SYSTEM AND METHOD FOR PRODUCING HOMOGENEOUS FUEL CHARGE IN AN INTERNAL COMBUSTION DIESEL ENGINE
FIELD OF INVENTION:
The present invention relates to internal combustion diesel engine. More particularly, the present invention relates to a system and method for producing homogeneous fuel charge for HCCI mode of the internal combustion diesel engine such that both NOx and soot emissions are reduced substantially.
BACKGROUND OF THE INVENTION:
It is well known in the art that diesel engines have highest thermal efficiency among currently available engines and are, therefore, widely used. However, one of the major disadvantages associated with the diesel engines is that such engines usually emit more particulate matter and NOx than their gasoline counterparts. Another major disadvantage associated with the diesel engines occurs due to trade-off between NOx and soot emissions. It is usually impossible to reduce both kinds of emissions simultaneously as the factors that tend to decrease one usually increase the other.
Attention to environment has lead the government bodies to prescribe strict emission standards to the engine manufacturers. In order to achieve the prescribed emission standards, engine manufacturers are constantly trying to devise new and improved systems and methods that reduce the NOx and soot emissions. Further, the engine manufacturers are also trying to devise methods and system which reduce the NOx and soot emissions simultaneously

One such method is operating the internal combustion engine in homogenous charge compression ignition (HCCI) combustion mode at part load conditions. HCCI combustion mode is an alternative mode for internal combustion engine in which the fuel is homogeneously mixed with air and is auto-ignited by compression. Due to charge homogeneity, this mode is characterized by low equivalence ratios and temperatures giving simultaneously low NOx and soot in diesel engines. The conventional problem of NOx-soot trade-off is avoided in this mode due to absence of diffusion combustion. To avoid knocking, this mode can be employed at part load conditions while maintaining conventional combustion at high load thus minimizing regulatory cycle emissions and reducing cost of after-treatment systems.
Prior arts disclose various methods for achieving a homogenous charge for the HCCI combustion mode. One of the methods used is multiple fuel injections in the cylinder of the internal combustion engine. Such a method has been useful in reducing the NOx and soot emissions simultaneously if the ratio of fuel mass injected in each injection is carefully decided along with the injection timing to create adequate pre-mixing of the charge. If proper pre-mixing of the charge does not happen, it would lead to a NOx-soot trade off like conventional compression ignition (CI) combustion. However, such method achieves only about 20 % NOx and soot reduction over the conventional compression ignition (CI) mode.
Accordingly, there is a need for an improved system and method for producing homogeneous fuel charge in the internal combustion engine for substantially and simultaneously reducing NOx and soot emissions.
OBJECTS OF THE INVENTION:
One object of the present invention is to provide a system and method that reduces the NOx and soot emissions simultaneously.

Another object of the present invention is to provide a system and method that reduces soot emissions in the range of about 20 to 50% over the conventional compression ignition (CI) mode.
Yet another object of the present invention is to provide a system and method that reduces NOx in the range of about 20 to 50% over the conventional compression ignition mode.
Yet another objective of the present invention is to provide a system and method which is simple, cost effective and reliable.
These and other objects as well as advantages will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.
SUMMARY OF THE INVENTION:
In accordance with the purposes of the invention, the present invention as embodied and broadly described herein, provides a method for producing homogeneous fuel charge in an internal combustion engine for reducing NOx and soot emissions simultaneously. In one embodiment, the method comprises injecting a first quantity of fuel in the cylinder of the internal combustion engine. The first quantity of fuel is injected multiple times in pre-determined ratios at pre-determined injection timings. Thereafter, the method comprises recirculating a pre-determined quantity of exhaust gas discharged from the exhaust system of the internal combustion engine to the intake system of the internal combustion engine. The recirculation of the pre-determined quantity of exhaust gas is via a recirculation system. The method further comprises injecting a second quantity of fuel into the pre¬determined quantity of exhaust gas at one or more pre-determined locations in the recirculation system.

