Description:FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
[See section 10, Rule 13]

“ENGINE SYSTEM AND METHOD OF RECUPERATING EXHAUST GAS RECIRCULATION (EGR) COOLER IN ENGINE SYSTEM”
By
MAHINDRA & MAHINDRA LIMITED, A COMPANY REGISTERED UNDER THE INDIAN COMPANIES ACT, 1913, HAVING ADDRESS AT MAHINDRA RESEARCH VALLEY (MRV), MAHINDRA WORLD CITY, PLOT NO.41/1, ANJUR P.O., CHENGALPATTU, KANCHIPURAM DISTRICT, TAMILNADU – 603004, INDIA

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED
FIELD OF THE INVENTION
The present invention relates generally to a field of engines and more particularly to an engine system and a method of recuperating exhaust gas recirculation (EGR) cooler in engine system.
BACKGROUND OF THE INVENTION
For usage with internal combustion engines, exhaust gas recirculation (EGR) techniques and equipment are well-known. Most EGR systems have at least one EGR valve and, optionally, at least one EGR cooler connected in series between the engine's exhaust and intake systems. A typical EGR system has the capacity to combine some of the engine's exhaust gas with the new air that enters the engine. When exhaust gas is introduced into an engine's intake air stream, it displaces oxygen, resulting in a lower combustion flame temperature and subsequently decreased nitrous oxide (NOx) emissions.
Generally, exhaust gas recirculation cooler is a heat exchanger unit used in internal combustion engines to cool the hot exhaust gas with engine coolant before flowing into the intake manifold and is exposed to the wide degree of factors like temperature, hydrocarbon, soot, water vapour etc. The hot gas flow through heat exchanger tubes causes the inner tube surface to accumulate soot with increasing engine life. In an ideal condition, the soot accumulation hits a threshold and the turbulent gas flow itself acts as a self-regulating process to prevent the further soot build up, hence reaching an equilibrium.
In engine running scenarios such as cold start and short runs, being driven in stop-and-go traffic, not following fuel recommendations, driving patterns initiating frequent diesel particulate regenerations, and so on, the cooler gas surface is exposed to a greater number of cold hydrocarbon in wet state and soot, which together form a lacquer or a hard black soot-based compound under cold temperatures.
Thus, there is need in the art for an engine and a method that improves the performance of the EGR cooler system in the scenarios described above by detecting a clogged condition of EGR cooler’s gas path and recuperating the EGR cooler.
OBJECTIVE OF THE INVENTION
These objectives are provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This objective is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
An important object of the present invention aims at providing a method for detecting a clogged condition of EGR cooler’s gas path and recuperating the EGR cooler.
Another object of the invention is to provide an engine system having a control unit for detecting a clogged condition of EGR cooler’s gas path and recuperating the EGR cooler.
Yet another object of the invention is to provide a flow controller in the coolant outlet path to throttle the coolant flow at high gas temperature.
Another object of the invention is to clean the EGR cooler, so as to maintain the efficiency of the EGR cooler all over the lifetime.
Object of the present invention is not limited to the above-mentioned problem. Other technical problems that are not mentioned will become apparent to those skilled in the art from the following description.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, an engine comprises an exhaust system in fluid communication with a plurality of cylinders of an engine block, the exhaust system includes a turbocharger having a turbine in operable association with a compressor. An intake system in fluid communication with the plurality of cylinders and the compressor, the intake system having an intercooler, an intake throttle, and an intake manifold arranged in series between the compressor and the plurality of cylinders. An exhaust gas recirculation cooler in fluid communication with the exhaust system, the exhaust gas recirculation cooler is configured to cool the flow of exhaust gas passing therein.
Further, the engine comprises an EGR valve, disposed between the EGR cooler and the intake system, the EGR valve is arranged and constructed to control a flow of fluid from the EGR cooler to the intake system. A flow controller configured between the EGR cooler and a coolant pump, the flow controller is connected to the EGR cooler in a series configuration, and a control unit electronically in communication with the flow controller, the intake throttle, a plurality of pressure sensors and a plurality of temperature sensors.
The control unit monitors the pressure ratio between the outlet and inlet of the intake throttle to detect the EGR cooler clogging. If the throttle pressure ratio is higher than a predefined threshold for predefined time, such condition is identified as the EGR cooler clogging condition, and recuperation is activated by the control unit at which high EGR cooler inlet temperature is maintained by the flow controller for vaporising hydrocarbon and cleaning the EGR cooler.
