Claims:We claim:
1. A system (100) for controlling exhaust gas recirculation in an engine, said system (100) comprising:
a controller unit (102);
an EGR control valve (104) adapted to be provided in communication with said controller unit (102);
an exhaust gas temperature sensor (106) adapted to detect the exhaust gas temperature of the engine and provides the information to said controller unit (102); and
an engine speed sensor (108) adapted to detect the operating speed of the engine and provides the information to said controller unit (102),
wherein
said controller unit (102) is adapted to determine the operating load of the engine based on the measured exhaust gas temperature; and
said controller unit (102) controls said EGR control valve (104) to control exhaust gas recirculation to the engine based on the operating load and operating speed of the engine.

2. The system (100) as claimed in claim 1, wherein said controller unit (102) is configured to:
check if the measured exhaust gas temperature is between at least one first pre-defined exhaust gas temperature value and at least one second pre-defined exhaust gas temperature value; and
select at least one operating load associated with a combination of the at least one first pre-defined exhaust gas temperature value and the at least one second pre-defined exhaust gas temperature value.

3. The system (100) as claimed in claim 2, wherein said controller unit (102) is configured to:
match the measured exhaust gas temperature with a value in a look up table to determine the operating load point and a corresponding predetermined exhaust gas recirculation valve opening percentage is mentioned in another table which determines the rate of flow of exhaust gas recirculation to the engine; and
control the flow of the exhaust gas re-circulation to the engine for the calculated at least one operating load, the predetermined exhaust gas recirculation valve opening percentage and the operating speed of the engine based on the measured exhaust gas temperature and engine speed.

4. A method (200) for controlling exhaust gas recirculation to an engine, said method (200) comprising:
detecting an operating speed of the engine through an engine speed sensor (108);
detecting an exhaust gas temperature through an exhaust gas temperature sensor (106);
determining an operating load of the engine through a controller unit (102) based on the measured exhaust gas temperature; and
controlling exhaust gas re-circulation to the engine through an EGR control valve (104) when the EGR control valve (104) receives information from the controller unit (102) based on the operating load and operating speed of the engine.

5. The method (200) as claimed in claim 4, wherein said determining an operating load of the engine through the controller unit (102) based on the measured exhaust gas temperature comprises,
checking if the measured exhaust gas temperature is between at least one first pre-defined exhaust gas temperature value and at least one second pre-defined exhaust gas temperature value;
selecting at least one load point associated with a combination of the at least one first pre-defined exhaust gas temperature value and at least one second pre-defined exhaust gas temperature value; and
matching by, the controller unit (102), the measured exhaust gas temperature with a value in a look up table to determine the operating load point and a corresponding predetermined exhaust gas recirculation valve opening percentage is mentioned in another table which determines the rate of flow of exhaust gas recirculation to the engine for the calculated operating load point and the operating speed of the engine.
, Description:TECHNICAL FIELD
[001] The embodiments herein generally relate to exhaust gas re-circulation in an engine and more particularly, to a system and a method for controlling exhaust gas re-circulation in an all speed governed engine based on operating load and speed of the engine, where the operating load is determined through exhaust gas temperature.

BACKGROUND
[002] During the operation of an internal combustion engine (hereinafter called as engine), certain pollutants are emitted out in the exhaust gases. These gases generally consist of oxides of nitrogen (NOx), carbon monoxide (CO) and un-burnt particulate matter (PM). Emission of such pollutants is majorly based on the operating conditions of the engine and the power output of the engine. Due to the harmful nature of these pollutants, the government regulatory bodies have emission norms, which all the engines have to be complying to.
[003] Exhaust gas re-circulation (EGR) is a technique commonly used for controlling the generation of undesirable pollutant gases during the operation of engine. This technique has proven particularly useful in engines used in motor vehicles such as passenger cars, light duty trucks, and other on-road motor equipment. The exhaust gas re-circulation technique primarily involves the re-circulation of exhaust gas by-products into the intake air supply of engine. This exhaust gas thus reintroduced in to the engine cylinder reduces the concentration of oxygen therein, which in turn lowers the maximum combustion temperature within the cylinder and slows the chemical reaction of the combustion process, decreasing the formation of nitrous oxide. Furthermore, the exhaust gases typically contain a portion of unburned hydrocarbon which is burned on its reintroduction into the engine cylinder, which further reduces the emission of exhaust gas by-products which would be emitted as undesirable pollutants from the engine. Therefore, it is required to control the quantities of exhaust gas in exhaust gas recirculation system to reduce NOx emission with proper combustion.
[004] Controlling the EGR flow rate based on engine operating load is critical for meeting the emission requirements and is difficult and is one of the challenges posed to the original equipment manufacturers (OEMs).
[005] Therefore, there exists a need for a system and a method for controlling exhaust gas re-circulation to an engine, which obviates the aforementioned drawbacks.