The present invention further discloses a system for producing homogeneous fuel charge in an internal combustion engine for reducing NOx and soot emissions simultaneously. In one embodiment, the system comprises atleast one first injection means, atleast one second injection means and a recirculation system. The first injection means is configured for injecting a first quantity of fuel in the cylinder of the internal combustion engine. The first quantity of fuel is injected multiple times in pre-determined ratios at pre-determined injection timings. The recirculation system is configured for recirculating a pre-determined quantity of exhaust gas discharged from the exhaust system of the internal combustion engine to the intake system of the internal combustion engine. The second injection means is configured for injecting a second quantity of fuel into the pre-determined quantity of exhaust gas. The second quantity of fuel is injected at one or more pre-determined locations in the recirculation system.
These and other aspects as well as advantages will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.
BRIEF DESCRIPTION OF DRAWINGS
To further clarify advantages and aspects of the invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings, which are listed below for quick reference.
Figure 1 illustrates a method for producing homogeneous fuel charge in an internal combustion diesel engine for reducing NOx and soot emissions simultaneously, in accordance with the one or more embodiments of the present invention.

Figure 2 illustrates a system for producing homogeneous fuel charge in an internal combustion diesel engine for reducing NOx and soot emissions simultaneously, in accordance with one or more embodiments of the present invention.
Figure 3 illustrates a schematic layout showing the construction and working of the second injection means for producing homogeneous fuel charge in the internal combustion engine for reducing NOx and soot emissions simultaneously, in accordance with the one or more embodiments of the present invention.
Figure 4 illustrates an example of first injection method, in accordance with one or more embodiments of the present invention.
The person ordinary skill in the art will appreciate that elements in the drawings are illustrated for simplicity and may not have been necessarily drawn to scale. For example, the dimensions of some of the elements in the drawings may be exaggerated relative to other elements to help to improve understanding of aspects of the invention. Furthermore, the one or more elements may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.
DETAILED DESCRIPTION
It should be understood at the outset that although illustrative implementations of the embodiments of the present disclosure are illustrated below, the present invention may be implemented using any number of techniques, whether currently known or in existence. The present disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, including the exemplary design and

implementation illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents.
The term "some" as used herein is defined as "none, or one, or more than one, or all ." Accordingly, the terms "none," "one," "more than one," "more than one, but not all" or "all" would all fall under the definition of "some." The term "some embodiments" may refer to no embodiments or to one embodiment or to several embodiments or to all embodiments. Accordingly, the term "some embodiments" is defined as meaning "no embodiment, or one embodiment, or more than one embodiment, or all embodiments."
The terminology and structure employed herein is for describing, teaching and illuminating some embodiments and their specific features and elements and does not limit, restrict or reduce the spirit and scope of the claims or their equivalents.
More specifically, any terms used herein such as but not limited to "includes," "comprises," "has," "consists," and grammatical variants thereof do NOT specify an exact limitation or restriction and certainly do NOT exclude the possible addition of one or more features or elements, unless otherwise stated, and furthermore must NOT be taken to exclude the possible removal of one or more of the listed features and elements, unless otherwise stated with the limiting language "MUST comprise" or "NEEDS TO include."
Whether or not a certain feature or element was limited to being used only once, either way it may still be referred to as "one or more features" or "one or more elements" or "at least one feature" or "at least one element." Furthermore, the use of the terms "one or more" or "at least one" feature or element do NOT preclude there being none of that feature or element, unless otherwise specified by limiting language such as "there NEEDS to be one or more ..." or "one or more element is REQUIRED."

Unless otherwise defined, all terms, and especially any technical and/or scientific terms, used herein may be taken to have the same meaning as commonly understood by one having an ordinary skill in the art.
Reference is made herein to some "embodiments." It should be understood that an embodiment is an example of a possible implementation of any features and/or elements presented in the attached claims. Some embodiments have been described for the purpose of illuminating one or more of the potential ways in which the specific features and/or elements of the attached claims fulfill the requirements of uniqueness, utility and non-obviousness.
Use of the phrases and/or terms such as but not limited to "a first embodiment," "a further embodiment," "an alternate embodiment," "one embodiment," "an embodiment," "multiple embodiments," "some embodiments," "other embodiments," "further embodiment", "furthermore embodiment", "additional embodiment" or variants thereof do NOT necessarily refer to the same embodiments. Unless otherwise specified, one or more particular features and/or elements described in connection with one or more embodiments may be found in one embodiment, or may be found in more than one embodiment, or may be found in all embodiments, or may be found in no embodiments. Although one or more features and/or elements may be described herein in the context of only a single embodiment, or alternatively in the context of more than one embodiment, or further alternatively in the context of all embodiments, the features and/or elements may instead be provided separately or in any appropriate combination or not at all. Conversely, any features and/or elements described in the context of separate embodiments may alternatively be realized as existing together in the context of a single embodiment.
Any particular and all details set forth herein are used in the context of some embodiments and therefore should NOT be necessarily taken as limiting factors to the attached claims. The attached claims and their legal equivalents can be realized in the

