Claims:We claim,
1. A method 100 for starting an engine10 having at least one cylinder, said method 100 comprising:
cranking the engine10 and inducting charge inside at least one corresponding cylinder of the engine10;
compressing the inducted charge without injection of fuel in at least one corresponding cylinder of the engine 10 for a plurality of cycles by maintaining cranking the engine 10;
injecting fuel into at least one corresponding cylinder of the engine10 immediately after compression of the inducted charge for the plurality of cycles, and detecting partial burnt charge in at least one corresponding cylinder of the engine10 which occurs in a misfiring cycle;
retaining the partially burnt charge in at least one corresponding cylinder of the engine10 by maintaining at least one corresponding intake valve 20I and at least one corresponding exhaust valve 20E in a closed position on detection of partial burnt charge in the misfiring cycle in at least one corresponding cylinder of the engine 10;
compressing the retained partially burnt charge in at least one corresponding cylinder of the engine10 which occurs in a subsequent compression stroke, and combusting the partially burnt charge in at least one corresponding cylinder of the engine10; and
injecting fuel into at least one corresponding cylinder of the engine 10immediately after combustion of the partially burnt charge to facilitate sustained combustion of the fuel in at least one corresponding cylinder of the engine 10which occurs in a first firing cycle thereby starting the engine 10.
2. The method 100 as claimed in claim 1, wherein the method step of compressing the inducted charge without injection of fuel in at least one corresponding cylinder of the engine 10 for the plurality of cycles by maintaining cranking the engine 10 is based on at least one of ambient temperature of air, engine parameters, fuel parameters, fuel injection parameters, starting aids, engine configuration and cooling system which are being determined by a controller unit 200C.

3. The method 100 as claimed in claim 1 comprises a step of actuating at least one corresponding fuel injector 22 by the controller unit 200C when a predetermined fuel pressure is generated in at least one fuel rail prior to the method step of injecting the fuel into at least one corresponding cylinder of the engine 10 immediately after compression of the inducted charge for the plurality of cycles, and detecting partial burnt charge in at least one corresponding cylinder of the engine 10 which occurs in the misfiring cycle.

4. The method 100 as claimed in claim 1, wherein the partial burnt charge generated in at least one corresponding cylinder of the engine 10 in the misfiring cycle as detected by the controller unit 200 C is based on at least one of instantaneous speed of the engine 10, pressure in corresponding at least one cylinder of the engine10 and temperature in corresponding at least one cylinder of the engine 10.

5. The method 100 as claimed in claim 1 is for cold starting the engine 10, wherein the engine 10is a compression ignition engine having low compression ratio.

6. The method 100 as claimed in claim 1, wherein the compression ignition engine is a low compression ratio diesel engine.

7. A system 200 for cold starting an engine 10, said system 200 comprising, a controller unit 200C configured to:
induct a charge inside at least one corresponding cylinder of the engine 10 by maintaining at least one corresponding intake valve 20I in an open position and at least one exhaust valve 20E in a closed position;
compress the inducted charge without injection of fuel in at least one corresponding cylinder of the engine 10 for a plurality of cycles by at least one of maintaining at least one corresponding intake valve 20I and at least one corresponding exhaust valve 20E in the closed position, and maintaining cranking the engine 10;
inject the fuel into at least one corresponding cylinder of the engine 10 immediately after compression of the inducted charge for the plurality of cycles by actuating at least one corresponding fuel injector 22, and detect partial burnt charge in at least one corresponding cylinder of the engine 10 which occurs in a misfiring cycle;
retain the partially burnt charge in at least one corresponding cylinder of the engine 10 by maintaining at least one corresponding intake valve 20I and at least one corresponding exhaust valve 20E in the closed position on detection of partial burnt charge in misfiring cycle in at least one corresponding cylinder of the engine 10;
compress the retained partially burnt charge in corresponding at least one cylinder of the engine 10 which occurs in a subsequent compression stroke by maintaining corresponding at least one intake valve 20I and corresponding at least one exhaust valve 20E in the closed position, and combusting the partially burnt charge in corresponding at least one cylinder of the engine 20; and
inject fuel into corresponding at least one cylinder of the engine 10 by actuating corresponding at least one fuel injector 22 immediately after combustion of the partially burnt charge to facilitate sustained combustion of the fuel in corresponding at least one cylinder of the engine 10 which occurs in a first firing cycle thereby starting the engine 10.