According to an another aspect of the invention, a method of detecting a clogged condition in an exhaust gas recirculation (EGR) cooler’s gas path and recuperating the EGR cooler, the method comprises in the first step monitoring the pressure ratio between outlet and the inlet of the intake throttle to detect the EGR cooler clogging. Further, the method includes in the second step activating recuperation, if the throttle pressure ratio is higher than the predefined threshold for predefined time, and identifying such condition as the EGR cooler clogging condition, and in the final step maintaining high EGR cooler inlet temperature by a flow controller for vaporising the hydrocarbon and cleaning the EGR cooler clogging.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawing, illustrating by way of example the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in greater detail with reference to an embodiment which is illustrated in the following figures:
Figure 1 shows a typical engine system layout for a vehicle, according to an embodiment of the present invention;
Figure 2 is a block diagram showing function flow of a method for detecting a clogged condition of EGR cooler’s gas path and recuperating the EGR cooler, according to an embodiment of the present invention;
Figure 3 is a flow chart of figure 2, according to an embodiment of the present invention; and
Figure 4 is a graph showing the relationship between position of solenoid valve and EGR cooler outlet temperature, according to an embodiment of the present invention.
Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.
DETAILED DESCRIPTION OF THE INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
Figure 1 shows typical engine system layout for a vehicle for detecting a clogged condition in an exhaust gas recirculation (EGR) cooler’s gas path and recuperating the EGR cooler therein. Accordingly, the internal combustion engine system (100) comprises an exhaust system (102), an intake system (104), an exhaust gas recirculation (EGR) cooler (116), an EGR valve (118), a flow controller (120), and a control unit (124). The exhaust system (102) is in fluid communication with a plurality of cylinders of an engine block (106). The exhaust system (102) includes a turbocharger (108) having a turbine in operable association with a compressor. The intake system (104) is in fluid communication with the plurality of cylinders and the compressor. The EGR cooler (116) is in fluid communication with the exhaust system (102) and configured to cool the flow of exhaust gas passing therein. The EGR valve (118) is disposed between the EGR cooler (116) and the intake system (104). The EGR valve (118) is arranged and constructed to control a flow of fluid from the EGR cooler (116) to the intake system (104). The flow controller (120) is configured between the EGR cooler (116) and a coolant pump (122), the flow controller (120) is connected to the EGR cooler (116) in a series configuration. A control unit (124) is electronically in communication with the flow controller (120), the intake throttle (112), a plurality of pressure sensors (p2, p3) and a plurality of temperature sensors (T1, T2, T3, T4, TEGR).
In the internal combustion engine, the pressure ratio between the outlet and inlet of the intake throttle (112) is monitored by the control unit (124) to detect the EGR cooler (116) clogging. If the throttle pressure ratio is higher than the predefined threshold for predefined time, such condition is identified as the EGR cooler (116) clogging condition. Recuperation is activated by the control unit (124) at which high EGR cooler inlet temperature is maintained by the flow controller (120) for vaporising the hydrocarbon and cleaning the EGR cooler (116) clogging.
Table 1 shows maximum allowed or threshold pressure ratio according to an example embodiment of the present invention. The threshold pressure varies as per rated speed and brake torque of the engine. According to a known embodiment, predefined time for detecting the EGR clogged condition can be in the range of ~ 3 to 4 sec.

Table 1: Threshold pressure ratio at rated speed and brake torque
Speed/
Brake torque 1000 rpm 2000 rpm 3000 rpm
50 Nm 2.00 2.20 2.40
100 Nm 2.30 2.45 2.60
200 Nm 2.50 2.60 2.80

The plurality of pressure sensors (p2, p3) according to the invention includes a pressure sensor (p2) mounted at the inlet of the intake manifold (114) and a pressure sensor (p3) mounted at the inlet of intake throttle (112). The plurality of temperature sensors (T1, T2, T3, T4, TEGR) includes a temperature sensor (T1) mounted at the intake of an air filter (126), a temperature sensor (T2) mounted at the inlet of intake throttle (112), a temperature sensor (T3) mounted at the inlet of intake manifold (114), a temperature sensor (T4) mounted at the outlet of exhaust manifold (128) and a temperature sensor (TEGR) mounted at the outlet of EGR cooler (116).
The pressure ratio at the intake throttle (112) is defined as the pressure at the inlet of intake manifold (114) to the pressure at the inlet of intake throttle (112). Alternatively, the pressure ratio at the intake throttle (112) can also be defined as the pressure at the outlet and inlet of the intake throttle (112).
