DESC:FIELD

The present disclosure relates to combustion chamber for an engine.

BACKGROUND

Recent trends in diesel engine designs are aimed towards obtaining very low compression ratios to meet very stringent NOx (Nitrogen oxide) emission norms. The main advantage of low compression ratio is reduced pumping and frictional losses. However, low compression ratio results in very high CO (Carbon Monoxide) and THC (Total Hydro Carbon) emissions which in turn results in poor combustion efficiency. The main reason for higher CO and THC emissions is the entrapment of more unburned fuel in increased quench zones with reduced compression ratio. The design of combustion chambers of engines plays a vital role in reducing CO and THC emissions and improving low end torque.

In conventional diesel engines, the combustion chamber is re-entrant type with different geometrical shapes, typically having a small cut at the lip zones. To address the drawbacks of low compression ratio in conventional re-entrant combustion chambers for diesel engines and also increase low end torque, there is a need for alternative combustion chamber shapes.

OBJECTS

Some of the objects of the present disclosure aimed to ameliorate one or more problems of the prior art or to at least provide a useful alternative are described herein below:

An object of the disclosure is to provide a combustion chamber for an engine that improves NOx - Soot trade-off and fuel economy.

Another object of the disclosure is to provide a combustion chamber for an engine that reduces CO and THC emissions.

Yet another object of the disclosure is to provide a combustion chamber for an engine that improves low end torque.

Still another object of the disclosure is to provide a combustion chamber for an engine that improves combustion efficiency of engines having low compression ratio.

An additional object of the disclosure is to provide a combustion chamber for an engine that improves engine performance.

Yet another object of the disclosure is to provide a combustion chamber for an engine that can be implemented in any internal combustion engine.

Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.

SUMMARY

A combustion chamber system for an engine is disclosed in accordance with an embodiment of the present disclosure. The combustion chamber system includes a main combustion chamber and an auxiliary combustion chamber. The main combustion chamber is defined by a cavity recessed on an operative top face of a piston crown of a piston that traverses within the cylinder of the engine, inside surface of cylinder wall and a cylinder head. The main combustion chamber receives fuel to be combusted from an injector disposed on the cylinder head. The auxiliary combustion chamber is defined by an auxiliary cavity extending radially outward from and in fluid communication with the cavity, wherein the auxiliary cavity creates vortices and directs fuel flow received therein towards a center of the cylinder, thereby diverting the fuel flow away from wall quench zones and fuel entrapping crevices of the cylinder wall to prevent incomplete combustion of fuel caused by quenching and entrapment of fuel at the cylinder wall.

Typically, the auxiliary combustion chamber has a depth less than the main combustion chamber.

Generally, the main combustion chamber and the auxiliary combustion chamber are connected by a passageway that defines a minimum depth position from top face of the piston crown.

Typically, the engine is a low compression ratio engine.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

The combustion chamber of the present disclosure will now be described with the help of accompanying drawings, in which:

FIGURE 1 illustrates a schematic diagram depicting different conventional combustion chamber shapes;

FIGURE 2 illustrates a combustion chamber including a mini combustion chamber and a main combustion chamber, in accordance with the present disclosure;

FIGURES 3a, 3b and 3c illustrate different shapes of the mini combustion chamber and the direction of flow fields in accordance with the present disclosure;

FIGURE 4 illustrates geometrical notations of the combustion chamber in accordance with the present disclosure;

FIGURES 5a, 5b and 5c illustrate the mini combustion chamber with flow direction diverted towards the center of the chamber;

FIGURES 6a, 6b illustrate simulation results indicating air-fuel mixture distribution in the combustion chamber in accordance with the present disclosure and conventional combustion chamber respectively; and

FIGURES 7a and 7b illustrate exploded view of simulation results indicating air-fuel mixture distribution in the combustion chamber in accordance with the present disclosure and conventional combustion chamber respectively.