8. The system 200 as claimed in claim 7, wherein compression of the inducted charge without injection of fuel in at least one corresponding cylinder of the engine 10 for the plurality of cycles by at least one of maintaining at least one corresponding intake valve 20I and at least one corresponding exhaust valve 20E in the closed position, and maintaining cranking the engine 10 is based on at least one of ambient temperature of air, engine parameters, fuel parameters, fuel injection parameters, starting aids, engine configuration and cooling system which are being determined by said controller unit 200C.

9. The system 200 as claimed in claim7, wherein said controller unit 200C actuates corresponding at least one fuel injector 22 when a predetermined fuel pressure is generated in the fuel rail,
wherein the partial burnt charge generated in corresponding at least one cylinder of the engine 10 in the misfiring cycle as detected by said controller unit 200 C based on at least one of instantaneous speed of the engine 10, pressure in corresponding at least one cylinder of the engine 10 and temperature in corresponding at least one cylinder of the engine 10.

10. The system 200C as claimed in claim 7, wherein the engine 10 is a compression ignition engine having low compression ratio,
wherein the engine 10 is at least a low compression ratio diesel engine.

, Description:TECHNICAL FIELD
[001] The embodiments herein generally relate to engines and more particularly, to a method and a system for cold starting a compression ignition engine such as low compression ratio diesel engine and the like.
BACKGROUND
[002] Diesel engine is a type of compression ignition engine which ignite fuel by compressing a quantity of air in a combustion chamber during a compression stroke in which a piston compresses the air within the combustion chamber and the heat generated by the compression of the air increases the temperature within the combustion chamber. Once the temperature in the combustion chamber surpasses a threshold level, fuel injected into the combustion chamber ignites which generates high pressure gases that act on the piston to enable reciprocating movement of the piston which in turn causes a crankshaft of the diesel engine to rotate thereby propelling the vehicle. However, the temperature of the air in the combustion chamber at the end of the compression stroke also depends on the temperature of the air entering the combustion chamber prior to the compression stroke. During cold weather, the temperature of the air entering the combustion chamber may be low enough that the temperature rise in the combustion chamber during the compression stroke is not sufficient to raise the temperature of the combustion chamber above the threshold temperature. Under such conditions, the engine will not start or run. Increasing the temperature of the air advanced into the combustion chamber prior to the compression stroke will increase the temperature in the combustion chamber during the compression stroke and cause the injected fuel to ignite in the combustion chamber. In addition, even under conditions where the fuel does ignite, the temperature in the combustion chamber may not be high enough to completely combust all of the injected fuel in the combustion chamber. The unburned fuel, also known as unburned hydrocarbons, is exhausted into the atmosphere. These unburned hydrocarbons are a visible form of pollution known as white smoke. Current emission standards limit the amount of unburned hydrocarbons that can be emitted during the operation of the diesel engine. In addition, emission standards may limit the quantity of unburned hydrocarbons that can be emitted into the atmosphere during cold start-up conditions and warm up conditions. Increasing the temperature of the air in the combustion chamber prior to the compression stroke will also decrease the amount unburned hydrocarbons advanced into the atmosphere during cold start-up conditions.
[003] Low compression ratio is being preferred in modern diesel engines in order to meet nitric oxide emissions and lower urea consumption in vehicles fitted with selective catalyst reduction system. However, during starting the lower temperatures achieved towards the end of the compression stroke with either low ambient temperatures, low compression ratios or a combination of both will not favor auto ignition and thus start ability of the engine will be impaired. To meet emission legislation limits and desired cold start ability with low compression ratios in diesel engines is difficult and is one of the challenges posed to the original equipment manufacturers (OEM).