context of embodiments other than the ones used as illustrative examples in the description below.
Figure 1 illustrates a method 100 for producing homogeneous fuel charge in an internal combustion engine for reducing NOx and soot emissions simultaneously, in accordance with the one or more embodiments of the present invention.
For the purposes of the invention, said method is employed during the HCCI mode for the internal combustion diesel engine. In other words, this method can be employed at part load conditions while maintaining conventional combustion at high load.
At step 101, the method comprises injecting a first quantity of fuel in the cylinder of the internal combustion diesel engine, said first quantity of fuel being injected multiple times in pre-determined ratios at pre-determined injection timings. In one embodiment, the first quantity of fuel is injected in the pre-determined ratio of x: y: z, wherein x is in a range of 37-43%, y is in a range of 42-48%, and z is in a range of 12-16%. The pre-determined ratio x of the first quantity of fuel is injected at the pre-determined injection timing in the range of 45° to 55° CA bTDC. The pre-determined ratio y of the first quantity of fuel is injected at the pre-determined injection timing in the range of 0° to 5° CA bTDC. The pre-determined ratio z of the first quantity of fuel is injected at the pre-determined injection timing in the range of 15 to 20° CA aTDC. In this operating condition, the exhaust gas is continuously re-circulated to the intake system in the pre-determined quantity.
At step 102, the method comprises recirculating a pre-determined quantity of exhaust gas discharged from an exhaust system of the internal combustion engine to an intake system of the internal combustion engine via an exhaust gas recirculation system. In one embodiment, the pre-determined quantity of exhaust gas discharged from the exhaust system of the internal combustion chamber is in the range of 20-48% of total exhaust gas.

At step 103, the method comprises injecting a second quantity of fuel into the pre-determined quantity of exhaust gas, said second quantity of fuel being injected at one or more pre-determined locations in the exhaust gas recirculation system. In one embodiment, the pre-determined location is a location proximate to and upstream of the intake system of the internal combustion engine. The advantage of injecting second quantity of fuel at such a location is that it completely evaporates due to high exhaust gas temperature and mixes uniformly with the intake air. In another embodiment, the pre-determined location is a location in the recirculation system where the temperature of the exhaust gas is in a range of 100 to 300 °C. It is to be understood that the recirculation system may have a plurality of such locations and the second quantity of fuel may be injected at one or more of these locations in pre-determined ratios. Due to high temperature of exhaust gas i.e. 100 to 300 °C at such locations, the second quantity of fuel evaporates faster and enhances mixing with the intake air resulting in homogenous charge formation.
Figure 2 illustrates a system 200 for producing homogeneous fuel charge in an internal combustion engine for reducing NOx and soot emissions simultaneously, in accordance with an embodiment of the present invention.
The system comprises atleast one first injection means 201, atleast one second injection means 202 and a recirculation system 203. The first injection means 201 is configured for injecting a first quantity of fuel in the cylinder 204 of the internal combustion diesel engine 205. The first injection mean(s) 201 is operably connected to cylinder 204 of the internal combustion engine 205 to inject a first quantity of fuel. In one example, the first injection means may be a common rail direct injection method.
In one embodiment, the first quantity of fuel is injected in the pre-determined ratio of x: y: z, wherein x is in a range of 37-43%, y is in a range of 42-48%, and z is in a range of 12-16%. The pre-determined ratio x of the first quantity of fuel is injected at the pre-determined injection timing in the range of 45° to 55° CA bTDC. The pre-determined ratio y of the first quantity of fuel is injected at the pre-determined injection timing in the range

