DESC:TECHNICAL FIELD
[001] The embodiments herein generally relate to an internal combustion engine and, more particularly, to an injection system and a piston designed for use in a compression ignition (diesel) internal combustion engine and a method of operating the internal combustion engine.

BACKGROUND
[002] Automobile engines include diesel engines, gasoline engines, natural gas engines, and other engines. These engines produce exhaust having complex mixture of air pollutants. The air pollutants may be composed of gaseous compounds, which include nitrogen oxides, and solid particulate matter, which includes unburned hydrocarbon particulates called soot.
[003] Due to increased attention on the atmosphere, the standards for exhaust emission have become more stringent. The amount of air pollutants emitted from an engine may be regulated depending on the type of engine, size of engine, and/or class of engine. Some methods that have been implemented by engine manufacturers to comply with the regulation of air pollutants exhausted to the atmosphere to reduce these pollutants. Unfortunately, reducing particulate matter emissions often comes at the expense of efficiency properties such as fuel efficiency and/or attainable engine speed and power.
[004] Generally, diesel engines produce more particulate matter/soot emissions along with other combustion by products such as carbon di oxide (CO2), oxides of nitrogen (NOX), hydrocarbon (HC) and carbon monoxide (CO) due to their heterogeneous combustion. Controlling of soot emissions is difficult as the conventional strategies used for controlling soot leads to increase in NOX emissions. Homogenous charge compression ignition (HCCI) and premixed charge compression ignition (PCCI) are some of the strategies used for controlling soot and NOX emissions, in which soot formation is reduced by creating homogenous mixture for combustion, while NOX emissions are reduced by reduction of peak temperature. However, HCCI and PCCI are inefficient in controlling HC and CO emissions due to over leaning of mixtures and lower peak temperatures. Further, HCCI and PCCI strategies lead to knocking due to early injection of fuel and affect the lubrication of engine due to increase in diesel oil dilution because of spray impingement on the cylinder wall of the engine. Furthermore, the HCCI and PCCI have restrictions in operating at higher load due to difficulty in controlling the equivalence ratio.
[005] Further, one area of extensive research and experimentation in combustion science is to adapt the shape a piston combustion face in such a way that certain exhaust emissions, including particulate matter emissions, are reduced without unduly sacrificing efficiency. Such piston designs are known in the art. One such piston design includes a combustion bowl defined by the combustion face of the piston exposed to and defining a portion of the engine combustion chamber when placed in service. It is believed that combustion bowls, and certain bowl geometries, can affect the combustion properties of gases. Many such combustion bowl designs are directed to reducing one or both of oxides of nitrogen (NOx) and particulate matter.
[006] Therefore, there exists a need for an injection system and a piston with an optimized piston bowl design in internal combustion engines for reducing exhaust emissions. Furthermore, there exists a need for a piston with an optimized piston bowl design that can eliminate the aforementioned drawbacks.

OBJECTS
[007] The principal object of an embodiment of this invention is to provide an injection system and a piston designed for use in a compression ignition (diesel) internal combustion engine.
[008] Another object of an embodiment of this invention is to provide a piston with an optimized piston bowl design for an internal combustion engine for reducing exhaust emissions.
[009] Yet another object of an embodiment of this invention is to provide a method of operating an internal combustion engine using optimized piston bowl design.
[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 perspective view of a piston of an engine according to the embodiments of the invention as disclosed herein;
[0013] FIG. 2 depicts a top view of the piston of the engine according to the embodiments of the invention as disclosed herein;
[0014] FIG. 3 depicts a cross sectional view of the piston of the engine according to the embodiments of the invention as disclosed herein; and
[0015] FIG. 4 depicts a flowchart of a method of operating an internal combustion engine using optimized piston bowl design according to the embodiments of the invention as disclosed herein.