[004] Hence, diesel engines have used several devices to increase the temperature of the air advanced into the combustion chamber prior to the compression stroke. These devices include air pre-heaters which heat the air in the intake manifold prior to the air being advanced to the combustion chamber. These pre-heaters add cost and complexity to the design of the diesel engine as the pre-heater requires a fuel burner or electrical heating element to heat the air in the intake manifold. Another solution is to use glow plugs to heat the combustion chamber prior to ignition to improving the conditions inside the engine. These glow plugs incur added cost and packaging and arrangement of the glow plug adds complexity to the design of the diesel engine. Another solution is to use block heater, which heats the engine block prior to ignition to reduce the problem of cold starting. Incorporation of block heater in engine block incurs high cost and is complex in design and increases an overall weight of the engine. Another solution is to use a coolant heater to heat the engine coolant that surrounds the cylinders. Heating the cylinder walls also increases the temperature of the air in the cylinder. The added cost and complexity of a fuel burner or electrical heating element is required to heat the coolant in the diesel engine. Yet another solution, fuels with lower ignition temperatures, such as ether can be advanced to the combustion chamber to initiate ignition of the diesel fuel. Again, additional costly and complex equipment is required to store a separate fuel that is used only during cold start-up conditions. Other solutions include circulating oil heaters, circulating coolant heaters, coolant line heater and engine oil pan heater. However, these devices incur high cost and packaging and arrangement of the aforementioned devices adds complexity to the design of the diesel engine and increases an overall weight of the engine.
[005] Other conventional systems and methods for cold starting of the diesel engine would require a design change in the engine, and/or the systems associated with the engine thereby making the design complex and may lead to difficulties in packaging and arrangement of the components present in the engine and/or the systems associated with the engine and incurs high cost.
[006] Therefore, there exists a need for a method and a system for cold starting a compression ignition engine (low compression ratio diesel engine and the like), which obviates the aforementioned drawbacks.
OBJECTS
[007] The principal object of an embodiment of this invention is to provide a method for cold starting a compression ignition engine such as low compression ratio diesel engine and the like.
[008] Another object of an embodiment of this invention is to provide a system for cold starting a compression ignition engine such as low compression ratio diesel engine and the like.
[009] Another object of an embodiment of this invention is to provide a method for cold starting a compression ignition engine, which reduces the emission of unburnt pollutants (such as unburnt hydrocarbons and the like) during startup emission test and warm-up conditions.
[0010] These and other objects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the 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 of the invention are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the 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 schematic diagram of an engine and a system for cold starting the engine, according to an embodiment of the invention as disclosed herein;
[0013] Fig. 2 depicts a flowchart showing the steps of a method for cold starting an engine such as low compression ratio diesel engine and the like, according to an embodiment of the invention as disclosed herein; and
[0014] Fig. 3 depicts a graph plot between engine speed, crank angle and cylinder pressure in the engine for the system which implements the steps of the method for cold starting the engine, according to an embodiment of the invention as disclosed herein.

DETAILED DESCRIPTION
[0015] 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.
