turbocharger 18. Therefore during low temperature conditions, the exhaust temperature will be increased without affecting the turbocharger or engine oil deterioration or back pressure. The higher temperature of the exhaust gases is suitable for effective regeneration of the particulate filter and for heating up the catalyst element of the oxidation catalyst. The temperature of the exhaust gases entering into the exhaust after treatment system will be near to optimum condition or at least higher than the earlier, hence performance of the exhaust after treatment system will be better than earlier.
[0027] The present subject matter discloses an exhaust after treatment system (100) for an engine (10). The exhaust after treatment system (100) is comprises an Diesel Oxidation Catalyst (110), a Diesel Particulate Filter (120), a Selective Catalytic Reduction filter (130) and a passage (160). The Diesel Oxidation Catalyst (110) is configured to receive exhaust gases from an exhaust manifold (14) of the engine (10) through a turbocharger (18). The Diesel Particulate Filter (120) is configured to receive the exhaust gases from the Diesel Oxidation Catalyst (110). The Selective Catalytic Reduction filter (130) is configured to receive the exhaust gases from the Diesel Particulate Filter (120). The passage (160) is configured to divert the exhaust gases from the exhaust manifold (14) to the Diesel Oxidation Catalyst (110) for bypassing the turbocharger (18). The exhaust gases received by the Diesel Oxidation Catalyst (110) through the passage (160) is configured with higher temperature than the exhaust gases received through the turbocharger (18).
[0028] The exhaust gases through the passage (160) is configured to be regulated by an electronic control valve (150). Further the electronic control valve (150) is configured to be controlled by a control unit (200) based on plurality of engine parameters. The plurality of engine parameters are configured to be exhaust temperature, engine speed, fuel flow and mass air flow or lambda (stoichiometric ratio). In an embodiment, the control unit (200) is an engine control unit. The exhaust temperature is configured to be detected by a temperature sensor (140) installed at upstream of the Diesel Oxidation Catalyst (110).
[0029] Further, by-passing the exhaust gas from the turbocharger leads to suffocation of the air to the engine and hence more fuel intake in the system. This helps to increase the engine exhaust gas temperature thereby regeneration of DPF (120) will be made easy.
[0030] Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include those provided by the following features.
[0031] Some embodiments of the subject matter enable to increase exhaust gas temperature for efficient after treatment process.
[0032] Some embodiments of the subject matter enable bypassing the exhaust gases to the exhaust after treatment system before entry to the turbocharger.
[0033] Some embodiments of the subject matter enable to achieve passive regeneration in the DPF completely or up to some extent.
[0034] Although implementations for the exhaust after treatment system 100 have been described in language specific to structural features and/or methods, it is to be understood that the appended claims are not necessarily limited to the specific features described. Rather, the specific features are disclosed as examples of implementation for the exhaust after treatment system 100.

,CLAIMS:
1. An exhaust after treatment system (100) for an engine (10) wherein the exhaust after treatment system (100) is comprising:
a Diesel Oxidation Catalyst (110) configured to receive exhaust gases from an exhaust manifold (14) of the engine (10) through a turbocharger (18);
a Diesel Particulate Filter (120) configured to receive the exhaust gases from the Oxidation Catalyst (110);
a Selective Catalytic Reduction filter (130) configured to receive the exhaust gases from the Particulate Filter (120); and
a passage (160) configured to divert the exhaust gases from the exhaust manifold (14) to the Diesel Oxidation Catalyst (110) for bypassing the turbocharger (18).

2. The exhaust after treatment system as claimed in claim 1, wherein the exhaust gases, received by the Diesel Oxidation Catalyst (110) through the passage (160), is with higher temperature than the exhaust gases received through the turbocharger (18).

3. The exhaust after treatment system as claimed in claim 1, wherein the exhaust gases through the passage (160) is configured to be regulated by an electronic control valve (150).

4. The exhaust after treatment system as claimed in claim 2, wherein the electronic control valve (150) is configured to be controlled by a control unit (200) based on plurality of engine parameters.

5. The exhaust after treatment system as claimed in claim 4, wherein the plurality of engine parameters are configured to be exhaust temperature, engine speed, fuel flow and mass air flow or lambda (stoichiometric ratio).

6. The exhaust after treatment system as claimed in claim 5, wherein the exhaust temperature is configured to be detected by a temperature sensor (140) installed at upstream of the Diesel Oxidation Catalyst (110).

7. The exhaust after treatment system as claimed in claim 4, wherein the control unit (200) is configured to be an engine control unit.