DETAILED DESCRIPTION
[0016] 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.
[0017] The embodiments herein achieve an injection system and a piston designed for use in a compression ignition (diesel) internal combustion engine. Further, embodiments herein achieve a piston with an optimized piston bowl design for an internal combustion engine for reducing exhaust emissions. Referring now to the drawings, and more particularly to FIGS. 1 through 4, where similar reference characters denote corresponding features consistently throughout the figures there are shown embodiments.
[0018] In an embodiment, the internal combustion engine (not shown) used for description is a four-stroke diesel engine. However, any type of engine (for example, a four-stroke diesel engine, a two- or four-stroke gasoline engine, or a two- or four-stroke gaseous fuel-powered engine) can be used along with the embodiments as discussed herein.
[0019] In an embodiment, the combustion system includes a piston 101, a piston crown 103, a piston bowl 105, a combustion chamber (not shown), a cylinder (not shown), a connecting rod (or a rod) and a crankshaft (not shown).
[0020] In an embodiment, the piston 101 may be configured to reciprocate between a bottom-dead-center (BDC) or lower-most position, and a top-dead-center (TDC) or upper-most position within the combustion chamber (not shown). In an embodiment, the piston 101 is assembled to the crankshaft (not shown). The crankshaft of engine may be rotatably disposed within an engine block (not shown) and the piston 101 is coupled to crankshaft by the rod (not shown) so that a sliding motion of the piston 101 within the cylinder results in a rotation of the crankshaft. As the crankshaft rotates through about 180 degrees, the piston 101 and the connected rod makes one full stroke between the BDC and the TDC.
[0021] FIG. 1 depicts a perspective view of the piston 101 of an engine according to the embodiments of the invention as disclosed herein. In an embodiment, the piston crown 103 is defined on the piston 101. The piston crown 103 includes the piston bowl 105 on an outer surface of the piston 101 having a top face facing the combustion chamber (not shown). In an embodiment, the piston bowl 105 includes a lip portion 107, a re-entrant portion 109, a toroidal portion 111 and a central conical portion 113. Collectively, the lip portion 107, the re-entrant portion 109, the toroidal portion 111 and the central conical portion 113 may promote efficient mixing of the air and fuel, in combustion chamber (not shown). In an embodiment, the piston bowl 105 may provide a compression ratio of about 16.0:1 and 19.0:1 within the cylinder (not shown). In an embodiment, the compression ratio of 16.0:1 is used in the internal combustion engine as discussed herein.
[0022] In an embodiment, the lip portion 107 of the piston bowl 105 includes an upper lip surface 107a, and a lower lip surface 107b. Further, the lip portion 107 includes the re-entrant portion 109 defined between the upper lip surface 107a and the lower lip surface 107b. In an embodiment, the lip portion 107 includes an outer radius R1 and an inner radius R2. In an embodiment, the outer radius R1 ranges from 1.2 mm to 1.4 mm and the inner radius R2 ranges from 2.2 mm to 2.4 mm. In an embodiment, the re-entrant portion 109 includes a throat. The throat includes a throat radius r ranging from 22 mm to 23.4 mm. In an embodiment, the throat radius r is defined as the space between the piston bowl edge and a central axis of piston. Further, the re-entrant portion 109 includes a re-entrancy ratio ranging from 0.9 to 0.94.
[0023] FIG. 2 depicts a top view of the piston of the engine according to the embodiments of the invention as disclosed herein. In an embodiment, the piston bowl 105 further includes the annular toroidal portion 111 extending from the lower lip surface 107b. In an embodiment, the annular toroidal portion 111 includes a maximum bowl depth Dp ranging from 12.8 mm to 13.2 mm and a maximum bowl radius R ranging from 4 mm to 4.2 mm. In an embodiment, the maximum bowl depth is defined as the maximum depth Dp from the piston top surface, to the bottom point in the piston bowl. In an embodiment, the piston bowl toroidal radius R is defined as the maximum radius which occupies most of the piston bowl volume. In an embodiment, the toroidal radius R ranges from 4 mm to 4.2 mm. In an embodiment, major portion of the diesel combustion occurs in the toroidal radius portion 111. Further, the toroidal portion 111 includes a maximum bowl diameter. In an embodiment, the maximum bowl diameter Dm is defined as largest bowl diameter which is parallel to the piston top surface at any position along the piston bowl cross section.
[0024] FIG. 3 depicts a cross sectional view of the piston of the engine according to the embodiments of the invention as disclosed herein. In an embodiment, the piston bowl 105 further includes the central conical portion 113 (also referred as dome portion) located about the central axis of piston. In an embodiment, the conical portion 113 is connected to the annular toroidal portion 111. In an embodiment, the central conical portion 113 includes a center pip depth dp and the radius Rr (not shown). In an embodiment, the center pip depth dp is distance between piston top surface and top most point in the piston bowl bottom surface. In an embodiment, the center pip depth dp ranges from 4.2 mm to 4.6 mm and the radius Rr ranges from 18 mm to 20 mm. In an embodiment, the conical portion 113 may surround the central axis of piston.
[0025] In an embodiment, the engine includes the combustion chamber which further includes at least one intake port (not shown) for air intake into the combustion chamber having swirling effect during operation, the swirl effect having a swirl ratio ranging from 1.5 to 2.
[0026] In an embodiment, the combustion system includes the fuel injector (not shown) located above the top dead center position of the combustion chamber. In an embodiment, the fuel injector includes a fuel injector nozzle body (not shown). In an embodiment, the nozzle body includes a plurality of fuel injection holes (not shown). In an embodiment, the fuel injection holes (not shown) are disposed substantially equidistantly around a centerline of the fuel injector nozzle body. In an embodiment, the plurality of fuel injection holes in the nozzle body ranges from 7 to 9.
[0027] In an embodiment, the fuel injector nozzle body is positioned at a centerline of the nozzle to impinge the fuel on the lower lip surface 107b during the injection. In an embodiment, the fuel injector includes an injector flow ranging from 500 cc/min to 560 cc/min. In an embodiment, the fuel injection holes within the nozzle body are configured to deliver fuel at an angle between about 147? to 150? degrees. In an embodiment, the lip portion 107 provided in the piston bowl 105 is configured to direct the fuel spray towards the cylinder head in a squish zone to burn unused fuel available at the squish zone.
[0028] In an embodiment, the fuel injector further includes nozzle tip protrusion (NTP) defined as a distance between cylinder head bottom surface and a vertical cut section to the center line of fuel injector nozzle body which includes the plurality of fuel injection holes, wherein the distance of NTP ranges from 1.55 mm to 1.9 mm.
[0029] FIG. 4 depicts a flowchart of a method 400 of operating an internal combustion engine using optimized piston bowl design according to the embodiments of the invention as disclosed herein. In an embodiment, the method 400 of operating an internal combustion engine includes, rotating a crankshaft of the internal combustion engine in an engine cycle such that a piston 101 coupled with the crankshaft is moved between a bottom dead center position and a top dead center position within a combustion chamber (step 401). The method further includes, injecting a fuel directly into the combustion chamber using a fuel injector such that the fuel is injected after the piston 101 has passed the top dead center position in the engine cycle (step 403). Furthermore, the method includes, directing fuel injected after the piston has passed the top dead center position to impinge upon the lip portion 107 (step 405). In addition the method includes, auto igniting a mixture containing the injected fuel and air within the combustion chamber (step 407).
[0030] 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.