[0016] The embodiments herein achieve a method for cold starting a compression ignition engine such as low compression ratio diesel engine and the like. Further, embodiments herein achieve a system for cold starting a compression ignition engine such as low compression ratio diesel engine and the like. Referring now to the drawings, and more particularly to fig. 1 to fig.3, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0017] Fig. 1 depicts a schematic diagram of an engine 10 and a system 200 for cold starting the engine 10, according to an embodiment of the invention as disclosed herein. The engine 10 includes an air intake conduit 12, an air filter 14, a thermocouple 16, a cylinder head 18, an intake valve actuating mechanism 20, at least one fuel injector 22, an exhaust valve actuating mechanism 24, a cylinder block 26, at least one piston 28, at least one connecting rod 30, a crankshaft 32, a crankcase 33, a crankshaft position sensor 34, an exhaust conduit 36, a plurality of sensors (not shown)and may include other standard components as present in a standard engine assembly.The engine 10 is a compression ignition engine such as low compression ratio diesel engine and the like. In an embodiment, the engine 10 is a single cylinder engine. In another, embodiment, the engine 10 is a multi-cylinder engine. The air intake conduit 12 is used for supplying the atmospheric air to corresponding at least one cylinder of the engine 10. The air filter 14 is provided in the air intake conduit 12 for filtering the air prior to supplying the air to the cylinder of the engine 10.The thermocouple 16 is provided in communication with a controller unit 202C. The intake valve actuating mechanism 20 is used to actuate the intake valve 20I to control the position of the intake valve 20I between at least one of an open position and a closed position based on the signal received from the controller unit 202C. The intake valve actuating mechanism 20 is at least one of a mechanical intake valve actuating mechanism, an electro-hydraulic intake valve actuating mechanism, an electro-pneumatic intake valve actuating mechanism, and an electric and electronic intake valve actuating mechanism. The fuel injector 22 is used to inject the fuel into the cylinder of the engine 10 based on the signal from a controller unit 202C. The exhaust valve actuating mechanism 24 is used to actuate the exhaust valve 20E to control the position of the exhaust valve 20E between at least one of an open position and a closed position based on the signal received from the controller unit 202C. The exhaust valve actuating mechanism 20 is at least one of a mechanical intake valve actuating mechanism, an electro-hydraulic intake valve actuating mechanism, an electro-pneumatic intake valve actuating mechanism, and an electric and electronic intake valve actuating mechanism. The piston 28 is slidably connected with corresponding cylinder of the engine 10. The connecting rod 30 is used for connecting the piston 28 to the crankshaft 32. The crankshaft 32 is mounted in the crankcase 33 of the engine 10. The crankcase 33 is connected to the bottom of the cylinder block 26 for housing the crankshaft 32 and other standard components of the engine 10. The crankshaft position sensor 34 is used to determine the angular position of the crankshaft 32 and the position of the piston 28 in the corresponding cylinder of the engine 10 and provides the information to the controller unit 202C. The exhaust conduit 36 is used to facilitate discharge of exhaust gases from the engine 10. The plurality of sensors (not shown) includes in-cylinder pressure sensor and temperature sensors, which are provided in communication with the controller unit 202C.
[0018] In an embodiment, the system 200 for cold starting the engine 20 comprises a controller unit 200Cconfigured to, induct a charge (air) inside at least one corresponding cylinder of the engine 10 which occurs in an intake stroke by maintaining at least one corresponding intake valve 20I in an open position and at least one exhaust valve 20E in a closed position; compress the inducted charge without injection of fuel in at least one corresponding cylinder of the engine 10 for a plurality of cycles (compression cycles) by maintaining at least one corresponding intake valve 20I and at least one corresponding exhaust valve 20E in the closed position, and maintaining cranking the engine 10 based on the ambient temperature of air, engine parameters, fuel parameters, fuel injection parameters, starting aids, engine configuration and cooling system which are being determined (evaluated) by the controller unit 200C through corresponding sensors (not shown); inject the fuel into at least one cylinder of the engine 10 immediately after compression of the inducted charge for the plurality of cycles (compression cycles) by actuating at least one corresponding fuel injector 22 when a predetermined fuel pressure is generated in the fuel rail, and detecting partial burnt charge in corresponding at least one cylinder of the engine 10 which occurs in a misfiring cycle based on at least one of instantaneous speed of the engine 10, pressure in corresponding at least one cylinder of the engine 10 and temperature in corresponding at least one cylinder of the engine 10 which are being determined by the controller unit 200C through corresponding sensors (not shown);retain the partially burnt charge in corresponding at least one cylinder of the engine 10 by maintaining at least one corresponding intake valve 20I and at least one corresponding exhaust valve 20E in a closed position on detection of partial burnt charge in misfiring cycle in corresponding at least one cylinder of the engine 10; compress the retained partially burnt charge in corresponding at least one cylinder of the engine 10 which occurs in subsequent compression stroke by maintaining corresponding at least one intake valve 20I and corresponding at least one exhaust valve 20E in the closed position, and combusting the partially burnt charge in corresponding at least one cylinder of the engine 20 thereby increasing the in-cylinder temperature and pressure in corresponding at least one cylinder of the engine 10; and inject fuel into corresponding at least one cylinder of the engine 10 by actuating corresponding at least one fuel injector 22 immediately after combustion of the partially burnt charge to facilitate instantaneous and sustained combustion of the fuel in corresponding at least one cylinder of the engine 10 which occurs in a first firing cycle thereby producing sufficient high work output and aids in starting the engine 10.