OBJECTS

[006] The principal object of embodiments herein is to provide a system for controlling exhaust gas re-circulation in an engine based on operating load and speed of the engine, where the operating load is determined through exhaust gas temperature of the engine.
[007] Another object of embodiments herein is to provide a method for controlling exhaust gas re-circulation in an engine.
[008] Another object of embodiments herein is to provide a system which accurately controls exhaust gas re-circulation in an engine to reduce nitrous oxide emissions from engine during different operating conditions.
[009] Another object of embodiments herein is to provide a system for controlling exhaust gas re-circulation in an engine, which reduces the hydrocarbon (HC) and nitrous oxide (NOx) emissions from the engine during dual fuel operation.
[0010] These and other objects of embodiments herein will be better appreciated and understood when considered in conjunction with following description and accompanying drawings. It should be understood, however, that the following descriptions, while indicating embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF DRAWINGS
[0011] The embodiments are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0012] Fig. 1 depicts a block diagram of a system for controlling exhaust gas re-circulation in an engine, according to embodiments as disclosed herein; and
[0013] Fig. 2 depicts a flowchart indicating a method for controlling exhaust gas re-circulation in the engine, according to embodiments as disclosed herein.

DETAILED DESCRIPTION
[0014] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0015] The embodiments herein achieve a system and a method for controlling exhaust gas re-circulation to an engine based on operating load and speed of the engine, where the operating load is determined through exhaust gas temperature of the engine. Referring now to the drawings Figs 1 through 2, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0016] Fig. 1 depicts a block diagram of the system (100) for controlling exhaust gas re-circulation to the engine, according to embodiments as disclosed herein. The system (100) is used for controlling the exhaust gas re-circulation in the engine to control oxides of nitrogen (NOx) and hydrocarbons (HC) emissions from the engine. In an embodiment, the system (100) includes a controller unit (102), an exhaust gas re-circulation control valve (104), hereinafter referred to as EGR control valve), an exhaust gas temperature sensor (106) and an engine speed sensor (108). For the purpose of this description and ease of understanding, the system (100) herein is explained herein with below reference to controlling exhaust gas re-circulation in an all speed governed diesel engine present in a vehicle to control nitrous oxide (NOx) and hydrocarbons (HC) emissions from the engine. However, it is also within the scope of the invention to practice/implement the system (100) for controlling exhaust gas re-circulation in any of a petrol engine, a hybrid engine, a dual fuel engine or any speed governed engines or any other type of engine present in a vehicle or a machine, where control in NOx and HC is required, without otherwise deterring the intended function of the system (100) as can be deduced from the description and corresponding drawings.
[0017] The controller unit (102) is adapted to determine the operating load of the engine based on the measured exhaust gas temperature. The controller unit (102) controls the EGR control valve (104) to control exhaust gas recirculation to the engine based on the operating load and operating speed of the engine. For example, the controller unit (102) controls the opening of the EGR control valve (104) based on operating load and operating speed of the engine. The controller unit (102) is provided in communication with the EGR control valve (104), the exhaust gas temperature sensor (106) and the engine speed sensor (108). In an embodiment, the controller unit (102) includes but not limited to a processor, a micro-controller, a memory, a storage unit, an input output unit, a display unit and so on. In an embodiment, the controller unit (102) can be a dedicated control unit. In another embodiment, the controller unit (102) can be an electronic control unit present in the vehicle, which performs other functions related to the vehicle or one or more systems/sensors/modules present in the vehicle, other than according to embodiments as disclosed herein. The controller unit (102) may also include or have access to memory or databases (not shown) which include at least one lookup table providing information about requirement of exhaust gas recirculation at different operating load points and operating speed of engine, pre-defined exhaust gas temperature values and corresponding operating load points and so on.
[0018] The controller unit (102) is configured to control flow of exhaust gas re-circulation to the engine based on the measured operating parameters. On receiving the operating parameters of the engine, the controller unit (102) uses the measured exhaust gas temperature to calculate an operating load point (a load point at which the engine operates). The controller unit (102) checks if the measured exhaust gas temperature is between first pre-defined exhaust gas temperature value(s) and second pre-defined exhaust gas temperature value(s). On determining that the measured exhaust gas temperature is between the first pre-defined exhaust gas temperature value and the second pre-defined exhaust gas temperature value, the controller unit (102) selects the operating load point (a load point at which the engine operates) associated with the combination of the first and second pre-defined exhaust gas temperature values. Thus, the operating load point can be selected based on the exhaust gas temperature.