According to an embodiment of the present invention the flow controller (120) is a solenoid valve. The solenoid valve operation and activation sequence are electronically controlled by the control unit (124) with a close looping input from an EGR gas temperature sensor (TEGR).
In the turbocharger (108), the compressor has an air inlet connected to an air cleaner or filter (126), and a charge air outlet connected to a charge air intercooler (110) through charge air intercooler hot passage. The charge air intercooler (110) has an outlet connected to the intake throttle valve (112) through a charge air intercooler cold passage. The intake throttle valve (112) is connected to an intake manifold (114) that fluidly communicates with an intake system (104) of the engine. Branches of the intake system (104) are fluidly connected to each of a plurality of cylinders that are included in a crankcase / engine block (106) of the engine.
Each of the plurality of cylinders of the engine is connected to an exhaust system (102). The exhaust system (102) of the engine is connected to an inlet of the turbine in the turbocharger. An exhaust manifold (128) is connected to an outlet of the turbine. Other components, such as an exhaust after treatment system (130), a muffler (132), catalyst, particulate filter, and so forth, may be connected to the exhaust pipe but are not shown in figure 1 for the sake of simplicity.
Figure 2 shows a block diagram and figure 3 shows a flow chart of function flow of a method for detecting a clogged condition of EGR cooler’s gas path and recuperating the EGR cooler in the engine system, according to an embodiment of the present invention. The method comprises in the initial step (202) monitoring the pressure ratio at the intake throttle to detect the EGR cooler clogging. According to a preferred embodiment of the present invention, the pressure ratio at the throttle is defined as the pressure at the outlet to the pressure at the inlet of the intake throttle. In the next step (204), identifying the clogging in the EGR cooler based on a determination that the throttle pressure ratio is higher than a predefined threshold for predefined time. In the further step (206), activating recuperation on identifying the clogging in the EGR cooler. In the final step (208), maintaining high EGR cooler inlet temperature by a flow controller for vaporising the hydrocarbon and cleaning the EGR cooler clogging.
The detection of EGR cooler recuperation is based on the pressure ratio across the throttle (112). In ideal conditions, the throttle (112) will close in order to maintain the required EGR pressure ratio and a certain amount of EGR flow through the EGR. When the cooler (116) is clogged, the EGR ratio required to achieve the same amount of EGR flow as in the fresh condition increases, resulting in increased throttle (112) closure and a high-pressure ratio across the throttle.
The pressure ratio required by the throttle (112) to maintain the EGR pressure ratio and thus the EGR flow is monitored in this method. The pressure ratio across the throttle is monitored, and if it exceeds some pre-defined thresholds defined by the control unit (124) for a certain period of time, the EGR cooler recuperation function will activate and start controlling the EGR coolant flow. This function runs for the time specified by the control unit (124) as shown in figure 1, after which the normal flow through the EGR will resume. Also, this function is governed by variables such as EGR temperature and exhaust temperature. If any of these values exceed the thresholds, the function shall terminate.
According to the present invention, the hydrocarbon (HC) can be recovered intermittently by allowing the exhaust gas recirculation cooler to operate at a lower efficiency. Maintaining lower cooler efficiency raises the overall cooler wall temperature and thus the soot HC layer on the gas side of the cooler plates, higher temperature accelerates hydrocarbon vaporisation and slow burning of the deposited soot, resulting in recuperation. The method used in this invention to keep the cooler running at a lower efficiency is to regulate the engine coolant flow rate to the exhaust gas recirculation cooler.
According to an example embodiment of the present invention, the high EGR cooler inlet temperature is attained by reducing the coolant flow to the EGR cooler (116) up to 50 to 70 % by the flow controller. By regulating the flow of coolant into the EGR cooler (116) the high temperature is achieved in the EGR cooler (116). Figure 4 is a graph that shows the relationship between position of solenoid valve (120) and EGR cooler outlet temperature (TEGR), according to an embodiment of the present invention.
For the recuperation function, the EGR cooler gas temperature is defined at each speed load point in the flow controller. Usually, this temperature is 50 to 100 °C higher than the typical working range. Depending on the engine running condition, the average temperature of the EGR cooler gas is kept between 250 and 300 °C when the recovery function is active. The sludge that has built up inside the EGR cooler (116) is subjected to heavy thermal stresses at this temperature. The hydrocarbon component of the sludge is vaporised and the EGR cooler (116) is cleaned as a result, so as to maintain the efficiency of the EGR cooler (116) all over the lifetime.