[0019] In an embodiment, the controller unit 200C is an engine control unit. In another embodiment, the controller unit 200C is a separate control unit. The controller unit 200C is operatively connected to the engine 10. The controller unit 200C actuates at least one intake valve 20I and at exhaust valve 20E through corresponding intake valve actuating mechanism 20 and exhaust valve actuating mechanism 24 of the engine 10 to control the valve opening and closing timings based on the requirements. The controller unit 200C is provided in communication with corresponding at least one fuel injector 22 of the engine 10 to control the fuel injection based on the requirements. The controller unit 200C controls the valve arrangement based on at least one of instantaneous speed of the engine 10, cylinder pressure, intake charge temperature, position of the crankshaft 32 in the engine 10, type of fuel and in combination with any other starting aid. The controller unit 202C is provided in communication with the crankshaft position sensor 34 of the engine 10. The controller unit 202C is provided in communication with corresponding sensors (not shown) provided in the engine 10 and corresponding systems associated with the engine 10. After first firing cycle, the controller unit 202C may move on to normal valve timing or to any warm up sequence of valve timing and injection schedule.
[0020] Fig. 2 depicts a flowchart showing the steps of a method 100 for cold starting an engine10 such as low compression ratio diesel engine and the like, according to an embodiment of the invention as disclosed herein. For the purpose of this description and ease of understanding, the method 100 for cold starting an engine 10 is explained herein below with reference to compression ignition engines such as low compression ratio diesel engine and the like. It is also within the scope of the invention to practice/implement the entire steps of the method 100 or with omission of at least one step of the method 100 or with any addition of at least one step to the method 100 for cold starting of the engine 10, any other type of compression ignition engine and any other type of engine.In an embodiment, the method 100 for cold starting the engine 10 such as low compression ratio diesel engine and the like is as follows, the method 100 comprises, cranking the engine 10 and inducting charge inside at least one corresponding cylinder of the engine 10 which occurs in an intake stroke (step 102); compressing the inducted charge without injection of fuel in at least one corresponding cylinder of the engine 10 for a plurality of cycles (compression cycles) by maintaining cranking the engine10 (step 104);injecting the fuel into at least one cylinder of the engine 10 immediately after compression of the inducted charge for the plurality of cycles (compression cycles), and detecting partial burnt charge in corresponding at least one cylinder of the engine 10 which occurs in a misfiring cycle (step 106);retaining the partially burnt charge in corresponding at least one cylinder of the engine 10 by maintaining at least one corresponding intake valve 20I and at least one corresponding exhaust valve 20E in a closed position on detection of partial burnt charge in misfiring cycle in corresponding at least one cylinder of the engine10 (step 108); compressing the retained partially burnt charge in corresponding at least one cylinder of the engine 10 which occurs in subsequent compression stroke, and combusting the partially burnt charge in corresponding at least one cylinder of the engine 10 thereby increasing the in-cylinder temperature and pressure in corresponding at least one cylinder of the engine 10 (step 110); and injecting fuel into corresponding at least one cylinder of the engine 10 immediately after combustion of the partially burnt charge to facilitate sustained combustion of the fuel in corresponding at least one cylinder of the engine 10 which occurs in a first firing cycle thereby producing sufficient high work output and aids in starting the engine10 (step 112). The method step of compressing the inducted charge (air) without injection of fuel in at least one corresponding cylinder of the engine 10 for the plurality of cycles (compression cycles) by maintaining cranking the engine 10 is based on the ambient temperature of air, engine parameters, fuel parameters, fuel injection parameters, starting aids, engine