Referral numerals:
Piston 101
Piston crown 103
Piston bowl 105
Lip portion 107
Re-entrant portion 109
Toroidal portion 111
Conical portion 113
Center pip depth dp
Maximum depth of bowl Dp
Maximum bowl diameter Dm
Outer radius of lip R1
Inner radius of lip R2
Throat radius r
Toroidal radius R
,CLAIMS:STATEMENT OF CLAIMS
We claim,
1. An internal combustion engine for low emissions during combustion, comprising:
a piston 101 provided within a combustion chamber to reciprocate between a bottom dead center position and a top dead center position of the combustion chamber;
a piston crown 103 defined in the piston 101 having a top face facing the combustion chamber;
a piston bowl 105 defined within the piston crown 103,
wherein
the piston bowl 105 includes:
a lip portion 107 having an upper lip surface 107a and a lower lip surface 107b, a re-entrant portion 109 defined between the upper lip surface 107a and the lower lip surface 107b,
an annular toroidal portion 111 extending from the lower lip surface 107b, and a conical portion 113 located about a central axis of piston, wherein the conical portion 113 is connected to the annular toroidal portion 111;
and
a fuel injector located above the top dead center position of the combustion chamber having a fuel injector nozzle body, wherein the nozzle body includes a plurality of fuel injection holes, the fuel injection holes are disposed substantially equidistantly around a centerline of the fuel injector nozzle body.

2. The internal combustion engine for low emissions as claimed in claim 1, wherein the piston bowl 105 further includes:
the lip portion 107 having an outer radius R1 and an inner radius R2;
wherein the outer radius R1 ranges from 1.2 mm to 1.4 mm and the inner R2 ranges from 2.2 mm to 2.4 mm;
the re-entrant portion 109 includes a throat radius r ranging from 22 mm to 23.4 mm and a re-entrancy ratio ranging from 0.9 to 0.94;
the toroidal portion 111 defining a maximum bowl depth Dp ranging from 12.8 mm to 13.2 mm and a radius R ranging from 4 mm to 4.2 mm; and
the central conical portion 113 having a center pip depth dp and a radius Rr, wherein the the center pip depth dp ranges from 4.2 mm to 4.6 mm and the radius Rr ranges from 18 mm to 20 mm.

3. The internal combustion engine for low emissions as claimed in claim 1, wherein the combustion chamber further includes at least one intake port for air intake into the combustion chamber having swirling effect during operation, the swirl effect having a swirl ratio ranging from 1.5 to 2.

4. The internal combustion engine for low emissions as claimed in claim 1, wherein the fuel injector nozzle body is positioned at a centerline of the nozzle body to impinge the fuel on the lower lip surface 107b during the injection.

5. The internal combustion engine for low emissions as claimed in claim 1, wherein the fuel injector includes an injector flow which ranges from 500 cc/min to 560 cc/min.

6. The internal combustion engine for low emissions as claimed in claim 1, wherein the fuel injector further includes nozzle tip protrusion (NTP) defined as a distance between cylinder head bottom surface and a vertical cut section to the center line of fuel injector nozzle body which includes the plurality of fuel injection holes, wherein the distance of NTP ranges from 1.55 mm to 1.9 mm.

7. The internal combustion engine for low emissions as claimed in claim 1, wherein the plurality of fuel injection holes in the nozzle body ranges from 7 to 9.
8. The internal combustion engine for low emissions as claimed in claim 1, wherein the fuel injection holes within the nozzle body, are configured to deliver fuel at an angle between about 147? to 150? degrees.

9. A method of operating an internal combustion engine comprising the steps of:
rotating a crankshaft of the internal combustion engine in an engine cycle such that a piston 101 coupled with the crankshaft is moved between a bottom dead center position and a top dead center position within a combustion chamber;
injecting a fuel directly into the combustion chamber using a fuel injector such that the fuel is injected after the piston 101 has passed the top dead center position in the engine cycle;
directing fuel injected after the piston has passed the top dead center position to impinge upon the lip portion 107; and
auto igniting a mixture containing the injected fuel and air within the combustion chamber.