of 0° to 5° CA bTDC. The pre-determined ratio z of the first quantity of fuel is injected at the pre-determined injection timing in the range of 15 to 20° CA aTDC.
The recirculation system 203 is configured to recirculate a pre-determined quantity of exhaust gas discharged from an exhaust system 207 to an intake system 206 of the internal combustion engine 205. The recirculation system 203 comprises atleast one recirculation pipe and a control unit. The recirculation pipe acts as a passage for the flow of the recirculated exhaust gas. The control unit is configured to calculate and direct the pre-determined quantity of gas in the recirculation pipe. The remaining quantity of exhaust gas is disposed by means already known in the art.
As shown in the Figure, "x" quantity of exhaust gas is discharged from the exhaust system of the internal combustion engine out of which "y" quantity is recirculated to the intake system of the internal combustion engine. It is to be understood that the value of x is always greater than the value of y. In one embodiment, the pre-determined quantity of exhaust gas discharged from the exhaust system of the internal combustion engine is in the range of 20-48% of total exhaust gas.
In one embodiment, one end of the recirculation pipe is connected to the outlet of an Exhaust Gas Recirculation (EGR) cooler and the other end of recirculation pipe is connected to the intake system of the internal combustion engine. The EGR cooler is used to lower the temperature of the discharged exhaust gas. It is to be noted that the construction, function and the location of the EGR cooler is the same as known to a person skilled in the art.
The second injection mean(s) 202 is configured for injecting a second quantity of fuel at one or more pre-determined locations in the recirculation system 203. The second injection mean(s) 202 include a fuel injection pump that receives fuel from a fuel tank and air at a pre-determined pressure. The fuel injection pump is communicatively coupled to a control unit which in turn is communicatively coupled to the control unit of the internal

combustion engine. The fuel injection pump is coupled to a fuel injector. Based on engine parameters received from the control unit of the internal combustion engine, the control unit of the second injection means direct a second quantity of fuel to be injected, via a fuel injector, at one or more pre-determined locations in the recirculation system.
In one embodiment, the pre-determined location is a location proximate to and upstream of the intake system of the internal combustion engine. The advantage of injecting second quantity of fuel at such a location is that due to high exhaust temperature the fuel evaporates and mixes with the intake air to form a homogeneous charge. In another embodiment, the pre-determined location is a location in the recirculation system where the temperature of the exhaust gas is in a range of 100 to 300 °C. It is to be understood that the recirculation system may have a plurality of such locations and the second quantity of fuel may be injected at one or more of such locations. Due to high temperature of exhaust gas i.e. 100 to 300 °C at such locations, the second quantity of fuel evaporates faster and enhances mixing with the intake air resulting in homogenous charge formation. In one embodiment, the second quantity of fuel in injected at multiple locations by a plurality of second injection means.
Figure 3 illustrates a schematic layout 300 showing the construction and working of the second injection means for producing homogeneous fuel charge in the internal combustion engine, in accordance with the one or more embodiments of the present invention.
The layout comprises an internal combustion engine 301 coupled with an eddy current dynamometer 302. In one embodiment, the internal combustion engine 301 is a 4 cylinder, heavy duty, turbocharged, common rail engine. The layout comprises further components known to a person skilled in the art such as intercooler 303 with air inlet 315 and outlet 316 and water inlet 317 and outlet 318, air filters 304, exhaust back pressure control valves 305, turbocharger 306 and the likes.