configuration and cooling system which are being determined (evaluated) by a controller unit 200C (also called as engine control unit), wherein at least one corresponding intake valve 20I and at least one corresponding exhaust valve 20E is controlled and maintained in a closed position by the controller unit during compression of the inducted charge (air) for the plurality of compression cycles. The method 100 further comprises a step of actuating corresponding at least one fuel injector 22 by the controller unit 200C when a predetermined fuel pressure is generated in the fuel rail prior to the method step of injecting the fuel into at least one cylinder of the engine 10 immediately after compression of the inducted charge for the plurality of compression cycles, and detecting partial burnt charge in corresponding at least one cylinder of the engine 10 which occurs in the misfiring cycle, wherein the partial burnt charge which is occurred in the misfiring cycle in corresponding at least one cylinder of the engine 10 is detected by the controller unit 200C based on at least one of instantaneous speed of the engine, pressure in corresponding at least one cylinder of the engine 10 and temperature in corresponding at least one cylinder of the engine 10.
[0021] Fig. 3 depicts a graph plot between engine speed, crank angle and cylinder pressure in the engine 10 for the system 200 which implements the steps of the method 100 for cold starting the engine 10, according to an embodiment of the invention as disclosed herein. Experiments were conducted in a reference diesel engine for the system 200 which implements the steps of the method 100 for cold starting the engine 10. The results of the experiment are summarized in Fig. 3 which includes instantaneous engine speed, cylinder pressure and injector current with respect to crank angle. In these experiments cylinder pressure and injector current data were used only for measurement purpose. The curve A in the graph represents the speed of the engine 10. The curve B in the graph represents the pressure in cylinder of the engine 10. The plot C in the graph represents the injection current of the fuel injector 22 of the engine 10.As can be deduced from the graph, it is clearly understood that the charge (air) which is inducted in the cylinder in a suction stroke is compressed for a plurality of compression cycles to raise the temperature of the charge due to low temperature of the charge (air) in cold conditions. Thereafter, when the fuel is injected in the cylinder in a first fuel injection (F1) leads to misfiring of the charge (air and fuel) in the cylinder as the temperature of air is not sufficient enough to ignite entirety of the fuel thereby producing partially burnt charge in a misfiring cycle. Controller unit 202C identifies the misfiring cycle, using the change in engine speed after fuel injection (?N2) which is within the threshold limits. Thereafter, the partially burnt charge which is occurring in the misfiring cycle is retained in subsequent exhaust stroke, thereafter the retained partially burnt charge is compressed and combusted in subsequent compression stroke which results in increase in the pressure and temperature inside the cylinder of the engine 10 (as can be deduced from curve B). Thereafter, when the fuel is injected in the cylinder of the engine 10 in the second fuel injection (F2) immediately after the combustion of the partially burnt charge, the injected fuel ignites instantaneously to facilitate sustained combustion of the fuel which occurs in a first firing cycle (proper firing), where ?N3 is above the misfiring threshold levels (i.e., ?N3 >> ?N2) thereby producing sufficient high work output, increases the speed of the engine 10 (as can be deduced from the curve A) and aids in starting the engine 10 during cold conditions.
[0022] Therefore, a method 100 and a system 200 for cold starting a compression ignition engine such as low compression ratio diesel engine and the like, which effectively uses the partially burnt charge in misfiring cycle for aiding starting the engine 10 and reduces the emission of unburnt pollutants (unburnt hydrocarbon) by retaining the unburnt fuel within the cylinder during startup emission test and warm-up conditions is provided for the engine 10.
[0023] 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 modification within the spirit and scope of the embodiments as described herein.