DETAILED DESCRIPTION OF ACCOMPANYING DRAWINGS

Low compression ratio diesel engines provide lower NOx emissions. However, due to low temperature combustion higher CO and THC emissions are observed which directly have an impact on engine performance and other emission species such as soot, CO and THC emissions as well as fuel economy. In order to overcome the above drawbacks with low compression ratio, the present disclosure envisages a combustion chamber incorporating a mini combustion chamber and a main combustion chamber for improving the in-cylinder combustion efficiency, performance and emissions by diverting the fuel to the center of the combustion chamber from near wall quench zone and crevices. The combustion chamber as envisaged diverts the flow direction from near wall to centre of the chamber where the in-cylinder temperatures are generally close to 1500 K and best combustion efficiency is possible. To improve the combustion efficiency, mini combustion chamber is introduced adjacent to and in fluid communication with a main combustion chamber, such a configuration of the combustion chamber creates secondary vortices and directs the fuel away from quench zones and crevices, thereby prevents incomplete combustion of the fuel inducted into the combustion chamber and increases the combustion efficiency. The combustion chamber in accordance with the present disclosure also improves low end torque.

In conventional diesel engines, the combustion chamber is a regular re-entrant type as illustrated in FIGURE 1 with different geometrical shapes generally referenced as a, b, c and d. In the prior art patent references EP1630380A1, US5868112, US6705273, US6945210, US6997158, US7210448, US7918206 and US20120234285, the combustion chamber geometries involved a small cut at the lip zone.

A preferred embodiment will now be described in detail with reference to the accompanying drawings. The preferred embodiment does not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments 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.

The combustion chamber system 100 of the present disclosure is now explained with reference to Figures 1 through 7 wherein key features are generally referenced as illustrated. The combustion chamber of the present disclosure incorporates an auxiliary combustion chamber also referred to as mini combustion chamber (101) in association with the main combustion chamber (102) as illustrated in FIGURE 2. The main combustion chamber (102) is defined by a main cavity C1 recessed on an operative top face of a piston crown (50) of a piston traversing within a cylinder of the engine, inside surface of cylinder wall and a cylinder head. The main combustion chamber (102) receives fuel to be combusted from an injector disposed on the cylinder head. The auxiliary combustion chamber (101) also referred to as the mini combustion chamber (101) is defined by an auxiliary cavity C2 extending radially outward from and in fluid communication with the main cavity C1, wherein the auxiliary cavity C2 creates vortices and directs fuel flow received therein towards a center of the cylinder, thereby diverting the fuel flow away from wall quench zones and fuel entrapping crevices of the cylinder wall to prevent incomplete combustion of fuel caused by quenching and entrapment of fuel at the cylinder wall. The main objective of the mini combustion chamber is to create an additional vertices and divert the flow which is moving towards the piston liner to the centre of the chamber. Thereby, that the amount of fuel trapped in the quench zones and crevices will be reduced extensively. The quantity of fuel shifted towards centre of the chamber depends on the geometrical shape of the mini combustion chamber.

FIGURES 3a, 3b and 3c illustrate different shapes of the mini combustion chamber and the direction of flow fields in accordance with the present disclosure. The direction of the flow decides the vortex intensity and percentage shift in flow direction.

FIGURE 4 illustrates geometrical notations of the combustion chamber in accordance with the present disclosure. The critical design region (401) decides the structural stability of the bowl. Volume of the mini combustion chamber (402) and flow entry angle (403) are designed to be optimum along with the exit shape of the mini combustion chamber. This decides the amount of flow accommodated in the mini combustion chamber and intensity of the vortices. FIGURES 5a, 5b and 5c illustrate the mini combustion chamber with flow direction diverted towards the center of the chamber.