The layout further comprises an EGR cooler 307 for lowering the temperature of the exhaust gas discharged by the exhaust gas system 308 of the internal combustion engine 301. One end of the recirculation pipe 309 is connected to the outlet of the EGR cooler and another end of the recirculation pipe is connected to the intake system 310 of the internal combustion engine. The exhaust gas from the exhaust gas system 308 of the internal combustion engine 301 is received in the EGR cooler 307. Thereafter, a pre-determined quantity of exhaust gas is recirculated into the intake system 310 of the internal combustion engine 301.
The second injection means 311 is highlighted with dashed lines. As shown, the second injection means 311 includes a fuel tank 312, a fuel injection pump 313, a fuel injector and atleast one control unit 314. The fuel injection pump 313 is coupled to the fuel tank 312 and the fuel injector. The fuel injection pump 313 is further coupled to means that provide pressurized air. The control unit 314 is communicatively coupled to the control unit of the internal combustion engine via means known in the art such as, being not limited to, CAN network. Based on data received from the control unit of the internal combustion engine, the control unit 314 of the second injection means controls the operation and interaction of the above-mentioned components of the second injection means and injects a second quantity of fuel at one or more pre-determined locations (highlighted by ' 1' and/or '2' in Figure 3) in the recirculation system 309. The boundary box (shown by dash dot line) serves as an interface between the engine and the control units.
Two control units are used to control the entire set-up. The first control unit is used to control the first injection means and the second control unit is used to control the in-cylinder injection into the internal combustion engine. The pressurized shop air is supplied at 8 bar to the fuel injection pump. The Pulse Width Modulated (PWM) type of pump is controlled by the ECU. The air-assisted injector is a simple nozzle with no mechanical and electrical parts. The minimum Sauter Mean Diameter (SMD) that this injector can provide is around 15-(im. In one example, this injector is based on a twin-fluid atomizer concept with external air-assisted mixing. The energy for atomization is mainly provided by the air

pressure. The contact between air and liquid happens only after the liquid injection takes place.
As shown in the diagram, the second quantity of fuel is injected at a location upstream of the intake system 310 of the internal combustion engine 301 and is represented by reference symbol '1'. Also shown is an alternate location in the recirculation system denoted by reference symbol '2', where the temperature of the exhaust gas is in the range of 100-300 °C. It is to be understood that locations T and '2' are only for the purpose of illustration and should not in any way be construed as limiting. There may be other locations upstream and proximate to the intake system where the second quantity of fuel may be injected. Also, there may be other locations in the recirculation system where the temperature of the exhaust gas is in the range of 100-300 °C.
Figure 4 illustrates an example of first injection method, in accordance with one or more embodiments of the present invention.
As stated earlier, in one example, the first injection means is a common rail direct injection system. Such an injection system includes a fuel pump 401, a fuel accumulator
402 called as the common rail and an injector 403 per cylinder 404 all of which are
controlled by an electronic control unit 405. The system further comprises fuel filtration
system and reservoir 406, a fuel supply line 407 and a leak off fuel return line 408.
As indicated in the Figure, the fuel filtration system and reservoir 406 supplies fuel to the fuel pump 401 via fuel supply line 407. The fuel from fuel pump is supplied to common rail 402. The fuel pump is driven by means 409 already known in the art such as gear drive. The fuel from the common rail is thereafter supplied to one or more injectors
403 via common rail 402 under pre-determined conditions of pressure. Such pre-determined
conditions are already known to a person skilled in the art. In case of fuel leak off from the
common rail and the injectors, the fuel reaches back to the reservoir 406 via leak fuel return
line 408.

Table 1 illustrates results of the experiments performed by the disclosed method and system with 20% EGR rate. Conventional CI mode comprises of only in-cylinder injections and 100% of the fuel is injected into the cylinder in a pre-determined ratio but not necessarily resulting in the reduction of NOx and soot simultaneously. EDI mode is Early Direct Injection and it also comprises of only in-cylinder injection which we call as first injection in this art. In EDI mode, 100% of the fuel is injected in the cylinder itself in a pre¬determined ratio which is optimized for simultaneous reduction of NOx and soot emissions. AAI is Air-assisted Injection which is the second injection mentioned in this art. EDI+AAI mode is the combination of first and second injections. In this mode, 90% of the total fuel injection is carried out by means of first injection (EDI) and 10% of the total fuel injection is carried out by means of second injection (AAI) simultaneously. As shown in Table 1, EDI mode results in simultaneous reduction of both NOx and soot. NOx has reduced by 20.7% and soot by 16.7% over conventional CI mode. In EDI+AAI mode, nearly 24.1% NOx reduction over Conventional CI mode was achieved. However, there was an increase in soot emission due to insufficient evaporation of fuel in intake.