[0019] Once the operating load point is selected, the controller unit (102) matches the measured exhaust gas temperature with a value(s) in at least one look up table(s) to determine the operating load point, and a corresponding predetermined exhaust gas recirculation valve opening percentage is mentioned in another table, which determines the rate of flow of the exhaust gas recirculation to the engine for the calculated operating load point and the operating speed of the engine and accordingly, the controller unit (102) controls the rate of the flow of the exhaust gas recirculation to the engine based on the predetermined exhaust gas recirculation valve opening percentage, the calculated operating load point and the operating speed of the engine. Furthermore, with different speed (rpms) of the engine, the exhaust gas recirculation varies for the same rpm based on calibration. Thus, the flow of the exhaust gas recirculation to the engine can be controlled to reduce NOx emissions. The look up table is stored in the memory unit (not shown) of the controller unit (102). The look up table contains information about but not limited to predefined exhaust gas temperature value(s). Further, the lookup tables may provide information about requirement of exhaust gas recirculation at different operating load points and engine operating speed, pre-defined exhaust temperature values and corresponding operating load points and so on. The look up table may include other operating parameters of the engine which would be required in controlling exhaust gas recirculation to the engine.
[0020] The EGR control valve (104) is provided in communication with the controller unit (102). The EGR control valve (104) controls the flow of exhaust gas re-circulation to the engine based on the signal received from the controller unit (102). For the purpose of this description and ease of understanding, the EGR control valve (104) is considered to be a progressive EGR control valve. However, it is also within the scope of the embodiments herein to provide any other type of EGR control valves, where controlling of exhaust gas re-circulation is required, without otherwise deterring the intended function of the EGR control valve (104) as can be deduced from the description and corresponding drawings.
[0021] The exhaust gas temperature sensor (106) is adapted to detect the temperature of exhaust gas from engine and provides the information to the controller unit (102). The engine speed sensor (108) is adapted to detect the operating speed of the engine and provides the information to the controller unit (102).
[0022] In dual fuel operation, when the engine is operating on a combination of primary fuel which is compression ignition based and a secondary fuel which is Spark ignition based, (mostly primary fuel used is diesel, while secondary fuel is gas which could be CNG, LPG etc.) it was observed that, with the use of EGR, alongside NOx there was some reduction in HC emission also, due to recirculation of combustible gases in the exhaust and increase in in-cylinder temperature which assists in better combustibility of fuel. Thus, in dual fuel operation, use of EGR helps in controlling both HC and NOx. With better load identification using exhaust gas temperature, better emission control is achieved.
[0023] Fig. 2 depicts a flowchart indicating a method (200) for controlling exhaust gas re-circulation in the engine, according to embodiments as disclosed herein. For the purpose of this description and ease of understanding, the method (200) is explained herein below with reference to controlling exhaust gas re-circulation in an all speed governed diesel engine present in a vehicle to nitrous oxide (NOx) and hydrocarbons (HC) emissions from the engine. However, it is also within the scope of this invention to practice/implement the entire steps of the method (200) in a same manner or in a different manner or with omission of at least one step to the method (200) or with any addition of at least one step to the method (200) for controlling exhaust gas re-circulation in any of a petrol engine, a hybrid engine, a dual fuel engine or any other type of engine present in a vehicle or a machine, where control in NOx and HC is required, without otherwise deterring the intended function of the method (200) as can be deduced from the description and corresponding drawings. In an embodiment, the method (200) includes, detecting an operating speed of the engine through an engine speed sensor (108), step (202), detecting an exhaust gas temperature through an exhaust gas temperature sensor (106), step (204), determining an operating load of the engine through a controller unit (102) based on the measured exhaust gas temperature, step (206) and controlling exhaust gas re-circulation to the engine through an EGR control valve (104) when the EGR control valve (104) receives information from the controller unit (102) based on the operating load and operating speed of the engine, step (208).
[0024] The method step (206) of determining an operating load of the engine through a controller unit (102) based on the measured exhaust gas temperature comprises, checking by, the controller unit (102), if the measured exhaust gas temperature is between at least one first pre-defined exhaust gas temperature value and at least one second pre-defined exhaust gas temperature value, and selecting at least one load point associated with a combination of the at least one first pre-defined exhaust gas temperature value and at least one second pre-defined exhaust gas temperature value and matching by, the controller unit (102), the measured exhaust gas temperature with a value in a look up table to determine the operating load point, and a corresponding predetermined exhaust gas recirculation valve opening percentage is mentioned from another table which determines the rate of flow of the exhaust gas recirculation to the engine for the calculated operating load point and the operating speed of the engine.
[0025] Therefore, a system (100) and a method (200) which accurately re-circulates exhaust gas to an engine based on operating load and speed of the engine to reduce nitrous oxide (NOx) and hydrocarbons (HC) emissions and to improve fuel economy of a vehicle is provided.
[0026] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modifications within the spirit and scope of the embodiments as described herein.