The benefits and physics of the air-fuel mixture direction in the mini combustion chamber is purely a function of various non-limiting parameters which influence the in-cylinder flow and are listed herein below:
Vb : Volume of the Primary Combustion Chamber
Va : Volume of the Secondary Combustion Chamber
H1 : Depth of Primary Combustion Chamber
H2 : Depth of Secondary Combustion Chamber
h : Minimum Depth Position from Piston Face
D1 : Maximum Diameter of Primary Combustion Chamber
D2 : Maximum Diameter of Secondary Bowl from Center of the Piston
W : Width of the Secondary Combustion Chamber ((D2-D1)/2)
?1 : In-cylinder Flow out Direction Angle
?2 : In-cylinder Flow in Direction Angle

FIGURES 6a, 6b illustrate simulation results indicating air-fuel mixture distribution in the combustion chamber in accordance with the present disclosure and conventional combustion chamber respectively, referring to Figure 6a, it is clear that concentration of fuel is more towards the center of the chamber than near the near wall of the cylinder; and FIGURES 7a and 7b illustrate another view of simulation results indicating air-fuel mixture distribution in the combustion chamber in accordance with the present disclosure and conventional combustion chamber respectively. These simulation results clearly indicate the significant role played by the combustion chamber of the present disclosure in reducing fuel near the cylinder wall.

The combustion chamber of the present disclosure that can be implemented in any Internal Combustion (IC) engine including a low compression ratio diesel engine is characterized by the features listed herein below.

• The mini combustion chambers can be implemented in any diesel and gasoline direct engines in any field of operation.
• FIGURES 3a, 3b and 3c illustrate the design of air-fuel mixture exit from three different mini combustion chamber designs in accordance with the present disclosure.
• A mini combustion chamber volume to main combustion chamber volume ratio.
• Main and Mini combustion chamber depth ratios.
• Geometrical dimension of ?2, ?1 and h.

TECHNICAL ADVANCEMENTS AND ECONOMICAL SIGNIFICANCE

The technical advancements offered by the present disclosure include the realization of:

• a combustion chamber for an engine that improves NOx - Soot trade-off and fuel economy;

• a combustion chamber for an engine that reduces CO and THC emissions;

• a combustion chamber for an engine that improves low end torque;

• a combustion chamber for an engine that improves combustion efficiency of engines having low compression ratio;

• a combustion chamber for an engine that improves engine performance; and

• a combustion chamber for an engine that can be implemented in any internal combustion engine.

The mini combustion chamber improves the combustion efficiency when multiple injections strategy is used so that fuel economy (FE) improvement is possible.

For Low compression Ratio (LCR) engines, the mini combustion chamber creates an additional vortices and diverts the flow and minimizes the fuel near wall quench zones or crevices. By avoiding the air-fuel mixture stagnation near wall quench zones or crevices, it minimizes the oil dilution and reduces CO, THC and soot emissions. Reduced THC, CO and soot emissions, in effect results in increased low end torque.

The combustion chamber of the present disclosure can be implemented in all types of IC engines and mainly provides added advantage to Diesel engines/Gasoline Direct Engines deployed in the areas of automotive engines, Generator Engines and Tractor Engines.

The numerical values given of various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher or lower than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the disclosure unless there is a statement in the specification to the contrary.

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 preferred 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. ,CLAIMS:1. A combustion chamber system for an engine, said combustion chamber system comprising:

• a main combustion chamber defined by a cavity recessed on an operative top face of a piston crown of a piston adapted to traverse within the cylinder of engine, inside surface of the cylinder wall and a cylinder head, said main combustion chamber adapted to receive fuel to be combusted from an injector disposed on said cylinder head;

• an auxiliary combustion chamber defined by an auxiliary cavity extending radially outward from and in fluid communication with said cavity, wherein said auxiliary cavity is adapted to create vortices and direct fuel flow received therein towards a center of said cylinder, thereby diverting said fuel flow away from wall quench zones and fuel entrapping crevices of said cylinder wall to prevent incomplete combustion of fuel caused by quenching and entrapment of fuel at the cylinder wall.

2. The combustion chamber system as claimed in claim 1, wherein said auxiliary combustion chamber has a depth less than said main combustion chamber.

3. The combustion chamber system as claimed in claim 1, wherein said main combustion chamber and said auxiliary combustion chamber are connected by a passageway that defines a minimum depth position from top face of said piston crown.

4. The combustion chamber system as claimed in claim 1, wherein said engine is a low compression ratio engine.