The method of the present invention detects clogged condition of an exhaust gas recirculation cooler’s gas path due to combustion soot accumulation and recuperates the cooler performance through heating up of the gas path by controlling the coolant flow rate, preventing the exhaust gas recirculation failure.
While the preferred embodiment of the invention has been illustrated and described herein, it is to be understood that the invention is not limited to the precise construction herein disclosed, and the right is reserved to all changes and modifications coming within the scope of the invention.
Although there has been shown and described the preferred embodiment of the present invention, it will be readily apparent to those skilled in the art that modifications may be made thereto which do not exceed the scope of the appended claims. Therefore, the scope of the invention is only to be limited by the following claims.
, Claims:
1. An engine system (100), comprising:
an exhaust system (102) in fluid communication with a plurality of cylinders of an engine block (106), the exhaust system (102) includes a turbocharger (108) having a turbine in operable association with a compressor;
an intake system (104) in fluid communication with the plurality of cylinders and the compressor, the intake system (104) having an intercooler (110), an intake throttle (112), and an intake manifold (114) arranged in series between the compressor and the plurality of cylinders;
an exhaust gas recirculation (EGR) cooler (116) in fluid communication with the exhaust system (102), the EGR cooler (116) is configured to cool the flow of exhaust gas passing therein;
an EGR valve (118), disposed between the EGR cooler (116) and the intake system (104), the EGR valve (118) is arranged and constructed to control a flow of fluid from the EGR cooler (116) to the intake system (104);
a flow controller (120) configured between the EGR cooler (116) and a coolant pump (122), the flow controller (120) is connected to the EGR cooler (116) in a series configuration; and
a control unit (124) electronically in communication with the flow controller (120), the intake throttle (112), a plurality of pressure sensors (p2, p3) and a plurality of temperature sensors (T1, T2, T3, T4, TEGR);
wherein, the pressure ratio across the intake throttle (112) is monitored by the control unit (124) to detect the EGR cooler (116) clogging, if the throttle pressure ratio is higher than a predefined threshold for predefined time, such condition is identified as the EGR cooler clogging condition, and recuperation is activated at which high EGR cooler inlet temperature is maintained by the flow controller (124) for vaporising hydrocarbon and cleaning the EGR cooler (116).
2. The engine system (100) as claimed in claim 1, wherein the flow controller (120) is a solenoid valve.
3. The engine system (100) as claimed in claim 1, wherein the plurality of pressure sensors (p2, p3) includes a pressure sensor (p3) mounted at the inlet of the intake manifold (114) and a pressure sensor (p2) mounted at the inlet of intake throttle (112).
4. The engine system (100) as claimed in claim 1, wherein the pressure ratio is defined as the pressure at the inlet of intake manifold (114) to the pressure at the inlet of intake throttle (112).
5. The engine system (100) as claimed in claim 1, wherein the plurality of temperature sensors (T1, T2, T3, T4, TEGR) includes a temperature sensor (T1) mounted at the intake of an air filter (126), a temperature sensor (T2) mounted at the inlet of intake throttle (112), a temperature sensor (T3) mounted at the inlet of intake manifold (114), a temperature sensor (T4) mounted at the outlet of exhaust manifold (128) and a temperature sensor (TEGR) mounted at the outlet of EGR cooler (116).
6. A method (200) of detecting a clogged condition in an exhaust gas recirculation (EGR) cooler’s gas path and recuperating the EGR cooler (116) in an engine system, the method comprising the steps of:
monitoring (202) pressure ratio across an intake throttle to identify clogging in the EGR cooler (116);
identifying (204) the clogging in the EGR cooler (116) based on a determination that the throttle pressure ratio is higher than a predefined threshold for predefined time;
activating (206) recuperation on identifying the clogging in the EGR cooler (116); and
maintaining (208) high EGR cooler inlet temperature by a flow controller for vaporising the hydrocarbon and cleaning the EGR cooler clogging.
7. The method (200) as claimed in claim 5, wherein the pressure ratio is defined as the pressure at an inlet of intake manifold (114) to the pressure at an inlet of intake throttle (112).
8. The method (200) as claimed in claim 5, wherein the operation of the flow controller (120) is in close loop with a temperature sensor (TEGR) mounted at the outlet of EGR cooler (116) to control the flow of coolant.
9. The method (200) as claimed in claim 5, wherein the operating and activating sequence of flow controller (120) is electronically controlled by a control unit (124).
10. The method (200) as claimed in claim 5, wherein the high EGR cooler inlet temperature is in the range of 250-300 °C and is attained by reducing the coolant flow to the EGR cooler (116) up to 50 to 70 %.