It was necessary to carry out the second injection in hotter exhaust stream in-order to completely evaporate the fuel and form homogeneous charge to reduce soot emissions. Hence, it was decided to increase the EGR rate of the conventional combustion mode and carry out first and second injections with it in-order to assess reduction in soot emissions by EDI and EDI+AAI modes.
Table 2 illustrates results of the experiments performed by the disclosed method and system with 48% EGR rate. In the EDI+AAI mode, 85% of the total fuel injection is carried out by means of first injection (EDI) and 15% of the total fuel injection is carried out by means of second injection (AAI) simultaneously. As shown in Table 2, since higher EGR rate is used, the NOx is very low in all the three modes. Soot reduction of 75% over conventional CI mode was achieved. The results with 48% EGR rate show that there is a good potential for soot reduction due to complete evaporation of fuel which helps to form a homogeneous charge.

While certain present preferred embodiments of the invention have been illustrated and described herein, it is to be understood that the invention is not limited thereto. Clearly, the invention may be otherwise variously embodied, and practiced within the scope of the following claims.

WE CLAIM:
1. A method for producing homogeneous fuel charge in an internal combustion diesel
engine for reducing NOx and soot emissions simultaneously, said method comprising:
- injecting a first quantity of fuel in a cylinder of the internal combustion engine, said
first quantity of fuel being injected multiple times in pre-determined ratios at pre-determined injection timings;
- recirculating a pre-determined quantity of exhaust gas discharged from an exhaust
system of the internal combustion engine to an intake system of the internal
combustion engine via an exhaust gas recirculation system; and
- injecting a second quantity of fuel into the pre-determined quantity of exhaust gas,
said second quantity of fuel being injected at one or more pre-determined locations in the recirculation system.
2. The method as claimed in claim 1, wherein the pre-determined locations include:
- a location proximate to and upstream of the intake system of the internal combustion engine; and
- a location in the exhaust gas recirculation system where the temperature of the exhaust gas is in a range of 100 to 300°C.

3. The method as claimed in claim 1, wherein the first quantity of fuel and the second quantity of fuel are injected in a pre-determined ratio of a:b respectively, wherein 'a' is in the range of 6-15% and 'b' is in the range of 85-94%.
4. The method as claimed in claim 1, wherein the first quantity of fuel is injected in the pre-determined ratio of x: y: z, wherein x is in a range of 37-43%, y is in a range of 42 to 48%, and z is in a range of 12 to 16%.
5. The method as claimed in claim 5, wherein the pre-determined ratio x of the first quantity of fuel is injected at the pre-determined injection timing in the range of 45 to 55° CA bTDC, the pre-determined ratio y of the first quantity of fuel is injected at the

pre-determined injection timing in the range of 0° to 5° CA bTDC and the pre-determined ratio z of the first quantity of fuel is injected at the pre-determined injection timing in the range of 15 to 20° CA aTDC.
6. The method as claimed in claim 1, wherein pre-determined quantity of exhaust gas discharged from the exhaust system of the internal combustion chamber is in the range of 20-48% of total exhaust gas.
7. A system for producing homogeneous fuel charge in an internal combustion diesel engine for reducing NOx and soot emissions simultaneously, said system comprising:
- atleast one first injection means configured for injecting a first quantity of fuel in the
cylinder of the internal combustion engine, said first quantity of fuel being injected multiple times in pre-determined ratios at pre-determined injection timings;
- a recirculation system configured for recirculating a pre-determined quantity of
exhaust gas discharged from the exhaust system of the internal combustion engine to the intake system of the internal combustion engine; and
- atleast one second injection means configured for injecting a second quantity of fuel
into the pre-determined quantity of exhaust gas, said second quantity of fuel being injected at one or more pre-determined locations in the recirculation system.
8. The system as claimed in claim 7, wherein recirculation system includes an exhaust gas recirculation (EGR) cooler.
9. The system as claimed in claim 7, wherein the pre-determined locations include:
- a location proximate to and upstream of the intake system of the internal
combustion engine; and
- a location in the exhaust gas recirculation system where the temperature of the
exhaust gas is in a range of 100 to 300 °C.